Vol. 90 - No. 10 - October 2016

Journal of
Geodesy
The
Geodesist’s
Handbook
2016

A constituent Association of theInternational Union of Geodesy andGeophysics (IUGG)
Edited by:
IAG Office
Hermann Drewes
Deutsches Geodätisches Forschungsinstitut
der Technischen Universität München (DGFI-TUM)
Arcisstraße 21
D-80333 München, Germany
Phone: +49-89-23 031 1215, Fax +49-89-23 031 1240
E-mail: iag.office@tum.deFranz Kuglitsch
Helmholtz Centre Potsdam
GFZ German Research Centre for Geosciences
Telegrafenberg, A17
D-14473 Potsdam, Germany
Phone: +49-331-288 1978, Fax: +49-331-288 1759
E-Mail: fgkugl@gfz-potsdam.de
IAG Communication and Outreach Branch (COB)
József Ádám, Szabolcs Rózsa
Department of Geodesy and Surveying
Budapest University of Technology and Economics
P.O.Box 91
H-1521 Budapest, Hungary
Phone: +36-1-463 3222/3213, Fax +36-1-463 3192
e-mail: jadam@sci.fgt.bme.hu, szrozsa@iag-aig.org

J Geod (2016) 90:907–1205
DOI 10.1007/s00190-016-0948-z© 2016 The Author(s)This article is published with open access at Springerlink.com

THE GEODESIST’S HANDBOOK 2016
Table of Contents

Foreword …………………………………………………………………………………………………………

911

The International Association of Geodesy (IAG)
Historical Overview ……………………………………………………………………………………………..
Statutes of the International Association of Geodesy …………………………………………………………...
Bylaws of the International Association of Geodesy ……………………………………………………………
Rules for IAG Scientific Meetings ………………………………………………………………………………
Rules for the IAG Levallois Medal ……………………………………………………………………………...
Rules for the IAG Guy Bomford Prize …………………………………………………………………………..
Rules for the IAG Young Authors Award ……………………………………………………………………….
Rules for IAG Travel Awards ……………………………………………………………………………………
IAG Fund ………………………………………………………………………………………………………...
IAG Membership Application Form …………………………………………………………………………….

913
921
925
937
939
940
941
942
943
944

The XXVI IUGG General Assembly
IAG Presidential Address ……………………………………………………………………………………..…
IAG Levallois Medal Laudation …………………………………………………………………………………
IAG Guy Bomford Prize Lecture ………………………………………………………………………………..
IAG Young Authors Award Citation ……………………………………………………………………………
Report of the IAG Secretary General ……………………………………………………………………………
Minutes of the IAG Council Sessions …………………………………………………………………………...
Summary of the IAG Executive Committee Sessions ………………………………………………………...…
IUGG Resolutions ……………………………………………………………………………………………….
IAG Resolutions …………………………………………………………………………………………………

945
953
955
957
959
965
971
977
981

Structures for the Period 2015 – 2019
International Union of Geodesy and Geophysics (IUGG) ……………………………………………………... 983
International Association of Geodesy (IAG) …………………………………………………………………… 985
Commission 1 – Reference Frames …………………………………………………………………………….. 987
Commission 2 – Gravity Field ………………………………………………………………………………….. 1007
Commission 3 – Earth Rotation and Geodynamics …………………………………………………………….. 1027
Commission 4 – Positioning and Applications …………………………………………………………………. 1039
Inter-commission Committee on Theory ……………………………………………………………………….. 1059
Communication and Outreach Branch (COB) ………………………………………………………………….. 1077

Contents

910

Global Geodetic Observing System (GGOS)
GGOS Terms of Reference and Structure 2015-2019 ………………………………………………………….. 1079
Inventory of Standards and Conventions ……………………………………………………………………….. 1095

IAG Scientific Services
International Bureau on Weights and Measures – Bureau International des Poids et Mesures (BIPM)- Time Department …………………………………………………………………..…………………………. 1157
International Earth Rotation and Reference Systems Service (IERS) ………………………………………….. 1160
International DORIS Service (IDS) …………………………………………………………………………….. 1162
International GPS Service (IGS) ………………………………………………………………………………... 1167
International Laser Range Service (ILRS) ……………………………………………………………………… 1170
International VLBI Service for Geodesy and Astrometry (IVS) ……………………………………………….. 1173
International Gravity Field Service (IGFS) …………………………………………………………………….. 1175
International Centre for Global Earth Models (ICGEM) …………………………………………………..…… 1177
International Digital Elevation Models Service (IDEMS) ……………………………………………………… 1181
International Geodynamics and Earth Tide Service (IGETS) …………………………………………………... 1183
International Gravimetric Bureau – Bureau Gravimetrique International (BGI) ……………………………….. 1186
International Service for the Geoid (ISG) ………………………………………………………………………. 1191
Permanent Service for Mean Sea Level (PSMSL) ……………………………………………………………… 1193

General Information
IAG on the Internet ……………………………………………………………………………………………… 1195
IAG Publications ………………………………………………………………………………………………... 1197
IAG Delegates of IUGG Member Countries .…………………………………………………………………… 1199
IAG Representatives to Services, IUGG, and External Scientific Bodies ……………………………………… 1205

Foreword

911

Foreword
Hermann Drewes1 ∙ Franz Kuglitsch2 ∙ József Adám3 ∙ Szabolcs Rózsa3

The Geodesist’s Handbook is published by theInternational Association of Geodesy (IAG) periodicallyafter each IUGG/IAG General Assembly. The objective isto present the current IAG structure and its specifications,and to introduce the terms of reference and the officers of
the Association’s components for the upcoming legislative
period to the broad geodetic community. The scientificprogram and planned activities are described in detail.
The first part of the Handbook 2016 presents thehistorical developments and current regulations of the IAG(Statutes, Bylaws and Rules as reviewed during theIUGG/IAG General Assembly 2015).
The second part summarises the outcome of the IAG
General Assembly held in conjunction with the 26th IUGG
General Assembly in Prague, Czech Republic, in June/July
2015. An overview of the most important IAG results from2011 to 2015 is given in the presidential address. The
citations of the scientists decorated in Prague with thehighest IAG awards (Levallois Medal, Guy Bomford Prize,
and Young Authors Award) are published. Reports of theSecretary General, the IAG Council and Executive
Committee meetings, and the IUGG and IAG resolutions
conclude this section.

The third part of the Handbook contains the detailed
structures and programs for the period 2015-2019. All IAG
components (Commissions, Inter-commission Committee,
Communication and Outreach Branch, Services, and the
Global Geodetic Observing System) are presented alongwith their sub-components (Sub-commissions, Projects,
Study Groups and Working Groups). This part describes
the planed scientific work of IAG during the coming years.
The fourth part completes the Handbook with some
general information useful for the geodetic community.
The IAG Internet representation and the publication series
are highlighted, and the IAG national delegates andrepresentatives to services and international scientificbodies are listed.
We thank the contributors to the Geodesist’s Handbook
2016. These are in particular all the IAG officers listed in
the structures, but also the uncounted secretaries andtechnicians in the institutions affiliated with IAG or one ofits components and sub-components. The engaged andauthentic cooperation in geodesy is one of the mosteffective means for the great success of our science. We
hope that this collaboration will be continued or evenextended in the current period 2015-2019.

_□ Hermann Drewes, IAG Secretary General
iag.office@tum.de
1

Deutsches Geodätisches Forschungsinstitut, Technische Universität
München (DGFI-TUM), Arcisstr.21, 80333 München, Germany

2

Helmholtz Centre Potsdam, GFZ German Research Centre forGeosciences, Telegrafenberg, A17, 14473 Potsdam, Germany

3

Department of Geodesy and Surveying, Budapest University ofTechnology and Economics, P.O. Box 91, 1521 Budapest, Hungary

912

The Geodesist’s Handbook 2016

List of previous Geodesist’s Handbooks

1980: Bulletin Géodesique, Vol. 54, No. 3, http://link.springer.com/journal/190/54/3/page/1
1984: Bulletin Géodesique, Vol. 58, No. 3, http://link.springer.com/journal/190/58/3/page/1
1988: Bulletin Géodesique, Vol. 62, No. 3, http://link.springer.com/journal/190/62/3/page/1
1992: Bulletin Géodesique, Vol. 66, No. 2, http://link.springer.com/journal/190/66/2/page/1
1996: Journal of Geodesy, Vol. 70, No. 12, http://link.springer.com/journal/190/70/12/page/1
2000: Journal of Geodesy, Vol. 74, No. 1, http://link.springer.com/journal/190/74/1/page/1
2004: Journal of Geodesy, Vol. 77, No. 10-11, http://link.springer.com/journal/190/77/10/page/1
2008: Journal of Geodesy, Vol. 82, No. 11, http://link.springer.com/journal/190/82/11/page/1 (open access)2012: Journal of Geodesy, Vol. 86, No. 10, http://link.springer.com/journal/190/86/10/page/1 (open access)Historical Overview

913

The International Association of Geodesy
Historical Overview
H. Drewes1 ∙ J. Adám2

The history of the International Association of Geodesy
goes back to April 1862 when the Central European Arc
Measurement (“Mitteleuropäische Gradmessung”) was
initiated at a “preliminary consultation” of representativesof the states of Prussia, Austria and Saxony in Berlin. At
the end of the year, 16 countries had joined the project.
The first General Conference was held in Berlin, October
1864, with delegates from 14 countries. In 1867 it was
expanded to the European Arc Measurement and in 1886
to the International Geodetic Association (“Internationale

Erdmessung”, “Association Géodésique Internationale”).
At the Constitutive Assembly of the International ResearchCouncil (IRC) in Brussels, July 1919, the “Section
Geodesy” was one of the constituents of the International
Union of Geodesy and Geophysics (IUGG) and held its
Constitutive Assembly during the first IUGG General
Assembly in Rome, April-May 1922. The name waschanged to “Association of Geodesy” in Stockholm,
August 1930, and to the present name in July 1946. The
following summarises the historic development.

Table 1 General Conferences / General Assemblies of the International Association of Geodesy and predecessors
No

Venue

Year

I. General Conferences
Ia. Mitteleuropäische Gradmessung - Central European
Arc Measurement (1862-1867)

No
Venue
Year
Ic. Internationale Erdmessung - Association GéodésiqueInternationale – Int. Geodetic Association (1886-1922)
9

Paris, France

1889

1

Berlin, Prussia

1864

10

Brussels, Belgium

1892

2

Berlin, Prussia

1867

11

Berlin, German Empire

1895

12

Stuttgart, German Empire

1898

Ib. Europäische Gradmessung - European Arc
Measurement (1867-1886)

13

Paris, France

1900

3

Vienna, Austria-Hungary

1871

14

Copenhagen, Denmark

1903

4

Dresden, German Empire

1874

5

Stuttgart, German Empire

1877

15

Budapest, Austria-Hungary

1906

16

Cambridge, United Kingdom

1909

6

Munich, German Empire

1880

17

Hamburg, German Empire

1912

7

Rome, Italy

1883

8

Berlin, German Empire

1886

II. General Assemblies of the Section and Associationof Geodesy at the General Assemblies of the IUGG
IIa. IUGG Section of Geodesy (1919-1930)□ Hermann Drewes
iag.office@tum.de
1

Deutsches Geodätisches Forschungsinstitut der Technischen Univ.
München (DGFI-TUM), Arcisstr. 21, 80333 München, Germany
2
Department of Geodesy and Surveying, Budapest University ofTechnology and Economics, P.O. Box 91, 1521 Budapest, Hungary

18Rome, Italy (Constitutive Assembly)

1922

19

Madrid, Spain

1924

20

Prague, Czechoslovakia

1927

21

Stockholm, Sweden

1930

H. Drewes, J. Adám

914

Table 1 continued
No

Venue

Participants:

IUGG

IAG

Year

IIb. IUGG Association of Geodesy (1930-1946)

No

Venue

IUGG

IAG

Year

32

Moscow, USSR

Participants:

2577

449

1971

22

Lisbon, Portugal

200

1933

33

Grenoble, France

2564

398

1975

23

Edinburgh, UK

344

1936

34

Canberra, Australia

1944

278

1979

24

Washington, USA

805

1939

35

Hamburg, F.R. Germany

3204

472

1983

IIc. IUGG International Association of Geodesy (1946-…)

36

Vancouver, Canada

3939

420

1987

25

Oslo, Norway

368

1948

37

Vienna, Austria

4331

594

1991

26

Brussels, Belgium

918

1951

38

Boulder, USA

4481

567

1995

27

Rome, Italy

923

1954

39

Birmingham, UK

4052

478

1999

28

Toronto, Canada

1165

1957

40

Sapporo, Japan

4151

407

2003

29

Helsinki, Finland

1375

1960

41

Perugia, Italy

4351

433

2007

30

Berkeley, USA

1938

1963

42

Melbourne, Australia

3392

370

2011

31

Zurich/Lucerne,
Switzerland

2200

1967

43

Prague, Czech Republic

4231

534

2015

44

Montreal, Canada

357

2019

Table 2 Scientific Assemblies of the International Association of Geodesy
No

Venue

Date

Number of Attendees

1

Tokyo, JapanMay 7-15,1982

200

2

Edinburgh, UK

August 3-12,1989

355

3

Beijing, China

August 8-13,1993

340

4

Rio de Janeiro, Brazil

September 3-9,1997

250

5Budapest, Hungary

September 2-7, 2001

461

6

Cairns, Australia

August 22-26, 2005 (joint with IAPSO and IABO)

7

Buenos Aires, Argentina

August 31- Sept. 4, 2009

363

8

Potsdam, Germany

September 1-6, 2013

538

9

Kobe, Japan

July 30 – August 4, 2017 (joint with IASPEI)

IAG: 145 (in all: 724)

Table 3 Presidents of the International Association of Geodesy and predecessors
No

PeriodPosition

Name

Residence

Ia. Mitteleuropäische Gradmessung (1862-1867), Europ. Gradmessung (European Arc Measurement) (1867-1886)1

1864-1868

President of the Permanent Commission

Peter Andreas Hansen

Gotha, Thuringia

2

1869-1874

President of the Permanent Commission

August von Fligely

Vienna, Austria-Hungary

31874-1886

President of the Permanent Commission

Carlos Ibañez de Ibero

Madrid, Spain

Ib. Internat. Erdmessung - Association Géodésique Internationale (International Geodetic Association) (1886-1917)
3

1887-1891

President of the Association

Carlos Ibañez de Ibero

Madrid, Spain

4

1892-1902

President of the Association

Hervé A. E. A. Faye

Paris, France

5

1903-1917

President of the Association

Léon J. A. Bassot

Paris, France

Ic. Reduced Geodetic Association among Neutral States (1917-1922)6

1917-1922

President of the Reduced Association

Raul Gautier

Geneva, Switzerland

Historical Overview

915

Table 3 continued
No

PeriodPosition

Name

Residence

IIa. IUGG Section of Geodesy (1919-1930)7

1922-1933

President of the Section

William Bowie

Washington, USA

Felix A. Vening-Meinesz

Amersfoort, The Netherlands

IIb. IUGG Association of Geodesy (1930-1946)8

1933-1946

President of the AssociationIIc. International Association of Geodesy (IAG) of the IUGG (1946-…)
9

1946-1951

President of the IAG

Walter D. Lambert

Washington, USA

10

1951-1954

President of the IAG

Carl F. Bäschlin

Zurich, Switzerland11

1954-1957

President of the IAG

James de Graaf Hunter

London, United Kingdom

12

1957-1960

President of the IAG

Gino Cassinis

Milan, Italy13

1960-1963

President of the IAG

Charles A. Whitten

Washington, USA

14

1963-1967

President of the IAG

Guy Bomford

London, United Kingdom

15

1967-1971

President of the IAG

Antonio Marussi

Trieste, Italy

16

1971-1975

President of the IAG

Youri D. Boulanger

Moscow, USSR

17

1975-1979

President of the IAG

Tauno J. Kukkamäki

Helsinki, Finland18

1979-1983

President of the IAG

Helmut Moritz

Graz, Austria

19

1983-1987

President of the IAG

Peter V. Angus-Leppan

Kensington, Australia

20

1987-1991

President of the IAG

Ivan I. Mueller

Columbus, USA21

1991-1995

President of the IAG

Wolfgang Torge

Hannover, Germany

22

1995-1999

President of the IAG

Klaus-Peter Schwarz

Calgary, Canada

23

1999-2003

President of the IAG

Fernandó Sansó

Milan, Italy24

2003-2007

President of the IAG

Gerhard Beutler

Bern, Switzerland

25

2007-2011

President of the IAG

Michael G. Sideris

Calgary, Canada

26

2011-2015

President of the IAG

Chris Rizos

Sydney, Australia

27

2015-2019

President of the IAG

Harald Schuh

Potsdam, Germany

Table 4 Permanent Secretaries / Secretaries General of the International Association of Geodesy and predecessors
No

PeriodPosition

Name

Residence

Ia. Internationale Erdmessung - Association Géodésique Internationale (International Geodetic Association) (1886-1917)
and Reduced Geodetic Association among Neutral States (1917-1922)1

1886-1900

Permanent Secretary

Adolf Hirsch

Neuchatel, Switzerland2

1900-1921

Permanent Secretary

H. G. van de Sande-Bakhuysen

Leiden, The Netherlands

Ib. IUGG Section of Geodesy (1919-1930) and IUGG Association of Geodesy (1930-1946)3

1922-1946

Secretary General

Georges Perrier

Paris, France

Ic. International Association of Geodesy of the IUGG (1946-…)
4

1946-1960

Secretary General

Pierre Tardi

Paris, France

5

1960-1975

Secretary General

Jean-Jacques Levallois

Paris, France

6

1975-1991

Secretary General

Michel Louis

Paris, France

7

1991-1995

Secretary General

Claude Boucher

Paris, France

8

1995-2007

Secretary General

Carl Christian Tscherning

Copenhagen, Denmark

92007-2019

Secretary General

Hermann Drewes

Munich, Germany

H. Drewes, J. Adám

916

Table 5 Central Bureau (since 2007 Office) of the International Association of Geodesy and predecessors
No

PeriodHost InstituteName of Director

Residence

1
2
31864 – 1885
1886 – 1917
1917 – 1922

Royal Prussian Geodetic InstituteJohann Jacob Baeyer
Friedrich Robert Helmert
J. H. Louis Krüger (p.p.)

Potsdam, Prussia
Potsdam, Germany
Potsdam, Germany

4
5
6
7
8

1922 – 1946
1946 – 1960
1960 – 1975
1975 – 1991
1991 – 1995

Institut Géographique National (IGN)

Georges Perrier
Pierre Tardi
Jean-Jacques Levallois
Michel LouisClaude Boucher

Paris, France
Paris, France
Paris, France
Paris, France
Paris, France

91995 – 2007

Niels Bohr Institute, Department ofGeophysics, University of Copenhagen

Carl Christian Tscherning

Copenhagen, Denmark

102007 –

Deutsches Geodätisches Forschungsinstitut

Hermann Drewes

Munich, Germany

Table 6 Editors in Chief of Official Journals of the International Association of Geodesy and predecessors
No
I.1

JournalName of Editor-in-Chief

Residence

1922 – 1945

Georges Perrier

Paris, France

I.2

1946 – 1951

Pierre Tardi

Paris, France

I.3

1952 – 1964

Jean-Jacques Levallois

Paris, France

I.4

1965 – 1975

Michel Louis

Paris, France

I.5

1975 – 1986

Ivan I. Mueller

Columbus, USA

I.6

1987 – 1995

Carl Christian Tscherning

Copenhagen, Denmark

1976 – 1980

Ivan I. Mueller

Columbus, USA

II.2

1980 – 1982

Peter Meissl

Graz, Austria

II.3

1982 – 1988

Erwin Groten

Darmstadt, F.R. Germany

II.4

1989 – 1991

Clyde C. Goad
Erik W. Grafarend

Columbus, USA
Stuttgart, Germany

II.5

1991 – 1995

Petr Vaniček

New Brunswick, Canada

1995 – 2003

Peter J. G. Teunissen

Delft, The Netherlands

III.2

2003 – 2007

William E. Featherstone

Perth, Australia

III.3

2007 – 2015

Roland Klees

Delft, The Netherlands

III:42015 – 2019

Jürgen Kusche

Bonn, Germany

II.1

III.1

Bulletin Géodésique

PeriodManuscripta Geodaetica

Journal of Geodesy

Table 7 Editors of the International Association of Geodesy Symposia Series
No

Period1

1991-1995

Wolfgang Torge

Name of Editor

Hannover, Germany

Residence

Name of Assistant Editor

Residence2

1995-1999

Klaus-Peter Schwarz

Calgary, Canada

3

1999-2003

Fernandó Sansó

Milan, Italy4

2003-2007

Gerhard Beutler

Bern, Switzerland

5

2007-2011

Michael G. Sideris

Calgary, Canada

6

2011-2015

Chris Rizos

Sydney, Australia

Pascal Willis

Paris, France

7

2015-2019

Jeff Freymueller

Fairbanks, USA

Laura Sánchez

Munich, Germany

Historical Overview

917

Table 8 Editors of The Geodesist’s Handbook
No

Year

EditorResidence

1

1980

Ivan I. Mueller

Columbus, USA

2

1984

Carl Christian Tscherning

Copenhagen, Denmark

3

1988

Carl Christian Tscherning

Copenhagen, Denmark

4

1992

Carl Christian Tscherning

Copenhagen, Denmark

5

1996

Pascal Willis

Paris, France

6

2000

Ole B. Andersen

Copenhagen, Denmark

7

2004

Ole B. Andersen

Copenhagen, Denmark

8

2008

H. Drewes, H. Hornik / J. Ádám, Sz. Rózsa

Munich, Germany / Budapest, Hungary

9

2012

H. Drewes, H. Hornik / J. Ádám, Sz. Rózsa

Munich, Germany / Budapest, Hungary

10

2016

H. Drewes, F. Kuglitsch / J. Ádám, Sz. Rózsa

Munich & Potsdam, Germany / Budapest, Hungary

Table 9 Guy Bomford Prize Awardees of the IAG

Table 10 Levallois Medal Awardees of the IAG

No

Residence

No

Year

Name of Awardee

Year

Name of Awardee

Residence

11975 Erik Grafarend

Munich, F.R.Germany

1

1979 Charles Whitten

Washington, USA

2

1979 Fernandó Sansó

Milan, Italy

2

1983 Rudolf Sigl

Munich, F.R.Germany

3

1983 John Wahr

Boulder, USA

3

1987 Arne Bjerhammar

Stockholm, Sweden

4

1987 Peter J. Teunissen

Delft, The Netherlands

41991 Paul Melchior

Brussels, Belgium

51991 Shuhei Okubo

Tokyo, Japan5

1995 Willem Baarda

Delft, The Netherlands

61995 Thomas Herring

Cambridge, USA

61999 Torben Krarup

Copenhagen, Denmark

71999 Véronique Dehant

Brussels, Belgium

72003 George Veis

Athens, Greece

82003 Ramon Hanssen

Delft, The Netherlands

8

Copenhagen, Denmark

92007 Masato Furuya

Tokyo, Japan

2007 Carl Christian
Tscherning

102011 Johannes Böhm

Vienna, Austria

92011 Ruth E. Neilan

Pasadena, USA

112015 Yoshiyuki Tanaka

Tokyo, Japan

10

2015 Reiner Rummel

Munich, Germany

Table 11 IAG Best Young Author Awardees
No

Year

Author’s NameCountry

Title of the Publication

1 1993 Hussein A. AbdElmotaal

Egypt

Vening-Meinesz Moho depths: traditional, exact and approximated.
Manuscripta Geodaetica, 18: 171-181

2 1994 Jean-Pierre Barriot

FranceLine of sight operators in planetary geodesy. Manuscripta Geodaetica,
19: 269-283

3 1995 Srinivas V. Bettadpur

India

Hotine’s geopotential formulation revisited. Bull. Géod., 69: 135-142.

4 1996 Giovanna Sona

Italy

Numerical problems in the computation of ellipsoidal harmonics.
Journal of Geodesy, 70: 117-126.

5 1998 Cheinway Hwang

TaiwanInverse Vening-Meinesz formula and deflection-geoid formula:applications to the predictions of gravity and geoid over the South China
Sea. Journal of Geodesy, 72: 304-312.

6 1999 Peiliang Xu

China

Biases and accuracy of, and an alternative to, discrete nonlinear filters.
Journal of Geodesy, 73: 35-46.

7 2000 Christopher Kotsakis

CanadaThe multiresolution character of collocation. J. of Geodesy, 74: 275-290

H. Drewes, J. Adám

918

Table 11 continued
No Year

Author’s nameCountry

Title of the Publication

8 2000 Rüdiger Lehmann

Germany

Altimetry-gravimetry problems with free vertical datum. Journal of
Geodesy, 74: 327-334.

9 2001 Susan Skone

CanadaThe impact of magnetic storms on GPS receiver performance. Journal of
Geodesy, 75: 457-468.

10 2003 Michael Kern

Germany

A study on the combination of satellite, airborne and terrestrial gravity
data (with K.-P. Schwarz and N. Sneeuw). J. of Geodesy, 77: 217-225.

11 2004 Shfaqat Abbas
Khan

Pakistan

Shallow water loading tides in Japan from superconducting gravity (with
J.L. Hoyer). Journal of Geodesy, 78: 245-250.

12 2005 Roland Pail

Austria

A parametric study on the impact of satellite attitude errors on GOCE
gravity field recovery. Journal of Geodesy, 79: 231-241.

13 2006 Steffen Schön

Germany

Uncertainty in GPS networks due to remaining systematic errors: theinternal approach (with H. Kutterer). Journal of Geodesy, 80: 150-162.

14 2008 Franziska WildPfeiffer

Germany

A comparison of different mass elements for use in gravity gradiometry.
Journal of Geodesy, 82: 637-653.

15 2010 Elizabeth PetriUK

A first look at the effects of ionospheric signal bending on a globallyprocessed GPS network. Journal of Geodesy, 84: 491-499.

16 2011 Thomas Artz

Germany

Assessment of periodic sub-diurnal Earth rotation variations at tidal
frequencies through VLBI normal equations. J of Geodesy, 85, 565-584.

17 2012 Manuela Seitz

Germany

The 2008 DGFI realization of the ITRS: DTRF2008. Journal of
Geodesy, 86: 1097-1123.

18 2013 Krzysztof Sośnica

Switzerland Impact of loading displacements on SLR-derived parameters and on theconsistency between GNSS and SLR results. J of Geodesy, 87: 751-769.

19 2014 Alvaro Santamaría
Gómez

FranceLong-term vertical land motion from double-differenced tide gauge andsatellite altimetry data. Journal of Geodesy, 88: 207-222.

Table 12 IAG Services
No

Acronym

Name of the IAG Service (and Address of the Homepage)

Year of
Formation

1 BGI

Bureau Gravimetrique International / http://bgi.omp.obs-mip.fr

1951

2 BIPM

Bureau International des Poids et Measures – Time Department / http://www.bipm.org

1875

3 ICGEMInternational Centre for Global Earth Models / http://icgem.gfz-potsdam.de/ICGEM

2003

4 IDEMS

International Digital Elevation Models Service / http://TBD

1999

5 IDS

International DORIS Service / http://ids.cls.fr

2003

6 IERSInternational Earth Rotation and Reference Systems Service / http://www.iers.org

1987

7 IGETSInternational Geodynamics and Earth Tide Service / http://igets.u-strasbg.fr/

2015

8 IGFSInternational Gravity Field Service / http://www.igfs.net

2004

9 IGS

International GNSS Service / http://igscb.jpl.nasa.gov

1994

10 ILRSInternational Laser Ranging Service / http://ilrs.gsfc.nasa.gov

1998

11 ISGInternational Service for the Geoid / http://www.iges.polimi.it

1991

12 IVSInternational VLBI Service for Geodesy and Astrometry / http://ivscc.gsfc.nasa.gov

1999

13 PSMSL

Permanent Service for Mean Sea Level / http://www.psmsl.org/

1933

Historical Overview

919

Table 12 continued: Historical IAG Services
BIH
ICET
ILS
IPMS

Bureau International de l’Heure(1987 integrated into IERS)
International Center for Earth Tides (2015 integrated into IGETS)
International Latitude Service(1962 International Polar Motion Service, IPMS)
International Polar Motion Service (Successor of ILS, 1987 integrated into IERS)

1912
1956
1899
1962

Table 13 Fellows of the IAG
1991:
D.A. Adebekun, Nigeria
D.-E. Ajakaiye, USA
V. Ashkenazi, UK
W. Augath, Germany
T.F. Baker, UK
G. Balmino, France
L.W. Baran, Poland
G. Birardi, Italy
A. Bjerhammar, Sweden
D. Blitzkow, Brazil
Y. Bock, USA
G. Boedecker, Germany
J.D. Bossler, USA
C. Boucher, France
P. Brosche, Germany
F.K. Brunner, Austria
M. Burša, Czech Republic
J. Campbell, Germany
G. Carrera, Canada
M. Charfi, Tunisia
J. Y. Chen, China
B. H. Chovitz, USA
O. Coker, Nigeria
O. L. Colombo, USA
A. Comolet-Tirman, France
A.H. Cook, UK
P.A. Cross, UK
K. I. Daugherty, USA
P. de Jonge, USA
A. Dermanis, Greece
J.O. Dickey, USA
A.H. Dodson, UK
B.C. Douglas, USA
A. Drozyner, Poland
H. Dufour, France
D. Eckhardt, USA

O. Fadahunsi, Nigeria
F. Fajemirokun, Nigeria
M. Feissel-Vernier, France
I. Fejes, Hungary
I.K. Fischer, USA
R. Forsberg, Denmark
P. Forsyth, Canada
D. Fritsch, Germany
J. Gaignebet, France
E.M. Gaposchkin, USA
C. Gemael, Brazil
C.C. Goad, USA
E.W. Grafarend, Germany
E. Groten, Germany
E. Gubler, Switzerland
B. Guinot, France
B. Heck, Germany
G. Hein, Germany
H. Henneberg, Venezuela
S. Henriksen, USA
P. Holota, Czech Republic
L. Hora, Czech Republic
H.T. Hsu, China
J.R. Huddle, USA
C. Jekeli, USA
G. Jentzsch, Germany
I. Joó, Hungary
C.S. Joshi, India
H.-G. Kahle, Switzerland
H.P. Kahmen, Austria
J. Kakkuri, Finland
K. Kasahara, Japan
E. Kausel, Chile
H. Kautzleben, Germany
A.H.W. Kearsley, Australia
R.W. King, USA
A. Kiviniemi, Finland

R. Klees, The Netherlands
K.R. Koch, Germany
B. Kolaczek, Poland
K. Konan, Ivory Coast
J. Kovalevsky, France
Y. Kozai, Japan
J. Krynski, Poland
M. Kumar, USA
J.T. Kuo, USA
M.P.M. Lefebvre, France
D. Lelgemann, Germany
G.W. Lennon, Australia
G. Lensen, New ZealandJ-J. Levallois, France
E. Livieratos, Greece
M. Louis, France
G.R. Mader, USA
J. Makris, Germany
A. Mancini, USA
I. Marson, Italy
M. McNutt, USA
D.D. McCarthy, USA
W.G. Melbourne, USA
P. Melchior, Belgium
C. Morelli, Italy
H. Moritz, Austria
I.I. Mueller, USA
I. Nakagawa, Japan
A. Nobili, Italy
J.D. Obel, Kenya
M.Odlanicki-Poczobut,
PolandB.P. Pertsev, Russia
K. Poder, Denmark
C. Poitevin, Belgium
M.T. Prilepin, Russia
J. Rais, Indonesia

R.H. Rapp, USA
C. Reigber, Germany
A.R. Robbins, UK
R.S. Rostom, Kenya
R. Rummel, Germany
F. Sacerdote, Italy
F. Sansó, Italy
N.K. Saxena, USA
B. Schaffrin, USA
G. Schmitt, Germany
B.E. Schutz, USA
K.-P. Schwarz, Canada
G. Seeber, Germany
M.J. Sevilla, Spain
P.J. Shelus, USA
M.G. Sideris, Canada
L.E. Sjöberg, Sweden
R.A. Snay, USA
H. Sünkel, Austria
T. Tanaka, Japan
P. Teunissen, The Netherlands
W. Torge, Germany
C.C. Tscherning, Denmark
P. Vaniček, Canada
C. Veillet, France
P. Vyskočil, Czech Republic
A. Waalewijn, The Netherlands
J. Wahr, USA
D.E. Wells, Canada
W.M. Welsch, Germany
L.A. White, Australia
P. Wilson, Germany
P.L. Woodworth, UK
Y.Y. Yatskiv, Ukraine
K. Yokoyama, Japan
D.B. Zilkoski, USA
J.D. Zund, USA

1995:
J. Ádám, Hungary
R. Barzaghi, Italy
M. Becker, Germany
G. Beutler, Switzerland
W. Bosch, Germany
B.F. Chao, USA
H. Denker, Germany
J. Dow, Germany

G.K. Elgered, Sweden
B. Engen, Norway
A. Geiger, Switzerland
T. Kato, Japan
A. Kleusberg, Germany
J. Kouba, Canada
H. Landau, Germany
R.B. Langley, Canada
K. Linkwitz, Germany

S. Molodensky, Russia
R. Neilan, USA
C. Noll, USA
S. Okubo, Japan
P. Pâquet, Belgium
J.C. Ries, USA
J.M. Rüeger, Australia
E.J.O. Schrama, The
Netherlands

C.-K. Shum, USA
T.A. Spoelstra, The
Netherlands
S. Takemoto, Japan
C. Thomas, France
J.A. Weightman, UK
P. Willis, France
C. Wilson, USA
T. Yunck, USA

H. Drewes, J. Adám

920

Table 13 continued
1999:
N. Andersen, Denmark
O. Andersen, Denmark
D. Arabelos, Greece
M.G. Arur, India
L. Ballani, Germany
G.B. Benciolini, Italy
M.G. Bevis, USA

G. Blewitt, UK
J.M. Bosworth, USA
A. Cazenave, France
T.A. Clark, USA
J. Degnan, USA
V. Dehant, Belgium
H. Drewes, Germany
B. Ducarme, Belgium

W. Featherstone, Australia
W. Freeden, Germany
T. Herring, USA
K.-H. Ilk, Germany
J. Johanssen, Sweden
P. Knudsen, Denmark
Z.-X. Li, China
J. Manning, Australia

N. Pavlis, USA
C. Rizos, Australia
C. Rocken, USA
I.N. Tziavos, Greece
M. Vermeer, Finland
M. Wei, Canada
D. Wolf, Germany
S. Zerbini, Italy

2003:
E.F. Arias, Argentina
J.-P. Barriot, France
P.A. Berry, UK
C.A. Brunini, Argentina
C. Bruyninx, Belgium
D. Gambis, France
G. Gendt, Germany
R.S. Gross, USA

W. Gurtner, Switzerland
S. Han, Australia
R. Hanssen, The Netherlands
B.G. Harsson, Norway
C. Hwang, Taiwan
W. Keller, Germany
S.C. Kenyon, USA
R. Kursinski, USA
H. Kutterer, Germany

R. Lehman, Germany
A. Marchenko, Ukraine
R. Scharroo, The Netherlands
W. Schlüter, Germany
T. Schöne, Germany
S. Skone, Canada
N. Sneeuw, Canada
M. Stewart, Australia
G. Strykowski, Denmark

C. Tiberius, The Netherlands
H. van der Marel, The
Netherlands
N. Vandenberg, USA
P. Visser, The Netherlands
L. Vitushkin, France
J. Vondrak, Czech Republic
R. Weber, Austria
Y. Yuanxi, China

2007:
Z. Altamimi, France
R. Biancale, France
M. Craymer, Canada
D. Crossley, USA
R. Dietrich, Germany
X. Ding, Hong Kong
L.P.S. Fortes, Brazil
Y. Gao, Hong Kong
D. Grejner-Brzezinska, US

K. Heki, JapanL. Hothem, USA
J. Huang, China
J. Ihde, Germany
M. Kuhn, Australia
J. Kusche, The Netherlands
U. Marti, Switzerland
C. Merry, South Africa
A.W. Moore, USA
P. Novák, Czech Republic

M.C. Pacino, Argentina
M.R. Pearlman, USA
H.-P. Plag, USA
M. Poutanen, Finland
B. Richter, Germany
M. Rothacher, Germany
Sz. Rózsa, Hungary
M. Scheinert, Germany
H. Schuh, Austria
H.-P. Sun, China

J.A. Torres, Portugal
Gy. Tóth, Hungary
P. Tregoning, Australia
M. Verroneau, Canada
J. Wang, Australia
R. Wonnacott, South Africa
P. Xu, JapanJ. Yu, China
S.Y. Zhu, Germany

2011:
H. Abd-Elmotaal, Egypt
L. Alfonsi, Italy
D. Behrend, USA
S. Bettadpur, USA
S. Bisnath, Canada
A. Brzezinski, Poland
T. van Dam, Luxembourg
J. Davis, USA
Y. Feng, Australia
J. Freymueller, USA

Y. Fukuda, JapanTh. Hobiger, Japan
H. Hornik, Germany
S. Jin, South Korea
M.O. Karslioglu, Turkey
Ch. Kotsakis, Greece
S. Lambert, France
F. Lemoine, USA
C. Ma, USA
Z. Malkin, Russia
S. Matsuzaka, Japan

Gy. Mentes, Hungary
A. Michlenz, Germany
M. Omura, Japan
R. Pail, Germany
J. Ray, USA
A. Reiterer, Germany
G. Retscher, Austria
L.J. Rickards, UK
D. Roman, USA
L. Sanchez, Germany
M. Santos, Canada

M. Schmidt, Germany
F. Seitz, Germany
L. Soudarin, France
G. Tavernier, France
S. Verhagen, The
Netherlands
Y.M. Wang, USA
J. Wickert, Germany
H. Wilmes, Germany

2015:
D. Angermann, Germany
D. Avalos, Mexico
F. Barthelmes, Germany
O. Baur, Austria
J. Boehm, Austria
J. Bogusz, Poland
S. Bonvalot, France
C. Braitenberg, Italy

J. Chen, USA
R. Cunderlik, Slovakia
X. Deng, Australia
J. Dawson, Australia
A. Eicker, Germany
J. Ferrandiz, Spain
Ch. Gerlach, Germany
M. Hashimoto, Japan
A. Jäggi, Switzerland

G. Johnston, Australia
A. Kealy, Australia
Sh. Abbas Khan, Denmark
M. King, Australia
W. Kosek, Poland
K. Mikula, Slovakia
H. Ozener, Turkey
S. Pagiatakis, Canada
V. Palinkas, Czech Republic

M. Reguzzoni, Italy
S. Rosat, France
M. Thomas, Germany
M. Weigelt, Germany
B. Wouters, UK/USA
Li Zhenhong, UK

IAG Statutes

921

IAG Statutes adopted by the IAG Council
at the XXVI IUGG General Assembly in Prague, Czech Republic, 2015

1. Definition of Terms

2. International Association of Geodesy(a) Geodesy is the discipline that deals with the measurement and representation (geometry, physics, andtemporal variations) of the Earth and other celestialbodies.

(a) The International Association of Geodesy:(b) IUGG means the International Union of Geodesy
and Geophysics.

(b) In the event of the dissolution of the IAG, its assets
shall be ceded to the IUGG.

(c) IAG or Association means the International
Association of Geodesy.
(d) Adhering Body and Council have the same
meaning as in the Statutes of the IUGG.
(e) General Assembly means an assembly for scientific and/or administrative purposes of:(i) scientists from geodesy and other Earth science
disciplines;(ii) the Council delegates (or alternative delegates)
appointed by the Adhering Bodies; and(iii) individual members as defined by Statute 6(b).
(f) Scientific Assembly means an assembly forprimarily scientific purposes and therefore it does
not normally require the presence of the delegatesappointed by the Adhering Bodies.
(g) Council Delegate means the person appointed by
the Adhering Body to be member of the Council
for four years. Adhering Bodies may appoint an
Alternative Delegate to a Council meeting if thePermanent Delegate cannot attend the meeting.
(h) Period means the interval of time between theclosures of two successive ordinary General
Assemblies.

(i) is a constituent Association of the IUGG; and(ii) is subject to the Statutes and Bylaws of the
IUGG.

3. Mission
The Mission of the Association is the advancement ofgeodesy. The IAG implements its mission by
furthering geodetic theory through research andteaching, by collecting, analyzing, modelling andinterpreting observational data, by stimulating technological development and by providing a consistent
representation of the figure, rotation, and gravity fieldof the Earth and planets, and their temporal variations.

4. Objectives
The IAG shall pursue the following objectives toachieve its mission:(a) Study, at the highest possible level of accuracy, allgeodetic problems related to Earth observation andglobal change, including:i) Definition, establishment, and maintenance of
global and regional reference systems forinterdisciplinary use.
ii) Rotation of the Earth and planets.
iii) Positioning and deformation.
iv) Gravity field.
v) Ocean, ice and sea level.
vi) Atmosphere and hydrosphere.
vii)Time and frequency transfer.

The Geodesist’s Handbook 2016922(b) Support the maintenance of geodetic reference
systems and frames for continuous, long-term
observations and archival of results.
(c) Provide observational and processed data,
standards, methodologies, and models in a form
that ensures the broadest possible range of research
and application.
(d) Stimulate development and take advantage of
emerging space and other technologies to increase
the resolution and accuracy of geodetic data andproducts in order to advance geodetic andinterdisciplinary research.
(e) Initiate, coordinate, and promote international
cooperation and knowledge exchange throughsymposia, workshops, summer schools, training
courses, publications, and other means ofcommunication.
(f) Foster the development of geodetic activities andinfrastructure in all regions of the world, taking
into consideration the specific situation of developing countries.
(g) Collaborate with the international science andengineering community in supporting theapplication of geodetic theory and techniques andthe interpretation of results.
(h) Cooperate with national and international agencies
in establishing research goals, missions, andprojects.

5. Structure and Administration(a) The Association's structure shall comprise a small
number of components: Commissions, the Intercommission Committee on Theory (ICCT),
Services, the Global Geodetic Observing System(GGOS), and the Communication and OutreachBranch (COB).
(b) Subcomponents, such as IAG Projects, Sub-commissions, Commission Projects, Inter-commission
Committees, and Study and Working Groups, may
be formed as provided for in the Bylaws.
(c) The administration of the IAG is carried out by theGeneral Assembly, the Council, the Bureau and the
Executive Committee. The COB is the office
responsible for the promotional activities of the
IAG and the communication with its members.

6. Membership
The membership of the IAG shall comprise:(a) Adhering Bodies; and(b) Individual members in accordance with the Bylaws

7. IAG Council(a) The Council is responsible for governance, strategic policy and direction.
(b) The membership of the Council consists of delegates appointed by the Adhering Bodies.
(c) Each Adhering Body may appoint one delegate
subject to the conditions in (d) and (e) below.
(d) A delegate may only represent one Adhering Body.
(e) The President, Vice President and Secretary
General may not serve as delegates.

8. Bureau(a) The Bureau of the Association consists of the President,
the Vice President and the Secretary General.
(b) The duties of the Bureau shall be to administer theaffairs of the Association in accordance with these
Statutes and Bylaws and with the decisions of theCouncil and the Executive Committee.

9. President(a) The President shall be elected by the Council.
(b) The President shall provide general leadership for
the Association.
(c) The President presides over the meetings of theGeneral Assembly, the Scientific Assembly, theCouncil, the Executive Committee, and the Bureau.
The President has no vote in the Council meetings,
except in the case of a tie as provided in 14(h).
(d) The President, on completion of his or her term ofoffice of one period, shall serve for the next period
in the position of Immediate Past President.

10. Vice President(a) The Vice President shall be elected by the Council.
(b) The Vice President shall perform such tasks as may
be assigned by the President, the Executive
Committee or the Council.
(c) The Vice President assumes the functions, duties
and powers of the President when the latter isabsent or otherwise unable to assume office.

IAG Statutes

11. Secretary General(a) The Secretary General shall be elected by theCouncil.
(b) The Secretary General shall serve as secretary of
the General Assembly, the Scientific Assembly, theCouncil, the Executive Committee, and the Bureau
and arrange for meetings of these bodies inaccordance with the Bylaws.

12. Executive Committee(a) The Executive Committee shall consist of thefollowing voting members: the Bureau, the immediate Past President, the Presidents of theCommissions, the President of the ICCT, the Chairof GGOS, the President of the COB, the three
representatives of the Services, and two Membersat-Largetoimprove
geographicalandorganizational balance.
(b) Presidents of the Inter-commission Committees
other than the ICCT, Chairs of the IAG Projects,
and the Assistant Secretaries shall attend any
meeting of the Executive Committee, with voice
but without vote. The Past Presidents and past
Secretaries General may attend any meeting of the
Executive Committee, with voice but without vote,(except for the immediate Past President, who does
have a vote).
(c) The election of Executive Committee members
shall be in accordance with the Bylaws.
(d) The duties of the Executive Committee shall be tofurther the objectives of the Association througheffective coordination and through the formulationof general policies.

13. Council Meetings(a) The Council shall meet at the time of a General
Assembly.
(b) The Council may hold extraordinary meetings
either in person or electronically, at times otherthan a General Assembly. Such meetings must be
proposed by the Executive Committee.
(c) The members of the Executive Committee may
attend meetings of the Council, with voice but
without vote, except for those who are also delegates.

14. Voting in Council
Voting in Council shall follow the following rules:

923(a) An Adhering Body which is not represented at a
Council meeting may vote by correspondence on
any specific question, provided that the matter has
been clearly defined on the final agenda distributed
in advance, and that the discussion thereon has notproduced any significant new considerations orchange in its substance, and that the said vote has
been received by the President prior to the voting.
(b) Quorum in Council meetings is achieved when thenumber of Council Delegates in attendance is atleast one third of the delegates from countries
eligible to vote.
(c) On questions not involving matters of finance, eachdelegate from an Adhering Body, with its IUGG
subscriptions paid up to the end of the calendar
year preceding the voting, shall have one vote.
(d) On questions involving finance, each delegate froman Adhering Body, which has paid its IUGG subscriptions up to the end of the calendar year preceding the voting, shall have the right to vote. The
number of votes allotted to each delegate of an
Adhering Body shall then be equal to the numberof its category of membership, as defined by
IUGG.
(e) Before a vote in a Council meeting, the President
shall decide whether or not the matter under consideration is financial in character and whether theprocedure of voting by correspondence applies.
(f) The Council may also deliberate and decidematters at other times by correspondence and/or
email ballot, provided that the issues werecommunicated to Council members at least one
month in advance of the voting date.
(g) Decisions of the Council shall be taken by a simple
majority, except as otherwise specified in these
Statutes. If a tie should occur in a Council vote, thePresident shall cast the decisive vote. This
procedure also applies if the vote is taken by mailballot. Simple and two-thirds majorities are
determined by the proportion of affirmative votes
to the sum of all votes (affirmative, negative andabstention). Blank and invalid ballots and votes notcast by delegates present are counted as abstentions.
(h) Except as otherwise provided in the Statutes or
Bylaws, meetings of the Council, as well as thoseof other IAG administrative bodies, shall be conducted according to the edition of Robert's Rules ofOrder currently recommended by the IUGG.

The Geodesist’s Handbook 2016

924

15. Decision of Council(a) Decisions of the Council shall be reported to theindividual membership in a meeting of the IAG
General Assembly.
(b) If the majority of those present at this meeting disagree with the decisions of the Council, theCouncil shall reconsider the question, and make adecision, which shall be final.

16. Changes to Statutes and Bylaws
Changes in the Statutes and Bylaws shall be made as
follows:(a) If deemed necessary, the Association may review
the Statutes and Bylaws in each period, to ensure an
up-to-date structure of its scientific andadministrative organization. A Review Committee
will be appointed by the Executive Committee toachieve this goal. Proposals for a change of any
article of these Statutes and Bylaws must reach theSecretary General at least two months before theannounced date of the Council meeting at which it
is to be considered. The Secretary General shallnotify all Adhering Bodies of any proposed change
at least one month before the announced date of theCouncil meeting.
(b) The Statutes may not be modified except by theapproval of a two-thirds majority of votes cast at a
Council meeting, and shall come into force at theclose of that meeting.
(c) The Council shall have the power to adopt Bylaws
within the framework of the Statutes.
(d) The Bylaws may be modified by a simple majorityof votes cast at a Council meeting, and shall comeinto force at the close of the meeting.

IAG Bylaws

925

IAG Bylaws adopted by the IAG Council
at the XXVI IUGG General Assembly in Prague, Czech Republic, 2015

1. Definition of Terms(a) Association components or components means
Commissions, the Inter-commission Committee on
Theory (ICCT), Services, the Global Geodetic
Observing System (GGOS), and the Communication and Outreach Branch (COB).
(b) Commissions represent major fields of activity inaccordance with the IAG statutes.
(c) Services collect and analyze observations to generate products relevant to geodesy and othersciences and applications.
(d) The Global Geodetic Observing System (GGOS)
works with the IAG Services to provide thegeodetic expertise and infrastructure necessary forthe monitoring of the Earth system and globalchange research.
(e) Association subcomponents or subcomponents
are long-term or short-term structures created by
IAG or one or more of its components.
(f) Long-term subcomponents comprise IAG Projects (broad in scope and of high interest for theentire field of geodesy), Inter-commission Committees, Sub-commissions and Commission Projects which may remain established for several periods.
(g) Short-term subcomponents means Study Groups
and Working Groups which are established for a
maximum term of one period.
(h) Steering Committee means a group of elected or
appointed IAG officers who review the work ofCommissions, Inter-commission Committees (see17), IAG Projects (see 16), and the Communication
and Outreach Branch (see 18).

(i) Period means the interval of time between theclosures of two successive IAG General Assemblies.

2. Responsibilities of Association Components(a) The scientific work of the Association is performedby Commissions, Inter-commission Committees,
IAG Projects, Services and the GGOS.
(b) The responsibilities of the Association components
are determined by the Council on the recommendation of the Executive Committee.
(c) Components shall interact with each other where
their activities are inter-related.
(d) Each component may set up subcomponents and is
responsible for the activities of those subcomponents.

3. General Responsibilities of Component Presidents or Chairs, and Steering Committees(a) Each component shall have a President or Chair
who will lead a Steering Committee.
(b) The component President or Chair is responsible
for the scientific development within the component's field of interest. The component President or
Chair shall:(i) coordinate the work of the subcomponents;(ii) keep the officers of the component as well as
the Bureau informed of the component's
activities, on an annual basis;(iii) collect reports of the subcomponents twomonths before each IAG General andScientific Assembly for publication in the"Travaux de l'Association Internationale deGéodésie";

The Geodesist’s Handbook 2016

926

(iv) receive suggestions for new subcomponents,and suggestions for continuation of existingones; and(v) recommend changes to subcomponents to the
IAG Executive Committee for approval.
(c) The component steering committee shall meet atleast once per year and at least once during each
IAG General Assembly.
(d) The component steering committee shall review at
one of its meetings (usually the IAG General
Assembly, or the IAG Scientific Assembly):(i) the activities of the subcomponents over the
past period;(ii) the structure of the subcomponents; and(iii) the programs for the forthcoming period for
those subcomponents that will be recommended for continuation.
(e) The component steering committee shall inform the
IAG Secretary General about all relevant issues.
(f) The component steering committee may organize
scientific and organizational meetings and workshops provided that they are readily distinguished
as being of a more limited scope than IAG
Scientific symposia or IAG Sponsored Symposia
as described in Bylaws 27 and 28.

4. Commission Responsibilities
Commissions shall promote the advancement ofscience, technology and international cooperation in
their field. They establish the necessary links withsister disciplines and with the relevant Services.
Commissions shall represent the Association in all
scientific domains related to their field of geodesy.

5. Commission Steering Committee(a) The Commission Steering Committee shall be set
up at each IAG General Assembly following theelection of the Association officers.
(b) The Steering Committee shall have the following
voting members:(i) Commission President.
(ii) Commission Vice President.
(iii) Chairs of the Sub-commissions and Commission Projects.
(iv) Up to three representatives of the Services
relevant to the work of the Commission.
(v) Up to two Members-at-Large to balance geographical and member country representation.

6. Appointment of Commission Officers(a) The Commission President shall be elected by theCouncil for one period without reappointment
except where exceptional circumstances justify
reappointment.
(b) The Commission Vice President shall be appointed
by the IAG Executive Committee for one period
without reappointment except where exceptional
circumstances justify reappointment.
(c) Chairs of the Sub-commissions and Commission
Projects shall be nominated by the Commission
President and Vice President within two months
following the General Assembly.
(d) The representatives of the Services shall be
appointed by the Commission President and Vice
President upon proposal of the Services.
(e) The Members-at-Large shall be nominated by theCommission President and Vice President within
two months following the IAG General Assembly.
(f) The appointments of Members-at-Large and Chairsof Sub-commissions and Commission Projects takeeffect on approval of the nominations by the IAG
Executive Committee.

7. Tasks of Commission Steering Committee
The Commission Steering Committee is subject to thegeneral responsibilities of component steeringcommittees in Bylaw 3(c), 3(d), 3(e), and 3(f) above.
In particular, its tasks are to:(a) Review the Commission's field of interests andobjectives.
(b) Liaise with the other IAG commissions, the Intercommission Committees, and with similarorganizations outside the IAG, as appropriate.
(c) Foster active participation of young geodesists andgeodesists from under-represented countries.
(d) Coordinate and review the work of its components
and report at the time of the Scientific Assembly to
the IAG Executive Committee on the progress andperformance of the components.
(e) Encourage and organize Commission and interdisciplinary symposia and/or sessions at major
geodesy related international meetings.
(f) Maintain a Commission website and e-mailservice.
(g) Nominate up to three editors for the Journal of
Geodesy.

IAG Bylaws

8. Current Commissions
On the coming into effect of these bylaws, there shallbe four Commissions with areas of scientific responsibility as outlined below:(1) Commission 1: Reference Frames(a) Establishment, maintenance, improvement of
the geodetic reference frames.
(b) Advanced terrestrial and space observation
technique development for the above purposes.
(c) International collaboration for the definitionand deployment of networks of terrestriallybased space geodetic observatories.
(d) Theory and coordination of astrometric observation for reference frame purposes.
(e) Collaboration with space geodesy/ reference
frame related international services, agencies
and organizations.
(2) Commission 2: Gravity Field(a) Terrestrial, marine, and airborne gravimetry.
(b) Satellite gravity and altimetry observations.
(c) Gravity field modelling.
(d) Time-variable gravity field.
(e) Geoid determination.
(f) Satellite orbit modeling and determination.
(3) Commission 3: Earth Rotation and Geodynamics(a) Earth orientation (Earth rotation, polar motion,nutation and precession).
(b) Earth tides.
(c) Tectonics and crustal deformation.
(d) Sea surface topography and sea level changes.
(e) Planetary and lunar dynamics.
(f) Effects of the Earth's fluid layers (e.g., post
glacial rebound, loading).
(4) Commission 4: Positioning and Applications(a) Terrestrial and satellite-based positioning systems
development, including sensor and information
fusion.
(b) Navigation and guidance of platforms.
(c) Interferometric laser and radar applications (e.g.,Synthetic Aperture Radar).

927(d) Applications of geodetic positioning using three
dimensional geodetic networks (passive and active
networks), including monitoring of deformations.
(e) Applications of geodesy to engineering.
(f) Atmospheric investigations using space geodetic
techniques.

9. Commission Subcomponents and Joint
Subcomponents(a) Commission Subcomponents are Sub-commissions, Commission Projects, Study Groups, andWorking Groups, which all belong to one commission.
(b) If more than one component is involved in a
subcomponent, the term joint subcomponent will
be used, e.g. Joint Sub-commission, Joint
Commission Project, Joint Study Group, Joint
Working Group.

10. Sub-commissions and Joint Sub-commissions(a) A Sub-commission may be set up for topics where
the Commission plays a leading or coordinating role.
(b) Where a topic relates to the scientific responsibilities of more than one IAG component, a Joint Subcommission shall be established under the lead of
one Commission.
(c) A Sub-commission is expected to be establishedfor several periods.
(d) Sub-commissions are established and terminatedby the IAG Executive Committee upon recommendation from the Commission President.
(e) A proposal to the Executive Committee for a Joint
Sub-commission requires the recommendation of
the Presidents of all contributing components.

11. Commission Projects and Joint Projects(a) A Commission Project may be established when a
new scientific method or a new technique is being
developed, or when it seems appropriate to apply
an existing technique to a specific geographic area
where international collaboration is required.
(b) Where a topic for a Commission Project relates tothe scientific responsibilities of more than one
Commission, or a Commission and a Service, aJoint Commission Project shall be establishedunder the lead of one Commission.
(c) A Commission Project is established for one period
and may be extended for another period subject toa positive review.

The Geodesist’s Handbook 2016928(d) Commission Projects are established, extended andterminated by the IAG Executive Committee uponrecommendation from the Commission President.
(e) A proposal to the Executive Committee for a Joint
Commission Project requires the recommendationof the Presidents of all contributing Components.

12. Study Groups, Working Groups, Joint
Study Groups and Joint Working Groups(a) A Study Group or Working Group may be established at any time to address clearly defined wellfocused scientific topics of limited scope within thefield of the Commission. A Study Group deals withmore theoretical issues and a Working Group withmore practical realizations.
(b) Where a topic for a Study Group or Working
Group relates to the scientific responsibilities ofmore than one Commission, or a Commission anda Service, a Joint Study Group or a Joint Working
Group shall be established.
(c) A Study Group or Working Group is established
for one period or less.
(d) Study Groups and Working Groups, including theposition of the group chair, are established andterminated by the IAG Executive Committee uponrecommendation from the Commission President.
(e) A proposal to the Executive Committee for a Joint
Study Group or Joint Working Group requires therecommendation of the Presidents of allcontributing components.

13. Services(a) IAG Services generate products, using their own
observations and/or observations of other services,
relevant for geodesy and for other sciences andapplications. Accuracy and robustness of products,
quality control, timeliness, and state of the art
quality are the essential aspects of the Services.
(b) Each Service shall define its Terms of Reference asappropriate to accomplish its mission and shallsubmit the Terms of Reference to the IAG
Executive Committee for approval.
(c) Each Service shall have an IAG representative,
appointed by the IAG Executive Committee, as avoting member of its directing/governing board.
(d) Services are linked to at least one of the Commissions and may be also linked to other scientificorganizations, such as the World Data System(WDS) or the International Astronomical Union(IAU).
(e) Services should collaborate on a scientific basiswith the Commissions, establish Joint Commission
Projects and Joint Study Groups and help compile
the Commissions' list of themes for Study Groups.
(f) Three representatives shall be elected in accordance with Bylaw 39 to the IAG Executive
Committee to serve the interests of all Services.
(g) On any matter relating to the products of a Service,
the Service shall represent the IAG.

14. Current Services(f) The Chair of a Study Group or Working Group is
responsible for initiating and directing its work andappointing its members.

On the coming into effect of these Bylaws, there shallbe fourteen Services as outlined alphabetically:(g) Study Group and Working Group membershipshould be balanced so as to reflect international
cooperation in its subject.

(b) International Bureau of Weights and Measures(BIPM) Time Department(h) A Study Group or Working Group may have notmore than 20 full members and an unlimited
number of correspondent members.
(i) The Chair of each Study Group or Working Groupshall issue a brief description of the work to be
performed and a list of members, to be published in
the Geodesist's Handbook after each General
Assembly.
(j) The Chair of each Study Group or Working Groupshall report annually to its members and thecommission steering committee, on results
achieved and outstanding problems.

(a) International Altimetry Service (IAS)(c) International Centre for Global Earth Models(ICGEM)(d) International Digital Elevation Models Service(IDEMS)(e) International DORIS Service (IDS)(f) International Earth Rotation
Systems Service (IERS)

andReference(g) International Geodynamics and Earth Tides Service(IGETS)(h) International GNSS Service (IGS)(i) International Gravimetric Bureau (BGI)(j) International Gravity Field Service (IGFS)

IAG Bylaws(k) International Laser Ranging Service (ILRS)(l) International Service for the Geoid (ISG)(m) International VLBI Service for Geodesy andAstrometry (IVS)(n) Permanent Service for Mean Sea Level (PSMSL)

15. The Global Geodetic Observing System(GGOS)(a) The GGOS is IAG’s observing system to monitor
the geodetic and the global geodynamic propertiesof the Earth as a system.
(b) GGOS works with other IAG components, such as
the IAG Services and the IAG Commissions, aswell as the Inter-commission Committees, toprovide unique, mutually consistent, and easily
accessible geodetic products (including the geometric reference frames and the gravity field) andthe relevant geodetic constants for science and society.
(c) GGOS operates on its own Terms of Reference,
defined by the GGOS Coordinating Board (CB)and approved by the IAG Executive Committee.
GGOS nomination and election procedures are
specified in its Terms of Reference.
(d) The GGOS Chair is appointed by the IAG Executive Committee in consultation with GGOS CB for
one four-year period, which may be renewed once.

16. IAG Projects(a) IAG Projects are flagship long-term projects of abroad scope and of highest interest and importancefor the entire field of geodesy.
(b) Planning for the creation of an IAG Project shall be
carried out by a planning group established by the
Executive Committee.
(c) The Project Steering Committee shall have thefollowing voting members:(i) The Project Chair appointed by the IAG Executive Committee(ii) One member from each Commission appointed
by the Commissions' Steering Committee(iii)
Two Members-at-Large proposed by themembers of the Project Steering Committee
identified in clause (i) and (ii) above andapproved by the IAG Executive Committee.
(iv)
Chairs of the IAG Project Working
Groups (if any).
(v) Representatives of other IAG components, as
appropriate.

929(d) IAG Project Subcomponents are Working Groups
but not Study Groups.

17. Inter-commission Committees(a) Inter-commission Committees shall handle welldefined, important and permanent tasks involving
all Commissions.
(b) Each Inter-commission Committee shall have asteering committee, which shall include the following members:(i) President appointed by the IAG Executive
Committee.
(ii) Vice President appointed by the IAG Executive Committee on the recommendation of thepresident.
(iii) One representative appointed by each Commission.
(c) The terms of reference for each Inter-commission
Committee shall be developed by a planning group
appointed by the IAG Executive Committee forapproval by the Executive Committee.
(d) Inter-commission Committees will be established
for at least 2 periods (eight years) and shall be
reviewed by the Executive Committee every eight
years.
(e) The Inter-commission Committees shall report to
the IAG Executive Committee.

18. Communication and Outreach Branch(COB)(a) The function of the Communication and OutreachBranch is to provide the Association with
communication, educational/public informationand outreach links to the membership, to otherscientific Associations and to the world as a whole.
(b) The responsibilities of the Communication andOutreach Branch shall include the following tasks:(i) Promote the recognition and usefulness of geodesy in general and IAG in particular.
(ii) Publications (newsletters).
(iii) Membership development.
(iv) General information service and outreach.
(c) The Communication and Outreach Branch shallalso assist the IAG General Secretary, in thefollowing tasks as required:(i) Maintenance of the IAG website.
(ii) Setting up Association schools.
(iii) Setting up meetings and conferences.

The Geodesist’s Handbook 2016

930(d) The IAG Executive Committee establishes the
COB on a long-term basis by issuing a Call for
Participation. The responding organization(s) andthe IAG Executive Committee shall then negotiate
the Terms of Reference and other conditions.
(e) The President of the Communication and OutreachBranch shall be elected by Council.
(f) Major decisions related to the operations of the
COB shall be made by a Steering Committee consisting of the following voting members:(i) Communications
President.

andOutreach

Branch(ii) IAG Secretary General.
(iii) Editor-in-Chief of the Journal of Geodesy.
(iv) Editor-in-Chief of the IAG Symposia Series.
(v) Up to 5 other members appointed by the
Executive Committee on the recommendationof the President of the Communications andOutreach Branch.

19. IAG Publications(a) The IAG publications include the Journal of Geodesy, the IAG Symposia Series, the Geodesist's
Handbook, the "Travaux de l'Association Internationale de Géodésie," the IAG Newsletter, andIAG Special Publications.
(b) The Association's journal is the Journal of Geodesy, hereinafter referred to as the journal. The
journal is published monthly through an agreement
between the Association and a publishingcompany, or by other arrangement approved by the
Executive Committee. The terms of any agreement
for publication of the journal shall be negotiated by
the President of the Communications and OutreachBranch and ratified by the Executive Committee.
(c) The journal publishes peer-reviewed papers, covering the whole range of geodesy, including geodetic
applications.
(d) After each IAG General Assembly, a special issueof the Journal of Geodesy shall be published under
the name of "The Geodesist's Handbook". Thisissue provides the actual information on the
Association, including the reports of the President
and Secretary General presented at the previous
IAG General Assembly, the resolutions taken atthat Assembly, and the Association structure listing
all components and subcomponents for the running
period, rules for the IAG Fund, IAG Awards andfor the conduct of scientific meetings as well as
relevant scientific information.
(e) The IAG Symposia Series publishes peer-reviewed
papers related to presentations made at IAG and/or
IAG-sponsored Symposia provided that sufficientnumber of papers are submitted and accepted for
publication.
(f) After each IAG General Assembly, a collection of
the reports by the Association components shall be
published in the "Travaux de l'Association
Internationale de Géodésie". This publication is
supplied free of charge to the officers of the
Association and to the Adhering Body of eachmember country.
(g) At every IAG General Assembly each member
country is encouraged to a National Report on
geodetic work done since the previous General
Assembly to be placed on the IAG website. These
National Reports, as far as available, are distributedby the IAG Office in the same manner as the"Travaux de l'Association Internationale de Géodésie".
(h) The IAG Newsletter is under the editorial responsibility of the Communication and OutreachBranch. It should be published on the IAG website
and distributed to members electronically.

20. Editor-in-Chief and Editorial Board(a) There shall be one Editor-in-Chief for the journal,
hereinafter referred to as the Journal Editor. An
Assistant Editor-in-Chief may assist the Journal
Editor. The Journal Editor shall be advised andassisted by a Board of Editors, hereinafter referred
to as the Board. To ensure broad expertise, each of
the Commissions may nominate up to threemembers of the Board.
(b) The Journal Editor shall be responsible for thescientific content of the journal. The Journal Editor
shall make the final decision on whether a refereed
scientific manuscript is accepted for publication.
The Journal Editor shall keep the Executive
Committee informed of the activities and status ofoperations of the journal.
(c) Three months before each General Assembly, thecurrent Journal Editor, in consultation with the
Bureau, shall recommend a preliminary list of
candidates for the new Board of Editors. This list
shall be published on the IAG website at least twomonths in advance of the General Assembly tosolicit additional nominations for the EditorialIAG Bylaws

931

Board from the geodetic community. The
additional candidates will be added to the list.

(iv) Reduction of the registration fee for IAG
meetings as set under Bylaws 26(d) and 27(b).

(d) At the General Assembly, the current Board shallappoint the members of the new Board from thoserecommended. After taking office, the new Board
shall nominate the new Journal Editor and the new
Assistant Editor for the next period. After approvalof these nominations by the Executive Committee,
the Journal Editor and the Assistant Editor will beconsidered as elected. Concurrence with the
Publisher will be sought.

(e) The membership fee per annum is set by the
Executive Committee. In setting the fee the Executive Committee will consider a recommendationfrom the Secretary General.

(e) The Journal Editor, the Assistant Editor, and themembers of the Editorial Board shall each holdoffice for one period, but may be eligible to be reelected for one further period.
(f) There shall be one Editor-in-Chief for the IAG
Symposia Series, hereinafter referred to as theSeries Editor. He/she is appointed by the Executive
Committee for a four year period. An assistant
Editor-in-Chief may also be appointed for the sametime period.
(g) The Series Editor shall be responsible for thescientific content of the IAG Symposia Series. On
the recommendation of the volume editors, theSeries Editor shall make the final decision onwhether a refereed scientific manuscript is
accepted for publication. The Series Editor shallkeep the Executive Committee informed of theactivities and status of operations of the IAG
Symposia Series.
(h) Each volume of the IAG Symposia Series shallhave additional Volume Editors.

21. Individual Membership(a) Individuals engaged in geodesy, can become individual members of the Association on applicationand payment of the membership fee.
(b) Applications for individual membership are submitted to the Secretary General.
(c) The decision on the membership application shallbe made by the Bureau.
(d) Benefits of membership include(i) Substantial reduction on the individual subscription rate to the Journal of Geodesy.
(ii) The right to participate in the IAG election
process both as a nominator and a nominee.
(iii) Upon application, correspondent membershipin a sub-commission or study group of choice.

(f) In individual cases, the Secretary General may
consider a discount or full remission of membership fees on application by the member.
(g) Where a member provides a donation in excess ofthe membership fee, the excess shall be assigned to
the IAG Fund in support of young scientists.
(h) Membership is terminated if the membership fee is
not paid or if an application for discount or fullremission has not been received one year after thefee was due.

22. Honorary Officers, Fellows(a) The Executive Committee may appoint a merited
past President as Honorary President or a merited
Secretary General as Honorary Secretary General.
(b) The Executive Committee may appoint past
officers of the Association as Fellows.

23. IAG Fund
The Executive Committee may establish a fund (IAG
Fund) for supporting specific IAG activities as definedin the IAG Fund Rules, to be published in the
Geodesist's Handbook in accordance with Bylaw
19(d). The fund is under the direct responsibility of the
President; the fund's resources are administered by the
Secretary General.

24. IAG Awards
The Executive Committee may establish awards foroutstanding contributions to geodesy and distinguishedservice to the Association. The rules for the awards are
published in the Geodesist's Handbook in accordancewith Bylaw 19(d).

25. Administration
Assemblies

of

the

IAG

General(a) The IAG General Assembly will be held at thesame time and the same place as the IUGG General
Assembly.
(b) Before any IAG General Assembly, the Bureau of
the Association shall prepare detailed agendas for
the Council meetings, Executive Committee
meetings, the opening and the closing sessions.

The Geodesist’s Handbook 2016

932(c) The Executive Committee shall draw up the agenda
for the scientific program. Joint Symposia covering
topics of interest to two or more Associations
within the Union may be arranged.
(d) The agendas developed according to (b) and (c)above are sent to the member countries and to all
the officers of the Association so as to reach themat least two months prior to the IAG General
Assembly. In principle, only matters on the agenda
may be considered during the sessions, unless a
decision to do otherwise is passed by a two-thirds
majority in the Council concerning the agenda of
the Council meeting.
(e) At each IAG General Assembly, the President shallpresent a detailed report on the scientific work of
the Association during his/her tenure. The
Secretary General shall present a detailed report on
the administrative work and on the finances of the
Association for the same period. The President andSecretary General should include in their reports,
proposals for work to be undertaken during thecoming period, within the limits of expectedresources. These reports shall be published in "The
Geodesist's Handbook".
(f) At each IAG General Assembly, the work of eachCommission, each Service, the Communication
and Outreach Branch, and each IAG Project shallbe reported by its President / Chair. IAG
Representatives to other scientific bodies report to
the Executive Committee.

26. Scientific Meetings(a) Scientific meetings of the IAG are:(i) the Scientific Symposia held during a General
Assembly;(ii) Scientific Assemblies, including ScientificSymposia; and(iii) IAG sponsored Symposia.
(b) The IAG Newsletter shall include on a regularbasis a Calendar of IAG Symposia and otherscientific meetings organized or sponsored by the
IAG or its components.
(c) The Executive Committee shall appoint an official
IAG Scientific Meeting Representative for each of
the scientific meetings other than the General
Assembly and the Scientific Assembly to be
governed by these Bylaws. The representative is
obliged to remind the organizers to obey the
Bylaws for scientific meetings and to report backto the Executive Committee.

(d) A reduced registration fee shall be offered forindividual members in accordance with 21(d) (iv).

27. Scientific Assemblies(a) Scientific assemblies are held mid-way during theperiod between two IAG General Assemblies andshall consist of a group of component meetings
and/or a group of Scientific Symposia, held at thesame time and place.
(b) A reduced registration fee shall be offered forindividual members in accordance with 21(d) (iv).

28. Scientific Symposia(a) Scientific symposia take place at the IAG General
Assembly and the IAG Scientific Assembly. In
general, they shall be organized by Association
components and subcomponents, and be led bytheir respective chairs.
(b) The study of some questions may require joint
meetings of several components under a chair,appointed by the Executive Committee. A committee consisting of the component chairs shalldecide on the agenda and on the inclusion of scientific presentations.
(c) At each IUGG General Assembly Joint ScientificSymposia covering topics of interest to two or
more Associations within the IUGG and/or otherinternational scientific organizations may bearranged. Though the IAG may be asked to act asconvenor or co-convenor, these symposia shallfollow the rules issued by the IUGG. The IAG may
participate also in joint symposia at any other timeoutside of the IAG General Assembly obeying thesame procedures.
(d) The arrangement of a scientific symposium shall be
subject to the usual approval procedure provided
by in the Geodesist's Handbook in accordance with
Bylaw 19(d).

29. IAG Sponsored Symposia(a) The IAG may sponsor a symposium covering
broad parts of geodesy and having large attendanceat any suitable time outside the IAG General
Assemblies or Scientific Assemblies, and shall callit an IAG Sponsored Symposium, provided thefollowing conditions are fulfilled:(i) One or more Association component or subcomponent shall sponsor it or at least two
Study Groups.

IAG Bylaws

933(ii) Host organization of the symposium shallaccept a representative in the Scientific
Organizing Committee (SOC) appointed by the
IAG Executive Committee.

(iii) Receive reports from the Secretary Generaland consider for approval the decisions or
actions taken by the Bureau and the Executive
Committee since the last Council meeting.

(iii) The symposium shall be open to all bona-fidescientists in accordance with the ICSU rules.

(iv) Set up and dissolve Association components.

(iv) The symposium proceedings shall be published.
(b) The SOC appointed under 29(a)(ii) above shallbe responsible for the quality of science of thesymposium being at a high level. A Local
Organizing Committee (LOC) shall take careof the organization and logistics.
(c) Applications for approval of an IAG
Symposium should be submitted to theSecretary General at least one year before theintended date of the meeting.

30. International Cooperation(a) The Association may participate in joint bodies of
the IUGG and other scientific organizations,especially those belonging to the International
Council for Science (ICSU). These bodies shall beadministered according to their specific rules.
(b) The Association shall initiate international cooperation in scientific work of international andinterdisciplinary character. This includes theadequate participation in international programs
and projects and the representation at scientificcongresses, symposia etc. of organizations withrelated activities.
(c) Representatives to international programs andprojects shall be appointed by the Executive
Committee and shall inform the EC on the activities, on a biannual basis. The representatives shallalso prepare a report to be presented at the IAG
General Assembly.

31. Duties of the Council(a) In addition to any other functions, powers andduties provided in other Statutes and Bylaws, theCouncil shall:(i)Examine questions of general scientific policy
or administration, and propose actions deemednecessary.

(ii) Elect the voting members of the Executive
Committee, with the exception of the GGOS
Chair, see 15(d) and the ICCT President, see17(b(i)).

(v) Appoint the three members of the ad hoc(audit) committee created for examining thefinances of the Association, consider its
recommendations and adopt the final budget.
(vi) Consider proposals for changes in the Statutes
and Bylaws.
(vii) Decide on the venue of IAG Scientific Assemblies.
(viii) Approve the establishment of InterCommission Committees and IAG Projects.
(b) Council meetings shall be convened by the President of the Association. It shall meet at least once
during each IAG General Assembly and may be
convened at other times, normally coinciding with
the IAG Scientific Assembly according to the
Statutes 13b.

32. Duties of the Executive Committee(a) In addition to any other functions, powers andduties provided in other Statutes and Bylaws, theExecutive Committee shall:(i)

Initiate actions and issue guidelines, as required, to guide the Association towards theachievement of its scientific objectives.

(ii) Fill vacancies occurring between IAG General
Assemblies, in accordance with the Statutes
and Bylaws.
(iii) Approve the internal structure of Association
components.
(iv) Make recommendations to the Council onmatters of general policy of the Associationand on the implementation of its objectives.
(v) Appoint Honorary Officers and Fellows of the
Association, upon the recommendation of the
Bureau.
(vi) Appoint planning groups for Inter-commission Committees and IAG Projects.
(vii) Establish Inter-commission Committees and
IAG Projects.
(viii) Appoint a Committee for reviewing andupdating the IAG Statutes and Bylaws when
deemed necessary.

The Geodesist’s Handbook 2016934(ix) Confirm the Assistant Secretaries of the Association.
(x) Confirm the links between Commissions andServices.
(xi) Adopt the suggested membership fee(xii) Appoint the Vice President of each Commission.
(xiii) Appoint representatives to external bodies.
(b) Executive Committee meetings shall be convenedby the President of the Association. It shall meet at
IAG General Assemblies and its members are
expected to attend the meetings of the Council,
with voice but without vote. It shall also meet
normally at least once a year, especially one year
before the IAG General Assembly, in order toprepare the scientific agenda and the timetable ofthe next IAG General Assembly.
(c) At a meeting of the Executive Committee, nomember may be represented by any other person,
except by the corresponding Vice Presidents orVice Chairs of the IAG components represented in
the EC. In order that the deliberations of the
Executive Committee shall be valid, a quorum of atleast half of its members must be present or
represented.
(d) The agenda for each meeting of the Executive
Committee shall be prepared by the Bureau andsent to the members at least two months prior tothe meeting.

33. Duties of the Bureau(a) In addition to any other functions, powers andduties provided in other Statutes and Bylaws, theBureau shall:(i) Draw up the agenda of the meetings of theCouncil and Executive Committee and send
these to the members at least two months prior
to the meeting.
(ii) Ensure the adequate administration of the
Association.
(iii) Receive applications for individual memberships and accept individuals as Members of the
Association.
(iv) Recommend Honorary Officers and Fellows to
the Executive Committee.
(b) The Bureau shall normally meet before eachmeeting of the Executive Committee.

34. Duties of the President
In addition to any other functions, powers and duties
provided in other Statutes and Bylaws, the President
shall:(a) Provide general leadership for the Association in
all matters.
(b) Convene and preside over the IAG General
Assembly and over all meetings of the Council,
Executive Committee and Bureau.
(c) Represent the Association in the International
Union of Geodesy and Geophysics.
(c) Represent the Association in its dealing withnational or international organizations or institutions.
(d) Submit a report to the IAG General Assembly on
the scientific work of the Association duringhis/her tenure.

35. Duties of the Vice President
In addition to any other functions, powers and duties
provided in other Statutes and Bylaws, the Vice
President shall act as the President whenever the
President is not present or is unable to perform any of
the President’s duties, and shall perform such tasks as
may be assigned by the President, the Executive Committee or the Council.

36. Duties of the Secretary General
In addition to any other functions, powers and duties
provided in other Statutes and Bylaws, the Secretary
General shall:(a) Serve as secretary of the General Assembly, the
Scientific Assembly, the Council, the Executive
Committee and the Bureau; arrange for meetings ofthese bodies, distribute promptly the agenda andprepare and distribute the minutes of all their
meetings.
(b) Act as Director of the IAG Office.
(c) Manage the affairs of the Association including
finances as per 42(b), attend to correspondence,and preserve the records.
(d) Circulate all appropriate information related to the
Association.
(e) Prepare the reports of the Association's activities.
(f) Perform such other duties as may be assigned by
the Bureau.

IAG Bylaws(g) The function of the Secretary General is unpaid
and only expenses incurred in connection with thefunctions and duties are repayable.

37. Assistant Secretaries(a) The Secretary General is assisted by a small
number of assistant secretaries.
(b) The position of Assistant Secretary is unpaid andonly expenses incurred in connection with thefunctions and duties are repayable.

38. IAG Office
To assist the Secretary General, the Association establishes the IAG Office in the country in which theSecretary General resides. The Executive Committee
negotiates logistical and financial support with the hostcountry.

39. Procedure for Nominations and Electionsof Officers(a) Elections shall take place by e-mail vote before
each IAG General Assembly and should becompleted one month before the assembly.
(b) The President of the Association, after taking
advice from the Executive Committee, shallappoint a Nominating Committee consisting of a
Chair and three other members.
(c) The Nominating Committee, after taking advice
from the Delegates of the Adhering Bodies, theofficers, fellows, and members of the Association,
shall normally propose at least two candidates foreach position to be filled by election in theCouncil. Candidates shall be asked to signify theiracceptance of nomination and to prepare a resume,
maximum 150 words, outlining their position,
research interests and activities relating to the
Association.
(d) The Adhering Bodies and the individual membership shall be informed of these nominations threemonths before the IAG General Assembly.
(e) During the following month further nominations
can be submitted by the Delegates of the Adhering
Bodies. Such additional nominations shall be inwriting, shall be supported by at least two membersof the Council, and shall be submitted withresumes as described above to the Chair of theNominating Committee.
(f) Nominations shall be checked against the eligibility criteria in Bylaw 40 by the Nominating
Committee. Ineligible nominations will not be

935

accepted and the members of Council who
supported the nomination will be advised of thereason for its rejection.
(g) Delegates shall be informed of these further
eligible nominations and resumes and of theirsupporters.
(h) The Chair of the Nominating Committee shallwrite to all Services asking them for one nomination from each Service for the Service representatives in the Executive Committee. The Nominating Committee shall recommend normally two
nominees for each of the Services’ three positions,considering appropriate scientific and national
distribution. The procedure for seeking additional
nominations in sub clause (e) above does not apply
to these positions.
(i) If candidates have been nominated for more than
one position, they will be asked to make a decision
for which position they will allow their name tostand.
(j) Elections shall be by e-mail ballot and by majority
vote.
(k) The Members-at-Large shall be elected in a second
round after the other members of the Executive
Committee are known, in order to fulfil thecondition of geographical and organizationalbalance (see Statutes 12a).

40. Eligibility and Terms of Office(a) No person may hold more than one of the following offices at the same time: President of the
Association, Vice President, President of aCommission, President of an Inter-commission
Committee, Chair of a Service, Chair of GGOS,
President of the Communication and OutreachBranch, Chair of an IAG Project.
(b) A member of the IUGG Bureau or of the IUGG
Finance Committee may not occupy the post of
President, of Vice President or of Secretary
General of the Association.
(c) The President of the Association is elected for one
period and may not be immediately re-elected tothe same office.
(d) The Vice President is elected for one period andmay not be re-elected to the same office.
(e) The Secretary General is elected for one period
initially. He/she may be re-elected for two
additional periods.

The Geodesist’s Handbook 2016936

41. Extraordinary Vacancies(iv) Membership fee.

(a) Should the position of President become vacant during
the Period between two IAG General Assemblies, his
duties devolve to the Vice President until the closureof the next IAG General Assembly.

(v) A portion of the registration fee charged at
IAG symposia.

(b) Should the post of Secretary General become
vacant, the President shall arrange without delay
for the Executive Committee to propose a replacement and for the Council to appoint a new
Secretary General so as to ensure the continuity of
the work of the IAG Office. This appointment has
effect until the closure of the next IAG General
Assembly and shall not be counted in the
restriction of eligibility for re-election of theSecretary General under Bylaw 40(e).

(b) The Secretary General is responsible to the Bureau
and to the Council for managing the funds inaccordance with the Statutes and Bylaws, with thedecisions of the Council. The Secretary Generalalone shall be responsible for control of thefinancial operations of the Association.

42. Finances(a) The Finances of the Association derive from thefollowing sources:(i) Contributions of IUGG Adhering Bodies ofwhich a portion, determined by the IUGG
Council on recommendation of its FinanceCommittee, is paid to the Association by theTreasurer of the Union.
(ii) Sale of publications.
(iii) IAG Fund collected from individual contributions for specific purposes.

(vi) Other sources e.g., grants, interests, and funds
remaining after a symposium.

(c) At each IAG General Assembly the budget
proposal for the next period shall be presented by
the Secretary General and submitted for approvalto the Council. The budget as approved by theCouncil shall be implemented by the Secretary
General.
(d) During each IAG General Assembly, the Council
shall examine all expenditures during the preceding
period to ensure that they were in accordance withthe proposed budget previously approved. This
examination shall be carried out by an ad hoc(audit) committee appointed by the Council; seealso 31(a)(v).
(e) In addition, the accounts shall be audited by aqualified accountant and shall then be reported to
the IUGG Treasurer, as prescribed in Article 20 of
the IUGG Bylaws.

IAG Rules

937

Rules for IAG Scientific Meetings

1. IAG scientific meetings are organized by IAG components (Commissions, Inter-commission Committee on
Theory, Services, and the Global Geodetic Observing
System) or IAG Sub-components (Sub-commissions,other Inter-commission Committees, Projects, Study
Groups, Working Groups). They may take place:a) during IAG General Assemblies, held in conjunction with the IUGG General Assemblies,b) during IAG Scientific Assemblies, held in-between
successive General Assemblies, orc) at any time and place apart from the General or
Scientific Assemblies.
2. During the General or Scientific Assemblies symposia
and other meetings are in general organized by IAG
components or sub-components. For specific topics
there may be joint symposia of several components or
sub-components under a convener appointed by the
IAG Executive Committee. The inclusion of scientificpapers for presentation at a General or Scientific
Assembly is decided by a Scientific Committee
established by the IAG Executive Committee.
3. At General Assemblies joint symposia covering topics
of two or more Associations within the Union and/or
other international scientific organizations may beorganized. Though the IAG may act as convener or coconvener, these symposia follow the IUGG rules.
4. The IAG may participate also in joint symposia withother Associations at any other time outside of theGeneral Assemblies, following the same procedures.
5. The IAG may sponsor symposia covering appropriate
topics of Geodesy at any time outside of the General or

Scientific Assemblies. It shall be called IAG sponsored
Symposium if the following conditions are fulfilled:
x The symposium has to be organized by at least one
component or two sub-components of the IAG.
x The host organization of the symposium must accept
a representative in the Scientific Organizing
Committee (SOC) appointed by the IAG Executive
Committee.
x The symposium must be open to all bonafide
scientists in accordance with the ICSU rules.
x The proceedings of the symposium shall be published.
x If there is a registration fee, it must be reduced for
IAG members by at least 10%.
x Immediately after the end of the Symposium thechairperson of the Scientific Committee shall prepare asummary to be published in the IAG Newsletter.
6. Applications for approval to be designated IAG Symposium should be submitted to the Secretary General of
the IAG at least twelve months before the proposed
date of the Symposium. The following informationmust be provided in the application for approval:a) Title,b) Date and duration,c) Location,d) Sponsoring IAG (Sub-) components,e) Other co-sponsoring scientific organizations withletters enclosed,f) Suggested composition of the Scientific Organizing
Committee,g) Local Organizing Committee, host organization,
name and address of contact, etc.
h) Estimated number of participants,

The Geodesist’s Handbook 2016

938i) Financial support expected from sources other thanthe IAG,j) Names of the proposed editors of proceedings,k) Draft scientific program,l) A detailed account of why the proposed symposium
is useful and necessary at the time proposed, and its
relationship with other meetings.
7. Guidelines for the organization of the symposium:a) The Scientific Organizing Committee is responsible
for ensuring a high standard of scientific value ofthe symposium. The chair of the Committee:
x invites participants after the symposium isapproved by the IAG Executive Committee,
x invites contributions and sets a deadline for submissions of abstracts, andx informs the IAG Secretary General of all important matters pertaining to the symposium.
b) The Local Organizing Committee is responsible forthe smooth running of the symposium. It does notreceive financial assistance from the IAG, with all
the necessary expenses being met by local funds orby contributions from the participants. The requirements of local organizations are generally as follows:
x providing meeting rooms suitable for the
expected number of participants,
x providing the facilities for oral and visual presentations,x provide adequate space and logistical support for
poster sessions (if any),x reproduction of participants’ document (if necessary), organize publication of proceedings or production of CD version,x sufficient secretarial and technical assistance,x undertake full responsibility for registration ofparticipants, maintaining a web page, printing ofbrochures and programmes, etc.
x information on accommodation (hostels, hotels,
etc...), sent to the IAG Executive Committee for
acceptance, and to prospective participants,
x organizing receptions and excursions during afree period within the meeting, or just before orafter the meeting.

8. The IAG Executive Committee shall recognize scientific meetings other than symposia (workshops, etc.)
organized by IAG (Sub-) Components, alone or jointlywith other international and national groups and bodies,at any time outside of the General Assemblies, if they
have been approved by the Executive Committee. The
Meeting may be announced as "International Meeting,organized by the ....... of IAG". It is not permitted touse the term “IAG Symposium”.
9. The IAG may recognize scientific meetings, organizedby national bodies as important scientific events with
benefit for the international geodetic community, andsponsor them if the meeting is open to all scientists
according to the ICSU Rules, and will be sponsored byat least one IAG (Sub-) Component, and if theorganizer undertakes to maintain the expected standard
for IAG-Symposia.
These Meetings may be announced as "International
Meeting, organized by ....., sponsored by IAG". It is not
permitted to use the term “IAG Symposium”. Sponsorship by the IAG means only official recognition anddoes not imply financial support by the IAG. The IAG
may appoint an official representative to that meeting.
The IAG expects that, in the event that proceedings are
published, the Proceedings will be prepared by the
local organizers and published within 6-8 months after
the end of the meeting.
Applications for sponsorship should be submitted to
the IAG Secretary General not later than 12 months
before the intended date of the meeting.
10. In its decision whether to approve and/or sponsor ascientific meeting, the IAG Executive Committee takes
into account the need for a balanced selection of meetings, a representative coverage of subjects, and a good
geographical distribution. The IAG wishes to avoid
duplication of symposia or meetings, and to discourage
symposia or meetings with overlapping themes that areheld with too high a frequency.
The IAG Secretary General shall publish a calendarof IAG Symposia and other scientific meetingsorganized or sponsored by IAG components or subcomponents in the IAG Newsletter, in the Journal of
Geodesy, and on the IAG Website.

IAG Rules

939

Rules for the IAG Levallois Medal

PurposeThe Levallois Medal was established by the International
Association of Geodesy in 1979 to honour Jean-Jacques
Levallois, and to recognize his outstanding contribution to
the IAG, particularly his long service as Secretary General,
1960-1975.
The award of the Medal will be made in recognition of
distinguished service to the Association, and/or to thescience of geodesy in general.
The Medal is normally awarded at four year intervals, on
the occasion of the General Assemblies of the International

Association of Geodesy and International Union of
Geodesy and Geophysics; but the award may be omitted if
it is considered that there is no candidature of sufficient
merit, and an additional award may be made at any time if
justified by exceptional circumstances.

Nomination and Election
A nomination for the award shall be made by an ad hoc
committee consisting of the Honorary Presidents and must
be confirmed by the IAG Executive Committee. The ad
hoc committee shall prepare a citation, suitable for publication, setting out the grounds for the proposed award
before the General Assembly.

The Geodesist’s Handbook 2016

940

Rules for the IAG Guy Bomford Prize

PurposeThe Guy Bomford Prize is awarded by the International
Association of Geodesy for outstanding contribution to Geodesy. It was established by the British National Committee
for Geodesy and Geophysics to mark the contributions togeodesy of Brigadier G. Bomford, formerly of the University of
Oxford and a Past President of the International
Association of Geodesy. It has been inaugurated by the
IAG in 1975. The Prize is normally awarded at intervals offour years on the occasion of the General Assembly of the
IAG held concurrently with the General Assembly of theInternational Union for Geodesy and Geophysics. The
following rules for the award of the Guy Bomford Prize
may be altered by the IAG Executive Committee if amajority of its voting members sees a necessity to do so.

Eligibility
The Guy Bomford Prize is awarded to a young scientist or
to a team of young scientists for outstanding theoretical orapplied contributions to geodetic studies particularly in thefour year period preceding the General Assembly at which
the award is made. Scientists who are under 40 years ofage on December, 31, of the year preceding the Assemblyat which the award is made, are eligible for the award.

Nominations
Nominations will be invited by the IAG Bureau from all
National Committees of IUGG member countries at least
one year ahead of the General Assembly. Each committee
can make one nomination which has not necessarily to befrom its own country. The deadline for nominations will
normally be six months before the next General Assembly
and will be explicitly started in the letter of invitation.

Nominations must be accompanied by:
x The full name, address, age, academic and/or professional qualifications and position of the candidates andthe name of the National Committee making the nomination.
x An outline of the reasons for the nomination including ageneral summary of the career and scientific achievementof the candidate.
x A review of recent achievements of the candidates which
would merit the award, including references to key
papers, published, alone or jointly, during the preceding
four-year period.
x A curriculum vitae, publication list, and copies of up to
two key papers which are considered to justify candidature.
x The name and address of two referees who can be consulted.

Selection procedure
A selection committee will be appointed consisting of thepresidents of the IAG commissions and two other members
to be appointed by the IAG Bureau. Based on the material
submitted by the National committees each member of theselection committee will rank the nominations and select thecandidate to be awarded the Guy Bomford prize. The decision(not the detailed ranking) will be communicated to all
National Committees and to the selected candidate. The prize
may be withheld if, in the opinion of the selection committee,
there is no sufficiently qualified candidate available.

Presentation of award
The Prize shall be presented to the successful candidate at
the opening Plenary Session of the IAG Assembly. He or
she shall be invited to deliver a lecture during the course of
the IAG Assembly.

IAG Rules

941

Rules for the IAG Young Authors Award

PurposeNomination and Selection

The award is to draw attention to important contributions
by young scientists in the Journal of Geodesy and to foster
excellence in scientific writing.

For each two-year period the Editor-in-Chief of the Journalof Geodesy will propose a minimum of three candidates
for the award. In addition, proposals made by at least three
Fellows or Associates will be considered for the competition. The voting members of the IAG Executive Committee will make the final selection. It will be based on theimportance of the scientific contribution, which may beeither theoretical or practical, and on the quality of thepresentation. The name and picture of the award winnerand a short biography will be published in Journal of
Geodesy.

Eligibility
The applicant must be 35 years of age or younger whensubmitting the paper for the competition. The paper must
present his or her own research, and must have been published in the two annual volumes of the Journal of Geodesy
preceding either the IAG General Assembly or the
Scientific Assembly. Although multiple author papers will
be considered, single author papers will be given moreweight in the selection process.

Award
The award consists of a certificate and a cheque of US $ 1000.
Presentation of the awards will be made at each IAG General
Assembly and each Scientific Assembly. Up to two awards
will be presented on each occasion for the two-year period
corresponding to the annual volumes specified above.

Procedure
Each year the conditions for the award will be announced
in the Journal of Geodesy. Nominations should be sent to
the Secretary General of the IAG, giving name, address,
and age of the author (at date of submission), the title ofthe paper on which nomination is based, and a brief justification. Nominations must be received by March 1 of theyear in which either an IAG General Assembly or an IAG
Scientific Assembly takes place.

The Geodesist’s Handbook 2016

942

Rules for the IAG Travel Awards

PurposeApplication procedure

The award is established to assist young scientists frommember countries to present results of their research at
IAG meetings (assemblies, symposia, workshops, etc.).

Applicants are asked to send their application at least threemonths before the meeting to the IAG Secretary General.
As a minimum, the application should contain: title,
authors, and abstract of the paper to be presented,
acceptance by the organising committee (if available),travel budget and sources of additional funding. The
letter(s) of support (one IAG Fellow or two Associates)
should be sent separately. An application form may befound at the IAG Website.

Eligibility
The applicant must present results of his or her research at
the meeting and must be 35 years of age or less at the dateof the application. The application must be supported by atleast one IAG Fellow or two Associates.

Type of awards
There are two awards, one for meetings in the applicant’s
own country, and the other for meetings outside the applicant’s country. The first is called IAG National TravelAward and has a maximum financial value of US $ 500. It
is available for meetings in developing countries. The
second is called IAG International Travel Award and has amaximum financial support of US $ 1000. The amounts
can occasionally be adjusted by the IAG Executive Committee. It was adjusted last in 2011.

Selection procedure and criteria
Selection of applicants will be done by the IAG Bureau. It
will be based on the paper to be presented, the letter(s) of
support, and the applicant’s ability to actually attend themeeting. Priority will be given to candidates fromdeveloping countries.

Additional benefits
The IAG will encourage the organizers of the meetings towaive the registration fees for all IAG Travel award winners.

IAG Fund and Membership943

IAG FundThe IAG Fund aims at supporting specific IAG activities.
Its primary goals are:• to provide travel support for young scientists to attend
IAG Symposia and workshops,• to assist in the organisation of IAG workshops indeveloping countries, and• to provide an annual IAG Best Publication Award foryoung scientists.
The fund was established by the IAG Executive Committee at its meeting in Columbus, Ohio, 1992, see Bulletin
Géodésique, Vol. 68, pp. 41-42, 1994.

Contributors are divided in 3 groups:• Presidents Club (cumulative contributions of US $ 1000and more or equivalent in EUR)
• Special contributors (annual contributors of US $ 100… US $ 1000 or equivalent in EUR)
• Contributors (annual contributions of less than US $ 100
or equivalent in EUR)
The rules for the IAG Young Authors Award and for the
IAG Travel Award for young scientists are given in a
separate section of the Geodesist’s Handbook. The
application forms may be found at the IAG Website.

__________________________________________________________________________________________________

I wish to contribute to the IAG fundAnnual basis

One-and-for-all

Title: ………………………………………………………

Amount ………….…… US $, or ...………………. EUR

Name: ……………………………………………………..

Please charge my credit card

Institution/Department: ……………………………………

 Master Card, VISA Card

Card number: ....................................................................

……………………………………………………………..
Address: ……………………………………………………
Country: ……………………………………………………

Expiry date: ....................

Security code: ...................
Phone: ……………………………………………………..

I shall pay by bank transfer to:Bayerische Landesbank München Girozentrale
D 80333 München, Germany
IBAN: DE10 7005 0000 0000 0248 66
SWIFT / BIC: BYLADEMM,
Note to payee: PK 0002.0169.0517, your name

Fax: ………………………………………………………..
E-Mail: ……………………………………………………
Date: ………………………………………………………
Signature:

The Geodesist’s Handbook 2016

944

INTERNATIONAL ASSOCIATION OF GEODESYMembership Application Form
Please complete and send to:www.iag-aig.org
iag.dgfi.tum.de

Prof. Hermann Drewes, IAG Secretary General
Deutsches Geodätisches Forschungsinstitut
Technische Universität München (DGFI-TUM)
Arcisstr. 21, D-80333 München, Germany
Tel.: +49 89 23031 1215, +49 331 288 1978
Fax: +49 89 23032 1240, +49 331 288 1759
E-mail: iag.office@tum.de, fgkugl@gfz-potsdam.de

Personal details
Surname/Last/Family Name

Title (Prof./ Dr./
Ms./ Mr.)First / Other Names

Address(Affiliation,
Street, no.
City, zip
Country)

Date of Birth
dd/mm/yyyy

Phone:
Fax:
E-mail:Class of membership (tick one)
Individual
Individual at reduced fee,□
4 years (US $ 150) □application is submitted separately □Student (annually free)□ University / College certificate submitted separately every year
Retired□ Reduced fee upon request and acceptance only
I represent
I want to pay for
persons; names to be□ Institution name:the institution
a membership ofsent separately
Individual
One year (US $ 50)

IAG Fund (voluntary)
I wish to contribute to the IAG Fund:

Annually□ One-and-for-all □ US $/EUR:

Payment details (tick one)

□ Credit
Card no.:Name ofholder:□ Banktransfer:

Expiry
date:
Card
type:

Security
code:
VISA

MasterEurocard

Bayer. Landesbank München Girozentrale Date and Signature
IBAN: DE10 7005 0000 0000 0248 66
BIC / Swift: BYLADEMM………………………………………………...
Note: PK 0002.0169.0517, name

XXVI IUGG General Assembly 2015

945

The XXVI IUGG General Assembly, Prague, Czech Republic, 2015
IAG Presidential Address
Chris Rizos1

Distinguished Guests and Colleagues,
Ladies and Gentlemen1
It is my pleasure to welcome you to the IAG General
Assembly, held here in Prague on the occasion of the 26th
General Assembly of the International Union of Geodesy
and Geophysics (IUGG). The IAG General Assembly
marks the transition from the current Executive Committee
to the new one. The new Executive Committee was electedby ballot prior to this General Assembly, and details will
be provided later in my report. As outgoing IAG President
my last responsibilities include chairing this Opening
Ceremony. Before I proceed with some highlights of thelast quadrennial period 2011-2015 I wish to thank all
members of the IAG Executive Committee, and the manyother colleagues who make vital contributions to the IAG
Commissions, Services, and other components. Without
your unstinting support and commitment the IAG would bea far poorer organisation, and it would not be able to provide
the knowledge base, and products that now underpin many
endeavours in geoscience, and society in general.
Let us first remind ourselves that the Mission of the IAG
is the advancement of geodesy. The IAG implements its
mission by furthering geodetic theory through research andteaching; by collecting, analysing, modelling andinterpretingobservationaldata;bystimulating
technological development and by providing a consistent
representation of the figure, rotation, and gravity field of
the Earth and planets, and their temporal variations. The
IAG shall pursue the following objectives:□ Chris Rizos <c.rizos@unsw.edu.au>
1

University of New South Wales, School of Civil & Environmental
Engineering, Sydney NSW 2052, Australia

x Study, at the highest possible level of accuracy, allgeodetic problems related to Earth observation andglobal change.
x Maintenance of geodetic reference systems and frames.
x Determination and study of the Earth’s gravity field.
x Monitoring the Earth’s rotation and geodynamics.
x Application of geodetic studies to science and practice.
The IAG is structured into four Commissions, fourteen
Scientific Services, the Global Geodetic Observing System(GGOS), the Communication and Outreach Branch (COB),
and the Inter-Commission Committee on Theory (ICCT).
The Commissions are divided into Sub-commissions,
Projects, Study Groups and Working Groups. The
administration is supervised by the Council, and managed
by the Bureau, the Executive Committee and the Office.
All these IAG components inform our community about
their activities through such means as the IAG Newsletterand the biennial IAG Reports (Travaux de l’AIG).
The IAG Commissions are:x Commission 1: Reference Framesx Commission 2: Gravity Field
x Commission 3: Earth Rotation and Geodynamics
x Commission 4: Positioning and Applications

1 Activities
Commission 1
Over the last quadrennial period Commission 1 organised
several workshops, schools and conferences; conducted
some focused studies; and coordinated reference frame
activities at the regional level. Some highlights are:

Chris Rizos

946

x Organisation of the REFAG2014 Symposium, in
Luxembourg, 12-17 October 2014. Although intended
to coincide with the release of the latest International
Terrestrial Reference Frame ITRF2014, the delay in thecompletion of the computations underpinning the
ITRF2014 meant that the conference covered a broad
range of other global, regional and national reference
frame topics. Tonie van Dam, President of Commission
1, did a tremendous job organising a successful REFAG
symposium. (The REFEAG symposia are one of a seriesof IAG symposia dealing with critical topics of interest
to the IAG, and the wider community.)x One extraordinary event took place on 26 February
2015, when the UN General Assembly adopted theresolution, A Global Geodetic Reference Frame for
Sustainable Development, recognising the increasingrole Geodesy plays in people’s lives, and through its
contributions to the geospatial discipline and to thegeosciences, by provision of the fundamental mapping,geoscience and geospatial datum, and enabling easy
connection to this datum using the GNSS technology
through global services and infrastructure. The Working
Group on the Global Geodetic Reference Frame(GGRF), established by the Committee of Experts of the
UN Global Geospatial Information Management (UNGGIM) initiative, is currently developing a Roadmap on
how to progress the principles described in this UN-GA
resolution.
x Validation of the Global Geophysical Fluids Centre(GGFC) models.
x Regional Reference Frame highlights:– Continuing increase in the number of GNSS
Continuously Operating Reference Stations (CORS)
within the six regional Sub-commissions.
– Upgrade of CORS networks in the European
Permanent Network, and elsewhere, to support multisystem GNSS capability.
– Densification of the ITRF and IGS network is madeby weekly combinations of five regional weekly
solutions using different GNSS processing software.
– Closer alignment of regional reference frame
initiatives with those of the regional sub-groups of
the UN-GGIM.
x Schools and Workshops:– Workshop on Site Surveys and Co-location, Paris,
France, 21-22 May 2013.
Commission 1 was ably led by Tonie van Dam. I thankher, and her Commission Steering Committee for their
hard work in managing the very important topic ofReference Frame definitions and realisations.

Commission 2
Over the last quadrennial period Commission 2 organised alarge number of successful workshops, schools andconferences; conducted some focused studies related toterrestrial and satellite-mapped gravity field parameters;
analysed the products of recent gravity field mapping
missions such as GRACE and GOCE, and coordinatedactivities that culminated in the proposal to establish an
International Height Reference System and Frame. Somehighlights are:x Commission 2 organised another very successful
Gravity, Geoid & Height Systems (GGHS) Symposium,
Venice, Italy, 9-12 October 2012. (The GGHS symposia
are one of a series of IAG symposia dealing with critical
topics of interest to the IAG, and the wider community.)x Project “Geoid in Africa” was one of the association
projects supported by the IUGG.
x Conclusion of an agreement between Geodesy (IAG)and Metrology (CCM) concerning the future of thecomparison of absolute gravimeters at BIPM, Paris.
x Release (5) of the final GOCE geopotential models.
x Many studies on sea level rise, ice melting, hydrologicalprocesses, etc, arising from the analysis of GRACE
monthly solutions were reported at symposia andworkshops.
x A pleasing outcome was the assurance of a GRACE
follow-on mission, scheduled for launch in 2017.
x Progress in defining an International Height Reference
System/Frame, which has led to an IAG resolution.
x Progress in defining a Global Gravity Reference
Network, which has led to an IAG resolution.
x Improved models of the marine gravity field and ocean
topography models from satellite altimetry werereported.
This Commission was ably led by Urs Marti. I thankhim, and his Commission Steering Committee for their
hard work in managing the many facets of Gravity Field
mapping, modelling and services.
Commission 3
Over the last quadrennial period Commission 3 organised anumber of workshops and conferences, these included:
x 17th International Symposium on Earth Tides:
Understand the Earth, Warsaw, Poland, 15-19 April
2013.
x International Symposium on Geodesy for Earthquake
and Natural Hazards, Matsushima, Miyagi, Japan, 2226 July 2014.

IAG Presidential Address

x International Symposium on Reconciling Observations
and Models of Elastic and Viscoelastic Deformation due
to Ice Mass Change, Ilulissat, Greenland, 30 May - 2June 2013.
x 16th General Assembly of WEGENER: Earthquake
Geodesy and Geodynamics: From Giant to Small Scale
Events, Strasbourg, France, 17-20 September 2012.
x 17th General Assembly of WEGENER: Measuring andModeling Our Dynamic Planet, Leeds, United
Kingdom, 1-4 September 2014.
Commission 3 was led by Richard Gross. I thank him,
and his Commission Steering Committee for their hard
work in making the geodesy community aware of the many
exciting advances in studies into Earth Rotation andGeodynamics.
Commission 4
Over the last quadrennial period Commission 3 organisedor participated in a large number of workshops, schools
and conferences. Many of these were jointly organisedwith the IAG’s sister organisations, the FIG (International
Federation of Surveyors), ISPRS (International Society for
Photogrammetry & Remote Sensing), ICA (International
Cartographic Association), U.S. Institute of Navigation,and others. Many of the activities of the Sub-commissionsand Working Groups are related to various aspects of
GNSS precise positioning, and are therefore of a wider
interest than just to the IAG and the IGS. Engineering
Geodesy (deformation monitoring, etc), AtmosphericEffects on GNSS, Techniques of Precise GNSS
Positioning, Geodetic Imaging (radar and lidar), are someof the topics under study. Some highlights are:x Participation at many GNSS conferences, workshops
and sessions, dealing with topics such as Precise Point
Positioning (PPP), Real-Time Kinematic (RTK, andNetwork-RTK), Continuously Operating Reference
Stations (CORS) infrastructure & services, kinematic,
mapping & geodetic applications of GNSS.
x IAG/FIG/ISPRS cooperation in a number of symposia,
field experiments, special journal issues, etc.
x Active participation and co-organisation of theInternational Symposium on UAVs for Geomatics:
UAV-g 2011, Zurich, Switzerland, 14-16 September
2011; UAV-g 2013, Rostock, Germany, 4-6 September
2013.
x 8th International Symposium on Mobile MappingTechnology (MMT), Tainan, Taiwan, 1–2 May 2013.

947

x 2nd Joint International Symposium on Deformation
Monitoring (JISDM), Nottingham, United Kingdom, 911 September 2013.
x Participation in a variety of focused conferences orsessions at larger conferences emphasising “Positioning& Applications”: Location-Based Services, Imaging, Atmospheric Remote Sensing, Engineering Geodesy, and others.
x Schools and Workshops:– GNSS (HK, May 2012, 2014), Mobile Mapping(Taiwan, June 2012, April 2013; Xiamen, April2015), AI in Engineering Geodesy (Munich, Sept2012).
(The MMT, UAV-g and JISDM symposia are several ofa series of IAG symposia dealing with critical topics ofinterest to the IAG, and to the wider geospatial
community.)
Commission 4 was led by Dorota Brzezinska. I thankher, and her Commission Steering Committee for their
hard work in promoting geodetic expertise in the fields of
GNSS, Mobile Mapping/Imaging, and Atmospheric
Remote Sensing, and others, to our sister organisations,and to the wider geospatial community.
Inter-Commission Committee on Theory (ICCT)The mission of the ICCT is to interact actively and directlywith other IAG entities, in particular Commissions and
GGOS, in order to further the objectives of the ICCT:x to be the international focal point of theoretical geodesy,x to encourage and initiate activities to further geodetic
theory in all branches of geodesy, andx to monitor research developments in geodetic modelling.
During the last quadrennial period the highlights were:x Transition of the ICCT to a permanent IAG entity.
x The work of nine Joint Study Groups (with theCommissions).
x Organisation of the Hotine-Marussi Symposium, in
Rome, Italy, 17-21 June 2013 “in honour of FernandoSansò”. (The Hotine-Marussi symposia are one of theimportant IAG symposia dealing with topics of interest
to the IAG.) The Chair of the ICCT was Nico Sneeuw.
Services
In many respects the IAG Services are the “engine room”
of the IAG, and a significant differentiator of the IAG fromits sister associations within the IUGG. There are fourteen
IAG Services, which may be split into three general fields:

Chris Rizos

948

geometry (IERS, IDS, IGS, ILRS, and IVS), gravity(IGFS, ICGEM, IDEMS, IGeS, and BGI), andcombination (IAS, BIPM, ICET, and PSMSL). All of them
maintain their own Homepages and data servers, and havetheir governance structures. Details of their structures,products/services and work programs or priorities for thequadrennial 2011-2015 can be found in the Geodesists’Handbook 2012, and the progress reports 2011-2013 in the
IAG Reports (Travaux de l’AIG). Most of the Services heldinternational meetings, and participated in many symposia.
I would like to thank the Services representatives on the
IAG Executive Committee: Riccardo Barzaghi, Ruth
Neilan, Tom Herring. Some highlights:
x International Earth Rotation & Reference Systems
Service (IERS)– Release of new International Terrestrial Reference
Frame ITRF2014 is imminent (to update and replace
ITRF2008).
x International GNSS Service (IGS):– 20th anniversary IGS Workshop, Pasadena, USA, 2327 June 2014.
– Continued engagement with many stakeholders andagencies, including GGOS, UN-GGIM, and theInternational Committee on GNSS.
x International VLBI Service for Geodesy and Astrometry(IVS):– General Meetings: Madrid, Spain, 2012; Shanghai,
China, 2014.
x International Gravity Field Service (IGFS):– General Assembly, Shanghai, China, 30 June – 6 July2014.
An assessment of the IAG Services is currently
underway to facilitate strategic planning and to facilitate
the improvement of their performance and their products,
so as to better address the stringent requirements of GGOS
2020.
Global Geodetic Observing System (GGOS)The GGOS is IAG’s observing system to monitor thegeodetic and the global geodynamic properties of the Earth
as a system. A new structure was set up during a retreat in2011 and implemented in 2012. It includes a Consortium
composed by representatives of the Commissions andServices, the Coordinating Board as the decision-making
body, the Executive Committee, and the Science Panel.
The scientific work of GGOS is structured by Themes,Working Groups and Bureaus. This new structure will be
described in their separate report. The Chair of GGOS is
Hansjoerg Kutterer. He has been reappointed for the next
quadrennial period 2015-2019.

Coordination with Other Organisations
IAG maintains close cooperation with several
organisations beyond the associations of the IUGG. There
were frequent meetings with the Advisory Board on the
Law of the Sea (ABLOS, together with IHO), Group on
Earth Observation (GEO, with IAG as a participatingorganisation), International Standards Organisation (ISO,TC211 Geographic Information / Geomatics), Joint Boardof Geospatial Information Societies (JBGIS), United
Nations Office for Outer Space Affairs (UN-OOSA), withparticipation in Space-based Information for Disaster
Management and Emergency Response (UN-SPIDER); theInternational Committee on Global Navigation Satellite
Systems (ICG); and the UN-GGIM.

2 Administration
IAG Council
The Council met twice during the IUGG General
Assembly 2011 in Melbourne, Australia, and once at the
IAG Scientific Assembly 2013 in Potsdam, Germany. The
list of national correspondents forming the IAG Council
was regularly updated with the assistance of the IUGG
Secretary General. The Council was informed by email
about activities of the Bureau and the Executive
Committee.
IAG Executive Committee (EC)The EC comprises the IAG President, immediate PastPresident, Vice-President, Secretary General, the fourCommission Presidents, the Chairperson of GGOS, thePresident of the COB, three representatives of the Services,and two members-at-large. Seven EC meetings were held
during the last quadrennial period: Melbourne, Australia,
July 2011; San Francisco, USA, December 2011;
Singapore, August 2012; Vienna, Austria, April 2013;
Potsdam, Germany, September 2013; Vienna, Austria,
April 2014, and San Francisco, USA, December 2014. The
meeting summaries were published in the IAG Newsletterand are available online at the IAG Homepage(http://www.iag-aig.org) and in the IAG Office Homepage(http://iag.dgfi.tum.de). The EC meetings to be held at thisIAG General Assembly will be the last for the current EC.
Main agenda items at the EC meetings were the regular
reports of the Commissions, Services, GGOS, ICCT, COB,
the Editor-in-Chief of the Journal of Geodesy, and the
Editor of the IAG Symposia Series. They were typicallyfollowed by discussion on specific scientific issues,

IAG Presidential Addresschanges in the structures of GGOS and Services, and IAG
publications. Other important topics were the IAG
Scientific Assembly 2013, the preparation of the IAG
Symposia for the IUGG General Assembly 2015, thebiennial IAG Reports (Travaux de l’AIG), sponsoring of
symposia, and reports on engagement with other organisations,e.g. FIG, GEO, JBGIS, IHO, ISO, and UNOOSA.
IAG Bureau
The IAG Bureau, consisting of the President, the VicePresident and the Secretary General, held monthly
teleconferences and met regularly before each EC face-toface meeting. The President and Secretary Generalparticipated in the IUGG Executive Committee meetings.
The Bureau members represented the IAG at international
scientific meetings, and at several anniversaries, as listed
below under Awards, Anniversaries, and Obituaries.
IAG Office
The IAG Office assists the Secretary General, responsible
for administration of all IAG business, meetings andevents, including the budget management, the record
keeping of the individual IAG membership, and the
preparation and documentation of all Council and EC
meetings, with detailed minutes for the EC members andmeeting summaries published in the IAG Newsletters andat the IAG Homepage. Important activities were thepreparation and execution of the IAG Scientific Assembly2013 together with the celebration of the 150th IAG
anniversary and the IAG symposia of the IUGG General
Assembly 2015. An important task was the publication of
the Geodesist’s Handbook 2012, providing an organisationalguide to the IAG, with a complete description of the IAG
structure (and reports, terms of reference, documents, etc);
and of the Mid-Term Reports 2011–2013 (Travaux del’AIG Vol. 38). Travel grants for young scientists toparticipate at IAG sponsored symposia were administered.
Communication and Outreach Branch (COB)
The task of the COB includes maintenance of the IAG
Homepage and publishing the monthly online Newsletter,and news items in the Journal of Geodesy. The COB also
keeps track of all IAG-related events in the Meetings
Calendar. The IAG Newsletter is sent to all IAG officers,
individual members, the Presidents and Secretaries Generalof the IUGG Associations and liaison bodies. The COB
designed, printed and distributed a new IAG leaflet and acomprehensive IAG brochure, and participated in the
preparation of the Geodesist’s Handbook 2012.

949

Awards, Anniversaries, Obituaries
The following medals and prizes have been awarded
during the past quadrennial period:x Levallois Medal to Ruth Neilan, USA (2011)x Bomford Prize to Johannes Boehm, Austria (2011)x Young Author Award to Elizabeth Petrie, UK (2011)x Young Author Award to Thomas Artz, Germany (2013)x Young Author Award to Manuela Seitz, Germany (2013)
In addition, 53 Travel Awards were given to young
scientists for participation at 15 IAG sponsored symposia.
The following anniversaries were celebrated with IAG
participation:
x 150th anniversary of the Swiss Geodetic Commission,
Zurich, Switzerland, 10 June 2011x 150th anniversary of the Arc Measurement in the
Saxony, Dresden, Germany, 1 June 2012
x 150th anniversary of the Central European Arc
Measurement, Vienna Austria, 14 September 2012
x 150th anniversary of the Austrian Geodetic Commission,
Vienna, Austria, 7 November 2013
Obituaries were written for former IAG officers andoutstanding geodesists who passed away:
x 2011: A. Bjerhammar, Sweden; I. Fejes; Hungary;
A. Finkelstein, Russia, S. Henriksen, USA.
x 2012: K.-P. Schwarz, Canada.
x 2014: C.C. Tscherning, Denmark; E. Kejlso, Denmark.
x 2015: B.E. Schutz, USA

3 Concluding Remarks
Shortly after becoming President of the IAG on the 6th July
2011, I mused on what Geodesy “is” and how to explain
this arcane field. During my period as IAG President I
returned over and over again to this challenge. I have to
explain not just what Geodesy is, but what its contribution
to today’s “Grand Challenges” is. I did this in several news
articles, and in keynote presentations at several
international symposia. In order to define what Geodesy“is”, it is necessary to articulate what Geodesy is “not”.
I can remember I had a disturbing “eureka” moment in2010. I had given a talk to an audience of surveyors on thetheme “why Geodesy has a bad name”. I noted that theclassical topics of Geodesy were no longer taught in many
university surveying/geomatics programs. I rattled off the
topics, which resonated with the audience. As I listed
them, many members of the audience nodded their heads…
geodetic control networks, atmospheric refraction,
spherical harmonic models, geodetic boundary value

950

problem, deflections of the vertical, gravity anomalies andgravimetry,
least-squares
estimation,
ellipsoidal
computations, map projections, reference frametransformations, positional astronomy, and so on. What I
had not appreciated until that moment was that all thesewere “hard” topics that few surveyors had fond memoriesof these subjects, and fewer would say they were better off
by having studied them. Yet Modern Geodesy has
progressed in the last decades in leaps and bounds.
A second revelation came to me also in 2010 as I
participated in the centenary celebrations of the foundingof the International Society of Photogrammetry & Remote
Sensing (ISPRS) in Vienna by Eduard Dalezal. (The IAG
and the ISPRS are two of the ten sister organisations
making up the Joint Board of Geospatial Information
Societies – JBGIS.) Speakers at the ISPRS 100 year
anniversary conference celebrated the history ofphotogrammetry and remote sensing, but also enthused
about the future of satellite technologies in helping address
society’s environmental challenges. I sat there and thought,“that is what Modern Geodesy also seeks to do!” The goalof Modern Geodesy is nothing less than to monitorchanges in a range of physical processes in the solid Earth,
the atmosphere, and the oceans in order to improve ourunderstanding of this fragile, precious and stressed planet.
It was clear to me that Geodesy could be described as an
Earth Observation (EO) discipline, or science. Certainly
the classical definition of Geodesy does not make clear that
it is an EO science which has broader functions andapplications, and potentially more relevance, than just as afoundation for mapping and surveying.
So what sets Geodesy (and the IAG) apart from other
EO disciplines? It is the fact that the IAG has fostered theestablishment of Services to provide fundamental products
for many geoscientific and geospatial end-users. No otherIUGG or JBGIS organisation supports the number andrange of Services that the IAG does. As IAG President I
have been especially proud to acknowledge the importantwork of these services. The Services dealing with space(geometric) geodesy techniques include the International
VLBI Service (IVS), the International Laser Ranging
Service (ILRS), the International DORIS Service (IDS)
and the best known, the International GNSS Service (IGS).
The latter I knew very well, having been a member of its
Governing Board since 2004.
Through another IAG service – the International Earth
Rotation & Reference Systems Service (IERS) – thesespace geodetic techniques play a critical role in defining
the fundamental reference frame in relation to whichchanges in the location of points on (or above) the Earth’s
surface (including satellite orbits), or the shape of the land,or level of the ocean surface, can be monitored over many

Chris Rizos

years to sub-centimetre accuracy. Therefore special
mention should be made of one of the IAG’s “flagship”
products – the International Terrestrial Reference Frame(ITRF) – which also increasingly is the basis for modern
national mapping datums. I am pleased that ITRF2014 issoon to be released. This IAG product together with the
GNSS products of the IGS have raised the visibility of the
IAG across the geoscience community, and beyond.
The IAG also established the International Gravity Field
Service (IGFS) to measure and model the Earth’s gravity
field to high accuracy using, for example, sophisticatedgravity mapping satellite missions such as CHAMP,GRACE and GOCE. Gravimetric Geodesy can nowadays
measure changes in gravity acceleration arising from masstransport (which changes gravity by tiny amounts) due tothe global water cycle, atmospheric and ocean circulation,and solid earth processes such as volcanism and tectonics.
All of the IAG Services generate products on acontinuous basis. These products may be the primary
outputs of geodetic analysis, such as precise coordinates of
GNSS monitor stations, or global meteorological values ofhumidity, temperature and pressure, or maps ofionospheric disturbances, rate of rotation of the Earth,orientation of its rotation axis, and many others. Suchproducts can be used directly by many scientists. In
addition, indirect products such as the reference frame,
precise orbits of EO satellites, precise timing scales andhigh-accuracy GNSS-enabled navigation capability,
support many other scientific and professional users. The
IAG has commenced a „services assessment exercise“, but
unfortunately it has not yet been concluded. The goal is toraise the quality and consistency of all geodetic products to
support the Global Geodetic Observing System (GGOS).
During this past quadrennial we celebrated a verysignificant anniversary. The story is well known, but isworth repeating here. At the invitation of the Prussian
General Johann Jacob Baeyer, representatives of the statesof Prussia, Austria and Saxony met from 24th to 26th April
1862 in Berlin to discuss Baeyer’s “Proposal for a Central
European Arc Measurement”. By the end of 1862, 16
nation states had agreed to participate in the project:
Austria, Belgium, Denmark, France, seven German states(Baden, Bavaria, Hannover, Mecklenburg, Prussia,
Saxony, Saxe-Gotha), Italy, The Netherlands, Poland,
Sweden, Norway and Switzerland. The IAG counts thisinternational scientific initiative, and the organisation it
spawned, as its origin. Note that the primary motivation
was to encourage national cooperation for a practicalgeodetic project, with the outcome being improved
reference frame and geoid knowledge to support continentwide mapping. Of course there were important sciencechallenges that also had to be addressed, and hence from

IAG Presidential Address

the very beginning the IAG has fostered both operational
geodetic practice as well as basic research. This dual
function continues to drive Modern Geodesy.
In October 1864, the first “General Conference of theRepresentatives to the Central European Arc
Measurement” took place in Berlin. The organisational
structure was agreed upon and a research program wasdeveloped. The IAG considers this conference as its first
General Assembly. Baeyer was appointed Director of theCentral Bureau and Peter Andreas Hansen appointed
President of the Permanent Commission. The projectextended rapidly to other European states and consequently
the name of the organisation was changed in 1867 to“Europäische Gradmessung”, and in 1886 to“Internationale Erdmessung” (“Association Internationalede Géodésie”) with additional member states Argentina,
Chile, Japan, Mexico, and USA.
Baeyer died in 1885, and under his successor, Friedrich
Robert Helmert, the Central Bureau moved from Berlin to
Potsdam, together with the Geodetic Institute. Against all
odds the IAG survived two World Wars, evolving in theprocess to focus more on the science of geodesy, becoming
part of the International Union of Geodesy and Geophysics(IUGG) after that organisation’s establishment in 1919. In
1932 the name “International Association of Geodesy” wasadopted. I was fortunate to be IAG President during thiscelebration, but acknowledge that I “stood on the shouldersof giants” (nanos gigantum humeris insidentes), a
statement attributed to Isaac Newton, and most recently the
motto of Google Scholar!
There are a number of reasons why Geodesy has in acomparatively short time transformed from an esotericgeoscience to valued geospatial discipline. Firstly, Modern
Geodesy relies on space technology, and enormous strides
have been made in accuracy, resolution and coverage due
to advances in satellite sensors and an expanding portfolioof satellite missions. Secondly, Geodesy can measure Earth
System parameters that no other remote sensing techniquecan, such as the position and velocity of points on thesurface of the Earth, changes of sea level and the shape of
the Earth’s ocean, ice and land surfaces, and map the
spatial and temporal features of the gravity field. Thesegeodetic parameters are in effect the “fingerprints” ofmany dynamic Earth phenomena, including those that we
now associate with global change (due to anthropogenic or

951

natural causes) as well as responsible for devastating
events such as earthquakes, tsunamis and volcanoes. The
challenge is to invert the outward expressions of these
dynamic Earth processes in order to measure and monitor
over time the underlying physical causes. Finally what
relentlessly drives geodesy into the future is the innovativeuse of signals transmitted by Global Navigation Satellite
Systems (GNSS) such as the U.S.’s GPS and Russia’s
GLONASS, E.U.’s Galileo, and China’s BeiDou – thelatter two constellations currently being deployed and will
be fully operational by the end of this decade.
However, GNSS is more than just another space
geodetic technology. GNSS is today used for an enormous
range of applications, from consumer uses such as for car
navigation and in mobile phones to access location-based
services, to professional applications such as machine
automation (guidance of farm, mining and construction
vehicles), emergency services, military operations, rapid
mapping, surveying, transport management, and many
more. However it is the special ultra-high accuracy form
that is of geodetic interest. The IGS therefore deserves
special mention. The IGS was established in 1994 as thefirst of the IAG’s geometric services, primarily bycomputing high accuracy GPS and GLONASS satellite
orbit and clock data products, as well as open (and free)access to measurements made by a global ground networkof continuously operating GNSS tracking stations. Thesehundreds of GNSS receivers on stable pillars or solidmonuments operate continuously around the world alsofunction as precise monitoring systems for groundmovement due to global effects such as continental drift,
local subsidence due to fluid extraction or undergroundmining, uplift due to volcanism or post-glacial rebound,and more. In 2014 the IGS celebrated its 20 year
anniversary, and I was proud to participate in its celebration.
In summary, Geodesy is facing an increasing demand
from Science, Engineering Applications, the Earth
Observation community, and society at large for improved
accuracy, reliability and access to geodetic services,
measurements and products. My catch phrase as I stepped
up four years ago to take on the presidency of the IAG stillholds true “geodesy matters, now more than ever”. I am
proud to have served the IAG, in a number of capacities
over the last 20 years. I hope to continue to do so in the
coming years.

952

Chris Rizos

Fig. 1 IAG Presidents G. Beutler (2003-2007), W. Torge (1991-1995), I.I. Mueller (1987-1991), Ch. Rizos (2011-2015), M.
Sideris (2007-2011); and Secretaries General H. Drewes (2007-…) and C. Boucher (1991-1995) at the IAG Scientific Assembly,
Potsdam, Germany, 1-6 September 2013

Levallois Medal Laudation

953

Levallois Medal Laudation for Reiner Rummel
Sakis Dermanis1, Gerhard Beutler2 and Michael Sideris3

The Levallois Medal was established in 1979 to honor
Jean-Jacques Levallois for his long service from 1960 to1975 as Secretary General of the International Associationof Geodesy (IAG). It is usually awarded every four years at
the IAG General Assemblies, and is presented “inrecognition of distinguished service to the association
and/or to the science of geodesy in general”. 123

Fig. 1 Handover of the Levallois Medal to Reiner Rummel(left) by the IAG President, Chris Rizos (right)
A committee of six past Presidents of the IAG (Gerhard
Beutler, Helmut Moritz, Ivan Mueller, Fernando Sanso,
Michael Sideris and Wolfgang Torge) recommended
unanimously to award the Medal at the 2015 General
Assembly in Prague to Reiner Rummel for his distinguished1

Aristotle University, Dept. Geodesy & Surveying, University Box 503,
54124 Thessaloniki, Greece
2
University of Bern, Astronomical Institute, Sidlerstrasse 5, CH-3012
Bern, Switzerland
3
University of Calgary, Department of Geomatics Engineering, 2500
University Drive N.W., Calgary Alberta T2N 1N4, Canada

service to the IAG and the science of geodesy in general,and in particular for his decisive role in the development ofsatellite gradiometry and the realization of the Gravity field andsteady-state Ocean Circulation Explorer (GOCE) mission.
Right after his PhD degree in 1974, Reiner was invited
as a post-doctoral researcher to the Department of
Geodetic Science at the Ohio State University, where he
had the chance to collaborate with distinguished colleagues
and formulate his geodetic profile as an amalgam ofEuropean geodetic theory and US geodetic practice, as the
now established space geodetic techniques were justcoming into blossom at that time.
After a period of work as a researcher in Munich, firstwith the German Geodetic Research Institute and then with
the Geodetic Commission of the Bavarian Academy of
Sciences and Humanities, he was appointed Professor ofphysical geodesy at the Delft University of Technology,
where he served for 13 very fruitful years. In 1993, he wasappointed Professor and Head of the well-known Instituteof Physical and Astronomical Geodesy at the Technical
University of Munich, where he served until his retirementin 2011. Since his retirement, he is a Professor Emeritus at
the same University and a Carl von Linde Senior Fellow of
the Institute of Advanced Study. It was during his 18 years
at the Technical University of Munich that Reiner Rummel
made his greatest contributions as both an academic
teacher and a pioneering researcher.
Reiner’s role in science is that of a visionary, whose ideas
and originality greatly contributed to the status of contemporary
geodesy. Among his many contributions, three should bepointed out that had the greatest impact on the geodetic
community: his central role in the restructuring/modernizationof the IAG, his protagonistic role in the realization of the
GOCE satellite gradiometry mission, and his role as an initiatorof the IAG’s Global Geodetic Observing System (GGOS).

954

As President of IAG’s Section II “Space Geodesy” in
1995-1999, Reiner was instrumental in initiating theprocess of restructuring the International Association of
Geodesy. With the development of modern IAG Services
like the IERS (International Earth Rotation and Reference
System Service) and the IGS (International GNSS Service)
it became clear that IAG had to take advantage of thesepromising initiatives in order to reform its structure, which
was going back to the 1960s. Starting with an IAG Section
II Symposium in Munich devoted to the restructuring of
the IAG, a review was actually performed in the period
1999-2003. The new structure was accepted at the 2001
IAG Scientific Assembly in Budapest, and was finallyrealized at the 2003 Sapporo General Assembly.
The Global Geodetic Observing System (GGOS),
originally labeled IGGOS (Integrated Global Geodetic
Observing System) by Reiner Rummel, is devoted to themonitoring of the system Earth by geodetic methods andcomprises the entire geodetic infrastructure – terrestrial
and space, including satellite missions. The GGOS concept
is scientifically based on Reiner’s concept of the threepillars of geodesy, namely the (geometric) Earth’s shape,
the Earth’s gravity field, and Earth’s rotation, intersecting
into the concept of reference systems. The GGOS concept
is ambitious, its realization a major challenge, which,although already quite advanced, has not reached its
pinnacle yet. Nevertheless, the original idea and the “granddesign” are due to Reiner Rummel.
It has been a major undertaking to convince the space
agencies of the necessity to realize dedicated gravity field
missions. In retrospect, it is close to a miracle that three
dedicated gravity field missions, namely CHAMP,GRACE, and GOCE, were launched into orbit in the first
decade of our century. We would estimate that Reiner
Rummel probably devoted more than ten years of his
career to the development and realization of what is now
known as the European Space Agency’s Gravity field andsteady-state Ocean Circulation Explorer (GOCE) mission.
Reiner’s most important contribution was to lead European
geodesists to develop a consistent mission concept – a
typical geodetic approach, which in essence measures (thesecond derivatives of) the gravitational potential in situ.
Reiner Rummel was the Principal Investigator of the
GOCE Mission and the Coordinator of the GOCE HPF(High-level Processing Facility) of ten European
institutions collaborating to provide the official GOCE
products and to scientifically exploit the applications
enabled by GOCE, such as, for example, the Unification of
Height Systems.

S. Dermanis, G. Beutler, M. Sideris

As it can be seen in his more than 170 publications,
Reiner maintained through his research career, and despite
his devotion to gravity gradiometry, a vivid interest in awide spectrum of topics ranging from the purely
theoretical to the more application oriented ones, coveringboth geometric and gravimetric aspects of geodesy. Hisview of geodesy as an interdisciplinary branch of science
promoted the idea of seeking collaboration with othergeoscientists – from oceanographers to seismologists toatmosphere physicists.
Reiner Rummel has been an outstanding teacher. His
natural gift of lecturing helps him inspire his audience withstimulating and at times unconventional presentations. His
initiative and ideas led to the formulation of the ESPACE
Master Curriculum at TU Munich providing fundamental
knowledge in space engineering and satellite applications
related to navigation, remote sensing, and Earth systemscience. His students simply admired and adored him.
Many of his Doctoral and Habilitation students hold highacademic positions in Germany and worldwide.
His list of services to the academic community is toolong to be mentioned here. They are best mirrored in his
many medals and awards in recognition of his academic
and research excellence, which include the Heiskanen
Award of the Ohio State University (1977), the Vening
Meinesz Medal of the European Geophysical Society(1998), and the Bavarian Order of Sciences and Arts
(Maximiliansorden) (2010). He is a member of the Royal
Netherlands Academy of Sciences (1989), the Bavarian
Academy of Sciences (1997), an honorary member of the
Hungarian Academy of Sciences (2001), of the Deutsche
Akademie der Naturforscher Leopoldina (2004) and theLeibniz Sozietät Berlin (2008). He has been awarded the
Honorary Doctor Degrees from the Technical University ofGraz (2005), the University of Bonn (2005), the Ohio State
University (2013) and the Aristotle University ofThessaloniki (2014).
In summary, it is appropriate to state that Reiner Rummel is
one of few outstanding geodesists of the 20th – and 21st –century. His impact on geodesy, geodynamics, and on
Earth sciences in general can hardly be overestimated.
He is happily married to Renate, a father of two children,
Benno and Veronika, and a proud grandfather of four.
Finally, beyond his scientific contributions, a word mustbe said about the person Reiner Rummel. He has a pleasantpersonality and a mild, lovable character. Colleagues,
collaborators and former students alike have found in
Reiner a caring mentor and dear colleague. It has been ourpleasure and honour to write this citation for Reiner
Rummel – an outstanding geodesist and a dear friend.

Guy Bomford Prize Lecture955

Guy Bomford Prize Lecture
Physical modeling of gravity field variations to explore mechanisms ofgreat earthquakes
Yoshiyuki Tanaka1

GNSSs1 have detected postseismic crustal deformations
due to megathrust earthquakes that occur in island-arc
trench systems. Such crustal deformation data have beeninterpreted by combining three mechanisms: afterslip,
poroelastic rebound and viscoelastic relaxation. It is
seismologically important to determine the contribution ofeach mechanism because it provides frictional properties
between the plate boundaries and viscosity estimates in theasthenosphere which are necessary to evaluate the stressbehavior during earthquake cycles. However, theobservation sites of GNSSs are mostly deployed over landand can detect only a small part of the large-scale
deformation, which precludes a clear separation of themechanisms. To extend the spatial coverage of thedeformation area, recent studies started to use satellite
gravity data obtained by GRACE and GOCE that can
detect long-wavelength deformations over the ocean.
To make the best use of the gravity data, a theory on
global deformation is required, which treats the selfgravitation effect rigorously. The governing equations for aself-gravitating viscoelastic sphere were already given by
Peltier (1974) to model postglacial rebounds. The same
framework has been applied to postseismic relaxation.
However, those governing equations has been solved only
for special cases such as the incompressible case (thedivergence of the displacement field is zero) until recently,
due to some mathematical difficulties.
A first difficulty is that denumerable infinite sets ofeigenmodes appear in the compressible case. The
conventional root-finding procedure in the Laplace domain
encounters technical difficulties for identifying thesemodes. To avoid this, Tanaka et al. (2006) evaluated thesum of the contributions from these modes by applying the1

Earthquake Research Institute, the University of Tokyo,
Tokyo, Japan

numerical inverse Laplace integration to a radiallystratified viscoelastic earth with many layers. Later,
Cambiotti et al. (2011) and Tanaka et al. (2015) solved thesame governing equations using a modal and a timedomain approach, respectively. Theoretical studies showthat the effects of compressibility exceed 10% with respect
to the incompressible case.
A second difficulty is the presence of unstable modes.
The unstable modes for realistic earth models like PREM
have geological time scales, so in practice they contributeonly to the coseismic elastic deformation. If excludingthese modes, the computed coseismic deformation
disagrees with the result obtained by an elasticity
dislocation theory (Sun & Okubo, 1993). A fundamental
solution to this problem could be obtained by considering
higher-order terms omitted in the governing equations ormodifying the initial state of the earth model, which needs
further studies.
To include 3-D viscoelastic structures is also importantwhen modeling postseismic deformations by megathrust
events (Pollitz et al. 2008). Most spherical models do notconsider strong lateral heterogeneities in mantle viscosity,in particular due to a subducting slab. Ordinary finiteelement methods can consider such effects. However, theself-gravitation effect is often treated only approximately
because the model domain does not cover the whole earth.
Tanaka et al. (2015) developed a spectral finite-element
approach that allows 3-D viscosity distributions and theself-gravitation effect to be considered in a more natural
way without approximating the governing equations of
Peltier. In this approach, much larger lateral viscosity
variations can be handled than by perturbation techniques
to compute global deformations.
The developed approach was applied to the postseismic
deformation of the 2004 Sumatra–Andaman earthquake.

Y. Tanaka

956

The spatial patterns of gravity change generated by theabove three mechanisms clearly differ from one another. A
comparison with the satellite gravity data revealed thatboth afterslip and viscoelastic relaxation were occurring.
Recent new satellite gravity data may also be able to identify
the effects of the slab on postseismic relaxation, which
could exceed 20% of the coseismic change in some cases.
Recent seismological studies indicate that non-tidal
decadal variations in the ocean bottom pressure with only
100 Pa could modify a long-term triggering probability of
non-volcanic tremors, when combined with rapid tidal
stress changes (Tanaka et al., EPS, 2015). Tremors can betriggered by much smaller stress changes due to the low
effective normal stress than ordinary earthquakes.
Moreover, the non-linear frictional law amplifies thesuperimposed tidal effects in periods with low OBPs. Thismeans that plate subduction speeds can slowly fluctuate in
the transition zone as a result of the interaction between theocean and the plate interface. To explore this phenomenon,
future satellite gravity missions are expected to monitor
ocean bottom pressures in coastal areas near the plateboundaries more precisely. Global geodesy which views
surface fluids and the solid earth as a system may play amore and more important role, also in studying interseismic deformation.

Okubo for giving me a good theme when I was a master’s
student. The subsequent, more advanced research was
carried out when I was visiting the GFZ Potsdam, fundedby the Ministry of Education, Culture, Sports, Science andTechnology of Japan. The collaborative work there wasvery successful and I appreciate especially Detlef Wolf,Zdeněk Martinec, Volker Klemann, Maik Thomas andVeronika Söllner. Without their hospitality andcooperation, this work was never completed. I thank manycolleagues in the GFZ and the GSI of Japan for supporting
my research. I also thank colleagues in the ERI and Dr.
Satoshi Ide at the Univ. Tokyo for collaborative work. The
research was supported by the Grant-in-Aid for Scientific
Research, Japan Society for the Promotion of Science(20840012).

Acknowledgements
It is a great honor to receive the 2015 Guy Bomford Prize.
I would like to express my sincere gratitude to the Science
Council of Japan and the IAG for nominating andawarding me with this wonderful prize. I thank Dr. Shuhei

Yoshiyuki Tanaka

Young Authors Award 2013957

Young Authors Award 2013
Citation for Krzysztof SośnicaThe IAG Young Authors
Award 2013 is presented
to Krzysztof Jakub Sośnica
for his paper “Impact ofloading displacements on
SLR-derived parameters
and on the consistency
between GNSS and SLR
results” written together
with the co-authors andadvisors Daniela Thaller,
Rolf Dach, Adrian Jäggi,Krzysztof Jakub Sośnica
and Gerhard Beutler.
The work was published in the Journal of Geodesy,
2013, Volume 87, Issue 8, pp. 751-769. The article studies
the impact of Ocean Tidal Loading (OTL), AtmosphericTidal Loading (ATL), and Atmospheric Non-Tidal
Loading (ANTL) on 12 years of Satellite Laser Ranging(SLR) data.
The international scientific community currently
recommends applying OTL and ATL corrections at theobservation level for IERS products, but not the ANTL
corrections. The article shows, however, that theapplication of ANTL on the observation level does not
only positively impact the long-term stability of theestimated station coordinates, but the quality of Earth
Rotation Parameters, satellite orbits, and geocenter
coordinates, as well.
ANTL corrections play in particular a crucial role in the
combination of optical (SLR) and microwave (GNSS,VLBI, DORIS) observations because of the so-called BlueSky effect: SLR measurements require a cloudless sky,typically associated with high air pressure, which deforms

the Earth's crust. Microwave observations, on the other
hand, are weather-independent and therefore continuously
available. The omission of ANTL corrections in theanalysis of space geodetic data therefore leads toinconsistencies between SLR and GNSS solutions, up to
2.5 mm for inland stations. The application of ANTL
corrections on the observation level does not only improve
the stability of SLR solutions, but reduces thediscrepancies between GNSS and SLR solutions due to theBlue-Sky effect, as well, which is confirmed by about 10%
improvement of the estimated GNSS-SLR coordinate
differences with respect to local tie vectors measured on
ground at the co-located GNSS-SLR sites. These results
indicate how to further improve the consistency between
different space geodetic techniques. They are important in
the context of GGOS, striving for a 1 mm accuracy and a
0.1 mm/y stability for the next generation of terrestrialreference frames.
Krzysztof Sośnica studied geodesy at the Wroclaw
University of Environmental and Life Sciences from 2004
to 2009, when he graduated with a thesis on filtering
airborne laser scanning data with wavelet algorithms. After
additional IT studies in Wroclaw he joined the satellite
geodesy research group at the Astronomical Institute of the
University of Bern (AIUB). His research was devoted tothe analysis of SLR data with the focus on Earth Rotation
Parameters, on temporal variations of the Earth’s gravity
field, and on the improvement of the terrestrial reference
frame. In 2014 he completed his work in Bern with a Ph.D.
thesis entitled “Determination of Precise Satellite Orbits
and Geodetic Parameters using Satellite Laser Ranging”.
After one year as a research associate at the AIUB he
returned to Wroclaw University in spring 2015.

Young Authors Award 2014958

Young Authors Award 2014
Citation for Alvaro Santamaría Gómez

The
awardee,
AlvaroSantamaría-Gómez, took his
first steps in geodesy during
his undergraduate degree inland surveying at the Universityof Salamanca in 2002 and thenduring his graduate degree in
geodesy at the Technical
University of Madrid in 2005.
In 2006 he joined the geodetic
Alvaro Santamaría Gómez department at the National
Geographic Institute of Spainand in 2007 he started his PhD studies at the Geodesy
Research Laboratory of the National Geographic Instituteof France. His PhD research focused on the correction ofvertical land motion in tide gauge records using GPS
velocities. In 2012, while working on the awarded paper,
he obtained a Marie Curie International Outgoing
Fellowship at the University of La Rochelle and the
University of Tasmania. The objective of his present
research is to advance in the understanding of vertical landmotion errors and its impact on sea level change estimatesfrom tide gauges and satellite altimetry.
The award-winning paper presents an improvement of
the method to estimate linear trends of vertical land motion(VLM) at tide gauges using mean sea level observations.
Former methods were based on differences between pairsof tide gauge records or differences between a tide gauge
record and its corresponding nearby satellite altimetry
record. The improved method in this paper is based on
double differences between pairs of tide gauge records andtheir corresponding nearby pairs of satellite altimetry
records. The estimated relative VLM trend between
redundant (multiple inter-connected) pairs of tide gauges isthen adjusted while taking into account their spatial
correlation. The VLM trend at each tide gauge is finallyobtained by adjusting the origin or datum of the relative
VLM estimates using vertical velocities from GPS stations
co-located near some of the inter-connected tide gauges.
One of the main advantages of this method is that thegeocentric VLM of many inter-connected tide gauges canbe estimated from a lower number of co-located GPS
stations, i.e. more than one tide gauge per co-located GPS
station. When redundant (multiple) GPS velocities areavailable their relative vertical velocities can be comparedagainst the double-differenced results, resulting in an
independent method to assess the quality of GPS verticalvelocities to determine the VLM at the tide gauges.
Furthermore, by using differences between pairs ofaltimetry records, the impact of relative geocentric sealevel trends between pairs of tide gauges is reduced while
also reducing the spatially-correlated trend errors arisingfrom altimeter bias drift, satellite orbits or sea-surfacepressure. More than a thousand tide gauges wereconsidered in the paper. However, due to the shortness ofthe satellite altimetry records, only pairs of tide gauge andsatellite altimetry having an extremely high spatial
correlation were used, which reduced the number of tidegauges used to 86. With the extension of the satellite
altimetry data span in the future, the correlation threshold
can be loosened resulting in more pairs of inter-connectedtide gauges being included in the double differences. The
estimated VLM at the tide gauges has a mean formal
uncertainty of 0.7 mm/yr including the uncertainty ofadjusting the datum of the relative VLM using sparse GPS
velocities. With a larger number of tide gauge pairs and colocated GPS velocities, this uncertainty could besubstantially reduced.

Report of the IAG Secretary General

959

Report of the IAG Secretary General
Hermann Drewes

The duties of the IAG Secretary General are (Bylaw 36):(a) Serve as secretary of the General Assembly, the
Scientific Assembly, the Council, the Executive
Committee, and the Bureau; arrange for meetings ofthese bodies, distribute promptly the agenda andprepare and distribute the minutes of all their meetings;(b) Act as Director of the IAG Office;(c) Manage the Association affairs including finances,attend to correspondence, and preserve the records;(d) Circulate all appropriate information related to the
Association;(e) Prepare the reports of the Association’s activities;(f) Perform such other duties as may be assigned by the
Bureau.
At each IAG General Assembly, the Secretary Generalshall present a detailed report on the administrative workand on the finances of the Association (Bylaw 25) to be
published in the Geodesist’s Handbook (Bylaw 19).
The Secretary General is assisted by the IAG Office inthe administration of all IAG business affairs including theorganization of General and Scientific Assemblies, record
keeping of the Council, EC and Bureau meetings,
individual IAG membership, and the budget management.

1 Administrative work
Most important activities in the period 2011-2015 were thepreparation and execution of the IAG Scientific Assembly2013 and the IAG part of the IUGG General Assembly
2015, the edition of the Geodesist’s Handbook 2012, andthe IAG Reports 2011–2013 and 2011-2015 (Travaux del’AIG Vol. 38 and Vol. 39). The accountings of the Journalof Geodesy and the IAG Symposia Series, both publishedby Springer, were supervised. 53 travel awards for young
scientists to participate in IAG sponsored symposia, and 35
IAG / IUGG awards for participation in the General
Assembly 2015 were handled.
1.1 Scientific Assembly
The IAG Scientific Assembly was organised in Potsdam,
Germany, 2-6 September 2013 celebrating concurrently
IAG’s 150th anniversary. The complete assembly report ispublished at http://iag.dgfi.tum.de/index.php?id=304 and asummary in the IAG Newsletter, December 2013. A totalof 538 attendees from 47 countries registered, 241 lecturesand 234 posters were presented. The Young Authors
Awards were granted for the best publications in the
Journal of Geodesy to Thomas Artz (2011) and Manuela
Seitz (2012). Each three awards were granted to the best
young authors lectures and posters. 8 travel awards were
given to young scientists. The symposium proceedings
were published in the IAG Symposia Series, Vol. 143.
1.2 General Assembly
The IAG General Assembly was held customarily together
with the IUGG General Assembly in Prague, Czech
Republic, 22 June – 2 July, 2015. The complete report may
be found at http://www.iugg.org/assemblies/2015prague/, asummary of the IAG assembly is published in the IAG
Newsletter, August 2015. The IAG organised 1 Union
Symposium, 3 Joint Symposia with other Associations, and
8 IAG Symposia. 10 Union Symposia and 10 Joint
Symposia were co-sponsored by IAG, and 1 Union lecture
was given by the IAG Vice President Harald Schuh. 534 of
the total of 4231 participants from 87 countries registeredfor IAG, presenting 545 lectures or posters in the IAG

H. Drewes

960

Symposia and 65 in the Joint Symposia. 35 travel awards
were granted and 42 registration fees were waived for IAG
participants from the IUGG and IAG budget. The IAG
Levallois Medal, Guy Bomford Prize, and Young Authors
Awards were granted (see reports in this Handbook).
1.3 Council
The IAG Council is responsible for governance, strategic
policy and direction. It consists of the delegates appointed
by the Adhering Bodies of the IUGG member countries.
The Council meetings at the IUGG General Assemblies
2011 (Melbourne, Australia) and 2015 (Prague, Czech
Republic), and at the Scientific Assembly 2013 (Potsdam,
Germany) were prepared and minutes were published. The
national delegates’ list was regularly updated, and they
were informed by e-mail about the IAG activities.
1.4 IAG Executive Committee (EC)The Executive Committee guides the Association withregard to the achievement of its scientific objectives. The 8
EC meetings during the legislative period 2011 to 2015
(Melbourne, Australia, July 2011; San Francisco, USA,
December 2011; Singapore, August 2012; Vienna, Austria,
April 2013; Potsdam, Germany, September 2013; Vienna,
Austria, April 2014; San Francisco, USA, December 2014;
and Prague, Czech Republic, June 2015) were prepared,
minutes were distributed, and summaries were published in
the Newsletter, in the Journal of Geodesy and on the IAG
Websites (www.iag-aig.org and iag.dgfi.tum.de).
1.5 IAG Bureau
The meetings of the IAG Bureau (IAG President, Vice
President, Secretary General), normally held every monthby teleconferences and regularly before each EC meeting,were prepared and recorded. The President and Secretary
General participated in the IUGG Executive Committee
Meetings. The IAG was represented at meetings, e.g. the150th anniversaries of the Swiss Geodetic Commission,
Zurich, Switzerland, June 2011, the Arc Measurements in
Saxony, Dresden, Germany, June 2012, and in AustriaHungary, Vienna, Austria, September 2012, and Austrian
Geodetic Commission, Vienna, Austria, November 2013.
1.6 IAG Office
The IAG Office is located at Deutsches Geodätisches
Forschungsinstitut der Technischen Universität München,
Germany. A Website for internal IAG Communication is
maintained at http://iag.dgfi.tum.de.

1.7 Publications
The accounts of the Journal of Geodesy, the IAG monthly
scientific periodical, and the IAG Symposia Series wereregularly rendered with the Springer-Verlag. The volumes
edited during the referred period are: Vol. 136: IAG
Scientific Assembly 2009; Vol. 137: VII Hotine-Marussi
Symposium on Mathematical Geodesy 2009; Vol. 138:
Commission 1 Symposium 2010; Vol. 139: General
Assembly 2011; Vol. 140: QuGOMS Workshop 2011. The
biannual IAG Reports were published in the Travaux del’AIG Vol. 37 (2011), Vol. 38 (2013) and Vol. 39 (2015).
1.8 Individual Membership
The IAG has at present about 200 individual members. The
membership fee (USD 50/year or USD 150/4 years,
students with university certificate free) was collected bycredit cards or bank transfer, and the membership list was
regularly updated in cooperation with the Communication
and Outreach Branch for sending the IAG Newsletter. The
actual lists were provided to the Organizing Committees of
IAG Symposia in order to reduce the registration fee for
IAG members according to the IAG Bylaws.
1.9 IAG Symposia, Workshops and Schools
Important meetings of IAG components and sponsored
IAG meetings from July 2011 to June 2015 were:x SIRGAS General Meeting, Heredia, Costa Rica, 8-10
August 2011;x Int. Workshop on GNSS Remote Sensing for Future
Missions & Sciences, Shanghai, China, 7-9 August 2011;x Int. Symposium on Deformation Monitoring, Hong
Kong, China, 2-4 November 2011;
x IGS Workshop on GNSS Biases, Bern, Switzerland, 1819 January 2012;
x VLBI2010 Workshop on Technical Specifications(TecSpec), Bad Kötzting, Germany, 1-2 March 2012;
x 7th IVS General Meeting "Launching Next-Generation
IVS Network", Madrid, Spain, 12-13 March 2012;x Symposium and Workshop on PPP-RTK and Open
Standards, Frankfurt, Germany, 12-14 March 2012;
x IERS Global Geophysical Fluids Center (GGFC)
Workshop, Vienna, Austria, 20 April 2012;
x EUREF 2012 Symposium, Saint Mandé, France, 6-8
June 2012;
x IGS Analysis Center Workshop, Olsztyn, Poland, 23-27
July 2012;
x IAG Symposium at the AOGS-AGU (WPGM) Joint
Assembly, Singapore, 13-17 August 2012;

Report of the Secretary Generalx Int. Symposium on Space Geodesy and Earth System(SGES2012), Shanghai, China, 19-20 August 2012;
x WEGENER 2012 Symposium, Strasbourg, France, 1720 September 2012;
x 17th Int. Symposium on Earth Tides and Earth Rotation(ETS 2012), Cairo, Egypt, 24-28 September 2012;
x IDS Workshop, Venice, Italy, 25-26 September 2012;
x 7th IAG-IHO ABLOS Conference, Salle du Ponant,Monaco, 3-5 October 2012;x European VLBI Network (EVN) Symposium,
Bordeaux, France, 9-12 October 2012;x Workshop on Reflectometry using GNSS and Other
Signals, Prudue University, West Lafayette, IN, USA,
10-11 October 2012;
x Int. VLBI Technology Workshop, Westford, MA, USA,22-24 October 2012;
x Int. Technical Laser Workshop “Satellite, Lunar, andPlanetary Laser Ranging: Characterizing the Space
Segment”, Frascati, Italy, 5-9 November 2012;x 21st European VLBI for Geodesy and Astrometry
Workshop, Helsinki, Finland, 6-8 March 2013;
x 17th Int. Symposium on Earth Tides “Understand theEarth”, Warsaw, Poland, 15-19 April 2013;
x Seventh IVS Technical Operations Workshop,
Westford, MA, USA, 6-9 May 2013;
x IERS Workshop on Local Ties and Co-locations, Paris,
France, 21-22 May 2013;
x EUREF Symposium, Budapest, Hungary, 29-31 May 2013;
x Int. Symp. “Reconciling Observations and Models of
Elastic and Viscoelastic Deformation due to Ice Mass
Change”, Ilulissat, Greenland, 30 May – 2 June 2013;
x GNSS Precise Point Positioning: Reaching Full
Potential, Ottawa, Canada, 12-14 June 2013;x VIII Hotine-Marussi Symposium, Rome, Italy, 17-21
June 2013;
x Int. Conference on “Earth Observations and Societal
Impacts”, Tainan, Taiwan, 23-25 June 2013;
x Int. Symposium on Planetary Sciences (IAPS2013),
Shanghai, China, 1-4, July 2013;
x IAG Scientific Assembly, Potsdam, Germany, 1-6
September 2013;
x 2nd Joint Int. Symposium on Deformation Monitoring,
Nottingham, UK, 9-11 September 2013;
x Third Symposium on “Terrestrial Gravimetry: Staticand Mobile Measurements (TGSMM-2013)”, St
Petersburg, Russia, 17-20 September 2013;
x Scientific Developments from Highly Accurate SpaceTime Ref. Systems, Paris, France, 16-18 Sept. 2013;
x ITU/BIPM Workshop on “The Future of the International
Time Scale”, Geneva, Switzerland, 19-20 September 2013;
x 2nd Int. VLBI Technology Workshop, Seogwipo, Rep.
of Korea, 10-12 October 2013;

961

x SIRGAS Symposium, Panama City, Panama, 24-26
October 2013;
x 18th Int. Workshop on Laser Ranging, Fujiyoshida,
Japan, 9-15 November 2013;
x European VLBI Network Technical and Operations
Group (EVN TOG) Meeting, Bad Kötzting, Germany,
23-24 January 2014;
x 8th IVS General Meeting, Shanghai, China, 2-7 March 2014;
x European Reference System (EUREF) Symposium,
Vilnius, Lithuania, 4-6 June 2014;
x IGS Workshop "Celebrating 20 Years of Service",
Pasadena, CA, USA, 23-27 June 2014;
x 3rd Int. Gravity Field Service (IGFS) General
Assembly, Shanghai, China, 30 June – 6 July 2014;
x Int. Symposium on Geodesy for Earthquake and Natural
Hazards (GENAH 2014), Matsushima, Miyagi, Japan,
22-27 July 2014;
x 18th WEGENER General Assembly: Measuring andModelling our Dynamic Planet Leeds, UK, 1-4
September 2014;
x Journees 2014 "Systemes de reference spatiotemporels", Pulkovo Observatory, St. Petersburg,
Russia, 22-24 September 2014;
x 12th European VLBI Network (EVN) Symposium,
Cagliari, Italy, 7-10 October 2014;
x Reference Frames for Applications in Geosciences(REFAG2014), Luxembourg, 13-17 October 2014;
x IDS Workshop, Konstanz, Germany, 27-28 October 2014;
x ILRS Technical Workshop, Greenbelt, MD, USA, 27-31
October 2014;
x Third Int. VLBI Technology Workshop, Groningen/
Dwingeloo, The Netherlands, 10-13 November 2014;
x PECORA 19 Fall Meeting (ASPRS, IAG, ISPRS)“Sustaining Land Imaging: Unmanned Aircraft Systems(UAS) to Satellites”, Denver, CO, USA, 17-20
November 2014;
x SIRGAS Symposium, La Paz, Bolivia, 24-26 November
2014;
x 11th Int. Symposium on Location-Based Services,
Vienna, Austria, 26-28 November 2014.
x Eighth IVS Technical Operations Workshop (TOW
2015), Westford, MA, USA, 4-7 May 2015.
x 8th Workshop on GNSS Reflectometry (GNSS+R 2015),
Potsdam, Germany, 11-13 May 2015.
x 22nd Meeting of the European VLBI Group for Geodesy
and Astrometry (EVGA) Ponta Delgada, Azores,
Portugal, 17-21 May 2015.
x SIRGAS Workshop on Vertical Reference Frames,
Curitiba, Brazil, 18-22 May 2015;
x GIA Modeling, Fairbanks, AK, USA, 26-29 May 2015;
x European Reference Frame (EUREF) Symposium,
Leipzig, Germany, 3-5 June 2015.

H. Drewes

962

The following IAG Schools were held:
x SIRGAS School “Geodetic Reference Systems”,
Heredia, Costa Rica, 3-5 August 2011;
x GNSS School “New GNSS Algorithms & Techniques for
Earth Observations”, Hong Kong, China, 14-15 May 2012;
x Int. Summer School “Space Geodesy & Earth System”,
Shanghai, China, 21-25 August 2012;
x SIRGAS School “Real Time GNSS Positioning”,
Concepción, Chile, 24-26 October 2012;

x IVS Training School for Next Generation Geodetic andAstrometric VLBI, Helsinki, Finland, 2-5 March 2013.
x 11th School of the International Geoid Service: Heights
and Height Datum, Loja, Ecuador, 7-10 October 2013.
x SIRGAS School “Reference Systems, Crustal
Deformation and Ionosphere Monitoring”, Panama City,
Panama, 21-23 October 2013.
x SIRGAS School “Vertical Reference Systems”, La Paz,
Bolivia, 20-22 November 2014.

2 Finances
The financial report includes the result 2011-2014 (Table 1), the budget 2015-2018 (Table 2) and the report of the Audit
Committee (Appendix A).
Table 1 Financial Report 2011-2014
Expenditures
11.5
11.6
12.2
14.1
14.2
16.2
18.6
19

20

Result 2011- 2014 in EUR
Receipts

Administration, Travel
Representation
Proceedings IAG Symposia Series
Assemblies, Organization
Symposia, Travel Awards
Prizes, Young Authors Awards
Credit Card Service

8.033,14
5.210,97
22.611,67
15.248,87
50.555,62
2.246,56
766,63

15
1
2
3.1
3.2
3.3
4.2
4.4
6

IUGG Allocation
Membership Fee
Other Grants
IAG Symposia Series
Journal of Geodesy
OthersIAG FundGeoid School
Total Receipts

103.378,81
16.036,60
962,262.400,00
12.271,00
297,00252,84217,98135.816,46

Total Expenditures
Surplus104.673,46
31.143,03

Total

135.816,49

Total

135.816,49

AssetsBalance 31.12.2014 in EUR
Liabilities

Staatsoberkasse 31.12.2010
Deposit IGS
Surplus 2011
Surplus 2012
Surplus 2013107.626,42
9.647,98
3611,08
20.529,39
9.103,76

Net Capital 31.12.2014
Refund IGS
Deficit 2014135.726,15
12.691,28
2.101,20

Total

150.518,63

Total

150.518,63

Net Capital 2014 in EUR
Open 1.1.2011
Surplus
Deficit IGS *)107.626,42
31.143,03-3.043,30

Total

135.726,15*) Refund USD 2.807,05 Reserve for IGS

Report of the Secretary General

963

Table 2 Budget 2015-2018
Budget for the period 1.1.2015 - 31.12.2018 in EUR
Receipts

Expenditures
11.2
11.5
11.6
12.1
12.2
13.1
13.2
14.2
16.2
18.6
19

Administration, Equipment
Administration, Travel
Administration, Representation
Publications, Outreach
Publications, IAG Symposia Series
Assemblies, Organization
Assemblies, Travel
Symposia, Travel Awards
Prizes, Young Authors Awards
Credit Card Service
Total Expenditures

4.000
25.00010.0001.000
25.00020.00010.00060.0004.000
1.000
160.000

Total

160.000

15
1
2
3
3.1
3.2
4
4.1

IUGG Allocation
Membership Fee
Other Grants
Sales of Publications
IAG Symposia Series
Journal of Geodesy
Miscellaneous
IAG Fund80.00015.0002.000

6Total Receipts
Deficit110.000
50.000Total

160.000

2.000
10.0001.000

Net Capital 2018 in EUR
Balance 31.12.2018

86.000Open 1.1.2015
Deficit136.000-50.000

Total

86.000Total

86.000Appendix A

The Audit Committee makes the following observations
and comments on the IAG accounts:

IAG Audit Committee Report
Committee members, appointed by the IAG Council:
Denizar Blitzkow, Kosuke Heki, Markku Poutanen
The Audit
functions:

Committee

performed

thefollowing

1.1 Noticed that the accounts were checked by theBavarian Ministry for Science, Research and Art(“Bayerisches Staatsministerium für Wissenschaft,
Forschung and Kunst”) together with the DGFI
accounts and that the accounting, bookkeeping andbudgeting are in EUR.
1.2 Examined the receipts and bank statements of the IAG
account for the period January 2011 to December 2014;
checked the balances appearing in the annual andquadrennial IAG reports.
1.3 Examined expenditure to ensure conformity with the
2011-2014 budget as approved at the IUGG General
Assembly in Melbourne in July 2011.
1.4 Examined the budget for the period 2015-2018.

2.1 The accounts were well presented and all expenditures
were supported by receipts and bank statements.
2.2 The banking service costs are completely free ofcharge. The possibility to use the DGFI account andthe use of EUR in bookkeeping simplifies accounting
and saves for extra costs.
2.3 During the review period, the IAG made an operating
surplus of EUR 31243. This amount is added to the
IAG reserve, leaving reserves of approximately EUR
136000 at the end of 2014.
2.4 The Audit Committee found that the IAG had a surplus
on the average over the 4 year period on approximately
EUR 7800 per year with quite large annual variations,from surplus EUR 20529 in 2012 to deficit of EUR
2101 in 2014. The Audit Committee concludes that thebudget estimates are being based on the experience
accumulated over the years and the annual variation
depends on the meetings and other activities each year.
2.5 The committee examined the provisional budget for
2015-2018 which seems to be realistic as compared tothe past period 2011-2014.

H. Drewes

964

The Audit Committee
recommendations:

makes

the

following

3.1 The current positive balance almost reaches the 4-year
budget, what is too high. Intended deficit of EUR
50000 in 2014-2018 will make the balance of bankaccount smaller, as already recommended in the 2011
audit report.
3.2 The budget for grants to young scientists has been
increased during the last period. The committee
encourage to continue the trend and use some of thesurplus for this, as planned in the 2015-2018 budget.
3.3 The organizers of the IAG meetings should be
encouraged to continue publishing their proceedingsby Springer Verlag series in order to maintain a seriesof publications with the IAG label and ensuring a highstandard as well. This series has been developed in avery positive way and is recognized by ISI web of
Science.

3.4 The IAG EC and COB should continue efforts to
attract people more effectively to join IAG. Current
membership benefits may not be attractive enough,and additional member functions available on IAG
web page are relatively invisible to most potential
members.
On behalf of the IAG Council, the Audit Committee
has the following acknowledgements and thanks
4.1 Hermann Drewes, IAG Secretary General, for his
efficient and cautious administration and managementof the IAG Office.
4.2 The German Geodetic Research Institute DGFI for
administrative and accounting support.
Prague, Czech Republic, 29 June 2015
Denizar Blitzkow, Kosuke Heki, Markku Poutanen

Minutes of the IAG Council Sessions

965

Minutes of the IAG Council Sessions at the General Assembly 2015
Helmut Hornik ∙ Franz Kuglitsch (Minutes Takers) ∙ Hermann Drewes (Secretary General)

Place: Prague Conference Centre, Prague, Czech Republic
Time: June 24, 08:30-10:00 and June 30, 18:00-20:00

AgendaWednesday, June 24, 2015, 08:30-10:00, Meeting Hall 5
1. Welcome and adoption of agenda
2. IUGG2015 organisational issues
3. Agenda of the Opening and Closing Sessions
4. Information on IAG Awards
5. Proposal of the IAG Budget 2015-2018
6. Appointment of the Audit Committee
7. Appointment of the Resolutions Committee
8. Review of the 2015 election process and results
9. Report on the Review of IAG Statutes and Bylaws
10. Status of GGOS and ICCT
11. Status of Journal of Geodesy and IAG Symposia Series
12. Status of IAG and National Reports 2011-2015
13. Venue Proposals for the Scientific Assembly 2017
14. Any other business (all)
15. Adjourn
Tuesday, June 30, 2015, 18:00-20:00, Conference Hall
16. Venue proposals for the Scientific Assembly 2017
17. Election of the Venue of the Scientific Assembly 201718. Audit Committee Report, discharge of the management
19. Approval of the IAG Budget 2015-2018
20. Approval of the revised Statutes and Bylaws
21. Report of the IAG Resolutions Committee
22. Approval of Resolutions
23. Report from IUGG Council and Executive Committee
24. IAG Representatives to external bodies
25. Preparation of the IAG and IUGG Closing Sessions
26. Any other business
27. Closure

Participants
IAG National Delegates: Argentina (Sergio Cimbaro,
June 30), Australia (Chris Rizos), Austria (Johannes
Böhm), Belgium (Juliette Legrand), Brazil (Denizar
Blitzkow), Colombia (Laura Sanchez), Czech Republic(Petr Holota), Denmark (Niels Andersen, June 24),
Estonia (Artu Ellman, June 24), Finland (Markku
Poutanen), France (Francoise Duquenne), Germany(Jürgen Müller), Greece (Elias Tziavos, June 24,
Christopher Kotsakis, June 30), Hungary (József Adám,
June 24), India (Virendra Tiwari, June 24, Vijay Prasad
Dimri, June 30), Israel (Gilad Even-Tzur, June 30), Japan(Kosuke Heki), Korea (Phil-Ho Park), Luxembourg (Tonie
van Dam), New Zealand (Matt Amos), Norway (Oddgeir
Kristiansen, June 24), Poland (Jan Krynski), Portugal (JoãoTorres, June 24), Russia (Vladimir Kaftan), Slovak
Republic (Ladislav Brimich, June 30), Sweden (Jonas
Agren), Switzerland (Adrian Wiget), Turkey (SonerÖzdemir), United Kingdom (Peter Clarke), USA (Jeffrey
Freymueller)
IAG Executive Committee (guests): Harald Schuh (VicePresident), Hermann Drewes (Secretary General), Michael
Sideris (Immediate Past President), Helmut Hornik(Assistant Secretary), Urs Marti (President Commission 2),
Riccardo Barzaghi (Representative of the Services).
Guests: Danan Dong (China), Larry Hothem (USA),
Johannes Ihde (Germany), Franz Kuglitsch (Assistant
Secretary General), Shah Muhammad (Pakistan), Diego
Pinon (Argentina), M. F. Le Quentrec-Lalancette (France),
Alexander Ustinov (Russia).

966

Minutes
Wednesday, June 24, 2015, 08:30-10:00, Meeting Hall 5
1. Welcome and adoption of agenda
Ch. Rizos opened the first Session of the IAG Council
2015. He invited the participants to attend the IAG
Opening Session with the following reception on June 25.
The agenda had been distributed by e-mail before, and wasunanimously adopted.
2. IUGG2015 organisational issues
H. Drewes presented an overview of the status and venueof the present 26th IUGG General Assembly summarising
the IAG symposia and meetings. There are:x 8 IAG Symposia (distributed over 52 sessions),x 3 Joint Association Symposia led by the IAG,
x 10 Joint Association Symposia sponsored by the IAG,
x 1 Union Symposia organised by the IAG,
x 10 Union Symposia sponsored by the IAG,
x 4 IAG EC Meetings (June 23, 26, 29; new EC: July 2),x 2 IAG Council Meetings (June 24 and 30).
There will be 9 Union Lectures (8 Associations and theUnion); H. Schuh will present “Contributions of Geodesy
to Monitoring Natural Hazards and Global Change”.
Additional public IAG events are the Opening Session(June 25), Dinner (June 28) and Closing Session (July 01).
H. Drewes then listed the IUGG 2015 statistics. Ca.
3100 participants have registered so far. 700 applications
for travel support and/or registration fee waiving were
submitted, 51 of them to the IAG. IAG receives nearly
9.000 US$ from the IUGG and 13 waived registration fees(~ 7.000 US$) from the LOC. Additional funds come fromthe IAG budget, thus about 37.000 US$ could be given for
travel awards and waived registration fee. The total
number of oral and posters presentations amounts to 5700;
ca. 580, i.e. 10%, are associated to the IAG. Most of thesubmitted IAG abstracts refer to Commission 2 “Gravity
Field” (136 to the static and 86 to the variable gravity);
each of the other 3 Commission symposia received ca. 80,
and each of the 3 GGOS symposia ca. 40 abstracts.
3. Agenda of the Opening and Closing Sessions
H. Drewes presented the schedules of the IAG Opening
Session followed by the IAG reception, and the IAG
Closing Session followed by the IUGG Closing Session.
He then explained the time schedule concerning the IAG
related sessions. Maximum two parallel IAG sessions willtake place and no sessions are scheduled when major
IUGG events such as the Union lectures will be held.

H. Hornik, F. Kuglitsch, H. Drewes

4. Information on IAG Awards
H. Drewes informed the EC on the awards to be presented
at the IAG Opening Session according to the IAG rules:
The Levallois Medal (installed 1979) is awarded inrecognition of distinguished service to the Association,
and/or to the science of geodesy in general. An ad hoc
committee of Honorary Presidents nominates a candidate
which has to be confirmed by the IAG EC. At the General
Assembly 2015 it will be granted to Reiner Rummel,
Munich/Germany, in particular for his merits as principal
investigator of the satellite mission "Gravity Field andSteady-State Ocean Circulation Explorer" (GOCE).
The Guy Bomford Prize (installed 1975) is awarded toa young scientist for outstanding contributions to geodesy.
The National Committees of IUGG member countries send
nominations to the IAG Bureau. A committee consisting of
the Presidents of the IAG Commissions and two othermembers appointed by the Bureau selects the awardee. The
2015 Bomford Prize is awarded to Yoshiyuki Tanaka,
Tokyo/Japan in particular for his recent contributions in
the field of geodynamics, regional tectonics, and glacialisostatic adjustment. He has opened new interdisciplinary
research areas spanning modern geodesy and seismology.
IAG Young Authors Award: This prize is dedicated toyoung scientists for excellent publications in the Journal of
Geodesy (JoG). Nominations are made by the Editor-inChief, moreover all proposals of at least three IAG Fellows
or Associates are considered. The IAG EC decides on theawardees. The prize is for each JoG annual volume andhanded over in a 2-years-turn on the occasion of the IAG
General and Scientific Assemblies. The prize comprises acertificate and US$ 1000. For the respective periods
considerable numbers of candidates were nominated; theEC selected for 2013 Krzysztof Sośnica, Bern/Switzerland
for his article "Impact of loading displacements on SLRderived parameters and on the consistency between GNSS
and SLR results") and for 2014 Alvaro Santamaría Gómez,Guadalajara/Spain and La Rochelle/France for his article"Long-term vertical land motion from double-differenced
tide gauge and satellite altimetry data").
5. Proposal of the IAG Budget 2015 – 2018
H. Drewes gave an overview of the financial report 2011 –2014. The accordance of receipts and expenditures with theapproved budget has to be verified by an Audit Committee
established by the Council. He emphasised that by far mostof the receipts are coming from the IUGG allocation, but
the fees of the IAG individual membership are
considerable (at present ca. 200 full members).

Minutes of the IAG Council Sessions

In the following H. Drewes explained the planned
budget for the next period 2015-2018. The major
expenditures refer to travel grants for young scientists,
followed by publications, organisation of assemblies andadministrative travel costs. In this context he emphasised
the considerable support by the German Geodetic ResearchInstitute (DGFI) and the Bavarian Academy of Sciences.
Furthermore, no bank account and transfer costs occur for
the IAG Office, because the State of Bavaria is covering
these as well as the continuous control of all expenditures.
This has particularly to be acknowledged.

967

x President of Commission 1: G. Blewitt, USA
x President of Commission 2: R. Pail, Germany
x President of Commission 3: M. Hashimoto, Japanx President of Commission 4: M. Santos, Canada
x Member at Large – Position 1: L. Combrinck, S. Africa
x Member at Large – Position 2: M. C. Pacino, Argentina
x Service Representative 1: R. Neilan, USA
x Service Representative 2: R. Barzaghi, Italy
x Service Representative 3: A. Nothnagel, Germany
All elected colleagues confirmed to accept their election.
9. Report on the Review of IAG Statutes and Bylaws

6. Appointment of the Audit Committee
As mentioned above, the financial report 2011-2014 has tobe proved by an audit committee to be established by theCouncil. The colleagues D. Blitzkow, Brazil, K. Heki,
Japan, and M. Poutanen, Finland were proposed. The
Council adopted the proposal unanimously.
7. Appointment of the Resolutions Committee
The colleagues R. Barzaghi, Italy, R. Gross, USA and P.
Willis, France were proposed to form the Resolutions
Committee. The proposal was unanimously accepted.
Two resolutions were proposed so far concerning
1. the installation of an International Height Reference
System (IHRS) for unifying the existing physical heightsystems as investigated in the GGOS Theme 1;
2. the establishment of a Global Absolute Gravity
Reference System to replace the International Gravity
Standardisation Net (IGSN71) which dates back to
1971, and many of its sites do not exist anymore.
8. Review of the 2015 election process and results
According to the IAG Statutes and Bylaws, the membersof the EC are elected by the Council every 4 years byemail-voting before the General Assembly (except the
GGOS Chair and the ICCT President which are appointed
by the EC). The IAG President appoints the Nominating
Committee. These were M. G. Sideris, Canada (Chair), S.
de Freitas, Brazil, Y. Fukuda, Japan, and B. Heck,
Germany. The candidates are nominated by the delegatesof the Adhering Bodies, the IAG officers, IAG Fellows,
and individual members. M. G. Sideris presented theelection process and the results of the elections from 42
incoming votes in total:
x President: H. Schuh, Germanyx Vice-President: Z. Altamimi, France
x Secretary General: H. Drewes, Germany
x President of the COB: J. Ádám, Hungary

The present IAG Statutes and Bylaws were adopted at theGeneral Assembly 2007. According to the IAG Bylaws, a
Review Committee has been installed in 2011 with themembers M. Sideris, Canada (Chair), Y. Fukuda, Japan, R.
Neilan, USA, and H. Schuh, Germany. After a call for
proposals incoming suggestions were revised and newversions of the Statutes and Bylaws were circulated. A
preliminary update was presented to the Council at the
IAG Scientific Assembly 2013; M. Sideris presented now
the latest version. The Council has to prove the texts anddecide on the acceptance or rejection. This voting will takeplace at the second Council meeting on June 30, 2016.
10. Status of GGOS and ICCT
H. Kutterer, Germany has been re-appointed by the IAG
EC as the Chair of Global Geodetic Observing System(GGOS). He reported that the ToR are going to be updated
and adapted to the present needs. The new version will bepresented to the EC to be proved and confirmed.
After two periods N. Sneeuw has retired from his
position as the ICCT Chair. The EC has appointed P.
Novak, Czech Republic as his successor. The revised IAG
Bylaws prescribe that the ICCT becomes an IAG
component like the Commissions and Services. Thus the
ICCT Chair will be elected by the IAG Council in future.
11. Status of the Journal of Geodesy (JoG) and the
IAG Symposia Series
H. Drewes presented a report of the JoG Editor in Chief R.
Klees on the recent development of Journal. The overview
informs on the impact factor, the number of submissions
and rejections etc. According to the IAG Bylaws, thepresent JoG Editor in Chief, R. Klees, The Netherlands,
recommended a list of candidates for the new Board. This
list was published on the IAG Website, and additional
nominations were received. The current Editorial Board
will appoint the new Board during this General Assembly.

968

Then H. Drewes presented a report of P. Willis,
Assistant Editor of the IAG Symposia Series, on the status(http://www.springer.com/series/1345?detailsPage=titles).
Volumes 136 - 141 have been published in the recent
period, 5 others are in progress. The time span between
submission and publication could be reduced considerably.
This is particularly due to the immediate online publicationof each article as soon as approved. The hard copy
publication takes considerably more time.
The Council discussed to release a digital version of theseries as open access. H. Drewes informed that this option
would be possible if the IAG pays the open-access fee.
12. Status of IAG Reports (Travaux de l’AIG) andNational Reports 2011-2015
H. Drewes informed the Council that all received texts for
the IAG Reports 2011 – 2015 (Travaux Vol. 39) and the
National Reports are available on the IAG Website.
13. Proposals for the Venue of the IAG Scientific
Assembly 2017
H. Drewes informed the Council that only one application
has been received for the IAG Scientific Assembly 2017.
The Geodetic Society of Japan invites to hold thisAssembly from July 30 – August 4, 2017 in theInternational Conference Centre, Kobe, Japan. The
President of the Geodetic Society of Japan and Chair of the
National Committee for the IAG, K. Heki, Hokkaido
University, Sapporo, will present the proposal. It isplanned to hold the IAG Scientific Assembly 2017
together with the IASPEI Scientific Assembly.
14. Any other business
There was no other topic to be discussed.
15. Adjourn
Ch. Rizos invited all delegates to study the updated IAG
Statutes and Bylaws for its adoption on June 30.
Tuesday, June 30, 2015, 18:00-20:00, Conference Hall
The IAG President, Ch. Rizos, opened the second meetingof the IAG Council 2015 and welcomed the participants.
16. Venue proposal for the Scientific Assembly 2017
K. Heki, the Japanese IAG Correspondent, presented thebid from Kobe, Japan, for organizing the IAG Scientific

H. Hornik, F. Kuglitsch, H. Drewes

Assembly 2017 and mentioned that there is interest toorganise a joint Assembly together with IASPEI. Kobe was
the only bid IAG has received to host the IAG Scientific
Assembly 2017. The IAG Council noted the venue
proposal for the Scientific Assembly 2017 and K. Heki was
asked to inform the responsible Japanese institutions tostart the preparations in time.
17. Election of the Venue of the IAG Scientific
Assembly 2017
All IAG Council Members voted in favour of organizing a
joint IAG-IASPEI Assembly in Kobe, Japan in 2017. Thus
the invitation from Kobe, Japan, to organise a joint IAGIASPEI Assembly in 2017 was accepted unanimously(Motion: Jeffrey Freymueller, 2nder: Petr Holota).
18. Report of the Audit Committee and discharge ofthe management
On behalf of the Audit Committee, K. Krynski presented
his report and informed that a complete collection of all
relevant budget documents has been handed over by the
IAG Office and has been examined carefully, and hemoved for the discharge. He mentioned that the new IAG
EC should try to attract more individual members and tostrengthen the benefits of the IAG membership. The IAG
Financial Report 2011-2014 was unanimously adopted andthe Secretary General was discharged.
19. Approval of the IAG Budget 2015-2018
Ch. Rizos mentioned that the IAG Bureau and EC havediscussed the proposal for the IAG Budget 2015-2018, andnoted that the names of expenditures and incomes are
given by IUGG and therefore cannot be changed. Also, he
noted that the new IUGG Statutes and By-Laws will allow
Associations to have individual members from all
countries in the world.
H. Drewes summarised the IAG Budget 2015-2018 andmentioned that the Bureau thinks that the costs foradministration and travel should be lowered further infuture. He noted that the allocations from IUGG are basedon the participation of IAG delegates to the last threeIUGG General Assemblies (Sapporo 2003, Perugia 2007,
Melbourne 2011), where the participation of IAG delegates
was not as high as in Prague 2015. Currently, IAG has only
201 individual members and some few student members.
He clarified that the Student Membership Fee is free ofcharge and the students need to present their students ID
every year. Also, he mentioned that the Communication
and Outreach Branch (COB; J. Adam) is asking for further

Minutes of the IAG Council Sessions

input to further strengthen the IAG website and thevisibility of IAG. The IAG Council approved the IAG
Budget 2015-2018 unanimously (Motion: Jürgen Müller,
2nder: Jeffrey Freymueller).
20. Approval of the revised Statutes and Bylaws
H. Drewes presented the revised Statutes and Bylaws onbehalf of M. Sideris with slightly revised wording
suggested by J. Freymueller. The IAG Council approved
the revised Statutes and Bylaws unanimously (Motion:
Jürgen Müller, 2nder: Jeffrey Freymueller). H. Drewes
noted that the revised Statutes and Bylaws will be sent to
the IUGG for approval, and will then be published on the
IAG website and in the Geodesist’s Handbook 2016.

969

General Assembly are related to IAG which is a very
positive development. J. Freymueller added (i) that the
IUGG Council is now eligible to vote electronically, andtherefore is no longer a body that decides only once in four
years, and (ii) that now scientists from any country are
eligible to be elected to any association officer position,
except for President. H. Schuh noted that also IAG should
continue with electronic voting. The IAG Council noted
the report from IUGG Council and Executive Committee.
24. IAG Representatives to external bodies
H. Drewes mentioned that several IAG people will serve as
IUGG liaison officers to international organisations in the
period 2015-2019. The IAG Council noted the IAG
representatives to external bodies.

21. Report of the IAG Resolutions Committee
25. Preparation of the IAG and IUGG Closing Sessions
Ch. Rizos mentioned that the Chair of the IAG Resolutions
Committee is not present.
H. Drewes presented the two revised IAG Resolutions
after wording change. Resolution 1 concerns the“Definition and Realisation of an International Height
Reference System” while Resolution 2 relates to the“Establishment of a Global Absolute Gravity Reference
System”. Ch. Rizos noted that so far there exists noInternational Height Reference System. The IAG Council
noted the report of the IAG Resolutions Committee.

H. Drewes presented the program for the IAG Closing
Session on 1 July. The program topics include the reportsof the IAG led Symposia by the respective conveners, thepresentation of the IAG Resolutions by the Chair of the
IAG Resolution Committee and the Fellows by the IAG
Secretary General, the inaugural speech of the new IAG
President, H. Schuh, and the closing speech of the outgoingpresident, Ch. Rizos. All colleagues are invited to attend
the Closing Session. The IAG Council noted the
preparations of the IAG Closing Session.

22. Approval of Resolutions
26. Any other business
The plenary discussed the texts of both resolutions; someslight changes in the wording were applied. The texts will
also be submitted to the IUGG for approval. The IAG
Council approved Resolution 1 unanimously (Motion:
Chris Rizos, 2nder: Adrian Wiget). The IAG Council
approved Resolution 2 with two against (Motion: Chris
Rizos, 2nder: Jan Krynski)
23. Report from the IUGG Council and Executive
Committee
Ch. Rizos gave a short report on the meeting of the IUGG
Council and Executive Committee. The IUGG Secretariat
received two bids from Montreal, Canada, and New Delhi,
India to hold the 2019 IUGG General Assembly. The
IUGG Council decided for Montreal, Canada. M. Sideris
was elected as IUGG President (2015-2019), Ch. Rizos as
IUGG Bureau Member (2015-2019), and J. Krynski asmember of the IUGG Finance Committee (2015-2019). A
new Union Commission on Planetary Science has been
established. 15% of all abstracts of the IUGG 2015

H. Drewes mentioned that (i) a new service was installedby the IAG EC, the International Geodynamics and Earth
Tides Service, which unifies the International Center for
Earth Tides (ICET) and the Global Geodynamics Project.
(ii) The Journal of Geodesy has got a new Editorial Board
and Jürgen Kusche, Germany, as the new Editor in Chief.
(iii) The new Statutes & By-Laws establish an Editor in
Chief and Assistant Editor for the IAG Symposia Series.
They will be elected by the new EC. J. Freymueller and L.
Sánchez were proposed by the old EC for these positions.
J. Krynski suggested discussing in future also theresolutions proposed by the IAG to the IUGG in the IAG
Council and not only in the EC. The IAG Council noted
this other business information.
27. Closure
Ch. Rizos closed the session with thanks to the participants
for their attendance and contributions at 20:00.

970

H. Hornik, F. Kuglitsch, H. Drewes

Fig . 1 Participants of the IAG Opening Session at the XXVI IUGG General Assembly, Prague, Czech Republic, 25 June 2015

Summary of the IAG Executive Committee Sessions

971

Summary of the IAG Executive Committee Sessions
Hermann Drewes (Secretary General) ∙ Helmut Hornik (Assistant Secretary)

Place: Prague Congress Centre, Prague, Czech Republic
Time: June 23, 08:30-15:00, June 26, 18:00-20:00 andJune 29, 18:00-20:00, 2015

Attendees
Voting: Ch. Rizos (IAG President), H. Schuh (IAG Vice
President), H. Drewes (IAG Secretary General), M. Sideris(Immediate IAG Past President), T. van Dam (Comm. 1
President), U. Marti (Comm. 2 President), R. Gross(Comm. 3 President), D. Brzezinska (Comm. 4 President),
J. Adám (COB President), H. Kutterer (GGOS Chair), R.
Barzaghi, T. Herring, R. Neilan (Repres. of the Services).
Regrets: C. Brunini, R. Wonnacott (Members at Large)
Non-voting: N. Sneeuw (ICCT President), H. Hornik(Assistant Secretary).
Guests: R. Klees (JoG Editor in Chief), P. Willis (Assist.
Editor IAG Symposia Series), F. Kuglitsch (IUGG Exec.
Secretary), A. Kealy (Comm. 4 Vice President).

Summary of Agenda Items
Session I: Tuesday, June 23, 2015, 08:30 – 15:00
1 Welcome and adoption of agenda
Ch. Rizos, welcomed the members of the IAG Executive
Committee (11 out of 15 voting members, 2 non-voting
members, and 4 guests. The agenda had been distributedby e-mail and was adopted unanimously. Minutes of theprevious EC meeting were available on the IAG Office
Homepage.

2 IUGG2015 organisational issues
H. Drewes presented the detailed time schedule and thesession arrangements of the IAG activities during theupcoming General Assembly. In total, 4231 participants
attended the General Assembly, 534 scientists presented
573 papers (11.8% of all Assembly papers) at the IAG
sessions.
3 Agenda of Council meetings, June 24 and June 30
The IAG Council meetings were held on June 24 and 30.
The EC is invited to participate in these meetings as theCouncil has the function of the parliament of the IAG andto supervise the activities of the IAG EC and the IAG
components. Ch. Rizos added the necessity to demonstratethat the activities of the IAG comprise much more thanorganizing conferences but also inducing actions andcontacts between scientists and inter-relations in particular.
4 Agenda of Opening and Closing Sessions
H. Drewes explained that the IUGG Opening Session willtake place on June 23 at 16:30; everybody was invited. The
IAG Opening Session was scheduled for June 25, 18:00 –20:00 in the Panorama Hall. The agenda comprised mainly
x Reports of the President and Secretary General;x Highlight reports of the IAG Commissions, ICCT,COB, GGOS, Services’ representatives;
x Presentation of the Levallois Medal;
x Presentation of the IAG Young Authors Awards;
x Presentation of the Guy Bomford Prize followed by the
Guy Bomford Prize Lecture.

H. Drewes, H. Hornik

972

Subsequently to the Opening Session the participants wereinvited to the IAG Reception, and to the IAG Dinner which
took place on June 28. H. Drewes thanked P. Holota fororganising these events.
The IAG Closing Session was scheduled for July 1,
13:30 – 15:00 in the Conference Hall with the main topics
x Reports of the IAG Symposia conveners;
x Presentation of the IAG Resolutions;x Presentation of the new IAG Fellows;x Inaugural Speech of the new IAG President (H. Schuh).
The IUGG Closing Ceremony followed at 16:30 in theCongress Hall.

Three drafts for IUGG resolutions concerning the IAG
were submitted, namely
x Future Satellite Gravity Mission Constellation,
x Global Geodetic Reference Frame, andx Real-Time GNSS Augmentation of the Tsunami Early
Warning System.
A Resolution Committee has to be established by the
IAG Council to collect proposals and to examine the IAG
resolutions. According to the IAG Bylaws, the EC may
propose candidates. R. Barzaghi, R. Gross (chair) and P.
Willis were elected to form the Committee.
H. Drewes presented then the draft resolutions for the
IAG and those for the IUGG concerning the IAG. Somewording was changed by the Executive Committee.

5 IAG Financial Summary 2011 – 2014
H. Drewes presented an overview on the receipts andexpenditures within the period 2011 – 2015. A major partwas spent for travel awards to young scientists toparticipate in symposia and workshops. For the present
IUGG General Assembly nearly 700 applications were
submitted to the IUGG, 51 of those to the IAG. Moreover aconsiderable amount was needed for buying a bulk of the
IAG Assembly Proceedings in the IAG Symposia Series
and the Geodesist’s Handbook. He informed that joint
projects of at least two Associations can be supported by
the IUGG. At present there are two IAG projects: ‘Detailed
Geoid for Africa’ together with IASPEI and “Monitoring
crustal deformation and the ionosphere by GPS in the
Caribbean” together with IAGA and IASPEI.
6 Proposal for members of the Audit Committee TBD
by the Council
According to the IAG Bylaws, the EC may propose
candidates for the Audit Committee to examine the IAG
accounts for the past period. The final nomination of thecommittee members is assigned to the IAG Council. D.
Blitzkow, Brazil, K. Heki, Japan, and M. Poutanen,
Finland, were suggested for the Committee. The proposal
will be submitted to the Council meeting on June 24.
7 Nomination of members of the IAG Resolution
Committee
At present two drafts for IAG resolutions were submitted
concerning
x Definition and realisation of an International Height
Reference System, andx Establishment of a Global Absolute Gravity Reference
System.

8 Levallois Medal, Guy Bomford Prize, Young
Authors Award, new IAG Fellows
H. Drewes informed that there are three IAG Awards. The
details may be read in the IAG Bylaws.
x Levallois Medal: The Levallois Medal 2015 is given to
R. Rummel, Munich, Germany, in particular for his
merits as principal investigator for the satellite mission"Gravity Field and Steady-State Ocean Circulation
Explorer" (GOCE) launched in 2009.
x Guy Bomford Prize: The 2015 Guy Bomford Prize isgiven to Y. Tanaka, Tokyo, Japan in particular for his
recent contributions in the field of geodynamics,
regional tectonics, and glacial isostatic adjustment. His
work has opened new interdisciplinary research.
x IAG Young Authors Award: For the best publication in
the Journal of Geodesy K. Sośnica, Bern, Switzerland,
was elected by the EC for 2013, and A. Santamaría
Gómez, La Rochelle, France, for 2014.
9 Results of IAG Officers elections
The chair of the Nominating Committee (NC), M. Sideris,gave a detailed overview on the nomination process. The
NC was appointed in spring 2014, consisting of S. R. C. deFreitas, Brazil, Y. Fukuda, Japan, B. Heck, Germany, andM. G. Sideris, Canada. In August 2014, a letter with a“Call for Nominations for IAG Officers 2015-2019” wassent to the electoral register according to Delegates of IAG
Adhering Bodies, IAG Officers, Fellows, and members.
The elected positions are the IAG President, Vice
President, Secretary General, Presidents of Commissions(4), Service Representatives (3), Members at Large (2),and the President of the COB.
A total of 55 names were nominated for all positions.
The elected officers to the IAG Executive Committee forthe period 2015-2019 are:

Summary of the IAG Executive Committee Sessions

x President: H. Schuh, Germany;x Vice-President: Z. Altamimi, France;
x Secretary General: H. Drewes, Germany;x President of the COB: J. Ádám, Hungary;x President of Commission 1: G. Blewitt, USA;x President of Commission 2: R. Pail, Germany;x President of Commission 3: M. Hashimoto, Japan;
x President of Commission 4: M. Santos, Canada;
x Members-at-Large 1: L. Combrinck, South Africa;
x Members-at-Large 2: M. C. Pacino, Argentina;
x Service Representative 1: R. Neilan, USA;x Service Representative 2: R. Barzaghi, Italy;
x Service Representative 3: A. Nothnagel, Germany.
In order to balance the geographical distribution of the
EC members, M. Sideris proposed that the Members-atLarge get elected after the election of the other officers.
10 Report on the review of the IAG Statutes andBylaws (Cassinis Committee)

973

x Commission 2 “Gravity Field”: After presenting the
research work, U. Marti proposed to publish no longer
printed proceedings of small conferences under thecurrent conditions. Finally he presented proposals for
two IAG Resolution “International Height Reference
System” and “International Gravity Reference System”.
x Commission 3 “Earth Rotation and Geodynamics”: R.
Gross reported on the activities of Sub-commissionsand Working Groups, especially the past and future
symposia. For the future he proposed a Sub-commission
on “Vertical motion of the Earth’s crust and sea levelchange”.
x Commission 4 “Positioning and Applications”: D.
Grejner-Brzezinska reported about numerous meetings.
For the future she suggested to split SC4.3 into two
subjects – one related to the troposphere and the otherone to the ionosphere. Moreover a new SC for
ionosphere study and modelling should be established.
13 Report and recommendations of the ICCTOn behalf of the Cassinis Committee, M. Sideris presented
viewgraphs with all the paragraphs of the IAG Statutes andBylaws to be changed. He emphasised that this update wasnecessary in order to make it more clear and consistent,
and to adapt it to the present situation. He reviewed the
major updates in detail. The texts will be discussed in the
IAG Council in its first session; the final approval will bemade after eventual changes in the second session.
11 Status of IAG Report 2011 – 2015 (Travaux del’AIG 2011 – 2015)
H. Drewes presented an overview of the current volume of
the IAG Reports 2011-2015 (Travaux de l’AIG Vol. 39)
and emphasised the importance to publish detailed reportsof all IAG components in order to inform the geodetic
community and as documentation for the future. It is now
online (http://iag.dgfi.tum.de/index.php?id=329); andhardcopies are available on request.
12 Reports and recommendations of the Commissions
H. Drewes explained that recommendations for the future
should be made. Close contacts between old and newpresidents are necessary to guarantee continuous activities.
x Commission 1 “Reference Frames”: T. van Dam
outlined the activities of the Sub-commissions andWorking Groups mentioning the most important
publications and the organised symposia andworkshops. As a general recommendation for the future
work she called on the geodetic community to facilitate
more inter-technique and modelling discussions.

N. Sneeuw summarised the activities of the 9 ICCT Joint
Study Groups. A remarkable event was the Hotine-Marussi
Symposium, Rome 2013 “in honour of Fernando Sansò”
for his long involvement in the organisation and hisleadership role in Theoretical Geodesy. For the future hesuggested the ICCT to be re-structured from a temporary toa permanent IAG component with full rights in the EC.
14 Appointment of the ICCT President for 2015 – 2019
According to the present Bylaws, the new ICCT President
has to be appointed by the IAG EC. N. Sneeuw proposed tonominate the present ICCT Vice-President P. Novák,
Czech Republic. After a short discussion the EC accepted
unanimously the proposal.
15 Report and recommendations of the Services’
representatives
R. Barzaghi presented the activities of the gravity field
related Services, i.e. IGFS, BGI, ISG, ICGEM, ICET and
IDEMS. He mentioned the Symposium GGHS, Venice,
Italy, 2012 and the IGFS General Assembly, Shanghai,
China, 2014. A project for detailed geoid estimation in the
Mediterranean (GEOMED II) was submitted to ESA. It isplanned to merge the International Center for Earth Tides(ICET) with the Global Geodynamics Project (GGP) to an
International Geodynamics and Earth Tide Service(IGETS). The International Digital Elevation Model
Service (IDEMS) is not active at present; there areproposals to revive it.

974

16 Adoption of the International Geodynamics andEarth Tide Service (IGETS) & new ToR of the IDS
H. Drewes presented a letter of J. P. Boy, EOST/IPGS,
Strasbourg, France, to establish the new IGETS. The draft
ToR were discussed. H. Schuh said that for years a net ofsuper-conducting gravimeters has been installed, so thisactivity should receive the best organisational support. The
EC unanimously adopted the proposal. H. Drewes
presented then the revised ToR of the IDS. After a short
discussion they were unanimously adopted.
17 Status of the IAG Services Assessment
H. Drewes mentioned that all comments of the ISA Teamto answers of the Services on a distributed questionnaire
have been collected and merged together into each one filewhich was sent to the individual Services. From someServices a response was received. Ch. Rizos emphasised tocontact these Services once more. H. Schuh proposed thatthe presently acting ISA Team chaired by Ch. Rizos should
continue its work at least for the next 6 – 9 months. He
announced to formulate guidelines on how to proceed.
18 Report and recommendations of GGOS andadoption of the new GGOS ToR
H. Kutterer presented the status of the GGOS development
and the new ToR. The GGOS Consortium has to beelected; the proposals are expected till end of July 2015. H.
Schuh emphasised that the re-organisation should now becompleted and the practical work be started. R. Gross
remarked that GGOS could probably accomplish a minor
part of all its tasks; in fact the whole work only can bedone within a co-operation of all groups within the IAG.
19 Appointment of the GGOS Chair for 2015 – 2019
According to the IAG Bylaws (§ 15.d), the GGOS Chair is
appointed by the IAG EC in consultation with GGOS CB.
Ch. Rizos informed that H. Kutterer has announced to beready for a second term. Thus he proposed to nominate
him again. T. Herring seconded and the EC unanimously
accepted the proposal. It was proposed to bring up newissues into the concept of GGOS. The new EC shouldreflect on this topic and formulate it for its next meetings.

H. Drewes, H. Hornik

order to enable the COB to generate the output to the IAG
community but also to the community interested in geoscience in general as actual as possible.
21 Report of the Journal of Geodesy Editor-in-Chief
R. Klees reported on the development of the JoG in the
recent period. The JoG has proved to be one of the mostsuccessful journals in geo-sciences. He presented
viewgraphs showing the excellent position of the JoG, e.g.
related to the impact factor, the authors’ satisfaction, thenumber of submissions, the internationality of the authors.
The time span between the submission of articles and final
publication could be decreased. R. Klees mentioned that
the JoG has become a member of COPE (Committee on
Publication Ethics). The statistics of downloaded articles
shows that the readers are also very interested in reading
articles on “old fashioned themes”.
22 Proposal of the new Board of Editors of Journal of
Geodesy by the present Board
R. Klees presented a proposal for the new Editorial Board.
J. Kusche, Germany, was nominated as the new Editor-inChief. For some Board positions experts are still to befound. H. Drewes remarked that the majority of papers
dealing with earthquake induced displacements and related
themes are mostly published in geophysical journals. The
attractiveness of the JoG for such articles could probably
be improved if a specialist in this field would be memberof the Editorial Board.
23 Report of the Assistant Editor of IAG Symposia Series
P. Willis informed that 6 volumes in the IAG Symposia
Series have been published in the recent period, 5 others
are in progress. As achievements he mentioned theinstallation of a Springer submission website, the generally
improved review process, and more international
participation concerning both authors and reviewers and inparticular the changed publication procedures fromvolume-to-volume to paper-to-paper with DOI. The EC
discussed the delay of publication and expressed theopinion that 3 months between submission and publication
should be sufficient and 6 months at the maximum.
Session II: Friday, June 26, 2015, 18:00 – 20:00

20 Report of the COB
J. Adám mentioned in particular the maintenance of the
IAG Website and the IAG Newsletter. Again he invited allcolleagues to contribute permanently in every matter in

24 Proposal for an (electronic) series
proceedings (not as strictly reviewed)
The topic was shifted to the new EC 2015-2019.

of

IAG

Summary of the IAG Executive Committee Sessions

25 Report on developing countries
H. Drewes presented the report on activities in Latin
America and the Caribbean compiled by C. Brunini. The
majority of the work was in context with the tasks
described in IAG SC 1.3b “Reference Frames for Central
and South America” as well as SC 2.4b “Geoid andGravity Field in South America”. The report also
highlights the transfer of TIGO (Transportable Integrated
Geodetic Observatory) from Concepcion, Chile to La
Plata, Argentina, now named AGGO (Argentina – German
Geodetic Observatory). The German Bundesamt für
Kartographie und Geodäsie (BKG) is still supporting theoperating considerably, but in future Argentina should
operate the system self-employed.
26 Report on JBGIS (FIG, ISPRS, …)
Ch. Rizos as the chair of the Joint Board of Geospatial
Information Societies (JBGIS) gave a report. Previously
JBGIS represented more a loose “club” of geo-orientatedinstitutions. However, at the meeting 2013 in Potsdam,
Germany, it was decided to come to definite actions inparticular using the much knowledge besides of geodesy
assembled in JBGIS. H. Schuh proposed to nominate Ch.
Rizos again as the IAG delegate in JBGIS. H. Drewes
seconded, and the EC unanimously accepted the proposal.
27 Reports on liaised bodies (ABLOS, IAU Comm. 19,
GEO, ISO, UN)
The 2014 Annual Report on the activities of ABLOS waspresented by H. Drewes and Ch. Rizos.
28 Appointment of IAG Representatives to Services,IUGG Commissions and Groups, and other bodies
H. Drewes showed the recent list of representatives in theliaised bodies ABLOS (Advisory Board on the Law of theSea), IAU (International Astronomical Union) formerly
Commission 19, now Commission A2, GEO (Group ofEarth Observations), ISO (International Organisation forStandardisation) and UN (United Nations). The EC
discussed the nomination of new delegates. Ch. Rizos
interjected that this topic should be a task of the new EC,
thus it was decided to shift this topic to the new EC.
29 Venue of the IAG Scientific Assembly 2017 (Status
report of applications)
H. Drewes informed that according to the IAG Bylaws it is
up to the Council to decide on the venue of IAG Scientific

975

Assemblies. For the next one in 2017 only one application
was submitted. The Geodetic Society of Japan invites tohold the Assembly from July 30 – August 4, 2017 in Kobe,
Japan. It is planned to hold it together with IASPEI as a
“Joint IAG-IASPEI Scientific Assembly”.
30 Any other business
There were no other items.
Session III: Monday, June 29, 2015, 18:00-20:00
31 Actual status report
Ch. Rizos summarised the EC meetings of June 23 and 26,
and reported on the latest IUGG EC meeting (June 28) andIUGG Council meeting (June 29).
The IUGG Resolution Committee received 8
Resolutions, 3 of them submitted by the IAG: (1) Future
Satellite Gravity and Magnetic Mission Constellations, (2)Global Geodetic Reference Frame, (3) Real-Time
Augmentation of the Tsunami Early Warning System.
The IUGG Council also elected the new IUGG officers.
M. Sideris was elected as the new IUGG President, Ch.
Rizos as Bureau Member, J. Krynski, and V. Tiwari, Polishand Indian IAG Delegates, were elected members of the
IUGG Finance Committee. The following IAG associates
were elected IUGG Liaison Officers: B. Richter(CODATA), G. Blewitt (COSPAR), R. Neilan (WDS), H.
Drewes (UN-GIS), R. Biancale and C. Boucher (CCTF), L.
Sánchez (PAIGH), C. Boucher and H. Kutterer (GEO).
32 Approval of the new Board of Editors of the Journalof Geodesy (JoG)
According to the IAG Bylaws (§19), the current JoG
Editorial Board appoints the new Board. The new Board
nominates the new Editor-in-Chief for the next period.
The appointments and the nomination have to be approvedby the IAG Executive Committee. The nominated Board
members are: S. Bettadpur, USA; C. Brunini, Argentina; T.
van Dam, Luxembourg; D. Dong, China; Y. Gao, Canada;
T. Hobiger, Sweden; A. Hooper, UK; C. Huang, China; A.
Jaeggi, Switzerland; W. Keller, Germany; M. King,
Australia; Z. Malkin, Russia; B. Meyssignac, France; R.
Riva, The Netherlands; W.-D. Schuh, Germany; I. Tziavos,
Greece; S. Verhagen, The Netherlands; M. Vermeer,
Finland; P. Wielgosz, Poland; and P. Xu, Japan. The
nominated Editor-in-Chief is J. Kusche, Germany. After ashort discussion H. Drewes moved to approve the complete
Board, the Editor-in-Chief. C. Rizos seconded, and it was
unanimously adopted.

H. Drewes, H. Hornik

976

33 Approval of the Editor-in-Chief of the IAG
Symposia Series and an assistant Editor in Chief
The Editor of the IAG Symposia Series was hitherto the
IAG President ex officio. Ch. Rizos nominated P. Willis as
the Assistant Editor. The new IAG Bylaws established an
Editor-in-Chief and assistant Editor-in-Chief. The present
editors proposed J. Freymueller and L. Sánchez for these
positions. H. Schuh moved giving this proposal to the new
EC, Ch. Rizos seconded, and it was unanimously adopted.

38 Status of reviewed Statutes and Bylaws
H. Schuh gave a report on the review of the IAG Statutes
and Bylaws as a member of the Committee. The draft
versions were discussed in the Council and in detail withsome Council members. There were some small additionalchanges, but the general structure and contents was not
modified. The final version will be forwarded to theCouncil to be approved at its next meeting.
39 Sponsorship of symposia and workshops

34 IAG Budget 2015 – 2018
H. Drewes presented his draft IAG Budget for the period
2015-2018 to be adopted at the next Council meeting. It isbased on the financial report 2011-2014 which wasreviewed by the Audit Committee during the last days (seenext agenda item). The total expenditures were increased
with respect to the budget 2011-2014 because of a large
surplus in the present period and a current high net capital.
35 Summary of the Report of the Audit Committee

H. Drewes presented the list of proposed symposia andworkshops. According to a decision of the present EC, allmeetings organised by at least one IAG component or two
sub-components are automatically adopted. A proposal forsponsorship of “GEODATA 2016” in Argentina notsupported by two sub-components was discussed. As it isdirected to practical topography, cartography, geomatics,
photogrammetry, and cadastre, and includes neither
gravimetry and geoid (SC2.4b) nor reference frames issues(SC1.3b) the sponsorship was unanimously rejected.
40 Preparation of the IAG Closing Session

The Audit Committee established by the IAG Council
examined the receipts and bank statements of the IAG
account for 2011-2014, checked the balances, examinedthe expenditures, and ensured the conformity with thebudget 2011-2014. The Committee also examined the
proposed budget for 2015-2018. H. Drewes presented thewritten IAG Audit Committee Report dated June 29, 2015
with the approval of the financial report 2011-2014 and thebudget 2015-2018. C. Rizos moved to adopt this report, H.
Schuh seconded, and it was unanimously approved.

H. Drewes presented the agenda of the IAG Closing
Session. Traditionally the convenors of IAG led symposia
at the General Assembly give a short summary (5 min), theIAG Resolutions and the new IAG Fellows are presented,
and the new IAG President gives his inaugural speech. H.
Drewes was asked to send the list of IAG Fellows to the
EC members and to ask J. Freymueller to explain theprocedure of the proceedings of the IAG Symposia.

36 Report of the IAG Resolution Committee

41 Any other business

R. Barzaghi reported as a member of the IAG Resolution
Committee on the procedure. The two submitted IAG
Resolutions were discussed in the Committee. He
presented the final versions after some changes in the
structure and wording. Ch. Rizos thanked the members of
the Resolution Committee for their excellent work.

There were no other items.

37 Discussion of proposed resolutions for approval by
the IAG Council
The two proposed IAG Resolutions were discussed by theEC, and some minor changes were included. H. Drewes
moved to accept the slightly modified versions and to
forward them to the IAG Council for adoption. Ch. Rizos
seconded, and the Resolutions were unanimously approvedfor submission to the IAG Council.

42 Appointment of Ch. Rizos to IAG Honorary President
H. Drewes moved to appoint Ch. Rizos to an IAG
Honorary President in order to dignify his excellent
presidency during the period 2011-2015. H. Schuhseconded and the appointment was unanimously approved
with sustained applause of the EC members.
43 Closing the EC of the legislative period 2011 – 2015
Ch. Rizos thanked all the EC members for their greatcooperation during the last four years connected with hisbest wishes for their future work. He closed the session,and thereby the IAG legislative period 2011-2015.

IUGG Resolutions

977

IUGG Resolutions at the XXVI General Assembly 2015

Resolution 1: Role of Ocean in Climate
The International Union of Geodesy and Geophysics
Considering
The important role of the ocean in the whole Earth system,in particular its interactions with the atmosphere, at all
time-scales,
Acknowledging
x That this fact must be properly translated into modeling,either for operational oceanography or for study of the
Earth climatic system and that the use of these models
for estimating relevant states (past, present or future)requires specific observations,x Quantities related to physical oceanography are offundamental importance for research related tobiological or environmental aspects of the ocean (forinstance ocean acidification and deoxygenation) or forsocietal impact (sea level),
Noting
The recommendations
conferences,fromrecentinternational

Urges
x All countries to contribute through international
cooperation and coordination to establish adequate andsustainable observing systems, ensuring high quality
observations of the ocean on long time scales,
x Relevant international organizations such as theIntergovernmental Oceanographic Commission (IOC)and the Group on Earth Observations (GEO) to work
together to reach the previous objectives,

Resolves
To continue and amplify national and international
research efforts on the proper modeling of the ocean inclimatic systems and to contribute fully to societal
investigations related to this topic.

Resolution 2: Future Satellite Gravity andMagnetic Mission Constellations
The International Union of Geodesy and Geophysics
Considering− The interest and need of the IUGG scientific community
to understand processes of global mass transport in the
Earth system, and the interaction among its subsystems
including continental hydrology, cryosphere, atmosphere,
ocean and solid Earth, in order to close the global water
budget and to quantify the climate evolution of the Earth,− The long lead time required to bring an earth observation
system into operation,
Acknowledging
x The experience acquired in the last decade within the
IUGG in analyzing data from dedicated satellite
missions such as CHAMP, GRACE, GOCE and Swarmfor the purpose of estimating the gravity and magnetic
fields and their time variations,x The clear expression of need from the user communities
so far, and the definition of joint science and user
requirements for a future satellite gravity field mission
constellation by an international working team under theumbrella of IUGG,

978Notingx The need for a long-term sustained observation of thegravity and magnetic fields and related mass transport
processes of the Earth beyond the lifetime of GRACE
and the GRACE Follow-On planned for the 2017 - 2022
period, and beyond the lifetime of Swarm, currently
2013 to 2018,
x The demonstrated need for satellite constellations toimprove temporal and spatial resolution and to reduce
aliasing effects,
Urges
x International and national institutions, agencies andgovernmental bodies in charge of supporting Earthscience research to make all efforts to implement longterm satellite gravity and magnetic observation
constellations with high accuracy that respond to theaforementioned need for sustained observation.

Resolution 3: Global Geodetic Reference Frame

XXVI IUGG General Assembly

Resolution 4: Real-Time GNSS Augmentationof the Tsunami Early Warning
SystemThe International Union of Geodesy and Geophysics
Consideringx That large populations may be impacted by tsunamis
generated by megathrust earthquakes,
x That among existing global real-time observational
infrastructure, the Global Navigation Satellite Systems(GNSS) can enhance the existing tsunami early warning
systems,
Acknowledging
The need to coordinate with the UNESCO
Intergovernmental Oceanographic Commission (IOC) andthe established intergovernmental coordination framework
to define GNSS network requirements, data sharing
agreements and a roadmap for the development andintegration of the GNSS tsunami early warning
augmentation.

The International Union of Geodesy and Geophysics
Consideringx The significant efforts of the International Associationof Geodesy in developing and maintaining fundamental
geodetic products for scientific and societal benefits, inparticular through its Global Geodetic Observing
System (GGOS),
x The achievements realized by the UN Global Geospatial
Information Management (GGIM) through its Working
Group on Global Geodetic Reference Frame (GGRF), in
which IUGG played a significant role through its
International Association of Geodesy,
Recognizing
The adoption in February 2015 by the General Assemblyof the United Nations of a resolution entitled “A Global
Geodetic Reference Frame for Sustainable Development”,
Urges
The UN GGIM GGRF Working Group to engage with the
IUGG and other concerned organizations such as theCommittee of Earth Observation Satellites (CEOS) and theGroup on Earth Observations (GEO), in order to promote
the implementation of the UN GGIM GGRF RoadMap,
Resolves
To support the implementation of the intent of the UN
resolution.

Urges
x Operational agencies to exploit fully the real time
GNSS capability to augment and improve the accuracy
and timeliness of their early warning systems,x That the GNSS real-time infrastructure bestrengthened,x That appropriate agreements be established for the
sharing of real-time GNSS data within the tsunami
early warning systems,
x Continued support for analysis and production ofoperational warning products,
Resolves
x Operational to engage with IUGG member states topromote a GNSS augmentation to the existing tsunami
early warning systems.
x Initially to focus upon the Pacific region because thehigh frequency of tsunami events constitutes a large
risk to the region’s large populations and economies,by developing a prototype system, together withstakeholders, including scientific, operational, andemergency responders.

IUGG Resolutions

979

Resolution 5: Geo-Energy Resources

Resolution 6: Geoscience Cooperation

The International Union of Geodesy and Geophysics

The International Union of Geodesy and Geophysics

Considering
The challenges posed to our planet by climate change, andthe international efforts to transition in the next decades
towards a low-carbon economy with the aim to limit the
global warming to within 2°C with respect to the 18501900 average,

Notingx The increasingly cross-disciplinary nature of geoscience
research means that fields that once were distinct now
overlap in interests,
x That many important problems in geosciences require
the integration of geodesy, geology, geophysics, andother geoscience fields,x That the IUGG and other geoscience unions are able toserve as a focal point for many of these common
interests,
x That the International Union of Geological Sciences has
suggested exploring the possibility of organizing a joint
geoscientific assembly,

Notingx The crucial role of new renewable energy and electricity
sources for the future energy strategy and climatechange control,x The invaluable contribution that science can bring todevelop scenarios and identify new technologies andsolutions enabling the required transition to a lowcarbon economy,x The challenges posed by the global exploitation of georesources, including issues such as induced/triggered
seismicity, environmental contamination, and resource
supply,Recognizing
x The Future Earth initiative of the International Council
for Science,x The unique competence of IUGG in climate change
consequences as well as renewable geo-resources
fundamental for the future energy supply, includinghydropower, wind and geothermal energy, and to study
scientifically the challenges and risks associated withthe exploitation and extraction of new renewables
sources of energy and electricity.
Urges
International and national institutions, agencies andgovernmental bodies to support scientific advancement and
new knowledge development in the field of geo-resources,
Resolves
To promote and coordinate scientific contributions needed
to limit the impact of climate change and enable thetransition to a future low-carbon economy, and to adopt aholistic view covering all aspects from geo-resources toconsequences and risks.

Resolves
x To enhance cooperation and exchange with the othergeoscience unions by expanding the formation of joint
working groups or commissions,x To explore the organization of a joint geoscientificassembly.

XXVI IUGG General Assembly

980

Resolution 7: International Scientific Activities
and Cooperation
The International Union of Geodesy and Geophysics,
ConsideringThat opportunities to undertake, evaluate, and applyinternational scientific research on environmental extremes
and their associated impacts useful to society are growing,necessitating and justifying increased support in order toprovide maximum benefits for society in both the near- andlong-term,
Acknowledging
The need to continue the extensive existing efforts toenhance the worldwide availability of vital information
about the global environment, especially throughmonitoring, service, and commission-focused research
efforts and activities,
Noting
The increasing world-wide occurrence and intensities ofenvironmental problems and the disruptions to overall
economic well-being and development that have been andcould be caused by natural hazards and extremes and theneed to be prepared for the increasing potential for new
threats to emerge,
Urges
x National and scientific leaders of all nations torecognize the substantial benefits to overall well-being
and economic progress, both nationally and globally,that will accrue through advancing scientificunderstanding of and capabilities for predicting
potentially disruptive environmental consequences andextremes,x National and scientific leaders of all nations to support
the active participation of the members of theirscientific community in the collective international
effort being undertaken by the IUGG and associatedscientific unions within ICSU to strengthen and apply
research capabilities and findings for public and general
economic benefit and the coordination activities
necessary to accomplish such efforts,
x Scientists and experts around the world to re-dedicate
their efforts better to understand the Earth system and,in this time of increasing stress on the global
environment, to make their findings available to the
public in the most useful and appropriate ways,

Resolves
To be steadfast in: (1) encouraging and supporting theparticipation of scientists in international scientificmeetings and activities, (2) undertaking efforts to enhancefundamental understanding of geophysical processes andbehavior, especially in the grand challenge areas, (3)increasing efforts to utilize scientific understanding for the
benefit of society and the environment and for promotionof the economy and societal resilience; and (4) inproviding an independent voice in support of undertaking
and relying on the most rigorous and well-tested scientificfindings.

Resolution 8: Thanks
The International Union of Geodesy and Geophysics
Resolves
Gratefully to record its appreciation for the organization,
arrangements, and hospitality at the XXVI General
Assembly. On behalf of all participants, the Council
expresses its warm thanks to the Deputy Prime Minister for
Science Research and Innovations, the Mayor of Prague
and the President of the Academy of Sciences of the Czech
Republic, the Local Organizing Committee, the Scientific
Program Committee, and all others for making the XXVI
General Assembly a scientific success in the beautiful cityof Prague.

IAG Resolutions

981

IAG Resolutions at the XXVI IUGG General Assembly 2015

Resolution 1: Definition and Realization of anInternational Height Reference
System (IHRS)The International Association of Geodesy,
Recognizing thatx to determine and to investigate the global changes of the
Earth, the geodetic reference systems with long-term
stability and worldwide homogeneity are required;x to detect sea level change of a few millimeters per year
can only be possible when a stable spatial referencewith globally high accuracy over a long period of timeis realized; for this purpose, an integrated global
geodetic reference frame with millimeter accuracy must
be implemented; to reach this goal, the inconsistencies
existing between analysis strategies, models, andproducts related to the Earth's geometry and gravity
field must be solved;
x to accomplish both definition and realization of a heightreference system (HRS) standards and conventions thatallow a consistent definition and a reliable realization
are required;
Notingx the results of the GGOS Theme 1 investigations for thedefinition and realization of an International Height
Reference System in particular the conventions and thecomputations of the height reference level as thepotential value W0 at the geoid based on the newest
global gravity field and sea surface models;x the necessity of ensuring the reproducibility andinterpretability of the reference value, the procedure
applied for the determination of W0 must be well
documented including conventions and guidelines;

Resolves
x the following conventions for the definition of anInternational Height Reference System (see note 1):
1. the vertical reference level is an equipotential surfaceof the Earth gravity field with the geopotential value
W0 (at the geoid);
2. parameters, observations, and data shall be related tothe mean tidal system/mean crust;
3. the unit of length is the meter and the unit of time isthe second (SI);
4. the vertical coordinates are the differences -'WP
between the potential WP of the Earth gravity field at
the considered points P, and the geoidal potential
value W0; the potential difference -'WP is also
designated as geopotential number CP: -'WP = CP =W0 - WP;
5. the spatial reference of the position P for the potential
WP = W(X) is related as coordinates X of theInternational Terrestrial Reference System;
x W0 = 62636853.4 m2s-2 as realization of the potential
value of the vertical reference level for the IHRS (seenote 2)

Note 1: Ihde J., Barzaghi R., Marti U., Sánchez L., SiderisM., Drewes H., Foerste Ch., Gruber T., Liebsch G., Pail
R.: Report of the Ad-hoc Group on an International
Height Reference System (IHRS); In: IAG Reports
2011-2015(Travaux
de
l’AIG
Vol.
39),
http://iag.dgfi.tum.de/index.php?id=329.
Note 2: Report of Joint Working Group 0.1.1: Vertical
Datum Standardization (JWG 0.1.1); In: IAG Reports
2011-2015 (Travaux de l’AIG Vol. 39), GGOS, 402404, http://iag.dgfi.tum.de/index.php?id=329.

982

Resolution 2:Establishment of a global
absolute gravity reference
systemThe International Association of Geodesy,
Consideringx That the time variable gravity field is one of the keys tounderstanding the changing Earth,x That the accuracy of modern absolute gravimeters has
significantly improved,x That absolute gravity observation has become avaluable tool for monitoring crustal deformations andmass transports,
x That new observation principles and instruments likecold atom interferometers and ultra-precise clocks are inpreparation and testing,x That modern gravity observations need to be based upon
the International Metre Convention and the relevantmeasurement standards,
x That international comparisons of absolute gravimeters
under the auspices of International Committee for
Weights and Measures (CIPM) define the best
metrological realization,x That absolute gravity observations are archived anddistributed at global scale according to international
standards by the International Gravimetric Bureau(BGI) jointly with the Federal Agency for Cartography
and Geodesy (BKG) under the auspices of International
Association of Geodesy (IAG);
Acknowledging
x that the Strategy Paper between Metrology and Geodesy(see note 1) has been accepted by the IAG Executive
Committee;

XXVI IUGG General Assembly

Notingx That the International Gravity Standardization Net 1971
(IGSN71) no longer fulfills the requirements andaccuracy of a modern gravity reference thus requiring
replacement by a new global gravity reference system,x That measurement accuracies have improved from the“100 μGal” to the “few μGal” level,x That only with an improved gravity reference system
time-dependent gravity variations can be determinedwith high reliability,
x That the use of consistent standards and conventions isnecessary for the comparison of geometric andgravimetric observations in the framework of the Global
Geodetic Observing System (GGOS);
Resolves
x To adopt the Strategy Paper as the metrological basis
for absolute gravimetry,x To initiate a working group to compile standards for thedefinition of a geodetic gravity reference system based
upon the international comparisons of absolutegravimeters,x To establish a gravity reference frame by globally
distributed reference stations linked to the international
comparisons of absolute gravimeters where precise
gravity reference is available at any time,x To link the reference stations to the International
Terrestrial Reference System by co-location with spacegeodetic techniques,x To initiate the replacement of the International Gravity
Standardization Net 1971 (IGSN71) and the latest
International Absolute Gravity Base Station Network by
the new Global Absolute Gravity Reference System.

Note 1: Report of Commission 2: CCM – IAG Strategy for
Metrology in Absolute Gravimetry, Role of CCM and
IAG. In: IAG Reports 2011-2015 (Travaux de l’AIG Vol.
39 (http://iag.dgfi.tum.de/index.php?id=329).

Structure of the IUGG

983

Structures for the Period 2015 – 2019
International Union of Geodesy and Geophysics (IUGG)

Executive Committee

International Associations

BureauInternational Association of Cryospheric Sciences
President:
Charles Fierz (Switzerland)
President Elect: Regine Hock (USA)Secretary General: Andrew Mackintosh (New Zealand)

Michael Sideris (Canada)
Kathryn Whaler (UK)
Alik Ismail-Zadeh (Germany)
Aksel W. Hansen (Denmark)Isabelle Ansorge (South Africa)
Pierre Hubert (France)
Chris Rizos (Australia)

President:
Vice-President:
Secretary General
Treasurer:
Members:

Immediate Past President: Harsh Gupta (India)
Presidents of the International Associations
IACS 2015-2017:2017-2019:
IAG:
IAGA:
IAHS 2015-2017:2017-2019:
IAMAS:IAPSO:
IASPEI:
IAVCEI:Charles Fierz (Switzerland)
Regine Hock (USA)
Harald Schuh (Germany)
Eduard Petrovsky (Czech Republic)
Hubert Savenije (The Netherlands)
Günter Blöschl (Austria)
John Turner (UK)
Denise Smythe-Wright (UK)Thorne Lay (USA)Donald Dingwell (Germany)

Finance Committee
Chair:
Members:

David Collins (UK)Jan Krynski (Poland)
Corinna Risso (Argentina)
Virendra Tiwari (India)

International Association of Geodesy
President:
Harald Schuh (Germany)
Secretary General: Hermann Drewes (Germany)International Association of Geomagnetism and Aeronomy
President:
Eduard Petrovsky (Czech Republic)
Secretary General: Mioara Mandea (France)
International Association of Hydrological Sciences
President:
Hubert Savenije (The Netherlands)
President Elect: Günter Blöschl (Austria)
Secretary General: Christophe Cudennec (France)
International Association of Meteorology andAtmospheric Sciences
President:
John Turner (UK)
Secretary General: Teruyuki Nakajima (Japan)
International Association for the Physical Sciencesof the Oceans
President:
Denise Smythe-Wright (UK)
Secretary General: Stefania Sparnocchia (Italy)
International Association of Seismology andPhysics of the Earth’s Interior
President:
Thorne Lay (USA)Secretary General: Johannes Schweitzer (Norway)
International Association of Volcanology
and Chemistry of the Earth’s Interior
President:
Donald B. Dingwell (Germany)
Secretary General: Roberto Sulpizio (Italy)

984

Union Commissions and Working Groups
Union Commission on Climatic and Environmental
Changes (CCEC)
Chair:Tom Beer (Australia)
Secretary:
Keith Alverson (USA/Kenya)
Union Commission on Mathematical Geophysics(CMG)
Chair:
Yehuda Ben Zion (USA)Secretary:
Ilya Zaliapin (USA)Union Commission on Geophysical Risk andSustainability (GRC)
Chair:
Joan Marti (Spain)
Secretary General:
Paula Dunbar (USA)

Structures for the Period 2015-2019

Union Commission on Studies of Earth’s Deep Interior(SEDI)
Chair:
Jonathan Aurnou (USA)Secretary:
Michael Bergman (USA)Union Commission on Planetary Sciences (UCPS)
Chair:
Shuanggen Jin (China)
Secretary:
Scot Rafkin (USA)Union Commission on Data and Information (UCDI)
Chair:
Peter Fox (USA)Secretary:
Adelina Geyer Traver (Spain)
Working Group on History (WGH)
Chair:
Hans Volkert (Germany)
Vice Chair:
Claude Boucher (France)Structure of the IAG

985

International Association of Geodesy (IAG)

1. IAG Executive Committee
1.1 IAG Bureau
IAG President: Harald Schuh (Austria)
Vice President: Zuheir Altamimi (France)
Secretary Gen.: Hermann Drewes (Germany)
1.2 IAG Immediate Past President
Pres. 2007-2011: Chris Rizos (Australia)
1.3 IAG Commission Presidents
Commission 1: Geoffrey Blewitt (USA)Commission 2: Roland Pail (Germany)
Commission 3: Manabu Hashimoto (Japan)
Commission 4: Marcelo Santos (Canada)
1.4 Inter-Commission Committee on Theory (ICCT)ICCT President: Pavel Novák (Czech Republic)
1.5 Global Geodetic Observing System (GGOS)
GGOS Chair:Hansjoerg Kutterer (Germany)
1.6 Communication & Outreach Branch (COB)
COB President: József Ádám (Hungary)
1.7 Representatives of the Services
Representatives: Riccardo Barzaghi (Italy)
Ruth Neilan (USA)Axel Nothnagel (Germany)
1.8 Members-at-Large
Members:
Ludwig Combrinck (South Africa)
Maria Cristina Pacino (Argentina)
1.9 Non-voting Members
Assistant Secretary: Franz Kuglitsch (Germany)

IAG Past Presidents (before 2011)
1979-1983:
Helmut Moritz (Austria)
1987-1991:
Ivan I. Mueller (USA)
1991-1995:
Wolfgang Torge (Germany)
1999-2003:
Fernando Sansó (Italy)
2003-2007:
Gerhard Beutler (Switzerland)
2007-2011:
Michael G. Sideris (Canada)
IAG Past Secretaries General
1975-1991:
Michel Louis (France)
1991-1995:
Claude Boucher (France)

2. IAG OfficeDeutsches Geodätisches Forschungsinstitut derTechnischen Universität München
Director:
Hermann Drewes (Germany)
Assist. Secretary: Franz Kuglitsch (Germany)
Treasurer:
Wolfgang Küffner (Germany)

3. IAG Communication & Outreach Branch
Budapest University of Technology and Economics
President:
József Ádám (Hungary)
Secretary:
Szabolcs Rózsa (Hungary)
Newsletter Editor: Gyula Tóth (Hungary)

4. Journal of Geodesy
Editor in Chief: Jürgen Kusche (Germany)

5. IAG Symposia Series
Editor in Chief: Jeff Freymueller (USA)Assistant Editor: Laura Sánchez (Germany)

Structures for the Period 2015-2019

986

6. IAG Commissions
Commission 1: Reference Frames
President:
Geoffrey Blewitt (USA)Vice-President: Johannes Böhm (Austria)
Commission 2: Gravity Field
President:
Roland Pail (Germany)
Vice-President.: Shuanggen Jin (China)
Commission 3: Earth Rotation and Geodynamics
President:
Manabu Hashimoto (Japan)
Vice-President: Cheng-Li Huang (China)
Commission 4: Positioning and Applications
President:
Marcelo Santos (Canada)
Vice-President: Allison Kealy (Australia)

7. IAG Inter-Commission Committee on Theory
ICCT President: Pavel Novák (Czech Republic)
Vice-President: Mattia Crespi (Italy)

8. IAG Global Geodetic Observing System
GGOS Chair:Vice-Chair:Hansjörg Kutterer (Germany)
Ruth Neilan (USA)

9. IAG Scientific Services
International Bureau of Weights and Measures,(Bureau International des Poids et Mesures, BIPM)
Time Department
Director:
Elisa Felicitas Arias (France)
International Earth Rotation and Reference Systems
Service (IERS)
Chair of Directing Board: Brian Luzum (USA)
Director Central Bureau: Daniela Thaller (Germany)International DORIS Service (IDS)
Chair Governing Board: Pascal Willis (France)
Director Central Bureau: Laurent Soudarin (France)

International GNSS Service (IGS)
Chair of the Gov. Board: Gary Johnston (Australia)
Director Central Bureau: Ruth Neilan (USA)International Laser Ranging Service (ILRS)
Chair Governing Board: Guiseppe Bianco (Italy)
Director Central Bureau: Michael Pearlman (USA)International VLBI Service for Geodesy andAstrometry (IVS)
Chair Directing Board: Axel Nothnagel (Germany)
Director Coordinat. Ctr: Dirk Behrend (USA)International Gravity Field Service (IGFS)
Chair:
Riccardo Barzaghi (Italy)
Director Central Bureau: Georgios Vergos (Greece)
International Centre for Global Earth Models(ICGEM)
Director:
Franz Barthelmes (Germany)International Digital Elevation Models Service(IDEMS)
Director:
Kevin M. Kelly (USA)International Geodynamics and Earth Tide Service(IGETS)
Chair:
Hartmut Wziontek (Germany)
Director Central Bureau: Jean-Paul Boy (France)
International Gravimetric Bureau,(Bureau Gravimetrique International, BGI)
Director:
Sylvain Bonvalot (France)
International Service for the Geoid (ISG)
President:
Mirko Reguzzoni (Italy)
Director:
Giovanna Sona (Italy)
Permanent Service for Mean Sea Level (PSMSL)
Director:
Lesley Rickards (UK)Commission 1 – Reference Frames

987

Commission 1 – Reference Frames
President: Geoffrey Blewitt (USA)Vice President: Johannes Böhm (Austria)
http://iag.geo.tuwien.ac.at/c1/

Terms of Reference
Reference systems and frames are of primary importancefor much Earth science based research and applications,satellite navigation as well as for practical applications in
geo-information. A precisely defined reference frame isneeded for an improved understanding of the Earth’s
rotation and its gravity field, sea level change with time,
tectonic plate motion and deformation, glacial isostatic
adjustment, geocentre motion, deformation due to Earthquakes, local subsidence and other crustal displacements.
Commission 1 activities and objectives deal with thetheoretical aspects of how best to define reference systems
and how reference systems can be used for practical andscientific applications. Commission 1 will closely interact
with the other IAG Commissions, ICCT, Services and
GGOS components where reference system aspects are ofconcern. Commission 1 is identical with Sub-commission
B2 of COSPAR.

Objectives
x Definition,
establishment,
maintenanceandimprovement of the geodetic reference frames;
x Advanced terrestrial and space observation techniquedevelopment for the above purposes;
x International collaboration for the definition and deployment of networks of terrestrially-based space geodetic
observatories;
x Theory and coordination of astrometric observation forreference frame purposes.
x Collaboration with space geodesy/reference frame
relatedinternational
services,
agenciesandorganizations;x Promote the definition and establishment of verticalreference systems at global level, considering theadvances in the regional sub-commissions;x Work to maintain a reference frame that is valuable for
global change studies

Structure
Sub-Commissions
SC 1.1: Coordination of Space Techniques
Chair: Urs Hugentobler (Germany)
SC 1.2: Global Reference Frames
Chair: Xavier Collilieux (France)
SC 1.3: Regional Reference Frames
Chair: Carine Bruyninx (Belgium)
SC 1.3a: Europe
Chair: Markku Poutanen (Finland)
SC 1.3b: South and Central America
Chair: William Martinez (Colombia)
SC 1.3c: North America
Chair: Michael Craymer (Canada)
SC 1.3d: Africa
Chair: Elifuraha Saria (Tanzania)
SC 1.3e: Asia-Pacific
Chair: John Dawson (Australia)
SC 1.3f: Antarctica
Chair: Martin Horwath (Germany)
SC 1.4: Interaction of Celestial and Terrestrial Reference
FramesChair: Zinovy. Malkin (Russia)

Structures for the Period 2015-2019

988

Joint Study Groups

Program of Activities

JSG 0.22:

Definition of Next Generation Terrestrial
Reference Frames(joint with ICCT, description see ICCT)
Chair: Christopher Kotsakis (Greece)

JSG 3.1:

Intercomparison of Gravity and Height
Changes(joint with IGFS, Commissions 2 and 3,
description see Commission 3)
Chair: Severine Rosat (France)

The program of activities for Commission 1 includes:x Theoretical and applied research activities related toreference frames;
x Research and development activities that impact thereference frame determination and its accuracy, as wellas, the best and optimal usage of reference frames inEarth Science applications;x Interaction with all established IAG Services: IVS, IGS,ILRS, IDS and the IERS, including their Combination
Centres and Working Groups;
x Development in the theory and application of thetransformation between Celestial and Terrestrial
Reference Systems and application of the theory to
improve the consistency between ICRF, ITRF and
EOPs, in cooperation with IVS and IERS;
x Exploration of advanced methodologies for the
combination of products and raw observations of space
geodetic techniques;x Investigation of systematic error sources and factors
limiting the precision of space geodetic techniques andtheir combination;x Encouraging and assisting regional sub-commission
countries to re-define and modernize their national
geodetic systems so that they are compatible with the
ITRF;
x Establishment of a dedicated Web site relating all
Commission 1 activities.

Joint Working Groups
JWG 0.1.2: Strategy for the Realization of the International
Height Reference System (IHRS)(joint with GGOS, Commission 2 and IGFS,
description see GGOS)
Chair: Laura Sanchez (Germany)
JWG 1.1:

Site Survey and Co-location(joint with the IERS)
Chair: Sten Bergstrand (Sweden)

JWG 1.2:

Modelling Environmental Loading Effects for
Reference Frame Realizations(joint with the IERS)
Chair: Tonie van Dam (Luxembourg)

JWG 1.3:

Troposphere Ties
(joint with Commission 4)
Chair: Robert Heinkelmann (Germany)JWG 2.1:

Relativistic Geodesy: First Steps Towards a
New Geodetic Technique(joint with Commission 2, description see
Commission 2)
Chair: Jakob Flury (Germany)

JWG 3.2:

Constraining Vertical Land Motion of Tide
Gauges(joint with Commission 3, description see
Commission 3)
Chair: Alvaro Santamaría-Gómez (France)

Steering Committee
President Commission 1: Geoffrey Blewitt (USA)Vice President Comm. 1: Johannes Böhm (Austria)
Chair Sub-Comm. 1.1:
Urs Hugentobler (Germany)
Chair Sub-Comm. 1.2:
Xavier Collilieux (France)
Chair Sub-Comm. 1.3:
Carine Bruyninx (Belgium)
Chair Sub-Comm. 1.4:
Zinovy Malkin (Russia)
Representative of IERS: Detlef Angermann (Germany)
Representative of ILRS: Vincenza Luceri (Italy)
Representative of IVS: Guangli Wang (China)
Member-at-Large:
Gary Johnston (Australia)

Commission 1 – Reference Frames

989

Sub-Commissions

Working Groups of Sub-Commission 1.1

SC 1.1: Coordination of Space Techniques

WG 1.1.1: Co-Location using Clocks and New Sensors

Chair: Urs Hugentobler (Germany)

Chair: Ulrich Schreiber (Germany)

Terms of ReferenceTerms of Reference

Space techniques play a fundamental role for therealization and dissemination of highly accurate and longterm stable terrestrial and celestial reference frames as well
as for accurate monitoring of the Earth orientation
parameters linking the two fundamental frames. The
current space geodetic techniques contributing to ITRF and
ICRF, i.e., Very Long Baseline Interferometry (VLBI),
Satellite and Lunar Laser Ranging (SLR/LLR), Global
Navigation Satellite Systems (GNSS) and Doppler
Orbitography and Radiopositioning Integrated by Satellite(DORIS) have particular strengths and technique-specificweaknesses.
Strengths of the techniques are exploited by combining
them making use of fundamental sites co-locating morethan one technique. Sub-commission 1.1 focusses on thecoordination of research related to the geodetic spacetechniques with emphasis on co-location aspects at
fundamental geodetic observatories as well as on colocation targets in space, considering common parameterssuch as coordinates of stations and satellites, troposphereparameters, and clock parameters.

The establishment of accurate local ties of different space
geodetic techniques at fundamental geodetic observatories
poses a long-standing problem. While geometric ties canbe determined at sub-millimeter-level, the relation tophysical phase centers of the instruments and temporalstability of such offsets are usually known withsignificantly lower precision. Novel ways for intertechnique calibration at a geodetic site need to be
developed using existing and new sensors andtechnologies, such as highly accurate time and frequency
transfer, ultra-stable clocks, and co-location targets.
Complementary to such development the tying oftechniques shall be exploited to their limits at the analysis
level e.g. to using common clock and troposphereparameters.

Objectives
x Coordinate research on co-location using common
parameters in space;x Coordinate research on co-location using common
parameters at fundamental geodetic observatories;
x Explore the use of new techniques and technologies;x Interface with IERS WG on Site Survey and Colocation;
x Interface with the GGOS Committee on Performance
Simulations and Architectural Trade-Offs (PLATO);
x Interface with Joint WG on Tropospheric Ties.

Objectives
The main objective of the working group is theinvestigation of new methods and technologies to crosscalibrate space geodetic sensors at geodetic observatories
and to exploit common parameters at the analysis level.
The working group willx Investigate new technologies for inter-techniquecalibration of sensors at geodetic observatories;x Investigate the capabilities of accurate time andfrequency distribution between sensors at geodetic
observatories and between observatories;x Investigate the long-standing discrepancy in scale
coming from VLBI and SLR;
x Address the use of new sensors such as ring lasers,
quantum sensors, etc.;
x Further assess the contribution of estimation of common
parameters at analysis level to the stability and accuracyof geometric local ties and the consistency of combined
global reference frames.
To this purpose it closely interacts with the IERS WG
on Site Survey and Co-location and the Joint WG 1.1.6 on
Tropospheric Ties.

990

JWG 1.1.2: Performance Simulations andArchitectural Trade-Offs (PLATO)(joint with GGOS)
Chair: Daniela Thaller (Germany)
Vice-chair: Benjamin Männel (Germany)
Terms of Reference
The terrestrial reference frame (TRF) is the foundation forvirtually all space-based and ground-based Earthobservations. Positions of objects are determined within anunderlying TRF and the accuracy with which objects canbe positioned ultimately depends on the accuracy of thereference frame. The most accurate and stable global TRFs
currently available are the “International Terrestrial
Reference Frames (ITRFs)” produced under the auspicesof the “International Earth Rotation and Reference Systems
Service (IERS)” in cooperation with its technique-specificservices IDS, IGS, ILRS and IVS. In order to meet the
anticipated future needs of science and society, GGOS has
determined that by 2020 the accuracy and stability of the
ITRF needs to be better than 1mm and 0.1mm/y,
respectively. The current ITRF is at least an order ofmagnitude less accurate and stable than these goals.
The ITRF is currently determined and maintained by asubset of ground-based observations acquired by the spacegeodetic measurement techniques of VLBI, SLR, GNSS,
and DORIS. Further improvements of the ITRF arethought to be achieved by:x Developing next generation space-geodetic stations withimproved technology and system performance;x Improving the ground network configuration in view ofglobal coverage and co-locations;x Improving the number and accuracy of surveys between
co-located stations;x Deploying, improving and optimizing space-based colocations.
This joint working group aids these activities and helps toevaluate the impact on the accuracy and stability of future
ITRFs.
Objectives
Several aspects related to design of ground- and spacebased architectures and their impact on TRF accuracy andstability are investigated:x Study different ground station architectures and possible
evolutions (different techniques, mix of legacy and next
generation stations, co-located sites, data improvements/
degradations, etc.);x Develop optimal methods of deploying next generation
stations for TRF computation

Structures for the Period 2015-2019

x Study requirements on site ties and space ties, including
trade-offs between co-locating techniques on groundand/or in space;x Study different space-based architectures, including
laser ranging to GNSS or LEO satellites, VLBI
observations to GNSS satellites;
x Study new concepts for space-based architectures(including inter-satellite links, specially designed colocation satellites, VLBI transmitter on the moon, etc.);x Study evolution of space-based architectures (including
degradation of laser ranging targets, additional targets,new satellites / constellations, etc.);x Study trade-offs in space-geodetic data, e.g., between
number of stations vs. accuracy of observations, and colocating techniques at all sites vs. co-locating sometechniques at some sites, and number of co-locatedsatellites vs. amount of observations per space colocation.
These and other related aspects will be addressed by two
types of approaches:x Develop improved analysis methods using all existingdata and co-locations;x Carry out simulations for future improvements andoptimization of ground network, space segment andobservation scenario.

Commission 1 – Reference Frames

SC 1.2: Global Reference Frames
Chair: Xavier Collilieux (France)
Terms of Reference
Global reference frames are fundamental to study andlocate global phenomena or objects at the Earth's surface,in the ocean or in space, and to determine Earth's rotationin space. Sub-commission 1.2 focuses its activity on thedefinition and realization of the terrestrial reference system(TRS) and its link to world height system (WHS). It shallstudy fundamental questions but also more practicalaspects that could improve current terrestrial reference
frame (TRF) determinations.
More than 35 years of space geodetic observations are
now available. Thanks to this extraordinary datasets, nonstationary Earth surface displacements are now clearly
evidenced. The next generation of TRF should be able toexplicitly model them or should be constructed in such a
way that those displacements do not affect its accuracy.
Time series of frames have been suggested in the past as apotential solution but practical issues still need to be copedwith so that the implicit reference frame reach the required
accuracy. Multi-technique satellite that should tie all kindof space geodetic could potentially solve most of thesepractical issues. However, a set of accurate tie vectors that
relates position of various technique instruments at colocation sites will still be of outmost importance to validate
those new ties and monitor their variations along time.
Work on enhanced parametric modeling, coupled withenhanced forward displacement model is an alternative to
TRF time series. This approach is in agreement with pastmodeling of the International Terrestrial Reference Frame(ITRF) but still require progress in forward models(loading, seismic). In parallel of this work on the TRF
modeling, study of systematic errors in the coordinates
provided by various techniques is still mandatory to
improve the homogeneity and frame definition of the TRF
whatever the solution that will be adopted.
A step forward could be established by investigating
relativistic reference frames based on a network of clocks
in space linked with time transfer technologies. Suchrealized frame would be entirely decoupled from groundfixed stations and could be used to reference any point on
the Earth's surface. Difference of frequencies of clocks
would inform on Earth gravity potential differences, thistechnology being used in the end to determine a world
height system based on a network of ground clocks. In
such a framework, distinction between geometric andgravity based height system disappears.

991

While this ultimate goal still requires intensive researchworks, TRF and future WHS need to be studied in closer
partnership in order to locate reference benchmarks,
gravimeters or clocks in the TRF but also to provide
consistent coordinate and altitude time-variations.
The work of this sub-commission will be done inpartnership with the International Earth Rotation andReference Systems Service (IERS), IAG commission 2 andInter-Commission Committee on Theory (ICCT) as well as
IAG Global Geodetic Observing System (GGOS).
Cooperation with International Astronomical Union (IAU)
and International Organization for standardization (ISO)will be also continued.
Objectives
The main objectives of sub-commission 1.2 are thefollowing:x Standardization activities: ISO, United Nations
Committee of experts on Global Geospatial Information
Management (UN-GGIM) working group on global
geodetic reference frame (GGRF), IERS conventions;x Definition of the global terrestrial reference frame(origin, scale and orientation, time evolution, standards,
conventions, models);x Enhanced forward modeling of the Earth’s deformation;
x Modeling of the reference frame in general relativity;
x Linking global height system with the terrestrialreference frame;x Evaluation of systematic errors by focusing on errors at
co-location sites and offset detection methods;
x Methods to determine local tie vectors;
x Impact of multi-technique satellites (space ties).
Links to Services
Sub-Commission 1.2 will establish close links to therelevant services for reference frames, namely the IERS,
GGOS and IAG technique services: International GPS
Service (IGS), International Laser Ranging Service(ILRS), International VLBI Service for Geodesy andAstrometry (IVS), and International DORIS Service (IDS).

Structures for the Period 2015-2019

992

Working Groups of Sub-Commission 1.2

Objectives

WG 1.2.1: Offset Detection in Geodetic Coordinate
Time Series

x Encourage cooperation between different groups in thegeodetic community to contribute, investigate anddisseminate different offset detection methods;
x Identify and provide offset detection methods for theuse of the community, including code;x Provide a realistic benchmark dataset(s) on which to test
their efficacy (successor to the DOGEx);x Evaluate the validity of alternative velocity estimation
methods that may be less biased by undetected offsets
particularly in the context of a DOGEx follow on;
x Provide guidelines and advice on offset detection in
geodetic coordinate time series;x Foster and establish interactions with other areas ofscience for which offset detection is also an issue toidentify different approaches to the problem.

Chair: Simon Williams (UK)
Terms of Reference
The accuracy and validity of geodetic positioning timeseries are often degraded by the presence of step
discontinuities (offsets) that may either be known (e.g.
documented equipment changes or earthquakes) or
unknown, and with amplitudes that are, at best, known
imprecisely. Undetected offsets can have an adverse effecton estimated velocities. Accurate velocities are required
for many geophysical studies such as plate tectonics, intraplate deformations, global reference frames and regionaland global sea level. For example vertical land movements
at tide gauges need to be obtained with a precision andaccuracy of 0.1-0.2 mm/yr for sea level change studies. As
the length of time series continue to increase the number ofoffsets is likely also to increase and the cumulative effectof even the smallest of offsets can seriously alter our
velocity estimates. This, coupled with the huge growth in
the number of sites, particularly GNSS, necessitates theautomation of site velocity estimation and therefore offset
detection. Offset detection is an issue in many different
scientific studies, where it is often called data segmentationor homogenization, such as climate/meteorology,
economics, image processing and bio-statistics. However
what works in one discipline may not be suitable inanother. The aim of this working group is to encourage
cooperation between different groups in the geodetic
community to contribute, investigate and disseminate
different offset detection methods and provide a realistic
benchmark dataset(s) on which to test their efficacy.

Members
Simon Williams (UK), Chair
Machiel Bos (Portugal)
Norman Teferle (Luxembourg)
Matt King (Australia)
Xavier Collilieux (France)
Jarir Saleh (USA)Commission 1 – Reference Frames993

SC 1.3: Regional Reference Frames

Program of Activities

Chair: Carine Bruyninx (Belgium)x Organize inter-regional workshops addressing activities,
results and key issues of common interest to theregional Sub-commissions;x Develop analysis strategies and compare methods forthe implementation of the regional reference frames andtheir expression in the ITRF, in full interaction with the IGS;
x Consider developing tectonic deformation models thatwill enable transformation of locations within a definedreference frame between different epochs;
x At regional levels, contribute to the realization andimprovement of local surveys in the collocation sites,with full cooperation with the Sub-Commission 1.2
Global Reference Frames.

Terms of Reference
Sub-commission 1.3 deals with the definitions andrealizations of regional reference frames and theirconnection to the global International Terrestrial Reference
Frame (ITRF). It offers a home for service-like activities
addressing theoretical and technical key common issues ofinterest to regional organisations.
Objectives
In addition to the specific objectives of each regional Subcommission, the main objectives of SC 1.3 as a whole areto:x Coordinate the activities of the regional Subcommissions focusing on exchange of data, competences
and results;
x Promote operation of permanent GNSS stations, inconnection with IGS whenever appropriate, as the basis
for the long-term maintenance of regional reference
frames;x Promote open access to the GNSS data from permanent
GNSS stations used for the maintenance of regionalreference frames and scientific applications;x Develop specifications for the definition and realizationof regional reference frames, including the verticalcomponent with a special consideration of gravity andother data;x Encourage and stimulate the development of the
AFREF project in close cooperation with IGS and otherinterested organizations;x Encourage and assist countries, within each regional
Sub-commission, to re-define and modernize theirnational geodetic systems, compatible with the ITRF;
x Support the initiatives of the GGRF (Global Geodetic
Reference Frame) WG of the UN-GGIM (United
Nations Initiative on Global Geospatial Information
Management).

Structures for the Period 2015-2019994

SC 1.3a: Europe

Program of Activities

Chair: Markku Poutanen (Finland)
Secretary: Wolfgang Söhne (Germany)x Continue to develop the EPN in close cooperation
with IGS (International GNSS Service), for the
maintenance of the European Terrestrial Reference
Frame (ETRF), as a contribution to the ITRF and as an
infrastructure to support practical applications for
precise positioning and referencing geo-information;
x Extend the Unified European Levelling Network(UELN) and prepare it to be computed under ageokinematic approach using the European Combined
Geodetic Network (ECGN) for a long-term
maintenance of the European Vertical Reference Frame(EVRF);x Support new developments in reference frame
realization and application by introducing newtechnologies like real-time GNSS data transfer andproducts, as well as Galileo for precise positioning;x Realize a dense and homogeneous position and velocity
product for Europe;x Establish a dense velocity field model in Europe for the
long-term maintenance of the European reference
frame;x Cooperate with European political and scientificorganisations and projects, e.g. EuroGeographics,
EUMETNET, CEGRN (Central European GPS
Geodynamic Reference Network), EPOS (European
Plate Observing System), UN-GGIM: Europe, etc.
x Consider the contribution to the IAG Programme
GGOS (Global Geodetic Observing System) using the
installed infrastructures managed by the EUREF
members;x Promote the adoption of the reference systems definedby EUREF (ETRS89-European Terrestrial Reference
System 1989 and EVRS - European Vertical Reference
System) in the European countries and European-wide
initiatives related to geo-referencing activities like
INSPIRE;x Organize annual symposia addressing activities carriedout at national and Europe-wide levels related to theglobal work and objectives of EUREF.

Terms of Reference
EUREF, the Regional Reference Frame Sub-commission
for Europe, deals with the definition, realization andmaintenance of the European Reference Frames. EUREF is
focusing on both the spatial and the vertical components inclose cooperation with the pertinent IAG components(Services, Commissions, and Inter-commission projects)
and EuroGeographics, the consortium of the National
Mapping and Cadastral Agencies (NMCA) in Europe. For
more information, see www.euref.eu.
Objectives
EUREF’s objectives are
x The definition, realization and maintenance of theEuropean Geodetic Reference Systems;
x The promotion and assistance of the adoption and useof European Terrestrial Reference System (ETRS89)
and European Vertical Reference System (EVRS) in
our partner countries;
x The development and maintenance of the EUREF
GNSS Permanent Network (EPN) which is the groundbased GNSS infrastructure for scientific and practicalapplications in positioning and navigation (GGOS, IGS
Real-time Service);x The development of strategies and technologies for therealization of geodetic reference systems.
Structure
EUREF is composed of representatives from European
IAG member countries.
The TWG (Technical Working Group) is composed ofmembers elected by the plenary, members in charge of
special tasks and ex-officio members.

Commission 1 – Reference Frames

SC 1.3b: South and Central America
Chair: William Martinez (Colombia)
Vice-chair: Virginia Mackern (Argentina)
Terms of Reference
Sub-commission 1.3b (South and Central America)
encompasses the activities developed by the “Geocentric
Reference System for the Americas” (SIRGAS). As such,it is concerned with the definition, realization andmaintenance of a modern geodetic reference infrastructure
for South and Central America and the Caribbean. This
includes a geometric reference frame consistent with
ITRS/ITRF and a gravity field-related vertical reference
system, defined and realized globally.
Objectives
The main purposes of the Sub-commission 1.3b are:x To determine, maintain and make available a geocentricreference frame (a set of stations with high-precise geocentric positions and their variation with time, as aregional densification of the global ITRF);
x To support the SIRGAS countries in the establishment
and maintenance of national reference networks as local
densifications of SIRGAS in order to guarantee
accessibility to the ITRF at national and local levels;
x To establish a unified vertical reference system
supporting the determination and precise combination ofphysical and geometric heights as well as theirvariations with time;x To contribute to the GGOS program by developing andimplementing state-of-the-art products based on the
SIRGAS observational infrastructure;x To promote, support, and coordinate the efforts of theLatin American and Caribbean countries to achievethese objectives.
Structure
The structure of the Sub-commission 1.3b is based on thefunctioning bodies of SIRGAS. There are currently three
Working Groups:
x WG 1.3b.1: Reference System
Chair : Víctor José Cioce (Venezuela)
x WG 1.3b.2: SIRGAS at National Level
Chair: Roberto Pérez Rodino (Uruguay)x WG 1.3b.3: Vertical Datum
Chair : Silvio Rogério Correia de Freitas (Brazil)

995

The SIRGAS Executive Committee (as it is named in the
SIRGAS statutes) is composed of:x SC1.3b Chair : W. Martínez (Colombia)
x SC1.3b Vice-chair : Virginia Mackern (Argentina)
x SC1.3b WG1 Chair : Víctor José Cioce (Venezuela)
x SC1.3b WG2 Chair : Roberto Pérez Rodino (Uruguay)x SC1.3b WG3 Chair : Silvio Correia de Freitas (Brazil)
Program of Activities
Since the SIRGAS countries are improving their nationalreference frames by installing an increasing number ofcontinuously operating GNSS stations, it is necessary tooutline the best strategy for the appropriate integration of
those frames into the continental frame. This includes:
x Promotion of the IGS and IERS standards within the
SIRGAS countries to ensure the adequate installation,
maintenance, and analysis of continuously operating
GNSS stations;x Establishment of a SIRGAS National Processing Centre
in all the member countries;
x Refinement of the SIRGAS station hierarchy. At
present, two classes are considered: core anddensification stations (the establishment of othercategories is under consideration);x Promotion of the adequate usage of SIRGAS as areference frame by means of capacity building. This
comprises SIRGAS schools on reference frames, scientific processing of GNSS data, atmospheric analysis
based on the SIRGAS infrastructure, etc.;
x Promotion and implementation of real-time services
based on the SIRGAS infrastructure to make available
the reference frame to more users;
x The kinematics of the SIRGAS frame, up to now, havebeen represented by linear station movements (i.e.
constant velocities). This representation is not
sufficiently precise due to existing seasonal variations inthe station position time series and due to discontinuities
caused by the frequent occurrence of seismic events in
the SIRGAS region.
According to this, it is necessary:x To model non-linear station movements within thereference frame computation;
x To implement a methodology aiming at a precisetransformation between different epochs and, in general,
between pre-seismic and post-seismic reference frame
realizations in particular;
x To evaluate the feasibility of computing and using nearreal time reference frames instead of those based on
epoch station positions and constant velocities.

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The establishment of a unified vertical reference system
continues to be a big challenge of SIRGAS. The related
activities concentrate on:
x Continental adjustment of the national vertical networks
in terms of geo-potential numbers;
x Combined analysis of tide gauge registrations, GNSS
positioning and satellite altimetry observations to determine the dynamic ocean topography at the classicalvertical datums;x Determination of potential differences between thereference tide gauges and the global reference surface;x Stronger cooperation with the Sub-Commission 2.4b
(Gravity and Geoid in South and Central America GGSCA) to promote national initiatives regarding themodernization of the gravity reference networks and thecomputation of geoid models of high resolution.
Hourly SIRGAS ionospheric models (vTEC) based on
the GNSS SIRGAS stations have been generated since2006 on a regular basis. The SIRGAS ionospheric model isbeing upgraded to include a better distribution of theelectron density based on the assimilation of ground- andspace-based GNSS observations. In addition, SIRGAS isdeveloping a service for computing water vapour estimations.

SC 1.3c: North America
Chair: Michael Craymer (Canada)
Vice-chair: Dan Roman (USA)Terms of Reference
To provide international focus and cooperation for issues
involving the horizontal, vertical, and three-dimensional
geodetic control networks of North America, including
Central America, the Caribbean and Greenland (Denmark).
For more information, see www.naref.org.
Objectives
In collaboration with the IAG community, its service
organisations and the national geodetic organizations ofNorth America, the aims and objectives of this regional
Sub-commission are to provide international focus andcooperation for issues involving the horizontal, verticaland three dimensional geodetic control networks of North
America. Some of these issues include:x Densification of the ITRF reference frame in North
America and the promotion of its use;
x Maintenance and future evolution of plate-fixed
geometric reference frames for North America,
including the North American Datum of 1983 (NAD83)
and any possible successors.
x Maintenance and future evolution of vertical datums(ellipsoidal and orthometric), including the North
American Vertical Datum of 1988 (NAVD88) and theInternational Great Lakes Datum (IGLD);
x Effects of crustal motion, including post-glacial reboundand tectonic motions along, e.g., the western coast of
North America and in the Caribbean;x Standards for the accuracy of geodetic positions;x Outreach to the general public through focused
symposia, articles, workshops and lectures, andtechnology transfer to other groups.
Structure
Chair: Michael Craymer (Canada)
Vice-chair: Dan Roman (USA)
Organizing Committee:
Michael Craymer (Canada), Dan Roman (USA), Bo Finn
Madsen (Denmark), Guido Gonzalez (Mexico)

Commission 1 – Reference Frames

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Working Groups of Sub-Commission 1.3c

SC 1.3d: Africa

WG 1.3c.1: North American Reference Frame (NAREF)

Chair: Elifuraha Saria (Tanzania)

Chair: Michael Craymer (Canada)

Terms of Reference

Programme of Activities

Sub-commission 1.3d (Africa) is concerned with the definition and realization of a unified continental reference
frame (AFREF) for Africa, which will be consistent andhomogeneous with the global International Terrestrial
Reference Frame (ITRF).

To densify the ITRF reference frame in the North
American region by organizing the computation of weekly
coordinate solutions and associated accuracy information
for continuously operating GPS stations that are not part ofthe current IGS global network. A cumulative solution of
coordinate and velocities will also be determined on a
weekly basis. The working group will organize, collect,analyse and combine solutions from individual agencies,
and archive and disseminate the weekly and cumulative
solutions.

WG 1.3c.2: Plate-Fixed North American Reference Frame
Chair: TBD (USA)
Programme of Activities
To establish a high-accuracy, geocentric reference frame,
including velocity models, procedures and transformations,tied to the stable part of the North American tectonic plate
which would replace NAD83 and serve the broad scientificand geomatics communities by providing a consistent,
mm-accuracy, stable reference with which scientific andgeomatics results (e.g., positioning in tectonically active
areas) can be produced and compared.

WG 1.3c.3: Reference Frame Transformations
Chair: Michael Craymer (Canada)Todetermineconsistent
relationships
betweeninternational,
regional
andnationalreferenceframes/datums in North America, to maintain (update)these relationships as needed and to provide tools for
implementing these relationships.

Objectives
In collaboration with the IAG community and its services
organisations and the National and Regional Mapping
Organisations of Africa, the aims and objectives of Subcommission 1.3d (Africa) are:x To define the continental reference system of Africa.
The goal is to establish and maintain a unified geodetic
reference network as the fundamental basis for thenational 3-D reference networks fully consistent andhomogeneous with the global reference frame of the
ITRF;
x To realize a unified vertical datum and support efforts toestablish a precise African geoid, in concert with the
African Geoid project (Project 2.3 in Commission 2)
activities;
x To establish continuous, permanent GNSS stations suchthat each nation or each user has free access to, and is at
most 500km from, such stations;x To provide a sustainable development environment fortechnology transfer, so that these activities will enhance
the national networks, and numerous applications, withreadily available technology;
x To understand the necessary geodetic requirements ofparticipating national and international agencies and;x To assist in establishing in-country expertise for
implementation, operations, processing and analyses ofmodern geodetic techniques, primarily GNSS.

Structures for the Period 2015-2019

998

Program of Activities

SC 1.3e: Asia-Pacific

It is envisaged that the regionalization of AFREF will
follow an approach that consists of three major phases:
x The establishment of a framework of permanent orsemi-permanent GPS base stations throughout theregion that will become part of the worldwide IGS
stations network;x The densification of the network of permanent or semipermanent base stations, largely on a country-bycountry basis, to determine the relationship between thenational geodetic system and the ITRS, and to refine thetransformation parameters necessary to relate thenational systems to a common ITRF;
x The third and equally important phase of the project will
be to address the development of a more refined geoid
model for Africa and the definition of a common
vertical datum for the continent. This will be done incollaboration with the IAG Africa Geoid Project.

Chair: John Dawson (Australia)

It is further planned to hold workshops and seminars tostrengthen the science and knowledge of geodesy and
GNSS within Africa and their application to the development of reference frames.

Terms of Reference
To improve regional cooperation that supports therealization and densification of the International Terrestrial
Reference frame (ITRF). This activity will be carried out
in close collaboration with the Geodetic Reference
Framework for Sustainable Development Working Groupof the United Nations Global Geospatial Information
Management for Asia and the Pacific (UN-GGIM-AP).
Objectives
The objectives of the Sub-commission 1.3e are:x The densification of the ITRF and promotion of its use
in the Asia Pacific region;x To encourage the sharing of GNSS data from Continuously
Operating Reference Stations (CORS) in the region;x To develop a better understanding of crustal motion in
the region;x To promote the collocation of different measurement
techniques, such as GPS, VLBI, SLR, DORIS and tidegauges, and the maintenance of precise local geodetic
ties at these sites; andx To outreach to developing countries through symposia,
workshops, training courses, and technology transfer
activities.
Program of Activities
The activities of this Sub-commission will principally bethose of the Asia-Pacific Reference Frame (APREF), see
http://www.ga.gov.au/scientific-topics/positioningnavigation/geodesy/asia-pacific-reference-frame.

Commission 1 – Reference Frames999

SC 1.3f: Antarctica

Program of Activities

Chair: Martin Horwath (Germany)x Organization of GNSS campaigns in Antarctica;
x Extend activities for the operation of remote permanent
GNSS stations;x Maintenance of the data archive (SCAR GNSS database) to collect Antarctic GNSS data and provide themto the scientific community;
x Data analysis and determination of the Antarctic GNSS
network as a regional densification of ITRF;
x Provide homogeneous site velocities for e.g. glacialisostatic adjustment determination;
x Support airborne surveys and satellite missions with
precise terrestrial reference;x Collaborate
with
IAG
Sub-Commission
3.4(Cryospheric Deformation) and the SCAR Scientific
Research Programme Solid Earth Response andinfluence on Cryosphere Evolution (SERCE)x Organize special workshop(s) on the consistent analysis
of GNSS data and realization of ITRF
x Organize meetings/sessions at conferences like IAG,IUGG, SCAR Open Science Conference.

Terms of Reference
Sub-commission 1.3f (Antarctica) focuses on therealization and densification of a unified reference frame
for Antarctica, which will be consistent with the global
International Terrestrial Reference Frame (ITRF).
The Sub-commission shares objectives and activities of the
Scientific Committee on Antarctic Research (SCAR),
namely of the SCAR Expert Group Geodetic Infrastructure
for Antarctica (GIANT). The Sub-commission closely
links IAG and SCAR activities by embedding identicalactivities, with identical persons where indicated, into thetwo complementary organisational structures.
Objectives
x Maintenance and densification of the precise geodetic
reference network in Antarctica by permanent
observations and GNSS campaigns;
x Realization of a unified vertical datum including GNSS
ties of tide gauges;
x Providing unified reference for further GNSS
applications like airborne gravimetry, ground truthing
for satellite missions, geodynamics and glaciology;
x Develop technologies for remote geodetic observatories.
x Stimulate and coordinate international collaboration on
the above fields, under the unique political conditions of
Antarctic research given by the Antarctic Treaty, inorder to make optimum use of logistics andinfrastructure.

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1000

Working Groups of Sub-Commission 1.3

Members

WG 1.3.1: Time-Dependent Transformations Between
Reference FramesRichard Stanaway (Australia), Chair
Hasanuddin Abidin (Indonesia)
Sonia Alves (Brazil)
Graeme Blick (New Zealand)
Miltiadis Chatzinikos (Greece)
Chris Crook (New Zealand)Paul Denys (New Zealand)
Nic Donnelly (New Zealand)
Rui Fernandes (Portugal)
Yasushi Harada (Japan)
Kevin Kelly (USA)Juliette Legrand (Belgium)
Daphné Lercier (France)
Martin Lidberg (Sweden)
Rob McCaffrey (USA)
Christopher Pearson (New Zealand)
Craig Roberts (Australia)
Laura Sánchez( Germany)
Yoshiyuki (Japan)
Norman Teferle (Luxembourg)

Chair: Richard Stanaway (Australia)
Terms of Reference
The main aim of the WG is to focus research indeformation modelling into the rapidly emerging field ofregional reference frames used in applied geodesy,particularly positioning and GIS. Deformation models andother time-dependent transformation models provide
linkages between global reference frames such as ITRF,
regional reference frames and local reference framescommonly used for land surveying and mapping.
The WG will integrate the findings of IAG WG 1.3.1“Integration of dense velocity fields in the ITRF” (20112015), the EUREF WG on Deformation Models and othercurrent research into developing a global deformation andtransformation model schema that can be used to support
realisation of regional and local reference frames fromITRF to support GIS and positioning technologies such as
Network RTK (NRTK). This will require development of astandardised deformation model format that can beaccessed from international registries of geodetic
parameters such as those hosted by ISO/TC 211 and EPSG
(European Petroleum Survey Group).
WG 1.3.1 will work closely with FIG Commission 5(Positioning and Measurement), specifically FIG Working
Group 5.2 (Reference Frames). WG members comprise ofa wide spectrum of researchers from different fields ofgeophysics, geodesy, land surveying and GIS.

Commission 1 – Reference Frames

SC 1.4: Interaction of Celestial andTerrestrial Reference Frames

1001

Working Groups of Sub-Commission 1.4

Chair: Zinovy Malkin (Russia)

WG 1.4.1: Consistent Realization of ITRF, ICRF, andEOP

Terms of Reference

Chair: Manuela Seitz (Germany)International terrestrial and celestial reference frames,
ITRF and ICRF, respectively, as well as the tie between
them expressed by the Earth Orientation parameters (EOP)
are key products of geodesy and astrometry. The
requirements to all the components of this triad growsteadily and the mm/μas level of accuracy is the current
goal of the astronomic and geodetic community.
The current computation procedures for ITRF and ICRF arebased on multi-stage processing of observations made withseveral space geodetic techniques: VLBI, SLR, GNSS, and
DORIS. Not all of them provide equal contributions to the final
products. The latest ITRF realizations have been derived fromcombination of normal equations obtained from all four
techniques, whereas the ICRF is a result of a single global
VLBI solution. The latter is tied to the ITRF using an arbitrary
set of reference stations. But VLBI relies on the ITRF origin
provided by satellite techniques and shares responsibility with
SLR for the ITRF scale. And all the techniques contribute topositions and velocities of ITRF stations.
This situation causes complicated mutual impact of ITRF
and ICRF, which should be carefully investigated in order toimprove the accuracy of both reference systems and theconsistency between each other and EOP. The subject becomes
more and more complicated when moving to millimeter
accuracy in all components of this fundamental triad. As aconsequence, we face systematic errors involving theconnection between the ICRF and ITRF realizations, whichcannot be fixed by datum correction during the current solution.

Objectives

Objectives
There are several issues currently preventing therealization of the terrestrial and celestial reference systems(TRF and CRF, respectively) at the mm/μas level of accuracy:
x Insufficient number and non-optimal distribution ofactive and stable (systematically and physically) stations(VLBI and SLR in the first place) and radio sources;
x Technological (precision) limitations of existing techniques;x Incompleteness of the theory and models;x Not fully understood and agreed-upon details of theprocessing strategy.
These issues are the subject of research of the IAG SubCommission 1.4. The SC 1.4 is organized in three Working
Groups in close cooperation.

x Investigation of the impact of different analysis options
and combination strategies on the consistency between
TRF, CRF, and EOP derived from joint analysis of thespace geodesy observations.
x Investigation of the consistency between the current
ICRF and ITRF versions and IERS EOP C04 series.
x Investigation of the consistency between VLBI-only(IVS) CRF, TRF, and EOP series with the ITRF, ICRF,
and C04 EOP series.
x Study of effects of geodetic datum realization on VLBIderived CRF.
x Study of optimal use of the space-collocated techniques
in improvement of the consistency between TRF, CRF,
and EOP.
Members
Manuela Seitz (Germany), Chair
Susanne Glaser (Germany)
Richard Gross(USA)Robert Heinkelmann (Germany)
Chris Jacobs (USA)Sebastien Lambert (France)
Karine Le Bail (USA)Zinovy Malkin (Russia)
David Mayer (Austria)
Dan MacMillan (USA)
Hana Krasna (Austria)

Structures for the Period 2015-2019

1002

WG 1.4.2: Impact of Geophysical and Astronomical
Modeling on Reference Frames and their
Consistency

WG 1.4.3: Improving VLBI-based CRF for Geodesy

Chair: Dan MacMillan (USA)Objectives

Objectives

The WG will address the way of improving the VLBI CRF
and how these improvements can impact other geodetic
products. The following items will be looked into:x Analysis and Solution Parameterization– More advanced gradient parameterization– Estimation of systematic temporal variation of source
positions– Galactic aberration modelx External Models (Comparisons of models and effect onreference frames)– Loading models– Troposphere delay models (mapping functions or
raytraced delays) based on numerical weather models– Effects arising from shifting from ITRF2008 to
ITRF2014
x Internal Inconsistency– Declination zonal systematic CRF difference
between 2009 and current solutions– Addition of Australian network data?
– Troposphere estimation effect?
– Other VLBI network dependent effects?
Members
Dan MacMillan (USA), Chair
Robert Heinkelmann (Germany)
Tobias Nilsson (Germany)
Hana Krásná (Austria)
David Mayer (Austria)
Sebastien Lambert (France)
Manuela Seitz (Germany)
Zinovy Malkin (Russia)

Chair: Sébastien Lambert (France)x ICRS/ICRF definition in view of the latest
developments in astrometry and space geodesy,x Systematic errors in the current individual CRF
realizations,x Effects of changing the wavelengths due to, e.g., coreshift,x Modeling and analysis options
x Interaction with futures Gaia-like CRF
Members
Sébasitien Lambert (France), Chair
François Mignard (France)
Maria Karbon (Germany)
Dan MacMillan (USA)Zinovy Malkin (Russia)
Jacques Roland (France)
Manuela Seitz (Germany)
Stas Shabala (Australia)

Commission 1 – Reference Frames

1003

Joint Working Groups of Commission 1

Members

JWG 1.1: Site Survey and Co-Location(joint with the IERS)

Sten Bergstrand (Sweden), ChairJohn Dawson (Australia), Vice-chair
Rüdiger Haas (Sweden)
Jim Long (USA)
Erricos Pavlis (USA)
Jerome Saunier (France)
Ralf Schmid, (Germany)

Chair: Sten Bergstrand (Sweden)
Vice-chair: John Dawson (Australia)
Terms of reference
The combination of space geodetic solutions is criticallyreliant on the availability of local tie vectors, which are therelative positions of the reference points of co-locatedspace geodetic instruments determined by some survey
technique. Tie vectors enter the combination of space
geodetic solutions effectively as a fifth technique and are
not only necessary for rigorous terrestrial reference frame
realization but also serve to highlight the presence oftechnique- and/or site-specific biases.
With the ultimate objective of improving the accuracyof tie vectors as well as the consistency of space geodetic
solutions, the Working Group (WG) will provide anauthoritative source of surveying methodology advice,promote technical discussion, provide a forum for theevaluation of existing and new procedures and analysis
strategies, and support the exchange of relevant
information across GGOS and between the IAG techniqueservices. Currently, dedicated points of contact (POC) havebeen established with IDS, IGS, ILRS and IVS. The WG
will also support new survey activities with advice andadvocate for re-survey where necessary.
Goals and objectives
Research:x Revise existing local tie proceduresx Revise existing tie vector estimation processes
x Develop and define new methods
Coordination:
x Liaise with IERS combination centres
x Liaise with IAG technique services
x Direct research towards the investigation of techniquespecific systematic effects
Outreach:x Remotely support local tie operations and tie vector
estimationx Spread the know-how
x Set guidelines

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1004

JWG 1.2: Modelling environmental loading effects for
Reference Frame realizations(joint with the IERS)
Chair: Tonie van Dam (Luxembourg)
Vice-chair: Anthony Mémin (France)
Terms of reference
The accuracy and precision of current space geodetic
techniques are such that displacements due to non-tidal
surface mass loading are measurable. Many scientificstudies have already considered atmospheric loading
corrections at the observation level. The modeling of other
non-tidal loading effects has been also investigated byvarious authors. In parallel, a posteriori corrections havebeen shown to slightly decrease the variance factor of a
Terrestrial Reference Frame (TRF) multi-technique
combination but the improvement at some sites was alsocounterbalanced by degradation at others.
There still exist open questions regarding theapplication of loading corrections for the generation ofoperational geodetic products, either a priori or aposteriori: accuracy of the models in all frequency bands sub-daily band is the most important for a priori
corrections -, too few studies regarding available loading
model agreement have been carried out, proper massconservation of all contributions and degree 0 of eachcontribution, methods that should be use for interpolating
the loading displacements, required model resolution,reference loads that are or should be used for geodetic
products, contribution of ice melting at high latitude which
is not modeled in current continental water loading models.
The optimal usage of loading models is still to be definedin all possible applications.
The goal of this working group is to study the optimal
usage of load models for TRF utilization.
Objectives
The principal objectives of the scientific work are toinvestigate optimal methods for applying load corrections
for TRF development and usage, and to assemble specificrecommendations for users.

Specific program activities
x Compare and assess differences between existing load
models for a given effect.
x develop forward model of ice loading at high latitudes
x monitor geocenter motion variations to identify possible
accelerations
x Maintain a bibliography on the available models andtheir evaluation.
x Assessment of the propagation of loading model errors
into the site coordinates and the ITRF.
x Define whether models should be applied at theobservation level or in the post-processing. In this case,define the best method (if any) to handle loading effects
at the observation level (filtering, interpolation etc…).
x Tie results/findings to IERS conventions.
x Collect user opinions about what signals they need instation position time series (loading corrected or not).
Members
Tonie van Dam (Luxembourg), Chair
Anthony Mémin (France), Vice-chair
Zuheir Altamimi (France)
Johannes Böhm (Austria)
Jean-Paul Boy (France)
Xavier Collilieux (France)
Robert Dill (Germany)
Pascal Gegout (France)
Matt King (Australia)
Anthony Mémin (France)
Laurent Métivier (France)
Gerard Petit (France)
Jim Ray (USA)
Leonid Vitushkin (Russia)
Xiaoping Wu (China)

Commission 1 – Reference Frames

JWG 1.3: Troposphere Ties
Chair: Robert Heinkelmann (Germany)
Vice-chair: Jan Douša (Czech Republic)
Terms of Reference
Since many years, tropospheric parameters have been
determined by space geodetic techniques, by othermeasurement techniques, such as water vapor radiometers,
and, more recently, from model data, e.g. from numerical
weather models. As tropospheric parameters we designate
the hydrostatic and wet or total zenith delays and thehorizontal gradients. Many comparative studies haverevealed that besides statistical deviations the troposphericparameters partly exhibit systematic differences. Suchsystematic differences might be caused by
x General differences, e.g. the different locations of thesensors, the different epochs of the observations andother e.g. meteorological ambient conditions;x Effects due to hardware and hardware changes, e.g.
change of the type of the GNSS antenna or effect of aradome at a station;
x The inter-technique systematics, for example due todifferent correlations among groups of parameters and /or due to the different sampling and geometry ofobservations;x The application of different analysis models, such as the
mapping functions, the different parameterizations used
to represent the troposphere and the application of
constraints during the adjustment, and, in addition;
x The post-processing methods of data handling for thecomparison, e.g. the application of synchronization
methods, such as interpolation, filtering, smoothing.
The terrestrial reference frame (TRF) is commonly
realized by a combination of space geodetic techniques.
For the combination of the techniques ‘global ties’, i.e.
common global parameters, like the Earth Orientation
Parameters (EOP), can be directly used, while ‘local ties’,
i.e. common coordinates at co-location sites, have toconsider the distances between the reference points of thevarious devices. The distances between the reference
points are usually surveyed at site, but can also be
indirectly assessed through the comparison of the positions
determined by the various space geodetic techniques. The
ground-based space geodetic techniques all observe targets
in or above the atmosphere and consequently common
atmospheric parameters might be used to link thetechniques as well. The systematics between troposphericparameters obtained by different sensors have to beconsidered to reasonably perform this combination

1005

approach. With ‘tropospheric ties’ we designate thesystematics that enable a combination of troposphericparameters if they are appropriately considered.
Objectives
The main objective of the working group is (i) to assess thesystematics between tropospheric parameters obtained at
different locations, times, and by different measurement
techniques: tropospheric ties. The other focus is (ii) to test
the application of tropospheric ties for the combination of
the space geodetic techniques. Accordingly, the group will
work onx Extensive comparisons of tropospheric parameters;
x Theoretical modeling based on hydrostatic equilibrium
and comparable assumptions;x Numerical modelling involving numerical weathermodels; andx Testing the combination with the application of thetropospheric ties.
Members
Robert Heinkelmann (Germany), Chair
Jan Douša (Czech Republic), Vice-chair
Thomas Artz (Germany)
Kyriakos Balidakis (Germany)
Elmar Brockmann (Switzerland)
Gregor Möller (Austria)
Angelyn W. Moore (USA)Tobias Nilsson (Germany)
Rosa Pacione (Italy)
Tzvetan Simeonov (Bulgaria)
Peter Steigenberger (Germany)
Kamil Teke (Turkey)
Daniela Thaller (Germany)
Xiaoya Wang (China)
Pascal Willis (France)
Florian Zus (Germany)

Commission 2 – Gravity Field

1007

Commission 2 – Gravity Field
President: Roland Pail (Germany)
Vice President: Shuanggen Jin (China)
http://alpha.fesg.tu-muenchen.de/IAG-C2/

Terms of Reference
The accurate determination of the gravity field and its
temporal variations is one of the three fundamental pillars
of modern geodesy (besides of geometry/kinematics andEarth rotation). This is essential for applications inpositioning and navigation, civil engineering, metrology,
geophysics, geodynamics, oceanography, hydrology,
cryospheric sciences and other disciplines related to the
Earth’s climate and environment. IAG Commission 2 wasestablished at the IUGG in Sapporo in summer 2003 forpromoting, supporting, and stimulating the advancement ofknowledge, technology, and international cooperation in
the geodetic domain associated with Earth’s gravity field.
Since most of the scientific themes are of long-term
interest, large parts of the structure of Commission 2 arecontinued on the same basis as in the previous period
2011-15. Main focus points for the present period 2015-19
are related to the IUGG and IAG resolutions adopted at the
XXVI IUGG General Assembly 2015 in Prague,
addressing the topics global geodetic reference frames,
future satellite gravity mission constellations, and the roleof oceans in the climate system (IUGG), as well as
definition and realization of an International Height
Reference System (IHRS) and the establishment of an
absolute gravity reference system (IAG). The structure ofCommission 2 has been adopted to address theseobjectives and tasks, and joint working and study groups
have been implemented accordingly.
Commission 2, at the start of the new period, consists ofsix sub-commissions (SCs), plus several Joint Study
Groups (JSG) and Joint Working Groups (JWG), all ofthem jointly with other Commissions and/or services. The
sub-commissions cover the following scientific topics:x Terrestrial (land, marine, airborne) gravimetry andrelative/absolute gravity networks;
x Methodology for geoid and physical height systems;
x Satellite gravity missions;x Regional geoid determination;x Satellite altimetry;x Gravity and mass transport in Earth system.
Commission 2 has strong links to other commissions,
GGOS, IGFS, ICCT and other components of IAG.
Connections to these components are created through joint
working groups (JWGs) and joint study groups (JSGs) thatprovide a cross-disciplinary stimulus for work in several
topics of interest to the commission, and the joint
organization of meetings.
The main tasks of Commission 2 in the period 2015-19
are among others:
x Establishment of a global absolute gravity reference system(GAGRS) to replace the International Gravity Standardization
Net 1971 (IGSN71), which no longer fulfills therequirements and accuracy of a modern gravity reference;
especially to include time-dependent gravity variations;x Supporting the realization of an International Height
Reference System (IHRS);
x Supporting the realization of an Global Geodetic
Reference System (GGRS);x Analysis of current and future satellite data (CHAMP,GRACE, GOCE, GRACE-FO) and the release of
improved global Gravity field models (satellite only
models and in combination with terrestrial data andsatellite altimetry);x Promoting future gravity mission constellations forassuring the continued monitoring of global gravity andmass transport processes in the Earth system;x Assuring the future of the comparison campaigns ofabsolute gravimeters;

Structures for the Period 2015-2019

1008

x Investigating modern relativistic methods and geodetic
metrology with special focus on gravity field and height
determination;
x Fostering regional gravity and geoid determination andintegration of regional models into a global referencex Assisting the regional sub-commissions in establishingcontacts and in acquiring data;x Understanding of physics and dynamics of the Earthsub-systems and mass transport processes in the Earthsystem;x Providing contributions to operationalization of masstransport modelling and stimulation of new applications
x Fostering communication with user communities;
x Assisting the IGFS and its components in improving
their visibility and their services;
The necessary WGs and SGs can be established at any
time and they can be dissolved when they reached theirgoals or if they are not active.

Objectives
The main objectives of Commission 2 are as listed in the
IAG by-laws:x Terrestrial, marine and airborne gravimetryx Satellite gravity field observations
x Gravity field modelingx Time-variable gravity fieldx Geoid and height determinationx Satellite orbit modeling and determinationx Satellite altimetry for gravity field modeling

Structure
Sub-Commissions
SC 2.1: Gravimetry and Gravity networks
Chair: Leonid F. Vitushkin (Russia)
SC 2.2: Methodology for Geoid and Physical Height Systems
Chair: Jonas Ågren (Sweden)
SC 2.3: Satellite Gravity Missions
Chair: Adrian Jäggi (Switzerland)
SC 2.4: Regional Geoid Determination
Chair: Maria Cristina Pacino (Argentina)
SC 2.4a: Gravity and Geoid in Europe
Chair: Heiner Denker (Germany)
SC 2.4b: Gravity and Geoid in South America
Chair: Maria Cristina Pacino (Argentina)

SC 2.4c: Gravity and Geoid in North and Central America
Chair: Marc Véronneau (Canada)
SC 2.4d: Gravity and Geoid in Africa
Chair: Hussein Abd-Elmotaal (Egypt)
SC 2.4e: Gravity and Geoid in Asia-Pacific
Chair: Jay Hyoun Kwon (Korea)
SC 2.4f: Gravity and Geoid in Antarctica
Chair: Mirko Scheinert (Germany)
SC 2.5: Satellite Altimetry
Chair: Xiaoli Deng (Australia)
SC 2.6: Gravity and Mass Transport in the Earth System
Chair: Jürgen Kusche (Germany)
Joint Study Groups
JSG 0.11: Multiresolution aspects of potential field theory(joint with ICCT, Commission 3, see ICCT)
Chair: Dimitrios Tsoulis (Greece)
JSG 0.12: Advanced computational methods for recoveryof high-resolution gravity field models(joint with ICCT, GGOS, see ICCT)
Chair: Robert Čunderlík (Slovak Republic)
JSG 0.13: Integral equations of potential theory forcontinuation and transformation of classical andnew gravitational observables(joint with ICCT, GGOS, see ICCT)
Chair: Michal Šprlák (Czech Republic)
JSG 0.15: Regional geoid/quasi-geoid modelling –Theoretical framework for the sub-centimeter
accuracy(joint with ICCT, GGOS, see ICCT)
Chair: Jianliang Huang (Canada)
JSG 0.16: Earth’s inner structure from combined geodetic
and geophysical sources(joint with ICCT, Commission 3, see ICCT)
Chair: Robert Tenzer (China)
JSG 0.18: High resolution harmonic analysis and synthesisof potential fields(joint with ICCT, GGOS, see ICCT)
Chair: Sten Claessens (Australia)
JSG 0.21: Geophysical modelling of time variations indeformation and gravity(joint with ICCT, Commission 3, see ICCT)
Chair: Yoshiyuki Tanaka (Japan)

Commission 2 – Gravity Field

JSG 3.1: Intercomparison of Gravity and Height Changes(joint with IGFS, Commissions 1 and 3,
description see Commission 3)
Joint Working Groups
JWG 0.1.2: Strategy for the Realization of the International
Height Reference System (IHRS)(joint with GGOS, Commission 1, ICCT, IGFS,
description see GGOS)
Chair: Laura Sánchez (Germany)JWG 2.1: Relativistic Geodesy: First steps towards a newgeodetic technique(joint with Commission 1)
Chair: Jakob Flury (Germany)

Program of Activities
The Gravity Field Commission fosters and encourages
research in the areas of its sub-entities by facilitating theexchange of information and organizing Symposia, either
independently or at major conferences in geodesy. The
activities of its sub-entities, as described below, constitutethe activities of the Commission, which will becoordinated by the Commission and summarized in annual
reports to the IAG Bureau.
The principal symposia that will be organized jointly by
Commission 2 and the IGFS in the next period will be heldin Thessaloniki in September 2016 and in 2018 (location
TBD). The other two symposia where a Commission 2
meeting will be held are the IAG Scientific Assembly 2017
in Kobe, Japan, and the IUGG General Assembly 2019 inMontréal.
The status of Commission 2, including its structure andmembership, as well as links to the internet sites of its subentities and parent and sister organizations and services,
will be updated regularly and can be viewed on the website: http://alpha.fesg.tu-muenchen.de/IAG-C2.

1009

Steering Committee
President Commission 2: Roland Pail (Germany)
Vice President Comm. 2: Shuanggen Jin (China)
Chair Sub-Comm. 2.1:
Leonid F. Vitushkin (Russia)
Chair Sub-Comm. 2.2:
Jonas Ågren (Sweden)
Chair Sub-Comm. 2.3:
Adrian Jäggi (Switzerland)
Chair Sub-Comm. 2.4:
Maria C. Pacino (Argentina)
Chair Sub-Comm. 2.5:
Xiaoli Deng (Australia)
Chair Sub-Comm. 2.6:
Jürgen Kusche (Germany)
Representative of IGFS: Riccardo Barzaghi (Italy)
Representative of ICCT: Pavel Novák (Czech Republic)
Member-at-Large:
Laura Sanchez (Germany)
Member-at-Large:
Urs Marti (Switzerland)
The steering committee will meet at least once per year.
These meetings are open for all interested IAG members.

Structures for the Period 2015-2019

1010

Sub-Commissions
SC 2.1: Gravimetry and Gravity Network
Chair: Leonid F. Vitushkin (Russia)
Vice-chair: Akito Araya (Japan)
Terms of Reference
IAG Sub-commission 2.1 "Gravimetry and gravity
networks" promotes scientific studies of the methods andinstruments for terrestrial (on the land, airborne, shipboard)gravity measurements, establishment of gravity networks
and improvement of strategy in the measurement of gravity
networks provided by growing number of absolute gravity
determinations and the sites for such determinations. The
Sub-commission provides the geodesy-geophysics
community with the means to access the confidence ingravity measurements at the well-defined level of accuracy
through organizing, in cooperation with metrology
community, Consultative Committee on Mass and Related
Quantities and its Working Group on Gravimetry (CCM
WGG), Regional Metrology Organizations (RMO) theinternational comparisons of absolute gravimeters on
continental scale. The Sub-commission proceeds from such
point-wise gravimetry to precise gravimetry/gradiometry
which should cover, in particular, the land-sea border areas
to resolve still existing problem of significant biases anderrors in determination.
Objectives
The Sub-commission promotes such research anddevelopment by stimulating airborne and shipboard
gravimetry and gradiometry. It encourages and promotes
special absolute/relative gravity campaigns, techniques andprocedures for the adjustment of the results of gravity
surveys on a regional scale. It promotes the research in thelinking of satellite and terrestrial gravity measurements.
In the frame of realization of the “CCM-IAG Strategy
for Metrology in Absolute Gravimetry” the Subcommission in collaboration with metrology community
promotes the implementation of the system of metrologicalsupport (calibration, verification, comparisons) of absolutegravimeters belonging to geodesy-geophysics community.
For the realization of these goals, the SC 2.1 sets up the
Study Group SG 2.1.1 on techniques and metrology interrestrial (land, marine, airborne) gravity measurements
and the joint with IGFS and IGETS Working Group
JWG2.1.1. SC2.1 appoints the Steering Committee consisted ofthe members experienced in the fields of gravimetry
related to the activities of SC2.1 and the contact persons

for European, East Asia and Western Pacific, SouthAmerica and North America Gravity Networks.
According to the Resolution 2 of IAG adopted at the
IUGG General Assembly in Prague in 2015 the Subcommission supports through its JWG2.1.1 in collaboration
with IGFS and IGETS the development of the Global
Absolute Gravity Reference System (GAGRS) for GGOS
technically and works on the standardization of absolutegravity data, software for absolute gravity measurement
and appropriate information. The Sub-commission willencourage regional meetings or workshops dedicated to
specific problems, where appropriate.
Program of Activities
x Selection (JWG 2.1.1) in collaboration with CCM WGG
of the sites for regional comparisons of absolutegravimeters, as the basis for GAGRS,
x providing the results of comparisons of absolutegravimeters to data base AGrav at BKG-BGI,x supporting the scientific investigations of absolute andrelative (including the superconducting) gravity
measurements on static and moving platforms,
x organizing the IAG Commission 2 Symposiums"Terrestrial
Gravimetry.
Staticandmobilemeasurements – TGSMM-2016 and TGSMM-2019".

Commission 2 – Gravity Field

1011

Study Groups of Sub-Commission 2.1

Members

SG 2.1.1: Techniques and metrology in terrestrial(land, marine, airborne) gravimetry

Derek van Westrum (USA), Chair
Christoph Förste (Germany), Vice-chair
Matthias Becker (Germany)
Mirjam Bilker (Finland)
Nicholas Dando (Australia)
Andreas Engfeld (Sweden)
Reinhard Falk (Germany)
Olivier Francis (Luxemburg)
Alessandro Germak (Italy)
Filippo Greco (Italy)
Joe Henton (Canada)
Jeff Kennedy (USA)Anton Krasnov (Russian Federation)
Nicolas LeMoigne (France)
Sebastien Merlet (France)
Oleg Orlov (Russian Federation)
Vojtech Palinkas (Czech Republic)
Vladimir Schkolnik (Germany)
Sergiy Svitlov (Ukraine)
Ludger Timmen (Germany)
Michel Van Camp (Belgium)

Chair: Derek van Westrum (USA)Vice-chair: Christoph Förste (Germany)
Terms of Reference
The SG 2.1.1 is concentrated on the scientific studies of
the techniques and methods of the measurements ofterrestrial gravity field on static and moving platforms (onthe land, shipboard and airborne gravimetry and gravity
gradiometry). It encourages and coordinates special
absolute and relative gravity campaigns, development of
the techniques, gravimetry sites and networks for themonitoring of temporal variations of gravity field using inparticular the superconducting gravimetry. It promotes the
improvements of the strategy in the measurement ofgravity for such applications as hydrogeology, studies of
volcanoes, technical geology, etc.
The SG2.1.1 promotes the studies of the techniques andprocedures for the adjustment of the results of gravity
surveys on a regional scale. It promotes the research in thelinking of satellite and terrestrial gravity measurements andthe studies of the use of terrestrial gravity data for thecalibration of the satellite gravity measurements.
The SG2.1.1 aims to deal with the technical andmetrological aspects in terrestrial absolute and relative
gravity measurements in collaboration with metrology
community.
Objectives
x Promotion and coordination of scientific studies of thetechniques and methods of absolute and relative
terrestrial gravity measurements on static and moving
platforms.
x Promotion and coordination in the establishment andmeasurements of regional gravity networks.
x The collaboration with metrology community for the
implementation of the system of calibration andverification of absolute gravimeters.
x Organization of scientific workshops and meetings forthe discussion of actual subjects in techniques andmethods of terrestrial gravity measurements.

Corresponding Members
Martin Amalvict (France)
Jan Krynski (Poland)
Chiungwu Lee (China-Taipei)
Shigeki Mizushima (Japan)
Jan Mrlina (Czech Republic)
Andrzej Pachuta (Poland)
Alfredo Esparza Ramires (Mexico)René Reudink (The Netherlands)
José Manuel Serna Puente (Spain)
Yury Stus (Russian Federation)
Simon Williams (UK)Structures for the Period 2015-2019

1012

Joint Working Groups of Sub-Commission 2.1
JWG 2.1.1: Establishment of a global absolute gravity
reference system(joint with IGFS, IGETS)
Chair: Hartmut Wziontek (Germany)
Vice-chair: Sylvain Bonvalot (France)
Terms of Reference
One task of IAG's Commission 2 “Gravity Field” is theestablishment of an absolute gravity reference system toreplace the International Gravity Standardization Net 1971
(IGSN71). At the IUGG General Assembly in Prague
2015, Resolution No. 2 for the establishment of a global
absolute gravity reference system was adopted by the IAG.
IAG Sub-Commission 2.1 “Gravimetry and Gravity
Networks” promotes scientific investigations of gravimetry
and gravity networks and terrestrial (on the land, airborne,
marine) and planetary gravity measurements. One of theoutputs of the SC 2.1 activities is the result of gravity
measurements, i.e. the gravity data. The International
Gravity Field Service IGFS coordinates the servicing of
the geodetic and geophysical community with gravity field
related data, software and information. A modern andprecise absolute gravity reference system will not only
contribute to the establishment of the Global Geodetic
Reference Frame (GGRF) of UN but will serve as a longterm and precise gravity reference for GGOS, the IAG
Global Geodetic Observing System.
Objectives
In the frame of IAG Sub-Commission 2.1 “Gravimetry andGravity Networks” the necessary steps to realize this newreference system will now be prepared by the JWG 2.1.1.
It will focus on the preparation of a roadmap forestablishment of the GAGRS taking into account:x Repeated international comparisons of absolutegravimeters under guidance of the International
Committee for Weights and Measures (CIPM) andRegional Metrology organizations which define bothmeasurement standards in gravimetry (absolutegravimeters) and absolute gravity standards for
metrology and geodesy;x A set of distributed gravity reference stations where therepeated absolute gravity measurements and themonitoring of temporal gravity changes withsuperconducting gravimeters for the realization of an
absolute gravity reference function;

x The transfer of international comparison results to otherabsolute gravimeters and reference stations, as outlinedin the document “CIPM – IAG Strategy for Metrology
in Absolute Gravimetry”;
x The definition of standard models for the correction ofabsolute gravity data in cooperation with the GGOS
Bureau of Standards and Conventions.
The absolute gravity database “AGrav”, which alreadybecame a fixed part of the BGI (International GravimetricBureau) services, will be used as a registry for the global
absolute gravity reference system. The extension forstorage and distribution of comparison results will be an
essential task.
Cooperation with the new International Geodynamics
and Earth Tide Service (IGETS) of IAG (former Global
Geodynamics Project, GGP) should be established torealize the continuous monitoring at the gravity reference
stations.
Members
Hartmut Wziontek, Chair (Germany),
Sylvain Bonvalot, Vice-chair (France),
Jonas Ågren (Sweden), Henri Baumann (Switzerland),Mirjam Bilker Koivula (Finland), Jean-Paul Boy (France),
Nicholas Dando (Australia), Reinhard Falk (Germany),
Olivier Francis (Luxembourg), Domenico Iacovone (Italy),
Jan Krynski (Poland), Jacques Liard (Canada),
Urs Marti (Switzerland), Vojtech Palinkas (Czech Republic),
Diethard Ruess (Austria), Victoria Smith (UK),
Ludger Timmen (Germany), Michel van Camp (Belgium),Derek van Westrum (USA), Leonid Vitushkin (Russia),
Shuqing Wu (China).
Corresponding Members
Mauro Andrade de Sousa (Brazil), In-Mook Choi (Korea),Andreas Engfeldt (Sweden), Yoichi Fukuda (Japan),
Alessandro Germak (Italy), Joe Henton (Canada),
Jacques Hinderer (France), Juraj Janak (Slovak Republic),
Shuanggen Jin (China), Janis Kaminskis (Latvia),
Jeff Kennedy (USA), Jakub Kostelecky (Czech Republic),
Jaakko Mäkinen (Finland), J.N. Markiel (USA),
Emil Nielsen (Denmark), Tomasz Olszak (Poland),
Bjørn Ragnvald Pettersen (Norway), Rene Reudink (TheNetherlands), Jose Manuel Serna Puente (Spain),
Manuel Schilling (Germany), Heping Sun (China),
V.M. Tiwari (India), Christian Ullrich (Austria).

Commission 2 – Gravity Field

SC 2.2: Methodology for Geoid and PhysicalHeight Systems
Chair: Jonas Ågren (Sweden)
Vice-chair: Artu Ellmann (Estonia)
Terms of Reference
A global height reference frame with high accuracy andstability is required to determine the global changes of the
Earth. A major step towards this goal was taken by the
IAG resolution (No. 1) for the definition and realization of
an international Height Reference System (IHRS), adopted
at the IUGG 2015 meeting in Prague. It is now theintention that the IHRS will be globally realized using
geometric satellite methods, like GNSS, in combination
with gravimetrically determined geopotential values. The
latter can be derived using a global geopotential model
originating from the dedicated satellite gravity missions,complemented with terrestrial gravity and otherinformation to reduce the omission error. Traditional
levelling might also be integrated on a regional or local
scale. The IAG SC 2.2 aims at bringing together scientists
and geodesists concerned with methodological questions in
geoid and height determination, who in different ways
contribute to reach the above mentioned goal of a global
height system realisation and unification. It includes topics
ranging from regional gravimetric geoid determination to
the realization and implementation of IHRS in view of theexisting regional/local/national height system realisations.
Objectives
The IAG Sub-Commission 2.2 (SC2.2) promotes andsupports scientific research related to methodologicalquestions in geoid and height determination, both from thetheoretical and practical perspectives, concentrating
particularly on methodological questions contributing to
the realization of IHRS with the required sub-centimetre
accuracy. This includes for instance:x Realization of the International Height Reference
System (support of Joint Working Group 0.1.2)
x Implementation of the International Height Reference
Frame, height system unification.
x Studies on W0 determination.
x Studies on data requirements, data quality, distribution
and sampling rate to reduce the omission error to thesub-centimetre level in different parts of the world.
x Investigation of the theoretical framework required tocompute the sub-centimetre geoid (support of JSG 0.15)
x Investigation and benchmarking of alternative regional
geoid determination methods and software.

1013

x Studies on theoretical and numerical problems related tothe solution of the geodetic boundary value problems in
geoid determination,x Studies on time variations of the gravity field andheights due to Glacial Isostatic Adjustment (GIA) andland subsidence.
x Development of relativistic methods for potential
difference determination using precise atomic clocks(support of Joint Working Group 2.3)
x Investigating the role of traditional levelling in future
regional/local height system realisations.
Program of activities
x Organizing meetings and conferences.
x Inviting the establishment of Special Study Groups onrelevant topics.
x Reporting activities of SC2.2 to the Commission 2.
x Communication/interfacing
betweendifferentgroups/fields relevant to the realization of IHRS.

Structures for the Period 2015-2019

1014

Joint Working Groups of Sub-Commission 2.2

Goals and Objectives

JWG 2.2.1: Integration and validation of local geoid
estimates(joint with ISG, IGFS, ICGEM)

The objectives of the Working Group are to:x Study and define methodologies for merging local geoid
solutionsx Discuss and define proper procedure to assess the geoid
estimation precisionx Compare different geoid estimation methods
x Define general rules for geoid estimation in areas withsparse gravity data

Chair: Mirko Reguzzoni (Italy)
Vice-chair: Georgios Vergos (Greece)
Terms of Reference
Regional geoid estimates (in areas having e.g. extension ofsome degrees) can give a detailed description of the highfrequency geoid features. They are based on local gravity
databases and high resolution DTMs that allow toreconstruct the high frequency spectrum of the gravity
field, thus improving the global geopotential model
representation. Local geoid estimates are computed
following well-defined estimation methods that can give
reliable results. These estimates are frequently used inengineering applications to transform GPS derived
ellipsoidal heights into normal or orthometric heights.
Despite the fact that methodologies in geoid estimation
have a sound basis, there are still some related issues thatare to be addressed.
In comparing local geoid estimates of two adjacentareas inconsistencies can occur. They can be caused by thedifferent global geopotential models used in representing
the low frequency part of the gravity field spectrum and/or
the method that has been adopted in the geoid estimation
procedure. Biases due to a different height datum can also
be present. Thus proper procedures should be proposed andassessed to homogenize the two local solutions.
Validation of regional geoid is another issue that is to bebetter standardized. Usually the validation is based on
GPS/levelling data that are compared with the geoid
estimates. Differences between GPS/levelling andgeoid/quasi-geoid values are then fitted with polynomial
surfaces to account for reference frames discrepancies.
Statistics of the post-fit residuals are then considered as theestimates of the geoid precision. In this respect, someissues related to the fitting procedure could be better
defined and standardized.
Finally, another question to be investigated is thedefinition of procedures for local geoid estimates in areas
with sparse gravity data. The interactions existing among
the maximum degree of the global geopotential model, theDTM resolution, the local gravity database mean spatial
density, the estimation geoid grid step should be studied todefine some general best-practice rules.

Program of Activities
The Working Group activities will be developed following
the objective stating above. Particularly, based on thegeoid solution available at ISG, numerical tests will be
carried out. Members will be required to participate inthese tests with their own software/methodologies. Resultsof these tests will be discussed through the ISG website
and in face-to-face meeting to be held in connection withmajor geodesy related congresses.
Members
Mirko Reguzzoni (Italy), Chair
Georgios Vergos (Greece), Vice-chair
Hussein A. Abd-Elmotaal (Egypt)Franz Barthelmes (Germany)
Riccardo Barzaghi (Italy)
T. Bašić (Croatia)
Will Featherstone (Australia)
Gabriel Guimaraes (Brazil)
Jianliang Huang (Canada)
Cheinway Hwang (China-Taipei)
Shuanggen Jin (China)
Norbert Kühtreiber (Austria)
Marie-Françoise Lalancette (France)
Giovanna Sona (Italy)
Hasan Yildiz (Turkey)
Corresponding Member
Heiner Denker (Germany)

Commission 2 – Gravity Field

1015

SC 2.3: Satellite Gravity Missions

Program of Activities

Chair: Adrian Jäggi (Switzerland)
Vice-chair: Frank Flechtner (Germany)

The focus of this sub-commission will be to promote andstimulate the following activities:
x Generation of static and temporal global gravity fieldmodels based on observations by the satellite gravity
missions CHAMP, GRACE, GOCE, and the future
GRACE Follow-On mission, as well as optimum
combination with complementary data types (SLR,
terrestrial and air-borne data, satellite altimetry, etc.);x Investigation of alternative methods and new
approaches for global gravity field modelling, withspecial emphasis on functional and stochastic models
and optimum data combination;
x Identification, investigation and definition of enabling
technologies for future gravity field missions:observation types, technology, formation flights, etc.;
x Communication / interfacing with gravity field model
user communities (climatology, oceanography /altimetry, glaciology, solid Earth physics, geodesy, ...);x Communication/interfacing
with
other
IAG
organizations, especially the GGOS Working Group for
Satellite Missions and the GGOS Bureau for Standards
and Conventions

Terms of Reference
Sub-commission 2.3 promotes scientific investigations
concerning the dedicated satellite gravity field missions
CHAMP, GRACE, GOCE, and the future GRACE FollowOn mission, the development of alternative methods andnew approaches for global gravity field processing also
including complementary gravity field data types, as wellas interfacing to user communities and relevantorganizations.
Objectives
The successful launches of the German CHAMP (2000),the US/German GRACE (2002) and the ESA GOCE
(2009) missions have led to a revolution in global gravity
field mapping by space-borne observation techniques. Dueto the fact that they are the only measurement system
which can directly observe mass and mass transport in the
Earth system, they provide valuable contributions to manygeoscientific fields of application, such as geodesy,hydrology, oceanography, glaciology, and solid Earthphysics. These missions have proven new concepts andtechnologies, such as high-low satellite-to-satellite tracking(SST) using the GPS constellation, low-low SST based on
micro-wave ranging, and satellite gravity gradiometry(SGG), as well as space-borne accelerometry. GRACE has
produced consistent long- to medium-wavelength global
gravity field models and its temporal changes. GOCE
provided high-accuracy and high-resolution static gravity
field models. In combination with complementary gravity
field information from terrestrial data, satellite altimetry,an even higher spatial resolution can be achieved.
Additionally, based on challenging user requirements,
concepts of future gravity field missions are developed andinvestigated.

Structures for the Period 2015-2019

1016

SC 2.4: Regional Geoid Determination

SC 2.4a: Gravity and Geoid in Europe

Chair: Maria Cristina Pacino (Argentina)
Vice-chair: Hussein Abd-Elmotaal (Egypt)

Chair: Heiner Denker (Germany)
Terms of ReferenceTerms of Reference and Objectives
Sub-Commission 2.4 is concerned with the following areasof investigation:
x Regional gravity and geoid sub-commissions: data sets,
involved institutions, comparison of methods andresults, data exchange, comparison with global models,connection of regional models
x Gravimetric geoid modelling techniques and methods,
available software, new alternative geoid determination
techniques
x GPS/levelling
geoid
determination:
methods,
comparisons, treating and interpretation of residuals,common treatment of gravity and GPS/levelling for
geoid determinationx Geoid applications: GPS heights, sea surface
topography, integration of geoid models in GPS
receivers, vertical datums.
x Other topics: topographic effects, downward andupward continuation of terrestrial, airborne, satellite
data specifically as applied to geoid modelling.
Program of Activities
Sub-Commission 2.4 is going to initiate and coordinate
regional gravity and geoid sub-commissions. It willencourage and support the data exchange between agencies
and will assist local, regional and national authorities intheir projects of gravity field determination. It will help inorganizing courses and symposia for gravity field
determination.

The primary objective of the sub-commission is thedevelopment of improved regional geoid and quasigeoid
models for Europe, which can be used for applications in
geodesy, oceanography, geophysics and engineering, e.g.,height determination with GNSS techniques, vertical datum
definition and unification, dynamic ocean topography
estimation, geophysical modelling, and navigation. Anotheremerging field is related to the development of new opticalclocks in physics with projected relative accuracies at thelevel of 10-18, as in accordance with the laws of generalrelativity, such clocks are sensitive to the gravity potential
at the level of 0.1 m2/s2, equivalent to 1 cm in height.
The geoid and quasigeoid modelling will be based mainly
on terrestrial gravity and terrain data in combination withstate-of-the-art global geopotential models. In this context,
upgraded terrestrial data sets as well as the utilization of
new GRACE and GOCE based global geopotential models
led to significant improvements. The evaluation of the latest
European Gravimetric Geoid 2015 (EGG2015) by GNSS andlevelling data indicates an accuracy potential of 1 – 2 cm on anational basis, and 2 – 4 cm at continental scales, provided thathigh quality and resolution input data are available within
the area of interest. Further improvements can be expectedfrom the inclusion of upgraded gravity field data sets,
especially in areas with hitherto insufficient input data.
Program of Activities
x Utilization of state-of-the-art global geopotential models.
x Identification and acquisition of new terrestrial data
sets, including gravity, terrain, and GPS/levelling data.
x Merging and validation of all data sets.
x Investigation of refined mathematical modelling
techniques and numerical tests.
x Computation of new geoid and quasigeoid models.
x Evaluation of the results by GNSS/levelling data.
x Study of applications, such as vertical datum definition
and unification, dynamic ocean topography estimation,
ground truth for optical clocks, etc.
Delegates
The SC2.4a cooperates with national representatives frommost of the countries in Europe. The existing contacts andsuccessful cooperation with the respective persons and national
and international agencies shall be continued and extended.

Commission 2 – Gravity Field

SC 2.4b: Gravity and Geoid in South America
Chair: Maria Cristina Pacino (Argentina)
Vice-chair: Denizar Blitzkow (Brazil)
Terms of Reference and Objectives
The Sub Commission 2.4b entitled Gravity and Geoid inSouth America, as part of the Commission 2 of IAG, wasestablished as an attempt to coordinate efforts to establish a
new Absolute Gravity Network in South America, to carryout gravity densification surveys, to derive a geoid modelfor the continent as a height reference and to support localorganizations in the computation of detailed geoid models
in different countries.
Besides, a strong effort is being carried out in several
countries in order to improve the distribution of gravity
information, to organize the gravity measurements in thecontinent and to validate the available gravity
measurements.
The main objectives of the project are:x To re-measure existent absolute gravity stations and toencourage the establishment of new stations.
x To validate fundamental gravity network from different
countries in order to establish a single and common
gravity network for South America.
x To adjust national gravity networks and to link them
together.
x To obtain and to maintain files with data necessary forthe geoid computation like gravity anomalies, digitalterrain models, geopotential models and satellite
observations (GPS) on the levelling network of different
countries.
x To provide a link between the different countries andthe IGFS in order to assure access to proper softwareand geopotential models for local geoid computation.
x To compute a global geoid model for South and Central
America using the available data. To encouragecountries to cooperate by releasing data for this purpose.
x To encourage and eventually support local organizations
in different countries endeavouring to increase thegravity data coverage, to improve the existing digitalterrain models, to carry out GPS observations on thelevelling network and to compute a high resolution
geoid.
x To organize and/or encourage the organization ofworkshops, symposia or seminars on gravity and geoid
determination in South America.
x To test and to use future geopotential models derived
from the modern missions (GRACE and GOCE) as wellas any new combined model (e.g. EGM2008).

1017

x To support the IAG Sub-Commission 1.3b (Reference
Frame for South and Central America, SIRGAS) in theactivities related to the unification of the existingvertical datums.
x Establish close connections with SC2.4c (Gravity andGeoid in North and Central America) to have a goodoverlap of data coverage in Central America and the
Caribbean.
Delegates
Denizar Blitzkow (Brazil)
Oscar Carranco (Ecuador)
Henry Montecino Castro (Chile)
Eduardo Andrés Lauría (Argentina)
Roberto Teixeira Luz (Brasil)
Silvia Alicia Miranda (Argentina)
Ana Crisitina Oliveira Concoro de Matos (Brasil)
Maria Cristina Pacino (Argentina)
Ivonne Gatica Placencia (Chile)
Norbertino Suárez (Uruguay)
Jorge Faure Valbi (Uruguay)Structures for the Period 2015-2019

1018

SC 2.4c: Gravity and Geoid in North and Central
America
Chair: Marc Véronneau (Canada)
Vice-chair: David Avalos (Mexico)
Terms of Reference and Objectives
The primary objective of this Sub-commission is thedevelopment of a regional gravity field and geoid model
covering the region of North America and Central America
by 2022 in order to achieve a common vertical datum. The
region involved will encompass Iceland, Greenland,
Canada, the U.S.A. (including Alaska and Hawaii),
Mexico, countries forming Central America, the Caribbean
Sea and the northern parts of South America. This model
will serve as the official realization of the vertical datum
for countries that want to adopt it.
The intention is to ensure that a suitable North
American Geoid is developed to serve as a common datum
for every-one in the region. All countries in the region
would be served by having access to a common model fortranslating oceanographic effects to terrestrial datums forvarious scientific, commercial, engineering and disaster
prepared-ness applications. Likewise, it shall serve as thebasis for the forthcoming International Great Lakes
Datumin 2022 (IGLD 2020).
The achievement of a geoid model for North andCentral America will be accomplished by coordinating
activities among agencies and universities with interest in
geoid theory, gravity, gravity collection, gravity fieldchange, geophysical modelling, digital elevation models(DEM), digital density models (DDM), altimetry, dynamic
ocean topography, levelling and vertical datums. Of
particular interest will be relating geoid and ocean
topography models to ocean topography and tidal
benchmarks, taking advantage of the recent satellite
altimetry and geopotential field products.
The determination of a geoid model for North andCentral America is not limited to a single agency, which
will collect all necessary data from all countries. The Subcommission encourages theoretical diversity in thedetermination of a geoid model among the agencies. Eachagency takes responsibility or works in collaboration withneighbouring countries in the development of a geoid
model for their respective country with an overlap (as large
as possible) over adjacent countries. Each solution will becompared, the discrepancies will be analyzed, and theconclusions will be used to improve on the next model.

Program of Activities
The Sub-commission will support geoid activities incountries where geoid expertise is limited by encouraging
more advanced members to contribute their own expertiseand software. The Sub-commission will encourage training
and education initiative of its delegates (e.g., IGeS geoid
school, graduate studies and IPGH technical cooperation
projects). Starting 2011 the Sub-commission will organize
regular meetings with representatives of Central American
and Caribbean countries to promote an increase ofexpertise as well as to create a wide network of specialists.
The chair (or a delegate representative) of the Subcommission will meet with the equivalent European andSouth American projects to discuss overlap regions and towork towards agreements to exchange data. The delegatesof the Sub-commission will keep close contact with all
related Study Groups of the IAG. The Sub-commission is
open to all geodetic agencies and universities across North
and Central America with an interest in the development ofa geoid model for the region. The meetings of the Subcommission 2.4c are open to everyone with interests ingeodesy, geophysics, oceanography and other related
topics.
The delegates will communicate primarily using e-mail.
In addition, starting on November 9, 2015, Canada (CGS),
USA (NGS) and Mexico (INEGI) will organize audio /video conferences every four weeks to discuss activity
plans and present results. The sub-commission also plansto organize annual meetings if enough delegates can bepresent. Preferably, these meetings will be held during
international conferences;. Minutes of meetings will be
prepared and sent to all delegates of the Sub-commission.
Delegates
Alvaro Alvarez (Costa Rica)
David Avalos (Mexico)
Christopher Ballesteros (Panama)
Carlos E. Figueroa (El Salvador)
Rene Forsberg (Denmark)Jianliang Huang (Canada)
Wilmer Medrano (Nicaragua)
Oscar Meza (Honduras)
Laramie Potts (USA)
Vinicio Robles (Guatemala)Dan Roman (USA)
Marc Véronneau (Canada)
Yan Min Wang (USA)
Anthony Watts (Cayman Islands)

Commission 2 – Gravity Field

1019

SC2.4d: Gravity and Geoid in Africa

Delegates

Chair: Hussein Abd-Elmotaal (Egypt)

Hussein Abd-Elmotaal (Egypt)
Mostafa Abd-Elbaky (Egypt)
Ahmed Abdalla (Sudan)
Francis Aduol (Kenya)
Mostafa Ashry (Egypt)
Jose Almeirim (Mozambique)
Joseph Awange (Kenya)Ludwig Combrinck (South Africa)
Benahmed Daho (Algeria)
Tsegaye Denboba (Ethiopia)
Hassan Fashir (Sudan)
Walyeldenn Godah (Sudan)
Godfrey Habana (Botswana)
Ayman Hassan (Egypt)
Bernhard Heck (Germany)
Addisu Hunegnaw (Ethiopia)
Saburi John (Tanzania)
Adekugbe Joseph (Nigeria)
J.B.K. Kiema (Kenya)
Norbert Kühtreiber (Austria)
Ismail Ateya Lukandu (Kenya)
Atef Makhloof (Egypt)
Charles Merry (South Africa)
Albert Mhlanga (Swaziland)Peter Nsombo (Zambia)
Karim Owolabi (Namibia)
Francis Podmore (Zimbabwe)
Solofo Rakotondraompiana (Madagascar)
Kurt Seitz (Germany)
Prosper Ulotu (Tanzania)

Terms of Reference
The African Gravity and Geoid sub-commission (AGG)
belongs to the Commission 2 of the International
Association of Geodesy (IAG). The main goal of theAfrican Gravity and Geoid sub-commission is to determine
the most complete and precise geoid model for Africa thatcan be obtained from the available data sets. Secondary
goals are to foster cooperation between African geodesists
and to provide high-level training in geoid computation to
African geodesists.
Objectives and Activities
The objectives and activities of the sub-commission aresummarized as follows:x Identifying and acquiring data sets - gravity anomalies,
DTMs, GPS/levelling.
x Training of African geodesists in geoid computation.
x Merging and validating gravity data sets.
x Computing African geoid models.
x Evaluating the computed geoid models using
GPS/levelling data.
x Updating the geoid models using new data/strategies toobtain better geoid accuracy (dynamic process).

Structures for the Period 2015-20191020

SC 2.4e: Gravity and Geoid in the Asia-Pacifica) Gravity and Related Data

Chair: Jay Hyoun Kwon (Korea)
Vice-chair: Cheinway Hwang (China-Taipei)

Explore ways in which we may
x Share available gravity data (e.g. via International
Gravity Bureau)x Share available DEMs along common borders (National
Geodetic Authorities)
x Combine resources for terrestrial gravity surveys alongcommon borders
x Combine resources for airborne gravity surveys in theregion.

Context
Depending on one’s definition of the Asia-Pacific (AP)region, this SC could cover as many as 48 counties.
Moreover, these countries are very diverse in terms oflanguage, political persuasions, governments and wealth.
This poses a significant challenge for the exchange ofgravity and geoid data and expertise.
Not only unique to the AP region, the management andadministration of gravity and the geoid can be vastlydifferent in each country, making the coordination of sucha group challenging. Taking Australia as an easy example,
the gravity database is administered by a different
government division to the administration of the national
quasigeoid model.
Terms of Reference and Objectives
Promote the cooperation in and knowledge of gravity,
geoid and closely related studies in the Asia-Pacific region.
A group of delegates comprises one member from eachparticipating country. Because of the need to carry national
authority, the national member is logically the officer inthe country’s geodetic authority responsible for its
quasi/geoid and/or vertical datum matters.
Because of the synergy that exists between theobjectives of this SC and those of the Working Group of
the United Nations Global Geospatial Information
Management for Asia and the Pacific ((UNGGIM-AP), it
is logical to liaise with this working group.
Program of Activities
Liaise with the Geodesy Working Group of the UNGGIMAP and other nations in the Asia-Pacific region, initiallythrough the production of a flier that outlines the benefitsof cooperation and data sharing.
Audit, document and catalogue the gravity and geoidrelated that exists – including airborne campaigns. It is also
important to establish a protocol for sharing the data.
National authorities may be reluctant to give all the data
available and at the precision available. It should bepossible for geoid evaluation purposes, however, todecrease the resolution and accuracy of data shared alongcommon borders without either comprising the precision of
the geoid significantly, or the security of the national data shared.

b) Quasi/geoid Control
Explore ways in which countries of the region may
cooperate byx Sharing geometric (GNSS/levelling and verticaldeflections) geoid control datax Combining efforts in global GNSS campaigns
x Undertaking joint campaign for the connection ofregional vertical datums.
c) Education & Research
Encourage and sponsor, for the region,x Meetings and workshops, in cooperation with theInternational Geoid Service, to foster understanding in
the evaluation and use of gravimetric quasi/geoids, andin their application to efficient height determination
with GNSS.
x Technical sessions in scientific and professional
conferencesx Research into matters of common concern/interest.
Delegates
John Dawson (Australia)
Will Featherstone (Australia)
Wen Hanjiang (Chaina)
Cheinway Hwang (China-Taipei)
Jay Hyoun Kwon (Korea)
Basara Miyahara (Japan)
Kamaludin Omar (Malaysia)
Ibnu Sofian (Indonesia)
Chalermchon Satirapod (Thailand)Commission 2 – Gravity Field

SC 2.4f: Gravity and Geoid in Antarctica
Chair: Mirko Scheinert (Germany)
Terms of Reference and Objectives
Antarctica is the region that still features the largest data
gaps in terrestrial gravity. Global gravity field solutions
suffer from the lack of terrestrial data in Antarctica as well
as from the polar data gap originating from the orbit
inclination of dedicated satellite gravity field missions(esp. GOCE with a polar data gap of 1,400 km diameter).
However, a certain coverage of terrestrial gravity data in
Antarctica coverage exists. These data are heterogeneousand exhibit inconsistencies. Nevertheless, these are needed
for the global high-resolution determination of the Earth’s
gravity field and/or for a validation of global gravity fieldmodels. Finally, terrestrial gravity data need to be applied
for a regional improvement of the Antarctic geoid.
Due to the vast extension of the Antarctic continent, its
hostile environment and the difficult logistic conditions it
is a long-lasting task to close the Antarctic data gaps interrestrial gravity. AntGG shall pursue this objective andshall facilitate the necessary coordination to release
gridded gravity datasets for Antarctica. It plays animportant role to improve the cooperation between all
interested scientists of geodesy and of neighboring
disciplines, mainly geophysics.
Program of Activities
x Promoting the collection of surface and airborne gravity
data in Antarctica;
x Promoting new gravity surveys in Antarctica, especiallyairborne gravimetry;x Promoting the establishment and (re-)measurement ofreference gravity stations utilizing absolute gravity
meters;x Promoting the scientific exchange of latest
developments in technology (esp. airborne gravimetry)and data analysis;x Evaluation of existing and new surface and airborne
gravity data, validation of global gravity field models in
Antarctica;x Investigation of optimum strategy for the combinationof gravity data of different sources;
x Release of gridded gravity anomaly dataset(s) for
Antarctica to the scientific public (first release plannedfor 2015/2016, subsequent updates are planned whendata availability improves adequately);1021

x Organization of special workshop on airborne geodesy
and geophysics (especially aerogravimetry) with focus
on Antarctica;
x Focus group for all scientists interested in Antarctic
gravity and geoid, and cooperation with similar data
initiatives, especially within the Scientific Committee
on Antarctic Research (SCAR);
Delegates
Don Blankenship (USA)
Alessandro Capra (Italy)
Koichiro Doi (Japan)
Graeme Eagles (Germany)
Fausto Ferraccioli (UK)
Christoph Förste (Germany)
René Forsberg (Denmark)Larry Hothem (USA)
Wilfried Jokat (Germany)
Gary Johnston (Australia)
Steve Kenyon (USA)German L. Leitchenkov (Russia)
Jaakko Mäkinen (Finland)
Yves Rogister (France)
Mirko Scheinert (Germany)
Michael Studinger (USA)
Associates
Matt Amos (New Zealand)Structures for the Period 2015-20191022

SC 2.5: Satellite Altimetry

Objectives

Chair: Xiaoli Deng (Australia)
Vice-chair: C.K. Shum (USA)Sub-Commission 2.5 will:x Establish a close link between this sub-commission andthe International Altimeter Service (IAS) and data
product providers, in order to (1) organise scientificforums to discuss new results, (2) bring new algorithms
from expert research into data production, and (3)encourage development of data products that more
directly facilitate cross-disciplinary applications using
satellite altimetry;x Promote innovative applications of satellite altimetry,
includingevaluations
andcross-disciplinary
applications of future satellite altimetry;x Continue developing techniques to improve altimeterdata quality, aiming towards new data products incoastal zones including coastal ocean, estuaries andinland water bodies;
x Focus on capabilities of the very high along-track
spatial resolution from new SAR and SARAL altimeters
for precisely modelling the marine gravity field, themean sea surface, bathymetry and ocean mean dynamic
topography, as well as temporal variations of sea level
induced by solid Earth processes, climate change andthe global terrestrial water cycle;
x Promote cross-disciplinary research on the shapes andtemporal variations of land/ice/ocean surfaces, such as
studies of long-term ocean variability, regional andglobal sea level changes, mountain glaciers/ice-sheet
ablations/accumulations,permafrost
degradation,
coastal and ice-shelf ocean tides, vertical displacements
at major tectonic-active zone, land subsidence and othergeophysical processes; andx Establish a specific connection with relevant altimetry
observing systems in IAG’s GGOS.

Terms of Reference
The long-term time series of altimeter measurements has
revolutionised the knowledge of many interdisciplinaryscientific research fields including the marine gravity field,
oceanic dynamics, terrestrial hydrology, ice sheet massbalance, sea level changes, and solid Earth geodynamics.
Conventional Ku-band altimetry is now a mature techniqueafter more than 24 years of continuous observations andwill be further applied in Jason-3. New missions
employing Ka-band radar (SARAL/AltiKa), delay Doppler
SAR altimetry (CryoSat-2, Sentinel-3 and Jason-CS) andlaser altimetry (ICEsat-1/-2 including a photon counting
instrument) are providing and will provide higher
resolution observations of the cryosphere, sea-ice, icecovered oceans, open oceans and inland water bodies. The
future Surface Water and Ocean Topography (SWOT)
altimeter mission, to be launched in 2020, is expected to
substantially improve our understanding of ocean
circulation and surface water hydrology at finer scales.
Another altimetry technology under development is
GNSS-R altimetry or reflectometry, which also hasapplications in the remote sensing of ocean wind retrieval,soil moisture, land cover, snow depth, and ocean surface
topography.
With these existing and new technological advances inaltimetry, novel observations are and will be driving
technological leaps forward for satellite geodesy andoceanography. At the same time, they will bridge anobservational gap on a spatio-temporal domain critical forsolving interdisciplinary problems of considerable societal
benefit. Therefore, the purpose of this IAG subcommission is to promote innovative research using
historic and future altimeter observations to study local,
regional, and global geophysical processes, with emphasison emerging cross-disciplinary applications using satellite
altimetry, and in combination with other in situ data sets
and techniques including hydrography data, SAR/InSAR
and GRACE/GOCE. The research results and potential
data products will benefit IAG’s Global Geodetic
Observing System.

Program of Activities
This sub-commission will organize independent workshops
or special sessions in major meetings to promote altimetricapplications in interdisciplinary earth sciences, and toincrease the visibility of IAG in altimetric science. Special
study groups may be established to investigate important
issues.

Commission 2 – Gravity Field

SC 2.6: Gravity and Mass Transport in the
Earth System
Chair: Jürgen Kusche (Germany)
Vice-chair: Isabelle Panet (France)
Terms of Reference
Spatial and temporal variations of gravity are related to the
dynamics of the Earth’s interior, land surface, oceans,cryosphere, and atmosphere. The geoid maps equilibrium
dynamic processes in the ocean and in the Earth’s mantle
and crust, and large-scale coherent changes in gravity
result from mass transports in atmosphere, hydrosphere,
cryosphere, and the ocean, and across these. The gravity
field, derived from terrestrial and space gravimetry (SLR,
GRACE, GOCE, …) with unprecedented accuracy andresolution, provides a unique opportunity to investigate
gravity-solid earth coupling, the structure of the globe fromthe inner core to the crust, and mass transports such as
those associated within the global water cycle. Gravimetry
also contributes to a better understanding of theinteractions in the Earth system, and to its response to
climate change and the anthropogenic fingerprint.
Objectives
x To further the understanding of the physics anddynamics of the Earth’s interior, land surface,cryosphere, oceans and atmosphere using gravity andother geophysical measurement techniques.
x To promote the study of solid Earth mass (re)distribution from gravity and gravity gradient tensor
variations, e.g. crust thickness, isostatic Moho
undulation, mass loadings, basin formation, thermal
effects on density, deformations, as well as interactions
with the Earth’s interior.
x To advance the investigation of mass transports in the
Earth system, and, in particular, to contribute to theunderstanding of the global water cycle, of the storageof water in cryosphere and hydrosphere, of the fluxes
across these sub-systems and the atmosphere, and of sea
level.
x To contribute to the operationalization of mass transportmonitoring, e.g. for water resource monitoringx To stimulate new applications of gravimetry and masstransport monitoring, e.g. in climate model validationand detection of anthropogenic effects
x To aid in method benchmarking and reconciliation of
conflicting results

1023

x To communicate with gravity-related communities inoceanography, hydrology, cryosphere, solid Earth,
geodesy...)Program of Activities
The sub-commission will establish Work Groups (WGs)on relevant topics. The Steering Committee will work
closely with members and other IAG commissions andsub-commissions to obtain mutual goals. Also it will
promote and jointly sponsor special sessions at IAG
Symposia and other workshop/conferences.

Structures for the Period 2015-2019

1024

Joint Working Groups of Sub-Commission 2.6

Objectives:

JWG 2.6.1: Geodetic observations for climate model
evaluation(joint with Commission 1)

x To further the understanding of the potential of gravity
and other geodetic measurements for the observation,
analysis and validation of fluxes across the landatmosphere continuum.
x To promote the cross-disciplinary study of these fluxes
through comparison and possibly integration ofgravimetric and hydro-meteorological measurements
such as soil moisture, precipitation, water vapor, or
evapotranspiration (e.g. latent and sensible heat flux)
x To advance the improvement of climate models(including land surface models), climate monitoring
systems and analyses/reanalyses through space-based
measurements of gravity
x To stimulate discussion between the gravity community
and the land surface modelling, atmospheric modellingand climate communities

Chair: Annette Eicker
Terms of Reference
Spatio-temporal variations of gravity are related to the
dynamics of the Earth’s interior, land surface andhydrosphere, oceans, cryosphere, and atmosphere. Due to
its large signal, in particular the variations of continental
water storage have been observed and analyzed in recent
years from space gravimetry. In addition, the temporalchange of gravity has been successfully related to net flux
at the land-atmosphere interface, the sum of precipitation,
evapotranspiration and runoff/discharge. Another powerfulgeodetic technique is microwave remote sensing of theatmosphere; in particular global and regional water vapor
trends can be determined from GNSS measurements andother space-geodetic data and, e.g. radiosonde information.
Global and regional climate models simulate thecoupled atmosphere-land surface- ocean system on decadal
to century-long time scales. Since the water cycle iscoupled to the energy and carbon cycles and criticallycontrols biomass evolution, their ability of correctly
simulating variability, frequency and trends of climate
variables like land and sea surface temperature andprecipitation and their response to anthropogenic forcing
depend critically on their skills in representing the water
cycle. As a result, the representation of the water cycle,
including groundwater and human modifications likepumping and irrigation, has gained much attention inrecent years. This holds also for climate monitoring
activities that rather focus on assessing the current state of
the Earth’s climate than on the future. Initialization ofclimate model runs, detection and attribution of theanthropogenic
fingerprint,orreanalysisofatmospheric/land surface modelling all depend on accurate
observations of the current water cycle.
The gravity field, derived from GRACE and in the near
future from GRACE-FO and other missions with
unprecedented accuracy and resolution, provides a unique
opportunity to validation of global and regional climate
models. Different from ‘GRACE-Hydrology’, the focus of
this WG would be on the observation, analysis andvalidation of fluxes across the land-atmosphere interface,and not on water resources. We would also aim atdeveloping synergies between gravimetric, microwavebased, and other geodetic climate model validation efforts.

Program of Activities
x The WG will create opportunities for communicationand discussion through suggesting/organizing sessions
at international meetings and conferences
x The WG will develop reference (best-practice) methods
for evaluating/improving climate models from geodetic
data and publish these methods (e.g. in a ‘white paper’)x The WG will seek to organize a special issue on its
topic in an appropriate international journal

Members
Carmen Böning (USA)Marie-Estelle Demory (UK)
Albert van Dijk (Australia)
Henryk Dobslaw (Germany)
Annette Eicker (Germany)
Wei Feng (China)
Vincent Humphrey (Switzerland)
Harald Kunstmann (Germany)
J.T. Reager (USA)Anne Springer (Germany)
Paul Tregoning (Australia)

Commission 2 – Gravity Field

1025

Working Groups of Sub-Commission 2.6

Members

WG 2.6.1: Potential Field modeling with PetrophysicalsupportOrlando Alvarez (Argentina)
Valeria Barbosa, (Brazil)
Carla Braitenberg (Italy)
Jörg Ebbing, (Germany)
Christian Hirt (Germany)
Erik Ivins (USA)Juanggen Jin (China)
Jon Kirby (Australia)
Rezene Mahatsente (USA)
Daniele Sampietro, (Italy)
Sabine Schmidt (Germany)
Holger Steffen (Sweden)
Leonardo Uieda (Brazil)
Xiapoping Wu (USA)

Chair: Carla Braitenberg (Italy)
Terms of Reference
The WG is concentrated on developing and promoting
methods and software that are needed for a fullunderstanding of the Earth static and variable gravity andgradient field. Due to the similarity in the gravity andmagnetic potential field equations and the recent SWARM
mission, the magnetic field modeling is also considered. At
the present stage of knowledge it is recognized that apetrologic modeling of density should be considered inorder to reduce ambiguity of the density models of crustand mantle. The group will seek petrological support toassist in developing a geophysically oriented petrological
software for density, magnetic susceptibility and seismic
velocity modeling. The output should be usable for further
modeling as input for 3D lithosphere and mantle modeling.
The working group intends to validate potential fieldmodeling software that is free-share. Herefore a series ofbenchmark models will be collected.
The WG promotes studies and research of potential fieldterrestrial and satellite data for crust and mantle modeling.
Objectives:x Validation of potential field modelling softwarex Promote development of geophysical oriented
petrological
softwarefordensity,magnetic
susceptibility, seismic velocity modeling. Output should
be usable for further modeling as input for 3D
lithosphere and mantle modeling.
x Define benchmark models for validation of softwarex Organization of scientific workshops and meetings forthe discussion of up to date modeling methods ofpotential fields and their time variations

Structures for the Period 2015-2019

1026

Joint Working Groups of Commission 2
JWG 2.1: Relativistic Geodesy: Towards a new geodetic
technique(joint with Commission 1, ICCT)
Chair: Jakob Flury (Germany)
Vice-chair: Gerard Petit (France)
Terms of Reference
In recent years major technology breakthroughs on thefields of optical frequency standards and optical frequency
transfer have been achieved, which provide a new basis for
relativistic geodesy. Optical frequency standards at theleading National Metrology Institutes today have relative
frequency inaccuracies in the order of 10-17 to 10-18
range, and long-distance optical frequency transfer throughphase-stabilized optical fiber has been demonstrated evenwith a relative frequency inaccuracy at the 10-19 level.
The current, very dynamic activities on the field of opticalfrequency transfer are expected to pave the way towards
continental or even global clock networks. Thisdevelopment will contribute to a redefinition of the SI
second based on optical standards, and it could allow tying
height reference and height networks to atomic standards.
In addition, upcoming space missions such as Microscopeand GRACE Follow-On will provide measurements at an
accuracy level that is very relevant for relativistic geodesy.
The Joint Working Group 2.1 will foster the exchange on
concepts and methods in relativistic geodesy and will
promote the development of clock networks and their use
for relativistic geodesy. This requires strong links withtime and frequency metrology and, in this aim, the JWG
will establish liaisons with the Consultative Committee on
Time and Frequency (CCTF) of BIPM to enhancecommunication and coordination. Within IAG, the group is
joint and with IAG Sub-Commission 1-2 on Global
Reference Frames to enhance communication andcoordination.
Goals and Objectives
x Act as interface between groups in geodesy (gravity
fields, reference frames…) and in time and frequency
metrology (clock development, clock comparisons …);
x Provide a platform to promote the further development
and application of relativistic geodesy, e.g. in physics,
astronomy and other fields of geodesy and metrology;
x Foster the geodetic interests in the realization of theconcept of relativistic geodesy;x Develop an optimal strategy for the installation andanalysis of clock networks and for the combination ofclock data with classical geodetic data (e.g. for heightsystems);x Advocate the implementation of a clock network ofsufficient capability to obtain data products essential forgeodetic applications;x Study the use of clock networks in space;
x Provide relevant information for the geodetic
community including key contacts and links;
x Organize meetings and sessions on relativistic geodesy;x Prepare a document on the perspectives and applicationsof relativistic geodesy.
Program of Activities
The JWG 2.1 will work on meeting these objectives. In
particular, the group will meet regularly during major
conferences on geodesy and on time and frequency
metrology, such as IAG Scientific Assembly, IUGG
General Assembly, IFCS, EFTF. If needed, dedicatedmeetings will be organized. The group will exchange
information and discuss questions on measurement
techniques, standards, and analysis methods. The groupwill foster communication and coordination related tomeasurement campaigns and infrastructure in clock
networks and Relativistic Geodesy. If appropriate, thegroup will make recommendations on methods ofmeasurement and analysis.
Members
Jakob Flury (Germany), Chair
Gerard Petit (France), Vice-chair
Geoff Blewitt (US)Claude Boucher (France)
Pascale Defraigne (Belgium)
Pacome Delva (France)
Gesine Grosche (Germany)
Claus Lämmerzahl (Germany)
Christian Lisdat (Germany)
Jürgen Müller (Germany)
Pavel Novak (Czech Republic)
Paul Eric Pottie (France)
Bijunath Patla (US)Nikos Pavlis (US)Stefan Schiller (Germany)
Piet Schmidt (Germany)
Pieter Visser (The Netherlands)Peter Wolf (France)

Commission 3 – Earth Rotation and Geodynamics

1027

Commission 3 – Earth Rotation and Geodynamics
President: Manabu Hashimoto (Japan)
Vice President: Cheng-Li Huang (China)
http://www.rcep.dpri.kyoto-u.ac.jp/iag-commission3/Commission_3.htm

Terms of Reference
Geodynamics is the science that studies how the Earth
moves and deforms in response to forces acting on the
Earth, whether they derive from outside or inside of ourplanet. This includes the entire range of phenomena
associated with Earth rotation and Earth orientation such aspolar motion, Universal Time or length of day, precession
and nutation, the observation and understanding of which
are critical to the transformation between terrestrial andcelestial reference frames. It also includes tidal processes
such as solid Earth and ocean loading tides, and crust andmantle deformation associated with tectonic motions andisostatic adjustment etc.
During the last few decades many geophysicists have cometo use geodynamics in a more restricted sense to address
processes such as plate tectonics and postglacial reboundthat are dominantly endogenic in nature. Because the Earth
as a mechanical system responds to both endogenic andexogenic forces, and because these responses are
sometimes coupled, Commission 3 studies the entire rangeof physical processes associated with the motion and thedeformation of the solid Earth. The purpose ofCommission 3 is to promote, disseminate, and, whereappropriate, to help coordinate research in this broad arena.
Sub-Commission 3.1 (Earth Tides and Geodynamics)
addresses the entire range of tidal phenomena including its
effect on Earth rotation. Sub-Commission 3.2 (Crustal
Deformation) addresses the entire range of global andregional crustal deformation including intraplatedeformation, the earthquake deformation cycle, aseismic
phenomena such as episodic tremor and slip, and volcanic
deformation. Sub-Commission 3.3 (Earth Rotation andGeophysical Fluids) addresses the space-time variation of
atmospheric pressure, seafloor pressure and the surface

loads associated with the hydrological cycle, and Earth's(mainly elastic) responses to these mass redistributions.
Sub-Commission 3.4 (Cryospheric Deformation) addresses
the Earth's instantaneous and delayed responses to ice masschanges, including seasonal (cyclical) mass changes andprogressive changes associated with climate change. This
group also studies postglacial rebound at all spatial scales
and the elastic deformation taking place in the near-field ofexisting ice sheets and glaciers. Sub-Commission 3.5(Tectonics and Earthquake Geodesy) addresses theintegration of space and terrestrial approaches for studying
the kinematics and mechanics of tectonic plate boundary
zones, and in particular of the Eurasian/African/Arabianboundary zone.
Commission 3 interacts with GGOS, otherCommissions and Services of the IAG as well as withother organizations such as the International Astronomical
Union (IAU). For example, the recent space mission
GRACE has expanded our common interests with IAG
Commission 2 (Gravity Field) since temporal changes ingravity are associated with both the drivers of Earthdeformation (e.g. changing ice and loads) and with Earth's
response to these and other forcing.

Objectives
x To promote cooperation and collaboration on the theory,modelling and observation of Earth rotation andgeodynamics.
x To ensure development of research in Earth rotation andgeodynamics by organizing meetings, symposia, andsessions at conferences and general assemblies, bycreating working groups on specific topics, and byencouraging the exchange of ideas and data and theStructures for the Period 2015-20191028

comparison of methods and results with the goal of
improving accuracy, content, methods, theories, andunderstanding of Earth rotation and geodynamics.
x To serve the geophysical community by facilitatinginteractions with organizations that provide the dataneeded to study Earth rotation and geodynamics.

Structure

Joint Working Groups
JWG 3.1: Theory of Earth Rotation and Validation(joint with IAU)
Chair: José Ferrándiz (Spain)
JWG 3.2: Constraining Vertical Land Motion of Tide
Gauges(joint with Commission 1)
Chair: Alvaro Santamaría-Gómez (France)

Sub-Commissions
SC 3.1:
SC 3.2:SC 3.3:SC 3.4:
SC 3.5:

Earth Tides and Geodynamics
Chair: Janusz Bogusz (Poland)
Crustal Deformation
Chair: Zheng-Kang Shen (China)
Earth Rotation and Geophysical Fluids
Chair: Jianli Chen (USA)
Cryospheric Deformation
Chair: Shfaqat Abbas Khan (Denmark)Tectonics and Earthquake Geodesy
Chair: Haluk Ozener (Turkey)

Program of Activities
Commission 3 fosters and encourages research in the areasof its sub-entities by facilitating the exchange of
information and organizing symposia, either independently
or at major conferences in geodesy or geophysics. Some
events will be focused narrowly on the interests of the subcommissions and other entities listed above, and others
will have a broader commission-wide focus.

Joint Study Groups

Steering Committee

JSG 0.16 Earth’s inner structure from combined geodetic
and geophysical sources(joint with Commission 2 and ICCT, description
see ICCT)
Chair: R. Tenzer (China)

President Commission 3: Manabu Hashimoto (Japan)
Vice President Comm. 3: Cheng-Li Huang (China)
Chair Sub-Comm. 3.1:
Janusz Bogusz (Poland)
Chair Sub-Comm. 3.2:
Zheng-Kang Shen (China)
Chair Sub-Comm. 3.3:
Jianli Chen (USA)
Chair Sub-Comm. 3.4:
Sh. Abbas Khan (Denmark)Chair Sub-Comm. 3.5:
Haluk Ozener (Turkey)
Representative of IERS: Brian Luzum (USA)
Representative of IGFS: Riccardo Barzaghi (Italy)
Representative of GGOS: Richard Gross (USA)Member-at-Large:
José Ferrándiz (Spain)
Member-at-Large:
Alvaro Santamaría-Gómez(France)

JSG 0.19 Time series analysis in geodesy(joint with ICCT and GGOS, description see
ICCT)
Chair: W. Kosek (Poland)
JSG 0.21 Geophysical modelling of time variations indeformation and gravity(joint with Commission 2 and ICCT, description
see ICCT)
Chair: Y. Tanaka (Japan)
JSG 3.1: Intercomparison of Gravity and Height Changes(joint with IGFS, Commissions 1 and 2)
Chair: Severine Rosat (France)

Commission 3 – Earth Rotation and Geodynamics

Sub-Commissions
SC 3.1: Earth Tides and Geodynamics
Chair: Janusz Bogusz (Poland)
Vice-Chair: Carla Braitenberg (Italy)
Terms of Reference
SC 3.1 addresses the entire range of Earth tidal phenomena
and dynamics of the Earth, both on the theoretical as wellas on the observational level. Earth tide observations havea very long tradition. These observations led to thediscovery of the Earth’s elasticity which allows
deformation and variations in Earth orientation androtation parameters. The phenomena responsible for thesevariations include the full range of periodic and nonperiodic occurrences such as solid Earth tides, ocean andatmospheric tidal loading, ocean, atmospheric andhydrospheric non-tidal effects as well as plate tectonics
and intraplate deformation. The periods range from seismic
normal modes over to the Earth tides and the Chandler
Wobble and beyond. Thus, the time scales range fromseconds to years and for the spatial scales from local tocontinental dimensions.
As tidal friction is affecting Earth rotation, all thephysical properties of the Earth contribute to the
explanation of this phenomenon. Therefore, the researchon tidal deformation due to changes of the tidal potential aswell as ocean and atmospheric loading are a prerequisite toanswer such questions. Further, direct and indirect tidal
phenomena affect the position of fiducial sites and have to
be corrected to provide accurate spatial referencing. Suchreferencing is needed for the observation and monitoringof changes of the Earth’s surface at global, regional andlocal scales. Therefore, there is a considerable contributionof tidal research to global geodynamics and climate change
by providing important constraints to geophysical models.
Modern gravimetry is improving our knowledge on the
Earth’s: global gravity field and its temporal variations,structure and dynamics. Notably, superconducting
gravimeters allow continuous monitoring of the gravity
signal at selected sites with a precision of better than 10-10.
These geophysical observations together with other
geodetic observations and geological information provide
the means to better understand the structure, dynamics andevolution of the Earth system. Nowadays, the range of theapplications of superconducting gravimeters (SG) becomesvery wide and applicable not only to Earth tides
investigations, but also to support studies on Earth’s
seismicity or hydrological influences.

1029

The Chair of SC 3.1 is also responsible for close
cooperation with the International Geodynamics and Earth
Tide Service (IGETS) to provide effective service-withscience coupling.
Objectives
Objectives of SC 3.1 include:
x To study and implement new observational techniques
and improve existing ones, including clinometric andextensometric techniques;x To advance tidal data analyses and prediction methods;
x To enhance the models on the interaction among solid
Earth, ocean, and atmospheric tides;
x To research the effects of the atmosphere on gravity andother geodetic observations;x To study the response of the Earth at tidal and non-tidal
forcing frequencies;
x To study the interplay between tides and Earth rotation;
x to study tides on the planets;
x To study the effects of ocean loading and global water
distribution;
x To create and coordinate working groups on specifictopics of interest and relevancy to the understanding ofour planet;x To develop, coordinate and promote international
conferences, programs and workshops on dataacquisition, analysis and interpretation related to theresearch fields mentioned above;x To contribute to the definition and realization of theInternational Terrestrial Reference Frame via advanced
geodynamic models at global, regional and local scales;
x To promote the systematic calibration andintercomparison of absolute and superconducting
gravimeters;x To promote interdisciplinary research in Earth andplanetary tides;
x To support the IAG Global Geodetic Observing System(GGOS) in the field of- the integral effect on Earth rotation of all angularmomentum exchange inside the Earth, between land,
ice, hydrosphere and atmosphere, and between the
Earth, Sun, Moon, and planets,- the geometric shape of the Earth’s surface (solid
Earth, ice and oceans), globally or regionally, and its
temporal variations, whether they are horizontal orvertical, secular, periodical or sudden,- the Earth’s gravity field-stationary and time variablemass balance, fluxes and circulation.

1030

Program of Activities
SC 3.1 National representatives are involved in:x Organization of International Symposium on
Geodynamics and Earth Tide (GET Symposium held
every four years) as well as other thematic conferences
together with other Commission 3 SCs if possible;x Awarding of the outstanding scientists with the Paul
Melchior Medal, formerly known as the Earth Tides
Commission Medal;x Organization of special sessions at international
meetings;
x Organization of the comprehensive SC meeting together
with the IGETS;
x Publishing the outcome of the researches, either asstand-alone publications or as proceedings or special
issues of scientific journals;
x Cooperating with other Joint Study Groups (JSG), Joint
Working Groups (JWG) or Inter-Commission Projects(ICP) and Committees (ICC);x Cooperate with GGOS, as mentioned above.

Structures for the Period 2015-2019

Commission 3 – Earth Rotation and Geodynamics

SC 3.2: Crustal Deformation
Chair: Zheng-Kang Shen (China)
Vice-Chair: Paramesh Banerjee (Singapore)
Terms of Reference
There are many geodetic signals that can be observed andare representative of the deformation mechanisms of the
Earth's crust at different spatial and temporal scales. This
includes the entire range of tectonic phenomena including
plate tectonics, intraplate deformation, the earthquake
deformation cycle, aseismic phenomena such as episodic
tremor and slip, and volcanic deformation. The time scales
range from seconds to years and the spatial scales frommillimeters to continental dimension.
A variety of geodetic technologies such as GNSS,InSAR, LiDAR, terrestrial LiDAR, tiltmeter, andstrainmeter now provides the means to observe
deformation and movements of the Earth's crust at global,
regional, and local scales. This is a considerable
contribution to global geodynamics by supplying primaryconstraints for modeling the planet as a whole, but also forunderstanding geophysical phenomena occurring at local
scales. Some phenomena are potentially hazardous, likeearthquake and volcanic activity related phenomena. On
the other hand, there are many slow deformations which
are not hazardous, but in long time scales may haveconsiderable effects. These include steady tectonic
deformations and postglacial rebound. Other non-tectonic
deformations which may have significant societal impacts
include landslide, ground subsidence, sinkhole, and theones related to surficial and underground fluid circulations.
One of the key issues nowadays is the definition andstability of global and regional reference frames. Crustal
deformations in all time and spatial scales as well as masstransfer will affect reference frames. Gravimetry, absolute,
relative, and nowadays also spaceborne, is a powerful tool
providing information to the global terrestrial gravity field
and its temporal variations, and helping define global andregional reference frames. Integration of variety ofgeodetic observations and data from other geophysical andgeological sources provides the means to understand thestructure, dynamics and evolution of the Earth system.
Organizational Aspects
There is a natural relationship with IAG Commission 1, as
the reference frame definition must be consistent with theactual crustal deformation. The work of the SubCommission will be organized as working-group like. A
core group of people will be invited to meet regularly and1031

try to evaluate different models or approaches forcomputing or evaluating these effects. Due to global
distribution of participants, electronic meetings and e-mails
will be an essential part of communication for theorganization. The Sub-Commission aims to organize 1-2
topical symposia during the 4-year period.
Objectives
General objectives of the Sub-Commission 3.2 will
include:x To study crustal deformation in all scales, from plate
tectonics to local deformation;
x To contribute reference frame related work in order tobetter understand deformations, and to improve global,
regional and local reference frames and their dynamical
modeling;
x To study sea-level fluctuations and changes in relation
to vertical tectonics along many parts of the coastlines
and in relation to environmental fluctuations/changes
affecting the geodetic observations;x To study deformation during the seismic cycle including
earthquakes, episodic slow slip events, and postseismictransients, in relation to physical processes of fault
zones, crust and mantle rheology, and seismic hazards;
x To characterize strain partitioning in fault systems withreference to block or continuum mechanics;
x To monitor and study volcanic, fluid circulation related,
and anthropologic deformations;x To monitor and study natural hazard related
deformations such as landslide, ground subsidence, andsinkhole, etc.;
x To promote, develop, and coordinate international
programs related to observations, analysis and datainterpretation for the fields of investigation mentioned
above;x To promote free data sharing/exchange andcollaborations within the community;
x To organize and co-organize meetings and symposia
related to the topic.

Structures for the Period 2015-20191032

SC 3.3: Earth Rotation and Geophysical Fluids

Program of Activities

Chair: Jianli Chen (USA)Vice-Chair: Michael Schindelegger (Austria)

SC 3.3 follows the program of activities defined by Commission 3. In order to promote the exchange of ideas andresults as well as of analysis and modeling strategies,
sessions at international conferences and topical
workshops will be organized. In addition, SC 3.3 interacts
with the sister organizations and services, particularly with
the IERS Global Geophysical Fluids Centre and its
operational component with four Special Bureaus(atmosphere, hydrology, ocean, combination) and its nonoperational component for core, mantle, and tides. SC 3.3
will have close contacts to the GGOS activities, inparticular to the activities of the newly established GGOS
Working Group ‘Contributions to Earth System
Modelling’.

Terms of Reference
Mass transport in the atmosphere-hydrosphere-mantle-coresystem, or the 'global geophysical fluids', causes
observable geodynamic effects on broad time scales.
Although relatively small, these global geodynamic effects
have been measured by space geodetic techniques toincreasing, unprecedented accuracy, opening up important
new avenues of research that will lead to a better
understanding of global mass transport processes and of
the Earth’s dynamic response. Angular momenta and therelated torques, gravitational field coefficients, andgeocenter shifts for all geophysical fluids are the relevant
quantities. They are observed using global-scalemeasurements and are studied theoretically as well as byapplying state-of-the-art models; some of these models are
already con-strained by such geodetic measurements.
Objectives
The objective of the SC is to serve the scientificcommunity by supporting research and data analysis inareas related to variations in Earth rotation, gravitational
field and geocenter, caused by mass re-distribution within
and mass exchange among the Earth’s fluid sub-systems,
i.e., the atmosphere, ocean, continental hydrosphere,
cryosphere, mantle, and core along with geophysicalprocesses associated with ocean tides and the hydrologicalcycle.
The SC complements and promotes the objectives of
GGOS with its central theme "Global deformation andmass exchange processes in the Earth system" and thefollowing areas of activities:
x quantification of angular momentum exchange and masstransfer;x deformation due to mass transfer between solid Earth,atmosphere, and hydrosphere including ice.

Commission 3 – Earth Rotation and Geodynamics

1033

SC 3.4: Cryospheric Deformation

Program of Activities

Chair: Shfaqat Abbas Khan (Denmark)Vice-Chair: Matt King (Australia)

x Organize a workshop to discuss separation of elastic and
GIA signals in key regions of interest, including
Greenland, Antarctica, Patagonia and Alaska. Include
WG 2.6.3 “Glacial isostatic adjustment (GIA) Modeland Effects” and SC 1.2 “Global Reference Frames” onglobal reference frames for validation of GIA models.
x Establish and publish a list of PSMSL tide gauges thatare subject to large, time-variable elastic deformation
associated with present-day glacier mass change.
x Compile a database of predictions for relative sea levelchanges at tide gauges, gravity field, and 3D
deformation rates at geodetic sites and on global orregional grids for a set of reasonable GIA models, bothfor the deglaciation after LGM and more recent icechanges. While this database may not lead to consensus
about the “best” model, it will clarify the range ofpredictions made by models that have some support
within the broader community.
x Interact where possible with those working on
alternative measurements of the same signals(gravimetric or Earth rotation).
x Organize a workshop on “Present-day changes in themass balance of Earth's glaciers and ice sheets”.

Terms of Reference
Past and present changes in the mass balance of the Earth's
glaciers and ice complexes induce present-day deformationof the solid Earth on a range of spatial scales, from thevery local to global. Of principal interest are geodetic
observations that validate, or may be assimilated into,models of glacial isostatic adjustment (GIA) and/or
constrain models of changes in present-day ice masses
through measurements of elastic rebound. Using geometricmeasurements alone, elastic and GIA deformations cannot
be separated without additional models or observations.
Reference frames of GIA models do not allow directcomparison to measurements in an International Terrestrial
Reference Frame and ambiguity currently exists over theexact transformation between the two. Furthermore, there
is no publicly available and easy-to-use tool for modelcomputations of elastic effects based on observed
elevation/mass changes over the spatial scales of interest(small valley glaciers to large ice streams) and including
gravitational/rotational feedbacks. This SC will focus on
resolving these technical issues and work on disseminationof these measurements within the glaciological community(notably IACS).

Structures for the Period 2015-20191034

SC 3.5: Tectonics and Earthquake Geodesy
Chair: Haluk Ozener (Turkey)
Terms of Reference
Space and terrestrial geodesy provide key observations toinvestigate a broad range of the Earth’s systems. These
data are collected, analyzed, and interpreted by geodesists
and other scientists. Studies of crustal deformation rely on
the continuous and/or repeated acquisition of geodetic
measurements and their analysis in the frame of active
tectonics, and on their combination with results obtained
from other geological and geophysical investigations(seismology, neotectonics, gravity, rock physics,
electromagnetic, ...).
The evolution of geodetic techniques in the past decade,with unprecedented achievements in the precise detection
and monitoring of 3D movements at the millimeter levelhas opened new prospects for the study of Earth kinematics
and geodynamics. However, these achievements also raise
new issues that have to be properly taken into account in
the processing and analysis of the data, demanding a
careful inter-disciplinary approach.
Areas that involve the broad collision zone between
Europe, Africa and Arabia, provide natural laboratories tostudy crucial and poorly understood geodynamic
processes. The recent occurrence of giant earthquakes(with Mw > 9), unexpected and in subduction areas withweak geodetic monitoring provides further challenges tothe scientific community. Although these active zones
were systematically monitored in the last decade bydifferent institutions and research groups using a variety ofspace geodesy and other methods, in general the data
analysis and interpretation have been done from theperspective of one discipline and have rarely followed an
integrated approach. Never completely explored, theexistence of these data (geodata) justifies a new, integrated
approach including different observational techniques andinput from other disciplines in the Earth sciences (geology,
seismology, tectonics ...). This should lead to thedevelopment of interdisciplinary work in the integration of
space and terrestrial approaches for the study of, forinstance, the Eurasian/African/Arabian plate boundary
deformation zone (and adjacent areas), and contribute to
the establishment of a European Velocity Field. With thisobjective, it is important to promote stronger international
cooperation between Earth scientists interested in plateboundary zones.

Towards this goal the SC aims:
x To actively encourage the cooperation between all geoscientists studying the Eurasian/African/Arabian plateboundary deformation zone, by promoting the
exploitation of synergies;
x To reinforce the study of subduction zones inMediterranean regions and elsewhere by increasing anddeveloping infrastructures and geodetic stations;x To be a reference group for the integration of the mostadvanced geodetic and geophysical techniques bydeveloping consistent methodologies for data reduction,
analysis, integration, and interpretation;
x To act as a forum for discussion and scientific support
for international geoscientists investigating thekinematics and mechanics of the Eurasian/African/
Arabian plate boundary deformation zone;
x To promote the use of standard procedures for geodetic
data acquisition, quality evaluation, and processing,particularly GNSS data;x To promote earthquake geodesy and the study ofseismically active regions with large earthquake
potential;
x To promote the role of Geodesy in tectonic studies forunderstanding the seismic cycle, transient andinstantaneous deformation, and creeping versus seismic
slip on faults.
Objectives
The primary goals of the SC are:
 To continue as a framework for geodetic cooperation in
the study of the Eurasian/African/Arabian plateboundary zone;
 To identify and characterize a potential “Wegener
Supersite”;
 To develop scientific programmes in earthquake geodesy forsubduction zones (e.g., Hellenic Arc) and possible
occurrence of giant earthquakes and associated tsunamis;
 To foster the use of space-borne, airborne and hybrid
techniques as high-resolution GNSS, InSAR, GOCE,
GRACE, ENVISAT, SENTINELLE, LIDAR, etc. forearth observation;
 To define effective integrated observational strategies
for these techniques to reliably identify and monitor
crustal movements and gravity variations over all timescales; To facilitate and stimulate the integrated exploitation ofdata from different techniques in the analysis andinterpretation of geo-processes;
 To organize periodic workshops and meetings withspecial emphasis on interdisciplinary research andinterpretation and modeling issues;

Commission 3 – Earth Rotation and Geodynamics

 To reinforce cooperation with African and Arabcountries and colleagues with scientific projects, thatcan contribute to understanding the kinematics anddynamics of the Eurasian/African/Arabian plateboundary zone and promote the growth of such researchand geodetic expertise in these countries.
Program of Activities
 Build a web-portal and an associated geo-database thatenables access to metadata, processed results, and whenpossible historical data from continuous GNSS stations
and episodic geodetic campaigns, as well as otherderived products such as strain rates, velocity fields,etc.; Promote the application of standards for GNSS network
establishment, data acquisition, and guidelines for dataprocessing and reliability checks;
 Define strategies for a full exploitation of different geodata (GNSS, gravimetry, InSAR, etc.);
 In coordination with the IGS and other relevantorganizations, establish a GNSS analysis centre
specially dedicated to process permanent and episodic
campaign data, not analyzed by other GNSS centres,
which will contribute to the development of a joint
velocity field (EUROVEL) that can support kinematicand geodynamic modeling; Organize bi-annual conferences to serve as high-levelinternational forums in which scientists from all over
the world can look at a multi-disciplinary interpretationof geodynamics, and strengthen the collaboration
between countries in the greater Mediterranean region.

1035

Links to Services
The SC will establish links to relevant services and other
IAG (sub-) components, such as: International Earth Rotation and Reference Systems
Service (IERS);
 International GNSS Service (IGS);
 International Laser Ranging Service (ILRS); International VLBI Service for Geodesy and Astrometry(IVS);
 International DORIS Service (IDS); Global Geodetic Observing System (GGOS); African Reference Frame (AFREF);
 Asia-Pacific Reference Frame (APREF);
 European Reference Frame (EUREF):
 North American Reference Frame (NAREF);
 South-Central American Reference Frame (SIRGAS).

Structures for the Period 2015-2019

1036

Joint Study Groups of Commission 3
JSG 3.1: Intercomparison of Gravity and Height
Changes(joint with IGFS, Commissions 1 and 2)
Chair: Séverine Rosat (France)
Terms of Reference
Surface deformations are continuously recorded fromspace and from the ground with increasing accuracy.
Vertical displacements and time-varying gravity are
representative of various deformation mechanisms of the
Earth occurring at different spatial and temporal scales. We
can quote for instance post-glacial rebound, tidal
deformation, surficial loading, co- and post- seismic
deformation and volcanic deformation. The involved
temporal scales range from seconds to years and the spatial
scales range from millimeters to continental dimension.
Large-scale deformation are well monitored by space
geodetic measurements from monthly spatially-averaged
GRACE measurements while local deformation are
precisely monitored by daily GNSS solutions and sub-daily
gravimetric data at a site. The intercomparison of thespace- and ground-gravity measurements with verticalsurface displacements enables us to better understand thestructure, dynamics and evolution of the Earth system.
Thanks to ever-improving measurements techniques andcomputation methods, reaching a millimeter or even a submillimeter level precision has become the new challenge ofthe geodetic community. A method has been proposed touse time-varying ground gravity recorded bysuperconducting gravimeter (SG) at co-located sites withgeometrical space technique (like VLBI, LLR, SLR or
GNSS) to determine more precisely the local deformation.
Several issues arise when comparing geometric andgravimetric measurements of surface deformations.
Among these issues we can quote differences in spatial andtemporal scales, differences in sensitivity and noisecharacteristics as well as some variability in the terrestrialreference frame realization. As a consequence, this Study
Group is joined between Commission 1 on Reference
Frames, Commission 2 on Gravity Field and Commission
3 on Earth Rotation and Geodynamics.
Objectives
The motivation of this Joint Study Group (JSG) is to study
surface deformation by comparing site displacement
observations with both ground- and space-based gravity
measurements. In particular, we will focus on the transfer

function of the Earth at various time-scales related to theelastic and visco-elastic properties of the Earth. This JSG
will hence theoretically study the gravity-to-height changes
ratio in order to discriminate vertical motion from masstransfer. The influence of topography, rheology and lateralheterogeneities of the Earth makes the comparison ofgravity and height changes more difficult to interpret interms of Earth’s structure and properties. So this JSG will
provide solutions helping to understand such effects.
Another objective will be to propose some examples ofcomparison of gravity and height changes using GNSS andSuperconducting Gravimeter observatory data, for instanceto estimate the geocenter motion and mass changes. Such
activity will rely on the IGETS (International
Geodynamics and Earth Tides Service) products (serviceof the IAG and of IGFS) for ground gravity data.
Program of Activities
 Study of the noise characteristics of GNSS heightchange and Superconducting Gravimeter gravity change
measurements.
 Love numbers determination using co-located gravity
and displacement measurements.
 Review of the gravity-to-height ratio at various time andlength scales.
 Theoretical and numerical computation of the influenceof rheology and lateral structure of the Earth on thegravity-to-height ratio.
 Estimate of the geocenter motion by combining GNSS
and gravity measurements.
 Organization of an international workshop in 2017 in
Strasbourg (France).
 Contribution to international meetings and conferences.
 Common publications by JSG members.
Members
Séverine Rosat (France), Chair
José Arnoso (Spain)
Valentina Barletta (Denmark)Janusz Bogusz (Poland)
Andrea Bordoni (Denmark)
Yoichi Fukuda (Japan)
Anthony Mémin (France)
Laurent Métivier (France)
Yves Rogister (France)
Holger Steffen (Sweden)
Corresponding member
Giorgio Spada (Italy)

Commission 3 – Earth Rotation and Geodynamics

Joint Working Groups of Commission 3
JWG 3.1 Theory of Earth Rotation and Validation(joint with IAU)
Chair: José Ferrándiz (Spain)ViceǦChair: Richard Gross (USA)PurposeTo promote the development of theories of Earth rotationthat are fully consistent and that agree with observations
and provide predictions of the Earth orientation parameters(EOPs) with the accuracy required to meet the needs of thenear future as recommended by, e.g., GGOS, the Global
Geodetic Observing System of the IAG.
Justification
Recent efforts have not led to improvements in theaccuracy of theoretical models of the Earth’s rotation thatapproach the required millimeter level, so there is a strong
need to develop such theories to meet the current andfuture accuracy of the observations and trying to improvepredictions.
Terms of Reference
A main objective of the Working Group (WG) is to assessand ensure the level of consistency of EOP predictions
derived from theories with the corresponding EOPs
determined from analyses of the observational data
provided by the various geodetic techniques. Consistency
must be understood in its broader meaning, referring tomodels, processing standards, conventions etc. This JWG
will closely collaborate with GGOS.
Clearer definitions of polar motion and nutation areneeded for both their separation in observational data
analysis and for use in theoretical modeling.
Theoretical approaches must be consistent with IAU
and IAG Resolutions concerning reference systems, frames
and time scales.
Searching for potential sources of systematic differences
between theory and observations is encouraged, including
potential effects of differences in reference frame
realization.
The derivation of comprehensive theories accounting
for all relevant astronomical and geophysical effects andable to predict all EOPs is sought. In case more than one
theory is needed to accomplish this, their consistency
should be ensured.

1037

There are no a priori preferred approaches or methodsof solution, although solutions must be suitable for
operational use and the simplicity of their adaptation to
future improvements or changes in background models
should be considered.
The incorporation into current models of corrections
stemming from newly studied effects or improvements ofexisting models may be recommended by the JWG when
they lead to significant accuracy enhancements, validatedby comparisons with determined EOP.
Desired Outcomesx ContributetoimprovingtheaccuracyofprecessionǦnutation and Earth rotation parameters(ERP) theoretical models by proposing both newmodels and additional corrections to existing ones;x Clarify the issue of consistency among conventional
EOPs, their definitions in various theoretical
approaches, and their practical determination;
x Establish guidelines or requirements for future
theoretical developments with improved accuracy.
We are aware that subject is too broad for a single
Working Group, and also that the existence of independent
Sub-WGs for different subǦfields implies a risk that theirresults will not be consistent with each other. Thus, weestablish the following three Sub-WGs.
The subjects of SWG 1 and 2 are self-explanatory.
SWG 3 will be dedicated to numerical theories andsolutions, relativity and new concepts and validation bycomparisons among theories and observational series.
1. Precession/Nutation
Chair: Juan Getino (Spain)
Vice-Chair: Alberto Escapa (Spain)
Members
Yuri Barkin (Russia),
Véronique Dehant (Belgium),
Cheng-Li Huang (China), Jan Vondrak (Czech Republic)
Correspondents
Nicole Capitaine (France), Steven Dickman (USA),
Marta Folgueira (Spain), Alexander Gusev (Russia),
Tom Herring (USA),
George Kaplan (USA),
Jürgen Mueller (Germany), Harald Schuh (Germany),
Jean Souchay (France),
Sean Urban (USA),
Vladimir Zharov (Russia).

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1038

2. Polar Motion and UT1

JWG 3.2 Constraining vertical land motion of tide gauges(joint with IAG Comm. 1)

Chair: Aleksander Brzezinski (Poland)
Chair: Alvaro Santamaría-Gómez (France)
Members
Terms of reference
Christian Bizouard (France), Benjamin F. Chao (Taipei),
Jolanta Nastula (Poland), David Salstein (USA),
Florian Seitz (Germany).
Correspondents
Wei Chen (China),
Cheng-Li Huang (China),
Wiesław Kosek (Poland), Jim Ray (USA),
Cyril Ron (Czech Republic), Harald Schuh (Germany),
WenBin Shen (China),
Daniela Thaller (Germany),
QiJie Wang (China),
YongHong Zhou (China).
3. Numerical Solutions and Validation
Chair: Robert Heinkelmann (Germany)
Members
Wei Chen (China),
Daniel Gambis (France),
Brian Luzum (USA),
Zinovy Malkin (Russia),
M Schindelegger (Austria).
Correspondents
BF Chao (Taipei),
Véronique Dehant (Belgium),
Enrico Gerlach (Germany), Cheng-Li Huang (China),
Juan F. Navarro (Spain), Maria Eugenia Sansaturio (Spain),
Harald Schuh (Germany), Florian Seitz (Germany),
Maik Thomas (Germany), QiJie Wang (China).

Inter-annual to secular vertical motion of the Earth’s crustat the tide gauge locations has a substantial impact on theassessment of climatic sea-level variations and for thevalidation of satellite altimetry missions.
When a postglacial rebound model is used to correct thesecular vertical motion of the tide gauges, errors in themodel and the omission of other sources of land motion
makes the corrections uncertain. The alternative is using
land motion estimates from geodetic observations.
However, not all the tide gauges are monitored andestimates of vertical land motion from geodetic
observations are severely limited in time, especially when
considering
multi-decadal
tide
gauge
records.
Consideration of non-linear deformation and reference
frame stability is therefore crucial for extrapolating thevertical motion estimates beyond the observed period.
This Working Group will focus on providing contrasted
vertical land motion at tide gauges from a multi-techniqueperspective. Tide gauges commonly used for long-term
sea-level change (e.g., sea-level reconstructions) and forcalibration/validation of satellite altimeters are the main
target.

Program of activities
x Collect and compare different vertical land motion
estimates and constraints at the tide gauges from amulti-approach perspective (geodetic observations andgeophysical models).
x Identify tide gauges with large uncertainty on its verticalmotion.
x Assess the propagation of vertical land motion
uncertainty onto sea-level change.
x Identify InSAR imagery data suitable to determine
relative vertical motion around selected tide gauges.
Members:
Alvaro Santamaría-Gómez (France), Chair
Matt King (Australia)
Tilo Schöne (Germany)
Tonie van Dam (Luxembourg)
Guy Wöppelmann (France)

Commission 4 – Positioning and Applications

1039

Commission 4 – Positioning and Applications
President: Marcelo Santos (Canada)
Vice President: Allison Kealy (Australia)
http://IAG-Comm4.gge.unb.ca

Terms of Reference

Objectives

IAG Commission 4 intends to bring together scientists,
researchers and professionals dealing with the broad areaof positioning and its applications. For this purpose, it will
promote research that leverages current and emerging
positioning techniques and technologies to deliver practicaland theoretical solutions for engineering and mapping
applications, GNSS technologies, sensors fusion, andatmospheric sensing, modelling, and applications, based on
geodetic techniques. Commission 4 will carry out its workin close cooperation with the IAG Services and other IAG
entities, as well as via linkages with relevant entities withinscientific and professional organizations.
Recognizing the central role of Global Navigation
Satellite Systems (GNSS) in providing high accuracy
positioning information today and into the future,
Commission 4 will focus on research for improving
models and methods that enhance and assure thepositioning performance of GNSS-based positioning
solutions for a range of geodetic applications.
The Sub-Commissions will develop theory, strategies
and tools for modeling and/or mitigating the effects ofinterference, signal loss and atmospheric effects as they
apply to precise GNSS positioning technology. They willaddress the technical and institutional issues necessary fordeveloping backups for GNSS, integrated positioning
solutions, automated processing capabilities and quality
control measures.
Commission 4 will also deal with geodetic remotesensing, using Synthetic Aperture Radar (SAR), Light
Detection and Ranging (LiDAR) and Satellite Altimetry(SA) systems for geodetic applications.
Additional WGs and SGs can be established at any time,and existing can be dissolved, if they are inactive.

The main topics dealt by Commission 4 are as listed in the
IAG By-laws:x Terrestrial and satellite-based positioning systems
development, including sensor and information fusion;x Navigation and guidance of platforms;
x Interferometric laser and radar applications (e.g.,Synthetic Aperture Radar);x Applications of geodetic positioning using three
dimensional geodetic networks (passive and active
networks), including monitoring of deformations;x Applications of geodesy to engineering;x Atmospheric investigations using space geodetic
techniques.

Structure
Sub-Commissions
SC 4.1: Emerging Positioning Technologies and GNSS
Augmentation
Chair: Vassilis Gikas (Greece)
SC 4.2: Geo-spatial Mapping and Geodetic Engineering
Chair: Jinling Wang (Australia)
SC 4.3: Atmosphere Remote Sensing
Chair: Michael Schmidt (Germany)
SC 4.4: Multi-constellation GNSS
Chair: Pawel Wielgosz (Poland)

1040

Joint Study Groups
JSG 0.10: High rate GNSS
Chair: Mattia Crespi (Italy)(joint with ICCT, description see ICCT)JSG 0.14: Fusion of multi-technique geodetic data
Chair: Krzysztof Sośnica (Poland)(joint with ICCT, description see ICCT)JSG 0.17: Multi-GNSS theory and algorithms
Chair: Amir Khodabandeh (Australia).
(joint with ICCT, description see ICCT)JSG 0.20: Space weather and ionosphere
Chair: Klaus Börger (Germany)(joint with ICCT, description see ICCT)
Joint Working Groups
JWG 1.3: Troposphere Ties
Chair: Robert Heinkelmann (Germany)
Vice-Chair: Jan Douša (Czech Republic)(joint with Commission 1, description see
Commission 1)

Steering Committee
President Commission 4: Marcelo Santos (Canada)
Vice-President Comm. 4: Allison Kealy (Australia)
Chair Sub-Comm. 4.1: Vassilis Gikas (Greece)
Chair Sub-Comm. 4.2: Jinling Wang (Australia)
Chair Sub-Comm. 4.3: Michael Schmidt (Germany)
Chair Sub-Comm. 4.4: Pawel Wielgosz (Poland)
Representative of IVS: Robert Heinkelmann (Germany)
Member-at-Large:
Jens Wickert (Germany)
Member-at-Large:João F. Galera Monico (Brazil)

Representative of External Bodies
ISPRS: Charles Toth (USA)
FIG:
Allison Kealy (Australia)
ION: Larry Hothem (USA)UN International Committee on GNSS: Ruth Neilan (USA)

Structures for the Period 2015-2019

Commission 4 – Positioning and Applications

Sub-Commissions
SC 4.1: Emerging positioning technologies
and GNSS augmentation
Chair: Vassilis Gikas (Greece)
Vice-chair: Günther Retscher (Austria)
Secretary: Harris Perakis (Greece)
Terms of Reference
To undertake, promote and report on research thatleverages
emerging
positioning
techniques
andtechnologies aiming to address practical and theoreticalsolutions for positioning, navigation and guidance,
including spatio-temporal monitoring and tracking ofobjects at various scales. The focus will be on multisensor cooperative systems operating in adverse GNSS
conditions for transportation, personal mobility, industrial
and indoor positioning applications and to a lesser extent
environmental monitoring. Except GNSS, the primarysensors of interest include inertial and wirelesstechnologies as well as vision-based systems and laser
scanning. SC 4.1 will foster linkages and pursue its goals
in close collaboration with other IAG Entities, as well assister scientific and professional organizations, primarily
the ISPRS, FIG, ION and IEEE.
Objectives
x To address and evaluate new algorithms and multisensor systems for cooperative and ubiquitous
positioning for land and airborne navigation
applications including UAV systems;
x To examine the potential and capabilities of low-cost
sensors including GNSS systems and smartphonenavigation sensors;x To follow the technical advances in wireless systems
such as RFID, UWB, WiFi, LED, DSRC for personal
mobility and road applications;x To evaluate the usability of emerging positioning
technologies for urban traffic navigation and improved
routing using collaborative driving systems andcrowdsourcing traffic information;
x To study vision-based and optical systems including
cameras and laser scanning both for navigation andobject tracking and monitoring purposes;x To contribute in research that depends on big data
handling, sensor synchronization, data fusion, real-timeprocessing as well as to support standardization
activities;

1041

x To study and monitor the progress of new multi-sensor
applications, as well as, to support and promoteknowledge exchange and reporting on the development
trends, possibilities and limitations of emerging
positioning technologies;
x To work closely, promote and present throughpublications and workshops the SC work at IAG eventsand those of sister organizations including the FIG,ISPRS, IEEE, ION, as well as, in collaboration withmore specialized initiatives such as the EU COST
Action SaPPART.

Structures for the Period 2015-2019

1042

Working Groups of Sub-Commission 4.1

WG 4.1.2: Indoor Positioning and Navigation

WG 4.1.1: Multi-Sensor Systems

Chair: Kefei Zhang (Australia)
Vice-Chair: R. Chen (USA)

Chair: Allison Kealy (Australia)
Vice-Chair: Günther Retscher (Austria)
Description
This group is a joint working group between IAG and FIG.
It focuses on the development of shared resources that
extend our understanding of the theory, tools andtechnologies applicable to the development of multi-sensor
systems. It has a major focus on:
x Performance characterization of positioning sensors andtechnologies that can play a role in augmenting core
GNSS capabilities;
x Theoretical and practical evaluation of current
algorithms for measurement integration within multisensor systems;
x The development of new measurement integration
algorithms based around innovative modelingtechniques in other research domains such as machinelearning and genetic algorithms, spatial cognition etc.;
x Establishing links between the outcomes of this WG andother IAG and FIG WGs (across the whole period);
x Generating formal parameters that describe theperformance of current and emerging positioning
technologies that can inform IAG and FIG members.
Specific projects to be undertaken include:
x International field experiments and workshops on a
range of multi sensor systems and technologies;
x Evaluation of UAV capabilities and the increasing roleof multi-sensor systems in UAV navigation;x Investigation of the role of vision based measurements
in improving the navigation performance of multisensor systems;x Development of shared resources to encourage rapid
research and advancements internationally.

Description
The needs for indoor positioning and navigation haveexperienced unprecedented growth in the past decade dueto the proliferation and ubiquitous usages of mobile
devices and the rapid development of Internet of Things.
Location information of people and objects in indoor
environments becomes a key issue for many emerging andinnovative applications. The primary aims of this working
group are:x To investigate emerging sensor technologies (e.g. LED,magnetometers), integrated techniques and protocols forindoor positioning and tracking;x To discuss, investigate and develop new algorithm andsmart solutions;x To bring key researchers and developers in this area
together;x To disseminate effectively the state-of-the-art
knowledge and new discoveries in the geospatial
communities.
Specific projects to be undertaken include:
x Smart tracking based hybrid indoor positioning and GIS
techniques;x Third generation of positioning system for undergroundmine environments;
x Tracking indoor information and people’s behaviour;x Development of intelligent device-finder and locationfinder;x Multi-sensor Navigation with low-cost;x Positioning in 5G cellular communication system.

Commission 4 – Positioning and Applications

WG 4.1.3: 3D Point Cloud Based Spatio-temporal
Monitoring
Chair: Jens-Andre Paffenholz (Germany)
Vice-Chair: Corinna Harmening (Austria)
Description
The WG will focus on spatio-temporal monitoring ofartificial and natural objects with the aid of 3D point
clouds acquired by means of multi-sensor-systems (MSS).
The emphasis will primarily be placed on laser scanningtechnology and to certain extend on digital cameras. In
general, monitoring applications over a certain period oftime require a geo-referencing of the acquired data withrespect to a known datum. Also, a kinematic MSS requires
the determination of the time-dependent seven degrees of
freedom (translation, rotation and scale) with regard to areferencing.
Objectives
x Performance characterization of laser scanners andcameras and their fusion in MSS with respect to spatiotemporal monitoring of artificial and natural objects indifferent scales. Potential objects or scenarios can range
from plant phenotyping to the monitoring of
infrastructure buildings;
x Evaluate the object’s abstraction for epochal
comparison by means of discrete point-wise, area-based
and shape-based approaches. One suitable method toinvestigate will be B-spline surfaces;
x Investigate and develop suitable algorithms for change
tracking over time in 3D point clouds, for instance bymeans of feature point tracking or shape matching;x Evaluate the fusion of heterogeneous data like 3D point
clouds and ground-based synthetic aperture radar (GBSAR) data with respect to structural health monitoring
applications including infrastructure buildings;
x Algorithms will be implemented in Python, Matlab,
C++ whereas for basic 3D point cloud operations open
source libraries should be used, such as point cloudlibrary (PCL);x Establishing links to colleagues from civil andmechanical engineering to benefit from each other interms of structural health monitoring, for instanceloading tests of structural elements in lab and realconditions;x Establishing working links between this working groupand similar national and international working groups
such as DVW, ISPRS, IAG and FIG working groups.

1043

Specific projects to be undertaken include:
x Comparative study of different laser scanners in a plant
phenotyping scenario in a greenhouse environment. The
focus should be on low-cost laser scanners rather thanon high-end triangulation sensors (link to plantscientists);x Loading tests of a concrete structures in laboratoryenvironments (link to civil engineers);
x Simultaneous observations and cross-comparisons using
laser scanner, camera and GB-SAR of suitable objects.

1044

WG 4.1.4: Robust Positioning for Urban Traffic
Chair: Laura Ruotsalainen (Finland)
Vice-Chair: Fabio Dovis (Italy)
Description
The Work Group will focus on the navigation challenges
on the urban environments for greener, safer and more
comfortable traffic. At present, navigation is mainly basedon the use of Global Navigation Satellite Systems (GNSS),
providing good performance in open outdoor
environments. However, navigation solution with
sufficient accuracy and integrity is needed in urban
canyons, where GNSS is significantly degraded or
unavailable. For overcoming the aforementioned
navigation challenges, research has been very active for
decades for finding a suitable set of other methods foraugmenting or replacing the use of GNSS in positioning
for urban traffic.
Objectives
x Specification and characterization of the system
requirements, especially from the environmental andsafety viewpoints;
x Evaluation of the usability of emerging technologies forthe urban traffic navigation, including vision-aiding andcollaborative driving systems;
x Selection of best set of technologies fulfilling thesystem requirements;
x Performance analysis of the selected system both forvehicles and pedestrians in urban areas;x Selecting the most suitable algorithms for map matching
and routing.
Specific projects to be undertaken include reporting on
and/or establishing links between:
x The specification and characterization of the system
requirements;
x recommendations on the best set of sensors andtechnologies to be used;
x The performance analysis of the selected system;
x The most suitable algorithms for map matching androuting in urban environments.
The outcomes of this WG, other IAG and FIG WGs, theEU COST action SaPPART addressing the satellite
positioning performance assessment for road transport, as
well as different actors having interest in urban traffic, e.g.
transport authorities and car manufacturers.

Structures for the Period 2015-2019

Commission 4 – Positioning and Applications

SC 4.2: Geo-spatial mapping and geodeticengineering
Chair: Jinling Wang (Australia)
Vice-Chair: Michael J. Olsen (USA)Secretary: Hsiu-Wen Chang (China-Taipei)
Terms of Reference
Geodesy provides foundations for geospatial mapping andengineering applications. Modern geospatial mapping as amassive point positioning process has been evolving
towards automatic operations, and at the same time, various
engineering areas are increasingly relying on highly
developed geospatial technologies to deliver improved
productivities and safety with minimised negativeenvironment impact. This Sub-Commission (SC) 4.2 will
therefore endeavour to coordinate research and otheractivities that address the broad areas of the theory andapplications of geodesy tools in geospatial mapping andengineering, ranging from construction work, geotechnicaland structural health monitoring, mining, to natural
phenomena such as landslides and ground subsidence. The
SC4.2 will carry out its work in close cooperation withother IAG Entities, as well as via linkages with relevantscientific and professional organizations such as ISPRS,
FIG, ISM, ICA, IEEE, ION, OGC.

1045

Objectives
x To develop and promote the use of new geospatial
mobile mapping technologies for various applications;x To develop and report the modelling and quality control
framework for geo-referencing procedures;x To monitor research and development into newtechnologies that are applicable to the general field ofengineering geodesy, including hardware, software andanalysis techniques;x To study advances in geodetic methods for engineering
applications, such as mining operations, and large
construction sites;x To study advances in monitoring and alert systems for
local geodynamic processes, such as landslides, groundsubsidence, etc.;
x To study advances in Structural Health Monitoring(SHM) systems and geospatial mapping applications in
SHM;
x To study advances in Building Information Modelling(BIM) and geospatial mapping applications in BIM;
x To document the body of knowledge in the field ofgeospatial mapping and engineering geodesy, and topresent such knowledge in a consistent frame work at
symposia and workshops;
x To promote research into several new technology areas
or applications through the SC4.2 Working Groups.

Structures for the Period 2015-2019

1046

Working Groups of Sub-Commission 4.2
WG 4.2.1: Mobile Mapping Technologies andApplications
Chair: J. Skaloud (Switzerland)
Vice-Chair: K.-W. Chiang (China-Taipei)
Description
Mobile mapping technologies have been widely used tocollect geospatial data for a variety of applications, forexample, navigation and online geospatial information
services. As mobile mapping sensors are becoming
cheaper and easier to access, modeling and quality control
procedures for major steps of mobile mapping should befurther developed to ensure the reliability of geospatial
data from mobile mapping systems. This working groupwill conduct its work through coordinated activities among
the members of the group as well as in collaborations withother professional organizations, such as ISPRS/FIG.
Objectives
x To monitor new trends in mobile mapping technologies,
such as UAV/UAS mapping;x To evaluate the performance of geo-referencing andmapping sensors, such as IMU, GNSS, 3D cameras,
optical vision sensors;x To develop realistic mathematical and functionalmodels for geo-referencing procedures;x To develop a framework to evaluate the quality of georeferencing and mapping results;
x To promote the use of geospatial mapping systems forvarious applications.

WG 4.2.2: Applications of Geodesy in Mining
Engineering
Chair: Jian Wang (China)
Vice-Chair: Frederick Cawood (South Africa)
Description
Geodesy has been playing an important role in mining
operations from geospatial mapping, modern navigationand guidance technologies used in automation at various
mine sites to special orientation and location procedures
used in underground operations. This working group willconduct its activities in close collaborations with otherrelevant international professional organizations, such as
the International Society of Mining Surveying (ISM) andFIG.
Objectives
Major objectives of this WG are to study, and report theuse of:x Modern geodesy in various mining sites;
x 3D mapping for mining;x Positioning, navigation and guidance of mining
machinery;x Miner location technologies in underground mining
operations;x Mine CORS and its synergized hazard monitoring (e.g.
deformation, landslides and ground subsidence).

Commission 4 – Positioning and Applications

WG 4.2.3: Mobile Structural Health Monitoring
Systems
Chair: Christian Eschmann (Germany)
Vice-Chair: Johnson Shen (Australia)

1047

WG 4.2.4: Building Information Modelling (BIM)
Chair: Mohsen Lalantari (Australia)
Vice-Chair: Michael J. Olsen (USA)
Description

Description
Structural health monitoring (SHM) is an issue ofincreasing importance when looking at more and moreaging and critical infrastructure around the world. In orderto perform safety-related infrastructure inspections, robotic
solutions are required to allow an automatic and reliablegeospatial data acquisition for a comprehensive building
database suitable for SHM analysis. Here the investigationof new mapping and navigation methods as well as nondestructive testing (NDT) sensors forms the basis for thesemobile SHM systems. To develop such reliable
autonomous systems, this working group will focus on
current challenges such as the reproducibility andtraceability of mobile NDT sensor data as well as theprecise localization and navigation operations inside and/orin the areas close to infrastructures.

Developed and promoted by Architecture, Engineering andConstruction (AEC) industry, Building Information
Models (BIM) provides the most detailed 3D spatial andsemantic information about every building element during
the lifecycle of a building. BIM is a 3D digital data spacefor sharing building information to enable multidisciplinary collaboration among different actors involvedin the development process of buildings. Recent surveys
indicate that the BIM-based paradigm brings moreproductivity gains and long-term benefits. Therefore, thisworking group aims to promote BIM in IAG andencourage and report innovation in integrating BIM withgeospatial engineering. This working group will conduct
its activities in close collaborations with other relevantinternational professional organizations, such as GSDI,ISPRS and FIG.

Objectives

Objectives

x To monitor new approaches in terms of mobile
structural health monitoring;x To promote the use of unmanned mobile platforms,
such as RPAs, UGVs and ROVs, for remote inspection
and monitoring applications;x To develop new methods for autonomous precise
geospatial data acquisition and inspection tasks;
x To evaluate the applicability of miniaturized navigationand non-destructive testing sensors, such as LiDAR,
radar or ultrasound, in mobile SHM systems.

x Promote BIM and raise awareness in geospatial
engineering applications;x Integrate 3D mapping technologies and BIM;
x Investigate interoperability between and othergeospatial formats;x Use BIM in indoor navigation, indoor positioning, and3D cadasters

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1048

SC 4.3: Atmosphere remote sensing
Chair: Michael Schmidt (Germany)
Vice-Chair: Jaroslaw Bosy (Poland)
Secretary: Mahmut O. Karslioglu (Turkey)
Terms of Reference
The Earth’s atmosphere can be structured into various
layers depending on physical parameters such astemperature or charge state. From the geodetic point ofview the atmosphere is nowadays not only seen as a
disturbing quantity which has to be corrected but also as atarget quantity, since almost all geodetic measurement
techniques provide valuable information about theatmospheric state.
Space weather and especially its impacts and risks are
gaining more and more importance in politics and sciences,since our modern society is highly depending on spaceborne techniques, e.g., for communication, navigation andpositioning. Coupling processes between different
atmospheric layers and inter-relations with climate change
are other contemporary issues.
The general objectives of this SC are to coordinate
research on the one hand side in understanding processes
within and between the different atmospheric layers using
space-geodetic measurements and observations from otherbranches such as astrophysics and on the other hand indeveloping new strategies, e.g., for prediction and realtime modelling.
Since GNSS is characterized as a highly precise
observation technique it covers a wide range ofapplications and allows for a huge number of research
topics. Besides GNSS based atmosphere sounding andstudying space weather effects by modern evaluation
methods, the promising GNSS reflectometry technique(GNSS-R) is another innovative research topic within thisSub-Commission.
Objectives
x Bridging the gaps between modern geodetic observation
techniques such as GNSS radio occultations or GNSS-R
and measurements from other scientific branches suchas astrophysics and geophysics with the geodetic
community;
x Exploration of the synergies between geodesy and otherscientific branches such as astrophysics and geophysics;
x Improvement of the understanding of space weather
with respect to the whole cause and effect chain;x Investigation of the impact of solar events such as
CMEs and solar flares on technical systems and satellite
observation techniques;x Investigation of ionosphere phenomena such as currents
or scintillations;x Investigation of coupling processes between different
atmospheric layers;
x Estimation of thermosphere target parameters andstudying their influences on satellite missions;x Support of atmosphere prediction models based on the
combination ofdata from different observation
techniques, e.g., by developing sophisticated estimation
procedures;x Improvement of precise positioning and navigation on
the basis of new atmosphere models;x Development of real- and near real-time techniques foratmosphere monitoring;x Study of climatological variations of the atmosphere.
Program of activities
x To promote research collaboration among groups fromgeodesy and other disciplines worldwide dealing withatmosphere research and applications;x To organize and/or participate in scientific andprofessional meetings (workshops, conference sessions,etc.);x To maintain a web page concatenating the SubCommission activities and reports;
x To encourage special issues, e.g. of Journal of Geodesy,on research, applications, and activities related to the
topics of this Sub-Commission.

Commission 4 – Positioning and Applications

Study Groups of Sub-Commission 4.3
SG 4.3.1: Ionospheric and Atmospheric Coupling
Processes and Phenomena: Modeling and
Measurements
Chair: Lucie Rolland (France)
Vice-Chair: Attila Komjathy (USA)
Description
This SG aims at better understanding the coupling
processes within the Earth’s atmosphere and moregenerally between the solid Earth and its external
envelopes including oceans, neutral atmosphere and theionosphere using the help of geodetic techniques.
Ionospheric disturbances from disruptive phenomena such
as – but not limited to – large earthquakes, volcanic
eruptions, tsunamis, meteorological or geomagnetic storms
are now routinely observed using total electron content(TEC) measurements from GNSS indicating that the
Earth’s internal and external processes are closely coupled.
Objectives
x The development of new detection capabilities (e.g.,multi-GNSS, radar imagery, etc.);
x The characterization and classification of ionosphericsignatures, transients or traveling ionosphericdisturbances (TID), in terms of amplitude, duration,
frequencies, wavelengths, etc., as they relate to thesource of the phenomena (natural or hand-made,telluric, atmospheric or ionospheric, etc.);
x The development of algorithms and methods forquantitative modeling of acoustic-gravity waves andnovel designs of inversion strategies of physicalparameters defining the source;x Further developing data collection techniques alongwith establishing geodetic databases of coupledphenomena using non-geodetic observations (airglow,
infrasound, etc.).

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Structures for the Period 2015-2019

1050

Working Groups of Sub-Commission 4.3

WG 4.3.2: Ionosphere Predictions

WG 4.3.1: Real-time Ionosphere Monitoring

Chair: Mainul Hoque (Germany)

Chair: Alberto Garcia-Rigo (Spain)
Vice-Chair: David Roma Dollase (Spain)

Description

Description
Currently, near real-time or even real-time procedures areunder development to monitor and analyse the state of theionosphere and to predict ionosphere target parameterssuch as the electron density or the vertical total electron
content.
Objectives
x Summary of the current status of real-time Ionosphere
Monitoring;x Comparison of existing RT Ionosphere Monitoring
approaches from different perspectives for a specific
event, such as the recent St. Patrick's Day 2015
Geomagnetic Storm;x Procedure to automatically compare on a daily basis a
subset of real time ionosphere data products providing
the results in a common compatible IONEX format.
Potential validation with external data sources, such as
JASON2;x Open discussion towards new concept(s) on RT
Ionosphere Monitoring (through common mailing list).
x Dissemination activities (publications in international
congresses and in international journals).
This WG aims to work in close scientific collaboration
with IGS RT-WG, URSI and COSPAR IRI, among others.

The general objective of this study group is thedevelopment of ionosphere prediction algorithm/models
based on the dependence of ionospheric characteristics on
solar and magnetic conditions as well as on the region of
the Earth. Ionospheric disturbances can affect technologies
in space and on Earth disrupting satellite and airline
operations, communications networks, navigation systems.
As the world becomes ever more dependent on thesetechnologies, ionospheric disturbances as part of space
weather poses an increasing risk to the economic vitality
and national security. Therefore, having the knowledge ofthe ionospheric state in advance during space weather
events is becoming more and more important.
As part of the working group activities we will arrange
splinter meetings during international conferences (e.g.,
EGU, ION GNSS) depending on the availability ofmembers.
Within the next four years we will focus onx the development of algorithms for estimating andforecasting ionospheric parameters worldwide based ondata from geodetic observation systems, (e.g., GNSS) –the approach may take advantage of the ionospheric
movement from east to west,
x performing first steps by introducing physics-motivatedfunctions into the ionospheric parameters estimation
process with respect to the inclusion of Sun andmagnetic observations,x combining data from different sensors to improve thespatial and temporal resolution and sensitivity taking
advantage of different sounding geometries and latency.

Members
Alberto Garcia-Rigo (Chair, Spain)
David Roma Dollase (Vice-Chair, Spain)
Louikis Agrotis (UK), David Altadill (Spain)
Jens Berdermann (Germany), Nicolas Bergeot (Belgium)
Yannick Béniguel (France), Denise Dettmering (Germany)
Joachim Feltens (Germany), Tim Fuller-Rowell (USA)Ivan A. Galkin (USA), Alberto Garcia-Rigo (Spain)
Tamara Gulyaeva (Russia), Haris Haralambous (Cyprus)
Manuel Hernández-Pajares (Spain)
Attila Komjathy (USA), Andrzej Krankowski (Poland)
Anna Krypiak-Gregorczyk (Poland)
Raul Orús (The Netherlands), David Roma Dosalle (Spain)
Michael Terkildsen (Australia), Li Zishen (China)

Members
Mainul Hoque (Chair, Germany)
Aliaa Abd-Elnasser (Egypt)
Mahdi Alizadeh (Germany)
Claudia Borries (Germany)
Marta Cueto (Spain)
Nada Ellahony (Egypt)
Eren Erdogan (Germany)
Adria Rovira Garcia (Spain)
Abraham Stern (USA)Commission 4 – Positioning and Applications

WG 4.3.3: Combination of Observation Techniquesfor Multi-dimensional Ionosphere
Modelling(joint with GGOS)

1051

Thus, this JWG will provide integrated global and regional
maps of VTEC and peak ionosphere parameters from the
combination of various space geodetic techniques. These
products are interpretable as GGOS products following thestrategy defined at the GGOS days 2015 in Frankfurt.

Chair: Mahdi M. Alizadeh (Germany)
Description
The general objective of this working group is thedevelopment of regional and global ionosphere maps of
VTEC and electron density in 2D, 3D, and 4D; based on
the combination of various observation techniques. Several
observation techniques including space geodetic
techniques allow monitoring and modelling of theionosphere parameters, such as the electron density or thevertical total electron content (VTEC), but each technique
has its specific characteristics which influence the derived
parameters. Combining measurements from different
techniques will provide more homogeneous maps withhigher reliability and improved accuracy.
This JWG will contribute extensively to the aims of
GGOS, which is integrating different geodetic techniques,different models, and different approaches in order toensure a long-term, precise monitoring of the geodetic
observables in agreement with the Integrated Global
Observing Strategy (IGOS).
Objectives
x To investigate new space geodetic techniques suitablefor providing information about the ionosphere, e.g.
GNSS radio occultation aboard the Formosat7/COSMIC-2 mission;,x To focus on the development of appropriate parameter
estimation and assimilation techniques based on the
combination of different observation techniques;x To study the integration of measurements from othersources into the combination procedure, e.g. ionosondedata;
x To further investigate on empirical, mathematical, andphysical weighting schemes, with respect to theweighting of different techniques;x To validate the combined maps through comparison
with raw data from various space geodetic techniques;x To evaluate the global ionosphere maps with global
models such as IRI and NeQuick and the regional maps
with regional ionosphere models such as LPIM and
TWIM model.

Members
Mahdi M. Alizadeh (Germany)
Dieter Bilitza (USA)Janina Boisits (Austria)
Eren Erdogan, Eren (Germany)
Robert Heinkelman (Germany)
Mainul Hoque (Germany)
Jian Kong (China)
Ernest P. Macalalad (Philippines)
Anthony J. Mannucci (USA)David Minkwitz (Germany)
Lung-Chih Tsai (China-Taipei)
Robert Weber (Austria)
Dudy D. Wijaya (Indonesia)
Yibin Yao (China)

Structures for the Period 2015-2019

1052

WG 4.3.4: Ionosphere and Troposphere Impact on
GNSS Positioning

WG 4.3.5: Ionosphere Scintillations

Chair: Tomasz Hadas (Poland)

Chair: Lung-Chih Tsai (China-Taipei)
Vice-Chair: Jens Berdermann (Germany)

Description

Description

Atmosphere effects are still one of the major factors
limiting GNSS precise positioning. One possibility toovercome this limitation is to augment the positioning with
precise external model. The ionosphere information isparticularly important for processing long baselines, single
frequency data and ambiguity resolution. The tropospheremodel can improve the convergence time and height
estimation, particularly in real-time kinematic positioning.
Further research is needed in detailed analysis of theatmosphere impact on GNSS positioning.

Ionospheric scintillation has significant impacts on satellite
radio communication and navigation system performance.
The main effects of scintillation on transionospheric radio
systems are signal loss and phase cycle slips, causing
difficulties in the signal lock of receivers. There is no
doubt that scintillation of satellite radio signals is aconsequence of the existence of random electron density
fluctuations within the ionosphere. There could be
different sources for ionospheric instabilities/irregularities
at different areas and geophysical conditions.

Objectives

Objectives

x Specify the requirements for atmosphere models
supporting GNSS positioning;x Study the potential of NWM to support GNSS
positioning with troposphere information;x Investigate the impact of higher-order ionosphereeffects on GNSS precise positioning;x Final product: Recommendation on atmosphere models
quality for application in GNSS positioning.

x Understanding the climatology of ionosphericscintillations, namely, its variation with latitude, season,
local time, magnetic activity and solar cycle;x Understanding the primary instability sources;
x Forecasting scintillations.

Members
Tomasz Hadas (Chair, Poland)
Simon Banville (Canada)
Mainul Hoque (Germany)
Amir Khodabande (Australia)
Thaleia Nikolaidou (Canada)
Junbo Shi (China)
Toshiaki Tsujii (Japan)
Pavel Vaclavovic (Czech Republic)
Duojie Wenig (China)

Members
Lung-Chih Tsai (Chair, China-Taipei)
Jens Berdermann (Vice-Chair, Germany)
Suvorova Alla (China-Taipei)
Chi-Kuang Chao (China-Taipei)
Kai-Chien Cheng (China-Taipei)
Alexei V. Dmitriev (China-Taipei)
Rui Fernandes (Portugal)
Yoshihiro Kakinami (Japan)
Chinmaya Kumar Nayak (India)
Ernest Macalalad (Philippines)
Charles L. Rino (USA)Michael Schmidt (Germany)
Kuo-Hsin Tseng (China-Taipei)
Sudarsanam Tulasiram (India)

Commission 4 – Positioning and Applications

1053

WG 4.3.6: Troposphere Tomography

Members

Chair: Witold Rohm (Poland)

Witold Rohm (Chair, Poland)
Hugues Brenot (Belgium)
Michael Bender (Germany)
Michal Kacmarik (Czech Republic)
Toby Manning (Australia)
Alain Gaiger (Switzerland)
Zhizhao (George) Liu (Hong Kong, China)
Zohre Adavi (Iran)
Laurent Morel (France)
Gregor Moeller (Austria)
Krzysztof Kroszczynski (Poland)Cédric Champollion (France)
Yan Xin (Austria)
Andre Sa (Portugal)

Description
GNSS troposphere tomography technique is gradually
gaining interest around the world as new researchers start
to investigate this concept, with new implementations
being announced quite frequently. In the coming years wewill see dramatic increase of number of available
observations from dense GNSS networks and new satellite
constellations such as Galileo, Beidou, QZSS or IRSS. As
the slant troposphere delay estimation strategies are being
intensively reinvestigated, the number and quality ofstandard tomography observations will be tripled or
quadrupled.
This poses an opportunity for tomography application in
the field of meteorology for monitoring, nowcasting andforecasting. The tomography models could be applied toindependently resolve vertical and horizontal structure ofweather phenomenon, if this could be done with hightemporal resolution it would be an important input for
nowcasting systems. On the other hand a number of STDs
might overload the assimilation systems and theassimilation algorithms might not be optimal for exploiting
the information provided by slants. An intermediate
tomography step might solve these problems. However,successful implementation of tomography models in theweather services is hampered by several factors, such as(1) the unknown retrieval accuracy, (2) an unstable
solution that may vary from epoch to epoch, and (3) a low
vertical and horizontal resolution.
Objectives
x Quality assurance factors in GNSS tomography
processing, investigating new mapping techniques,operator monitoring schemes and use (in the early stage)
synthetic observations,x Optimal combination of GNSS observations with other
troposphere measurements in GNSS tomographymodels, [COMBINATION]
x Use of tomography retrievals in severe weather
investigation, [SEVERE]
x Use of tomography retrieval in weather systemassimilation. [ASSIMILATION]

Structures for the Period 2015-2019

1054

WG 4.3.7: Real-time Troposphere Monitoring

Members

Chair: Jan Dousa (Czech Republic)

Jan Dousa (Chair, Czech Republic)
John Braun (USA)Junping Chen (China)
Galina Dick (Germany)
Siebren de Haan (Netherlands)
Tomasz Hadaś (Poland)
Fabian Hinterberger (Austria)
Jonathan Jones (UK)Min Li (China)
Xingxing Li (Germany)
Thaleia Nikolaidou (Canada)
Rosa Pacione (Italy)
Eric Pottiaux (Belgium)
Yoshinory Shoji (Japan)
Felix Norman Teferle (Luxembourg)
Pavel Václavovic (Czech Republic)
Henrik Vedel (Denmark)Xiaoming Wang (Australia)
Kefei Zhang (Australia)

Description
The main objective of this WG is to develop, optimize andassess new real-time or ultra-fast tropospheric products
using data from GNSS permanent networks. Troposphericzenith total delays, tropospheric linear horizontal gradients,
slant delays, integrated water vapour (IWV) maps or otherderived products in sub-hourly fashion are foreseen for
future exploitation in numerical and non-numerical
weather nowcasting or severe weather event monitoring.
The use of Precise Point Positioning (PPP) processing
strategy will play a key role in developing new products
because it is an efficient and autonomous method, it issensitive to absolute tropospheric path delays, it caneffectively support real-time or ultra-fast production, it
may optimally exploit data from all GNSS multiconstellations, it can easily produce a full variety ofparameters such as zenith total delays, horizontal gradientsor slant path delays and it may also support as reasonable
as high temporal resolution of all the parameters. Last, but
not least, the PPP is supported with the global orbit andclock products provided by the real-time service of theInternational GNSS Service (IGS).
Objectives
x Develop optimal strategies for real-time/ultra-fast
tropospheric products suitable for numerical or nonnumerical weather nowcasting applications or severe
weather event monitoring.
x Stimulate development of application software forsupporting routine production.
x Demonstrate real-time/ultra-fast production, assess
applied methods, software and precise orbit and clock
products.
x Evaluate tropospheric parameters and their potential for
applications in meteorology
x Setup a link to the potential users, review productformat and requirements.

Commission 4 – Positioning and Applications

JWG 4.3.8: GNSS tropospheric products for Climate(joint with Commission 1)
Chair: Rosa Pacione (Italy)
Vice-Chair: Eric Pottiaux (Belgium)
Description
In many parts of the world, huge efforts are ongoing forproviding homogeneously reprocessed GNSS solutions
that are the basis for deriving very precise coordinates,
velocities and troposphere parameters (namely Zenith
Total tropospheric Delays and Horizontal Gradients).
These regional and global reprocessing campaigns are
possible thanks to the availability of 19+ years ofobservations from permanently observing GNSS stations
located worldwide (e.g. the IGS network), their regional
densifications (e.g. the EPN network), and of reprocessed
global orbit and clock products (e.g. those provided by the
IGS Analysis Centers). These long-term time series ofhomogeneously reprocessed troposphere parameters will
provide a GNSS climate data record with high potential forclimate monitoring. Unfortunately, these time series still
suffer from inhomogeneities (for example instrumental
changes, changes in the station environment) which canaffect the analysis of the long-term variability.
Objectives
The main objective of the working group is to assess
existing reprocessed GNSS tropospheric products, foster
the development of forthcoming reprocessing activities andpromote their use for climate research.
The objectives of this WG are:x Assess existing reprocessed troposphere solutions andprovide recommendations for the forthcoming
reprocessing activities.
x Set-up a common GNSS climate dataset on which
different homogenization methodologies can be tested.
The homogenized common long-term dataset can thenbe reused for climate trends and variability studies
within the community.
x Stimulate the data assimilation of GNSS troposphere
products in Climate Models.
x Review and update GNSS-based product requirements
and exchange format for climate.
x Strengthen the cooperation between geodesists andclimatologists.

1055

Members
Rosa Pacione (Chair, Italy)
Eric Pottiaux (Vice-Chair, Belgium)
Fadwa Alshawaf (Germany)
Andrzej Araszkiewicz (Poland)
Olivier Bock (France)
Galina Dick (Germany)
Jan Douša (Czech Republic)
Gemma Halloran (United Kingdom)
Robert Heinkelmann (Germany)
Tong Ning (Sweden)
Felix Norman (Luxembourg)
Marcelo Santos (Canada)
Roeland Van Malderen (Belgium)
Sibylle Vey (Germany)
June Wang (USA)Structures for the Period 2015-2019

1056

WG 4.3.9: GNSS-R
Chair: Felipe Nievinski (Brazil)
Vice-Chair: Thomas Hobiger (Sweden)
Description
Global Navigation Satellite Systems (GNSS) have not only
revolutionized positioning, navigation, and timing but also
lead to the development of many other applications whichwere not anticipated when those satellite systems were
designed decades ago. The most prominent example for anovel application from recent years is the usage ofreflected GNSS signals as a new tool for remote sensing.
GNSS-R enables us to derive geometric and physicalcharacteristics of the reflecting surface by analysing andinterpreting features of the received signals. GNSS-R has
started to make an impact in the discipline of remotesensing but it still has not reached the focus of a broader
geodetic community although topics like sea-levelmonitoring, hydrological loading, and water cycle anddrought/flooding observations are highly relevant to thegoals of the Global Geodetic Observing System (GGOS).
Thus, the overall aim of this working group is to bridge thegap between GNSS-R and the geodetic community, by
seeking to raise the awareness of its relevance to several
geodetic problems as well as opportunities.
Objectives
x Identify GNSS-R data products which have a strong
relation to IAG services and goals.
x Foster and establish interactions with neighbouring
societies (such as the IEEE Geoscience and Remote
Sensing Society, IGARSS) and cooperate withtechnological, engineering, and operational entities
related to GNSS (e.g., the International GNSS Service,
IGS), identifying common goals and detecting potential
synergies.
x Provide an online inventory of GNSS-R products
relevant to geodesy and point to corresponding dataarchives.
x Evaluate the possibility to obtain formal errors for
GNSS-R products in order to enable better combination
with other datasets.
x Provide guidelines and define formats for GNSS-R
products being used for geodetic purposes.
x Organize working meetings with GNSS-R experts,
while also inviting stakeholders from the geodetic
community to participate in such events.

x Extend IGS Site Guidelines so as to maximize theshared usefulness of new GNSS site installations forreflectometry applications.
x Supplement the GNSS-R Campaign Spreadsheet(initiated by the IEEE GARSS) so as to list existing
GNSS tracking stations that can be leveraged forreflectometry purposes.
x Evaluate the feasibility of a pilot project on GNSS-R for
coastal sea level monitoring, demonstrating its current
level of maturity towards an operational service;possibly in cooperation with the IGS Tide Gauge WG(IGS-TIGA).
x Plan future inter-comparison campaigns for thevalidation of theoretical model simulations as well as
parameter retrievals based on measured data.
Members
Felipe Nievinski (Chair, Brazil)
Thomas Hobiger (Vice-Chair, Sweden)
Estel Cardellach (Spain)
Rüdiger Haas (Sweden)
Kosuke Heki (Japan)
Yukihito Kitazawa (Japan)
Kristine Larson (USA)Manuel Martín-Neira (ESA)
Miguel Angel Ribot (Switzerland)
Nicolas Roussel (France)
Maximilian Semmling (Germany)
Joakim Strandberg (Sweden)
Kegen Yu (China)
Sibylle Vey (Germany)
Wei Wan (China)
Jens Wickert (Germany)
Simon Williams (UK)Commission 4 – Positioning and Applications

1057

SC 4.4: Multi-constellation GNSS

Study Groups of Sub-Commission 4.4

Chair: Pawel Wielgosz (Poland)
Vice-Chair: Yang Gao (Canada)
Secretary: George Liu (China)

SG 4.4.1: Integrity Monitoring for Precise Positioning
Chair: Ahmed El-Mowafy (Australia).
Vice-Chair: Aboelmagd Noureldin (Canada).

Terms of Reference
Description
Multi-GNSS Constellation is rapidly growing extending
the number of satellites and available signals/frequencies.
In addition to two already operational GPS and GLONASS
systems, the new Galileo and BDS systems are underconstruction. Both GPS and GLONASS are currently
undergoing a significant modernization, which adds morecapacity,more
signals,
betteraccuracy
andinteroperability, etc. These new developments in GNSS
provide opportunities to create new high-precision GNSS
technologies and applications and also to open new
research areas. This, however, results in new challenges in
multi-GNSS data processing. Recognizing the central roleof GNSS in providing high accuracy positioning
information, the SC4.4 will foster research that address
standards, theory and applications of Multi-GNSS
Constellation. SC4.4 will coordinate activities to deliver
practical and theoretical solutions for engineering andscientific applications and also will stimulate strong
collaboration with the IAG Services (IGS) as well as with
relevant entities within scientific and professional sisterorganizations (FIG, IEEE and ION).
Objectives
The major objective of SC4.4 is to promote collective
research on Multi-Constellation GNSS methods andtechnologies and their novel applications to facilitate
timely dissemination of scientific findings, to stimulate
strong collaborations among researchers and internationalorganizations and the industry.
Program of activities
x

x
x
x

to identify and investigate important scientific andtechnical issues in Multi-Constellation GNSS
applications,to stimulate strong collaborations among researchers,
to organize international conferences and workshops,
to promote the use of multi-GNSS techniques andproducts in interdisciplinary scientific research andengineering applications.

The use of GNSS for real-time precise positioning, defined
here as positioning at cm to sub-meter accuracy level,
relays on GNSS signals that have well-known
vulnerabilities and the use of supplementary systems tocalibrate measurement biases. In addition, when working
in urban environment or in case of a break in receiving thereference station data, GNSS need to be integrated withother sensors such IMU and speed sensors. For a user, suchas driverless cars, intelligent transport systems (ITS) andUAVs, with such vulnerabilities and mixture of systems,
integrity monitoring is important for protection from faults
and to alert the user in case that the system cannot reachthe target performance.
This Study Group (SG) will endeavour to research anddevelop a framework, including theory and algorithms, forintegrity monitoring of precise positioning in a number ofapplications. It will include precise positioning from
GNSS in a stand-alone mode, e.g. in Precis Point
Positioning (PPP), Real-Time Kinematic (RTK) or
Network RTK processing, and when being integrated withother sensors such as IMU and speed sensors. The study
group will carry out its work in close cooperation withother IAG and integrity monitoring groups, as well as via
linkages with relevant scientific and professionalorganizations such as IGS, FIG, IEEE and ION. The SG
will document the body of knowledge in the proposed fieldand present such knowledge at symposia and workshops.
Members
Ahmed El-Mowafy (Chair, Australia)
Aboelmagd Noureldin (Vice-Chair, Canada)
Slawomir Cellmer (Poland).
Naser El-Sheimy (Canada)
Per Enge (USA)
Pedro Francisco Navarro Madrid (Spain).
Allison Kelley (Australia),
Samer Khanafseh (USA)Nobuaki Kubo (Japan).
Ilaria Martini (Germany),Structures for the Period 2015-2019

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Working Groups of Sub-Commission 4.4

WG 4.4.2: Integer Ambiguity Resolution for MultiGNSS PPP and PPP-RTK

WG 4.4.1: Biases in Multi-GNSS data processing
Chair: Xingxing Li (Germany)
Vice-Chair: Jan Dousa (Czech Republic)

Chair: Xiaohong Zhang (China)
Vice-Chair: Sue Lynn Choy (Australia)
Description

Description
To address and investigate issues related to the various
biases in multi-GNSS data processing. The main research
focus will include the definition and mathematicalrepresentation of various biases in multi-GNSS, their
spatiotemporal characters and the related mechanism,
precise bias modeling and the estimability, thedevelopment of rigorous multi-GNSS algorithms, toimprove positioning performance and to enhancecomputational efficiency (especially for real-time orbit andclock determination) through proper bias estimation andcorrection. The continuous effort is to tightly integrate
multi-GNSS signals together through precise determination
and application of the biases for the best positioning
performance.

To study the methodology of integer ambiguity resolution
for Multi-GNSS PPP and investigate issues and problemsof Multi-GNSS PPP related to ambiguity initialization
time, success rate, accuracy and reliability etc. The
research will focus on the following areas: thedevelopment of methods and algorithms for integer
ambiguity resolution in Multi-GNSS precise point
positioning; the development of new ionosphericcorrection model to speed up PPP ambiguity initialization
time, and the real-time implementation and standardizationof PPP-based Multi-GNSS RTK systems. The working
group will carry out its work in close cooperation withother IAG groups and FIG to promote the use of multiGNSS techniques and products in interdisciplinaryscientific research and engineering applications

Members

Members

Xingxing Li (Chair, Germany)
Jan Dousa (Vice-Chair, Czech Republic)
Ahmed El-Mowafy (Australia)
Yang Gao (Canada)
Fei Guo (China)
Haibo He (China)
Shuanggen Jin (China)
Richard Langley (Canada)
Bofeng Li (China)
Zishen Li (China)
Yidong Lou (China)
Felipe Nievinski (Brazil).
Jacek Paziewski (Poland)
Nigel Penna (UK)
Chris Rizos (Australia)
Pavel Vaclavovic (Czech Republic)
Jinling Wang (Australia)
Ningbo Wang (China)
Xiaoming Wang (Australia)
Robert Weber (Austria)
Suqin Wu (Australia)
Tianhe Xu (China)

Xiaohong Zhang (Chair, China)
Sue Lynn Choy (Vice-Chair, Australia)
Simon Banville (Canada)
Maorong Ge (Germany)
Jianghui Geng (China)
Marco Mendonça (Canada)
Baocheng Zhang (Australia)

Inter-Commission Committee on Theory (ICCT)

1059

Inter-Commission Committee on Theory (ICCT)
President: Pavel Novák (Czech Republic)
Vice President: Mattia Crespi (Italy)
http://icct.kma.zcu.cz

Terms of Reference
The Inter-Commission Committee on Theory (ICCT) was
formally approved and established after the IUGG XXI
Assembly in Sapporo, 2003, to succeed the former IAG
Section IV on General Theory and Methodology and, more
importantly, to interact actively and directly with other
IAG entities, namely commissions, services and the Global
Geodetic Observing System (GGOS). In accordance with
the IAG by-laws, the first two 4-year periods werereviewed in 2011. IAG approved the continuation of ICCTat the IUGG XXIII Assembly in Melbourne, 2011. At the
IUGG XXIV Assembly in Prague, 2015, ICCT became apermanent entity within the IAG structure.
Recognizing that observing systems in all branches ofgeodesy have advanced to such an extent that geodetic
measurements (i) are now of unprecedented accuracy andquality, can readily cover a region of any scale up to tensof thousands of kilometres, yield non-conventional datatypes, and can be provided continuously; and (ii)consequently, demand advanced mathematical modellingin order to obtain the maximum benefit of suchtechnological advance, ICCT (1) strongly encourages
frontier mathematical and physical research, directly
motivated by geodetic need and practice, as a contribution
to science and engineering in general and theoreticalfoundations of geodesy in particular; (2) provides thechannel of communication amongst different IAG entities
of commissions, services and projects on the ground oftheory and methodology, and directly cooperates with andsupports these entities in the topical work; (3) helps IAG in
articulating mathematical and physical challenges ofgeodesy as a subject of science and in attracting young
talents to geodesy. ICCT strives to attract and serve ashome to all mathematically motivated and oriented

geodesists as well as to applied mathematicians; and (4)encourages closer research ties with and gets directly
involved in relevant areas of Earth sciences, bearing in
mind that geodesy has always been playing an importantrole in understanding the physics of the Earth.

Objectives
The overall objectives of the ICCT are
x To act as international focus of theoretical geodesy;x To encourage and initiate activities to advance geodetic
theory in all branches of geodesy;x To monitor developments in geodetic methodology.
To achieve these objectives, ICCT interacts andcollaborates with the IAG Commissions, GGOS and other
IAG related entities (services, projects).

Program of Activities
The ICCT's program of activities include
x participation as (co-)conveners of geodesy sessions atmajor conferences such as IAG, EGU and AGU,
x organization of Hotine-Marussi symposia,
x initiation of summer schools on theoretical geodesy,x and maintaining a website for dissemination of ICCT
related information.

Structure
The general structure of Inter-Commission Committees is
specified in the IAG By-laws (§17). The steeringcommittee shall include the president, the vice-president
and one representative appointed by each Commission.
The ICCT activities are structured in study groups. Due tothe inter-commission character of the ICCT, these study
groups are always Joint Study Groups, affiliated to one ormore of the Commissions and/or to GGOS.

Structures for the Period 2015-2019

1060

Joint Study Groups
JSG 0.10: High-rate GNSS
Chair: M. Crespi (Italy)(Affiliation: Commission 4 and GGOS)
JSG 0.11: Multiresolution aspects of potential field theory
Chair: D. Tsoulis (Greece)(Affiliation: Commissions 2 and GGOS)
JSG 0.12: Advanced computational methods for recoveryof high-resolution gravity field models
Chair: R. Čunderlík (Slovak Republic)(Affiliation: Commission 2 and GGOS)
JSG 0.13: Integral equations of potential theory forcontinuation and transformation of classical andnew gravitational observables
Chair: M. Šprlák (Czech Republic)(Affiliation: Commission 2 and GGOS)
JSG 0.14: Fusion of multi-technique satellite geodetic data
Chair: K. Sośnica (Poland)(Affiliation: Commission 4 and GGOS)
JSG 0.15 Regional geoid/quasi-geoid modelling –Theoretical framework for the sub-centimetre
accuracy
Chair: J. Huang (Canada)(Affiliation: Commission 2 and GGOS)
JSG 0.16 Earth’s inner structure from combined geodetic
and geophysical sources
Chair: R. Tenzer (China)(Affiliation: Commissions 2 and 3)
JSG 0.17 Multi-GNSS theory and algorithms
Chair: A. Khodabandeh (Australia)(Affiliation: Commission 4 and GGOS)
JSG 0.18 High resolution harmonic analysis and synthesisof potential fields
Chair: S. Claessens (Australia)(Affiliation: Commission 2 and GGOS)
JSG 0.19 Time series analysis in geodesy
Chair: W. Kosek (Poland)(Affiliation: Commission 3 and GGOS)
JSG 0.20 Space weather and ionosphere
Chair: K. Börger (Germany)(Affiliation: Commission 4 and GGOS)

JSG 0.21 Geophysical modelling of time variations indeformation and gravity
Chair: Y. Tanaka (Japan)(Affiliation: Commissions 2 and 3)
JSG 0.22 Definition of next generation terrestrialreference frames
Chair: K. Kotsakis (Greece)(Affiliation: Commissions 1 and GGOS)

Steering Committee
ICCT President:
Pavel Novák (Czech Republic)
ICCT Vice-President:
Mattia Crespi (Italy)
ICCT Past-President:
Nico Sneeuw (Germany)
Representative Comm. 1: Geoffrey Blewitt (USA)
Representative Comm. 2: Roland Pail (Germany)
Representative Comm. 3: Manabu Hashimoto (Japan)
Representative Comm. 4: Marcelo Santos (Canada)
Representative of GGOS: Hansjörg Kutterer (Germany)
Representative of IGFS: Riccardo Barzaghi (Italy)
Representative of IERS: Jürgen Müller (Germany)

Inter-Commission Committee on Theory (ICCT)

Joint Study Groups of the ICCTJSG 0.10: High-rate GNSS
(Affiliation: Commission 4 and GGOS)
Chair: M. Crespi (Italy)
Introduction
Global Navigation Satellite Systems (GNSS) have become
for a long time an indispensable tool to get accurate andreliable information about positioning and timing; inaddition, GNSS are able to provide information related tophysical properties of media passed through by GNSS
signals. Therefore, GNSS play a central role both ingeodesy and geomatics and in several branches ofgeophysics, representing a cornerstone for the observationand monitoring of our planet.
So, it is not surprising that, from the very beginning of
the GNSS era, the goal was pursued to widen the range inspace (from local to global) and time (from short to longterm) of the observed phenomena, in order to cover thelargest possible field of applications, both in science and inengineering; two complementary, but primary as well,goals were, obviously, to get this information with thehighest accuracy and in the shortest time.
The advances in technology and the deployment of new
constellations, after GPS (in the next years will becompleted the European Galileo, the Chinese Beidou and
the Japanese QZSS) remarkably contributed to transform
this three-goals dream in reality, but still remain
significant challenges when very fast phenomena have tobe observed, mainly if real-time results are looked for.
Actually, for almost 15 years, starting from the noble
birth in seismology, and the very first experiences instructural monitoring, high-rate GNSS has demonstrated its
usefulness and power in providing precise positioning
information in fast time-varying environments. At the
beginning, high-rate observations were mostly limited at 1
Hz, but the technology development provided GNSS
equipment (in some cases even at low-cost) able to collectmeasurements at much higher rates, up to 100 Hz,
therefore opening new possibilities, and meanwhile newchallenges and problems.
So, it is necessary to think about how to optimallyprocess this potential huge heap of data, in order to supply
information of high value for a large (and likely
increasing) variety of applications, some of them listed
hereafter without the claim to be exhaustive: better
understanding of the geophysical/geodynamical processes
mechanics; monitoring of ground shaking anddisplacement during earthquakes, also for contribution totsunami early warning; tracking the fast variations of the1061

ionosphere; real-time controlling landslides and the safetyof structures; providing detailed trajectories and kinematicparameters (not only position, but also velocity andacceleration) of high dynamic platforms such as airborne
sensors, high-speed terrestrial vehicles and even athlete
and sport vehicles monitoring.
Further, due to the contemporary technologicaldevelopment of other sensors (hereafter referred asancillary sensors) related to positioning and kinematics
able to collect data at high-rate (among which MEMS
accelerometers and gyros play a central role, also for their
low-cost), the feasibility of a unique device for high-rate
observations embedding GNSS receiver and MEMS
sensors is real, and it open, again, new opportunities andproblems, first of all related to sensors integration.
All in all, it is clear that high-rate GNSS (and ancillary
sensors) observations represent a great resource for future
investigations in Earth sciences and applications inengineering, meanwhile stimulating a due attention fromthe methodological point of view in order to exploit theirfull potential and extract the best information. This is thewhy it is worth to open a focus on high-rate (and, if
possible, real-time) GNSS within ICCT.
Objectives
x To realize the inventories of: the available and applied methodologies for high-rate
GNSS, in order to highlight their pros and cons andthe open problems; the present and wished applications of high-rate
GNSS for science and engineering, with a special
concern to the estimated quantities (geodetic, kinematic,
physical), in order to focus on related problems (still
open and possibly new) and draw future challenges;
 the technology (hw, both for GNSS and ancillary
sensors, and sw, possibly FOSS), pointing out what isready and what is coming, with a special concern forthe supplied observations and for their functional andstochastic modeling with the by-product of
establishing a standardized terminology;
x To address known (mostly cross-linked) problems
related to high-rate GNSS as (not an exhaustive list):
revision and refinement of functional and stochastic
models; evaluation and impact of observations timecorrelation; impact of multipath and constellation
change; outliers detection and removal; issues about
GNSS constellations interoperability; ancillary sensors
evaluation, cross-calibration and integration;
x To address the new problems and future challanges
arised from the inventories;

Structures for the Period 2015-20191062

x To investigate the inter-action with present real-time
global (IGS-RTS, EUREF-IP, etc.) and regional/local
positioning services: how can these services support
high-rate GNSS observations and, on reverse, how canthey benefit of high-rate GNSS observations.
Program of activities
x To launch a questionnaire for the above mentioned
inventory of methodologies, applications andtechnologies;
x To open a web page with information concerning highrate GNSS and its wide applications in science andengineering, with special emphasis on exchange ofideas, provision and updating bibliographic list ofreferences of research results and relevant publications
from different disciplines;
x To launch the proposal for two (one science and one
engineering oriented) state-of-the-art review papers inhigh-rate GNSS co-authored by the JSG members.
x To organize a session at the forthcoming HotineMarussi symposium;
x To promote sessions and presentation of the research
results at international symposia both related to Earthscience (IAG/IUGG, EGU, AGU) and engineering(meetings in structural and geotechnical engineering).
Members
Mattia Crespi (Italy), Chair
Juan Carlos Baez (Chile)
Elisa Benedetti (United Kingdom)
Geo Boffi (Switzerland)
Gabriele Colosimo (Switzerland)
Athanasios Dermanis (Greece)
Roberto Devoti (Italy)
Jeff Freymueller (USA)Joao Francisco Galera Monico (Brazil)
Jianghui Geng (Germany)
Kosuke Heki (Japan)
Melvin Hoyer (Venezuela)
Nanthi Nadarajah (Australia)
Yusaku Ohta (Japan)
Ruey-Juin Rau (China-Taipei)
Eugenio Realini (Italy)
Chris Rizos (Australia)
Nico Sneeuw (Germany)
Peiliang Xu (Japan)

JSG 0.11: Multiresolutional aspects of potential field
theory(Affiliation: Commission 2 and GGOS)
Chair: D. Tsoulis (Greece)
Introduction
The mathematical description and numerical computationof the gravity signal of finite distributions play a central
role in gravity field modelling and interpretation. Thereby,
the study of the field induced by ideal geometrical bodies,such as the cylinder, the rectangular prism or the generally
shaped polyhedron, is of special importance both as
fundamental case studies but also in the frame of terrain
correction computations over finite geographical regions.
Analytical and numerical tools have been developed forthe potential function and its derivatives up to second orderfor the most familiar ideal bodies, which are widely used ingravity related studies. Also, an abundance of
implementations have been proposed for computing thesequantities over grids of computational points, elaborating
data from digital terrain or crustal databases.
Scope of the Study Group is to investigate thepossibilities of applying wavelet and multiscale analysis
methods to compute the gravitational effect of known
density distributions. Starting from the cases of ideal
bodies and moving towards applications involving DTM
data, or hidden structures in the Earth's interior, it will be
attempted to derive explicit approaches for the individual
existing analytical, numerical or combined (hybrid)
methodologies. In this process, the mathematicalconsequences of expressing in the wavelet representation
standard tools of potential theory, such as the Gauss orGreen theorem, involved for example in the analyticalderivations of the polyhedral gravity signal, will be
addressed. Finally, a linkage to the coefficients obtained
from the numerical approaches but also to the potential
coefficients of currently available Earth gravity models
will also be envisaged.
Objectives
x Bibliographicalsurveyandidentificationofmultiresolutional techniques for expressing the gravity
field signal of finite distributions;x Case studies for different geometrical finite shapes;
x Comparison and assessment against existing analytical,
numerical and hybrid solutions;x Computations over finite regions in the frame ofclassical terrain correction computations;x Band limited validation against Earth gravity models.

Inter-Commission Committee on Theory (ICCT)Program of activities
x Active participation at major geodetic meetings.
x Organize a session at the forthcoming Hotine-Marussi
Symposium.
x Compile a bibliography with key publications both ontheory and applied case studies.
x Collaborate with other working groups and affiliated
IAG Commissions.
Members
Dimitrios Tsoulis (Greece), Chair
Katrin Bentel (USA)Maria Grazia D'Urso (Italy)
Christian Gerlach (Germany)
Wolfgang Keller (Germany)
Christopher Kotsakis (Greece)
Michael Kuhn (Australia)
Volker Michel (Germany)
Pavel Novák (Czech Republic)
Konstantinos Patlakis (Greece)
Clément Roussel (France)
Michael Sideris (Canada)
Jérôme Verdun (France)
Corresponding members
Christopher Jekeli (USA)Frederik Simons (USA)
Nico Sneeuw (Germany)1063

JSG 0.12: Advanced computational methods forrecovery of high-resolution gravity fieldmodels(Affiliation: Commission 2 and GGOS)
Chair: R. Čunderlík (Slovak Republic)
Introduction
Efficient numerical methods and HPC (high performancecomputing) facilities provide new opportunities in many
applications in geodesy. The goal of the JSG is to apply
numerical methods and/or HPC techniques mostly for gravity
field modelling and nonlinear filtering of various geodetic data.
The discretization numerical methods like the finite element
method (FEM), finite volume method (FVM) and boundary
element method (BEM) or the meshless methods like themethod of fundamental solutions (MFS) or singular boundary
method (SOR) can be efficiently used to solve the geodetic
boundary value problems and nonlinear diffusion filtering, or toprocess e.g. the GOCE observations. Their parallel implementations and large-scale parallel computations on clusters with
distributed memory using the MPI (Message Passing Interface)standards allows to solve such problems in spatial domains
while obtaining high-resolution numerical solutions.
The JSG is also open for researchers dealing with theclassical approaches of gravity field modelling (e.g. thespherical or ellipsoidal harmonics) that are using highperformance computing to speed up their processing ofenormous amount of input data. This includes large-scaleparallel computations on massively parallel architectures
as well as heterogeneous parallel computations usinggraphics processing units (GPUs).
Applications of the aforementioned numerical methods forgravity field modelling involve a detailed discretization of thereal Earth’s surface considering its topography. It naturally
leads to the oblique derivative problem that needs to be treated.
In case of FEM or FVM, unstructured meshes above thetopography will be constructed. The meshless methods like
MFS or SBM that are based on the point-masses modelling canbe applied for processing the gravity gradients observed by the
GOCE satellite mission. To reach precise and high-resolution
solutions, an elimination of far zones’ contributions ispractically inevitable. This can be performed using the fastmultipole method or iterative procedures. In both cases such anelimination process improves conditioning of the system matrix
and a numerical stability of the problem.
The aim of the JSG is to investigate and develop nonlinear
filtering methods that allow adaptive smoothing, which
effectively reduces the noise while preserves main structures indata. The proposed approach is based on a numerical solutionof partial differential equations using a surface finite volume
method. It leads to a semi-implicit numerical scheme of theStructures for the Period 2015-20191064

nonlinear diffusion equation on a closed surface where thediffusivity coefficients depend on a combination of theedge detector and a mean curvature of the filtered function.
This will avoid undesirable smoothing of local extremes.

JSG 0.13: Integral equations of potential theory forcontinuation and transformation of classicaland new gravitational observables(Affiliation: Commission 2 and GGOS)

Objectives

Chair: M. Šprlák (Czech Republic)

The main objectives of the study group are as follows:x To develop algorithms for detailed discretization of thereal Earth’s surface including the possibility of adaptiverefinement procedures;x To create unstructured meshes above the topography for
the FVM or FEM approach;x To develop the FVM, BEM or FEM numerical models
for solving the geodetic BVPs that will treat the obliquederivative problem;x To develop numerical models based on MFS or SBM
for processing the GOCE observations;x Tto develop parallel implementations of algorithms
using the standard MPI procedures;x To perform large-scale parallel computations on clusters
with distributed memory;x To investigate and develop methods for nonlinear diffusion
filtering of data on the Earth’s surface where the diffusivity
coefficients depend on a combination of the edge
detector and a mean curvature of the filtered function;
x To derive the semi-implicit numerical schemes for the
nonlinear diffusion equation on closed surfaces using
the surface FVM; andx To apply the developed nonlinear filtering methods toreal geodetic data.

Introduction

Program of activities
x Active participation at major geodetic workshops andconferences.
x Organization of group working meetings at maininternational symposia.
x Organization of conference sessions.
Members
Róbert Čunderlík (Slovak Republic), Chair
Karol Mikula (Slovak Republic), Vice-chair
Jan Martin Brockmann (Germany)
Walyeldeen Godah (Poland)
Petr Holota (Czech Republic)
Michal Kollár (Slovak Republic)
Marek Macák (Slovak Republic)
Zuzana Minarechová (Slovak Republic)
Otakar Nesvadba (Czech Republic)
Wolf-Dieter Schuh (Germany)

The description of the Earth's gravitational field and its
temporal variations belongs to fundamental pillars ofmodern geodesy. The accurate knowledge of the global
gravitational field is important in many applications
including precise positioning, metrology, geophysics,
geodynamics, oceanography, hydrology, cryospheric andother geosciences. Various observation techniques forcollecting gravitational data have been invented based onterrestrial, marine, airborne and more recently, satellite
sensors. On the other hand, different parametrization methodsof the gravitational field were established in geodesy,
however, with many unobservable parameters. For thisreason, the geodetic science has traditionally been formulating
various gravitational parameter transformations, including
those based on solving boundary/initial value problems ofpotential theory, through Fredholm's integral equations.
Traditionally, Stokes’s, Vening-Meinesz’s and Hotine’s
integrals have been of interest in geodesy as they accommodated geodetic applications. In recent history, new geodetic
integral transformations were formulated. This effort was
mainly initiated by new gravitational observables that became
available to geodesists with the advent of precise GNSS
(Global Navigation Satellite Systems) positioning, satellite
altimetry and aerial gravimetry/gradiometry. The family of
integral transformations has enormously been extended
with satellite-to-satellite tracking and satellite gradiometricdata available from recent gravity-dedicated satellite missions.
Besides numerous efforts in developing integral equations tocover new observables in geodesy, many aspects of integral
equations remain challenging. This study group aims for
systematic treatment of integral transformation in geodesy, as
many formulations have been performed by making use ofvarious approaches. Many solutions are based on sphericalapproximation that cannot be justified for globally distributed
satellite data and with respect to requirements of various data
users requiring gravitational data to be distributed the reference
ellipsoid or at constant geodetic altitude. On the other hand, theintegral equations in spherical approximation possess
symmetric properties that allow for studying their spatial andspectral properties; they also motivate for adopting ageneralized notation. New numerically efficient, stable andaccurate methods for upward/downward continuation,comparison, validation, transformation, combination and/or forInter-Commission Committee on Theory (ICCT)interpretation of gravitational data are also of high interest withincreasing availability of large amounts of new data.

1065

JSG 0.14: Fusion of multi-technique satellite geodetic
data(Affiliation: Commission 4 and GGOS)

Objectives
x To consider different types of gravitational data, i.e.,terrestrial, aerial and satellite, available today and toformulate their mathematical relation to thegravitational potential;
x To study mathematical properties of differential operators in
spherical and Jacobi ellipsoidal coordinates, which
relate various functionals of the gravitational potential;
x To complete the family of integral equations relating various
types of current and foreseen gravitational data and to derivecorresponding spherical and ellipsoidal Green’s functions;x To study accurate and numerically stable methods for
upward/downward continuation of gravitational fieldparameters;x To investigate optimal combination techniques ofheterogeneous gravitational field observables forgravitational field modelling at all scales;
x To investigate conditionality as well as spatial andspectral properties of linear operators based on
discretized integral equations;x To classify integral transformations and to propose
suitable generalized notation for a variety of classicaland new integral equations in geodesy.
Program of activities
x Presenting research results at major international geodetic
and geophysical conferences, meetings and workshops;
x Organizing a session at the forthcoming Hotine-Marussi
Symposium 2017;
x Cooperating with related IAG Commissions and GGOS;
x Monitoring activities of JGS members as well as otherscientists related to the scope of JGS activities;
x Providing bibliographic list of relevant publications
from different disciplines in the area of JSG interest.
Members
Michal Šprlák (Czech Republic), Chair
Alireza Ardalan (Iran)
Mehdi Eshagh (Sweden)
Will Featherstone (Australia)
Ismael Foroughi (Canada)Peter Holota (Czech Republic)
Juraj Janák (Slovak Republic)
Otakar Nesvadba (Czech Republic)
Pavel Novák (Czech Republic)
Martin Pitoňák (Czech Republic)
Robert Tenzer (China)
Gyula Tóth (Hungary)

Chair: K. Sośnica (Poland)
Introduction
Observations provided by space geodetic techniquesdeliver a global picture of the changing system Earth, inparticular temporal changes of the Earth’s gravity field,
irregularities in the Earth rotation and variations of station
positions due to various geodynamical phenomena.
Different techniques are characterized by different
accuracy and different sensitivity to geodetic parameters,e.g., GNSS provides most accurate pole coordinates, butcannot provide the absolute information on UT1-UTC, andthus, must be integrated with VLBI or LLR data. GRACE
observations provide state-of-the-art and most accurate
information on temporal changes of the gravity field, but
the temporal changes of the Earth’s oblateness or the
geocentre motion can be better determined using SLR data.
Therefore, a fusion of various space geodetic observations
is an indispensable prerequisite for a reliable description of
the varying system Earth.
However, the space geodetic observations are typicallynot free of artifacts related to deficiencies in various
models used in the data reduction process. GNSS satellite
orbits are very sensitive to deficiencies in solar radiationpressure modeling affecting, e.g., the accuracy of GNSSderived Earth rotation parameters and geocentre
coordinates. Deficiencies in modeling of antenna phasecenter offsets, albedo and the antenna thrust limit thereliability of GNSS and DORIS-derived scale of theterrestrial reference frame, despite a good global coverageof GNSS receivers and DORIS beacons. VLBI solutions
are affected by an inhomogeneous quality delivered bydifferent stations and antenna deformations. SLR techniqueis affected by the Blue-Sky effect which is related to theweather dependency of laser observations and the stationdependent satellite signature effect due to multiple
reflections from many retroreflectors. Moreover, unmodeled horizontal gradients of the troposphere delay in
SLR analyzes also limit the quality of SLR solutions.
Finally, GRACE data are very sensitive to aliasing with
diurnal and semidiurnal tides, whereas GOCE and Swarm
orbits show a worse quality around the geomagnetic
equator due to deficiencies in ionosphere delay modeling.
Separation of real geophysical signals and artifacts ingeodetic observations yield a very challenging objective. A
fusion of different observational techniques of space
geodesy may enhance our knowledge on systematicStructures for the Period 2015-20191066

effects, improve the consistency between different
observational techniques, and may help us to mitigate
artifacts in the geodetic time series.
The mitigation of artifacts using parameters derived bya fusion of different techniques of space geodesy should
comprise three steps: 1) identification of an artifact
through an analysis of geodetic parameters derived frommultiple techniques; 2) delivering a way to model anartifact; 3) applying the developed model to standard
solutions by the analysis centers.
Improving the consistency level through mitigating
artifacts in space geodetic observations will bring us closer
to fulfilling the objectives of the Global Geodetic
Observing System (GGOS), i.e., the 1-mm accuracy of
positions and 0.1-mm/year accuracy of the velocity
determination. Without a deep knowledge of systematiceffects in satellite geodetic data and without a proper
modeling thereof, the accomplishment of the GGOS goals
will never be possible.
Objectives
x Developing of data fusion methods based on geodetic
data from different sources;
x Accuracy assessment and simulations of geodetic
observations in order to fulfil GGOS’ goals;
x Study time series of geodetic parameters (geometry,gravity and rotation) and other derivative parameters(e.g., troposphere and ionosphere delays) determinedusing different techniques of space geodesy;x Investigating biases and systematic effects in single
techniques;x Combination of satellite geodetic observations at theobservation level and software synchronization;x Investigating various methods of technique colocations: through local ties, global ties, co-location in
space;
x Identifying artifacts in time series of geodetic
parameters using e.g., spatial, temporal, and spectral
analyzes;x Elaborating methods aimed at mitigating systematiceffects and artifacts;
x Determination of the statistical significance levels of theresults obtained by techniques using different methods
and algorithms;
x Comparison of different methods in order to point out
their advantages and disadvantages;
x Recommendations for analysis working groups andconventions.

Program of activities
x Preparing a web page with information concerning
integration and consistency of satellite geodetic
techniques and their integration with special emphasison exchange of ideas, providing and updating
bibliographic list of references of research results andrelevant publications from different disciplines.
x Working meetings at the international symposia andpresentation of research results at the appropriatesessions.
Members
Krzysztof Sośnica (Poland), Chair
Mathis Blossfeld (Germany)
Sara Bruni (Italy)
Claudia Flohrer (Germany)
Andrea Maier (Switzerland)
Toshimichi Otsubo (Japan)
Daniela Thaller (Germany)
Karina Wilgan (Poland)
Agnieszka Wnek (Poland)Inter-Commission Committee on Theory (ICCT)JSG 0.15: Regional geoid/quasi-geoid modelling –Theoretical framework for the subcentimetre accuracy(Affiliation: Commission 2 and GGOS)
Chair: J. Huang (Canada)
Introduction
A theoretical framework for the regional geoid/quasi-geoid
modelling is a conceptual structure to solve a geodetic
boundary value problem regionally. It is a physically soundintegration of a set of coherent definitions, physical models
and constants, geodetic reference systems andmathematical equations. Current frameworks are designed
to solve one of the two geodetic boundary value problems:
Stokes’s and Molodensky’s. These frameworks wereoriginally established and subsequently refined for many
decades to get the best accuracy of the geoid/quasi-geoid
model. The regional geoid/quasi-geoid model can now be
determined with an accuracy of a few centimeters in a
number of regions in the world, and has been adopted todefine new vertical datum replacing the spirit-leveling
networks in New Zealand and Canada. More and morecountries are modernizing their existing height systems
with the geoid-based datum. Yet the geoid model stillneeds further improvement to match the accuracy of the
GNSS-based heightening. This requires the theory and its
numerical realization, to be of sub-centimeter accuracy,
and the availability of adequate data.
Regional geoid/quasi-geoid modelling often involves
the combination of satellite, airborne, terrestrial (shipborne
and land) gravity data through the remove-compute-restore
Stokes method and the least-squares collocation. Satellite
gravity data from recent gravity missions (GRACE andGOCE) enable to model the geoid components with anaccuracy of 1-2 cm at the spatial resolution of 100 km.
Airborne gravity data are covering more regions with avariety of accuracies and spatial resolutions such as the US
GRAV-D project. They often overlap with terrestrial
gravity data, which are still unique in determining thehigh-degree geoid components. It can be foreseen thatgravity data coverage will extend everywhere over lands,
in particular, airborne data, in the near future.
Furthermore, the digital elevation models required for thegravity reduction have achieved global coverage withredundancy. A pressing question to answer is if these data
are sufficiently accurate for the sub-centimeter
geoid/quasi-geoid determination. This study group focuses
on refining and establishing if necessary the theoreticalframeworks of the sub-centimeter geoid/quasi-geoid.

1067

Objectives
The theoretical frameworks of the sub-centimeter
geoid/quasi-geoid consist of, but are not limited to, thefollowing components to study:
x Physical constant GM;
x W0 convention and changes;
x Geo-center convention and motion with respect to theInternational Terrestrial Reference Frame (ITRF);
x Geodetic Reference Systems;
x Proper formulation of the geodetic boundary value problem;x Nonlinear solution of the formulated geodetic boundary
value problem;x Data type, distribution and quality requirements;
x Data interpolation and extrapolation methods;
x Gravity reduction including downward or upward
continuation from observation points down or up to thegeoid, in particular over mountainous regions, polar
glaciers and ice caps;
x Anomalous topographic mass density effect on thegeoid model;
x Spectral combination of different types of gravity datax Transformation between geoid and quasi-geoid models;x The time-variable geoid/quasi-geoid change modelling;x Estimation of the geoid/quasi-geoid model inaccuracies;x Independent validation of geoid/quasi-geoid models;x Applications of new tools such as the radial basis
functions.
Program of activities
x The study group achieves its objectives throughorganizing splinter meetings in coincidence with major
IAG conferences and workshops if possible.
x Circulating and sharing progress reports, papers andpresentations.
x Presenting and publishing papers in the IAG symposia
and scientific journals.
Members
Jianliang Huang (Canada), Chair
Yan Ming Wang (USA), Vice-chair
Riccardo Barzaghi (Italy)
Heiner Denker (Germany)
Will Featherstone (Australia)
René Forsberg (Denmark)Christian Gerlach (Germany)
Christian Hirt (Germany)
Urs Marti (Switzerland)
Petr Vaníček (Canada)Structures for the Period 2015-2019

1068

JSG 0.16: Earth’s inner structure from combined
geodetic and geophysical sources(Affiliation: Commissions 2 and 3)
Chair: R. Tenzer (China)
Introduction
The satellite gravimetry missions, CHAllenging Minisatellite Payload (CHAMP), the GRavity field and Climate
Experiment (GRACE) and the Gravity field and steadystate Ocean Circulation Explorer (GOCE), significantly
improved our knowledge on the external gravitational fieldof the Earth at the long-to-medium wavelengths(approximately up to a spherical harmonic degree of 250).
Such improved information in terms of the accuracy andresolution has been utilized in studies of the Earth’s
interior for a better understanding of the Earth’s inner
structure and processes occurring within the lithosphereand sub-lithospheric mantle. Whereas the long-wavelength
spectrum of the Earth’s gravitational field comprises
mainly the signature of deep mantle density heterogeneities
attributed to mantle convection, the medium wavelengths
reflect the density structure of more shallow sources within
the lithosphere. This allows studying and interpreting in
more detail the gravitational features which are related to
the global tectonism (including the oceanic subduction,
orogenic formations, earthquakes, global lithospheric plate
configuration, etc.), sub-lithospheric stresses, isostaticmechanisms, glacial isostatic adjustment, and other relatedgeodynamic phenomena. Moreover, the Global Gravitational
Models (GGMs) have been extensively used in studies ofthe lithospheric density structure and density interfaces
such as for the gravimetric recovery of the Moho depth,
lithospheric thickness, and structure of sedimentary basins.
Since the gravity observations could not be used alone
to interpret the Earth’s inner density structure due to a nonuniqueness of inverse solutions (i.e. infinity many 3-D
density structures could be attributed to the Earth’s gravity
field), additional information is required to constrain thegravimetric methods for interpreting the Earth’s interior.
These constraining data comprise primarily results ofseismic surveys as well as additional geophysical,
geothermal and geochemical parameters of the Earth.
Moreover, numerous recent gravimetric studies of the
Earth’s interior focus on the global and regional Moho
recovery. The classical isostatic models (according to Airyand Pratt theories) are typically not able to model
realistically the actual Moho geometry, due to the fact thatthe isostatic mass balance depends on loading and effective
elastic thickness, rigidity, rheology of the lithosphere andviscosity of the asthenosphere. Moreover, geodynamic

processes such as the glacial isostatic adjustment, presentday glacial melting, plate motion and mantle convection
contribute to the time-dependent isostatic balance. To
overcome these issues, processing strategies of combining
gravity and seismic data (and possibly also additional
constraining information) have to be applied to determine
the actual Moho geometry.
The gravimetric methods applied in studies of the
Earth’s inner density structure comprise - in principle - twocategories. The methods for the gravimetric forward
modeling are applied to model (and remove) thegravitational signature of known density structures in orderto enhance the gravitational contribution of unknown (andsought) density structures and interfaces. The gravimetricinverse methods are then used to interpret these unknown
density structures from the refined gravity data. It is
obvious that the combination of gravity and seismic data
(and other constraining information) is essential especiallyin solving the gravimetric inverse problems.
This gives us the platform and opportunities towards
improving the theoretical and numerical methods appliedin studies of Earth’s interior from multiple data sources,
primarily focusing but not restricting only to combining
gravimetric and seismic data. It is expected that the gravity
data could improve our knowledge of the Earth’s interior
over significant proportion of the world where seismic data
are sparse or completely absent (such large parts of oceanic
areas, Antarctica, Greenland and Africa). The gravity data
could also provide additional information on thelithospheric structure and mechanisms, such as global
tectonic configuration, geometry of subducted slabs, crustal
thickening of orogenic formations and other phenomena.
Objectives
x Development of the theoretical and numericalalgorithms for combined processing of gravity, seismic
and other types of geophysical data for a recovery of the
Earth’s density structures and interfaces.
x Development of fast numerical algorithms for combined
data inversions.
x Development of stochastic models for combined
inversion including optimal weighting, regularizationand spectral filtering.
x Better understanding of uncertainties of interpreted
results based on the error analysis of input data andapplied numerical models. Geophysical and geodynamic
clarification of results and their uncertainties.
x Recommendations for optimal data combinations, better
understanding of possibilities and limiting factors
associated with individual data types used forgeophysical and geodynamic interpretations.

Inter-Commission Committee on Theory (ICCT)Program of activities
x Launching of a web page with emphasis on exchange ofideas and recent progress, providing and updating
bibliographic list of references of research results andrelevant publications from different disciplines.
x Work progress meetings at the international symposia
and presentation of research results at the appropriatesessions.
x Possible collaboration between various geosciencestudy groups dealing with the modeling of the Earth’s
interior and related scientific topics.
Members
Robert Tenzer (China), Chair
Lars Sjöberg (Sweden)
Mohammad Bagherbandi (Sweden)
Carla Braitenberg (Italy)
Mehdi Eshagh (Sweden)
Mirko Reguzzoni (Italy)
Xiaodong Song (USA)1069

JSG 0.17: Multi-GNSS theory and algorithms(Affiliation: Commissions 1, 4 and GGOS)
Chair: A. Khodabandeh (Australia)
Introduction
In recent years, we are witnessing rapid development in thesatellite-based navigation and positioning systems. Next tothe modernization of the GPS dual-frequency signals to thetriple-frequency signals, the GLONASS satellites havebeen revitalized and become fully operational. The new
global and regional satellite constellations are also joining
the family of the navigation systems. These additions are
the two global systems of Galileo and BeiDou satellites aswell as the two regional systems of QZSS and IRNSS
satellites. This namely means that many more satellites
will be visible to the GNSS users, transmitting data on
many more frequencies than the current GPS dualfrequency setup, thereby expecting considerable
improvement in the performance of the positioning andnon-positioning GNSS applications.
Such a proliferation of multi-system, multi-frequency
data demands rigorous theoretical frameworks, models andalgorithms that enable the near-future multiple GNSSs toserve as a high-accuracy and high-integrity tool for the
Earth-, atmospheric- and space-sciences. For instance,
recent studies have revealed the existence of non-zero
inter-system and inter-system-type biases that, if ignored,
result in a catastrophic failure of integer ambiguity
resolution, thus deteriorating the corresponding ambiguity
resolved solutions. The availability of the new multisystem, multi-frequency data does therefore appeal proper
mathematical models so as to enable one to correctly
integrate such data, thus correctly linking the data to theestimable parameters of interest.
Objectives
The main objectives of this study group are:x to identify and investigate challenges that are posed byprocessing and integrating the data of the next
generation navigation and positioning satellite systems,
x to develop new functional and stochastic models linking
the multi-GNSS observations to the positioning andnon-positioning parameters,
x to derive optimal methods that are capable of handlingthe data-processing of large-scale networks of mixedreceiver types tracking multi-GNSS satellites,
x to conduct an in-depth analysis of the systematic
satellite- and receiver-dependent biases that are present
either within one or between multiple satellite systems,

Structures for the Period 2015-2019

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x to develop rigorous quality-control and integrity tools
for evaluating the reliability of the multi-GNSS data andguarding the underlying models against any mismodelled effects,
x to access the compatibility of the real-time multi-GNSS
input parameters for positioning and non-positioning
products,x to articulate the theoretical developments and findings
through the journals and conference proceedings.
Program of activities
While the investigation will be strongly based on thetheoretical aspects of the multi-GNSS observation
modelling and challenges, they will be also accompanied
by numerical studies of both the simulated and real-world
data. Given the expertise of each member, the underlying
studies will be conducted on both individual andcollaborative bases. The outputs of the group study is toprovide the geodesy and GNSS communities with welldocumented models and algorithmic methods through thejournals and conference proceedings.
Members
Amir Khodabandeh (Australia), ChairPeter J.G. Teunissen (Australia)
Pawel Wielgosz (Poland)
Bofeng Li (China)
Simon Banville (Canada)
Nobuaki Kubo (Japan)
Ali Reza Amiri-Simkooei (Iran)

Gabriele Giorgi (Germany)
Thalia Nikolaidou (Canada)

JSG 0.18: High resolution harmonic analysis andsynthesis of potential fields(Affiliation: Commission 2 and GGOS)
Chair: S. Claessens (Australia)
Introduction
The gravitational fields of the Earth and other celestialbodies in the Solar System are customarily represented bya series of spherical harmonic coefficients. The models
made up of these harmonic coefficients are used widely ina large range of applications within geodesy. In addition,
spherical harmonics are now used in many other areas ofscience such as geomagnetism, particle physics, planetarygeophysics, biochemistry and computer graphics, but oneof the first applications of spherical harmonics was related
to the gravitational potential, and geodesists are still at theforefront of research into spherical harmonics. This holds
true especially when it comes to the extension of sphericalharmonic series to ever higher degree and order (d/o).
The maximum d/o of spherical harmonic series of the
Earth’s gravitational potential has risen steadily over the
past decades. The highest d/o models currently listed by
the International Centre for Global Earth Models (ICGEM)
have a maximum d/o of 2190. In recent years, sphericalharmonic models of the topography and topographic
potential to d/o 10,800 have been computed, and with everincreasing computational prowess, expansions to evenhigher d/o are feasible. For comparison, the current
highest-resolution global gravity model has a resolution of7.2” in the space domain, which is roughly equivalent tod/o 90,000 in the frequency domain, while the highestresolution global Digital Elevation Model has a resolutionof 5 m, equivalent to d/o ~4,000,000.
The increasing maximum d/o of harmonic models has
posed and continues to pose both theoretical and practicalchallenges for the geodetic community. For example, thecomputation of associated Legendre functions of the firstkind, which are required for spherical harmonic analysis
and synthesis, is traditionally subject to numericalinstabilities and underflow/overflow problems. Much
progress has been made on this issue by selection ofsuitable recurrence relations, summation strategies, and useof extended range arithmetic, but further improvements toefficiency may still be achieved.
There are further separate challenges in ultra-high d/oharmonic analysis (the forward harmonic transform) andsynthesis (the inverse harmonic transform). Many methods
for the forward harmonic transform exist, typicallyseparated into least-squares and quadrature methods, andfurther comparison between the two at high d/o, including

Inter-Commission Committee on Theory (ICCT)

studying the influence of aliasing, is of interest. The
inverse harmonic transform, including synthesis of a large
variety of quantities, has received much interest in recent
years. In moving towards higher d/o series, highly efficientalgorithms for synthesis on irregular surfaces and/or inscattered point locations, are of utmost importance.
Another question that has occupied geodesists for many
decades is whether there is a substantial benefit to the useof oblate ellipsoidal (or spheroidal) harmonics instead ofspherical harmonics. The limitations of the sphericalharmonic series for use on or near the Earth’s surface are
becoming more and more apparent as the maximum d/o ofthe harmonic series increase. There are still open questions
about the divergence effect and the amplification of theomission error in spherical and spheroidal harmonic series
inside the Brillouin surface.
The Hotine-Jekeli transformation between spherical andspheroidal harmonic coefficients has proven very useful, inparticular for spherical harmonic analysis of data on areference ellipsoid. It has recently been improved upon andextended, while alternatives using surface sphericalharmonics have also been proposed, but the performanceof the transformations at very high d/o may be improved
further. Direct use of spheroidal harmonic series requires(ratios of) associated Legendre functions of the second
kind, and their stable and efficient computation is also of
ongoing interest.
Objectives
The objectives of this study group are to:x Create and compare stable and efficient methods forcomputation of ultra-high degree and order associatedLegendre functions of the first and second kind (orratios thereof), plus its derivatives and integrals;
x Study the divergence effect of ultra-high degree
spherical and spheroidal harmonic series inside theBrillouin sphere/spheroid;x Verify the numerical performance of transformations
between spherical and spheroidal harmonic coefficientsto ultra-high degree and order;x Compare least-squares and quadrature approaches tovery high-degree and order spherical and spheroidal
harmonic analysis;x Study efficient methods for ultra-high degree and orderharmonic analysis (the forward harmonic transform) fora variety of data types and boundary surfaces;x Study efficient methods for ultra-high degree and orderharmonic synthesis (the inverse harmonic transform) of
point values and area means of all potential quantities ofinterest on regular and irregular surfaces.

1071

Program of activities
x Providing a platform for increased cooperation between
group members, facilitating and encouraging exchangeof ideas and research results.
x Creating and updating a bibliographic list of relevantpublications from both the geodetic community as wellas other disciplines for the perusal of group members.
x Organizing working meetings at international symposia
and presenting research results in the appropriatesessions.
Members
Sten Claessens (Australia), Chair
Hussein Abd-Elmotaal (Egypt)
Oleh Abrykosov (Germany)Blažej Bucha (Slovak Republic)
Toshio Fukushima (Japan)
Thomas Grombein (Germany)
Christian Gruber (Germany)
Eliška Hamáčková (Czech Republic)
Christian Hirt (Germany)
Christopher Jekeli (USA)Otakar Nesvadba (Czech Republic)
Moritz Rexer (Germany)
Josef Sebera (Czech Republic)
Kurt Seitz (Germany)

Structures for the Period 2015-2019

1072

JSG 0.19: Time series analysis in geodesy(Affiliation: Commission 3 and GGOS)
Chair: W. Kosek (Poland)
Introduction
Observations of the space geodesy techniques and on the
Earth's surface deliver a global picture of the Earthdynamics represented in the form of time series which
describe 1) changes of the Earth surface geometry, 2) the
fluctuations in the Earth orientation, and 3) the variationsof the Earth’s gravitational field. The Earth's surface
geometry, rotation and gravity field are the threecomponents of the Global Geodetic Observing System(GGOS) which integrates them into one unique physicaland mathematical model. However, temporal variations ofthese three components represent the total, integral effectof all global mass exchange between all elements of the
Earth’s system including the Earth's interior and fluidlayers: atmosphere, ocean and land hydrology.
Different time series analysis methods have been
applied to analyze all these geodetic time series for better
understanding of the relations between all elements of the
Earth’s system as well as their geophysical causes. Theinteractions between different components of the Earth’s
system are very complex so the nature of consideredsignals in the geodetic time series is mostly wideband,irregular and non-stationary. Thus, it is recommended toapply wavelet based spectra-temporal analysis methods toanalyze these geodetic time series as well as to explain
their relations to geophysical processes in different
frequency bands using time-frequency semblance andcoherence methods. These spectra-temporal analysis
methods and time-frequency semblance and coherence
may be further developed to display reliably the features of
the temporal or spatial variability of signals existing invarious geodetic data, as well as in other source data
sources.
Geodetic time series include for example horizontal andvertical deformations of site positions determined fromobservations of space geodetic techniques. These site
positions change due to e.g. plate tectonics, postglacial
rebound, atmospheric, hydrology and ocean loading andearthquakes. However they are used to build the global
international terrestrial reference frame (ITRF) which must
be stable reference for all other geodetic observations
including e.g. satellite orbit parameters and Earth's
orientation parameters which consist of precession,
nutation, polar motion and UT1-UTC that are necessary fortransformation between the terrestrial and celestialreference frames. Geodetic time series include also

temporal variations of Earth's gravity field where 1 arc-deg
spherical harmonics correspond to the Earth’s centre ofmass variations (long term mean of them determines the
ITRF origin) and 2 degree spherical harmonics correspondto Earth rotation changes. Time series analysis methods
can be also applied to analyze data on the Earth's surface
including maps of the gravity field, sea level, ice covers,
ionospheric total electron content and tropospheric delay as
well as temporal variations of such surface data. The main
problems to deal with include the estimation ofdeterministic (including trend and periodic variations) andstochastic (non-periodic variations and random changes)
components of the geodetic time series as well as theapplication of digital filters for extracting specificcomponents with a chosen frequency bandwidth.
The multiple methods of time series analysis may be
encouraged to be applied to the preprocessing of raw datafrom various geodetic measurements in order to promote
the quality level of enhancement of signals existing inthese data. The topic on the improvement of the edge
effects in time series analysis may also be considered,since they may affect the reliability of long-range tendency(trends) estimated from data series as well as the real-timedata processing and prediction.
For coping with small geodetic samples one can apply
simulation-based methods and if the data are sparse,
Monte-Carlo simulation or bootstrap technique may be
useful. Understanding the nature of geodetic time series isvery important from the point of view of appropriate
spectral analysis as well as application of filtering andprediction methods.
Objectives
x Study of the nature of geodetic time series to choose
optimum time series analysis methods for filtering,
spectral analysis, time frequency analysis andprediction;x Study of Earth's geometry, rotation and gravity field
variations and their geophysical causes in different
frequency bands;
x Evaluation of appropriate covariance matrices for thetime series by applying the law of error propagation tothe original measurements, including weighting
schemes, regularization, etc.;x Determination of the statistical significance levels of theresults obtained by different time series analysis
methods and algorithms applied to geodetic time series.
x Development and comparison of different time series
analysis methods in order to point out their advantages
and disadvantages;

Inter-Commission Committee on Theory (ICCT)x Recommendations of different time series analysis
methods for solving problems concerning specificgeodetic time series.

1073

JSG 0.20: Space weather and ionosphere(Affiliation: Commissions 1, 4 and GGOS)
Chair: K. Börger (Germany)

Program of activities
x Launching of a website about time series analysis in
geodesy providing list of papers from different
disciplines as well as unification of terminology appliedin time series analysis;x Working meetings at the international symposia andpresentation of research results at the appropriatesessions.
Members
Wieslaw Kosek (Poland), Chair
Michael Schmidt (Germany)
Jan Vondrák (Czech Republic)
Waldemar Popinski (Poland)Tomasz Niedzielski (Poland)
Johannes Boehm (Austria)
Dawei Zheng (China)
Yonghong Zhou (China)
Mahmut O. Karslioglu (Turkey)
Orhan Akyilmaz (Turkey)
Laura Fernandez (Argentina)
Richard Gross (USA)Olivier de Viron (France)
Sergei Petrov (Russia)
Michel Van Camp (Belgium)
Hans Neuner (Germany)
Xavier Collilieux (France)

Introduction
It is well known that space geodetic methods are underinfluence of ionospheric refraction, and therefore from thevery beginning of these techniques geodesy deals with theionosphere. In this context sophisticated methods andmodels have been developed in order to determine, torepresent and to predict the ionosphere. Apart from this theionosphere fits into another issue called „space weather“,
which describes the interactions between the constituentsof space and earth. To be more precise space weather
means the conditions in space with a significant impact on
space-based and ground-based technology as well as onearth and its inhabitants. Solar radiation, that is
electromagnetic emission as well as particle emission, isthe main cause or “drive” of space weather.
Originally, geodesy, or to be more precise, space
geodetic methods have considered the ionosphere as a
disturbing factor that affects signal propagation and thathas to be corrected. This (geodetic) perspective has beenchanged over time and the ionosphere has become a target
value so that geodetic observations are used to determine
the ionosphere. Different groups have developed models ofhigh quality, e.g. 3D-models which describe theionosphere as a function of longitude, latitude and time oreven 4D-models accounting for the height as well.
However, since the ionosphere is a manifestation of space
weather, geodesy should contribute to space weather
research, and in this respect completely new scientificquestions arise, in particular with respect to the so called“geo-effect”, which is the impact of space weather ingeneral.
There are two principal goals of the proposed study
group. Firstly, to connect the “geodetic” ionosphereresearch with solar-terrestrial physics, in order to consider
the complete cause-effect-chain. Second, the above
mentioned “geo-effect” has to be investigated in detail,which is an important aspect, because modern society
depends to a great extent on technology, i.e. technologythat can be disturbed, that can be harmed or that even canbe destroyed by extreme space weather events.
Objectives
x improvements and enlargements of ionosphere models(including scintillations)

Structures for the Period 2015-20191074

x geodetic contributions to investigate the impact of space
weather/the ionosphere (extreme events) on satellite
motionx geodetic contributions to investigate the impact of space
weather/theionosphere(extreme
events)oncommunication
x investigations of the impact of space weather/theionosphere (extreme events) on remote sensing products
x investigations of the impact of space weather/theionosphere (extreme events) on terrestrial technicalinfrastructure (metallic networks, power grids)
x “geodetic observations” of currents (ring current,electrojets)
Program of activities
x the maintaining of a website for general information as
well as for internal exchange of data sets and results
x organization of a workshop w.r.t. space weather andgeo-effects
x publication of important findings
Members
Klaus Börger (Germany), Chair
Mahmut Onur Karsioglu (Turkey), Vice-chair
Michael Schmidt (Germany)
Jürgen Matzka (Germany)
Barbara Görres (Germany)
George Zhizhao Liu (Hong Kong, China)
Ehsan Forootan (Germany)
Johannes Hinrichs (Germany)

JSG 0.21: Geophysical modelling of time variations indeformation and gravity(Affiliation: Commissions 2 and 3)
Chair: Y. Tanaka (Japan)
Introduction
In recent years, observational accuracy of ground-,satellite- and space-geodetic techniques has significantly
improved which enables us to monitor temporal variations
in surface deformations and gravity over various space andtime scales. These variations are related to a wide range of
surface and internal Earth’s processes, including thedeformational response to glacial loading, solid earth andocean tides, atmospheric and non-tidal ocean loadings,
hydrological phenomena, earthquake and volcano activity,
tsunamis from seismic to GIA-process frequencies. Theinterpretation of such high-accuracy observational data,
more advanced theories are required in order to describe
the individual processes and to quantify the individual
signals in the geodetic data. To facilitate this, interactions
between geophysical modelling and data modelling is
mandatory.
Objectives
x Development of 1-D, 2-D, and 3-D elastic/anelastic
Earth models for simulating the individual processes
causing variations in deformation and gravity.
x Development of phenomenological or dynamic theories
to treat deformation and gravity variations which cannot
be described by the above earth models (e.g., hydrology,
cryosphere, poroelasticity) and consideration of such
effects in the above earth models.
x Theoretical study to reveal the mechanisms of theindividual processes.
x Comparative study of theoretical methods using theexisting codes.
x Forward and inverse modelling of deformation andgravity variations using observational data.
x Development of observational data analysis methods toextract the individual geophysical signals.
Program of activities
x To launch an e-mail list to share information concerning
research results and to interchange ideas for solving
related problems.
x To open a web page to share publication lists and its update.

Inter-Commission Committee on Theory (ICCT)x To hold an international workshop focusing on theabove research theme.
x To have sessions at international meetings (EGU, AGU,
IAG, etc.) as needed.

1075

JSG 0.22: Definition of next generation terrestrialreference frames(Affiliation: Commission 1 and GGOS)
Chair: C. Kotsakis (Greece)

Members
Yoshiyuki Tanaka (Japan), ChairDavid Al-Attar (UK)
Johannes Bouman (Germany)
Taco Broerse (The Netherlands)
Gabriele Cambiotti (Italy)
Benjamin Fong Chao (China-Taipei)
Jose Fernandez (Spain)
Luce Fleitout (France)
Guangyu Fu (China)
Pablo Jose Gonzales (UK)Shin-Chan Han (Australia)
Erik Ivins (USA)
Volker Klemann (Germany)Zdeněk Martinec (Ireland)
Masao Nakada (Japan)
Jun'ichi Okuno (Japan)
Riccardo Riva (The Netherlands)
Giorgio Spada (Italy)Peter Vajda (Slovak Republic)
Wouter van der Wal (The Netherlands)

Introduction
A Terrestrial Reference Frame (TRF) is required formeasuring the Earth orientation in space, for positioning
objects at the Earth’s surface as well as satellites in orbit
around the Earth, and for the analysis of geophysicalprocesses and their spatiotemporal variations. TRFs are
currently constructed by sets of tri-dimensional coordinatesof ground stations, which implicitly realize the threeorthogonal axes of the corresponding frame. To accountfor Earth’s deformations, these coordinates have beencommonly modelled as piece-wise linear functions of time
which are estimated from space geodetic data undervarious processing strategies, resulting to the usual type of
geodetic frame solutions in terms of station coordinates (atsome reference epoch) and constant velocities. Most
recently, post-seismic deformation has been added as wellin geodetic frame solutions. The requirements of the Earthscience community for the accuracy level of such secular
TRFs for present-day applications are in the order of 1 mm
and 0.1 mm/year, which is not generally achievable atpresent. Improvements in data analysis models, coordinate
variation models, optimal estimation procedures and datum
definition choices (e.g. NNR conditions) should still be
investigated in order to enhance the present positioning
accuracy under the “linear” TRF framework.
Moreover, the consideration of seasonal changes in thestation positions due to the effect of geophysical loading
signals and other complex tectonic motions has created an
additional interest towards the development of “nonlinear” TRFs aiming to provide highly accurate coordinatesof the quasi-instantaneous positions in a global network.
This approach overcomes the limitation of global secular
frames which model the average positions over a long timespan, yet it creates significant new challenges and open
problems that need to be resolved to meet the
aforementioned accuracy requirements.
The above considerations provide the motivation forthis JSG whose work will be focused to studying andimproving the current approaches for the definition andrealization of global TRFs from space geodetic data, in
support of Earth mapping and monitoring applications. The
principal aim is to identify the major issues causing thecurrent internal/external accuracy limitations in global
TRF solutions, and to investigate ways to overcome themeither in the linear or the non-linear modeling framework.

Structures for the Period 2015-2019

1076

Objectives

Program of activities

x To review and compare from the theoretical point ofview the current approaches for the definition andrealization of global TRFs, including data reduction
strategies and frame estimation methodologies.
x To evaluate the distortion caused by hidden datum
information within the unconstrained normal equations(NEQs) to combination solutions by the “minimum
constraints” approach, and to develop efficient tools
enforcing the appropriate rank deficiency in input NEQs
when computing TRF solutions.
x To study the role of the 7/14-parameter Helmert
transformation model in handling non-linear (nonsecular) global frames, as well as to investigate theframe transformation problem in the presence ofmodeled seasonal variations in the respective
coordinates.
x To study theoretical and numerical aspects of thestacking problem, both at the NEQ level and at thecoordinate time-series level, with unknown non-linear
seasonal terms when estimating a global frame fromspace geodetic data.
x To compare the aforementioned methodology with otheralternative approaches in non-linear frame modeling,such as the computation of high-rate time series ofglobal TRFs.
x To investigate the modeling choices for the datum
definition in global TRFs with particular emphasis on
the frame orientation and the different types of no-netrotation (NNR) conditions.

x Active participation at major geodetic meetings,
promotion of related sessions at international scientificsymposia and publication of important findings related
to the JSG objectives.
x Proposal for a state-of-art review paper in global frame
theory, realization methodologies and open problems,co-authored by the JSG members.
x Organize a related session at the forthcoming HotineMarussi Symposium.
x Launching a web page with emphasis on exchange of
research ideas, recent results, updated bibliographic listof references and relevant publications from otherdisciplines.
Members
Christopher Kotsakis (Greece), Chair
Zuheir Altamimi (France)
Michael Bevis (USA)Mathis Bloßfeld (Germany)
David Coulot (France)
Athanasios Dermanis (Greece)
Richard Gross (USA)Tom Herring (USA)Michael Schindelegger (Austria)
Manuela Seitz (Germany)
Krzysztof Sośnica (Poland)Communication and Outreach Branch (COB)

1077

Communication and Outreach Branch (COB)
President: József Ádám (Hungary)
Secretary: Szabolcs Rózsa (Hungary)
http://www.iag-aig.org

Development
The Communication and Outreach Branch (COB) was
created by the IAG Council at its special meeting in Budapest, 7 September 2001. A Call for Participation was
issued by the IAG Central Bureau (CB) to fill this position.
Two offers were received to host the COB. The offer of the
Hungarian Academy of Sciences (HAS) / University ofTechnology and Economics (BME) was elected by the
Executive Committee (EC) at its meeting in Nice, 11 April,
2003. The IAG Council at the 23rd IUGG/IAG General
Assembly (Sapporo, Japan, 30 June-11 July, 2003) has
confirmed this election. Thus the COB started its activities
in July 2003, and in the period of 2015-2019 will be thefourth term in the operation of the COB by the HAS/BME.
The Communication and Outreach Branch is one of thecomponents of the Association. According to the new
Statutes (§5) of the IAG, the COB is the office responsible
for the promotional activities of the IAG and thecommunication with its members.

Terms of Reference
According to §18 of the new By-laws of the IAG:(a) The function of the Communication and OutreachBranch is to provide the Association with communication, educational/public information and outreachlinks to the membership, to other scientific Associations and to the world as a whole.
(b) The responsibilities of the Communication and Outreach Branch shall include the following tasks:(i) Promote the recognition and usefulness of geodesy
in general and IAG in particular.
(ii) Publications (newsletters).

(iii) Membership development.
(iv) General information service and outreach.
c) The Communication and Outreach Branch shall also
assist the IAG General Secretary, in the following tasks:(i) Maintenance of the IAG website.
(ii) Setting up Association schools.
(iii) Setting up meetings and conferences.
d) Major decisions related to the operations of the COB
shall be made by a Steering Committee consisting of
the following voting members:(i) Communication and Outreach Branch President.
(ii) IAG Secretary General.
(iii) Editor-in-Chief of the Journal of Geodesy.
(iv) Editor-in-Chief of the IAG Symposia Series.
(v) Up to 5 other members appointed by the Executive
Committee on recommendation of the President of
the Communication and Outreach Branch.

Program of Activities
According to the new modernised structure of the IAG, theindividual membership has been introduced in addition to
the traditional National Members. However the individual
membership requires a more commercial, member oriented
operation of the Association. The main purpose of the
COB is to promote communication and interaction among
all of its members and to facilitate the work of IAG in
general. Therefore the COB will be a permanent IAG officefor publication, publicity and visibility of the Association.
The planned activities of the COB will be split into two
main groups:a) Communicational activities;b) Membership developments and promotional activities
which enable the growth of the IAG itself.

Structures for the Period 2015-20191078

One of the major tasks of the COB is to create thechannels of the communication within the Association.
Our intention is to make a simple, structured way ofcommunication using various information technologies(IT). The communication of the IAG will be done using thefollowing channels:
x The official IAG website (see the chapter IAG on theInternet in this issue);x Publication of the IAG Newsletters and Geodesist’s
Handbook in cooperation with the IAG Office.
The official IAG website acts on one hand as the mostimportant interface to the outside community, and on theother hand it is the first pillar of the communicational
infrastructure of the Association. Therefore the content of
the website is defined to support both roles.
The server operating in the IAG COB, handles mailinglists, which will be the major source of information for themembers. The members get all of the announcements andNewsletters via e-mail. Our intention is to operate many
mailing lists. Issues for creating/maintaining user
database/lists for advertising, circular e-mails, surveys, etc
are as follows:
x Users can already register themselves by giving contact
information and topics of interest (e.g. GPS, Gravity
Field, Reference Frames, etc.) for notification;
x Registration should be entirely web-based using confirmation e-mails;
x Users can access/update/delete their personal contact
information with username and password;
x Privacy statement is necessary for keeping personal data
confident;
x Several statistics for geographical user distribution canbe shown in simple charts on the IAG website;x Benefits should be clearly stated to be on the user list.
The electronic version of the IAG Newsletter ispublished monthly. It has a unique logo which is a)
unmistakable and unambiguous, b) easy to read andperceive even when printed in black/white, and c) simply
designed and reproduces to any size. It is available indifferent formats for distribution: (i) plain text for e-mail,(ii) HTML for website, and (iii) PDF for e-mail anddownloading from website. Visitors have following
options regarding the distribution of the IAG Newsletter:x View the Newsletter online or download it directly;
x Browse/view/download past issues in the Newsletterarchive.
A selection of the Newsletter articles is published in the
Journal of Geodesy.
The membership developments and promotional
activities are further our one of the most important tasks.
The COB focuses not only on increasing the number ofmembers in the IAG, but also on providing science

information service to the members. For the membershipdevelopments a Membership Application Form (MAF) was
designed in the previous period and it is put on the IAG
website. In the front-page of our website, there is an indication to download the Membership Application Form.
The major channels of promotional activities are the
IAG website, and the mailing lists. Some brochures andleaflets are printed, which
x Introduce the IAG to the global community;
x Emphasize the mission statement of IAG; andx Describe the advantages of being an IAG member.
Our intention is that these brochures should be available atevery conference organized and/or sponsored by IAG.
Therefore the COB should also represent IAG at all major
meeting (including not only IUGG General Assemblies,
IAG Scientific Assemblies, AGU and EGS meetings, butalso at IAG-sponsored meetings) with different IAG materials (brochures, etc). These brochures can be downloaded
from the IAG website (www.iag-aig.org).

Steering Committee
The COB has a Steering Committee (SC) with thefollowing members:
Ex officio voting members:- COB President: József Ádám (Hungary)- IAG Secretary General: Herman Drewes (Germany)- Editor-in-Chief of the JoG: Jürgen Kusche (Germany)*- Editor-in-Chief of the IAG Symposia Series: Jeff
Freymueller (USA)*
Other voting members:- Szabolcs Rózsa (Hungary), COB Secretary, IAG
Webmaster- Gyula Tóth (Hungary), Editor of the IAG Newsletter*- Franz Kuglitsch (Germany), IAG Assistant Secretary
General- Allison B. Craddock (USA), GGOS, IGS* The Editors may be substituted by the respective
Assistant Editors
Permanent Guests (non-voting):- Harald Schuh (Germany), IAG President- Zuheir Altamimi (France), IAG Vice-President- Chris Rizos (Australia), IAG Immediate-Past President
The COB operates an office at
Department of Geodesy and Surveying
Budapest University of Technology and Economics
P.O. Box 91
H-1521 Budapest, Hungary.
Phone: +36-1-463 3222/3213, Fax: +36-1-463 3192.

Global Geodetic Observing System (GGOS)

1079

Global Geodetic Observing System (GGOS)
Chair of the GGOS Coordinating Board: H. Kutterer (Germany)
Vice-Chair of the GGOS Coordinating Board: R. Neilan (USA)
http://www.ggos.org

GGOS Terms of Reference
Preamble
The proposal for the Global Geodetic Observing System(GGOS) was developed by the GGOS planning groupbetween 2001 and 2003 according to the Bylaws of theInternational Association of Geodesy (IAG). The proposal
was accepted by the IAG Executive Committee and the
IAG Council at their meetings during the XXIII IUGG
General Assembly in Sapporo in July 2003. GGOS was
there endorsed by the IUGG through Resolution No. 3.
Changes in the IAG Bylaws in 2007 resulted in GGOS
being recognized as an integral component of IAG alongwith Services and Commissions. This transformed thestatus of GGOS from that of an IAG Project to an IAG
component. Specific to the GGOS are IAG Bylaws §1(d)and §15. During 2013Ǧ2015, revisions to the structure of
GGOS were discussed leading to the Terms of Reference
2015, primarily to streamline its organizational structure.
According to the IAG Bylaws §1(d) “The Global Geodetic
Observing System works with the IAG components toprovide the geodetic infrastructure necessary formonitoring the Earth system and global change research”.

x To provide the global geodetic frame of reference that is
the fundamental backbone for measuring andconsistently interpreting key global change processes
and for many other scientific and societal applications.
x To benefit science and society by providing thefoundation upon which advances in Earth and planetarysystem science and applications are built.
We live on a dynamic planet in constant motion that
requires long-term continuous quantification of its changes
in a truly stable frame of reference. GGOS and its related
research and services will address the relevant scienceissues related to geodesy and geodynamics in the 21st
century, but also issues relevant to society (global risk
management, geo-hazards, natural resources, climatechange, severe storm forecasting, sea level estimations andocean forecasting, space weather, and others). It is anambitious program of a dimension that goes beyond IAG,
requiring a strong cooperation within the geodetic,
geodynamic and geophysical communities, and externally,
to related endeavours and communities. GGOS will
provide this integration at the highest level, in service tothe technical community and society as a whole.

GGOS Strategic Direction

GGOS Vision

Overarching Strategic Areas of GGOS

Advancing our understanding of the dynamic Earth system
by quantifying our planet’s changes in space and time.

The GGOS Goals, Objectives, and Outcomes are built
around four strategic areas that are directly attributable tothe established GGOS goals. These areas were establishedin the 2011 Strategic Plan, and continue to be relevant tothe activities and future efforts of GGOS in subsequent
strategic plans. The strategies are related to each goal, but
are overarching in nature – just as each goal acts in supportof other goals, each strategy has a role in all of the goals.

GGOS Mission
x To provide the observations needed to monitor, map,and understand changes in the Earth’s shape, rotation,and mass distribution.

Structures for the Period 2015-20191080

1. Geodetic Information and Expertise (intangible assets):
GGOS outcomes will support the development andmaintenance of organizational intangible assets,
including geodetic information and expertise. The
development of this strategic focus area will benefit allother goals and objectives.
2. Global Geodetic Infrastructure (advocacy for, andsustenance of, tangible assets):
Development of, advocacy for, and maintenance ofexisting global geodetic infrastructure is in direct
support of each GGOS goal
3. Services, Standardization, and Support (internal andexternal coordination):
Optimal coordination, support, and utilization of IAG
services, as well as leveraging existing IAG resources,
are critical to the progress of all GGOS goals andobjectives.
4. Communication, Education, and Outreach (public
relations, external education and outreach, internal
continuing education and training):
Marketing, outreach, and engagement are criticalelements for sustaining the GGOS organizational fabric.
IAG Services, Commissions, and Inter-Commission
Committees in Support of GGOS
In order to accomplish its mission and goals, GGOS
depends on the IAG Services, Commissions and InterCommission Committees. The Services provide theinfrastructure and products on which all contributions of
GGOS are based. The IAG Commissions and InterCommission Committees provide expertise and support forthe scientific development within GGOS. In summary,
GGOS is IAG's central interface to the scientificcommunity and to society in general.
IAG is a Participating Organization of the Group on
Earth Observations (GEO). GGOS acts on behalf of the
IAG in GEO and actively contributes to the Global Earth
Observation System of Systems (GEOSS).
GGOS addresses relevant science issues related togeodesy and geodynamics in the 21st century, but also
issues relevant to society (including but not limited to
management of natural resources, natural hazards, global
risk management, monitoring of climate change andrelated phenomena, ocean forecasting and sea levelprojections, early warning of severe storms, tsunamis,
other hazards, and space weather). It is an ambitious
program of a dimension that goes beyond IAG, requiring astrong cooperation within the geodetic and Earth science
communities, and externally, to related endeavours andcommunities.

The GGOS 2020 Book (Global Geodetic Observing
System: Meeting the Requirements of a Global Society on
an Changing Planet in 2020", H.-P. Plag and M. Pearlman(editors) , Springer, 2009) serves as the initial basis for the
implementation of GGOS, as the observing system of IAG,
and is used to derive work plans based on its
recommendations.

GGOS Structure
Overview of Key GGOS Elements
The organizational structure of GGOS is comprised of thefollowing key elements which are depicted in Fig. 1:
x GGOS Consortium – is the collective voice for all
GGOS matters. It will meet annually as possible. The
elements of GGOS have the flexibility to determine anddesignate two representatives to the GGOS Consortium
as each (Service, Commission and Inter-Commission
Committees, or other entity) decides. The Consortium is
to be comprised of the Chairs of Services and the
Directors of the Service’s central offices or Central
Bureaus; Presidents and ViceǦPresidents of IAG
Commissions, Inter-Commission Committees, and otherentities essential to GGOS as determined by theConsortium. The GGOS Consortium is the nominatingand electing body of elected positions on the GGOS
Coordinating Board as noted below. The Chair of
GGOS shall act as the Chair of the GGOS Consortium.
x GGOS Coordinating Board – is the central oversightand decision-making body of GGOS, and represents the
IAG Services, Commissions, Inter-Commission
Committees, and other entities. For a comprehensive listof represented entities, see below.
x GGOS Executive Committee – serves at the direction of
the Coordinating Board to accomplish dayǦtoǦday
activities of GGOS tasks.
x GGOS Science Panel – advises and provides
recommendations relating to the scientific content of the
GGOS 2020 book to the Coordinating Board; andrepresents the geodetic and geoscience community at
GGOS meetings. GGOS Coordinating Office –coordinates the work within GGOS and supports the
Chairs, the Executive Committee and the Coordinating
Board.
x GGOS Bureau of Products and Standards – tracks,
reviews, examines, evaluates all actual standards,
constants, resolutions and products adopted by IAG or
its components and recommends their further use or
proposes the necessary updates.

Global Geodetic Observing System (GGOS)

1081

x GGOS Bureau of Networks and Observations –develops a strategy to design, integrate and maintain thefundamental
geodetic
infrastructure
includingcommunication and data flow; monitors the status of the
networks and advocates for implementation of core andother co-located network sites and improved network
performance.
x GGOS Committees, Working Groups and Focus Areas(formerly known as Themes) – address overarchingissues common to several or all IAG components, andare a mechanism to bring the various activities of theServices,
Commissions
andInter-Commission
Committees together, or to link GGOS to externalorganizations. Focus Areas are cross-disciplinary andaddress specific focus areas where GGOS contributors
work together to address broader and critical issues.

Fig. 1 GGOS organizational chart 2016

Fundamental Supporting Elements of GGOS
x IAG promotes scientific cooperation and research ingeodesy on a global scale and contributes to it throughits various research bodies. GGOS is the Observing
System of the IAG.
x IAG Services, Commissions and InterǦCommission
Committees are the fundamental supporting elements ofGGOS.

x GGOS Inter-Agency Committee (GIAC) – a forum thatseeks to generate a unified voice to communicate with
Governments and Intergovernmental organizations(GEO, UN bodies) in all matters of global and regional
spatial reference frames and research and applications.

Structures for the Period 2015-2019

1082

Details of the Structure of GGOS
GGOS Consortium
The GGOS Consortium is the voice and essentially thelarge steering committee of GGOS. It reviews the GGOS
progress, activities, and nominates and votes for the
candidates for the elected positions on the GGOS
Coordinating Board.
The GGOS Consortium is comprised of two designatedrepresentatives from each IAG component. The Chair of an
IAG Service Governing or Directing Board, and the
Director of the Central Bureau or Coordinating Office, as
well as Commission and Inter-Commission Committee
Presidents and Vice Presidents may be those designatedmembers. However, no person may represent two or morecomponents, and no one may have more than one vote.
The presiding Chair of the GGOS is, by default, the Chairof the Consortium. GGOS Consortium decisions are basedon consensus. Decisions requiring a vote are decided bysimple majority of the votes cast. The quorum is met whenat least fifty percent of members are present, but electronic
voting is acceptable provided a quorum responds.
The Consortium is the electing body for the GGOS
Coordinating Board. The Consortium will meet at least
once a year.
GGOS Coordinating Board
The Coordinating Board (CB) is the decision making bodyof GGOS. Decisions are based upon consensus, wheneverpossible. Decisions requiring a vote are decided by simple
majority of the votes cast. The quorum for a valid vote isparticipation of fifty percent of the voting members of theCoordinating Board. Votes may be held in person atmeetings, or by appropriate electronic means at thediscretion of the GGOS Executive Committee. The
Coordinating Board will meet at least once yearly,
although twice yearly is preferable.
Coordinating Board Members
Voting Coordinating Board members:
GGOS Chair (votes in case of a tie)
1
GGOS Vice-Chair
1
Chair of GGOS Science Panel (ex-officio)
1
Director of Coordinating Office (ex-officio)
1
Directors of GGOS Bureaus (ex-officio)
2
IAG President or designated representative (ex-officio) 1
Service Representatives (elected by the Consortium)
4
IAG Commission, and Inter-Commission Committee
Representatives (elected by the Consortium)
2
Members-at-Large (elected by the GGOS CB)
3
Total voting members
16

Non-Voting Coordinating Board Members:
Chairs of GGOS Committees / Working Groups(ex-officio)
Focus Area Leads (ex-officio)
GGOS Web and Social Media Manager (ex-officio)
Immediate Past Chair of the GGOS CB (ex-officio)
Representative of the GIAC (ex-officio)

n
3
1
1
1

Approved observers may also participate at the discretionof the Chair.
Chair
The chair of the GGOS Coordinating Board is determinedaccording to the IAG Bylaws [IAG Bylaw 15(d): “TheGGOS Chair is appointed by the IAG Executive committee
in consultation with the GGOS Coordinating Board for one
four-year period, which may be renewed once.”]. The
Chair of the GGOS CB is, by default, also known as the
GGOS Chair.
Members-at-Large
Members-at-Large are invited to join the Coordinating
Board in order to provide balance in representation ofgeographical regions or unique capabilities. The Chair,with the assistance of the Coordinating Office, appoints an
Election Committee to organize the voting process and toensure availability of the nominated candidates. The
Election Committee then presents the final list ofMembers-at-Large candidates to the CB for a vote.
Appointment of the Chair and Election of Coordinating
Board Members
The process for elections to the GGOS Coordinating Board
will follow the fourǦyear IAG General Assembly, whichtakes place during the IUGG General Assembly (see IAG
Bylaws for more detail). Candidates nominated to serve on
the Coordinating Board must be members of the GGOS
Consortium. The CB elects the Vice-Chair of the GGOS
CB by a vote. However, the GGOS Chair is appointed by
the IAG Executive Committee in consultation with the
GGOS Coordinating Board.
GGOS Executive Committee
The GGOS Executive Committee (EC) is comprised of thefollowing members:
GGOS Chair
1
GGOS Vice-Chair
1
Director of Coordinating Office1
Directors of the Bureaus
2
Members of the CB selected for EC membership
2
Total
7

Global Geodetic Observing System (GGOS)

Every other year, the GGOS Chair submits a list of hisor her candidates for the two open member spaces to the
CB for approval. These candidates must be voting
members of the CB in order to be nominated to the EC.
The GGOS Chair may nominate an EC member to serve
as primary GGOS representative to all GGOS
stakeholders, including but not limited to: IAG and its
Services, CEOS, GEO, space agencies, the United Nations,
university partners, and national mapping agencies. This
position will be filled by the GGOS Vice-Chair or other
EC member, depending on Chair nomination and CB
approval. A secondary or stakeholder-specific GGOS
representative may also be nominated, if necessary.
The Immediate Past Chair of GGOS, the Chair of the
GGOS Science Panel, and the President of IAG are allpermanently invited guests at meetings of the Executive
Committee. Other observers may be invited to attend EC
meetings (or teleconferences) as needed.
GGOS Science Panel
The GGOS Science Panel is an independent andmultiǦdisciplinary advisory board that provides scientificsupport and guidance to the GGOS steering andcoordination entities as requested. This support may
include organization of relevant scientific sessions atconferences, workshops, and other events.
The IAG Commissions and Inter-Commission Committees
each nominate two candidates to the Science Panel subject
to approval by the CB. The CB may appoint additional
Members-at-Large to the Science Panel in order to provide
balance in representation of geographical regions or uniquecapabilities. The immediate past Chair of the Science Panelis a Member of the Science Panel. The Science Panel will
elect its own Chair to be approved by the CB.
IAG Services, Commissions and InterǦǦCommission
Committees

GGOS works with these IAG components to provide thegeodetic infrastructure necessary for monitoring the Earthsystem and global change research. GGOS respects thebylaws and terms of reference for these essential
components. GGOS is built on the existing IAG Services
and their products. GGOS is not taking over tasks of theexisting, and well working IAG Services. GGOS will
provide a framework for existing or future Services andstrive to ensure their long-term stability.
GGOS Committees, Working Groups and Focus Areas
GGOS Committees and Working Groups (WG) areestablished by the Coordinating Board as needed. Working
Groups are set up for one 4-year period, Committees for1083

longer periods of time. The Coordinating Board appoints
their chairs and prepares and approves their charters. The
members of Committees and WGs are nominated by theirchairs and confirmed by the Coordinating Board.
Focus Areas are crossǦdisciplinary focus areas andmeant to consider gaps and needed future products. The
GGOS CB approves the Focus Areas. The CB appoints
theme leads. Focus Areas outline their purpose andpropose a work plan to address any noted gap to beaddressed by the particular theme focus.
GGOS Coordinating Office
The GGOS Coordinating Office (CO) performs thedayǦtoǦday activities in support of GGOS, the Executive
Committee, the Coordinating Board, and the Science
Panel, and ensures coordination of the activities of thevarious components. The CO ensures information flow,
maintains documentation of the GGOS activities, andmanages specific assistance functions that enhance thecoordination across all areas of GGOS, includinginterǦservices coordination and support for workshops. The
CO in its longǦterm coordination role ensures that the
GGOS components contribute to GGOS in a consistent andcontinuous manner. The CO also maintains, manages, andcoordinates the GGOS web presence and outreach.
Bureau of Products and Standards
The Bureau of Products and Standards keeps track of thestrict observations of adopted geodetic standards,
standardized units, fundamental physical constants,
resolutions and conventions in all official products
provided by the geodetic community. It reviews, examinesand evaluates all actual standards, constants, resolutions
and conventions adopted by IAG or its components, andrecommends further use or proposes the necessary updates.
It identifies eventual gaps in standards and products, andinitiates steps to close them with, e.g., resolutions by the
IUGG and/or IAG Councils.
Bureau of Networks and Observations
The Bureau of Networks and Observations develops a
strategy to design, integrate and maintain the fundamental
infrastructure in a sustainable way to satisfy the long-term(10-20 years) requirements identified by the GGOS
Science Panel. Primary emphasis must be on sustaining theinfrastructure needed to maintain the evolving global
reference frames, while at the same time ensuring thebroader support of the scientific applications of thecollected data. Coordinating and implementing the GGOS
co-located station network is a key focus for 2010-2020.

Structures for the Period 2015-2019

1084

GGOS Bureau of Networks and Observations

Objectives

Director: Michael Pearlman (USA)Members: Erricos C. Pavlis (USA), Carey Noll (USA),
Hayo Hase (Germany), Chopo Ma (USA), Giuseppe
Bianco (Italy), Wu Bin (China), Ruth Neilan (USA), Steve
Fisher (USA), Jérôme Saunier (France), Pascale Ferrage(France), Riccardo Barzaghi (Italy), Mark Tamisiea (UK),
Tilo Schöne (Germany), Daniela Thaller (Germany),
Richard Gross (USA), Bernd Richter (Germany), Jürgen
Müller (Germany), Roland Pail (Germany), Sten
Bergstrand (Sweden), John Dawson (Australia).

The Objectives of the Bureau are to:x Provide a forum for the Services, committees andworking groups to share and discuss plans, progress,
and issues, and to develop and monitor multi-entity
efforts to address GGOS requirements;
x Actively promote, design and coordinate the global
geodetic ground-based infrastructure needed to meetrequirements for Earth science and societal benefits;x Lead efforts for the integration of various groundobservation networks under the GGOS umbrella; andx Coordinate the international geodetic Services’
activities that are the main source of key data andproducts needed to realize stable global reference
frames and other data products essential to studychanges in the dynamic Earth System and characterize
key Earth science parameters for the benefit of society.

Introduction and Background
The Bureau of Networks and Observations (BN&O) is aredefinition of the GGOS Bureau for Networks andCommunication (BN&C) which was established in 2003 todevelop a strategy to design, integrate, implement andmaintain the fundamental geodetic network of co-locatedinstruments (VLBI, SLR, GNSS, and DORIS) and the
supporting infrastructure in a sustainable way to satisfy thelong-term (10 - 20 years) GGOS requirements (GGOS
2020, 2009). The BN&O advocates for implementation of
the global space geodesy network of sufficient capability
and geographic coverage to achieve data products essential
for GGOS and serves as a coordinating point for theServices to meet, discuss status and plans, and examine
common paths for meeting GGOS requirements.
Committees and working groups are included in the
Bureau in recognition of their synergistic role with Bureau
activities.
The new Bureau has been restructured to:x Expand its role with the inclusion of other than thegeometric Services and techniques (gravity, tide gauges,etc.);x Improve communication and information exchange andcoordination with the space missions;x Include simulation and network analysis activities;
x Include the site-tie component at co-located sites; andx Include the meta-data development activities.
These expanded activities are being implemented byincorporating the non-geometric measurement Services
and the pertinent GGOS committees (Missions,
Simulations, Data and Information Systems) and working
groups (IERS Working Group on Survey and Co-location)that have a very synergistic role with the Bureau. The
Bureau plays a very fundamental role in the GGOS Focus
areas: Geohazards Monitoring, Sea Level Monitoring, andUnified Height System.

Tasks
In its role to support the Services and better serve theusers, the activities of the Bureau are:x Advocate for implementation of the global space
geodesy network of sufficient capability to achieve data
products essential for GGOS;– Update the Bureau website for public use;
– Provide status and plans on network developmentfrom the Bureaus;– Continue to oversee the Bureau’s “Call for
Participation in the Global Geodetic Core Network:
Foundation for Monitoring the Earth System” andwork with new groups interested in participating;– Meet with interested parties and encourage
partnerships.
x Provide a forum for the Services, committees andworking groups to meet, discuss status and plans, andexamine common interests and requirements;
x Maintain and update the “Site Requirements for GGOS
Core Sites” document;
x Monitor and project the status and evolution of the
GGOS space geodesy network in terms of location andperformance (with the IAG Services);x Coordinate the effort of the Services to implement
procedures to provide test-based estimates of their data
quality and report;
x Facilitate efforts to integrate relevant parameters fromother ground networks (gravity field, tide gauges, etc.)
into the GGOS network to support GGOS requirements
including the reference frame, a unified height system,
etc.; advocate for installation of GNSS receivers at
appropriate tide gauges;

Global Geodetic Observing System (GGOS)

x Support the technique Services on the promotion ofrecommended
technologies/configurations
andprocedures in the establishment of new sites and theupgrading of current sites, and in the evaluation of
performance of new stations and new capabilities after
they become operational;
The evolution of the networks will be a long-term
endeavor, but the evolution in the networks, including boththe core and participating co-location sites, newtechnology and legacy sites, and the associated modelingand analyses, will provide steady and very usefulimprovements in the data products. The evolving data anddata products will be a major driver for developing andvalidating the new models and analysis techniques.

Committees of the Bureau of Networks andObservations
BNO C1: Committee on Performance Simulations andArchitectural Trade-Offs(joint with IAG Sub-Commission 1.1)
Chair: Daniela Thaller (Germany)
Vice-Chair: Richard Gross (USA)1085

 The full range of existing ground and space assets:- GNSS assets (ground and space)- SLR (beyond Lageos-1 and -2) including ranging to
GNSS satellites;- LLR assets- VLBI assets including tracking of GNSS satellites;- Co-located assets in space (e.g. GRACE, OSTM)- Mixture of existing legacy stations and simulated
next generation stations- Improved GNSS antenna calibrations and clock
estimation strategies (GNSS alone or when in
combination with SLR, VLBI, and DORIS)
 Anticipated improved performance of current systems:- Simulate impact of upgrading existing stations andtheir procedures- Simulate impact of additional ground surveys at colocation sites (site ties) Potential future space assets:- Co-locate all four techniques in space on a dedicatedsatellite (e.g., GRASP)
Tasks
x Define proper GGOS-related tasks with priorities;
x Develop a plan with tasks and task assignments (taskteams) in concert with the PLATO participants;

Objectives
Project future network capability and examine trade-off
options for station deployment and closure, technology
upgrades, impact of site ties, additional space missions,etc. to maximize the utility of the GGOS assets:
x Use simulation techniques to assess the impact onreference frame products of: network configuration,system performance, technique and technology mix, colocation conditions, site ties, space ties (added
spacecraft, etc.), analysis and modeling techniques, etc.;
x Use and developing improved analysis methods forreference frame products by including all existing data
and available co-locations (i.e., include all satellites anduse all data types on all satellites);x Make recommendations on network configuration andstrategies based on the simulation and trade-off studies.
The PLATO Committee / Working Group has 20+ member
groups working on simulations and data analysis covering
the full range of existing ground and space assets,
including VLBI, SLR, GNSS, and DORIS. The main focus
is how do we use existing resources including co-locationin space with existing and new dedicated satellites to best
support GGOS planning and implementation.
Investigations that are being included in the PLATO
activity include studying the impact of:

At the suggestion of Xavier Collilieux (new chair of IAG
SubǦcommission 1.2, on global reference frame), GGOS
has agreed that the PLATO Committee become a Joint(Sub-Commission 1.2) Working Group between GGOS
and IAG Commission 1, with special interest in studies
related to space coǦlocations.

Structures for the Period 2015-2019

1086

BNO C2: Committee on Data and Information

BNO C3: Committee on Satellite Missions

Chair: Bernd Richter (Germany)
Vice-Chair: Carey Noll (USA)

Chair: Jürgen Müller (Germany)
Vice-Chair: Roland Pail (Germany)

Objectives

Objectives

Develop a metadata strategy for all ground-based
measurement techniques:x Promote the use of metadata standards and conventions
and recommend implementations of metadatamanagement in the pursuit of a metadata policy;
x Promote interoperability among participating data
centers with other databases and services;x Develop strategies to protect the intellectual properties
on data and products;
x Align metadata standards with the GEOSS approachand methodology, interface on data standards with GEO
and ICSU.
GGOS is seeking a metadata schema that can be used by
its elements for standardized metadata communication,archiving, and retrieval. First applications would be theautomated distribution of up-to-date station configurationand operational information, data archives and catalogues,
and procedures and central bureau communication. One
particular plan of great interest is a site metadata schema
underway within the IGS Data Center Working Group.
This work is being done in collaboration with the IGS,UNAVCO, SIO, CDDIS, and other GNSS data centers.
The current activity is toward a means of exchange of IGS
site log metadata utilizing machine-to-machine methods,
such as XML and web services, but it is expected that thiswill be expanded to the other Services to help manage siterelated metadata and to other data related products andinformation. Schema for the metadata should follow
international standards, like ISO 19xxx or DIF, but should
be extendable for technique-specific information, which
would then be accessible through the GGOS Portal.

Improve coordination and information exchange with themissions for better ground-based network response to
mission requirements and space-segment adequacy for therealization of GGOS goals

Tasks
x Organize meetings to address a GGOS meta-data plan;x Identify members of all of the involved Services whowill be in the Meta-Data Committee (MDC);x Decide the extent of the information that is necessary to
fulfill catalogue services.
x Develop a proposal with examples of techniques withfilled schema for review by the MDC and the Services;x Develop a spreadsheet of collection-level metadata forreview by the Services;x Identify gravity-affiliated and tide-gauge affiliatedpeople to be added to the MDC;

Goals
Advocating, coordinating, and exchanging information
with satellite missions as part of the GGOS space
infrastructure, for a better ground-based network responseto mission requirements and space-segment adequacy forthe realization of the GGOS goals.
x Assess current and near-future satellite infrastructure,and their compliance with GGOS 2020 goals;
x Support proposals for new mission concepts andadvocate for needed missions;x Interfacing and outreach. These tasks will requireinterfacing with other components of the Bureau;
especially the ground networks component, thesimulation activity (PLATO), as well as the Bureau ofStandards and Products.
Tasks
x Work with the Coordinating Office to set up andmaintain a Satellite Missions Committee section on the
GGOS website;
x Set-up and maintain an inventory/repository (accessible
through the GGOS website and/or portal) of current andnear-future satellite missions relevant to GGOS;
x Evaluate the contribution of current and near termsatellite missions to the GGOS 2020 goals;
x Work with the Focus Areas and the Science Committee
to establish the required mission roles and to identify
the critical gaps in mission infrastructure;x Work with GGOS Executive Committee, Focus Areas,and data product development activities (e.g., ITRF) to
advocate for new missions to support GGOS goals;
x Support the Executive Committee and the Science
Committee in the GGOS Interface with space agencies;x Finalize and publish (outreach) of Science and User
Requirements Document for future gravity field
missions.

Global Geodetic Observing System (GGOS)

GGOS Bureau of Products and Standards
Director: Detlef Angermann (Germany)
Vice-Director: Thomas Gruber (Germany)
Members:
M. Gerstl (Germany), R. Heinkelmann(Germany), U. Hugentobler (Germany), L. Sánchez(Germany), P. Steigenberger (Germany)
Associated Members and Representatives:
J. Ádám (Hungary), F. Barthelmes (Germany), R. Barzaghi(Italy), S. Bonvalot (France), C. Boucher (France), H.
Capdeville (France), M. Craymer (Canada), J. Gipson(USA), T. Herring (USA), L. Hothem (USA), J. Ihde
(Germany), J. Kusche (Germany), F.G. Lemoine (USA),
J.M. Lemoine (France), U. Marti (Switzerland), E. Pavlis(USA), G. Pétit (France), J. Ries (USA), M. Thomas(Germany)
The Bureau of Products and Standards (BPS) is aredefinition of the former Bureau for Standards andConventions (BSC), due to restructuring of the GGOS
organization in 2014. The BPS supports the IAG in its goal
to obtain products of highest possible accuracy,
consistency, and temporal and spatial resolution, whichshould refer to a consistent reference frame, stable overdecades in time. To achieve this important goal, it is afundamental requirement that common standards andconventions are used by all IAG components for the
analysis of the different space geodetic observations. The
BPS also concentrates on the integration of geometric andgravimetric parameters and the development of new
products, required to address important geophysicalquestions and societal needs. Associated with the BPS are
the GGOS Committee “Contributions to Earth System
Modeling” and the Working Groups “ITRS Standards for
ISO TC 211” and “Establishment of the Global Geodetic
Reference Frame (GGRF)” (see below).
Objectives
The key objective of the BPS is to keep track of adopted
geodetic standards and conventions across all IAG
components as a fundamental basis for the generation of
consistent geometric and gravimetric products. The work is
primarily build on the IAG Service activities in the field of
data analysis and combinations. The BPS shall act as
contact and coordinating point regarding homogenizationof standards and IAG/GGOS products. More specificallythe objectives of the BPS may be divided into two major
topics/activities:(1) Standards: This includes the compilation of an
inventory regarding standards, constants, resolutions

1087

and conventions adopted by IAG and its components
and a regular update of such a document. Steps shall be
initiated to close gaps and deficiencies in standards andconventions. Based on the recommendations given inthis inventory priorities should be defined together withdedicated experts in the field. An action plan shall becompiled, including the definition of tasks,
responsibilities and a time schedule. Finally, the BPS
shall propose the adoption of new standards where
necessary and propagate standards and conventions to
the wider scientific community and promote their use.
(2) Products: The BPS shall review and evaluate thepresent status regarding IAG Service products,
including analysis and combination procedures, as wellas accuracy assessment with respect to GGOS
requirements. The Bureau shall initiate steps to identify
user needs and requirements for geodetic products andshall contribute to develop new products based on the
integration of geometric and gravimetric observations.
Activities
x The BPS has compiled an inventory based on thestandards and conventions currently in use by IAG and
its components. The resulting publication “GGOS
Bureau of Products and Standards: Inventory ofStandards and Conventions used for the Generation of
IAG Products” has been reviewed by an external board
and the revised version shall be published in the IAG
Geodesist's Handbook 2016 and on the GGOS web site
as a living document.
x As a major outcome this inventory presents the current
status regarding standards and conventions, identifies
gaps and inconsistencies and provides recommendations
for improvements.
x The transition of the former BSC to the BPS, as aconsequence of restructuring of the GGOS organization,
has been accomplished, including the compilation of an
implementation plan for the BPS and the associated
GGOS components and the revision of its charter.
x The interaction between the BPS and the IAG Services
as well as with other entities involved in standards andconventions has been strengthened by including
representatives of these entities in the BPS board and bycompiling a management plan.
In-progress activities and planned efforts
x Publication of the inventory on standards andconventions in the IAG Geodesist's Handbook and on
the GGOS web site as a living document;

Structures for the Period 2015-2019

1088

x Discussion of recommendations given in the inventory
and compilation of an action plan, including a task
description, specification of responsibilities and timeschedule;
x Evaluation of the current status of IAG/GGOS
products, including an accuracy assessment withrespect to the GGOS requirements;
x Initiation of efforts to identify user needs andrequirements for products that are currently notprovided by the IAG services;x Supporting the GGOS Portal to provide the relevant
information for IAG/GGOS products and contribute topromote geodetic products to the wider user
community.

Committees and Working Groups of the Bureau of
Products and Standards
BPS C1: Committee on Contributions to Earth System
Modeling
Chair: Maik Thomas (Germany)
The GGOS BPS Committee on “Contributions to Earth
System Modeling” was established in 2011 in order topromote the development of an integrated Earth systemmodel that is simultaneously applicable to all geodetic
parameter types, i.e., Earth rotation, gravity and surface
geometry, and observation techniques. Hereby, theworking group contributes to:x a deeper understanding of dynamical processes in the
Earth system integrally reflected in geodetic monitoringdata;
x the establishment of a link between the global timeseries of geodetic parameters delivered by GGOS andrelevant process models;x a consistent integration and interpretation of observed
geodetic parameters derived from various observation
techniques;x the utilization of geodetic observations for theinterdisciplinary scientific community (in cooperation
with GGOS WG on Data and Information Systems).
Objectives
The overall long-term goal is the development of aphysically consistent modular numerical Earth systemmodel for homogeneous processing, interpretation andprediction of geodetic parameters with interfaces allowing
the introduction of constraints provided by geodetic timeseries of global surface processes, rotation parameters andgravity variations. This ultimate goal implicates thefollowing objectives:
x promotion of homogeneous processing of geodetic
monitoring data (de-aliasing, reduction) by processmodeling to improve analysis of geodetic parametersets;
x contributions to the interpretation of geodetic
parameters derived from different observation
techniques by developing strategies to separate
underlying physical processes;
x contributions to the integration of geodetic observations
based on different techniques in order to promotevalidation and consistency tests of various geodetic
products.

Global Geodetic Observing System (GGOS)

Activities
Current activities focus onx the development of consistent standards, parameters,
analysis strategies and formats for all components of theunconstrained modular system model approach;x the identification of relevant interactions among
subsystems and appropriate parameterizations, inparticular to represent the dynamic links between nearsurface fluids and the “solid” Earth;x the development of strategies for the separation of
temporal variations of Earth rotation, gravity and geoid
into individual causative physical processes.
Important in-progress activities and future efforts focus onx feasibility studies for the provision of error estimates ofmodel-based predictions of geodetic quantities (EOP,
deformation, gravity variations);
x application of forward modeling and inversion methods
in order to predict geodetic quantities and to invert
geodetic observations for the underlying causative
processes;x the preparation of numerical algorithms for theassimilation of geodetic products into the numericalsystem model approach in order to provide a tool for
validation and consistency tests of various monitoringproducts.

1089

BPS WG1: Working Group on ITRS Standards for
ISO TC 211
Chair: Claude Boucher (France)
Purpose and Activities
This group was initially established to investigate thestrategy to obtain the adoption by the International
Standardization Organization (ISO) of a standardization
document related to ITRS. Following the initial work doneby the group, a proposal was submitted to ISO by France.
This proposal was a New Work Item Proposal (NWIP)
related to ITRS submitted to the ISO TC 211 on
Geographical information/Geomatics, to which IAG is aliaison. A new NWIP on ITRS has been officially resubmitted by France to ISO TC211 which is presently
under the formal approval channel.
ISO finally decided that a preliminary study
demonstrating the importance of geodetic references atlarge was necessary before going further in the direction of
the initial proposal. A project (19161) was therefore
established within ISO TC211 WG4 and chaired by Claude
Boucher. The project report was finalized in January 2015,
reviewed and finally submitted to WG4 for approval anddecision of further actions.
Recommendations and planned efforts
The report ends with some recommendations:x To develop a standard related to ITRS
x To make further studies about the interest and feasibilityof a standard on vertical referencesx To make similar action for universal identification ofgeodetic stations
x To work to improve geodetic terminology, including
update of existing standards
The GGOS WG was in stand-by during this time. But
assuming that the proposal about ITRS will be ultimately
approved by ISO TC211, it seems opportune to reactivate
this WG with a new mandate, namely drafting the
document related to ITRS, and to update the membershipof this WG.

Structures for the Period 2015-2019

1090

BPS WG2: Establishment of the Global Geodetic
Reference Frame (GGRF)
Chair: Urs Marti (Switzerland)
Terms of Reference
The United Nations General Assembly adopted theresolution on a Global Geodetic Reference Frame for
Sustainable Development (A/RES/69/266) on February 26,
2015.
IAG, as the responsible scientific organization for theestablishment and maintenance of global reference systems
and reference frames establishes a joint working group(JWG) for the realization of this UN resolution under theumbrella of the Bureau of Products and Standards (BPS) of
the Global Geodetic Observing System (GGOS). ThisJWG works together with representatives of IAG
Commissions 1 and 2, the Inter-Commission-Committeeon Theory (ICCT) the International Earth Rotation andReference Systems Service (IERS) and the International
Gravity Field Service (IGFS).
Besides the UN resolution, the following two IAG
resolutions adopted at the IUGG General Assembly 2015
in Prague are the basis of the actions of this working
group:x Resolution 1 for the definition and realization of anInternational Height Reference System (IHRS)
x Resolution 2 for the establishment of a Global Absolute
Gravity Reference System

x Advance the realization of a conventional global
reference gravity field modelx Study the influence of earth orientation parameters andtidal models on the realization of a consistent global
reference frame in geometry, height and gravity
x Study the necessity to replace / update the global
reference system GRS80
x Foster the free exchange of geodetic data and productsx Organize and assist sessions and symposia on the global
reference frame at conferencesx Development of a roadmap for the definition andrealization of a Global Geodetic Reference System
Members
Urs Marti (Switzerland), Chair
Jonas Ågren (Sweden), Commission 2
Detlef Angermann (Germany), Chair of GGOS BPS
Riccardo Barzaghi (Italy), IGFS
Johannes Ihde (Germany), WG on Height Systems
Hansjörg Kutterer (Germany), GGOS Chair
Jaakko Mäkinen (Finland), Tidal Systems
Pavel Novak (Czech Republic), ICCT
Roland Pail (Germany), Commission 2
Nikolaos Pavlis (USA), Global Gravity Field Models
Laura Sánchez (Germany), WG on Height Systems
Harald Schuh (Germany), IAG President
Hartmut Wziontek (Germany), Global Gravity Reference
Network
Corresponding Member

A preparatory paper “Description of the Global Geodetic
Reference Frame” has been prepared by IAG in 2015.
This JWG will work on the establishment and coordinationof the geometric reference frame, the global height system,
the global gravity network and their temporal changes. The
application of Earth orientation parameters and tidal
models and the underlying standard and reference models
has to be brought into consistency.
Objectives and activities
Main objectives and activities of the Working Group are:x Assist GGOS in defining the fundamental network andobserving systems for the realization of the global
geometric reference frame
x Assist the working group for establishing theInternational Height Reference System (IHRS) in therealization
x Integrating and combining the global gravity networkwith other techniques

Gary Johnston (Australia), Commission 1

Global Geodetic Observing System (GGOS)

Focus Area 1: Unified Height System
Chair: Laura Sánchez (Germany)
The objective of Focus Area 1 is the unification of theexisting vertical reference systems around the world. Thisshould be achieved through the definition and realizationof a global vertical reference system thatx supports geometrical (ellipsoidal) and physical (normal,
orthometric, geoidal) heights world-wide withcentimetre precision in a global frame;x enables the unification of all existing physical heightsystems (i.e., all geopotential differences shall bereferred to one and the same reference equipotential
surface with potential W0); andx provides high-accuracy and long-term stability of thevertical coordinates.
A first step towards the establishment of a worldwide
unified (standardized) height system was the release of an
IAG resolution for the definition and realization of anInternational Height Reference System (IHRS) that wasissued during the 2015 IUGG General Assembly. This
resolution outlines the conventions for the definition of the
IHRS in terms of potential parameters: the verticalcoordinates are geopotential numbers referring to an
equipotential surface of the Earth's gravity field realized bya conventional W0 value. At present, the main challenge isthe realization of the IHRS, i.e., the establishment of theInternational Height Reference Frame (IHRF). It is
expected that the IHRF follows the same structure as the
ITRF: a global network with regional and national
densifications, with known geopotential numbers referringto the global IHRS. To guarantee a precise combination ofphysical and geometric parameters and to support thevertical datum unification worldwide, this reference
network should be collocated with fundamental geodetic
observatories, geometrical reference stations, reference tidegauges, local levelling networks, and gravity reference
stations. For this purpose, it will use contributions from all
IAG Commissions, and the available databases, standards
and infrastructure of the IAG/GGOS Services.
Planned activities
x Refinement of standards and conventions for thedefinition and realization of the IHRS, including
unification of standards and conventions that are usedby the geometric and gravity Services of the IAG.
x Develop GGOS products for realizing the IHRS.
x Recommendation for a global vertical reference frame;
i.e. the IHRF.
x Guidelines/procedures for height system unification.

1091

x Development of a registry (metadata) containing theexisting local/regional height systems and theirconnections to the global one.
x Strategies for the maintenance and use in practice of theIHRS.
x Determination and modelling of the temporal changesof the IHRF.
x Update the IHRS definition and realization as needed,based on future improvements in geodetic theory andobservations.
x Servicing the vertical datum needs of other geosciencessuch as, e.g., hydrography and oceanography.
Efforts are currently underway to establish working groups
and processing centres that will focus on one or more of
the action items above. One such group is the alreadyestablished JWG 0.1.2, whose objectives are outlined
below.

Structures for the Period 2015-2019

1092

Joint Working Group of Focus Area 1
JWG 0.1.2: Strategy for the Realization of theInternational Height Reference System(IHRS)(joint with Commissions 1 and 2, ICCT, andthe International Gravity Field Service)
Chair: L. Sánchez (Germany)
The IAG Resolution No. 1 released during the IUGG 2015
General Assembly outlines five conventions for thedefinition of the International Height Reference System(IHRS). The definition is given in terms of potential
parameters: the vertical coordinates are geopotential
numbers (ǦΔWP = CP = W0 Ǧ WP) referring to an
equipotential surface of the Earth's gravity field realized by
the conventional value W0 = 62 636 853.4 m2s-2. The
spatial reference of the position P for the potential WP =W(X) is given by coordinates X of the International
Terrestrial Reference Frame (ITRF). This Resolution also
states that parameters, observations, and data shall be
related to the mean tidal system/mean crust.
At present, the main challenge is the realization of the
IHRS; i.e., the establishment of the International Height
Reference Frame (IHRF): a global network with regionaland national densifications, whose geopotential numbers
referred to the global IHRS are known. According to the
GGOS objectives, the target accuracy of these global
geopotential numbers is 1 x 10-2 m2s-2. In practice, theprecise realization of the IHRS is limited by different
aspects; for instance, there are no unified standards for thedetermination of the potential values WP, the gravity fieldmodelling and the estimation of the position vectors X
follow different conventions, the geodetic infrastructure is
not homogeneously distributed globally, etc. This may
restrict the expected accuracy of 1 x 10-2 m2s-2 to someorders lower (from 10 x 10-2 m2s-2 to 100 x 10-2 m2s-2).
Consequently, the next step is to outline the minimum setof fundamentals needed for a reliable and sustainablerealization of the IHRS.
According to this, the objectives of the JWG 0.0.2 are:x To define the standards and conventions required toestablish an IHRF consistent with the IHRS definition.
A main issue is the high-precise modelling of the timedependent changes of the vertical coordinate (which
also reflect time variations of X and W).
x To formulate minimum requirements for the IHRF
reference stations.
x To develop a strategy for collocation of IHRF reference
stations with existing geometrical reference stations at
different densification levels.

x To identify the geodetic products associated to the IHRF
and to describe the elements to be considered in thecorresponding metadata.
x To review the processing strategies for thedetermination of the potential values WP and torecommend an appropriate computation procedure
based on the accuracy level offered by those strategies.
x To review different approaches for the vertical datum
unification and to provide guidance for the integrationof the existing local height systems into the global
IHRS/IHRF.
x To make a proposal about the organizational andoperational infrastructure required to maintain the IHRF
and to ensure its sustainability.
The main result of this JWG should be a document similar
to the IERS conventions; i.e., a sequence of chapters
describing the different components to be consider for the
precise and sustainable realization of the IHRS and its
practical utilization.
The activities of this JWG are based on the resultspresented by previous work, in particular those of the IAG
Inter-Commission Project 1.2: Vertical Reference Frames(conventions for the definition of World Height System,
2003 – 2011); GGOS Focus Area 1 (former Theme 1):
Unified Height System (action Items for the unification
height reference systems, since 2011); the ESA project“GOCE+ Height System Unification with GOCE” (20112014); the GGOS-BPS (inventory of standards andconventions used for the generation of IAG/GGOS
products, since 2011); and the Joint Working Group 0.1.1
on Vertical Datum Standardisation (2011-2015).
MembersL. Sánchez (Germany), Chair, J. Ågren (Sweden),
M. Amos (New Zealand),D. Avalos (Mexico),
R. Barzaghi (Italy),S. de Freitas (Brazil),
W. Featherstone (Australia), M. Filmer (Australia),
J. Huang (Canada),
G. Liebsch (Germany),
J. Mäkinen (Finland),U. Marti (Switzerland),P. Novak (Czech Republic),
M. Poutanen (Finland),D. Roman (USA),
M. Sideris (Canada),
C. Tocho (Argentina),
M. Véronneau (Canada),
G. Vergos (Greece),
Y. Wang (USA).
Corresponding Members
M. Blossfeld (Germany),
J. Bouman (Germany),
T. Gruber (Germany),
J. Ihde (Germany),
D. Smith (USA),J. Böhm (Austria),
X. Collilieux (France),
B. Heck (Germany),
R. Pail (Germany),
M. Varga (Croatia).

Global Geodetic Observing System (GGOS)

Focus Area 2: Geohazards Monitoring
Chair: J. Labrecque (USA)The Geohazards Monitoring Focus Area of the Global
Geodetic Observing System (GGOS) seeks to apply
geodetic science and technology in support of global andregional resiliency to environmental hazards.
The GGOS and its associated IAG services(International GNSS Service (IGS), International VLBI
Service for Geodesy and Astrometry (IVS), International
DORIS Service (IDS), International Laser Ranging Service(ILRS), International Earth Rotation and Reference
Systems Service (IERS), and International Gravity Field
Service (IGFS)) provide products that serve as thefundamental geodetic references for science, governments,
and industry. The most notable of these products serve as
the basic reference for positioning and timing information
associated with the Global Navigation Satellite Systems(GNSS) including the International Terrestrial Reference
Frame (ITRF), precision orbit and time information andcontinuing scientific and technical advancements to theutilization of the GNSS data.
These and other GGOS products achieved wide global
recognition and acceptance because of their accuracy,
timeliness, and continuing technical improvements. These
are the very qualities needed for effective environmental
warning. In some cases the acceptance of geodetic
applications have been immediate and widespread such as
the application of GNSS to understanding and modeling
earthquake faults.
However, in other cases geodetic technology has
advanced faster than nations can utilize this new capability.
The Geohazards Monitoring Focus Area seeks toaccelerate and guide the acceptance of new geodetic
capability to improve resilience to environmental hazards.
The Focus Area will establish working groups comprisedof GGOS members and the responsible agencies ofparticipating nations. The Focus Area encourages thesharing of intellectual, financial and physical resources asrecommended by the UN-GGIM (http://ggim.un.org ).
As its first initiative, the Geohazards Monitoring Focus
Area has issued a Call for Participation (CfP) to researchscientists, geodetic research groups and national agencies
in support of the implementation of the IUGG 2015
Resolution 4: Global Navigation Satellite System (GNSS)
Augmentation to Tsunami Early Warning Systems(http://www.iugg.org/resolutions/IUGGResolutions2015.p
df). The CfP responders will comprise a working group to
be a catalyst and a motivating force through the definitionof requirements, identification of resources, and theencouragement of international cooperation in the1093

establishment, advancement, and utilization of GNSS for
Tsunami Early Warning, The initiative will have early
focus upon the Indo-Pacific region following the IUGG
2015 Resolution 4.
Future working groups of the Geohazards Monitoring
Focus Area will support compelling initiatives that
improve the resiliency of global and regional societies
through the application of geodetic science andtechnology. The working groups mandate will be todevelop an attainable and valuable goal as recommended
by the GGOS Science panel. Each working group willdefine a work-plan with an estimated time line that will be
subject to periodic review by the GGOS Coordinating
Board.

1094

Focus Area 3: Sea Level Change, Variability
and Forecasting
Chair: T. Schöne (Germany)
Sea level rise and its impact on human habitats andeconomic well being is one of the key issues in the climatechange discussion. In recent years this topic has received
considerable and growing attention by the general public,
engineers, researchers, and policy makers and calls for
multi-disciplinary research. In 2010 GGOS has identified
sea level change as one of the cross-cutting themes for
geodesy and established this topic as one of its Focus
Areas. The primary task of Focus Area 3 is to demonstrate
the value of different geodetic techniques available under
the umbrella of GGOS to the mitigation of sea level rise
including studies of the impacts of its change over theworld’s coastal regions and islands, and to support
practical applications such as sustainability.
Focus Area 3 interacts with the other two Focus Areas
as well as with the related Committees and Working
Groups of the GGOS Bureaus. Close cooperation isestablished and will be intensified with groups andorganizations working in related fields. One major topic is
the identification of gaps and their closure in geodetic
observing techniques and networks and to advocate
additions in the GGOS monitoring network and Services
where necessary.
Activities
Through the projects accepted ongoing Call for Participation
Focus Area 3 will progress with the following tasks:
x Identification or (re)-definition of the requirements for aroper understanding of global and regional/local sea
level rise and its variability especially in so far as theyelate to geodetic monitoring provided by the GGOS
Infrastructure, and their current links to externalorganizations (e.g., GEO, CEOS, and other observing
systems).
x Identification of gaps in geodetic observing techniques
contributing to sea level research and advocate
improvements and additions in the GGOS monitoring
network and Services where necessary
x Establishing Focus Area 3 as the interface and point-ofcontact between GGOS and organizations concernedwith sea level research aspects
x In the long-term, the aim is to support forecasting of
global and regional sea level for the 21st century.
Special emphasis will be given to local and regional
projects which re relevant to coastal communities, andwhich depend on the global perspective of GGOS.

Structures for the Period 2015-2019

1095

GGOS Bureau of Products and Standards
Inventory of Standards and Conventions
used for the Generation of IAG Products
D. Angermann1 · T. Gruber2 · M. Gerstl1 · R. Heinkelmann3 ·U. Hugentobler2 · L. Sánchez1 · P. Steigenberger4

c Springer-Verlag Berlin Heidelberg 2016
Revision 15 January 2016 / Contents

Preface

PrefaceScope of the document
Acknowledgements

The Global Geodetic Observing System (GGOS) released in 2008 a call for participation to complement
the existing structure by additional components, suchas the Coordinating Oﬃce and GGOS Portal, the Bureau for Standards and Conventions, and the Bureau
for Networks and Communications. The proposal of
the Forschungsgruppe Satellitengeodäsie (FGS) for theestablishment and operation of the GGOS Bureau forStandards and Conventions (BSC) was accepted by the
GGOS Steering Committee on December 14, 2008. Since
2009, the BSC is jointly operated by the Deutsches
Geodätisches Forschungsinstitut (DGFI) and the Institut für Astronomische und Physikalische Geodäsie(IAPG) of the Technische Universität München, bothin Munich, Germany, within the FGS.

1Introduction
1.1 GGOS: Mission, goals and structure
1.2 Standards and conventions

2

GGOS Bureau of Products and Standards
2.1 Mission and objectives
2.2 Tasks
2.3 Staff and representatives

3

Evaluation of numerical standards
3.1 Defining parameters
3.2 Solid Earth tide systems
3.3 Geopotential value W0
3.4 Open problems and recommendations

4

Product-based review
4.1 Celestial reference systems and frames
4.2 Terrestrial reference systems and frames
4.3 Earth Orientation Parameters (EOP)
4.4 GNSS satellite orbits
4.5 Gravity and geoid
4.6 Height systems and their realizations

5

Summary

Glossary
Bibliography

detlef.angermann@tum.de
1

Deutsches Geodätisches Forschungsinstitut (DGFI), Technische Universität München, Germany

2

Institut für Astronomische und Physikalische Geodäsie(IAPG), Technische Universität München, Germany

3Helmholtz Centre Potsdam, German Research Centre for Geosciences (GFZ), Germany

4

Deutsches Zentrum für Luft- und Raumfahrt (DLR), Germany

The FGS group includes, beside DGFI and IAPG, theForschungseinrichtung Satellitengeodäsie (FESG) of theTechnische Universität München, the Bundesamt für
Kartographie und Geodäsie (BKG), Frankfurt am Main,
Germany, and the Institut für Geodäsie und Geoinformation, University Bonn (IGG), Germany. The group
operates the Geodetic Observatory Wettzell, Germany,and pursues various research projects in space geodesy. The FGS is prominently involved in the management of the international scientiﬁc organizations and it
took over long-term commitments in the IAG Services
as data, analysis and combination centers.
In 2014, a restructuring of the GGOS organization was
performed. The existing components were kept and their
responsibilities were partly redeﬁned. The BSC has beenrenamed as GGOS Bureau of Products and Standards(BPS) and its tasks have been extended. The charter

Angermann et al.

1096

and implementation plan for the BPS was completed in
2015.
The BPS supports GGOS in its goal to obtain geodetic products of highest accuracy and consistency. In
order to fully beneﬁt from the ongoing technologicalimprovements of the observing systems, it is essentialthat the analysis of the precise space geodetic observations is based on the deﬁnition and application of common standards and conventions and a consistent representation and parameterization of the relevant quantities. This is of crucial importance for the establishment of highly accurate and consistent geodetic reference frames, as the basis for a reliable monitoring of
the time-varying shape, rotation and gravity ﬁeld of
the Earth. The BPS also concentrates on the integration of geometric and gravimetric parameters and thedevelopment of new products, required to address important geophysical questions and societal needs.
A key objective of the BPS is to keep track of adopted
geodetic standards and conventions across all components of the International Association of Geodesy (IAG)
as a fundamental basis for the generation of consistentgeometric and gravimetric products. The work is primarily build on the IAG Service activities in the ﬁeldof data analysis and combinations. The BPS shall act
as contact and coordinating point regarding homogenization of standards and IAG products. More specifically, major tasks in this ﬁeld are (i) to review andevaluate all standards, constants, resolutions and conventions adopted by IAG and its components, (ii) to
identify gaps, inconsistencies and deﬁciencies, and (iii)
to propose new standards if necessary. Following thistask description, the former BSC has started with thecompilation of an inventory based on the assessment of
the standards and conventions currently in use by IAG
and its components. This activity has been continued
by the BPS and as a result this document was created.
During the GGOS Coordination Board meeting and
IAG Executive Committee meeting in San Francisco(December 2014), the participants agreed on the procedure for the review of the inventory. It was decided
that the document should be evaluated by an external
review. The approved version of this document, which
is published in the IAG Geodesist’s Handbook 2016 reﬂects the status of January 15, 2016. A regularly updated version will be provided on the GGOS web site.
As a major outcome, this inventory presents the status regarding standards and conventions, identiﬁes gaps
and inconsistencies, and provides recommendations for
improvements. This recommendations should be discussed with dedicated experts in the ﬁeld and an action

plan should be compiled, including a task description,
speciﬁcation of responsibilities, and a time schedule.

Scope of the document
The BPS has the task to keep track of adopted standards and conventions across all IAG components andto evaluate products of IAG with respect to the adequate use of standards and conventions. Based on thisgeneral task description, a major activity of the BPS
was the compilation of an inventory regarding standards, constants, resolutions and conventions adopted
and used by IAG and its components for the generationof IAG products.
The scope of this document is summarized as follows:
Chapter 1 gives in the ﬁrst section some general information about GGOS including its mission, goals andthe organizational structure. The second part of thisintroductory chapter deals with standards and conventions from a general view along with some relevant
nomenclature, and it presents current standards, standardized units, fundamental physical standards, resolutions and conventions that are relevant for geodesy. In
the second chapter the mission and goals of the BPS aresummarized, along with a description of its major tasks.
It also presents the BPS staﬀ and the associated members, representing the IAG Services, the International
Astronomical Union (IAU) and other entities involvedin standards and conventions. Chapter 3 focusses on numerical standards, including time and tide systems andthe geopotential value W0 . Chapter 4 is the key elementof this document and it contains the product-based inventory, addressing the following topics: Celestial reference systems and frames, terrestrial reference systems and frames, Earth Orientation Parameters (EOP),
Global Navigation Satellite System (GNSS) satellite orbits, gravity and geoid, as well as height systems andtheir realizations. The structure of the corresponding
sections was homogenized to a large extent, however,its character is partly diﬀerent. This is a consequence ofthe current situation, that for some topics oﬃcial IAG
products exist (e.g., ITRF, EOP), whereas for others,
like the gravity ﬁeld and the height systems, no oﬃcial
IAG products are declared. In this product-based inventory, the BPS presents the current status, identiﬁes
gaps and inconsistencies as well as interactions between
diﬀerent products. In this context also open questions
and recommendations regarding standards and conventions for the generation of IAG products are provided.
In addition to this printed version, the inventory will be
regularly updated and will be published as a living doc-

Inventory of Standards and Conventions

1097

ument on the GGOS web site. This is important to keep
its contents up-to-date, since the standards and conventions are regularly updated and also the IAG products
are evolving with time, e.g., the upcoming ITRF2014
will be released early 2016 by the International Terrestrial Reference System (ITRS) Centre.
According to its Terms of Reference, the BPS also works
towards the development of new products derived froma combination of geometric and gravimetric observations and thus, such integrated products should be addressed in an updated version.

This ﬁrst revision cycle was completed at the end of
2014. The colleagues who provided feedback are:F. Barthelmes (Germany), S. Bettadpur (USA),
M. Bloßfeld (Germany), J. Böhm (Austria),
N. Donelly (Australia), J. Gipson (USA),
R. Gross (USA), J. Hassdyk (Australia),
B. Heck (Germany), T. Herring (USA),
C. Hohenkerk (United Kingdom), J. Ihde (Germany),
J. Kusche (Germany), F. Lemoine (USA),
E. Pavlis (USA), G. Petit (France),
C. Rizos (Australia), T. Schöne (Germany),
H. Schuh (Germany), M. Seitz (Germany),
R. Stanaway (Australia), D. Thaller (Germany).

Acknowledgements

The authors thank all these colleagues for their contributions.

This document has been reviewed in a two step procedure as described below. The eﬀorts of all reviewers andtheir constructive feedback and valuable comments on
the inventory are greatfully acknowledged by the authors. The suggestions and comments helped a lot toimprove the document and they are incorporated in thisversion.

During the GGOS Coordinating Board in San Francisco, USA in December 2014, it was decided that asecond (external ) review cycle should be conducted by
IAG. Responsible for this oﬃcial IAG review process
was the IAG Bureau (Chris Rizos, Harald Schuh andHermann Drewes). The IAG Secretary General, Hermann Drewes, took over the responsibility for the coordination of the review process. Each chapter/product of
the inventory was reviewed (mostly) by two reviewers(see Table 1). Again, many fruitful comments and suggestions have been received from the reviewers, whichwere incorporated in the ﬁnal version of this document.
The contributions of all reviewers, the support of the
IAG Bureau and the coordination of the review process
by Hermann Drewes is gratefully acknowlegded by theauthors.

The ﬁrst (internal ) review cycle was initiated by the
BPS in April 2014. The document was distributed to
the GGOS Coordinating Board members and to the
BPS associated members. Additionally, some of thesecolleagues and other experts were contacted personallyby the BPS to get feedback and detailed comments onparticular topics (sections) of the document. Many ofthem responded and provided very important feedback
and suggestions, which were incorporated in the ﬁrst
revision of the document.

Table 1: Reviewers designated by IAG to evaluate this document.

Chapter

Reviewers

Chapter 1.1
Chapter 1.2
Chapter 2
Chapter 3
Chapter 4.1
Chapter 4.2
Chapter 4.3
Chapter 4.4
Chapter 4.5
Chapter 4.6

H. Kutterer (Germany), C. Rizos (Australia)
H. Kremers (Germany), D. D. McCarthy, N. Stamatakos (USA)
H. Drewes (Germany), H. Schuh (Germany)
G. Petit (France), N. Sneuuw (Germany)
A. Nothnagel (Germany), J. Souchay (France)
Z. Altamimi (France), T. Herring (USA)D. Gambis (France), R. Gross (USA)A. Jäggi (Switzerland)
R. Barzaghi (Italy), U. Marti (Switzerland)
B. Heck (Germany), M. Sideris (Canada)

Inventory of Standards and Conventions: 1 Introduction

1098

1 Introduction
1.1 Global Geodetic Observing System(GGOS): Mission, goals andstructure
The GGOS was initially created as an IAG Project during the International Union of Geodesy and Geophysics(IUGG) meeting in 2003 in Sapporo, Japan, in response
to developments in geodesy, the increasing requirementsof Earth observations, and growing societal needs. Since
2004, GGOS represents IAG in the Group on Earth Observation (GEO) and contributes to the Global Earth
Observation System of Systems (GEOSS) [GEO 2005].
After a preliminary development phase, the Executive
Committee of the IAG decided to continue the Projectat its meeting in August 2015 in Cairns, Australia.
From 2005 to 2007, the GGOS Steering Committee,
Executive Committee, Science Panel, Working Groups,
and web pages were established. Finally, at the IUGG
meeting in 2007 in Perugia, Italy, IAG evaluated GGOS
to the status of a full component of IAG – as the permanent observing system of the IAG.

change research. GGOS relies on the observing systems
and analysis capabilities already in place in the IAG
Services and envisions the continued development of innovative technologies, methods and models to improve
our understanding of global change processes. IAG and
GGOS provide a framework that ranges from the acquisition, transfer and processing of a tremendous amountof observational data to its consistent integration. Consistency among the data sets from the diﬀerent (geometric and gravimetric) observation techniques is of
crucial importance for the generation of IAG products,
such as geodetic reference frames which are the basis
for the integration of geometry, Earth rotation and thegravity ﬁeld (see Figure 1.1).
GGOS as an organization is built upon the existing IAG
Services as a unifying umbrella, and will continue to be
developed for this purpose. Under this “unifying umbrella”, all the products provided by the diﬀerent IAG
Services are considered GGOS products – as ratiﬁed at
the IAG General Assembly in 2009 in Buenos Aires,
Argentina.
The mission and the overarching strategic focus areas of
GGOS are speciﬁed in its Terms of Reference (see www.
ggos.org). They were oﬃcially adopted by the IAG
Executive Committee (EC) at the IUGG XXV General
Assembly, Melbourne, Australia, 2011. Its ﬁrst revision
was approved by the IAG EC during the IUGG XXVI
General Assembly, Prague, Czech Republic, 2015.

Earth
rotation

The mission of GGOS is:ReferenceframesGravityfield

Geometry

Fig. 1.1: Integration of the “three pillars” geometry, Earth rotation and gravity field ([Rummel 2000], modified by [Plag et al.
2009]).

The IAG Services and Commissions provide the geodetic infrastructure and products, as well as the expertiseand support for scientiﬁc developments, which are thebasis for monitoring the Earth system and for global

1. To provide the observations needed to monitor, map
and understand changes in the Earth’s shape, rotation, and mass distribution.
2. To provide the global geodetic frame of reference thatis the fundamental backbone for measuring and consistently interpreting key global change processes andfor many other scientiﬁc and societal applications.
3. To beneﬁt science and society by providing the foundation upon which advances in Earth and planetarysystem science and applications are built.
The overarching strategic focus areas of GGOS goals
and objectives are:1. Geodetic Information and Expertise: GGOS outcomes will support the development and maintenanceof organizational intangible assests, including geodetic information and expertise. The development of
this strategic focus area will beneﬁt all other goals
and objectives.

1.2 Standards and conventions

2. Global Geodetic Infrastructure: Development of,
advocacy for, and maintenance of existing global geodetic infrastructure is a direct support of each GGOS
goal.
3. Services, Standardization, and Support: Optimal coordination, support, and utilization of IAG
Services, as well as leveraging existing IAG resources,
are critical to the progress of all GGOS goals and objectives.
4. Communication, Education, Outreach: Marketing, outreach, and engagement are critical elements
for sustaining the organizational fabric of GGOS.
The organizational structure of GGOS is comprised of
the following key components (see Figure 1.2):
GGOS Consortium – is the collective voice for all
GGOS matters.
GGOS Coordinating Board – is the central oversight and decision-making body of GGOS, and represents the IAG Services, Commissions, Inter-Commission
Committees, and other entities.
GGOS Executive Committee – serves at the direction of the Coordinating Board to accomplish day-today activities of GGOS tasks.
GGOS Science Panel – advises and provides recommendations relating to the scientiﬁc content of the
GGOS 2020 to the Coordinating Board; and represents
the geoscientiﬁc community at GGOS meetings.
GGOS Coordinating Office – coordinates the workwithin GGOS and supports the Chairs, the Executive
Committee and the Coordinating Board.
Bureau of Products and Standards (former Bureau for Standards and Conventions) – tracks, reviews,
examines, evaluates the standards, constants, resolutions and conventions adopted by IAG or its components and recommends their continued use or proposes
necessary updates; works towards the developement of
new products derived from a combination of geometricand gravimetric observations.
Bureau of Networks and Observations (former
Bureau for Networks and Communications) – develops strategies and plans to design, integrate and maintain the fundamental geodetic infrastructure, including communications and data ﬂows; monitors the networks and advovates for implementation of core andco-located network sites and improved network performance.
GGOS Working Groups and Focus Areas (former Themes) – address overarching issues common toseveral or all IAG components, and are a mechanism
to bring the various activities of the Services, Commissions and Inter-Commission Committees together, or1099

to link GGOS to external organizations. Focus areas
are cross-disciplinary and address speciﬁc areas where
GGOS contributors work together to address broader
and critical issues.
IAG – promotes scientiﬁc cooperation and research ingeodesy on a global scale and contributes to it throughits various research bodies.
IAG Services, Commissions and relevant InterCommission Committees – are the fundamental supporting elements of GGOS.
GGOS Inter Agency Committee (GIAC) – a forum that seeks to generate a uniﬁed voice to communicate with Governments and Intergovernmental organizations (GEO, UN bodies) in all matters of global andregional spatial reference frames and GGOS research
and applications.

1.2 Standards and conventions
Standards and conventions are used in a broad senseand various international organizations and entities are
involved in this subject. This section gives general information and an overview about the standards andconventions that are currently in use within the geodetic community. According to Drewes [2008] and Angermann [2012] one shall distinguish standards, standardized units, fundamental physical standards, resolutions
and conventions. Besides this, also background models
used for the processing of the space geodetic observations are introduced in this section.

1.2.1 Standards
Standards are generally accepted speciﬁcations and measures for quantitative or qualitative values that deﬁneor represent under speciﬁc conditions the magnitudeof a unit. A technical standard is an established norm
or requirement, which is usually a formal documentthat provides uniform engineering or technical criteria,
methods and processes or procedures.
Various international, regional and national organizations are involved in the development, coordination,
revision, maintenance, etc. of standards that address
the interests of a wide area of users. Important for geodesy is the International Organization for Standardization (ISO), an international standard-setting bodycomposed of representatives from a network of national
standards institutes of more than 150 countries. The
Technical Committee ISO/TC211 (www.isotc211.org)

Inventory of Standards and Conventions: 1 Introduction

1100

GGOS Consortium(Steering and Election Committee)

GGOS Coordinating Board(Decision-Making Body)

GGOS Executive Committee(Management Board)

GGOS Science Panel

ReportingDirection

GGOS Inter-Agency
Committee (GIAC)

GGOS Coordinating Office• Director• Secretariat• Outreach and User Linkage• Web and Social Media• Focus Area Coordination

GGOS Bureau of Networks & Observations

GGOS Bureau of Products & Standards• IAG Service Network Representatives• Committee on Satellite Missions• Committee on Data and Information Systems• Committee on Performance Simulations andArchitectural Trade-Offs (joint with IAG SC 1.2)

• IAG Service Analysis Coordinators andRepresentatives• Committee for Earth System Modelling• Working Group on Establishment of the GGRF
• Working Group on ITRS Standards

Reporting

Reporting

GGOS Focus Areas• Theme 1: Unified Height System• Theme 2: Geohazards Monitoring• Theme 3: Sea Level Change, Variability, andForecasting

IERS Working Group

IERS Conventions Centre

Site Survey and Co-location

Standards and Conventions

Fig. 1.2: Organizational structure of GGOS as adopted in 2015. Its initial structure [Kutterer et al. 2012] was restructured in 2014.
The former Bureau on Networks and Communications (BNC) was renamed the Bureau of Networks and Observations (BNO), andthe former Bureau of Standards and Conventions (BSC) was renamed the Bureau of Products and Standards (BPS). “Focus Areas”
were formerly called “Themes”. Please also note that GGOS is built upon the foundation provided by the IAG Services, Commissions,and Inter-Commission Committees.

was formed within ISO to cover the areas of digital geographic information and geomatics. Also relevant forgeodesy is the Open Geospatial Consortium (OGC), aninternational voluntary standards organization, originating in 1994. In OGC, more than 400 governmen-

tal, commercial, nonproﬁt and research organizations
worldwide collaborate in a consensus process encouraging development and implementation of open standards
for geospatial content and location-based services, Geographic Information System (GIS) data processing and1.2 Standards and conventions

data sharing. The ISO and OGC standards are appliedin geo-referencing, spatial analysis, and communication(service speciﬁcation). There is a close cooperation between OGC, ISO/TC211 and IAG components.
The standards and conventions that are relevant for geodesy are based primarily on decisions made by international organizations or bodies involved in this topic,
such as– the Bureau International de Poids et Mesures (BIPM),– the Committee on Data for Science and Technology(CODATA)and by resolutions related to standards and conventions
adopted by the Councils of– the International Union of Geodesy and Geophysics(IUGG),– the International Astronomical Union (IAU) and– the International Association of Geodesy (IAG).
Within IAU, the Commission A3 “Fundamental Standards” (www.iau.org/science/scientific_bodies/
commissions/A3) and the IAU’s Standards of Fundamental Astronomy (SOFA) service (www.iausofa.org)
are directly involved in standards.

1.2.2 Standardized units
In the International Vocabulary of Basic and General
Terms in Metrology [BIPM 2006; ISO/IEC 2007] theterms quantities and units are deﬁned. The value ofa quantity is expressed as the combination of a number and a unit. In order to set up a system of units,
it is necessary ﬁrst to establish a system of quantities,
including a set of equations relating those quantities.
Binding for geodesy is the International System of Units(SI), which was adopted by the 11th General Conference on Weights and Measures (1960). It is maintainedby the BIPM. The units are divided into two classes –base units and derived units. In a similar way the corresponding quantities are described as base quantities
and derived quantities. In the SI there are seven baseunits representing diﬀerent kinds of physical quantities.
Three of them are applied in geodesy:– Time (standardized unit second [s]): The second is
the duration of 9 192 631 770 periods of the radiation
corresponding to the transition between the two hyperﬁne levels of the ground state of the caesium 133
atom.
– Length (standardized unit metre [m]): The metre is
the length of the path travelled by light in vacuum
during a time interval of 1/299 792 458 of a second.

1101– Mass (standardized unit kilogram [kg]): The kilogram is the unit of mass. It is equal to the massof the international prototype of the kilogram.
The number of derived units and derived quantities ofinterest in geosciences can be extended without limit.
For example, the derived unit of speed is metre persecond [m/s], or centimetre per second [cm/s] in theSI. Whereas the kilometre per hour [km/h] is a unit
outside the SI but accepted for use with the SI. The
same holds for the gal [cm/s2 ] which is a special non-SI
unit of acceleration due to gravity.
The realization of the SI at the BIPM constitutes a fundamental contribution to the tasks of the IAG. One of
the ﬁve scientiﬁc departments of the BIPM, the “Timedepartment”, is a service of the IAG. The activities ofthis department are focused on the maintenance of the
SI second and the formation of the international reference time scales.

1.2.3 Fundamental physical constants
The formulations of the basic theories of physics andtheir applications are based on fundamental physicalconstants. These quantities, which have speciﬁc anduniversally used symbols, are of such importance thatthey must be known as accurately as possible. A physical constant is generally believed to be both universal
in nature and constant in time. In contrast, a mathematical constant is a ﬁxed numerical value, which does
not directly involve any physical measurement. A complete list of all fundamental physical constants is givenby the National Institute of Standards and Technology(NIST). NIST publishes regularly a list of the constants.
The CODATA is an interdisciplinary Scientiﬁc Committee of the International Council for Science (ICSU).
IUGG and IAU are member unions of CODATA. The
Committee works to improve the quality, reliability,
management and accessibility of data. CODATA is concerned with all types of data resulting from measurements and calculations in all ﬁelds of science and technology, including physical sciences, biology, geology, astronomy, engineering, environmental science, ecology
and others.
The CODATA Committee (former Task Group) on Fundamental Physical Constants was established in 1969.
Its purpose is to periodically provide the international
scientiﬁc and technological communities with an internationally accepted set of values for the fundamental
physical constants. The ﬁrst such CODATA set was
published in 1973, and later in 1986, 1998, 2002, 2006

1102

and 2010, see, [Mohr et al. 2012], and the open accessible report at physics.nist.gov/cuu/Constants/
Preprints/Isa2010.pdf. The latest version, the 2014least-squares adjustment of the values of the set of fundamental physical constants was released in 2015. The
2014 set replaces the previously recommended 2010 CODATA set and may also be found on the World Wide
Web at www.physics.nist.gov/Constants. The fundamental physical constants are classiﬁed in universal,
electromagnetic, atomic and nuclear, physico-chemical
constants as well as adopted values. The set of values
provided by CODATA do not aim at covering all scientiﬁc ﬁelds. Only few of these fundamental constants
are also relevant for geodesy. These are primarily two
universal constants and two adopted values, which are
given below:a) Universal constants– Newtonian constant of gravitation (G):(6.674 08 ± 0.00031) · 10−11 m3 kg−1 s−2– Speed of light in vacuum (c, c0 ):299 792 458 m/s (exact)b) adopted values (as mean values at sea level)– Standard acceleration of gravity (gn ):9.806 65 m/s2 (exact)– Standard atmosphere (atm): 101 325 Pa (exact)
It is obvious, that the astrogeodetic community needs,
in addition to these fundamental physical constants, a
set of suitable fundamental parameters as a basis for thedeﬁnition and realization of reference systems as well as
for the generation of geodetic products. The geodetic
activities in this ﬁeld are addressed in Section 3.1. Itshall also be mentioned, that the Conventions of theInternational Earth Rotation and Reference Systems
Service (IERS) provide in Section 1.2 a summary ofnumerical standards [Petit et al. 2010], as reﬂecting thesituation in 2010. More information on the IERS Conventions and on fundamental parameters can be foundin Sections 1.2.5 and 3.1.

1.2.4 Resolutions
A resolution is a written motion adopted by a deliberating body. The substance of the resolution can beanything that can normally be composed as a motion.
In this context we refer to the motion for adopting standards, constants or any parameters to be used by institutions and persons aﬃliated with the adopting body.
Most important resolutions for geodesy are those adopted by IUGG, IAG, and IAU.

Inventory of Standards and Conventions: 1 Introduction

The IUGG and IAG resolutions are adopted at the
IUGG General Assemblies and published every four
years in the corresponding IAG Geodesist’s Handbooks[Drewes et al. 2012]. They are also available in electronic
form at www.iugg.org/resolutions.
The IAU resolutions are adopted by General Assemblies held every 3 years. They are published regularlyin the IERS Conventions along with detailed information for their implementation [e.g., Petit et al. 2010].
An electronic version can be obtained from www.iau.
org/administration/resolutions.
Resolutions are non-binding laws of a legislature, butmore binding than recommendations. In non-legal bodies, such as IUGG, IAG and IAU, which cannot passlaws, they form the highest level of commitment. Resolutions shall be respected by all institutions and persons
aﬃliated with the adopting body.
The resolutions, which are relevant with respect to standards and conventions for geodesy, are summarized below in chronological order. Please note that only somemajor information is extracted from the original resolutions. For the full version follow the links above.
IUGG Resolution No. 7 (1979) and IAG Resolution No. 1 (1980) on the Geodetic Reference System
1980 (GRS80) [Moritz 2000]. It is recommended that
the Geodetic Reference System 1967 shall be replaced
by a new Geodetic Reference System 1980, also basedon the theory of the geocentric equipotential ellipsoid.
IAG Resolution No. 16 (1983) on tide systems, recognizing the need for the uniform treatment of tidal corrections to various geodetic quantities such as gravity
and station positions. It is recommended that the indirect eﬀect due to the permanent yielding of the Earthshall not be removed [IAG 1984].
IUGG Resolution No. 2 (1991) on the Conventional
Terrestrial Reference System (CTRS) recommends that:– CTRS to be deﬁned from a geocentric non-rotating
system by a spatial rotation leading to a quasi-Cartesian system,– the geocentric non-rotating system to be identical to
the Geodetic Reference System (GRS) as deﬁned in
the IAU resolutions,– the coordinate-time of the CTRS as well as the GRS
to be the Geocentric Coordinate Time (TCG),– the origin of the system to be the geocenter of the
Earth’s masses including oceans and atmosphere, and– the system to have no global residual rotation withrespect to horizontal motions at the Earth’s surface.

1.2 Standards and conventions

IAU Resolution A4 (1991) has set up a general relativistic framework to deﬁne reference systems centeredat the barycenter of the solar system and at the geocenter.
IAU Resolution B2 (1997) on the International Celestial Reference System (ICRS). From January 1, 1998,
the IAU celestial reference system shall be the ICRS.
The corresponding fundamental reference frame shallbe the International Celestial Reference Frame (ICRF)
constructed by the IAU Working Group on reference
frames. The IERS should take appropriate measures,in conjunction with the IAU Working Group on reference frames, to maintain the ICRF and its ties to thereference frames at other wavelengths.
IAU Resolution (2000) contains several speciﬁc resolutions (RES):
RES B1.1 Maintenance and establishment of reference frames and systems
RES B1.2 Hipparcos Celestial Reference FrameRES B1.3 Deﬁnition of the Barycentric Celestial Reference System (BCRS) and Geocentric Celestial Reference System (GCRS)RES B1.4 Post-Newtonian Potential Coeﬃcients
RES B1.5 Extended relativistic framework for timetransformations and realization of coordinate times in the solar system
RES B1.6 IAU Precession-Nutation Model
RES B1.7 Deﬁnition of the Celestial Intermediate PoleRES B1.8 Deﬁnition and use of Celestial and Terrestrial Ephemeris Origins
RES B1.9 Re-deﬁnition of the Terrestrial Time (TT)RES B2
Coordinated Universal Time (UTC).
The Resolutions B1.1 through B1.8 of the IAU General Assembly 2000 have been adopted by IUGG at its
General Assembly in 2003 (see Resolution No. 4). Moreinformation on these resolutions may be found in the“Proceedings of the IERS Workshop on the Implementation of the New IAU Resolutions” published in the
IERS Technical Note No. 29 [Capitaine et al. 2002].
IUGG Resolution 3 (2003) strongly supports theestablishment of the GGOS (former IGGOS) Project
within the new IAG structure as geodesy’s contribution
to the wider ﬁeld of geosciences and as the metrologicalbasis for the Earth observation programs within IUGG.
IAU Resolution B1 (2006) on adopting the P03 precession theory and deﬁnition of the ecliptic. It accepts
the conclusions of the IAU Division I Working Groupon Precession and Ecliptic [J. L. Hilton et al. 2006], andrecommends that the terms lunisolar precession andplanetary precession be replaced by precession of theequator and precession of the ecliptic, respectively, and1103

that, beginning on 1 January 2009, the precession component of the IAU 2000A precession-nutation model be
replaced by the P03 precession theory [Capitaine et al.
2003] in order to be consistent with both dynamical
theories and the IAU 2000 nutation.
IAU Resolution B2 (2006) is a supplement to the
IAU 2000 resolutions on reference systems, containing
primarily two recommendations, the ﬁrst to harmonize
the name of the pole and origin to “intermediate” and asecond recommendation ﬁxing the default orientation of
the BCRS and GCRS, which are assumed to be oriented
according to the ICRS axes (for more information see
the IERS Conventions 2010 [Petit et al. 2010]).
IAU Resolution B3 (2006) is on the re-deﬁnition of
Barycentric Dynamical Time (TDB) (for more information see the IERS Conventions 2010 [Petit et al. 2010]).
This resolution has also been adopted by the IUGG in
2007 as written in Resolution 1.
IUGG Resolution No. 2 (2007) on the Geocentricand International Terrestrial Reference System (GTRS
and ITRS) endorses the ITRS as the speciﬁc GTRS
for which the orientation is operationally maintained incontinuity with past international agreements (BIH orientation), and adopts the ITRS as the preferred GTRS
for scientiﬁc and technical applications, and urges othercommunities, such as the geo-spatial information andnavigation communities, to do the same.
IUGG Resolution No. 3 (2007) on the Global Geodetic Observing System (GGOS) of the IAG. The new
structure of IAG reﬂected by the designation of GGOS
as a permanent component, urges sponsoring organizations and institutions to continue their support ofthe elements of GGOS, which is crucial for sustaining
long-term monitoring and understanding of the Earthsystem.
IAU Resolution B2 (2009) on IAU 2009 astronomical standards. It recommends that the list of previously
published constants compiled in the report of the IAU
Division A Working Group Numerical Standards for
Fundamental Astronomy (NSFA) [Luzum et al. 2011]
be adopted as the IAU (2009) System of Astronomical
Constants, that Current Best Estimates (CBE) of astronomical constants be permanently maintained as anelectronic document, and that the IAU establish a permanent body to maintain the CBEs for fundamental
astronomy.
IAU Resolution B3 (2009) resolves that from 01
January 2010 the fundamental astronomic realizationof the International Celestial Reference System (ICRS)
shall be the Second Realization of the International Celestial Reference Frame (ICRF2) as constructed by the
IERS/International VLBI Service for Geodesy and As-

1104

trometry (IVS) Working Group on the ICRF in conjunction with the IAU Division I Working Group on
the International Celestial Reference Frame [Fey et al.
2009].
IUGG Resolution No. 3 (2011) on the ICRF2. This
resolution urges that the ICRF2 shall be used as thestandard for all future applications in geodesy and astrometry, and that the highest consistency between the
ICRF, the ITRF, and the EOP as observed and realized
by IAG and its components such as the IERS should bea primary goal in all future realizations of the ICRS.
IAU Resolution B2 (2012) on the re-deﬁnition of
the astronomical unit of length. It is recommended thatthe astronomical unit be re-deﬁned to be a conventional
unit of length equal to 149 597 870 700 m exactly, inagreement with the value adopted in IAU 2009 Resolution B2 (see www.iau.org/static/resolutions/
IAU2012_English.pdf).
IAG Resolution No. 1 (2015) for the deﬁnition andrealization of an International Height Reference System(IHRS). It outlines ﬁve fundamental conventions for thedeﬁnition of the IHRS, including a conventional value
for the reference potential W0 = 62 636 853.4 m2 s−2 ,and stating the mean tidal system/mean crust as thestandard for the generation of IHRS-related products(see iag.dgfi.tum.de/index.php?id=330).
IAG Resolution No. 2 (2015) for the establishmentof a global absolute gravity reference system. It resolves, among other issues, to initiate the replacementof the International Gravity Standardization Net 1971
(IGSN71) by the new Global Absolute Gravity Reference System.
IUGG Resolution No. 3 (2015) on the Global Geodetic Reference Frame (GGRF) recognizing the adoption
in February 2015 by the General Assembly of the United
Nations (UN) of a resolution entitled “A Global Geodetic Reference Frame for Sustainable Development”. It
urges the UN Global Geospatial Information Management (GGIM) GGRF Working Group to engage withIUGG and other concerned organizations such as theCommittee of Earth Observation Satellities (CEOS) and
the Group on Earth Observation (GEO), in order topromote the implementation of the UN GGIM GGRG
RoadMap.
UN Resolution (2015) on a Global Geodetic Reference Frame (GGRF). The United Nations General
Assembly adopted the resolution on a Global Geodetic
Reference Frame for Sustainable Development (A/RES/
69/266) on February 26, 2015.

Inventory of Standards and Conventions: 1 Introduction

1.2.5 Conventions
A convention is a set of agreed, stipulated or generally
accepted norms, standards or criteria. In physical sciences, numerical values such as constants or quantities
are called conventional if they do not represent a measured property of nature, but originate from a convention. A conventional value for a constant or a speciﬁcquantity (e.g., the potential of the geoid W0 ) can be, forexample, an average of measurements agreed between
the scientists working with these values.
In geodesy, conventions may be adopted by IAG and
its components (Services, Commissions, Inter-Commission Committees, and GGOS). Most established andcommon are the conventions of the IERS. These IERS
conventions are regularly updated and they serve as
the basis for the analysis of the geometric observations
and for the generation of IERS products. The IERS
conventions are based on the resolutions of the international scientiﬁc unions, namely the IUGG, IAU and
IAG and they provide those constants, models, procedures, and software that have the most signiﬁcance to
IERS products (e.g., celestial and terrestrial reference
frames, Earth orientation parameters).
The latest version are the IERS Conventions 2010 [Petit
et al. 2010]. They consist of eleven chapters that focus
on various topics, such as general deﬁnitions and numerical standards, the deﬁnition and realization of thecelestial and terrestrial reference systems, transformations between both systems, the geopotential, displacement of reference points, tidal variations in the Earth’s
rotation, models for atmospheric propagation delays,
general relativistic models for space-time coordinatesand equations of motion and general relativistic models for propagation. The IERS conventions provide thebasis for the work of the geometric Services of IAG, theInternational GNSS Service (IGS) [Dow et al. 2009], theInternational Laser Ranging Service (ILRS) [Pearlman
et al. 2002], the International VLBI Service for Geodesy and Astrometry (IVS) [Schuh et al. 2012], and theInternational DORIS Service (IDS) [Willis et al. 2010],
as well as for the deﬁnition and realization of geodetic reference systems and for the generation of IERS
products.
For data and products related to the gravity ﬁeld, equivalent conventions have to be established by the International Gravity Field Service (IGFS), but this is still an
issue that needs to be solved. Instead, for satellite gravity ﬁeld missions (e.g., CHAMP, GRACE, GOCE) different standards or conventions are in current use, e.g.,
EIGEN [Förste et al. 2012], GOCE [European GOCE

1.2 Standards and conventions

1105

gravity consortium 2012], EGM2008 [N. Pavlis et al.
2012].
Moreover, consistency between geometric and gravimetric standards has to be ensured, as a prerequisite for the
major goal of GGOS, the integration of the geometry,rotation and gravity ﬁeld of the Earth. A key objectiveof the BPS is to contribute to this important goal.

1.2.6 Physical and empirical backgroundmodels
Besides the numerical standards and conventions, thebackground models that are applied for the processingof the geodetic observations shall be addressed in thisinventory. These models need to be developed with a
speciﬁc level of accuracy for various eﬀects and phenomena that can be used to compute estimates of thespace geodetic observations. Usually two diﬀerent typesof correction models are distinguished:– Models to correct the eﬀect of geophysical phenomena that aﬀect the station positions, quasar positions
and/or satellite orbits (e.g., solid Earth tides, ocean
tides, pole tides, . . . );– Models to account for eﬀects that directly inﬂuence
the space geodetic observations such as signal propagation (ionosphere, troposphere) and technique-related instrumental eﬀects, e.g. GNSS antenna phasecenter variations, thermal deformation of VLBI telescopes, and SLR range biases.

The ﬁrst type of models is applied to the a-priori values
for station coordinates, satellite orbits and quasar positions (in the case of VLBI), whereas the second type
is mostly computed in observation space, but can also
be applied to the a-priori values. The corrected a-priori
values are then used to compute the theoretical geometry at the observation epoch. Finally, the values “o-c”(observed minus computed) are derived, and are an input for the adjustment procedure and the computationof geodetic products (see Figure 1.3).
Concerning the background models, a further type of
discrimination may be mentioned: While some models
refer to a-priori ﬁxed, fully determined values, someothers use parameterized expressions; the parametervalues are estimated within the least squares adjustment process related to the adjustment of the observations. Examples of the second type are, e.g., parametersin the solar radiation pressure model or harmonic coeﬃcients in the description of the Earth’s gravitational
potential.
It is obvious, that for the processing of the geodetic
observations all the models have to be applied consistently according to well-deﬁned standards and conventions. This is important to get interpretable and consistent results, in particular if the data of the individual
techniques are combined to generate geodetic products,
such as the terrestrial reference frame and the EOP.

A-priori values (e.g., station positions,
quasar coordinates for VLBI, orbits forsatellite techniques, etc.)

Original observations (e.g., VLBI,SLR, GNSS, DORIS)

Geophysical and empirical models tocorrect a-priori values (e.g., Earth tides,pole tide and ocean tides, etc.)

Computed models that affect theobservation (e.g., troposphere, ionosphere, instrumental calibrations, . . . )Computation of theoretical value andits partial derivatives for the observation at the measurement epoch

Corrected observations (e.g., VLBI,SLR, GNSS, DORIS)

Computation of “o-c”(observed minus computed)

Adjustment and computationof geodetic products

Fig. 1.3: Procedure for applying geophysical and empirical background models in the processing ofspace geodetic observations. Please note that in some software packages the second type of models(that affect the observations) are applied to the a-priori values, which will lead to identical results.

1106

Inventory of Standards and Conventions: 2 GGOS Bureau of Products and Standards

2 GGOS Bureau of Products and Standards
The GGOS Bureau of Products and Standards (BPS)
is a recent reorganization of the former GGOS Bureau
for Standards and Conventions (BSC), which was established in 2009. This resulted from a re-alignment of
the GGOS organization during the GGOS Coordinating Board Meeting in Vienna (April 2014). It has been
decided to keep the existing GGOS components, to redeﬁne and clarify their responsibities, and to extend thetasks of both GGOS Bureaus. A new charter and implementation plan for the BPS was completed in 2015.
The BPS is hosted and supported by the Deutsches
Geodätisches Forschungsinstitut (DGFI) and the Institut für Astronomische und Physikalische Geodäsie(IAPG) of the Technische Universität München, within
the Forschungsgruppe Satellitengeodäsie (FGS) [Angermann et al. 2015; Hugentobler et al. 2012].

2.1 Mission and objectives
The work of the BPS is primarily built on the IAG
Services and the products they derive on an operational basis for Earth monitoring making use of various space geodetic observation techniques such as VeryLong Baseline Interferometry (VLBI), Satellite Laser
Ranging (SLR)/Lunar Laser Ranging (LLR), GNSS,
Doppler Orbit Determination and Radiopositioning Integrated by Satellite (DORIS), altimetry, gravity satellite missions, gravimetry, etc. The purpose and major
goal of the BPS is to ensure that common standards andconventions are adopted and implemented by the IAG
components as a fundamental basis for the analysis of
the diﬀerent geodetic observations to ensure consistent
results for the geometry, rotation and gravity ﬁeld of
the Earth along with its variations in time. The BPS
supports GGOS in its goal to obtain products of highest
accuracy, consistency, and temporal and spatial resolution, which refer to a unique reference frame, stable overdecades in time.
The objectives are:
– To keep track of the strict observance of adopted
geodetic standards, standardized units, fundamental
physical constants, resolutions and conventions in thegeneration of IAG products.
– To review, examine and evaluate all standards, constants, resolutions and conventions adopted by IAG
or its components and recommend their use or propose the necessary updates.

– To identify gaps, inconsistencies and deﬁciencies instandards and conventions and to initiate steps toremove them.
– To propose the adoption of new standards and conventions where necessary, and submit the corresponding resolutions for the approval by IAG, IUGG, IAU,
and other international organizations.
– To propagate standards and conventions to the wider
scientiﬁc community and promote their use.

2.2 Tasks
Main tasks related to standards and conventions are:
– The BPS assesses the geodetic standards and conventions currently in use by all the IAG Services forthe generation of geodetic/geophysical products. It
reviews oﬃcial products of IAG with respect to theadequate use of standards and conventions.
– The BPS propagates all geodetic standards and conventions to geodetic and general scientiﬁc communities and urges their common use. If necessary, the
BPS proposes the adoption of new standards andconventions, changes and revisions, and submits thecorresponding resolutions for the approval by IAG,IUGG, IAU, and other international organizations.
– The BPS propagates most important standards tosociety in general and promotes their use. These outreach activities include the participation at relevant
conferences and meetings and submission of papers
to journals also in neighbouring ﬁelds.
– The BPS maintains regular contact with all internal and external institutions involved in the adoptionof standards, resolutions and conventions. It thereby
takes advantage of representations in IAG Services,
IAG Commissions, IUGG and IAU, as well as in otherbodies involved in standards and conventions (e.g.,
BIPM, ISO, CODATA).
– The Bureau is in charge of administrative tasks, communications, data base and web support. For thesetasks a close cooperation with the GGOS Coordination Oﬃce and the GGOS Portal is established.
– For speciﬁc issues dealing with particular ﬁelds of geodesy the BPS may set up dedicated working groups.
Regional or national members may be included insuch working groups– The BPS reports regularly to the GGOS Coordinating Board and to the IAG Executive Committee, and– if necessary or appropriate – to the IUGG Executive Committee.

2.3 Staff and representatives

1107

2.3 Staff and representation of IAG
components and other entities
In 2009, when the BSC started its operation, the staﬀ
members of the Bureau were U. Hugentobler (Director), D. Angermann (Deputy Director), J. Bouman, M.
Gerstl, T. Gruber, B. Richter, P. Steigenberger. In order to improve balance between members aﬃliated withgeometric and gravimetric research ﬁelds and due to afew personnel changes, the present BPS staﬀ is (status
December 2015):– Director: D. Angermann (successor of U. Hugentobler since April 2011)– Deputy director: T. Gruber– Geodetic ﬁelds covered by the BPS team:– Geometry, orbits, TRF: D. Angermann, U. Hugentobler, P. Steigenberger (as associated member)– Earth Orientation, CRF: M. Gerstl, R. Heinkelmann (as representative of IAU)
– Gravity, height systems: T. Gruber, L. Sánchez
In its current structure the following GGOS entities areassociated with the BPS:
– Committee “Contributions to Earth System Modelling”, Chair: M. Thomas (Germany),– Joint Working Group “Establishment of the Global
Geodetic Reference Frame (GGRF)”,
Chair: U. Marti (Switzerland),– Working Group “ITRS Standards for ISO TC211”,
Chair: C. Boucher (France).

As deﬁned in its charter, the BPS serves as contact andcoordinating point for the IAG Analysis and Combination Centers regarding the homogenization of IAG/
GGOS standards and products. The IAG Services andthe other entities involved in standards and geodetic
products have chosen their representatives as associatedmembers of the BPS. The Bureau comprises the staﬀ
members, the chairs of the associated GGOS components, the committee and two working groups as listed
above, as well as representatives of the IAG Services
and other entities. The status of December 2015 is summarized in Table 2.1. Regarding the development ofstandards, there is a link with the IERS Conventions
Center, the IAU Working Group “Numerical Standards
for Fundamental Astronomy”, BIPM, CODATA, NIST
and ISO/TC211.
This conﬁguration of the BPS ensures a close interaction with the IAG Services and the other entities involved in standards. A communication plan has been
setup for a regular exchange of information, in particular regarding the homogenization of standards and IAG
products. Regular meetings of the BPS staﬀ members
take place in Munich every two months to perform theoperational business. In addition regular telecons andface-to-face meetings (e.g., twice per year) with the BPS
staﬀ and the representatives (and invitees) take place
to coordinate and manage the BPS work, to monitor
progress against schedule, and to redeﬁne tasks and responsibilites in case of need.

Table 2.1: Associated members of the BPS, representing the IAG Services, IAU and other entities (status: December 2015).
T. Herring, USA, G. Petit, France
U. Hugentobler, Germany
E. Pavlis, USA
J. Gipson, USA
F. Lemoine, J. Ries, USA
J.-M. Lemoine, H. Capdeville, France
R. Barzaghi, Italy
F. Barthelmes, Germany
S. Bonvalot, France
R. Heinkelmann, Germany
M. Craymer, Canada
L. Hothem, USA
J. Ádám, Hungary
J. Ihde, Germany
J. Kusche, Germany
P. Steigenberger, Germany

International Earth Rotation and Reference Systems Service (IERS)
International GNSS Service (IGS)International Laser Ranging Service (ILRS)International VLBI Service for Geodesy and Astrometry (IVS)International DORIS Service (IDS)
International DORIS Service (IDS)
International Gravity Field Service (IGFS)
International Center for Global Gravity Field Models (ICGEM)
Bureau Gravimetric International (BGI)International Astronomical Union (IAU), Working Group“Numerical Standards for Fundamental Astronomy”
Chair of Control Body for ISO Geodetic Registry Network
Vice-Chair of Control Body for ISO Geodetic Registry Network
Chair of the IAG Communication and Outreach Branch
IAG representative to ISO/TC211
Representative of gravity community
Representative of GNSS community

1108

Inventory of Standards and Conventions: 3 Evaluation of numerical standards

3 Evaluation of numerical standards
3.1 Defining parameters of geodetic
reference systems, time and tidesystems
The IUGG resolution No. 7 (1979) and the IAG resolution No. 1 (1980) recommend that the Geodetic Reference System 1980 (GRS80) [Moritz 2000] shall be usedas the oﬃcial reference for geodetic work. The GRS80
is deﬁned by four conventional constants GM , a, J2 , ω(see Table 3.1). The GRS80 is now more than 30 years
old and thus these conventional constants are not anymore a good representation of a best-ﬁtting set of Earthparameters. However, the IAG recommends the GRS80
parameters as a conventional ellipsoid, i.e. to convert
Cartesian coordinates into ellipsoidal coordinates. It is
used worldwide for many map projections and millions
of coordinates are related to it.
The numerical standards and adopted constants may
also change with time, and thus we would better speak
about fundamental parameters instead of constants[Groten 2004]. In the last few years, substantial progresshas been achieved in the estimation of these fundamental parameters and their temporal changes. Consequently, the introduction of a new Geodetic Reference System (i.e., GRS2000) was a key topic within thegeodetic community, in particular in Special Commission 3 “Fundamental Constants” [Groten 2004] of theIAG (in its old structure). However, after lengthy discussion and consideration, it was decided not to propose
any change of the existing GRS80 at that time. Nevertheless, some progress was made and a consistent setof fundamental parameters and current (2004) best estimates have been compiled [Groten 2004]. The paper
lists several possible values for the parameters. A consistent set is deﬁned in section III of that paper, which wasused for the IERS Conventions 2010 [Petit et al. 2010].
Table 3.1 summarizes the numerical standards given
in diﬀerent sources, namely the conventional GRS80
constants [Moritz 2000], the fundamental parametersof [Groten 2004], the IERS Conventions 2010 and theEarth Gravitational Model 2008 (EGM 2008 [N. Pavlis
et al. 2012]).
Various factors have to be considered for a comparison
and interpretation of the values displayed in Table 3.1.
The values are obtained from diﬀerent sources aiming
at diﬀerent purposes. The GRS80 is still used as conventional ellipsoid (e.g., the IERS Conventions (2010),
Chapter 4, recommend to use the GRS80 ellipsoid toexpress geographical coordinates), although the values

are no longer truly representing reality. Except for the
angular rotation velocity ω, all other GRS80 values differ from the consistent set of fundamental parameters
published by Groten about 25 years later [Groten 2004].
For example, the diﬀerence for the equatorial radius a
is about 0.4 m. The set of fundamental parameters of[Groten 2004] was kept for the IERS Conventions 2010.
The adopted standards for the EGM 2008 were deﬁned
in the same geodetic reference system as adopted for
EGM 96 [Lemoine et al. 1998] to ensure consistency between both gravity ﬁeld models. For a comparison of
the values displayed in Table 3.1 it has also to be considered, that they are partly expressed in diﬀerent time
and tide systems.
Without going into detail on time systems, it shall bementioned that the IUGG Resolution No. 2 (1991) recommends that the Geocentric Coordinate Time (TCG)
shall be used for the Geodetic Reference System (GRS).
In practice, however, all analysis centers for the geometric space techniques use a scale consistent with theTerrestrial Time (TT). As described in the IERS Conventions the relation between both time scales is givenby the equation
LG = 1 − d(TT)/d(TCG) = 6.969290134 · 10−10(3.1)
Thus, the diﬀerence between both time scales and thecorresponding length scales is about 0.7 ppb (parts per
billion). Hence the value for the gravitational constantGM depends on the metric (see Table 3.1)
GMTT = GMTCG (1 − LG ) .

(3.2)

It follows that the TT-compatible value of GM given for
the EGM2008 standards is consistent with the TCGcompatible value given for the IERS Conventions 2010(see Table 1.1 of the IERS Conventions [Petit et al.
2010]).

3.2 Solid Earth tide systems
Concerning the tide system the IAG resolution No. 16(1983) states that for the uniform treatment of tidal
corrections to various geodetic quantities such as gravity and station positions, the indirect eﬀect due to thepermanent yielding of the Earth shall not be removed[IAG 1984].

3.3 Geopotential value W0

1109

Table 3.1: Numerical standards given in different sources. The fundamental parameters of [Groten 2004]
give the equatorial radius not only in the mean-tide system, but also in the zero-tide and tide-free system (thecorresponding values are displayed in brackets). Please note that various factors have to be considered for acomparison of the values (see explanations in this section).

Quantity

GRS80(Moritz
2000)

Fundamental
Parameters(Groten
2004)

IERS2010(Petit andLuzum,
2010)

Gravit. constant (GM )– TCG-compatible value– TT-compatible value

398.6005

398.6004418

398.6004418

Equatorial radius (a)– zero-tide value– mean-tide value– tide-free value

EGM2008(Pavlis etal. 2012)

Unit[1012 m3 s−2 ]398.6004415

6378136.6

6378137.0(6378136.62)
6378136.7(6378136.59)

Dyn. form factor (J2 )– zero-tide value1082.631082.6359

1082.6359

1082.6361[10−6 ]

Mean angularrotation velocity (ω)

7.292115

7.292115

7.292115

7.292115[10−5 rad s−1 ]In the geodetic community the following diﬀerent tidal
systems are in use and have to be distinguished (see[Denker 2013; Mäkinen et al. 2009; Petit et al. 2010]:– In the mean-tide system only the periodic tidal eﬀects
are removed from the positions, but the permanentparts (both direct and indirect) are retained.
– The zero-tide system is the one recommended by IAG.
In this system, the periodic tidal eﬀects and direct
permanent eﬀects are removed completely, but theindirect deformation eﬀects associated with the permanent tide deformation are retained.
– In the tide free system (or non-tidal system), the total tidal eﬀects (periodic and permanent, direct andindirect) have been removed with a model. In thiscase, the required (unobservable) ﬂuid Love numbers
have to be adopted by conventional values.
– The conventional routine for the evaluation of solid
Earth tides computes tidal displacements as a sum of
a frequency-independent closed form and a series offrequency-dependent corrections. The closed form includes a permanent tide which is wrongly multipliedwith the nominal elastic Love number. Since for along time the reduction of the wrong permanent partwas disregarded, a separate tidal system was created
which is now called conventional tide free system.
For geodetic products diﬀerent tidal systems are being
used. While the gravimetric services provide products
mostly in the zero-tide system, in agreement with IAG
resolution 16 of the 18th General Assembly 1983, the geometric services provide their products, e.g., the ITRF,
in the conventional tide free system. However, the ITRF
has adopted, by convention, the same tide system as the[m]6378136.3

technique analysis centers. If the users need anothertide system representation, the IERS Conventions provide the necessary conversion formulas in Chapter 7. In
applications involving satellite altimetry, the mean-tidesystem is commonly used.

3.3 Geopotential value W0
Per deﬁnition, W0 is understood as the value of thegravity potential of the Earth on a particular equipotential surface called the geoid. Since the Earth’s gravity
potential ﬁeld contains an inﬁnite number of equipotential surfaces, the geoid is to be deﬁned arbitrarily by
convention. The usual convention follows the deﬁnition
given by Gauss [1876] and Listing [1873]: The geoid isthe equipotential surface that best fits (in a least square
sense) the undisturbed mean sea level. As this condition
cannot be satisﬁed due to diﬀerent causes (like existence of the continents, oceanic currents, atmosphericpressure eﬀects, external gravity forces, etc.) an additional convention about the mean sea level is required.
This convention shall consider not only the reductions
applied to remove disturbing eﬀects, but also the timespan and the location where the sea surface level shallsatisfy the Gauss-Listing deﬁnition. It can be realized
over diﬀerent time spans at a local tide gauge, or as
average from several tide gauges, or over the ocean areas sampled globally [see, e.g., Ekman 1995; Heck 2004;
Heck et al. 1990; Mather 1978].
As a reference level for the determination of verticalcoordinates, W0 deﬁnes the scale (size) of the reference (zero-height) surface with respect to the Earth’s

1110

Inventory of Standards and Conventions: 3 Evaluation of numerical standards

body (i.e., it deﬁnes the vertical datum of a height system). As a parameter of the gravity ﬁeld, W0 may berequired for the transformation between the time scales
TCG and TT (see equations 3.1 and 3.3); and it can be
introduced as a primary parameter for the deﬁnitionof a reference mean Earth ellipsoid; i.e., a level ellipsoid that best ﬁts the geoid. Local realizations of W0(i)(i.e. W0 ) are enough for the determination of vertical coordinates referring to a local height system i. For
the transformation between TCG and TT and in thecase of a worldwide uniﬁed vertical reference system, a
global estimation of W0 is required. Usually, this was
performed by assuming W0 equivalent to the normal potential U0 generated by a mean Earth ellipsoid (like the
GRS80). Today, the estimation of a global W0 is basedon the combination of mean sea surface models derived
from satellite altimetry observations and the Earth’s
gravity ﬁeld modeling derived from space techniques,in particular low Earth orbiting satellites like GRACE,
GOCE, and the satellites for laser ranging observations
like LAGEOS, ETALON, etc. [e.g., Burša et al. 2007;
Dayoub et al. 2012; Sánchez 2012; Sánchez et al. 2014].
At present, there are three diﬀerent global reference
geopotential values (see Table 3.2): the ﬁrst one corresponds to the normal potential U0 of the GRS80 ellipsoid [Moritz 2000], the second one is that value includedin the IAU standards (and also in the IERS conventions), and the third one is the conventional W0 value
adopted by the IAG as the reference level for the deﬁnition and realization of the International Height Reference System, IHRS [IAG resolution No. 1, 2015]. The
IAU standards [Luzum et al. 2011] and the IERS Conventions 2010 [Petit et al. 2010] include a W0 value,
since the initial deﬁnition of the constant LG (see equations 3.1 and 3.2) was given by
LG = W0 /c2 ,(3.3)

c beeing the speed of light (cf. IAU recommendation IV,
1991, and IAU resolution B 1.9, 2000). Consequently,
after the introduction of the timescales TCG and TT
in 1991, LG was recomputed always when a new best
estimate for W0 was available (see Table 3.3). In the
IAU General Assembly of 2000, it was decided to declare LG as a deﬁning constant (IAU resolution B1.9,
2000); i.e., it should not change with new estimationsof W0 . A W0 value was maintained as an IAU/IERS
standard, although it is not more needed by the IAU or
the IERS. As matter of fact, the LG value applied atpresent by the IAU and the IERS is based on the W0
value recommended by [Groten 1999] and further mentioned by [Groten 2004]. The primary reference for thecomputation of that W0 value is dated in 1998 [Burša etal. 1998]; i.e., it corresponds to the best estimate available in 1998. This value (62 636 856.0 m2 s−2 ) is usuallycalled the IERS W0 value, although the IERS did notparticipate in its determination.
The IAG conventional W0 value (62 636 853.4 m2 s−2 )relies on the newest (as of 2013) gravity ﬁeld and sea
surface models and its computation is supported by detailed conventions considering [see Sánchez et al. 2015]:(1) sensitivity of W0 to the Earth’s gravity ﬁeld modeling (especially omission and commission errors andtime-dependent Earth’s gravity ﬁeld changes); (2) sensitivity of W0 to the mean sea surface modeling (e.g.
geographical coverage, time-dependent sea surface variations, accuracy of the mean sea surface heights); (3)dependence of W0 on the tide system; and (4) weighted
computation based on the input data quality. According to Ihde et al. [2015], W0 is deﬁned to be timeindependent (i.e. quasi-stationary) and it shall remain
ﬁxed for a long-term period (e.g. 20 years). However,it has to have a clear relationship with the mean sea
surface level as this is the convention for the realization of the geoid. Therefore, a main recommendation
after adopting this conventional W0 value is to monitor
the changes of the mean potential value at the sea surface WS . When large diﬀerences appear between W0
and WS (e.g. > ±2 m2 s−2 ), the adopted W0 may bereplaced by an updated (best estimate) value [Sánchez
et al. 2015]. This monitoring shall consider not only sea
level changes, but also mass redistribution eﬀects associated to temporal variations of the gravity potential.

3.4 Open problems andrecommendations
As outlined in Section 3.1, there are currently diﬀerent
numerical standards in use within the geodetic community. The GRS80 values are still used as oﬃcial ellipsoidparameters, although they are not truly representing
reality anymore. The numerical standards of the IERS
Conventions 2010, which are based on the best estimates of [Groten 2004], are commonly used for the processing of the geometric observations and for the generation of IERS products. The fact that the semi-major
axis between GRS80 and IERS Conventions 2010 diﬀers
by 0.4 m is critical and has to be considered correctly
for users of geodetic products. Moreover, diﬀerent standards are used within the gravity community, and they
are also partly diﬀerent from the numerical standards
given in the IERS Conventions.

3.4 Open problems and recommendations

1111
Table 3.2: Global reference geopotential values.

W0 [m2 s−2 ]Comments

References

62 636 860.850
62 636 856.0

GRS80 (W0 = U0 )IERS Conventions 2010 (best W0 estimate in 1998),
Topex/Poseidon (1993–1996), EGM 96
Conventional IAG value (best W0 estimate in 2015,
mean sea surface (1993–2013) from multi-mission
cross-calibration of several satellite altimeters,
and gravity field modeling based on SLR, GRACE,
and GOCE data

[Moritz 2000][Petit et al. 2010]

62 636 853.4[Sánchez et al. 2015]

Table 3.3: Values of the constant LG according to new best estimates of W0 . In 2000 LG was declared to be a defining constant.
Year

W0 [m2 s−2 ]

LG

1991

62 636 860 ± 30
[Chovitz 1988]

6.969 291 · 10−10 ± 3 · 10−16(IAU recommendation IV, note 6, 1991)

1992

62 636 856.5 ± 3

6.969 290 19 · 10−10 ± 3 · 10−17

1995[Burša et al. 1992]
62 636 856.85 ± 1[Burša 1995]

6.969 290 3 · 10−10 ± 1 · 10−17

1999

62 636 856.0 ± 0.5[Groten 1999][Fukushima 1995][McCarthy 1996, Tab. 4.1]

6.969 290 134 · 10−10 (as defining constant)(IAU resolution B1.9, 2000)

The current situation concerning numerical standards
and the diﬀerent use of time and tide systems is a potential source for inconsistencies and even errors of geodetic products. Thus, it is essential for a correct interpretation and use of geodetic results and products that theunderlying numerical standards be clearly documented.
Moreover, if geodetic results are combined that are expressed in diﬀerent time or tide systems, transformations have to be performed to get consistent results.
Another issue concerning time systems was brought up
by J. Gipson during the last GGOS Uniﬁed Analysis
Workshop in Pasadena (June 2014). At present, different space techniques and sometimes also diﬀerent
groups working within the same technique have diﬀerent time systems, for example GPS time vs. UTC. The
oﬀset between the diﬀerent systems does not aﬀect thecomparison of most geodetic parameters. However if theparameter is rapidly varying, such as ∆UT1, then it isimportant that the comparisons are done at the same
epoch. Thus it is recommended at a minimum that allscientists are clear and explicit about what time-tags
they are using. In a perfect world the same time-tags
should be used by everyone.
Concerning the tide systems the foundations of the IAG
Resolution No. 16 (1983) are still valid. The recommended zero tide system is the most adequate system
for gravity acceleration and gravity potential of the rotating and deforming Earth. However, for the terrestrialreference system parameters the conventional tide free

concept is used for decades, although the tide free crust
is far away from the real Earth shape and it is unobservable. In the past, there have been several discussions on
the tide system for the terrestrial reference frame. Dueto practical reasons it was decided that it shall not bechanged. But even if this conventional tide free concept
is kept also in the future, the zero tide system shall be
used for gravity and geopotential.
The IAG resolution No. 1 (2015) provides the basic conventions for the deﬁnition of an International Height
Reference System (IHRS), being the IAG conventional
W0 value a fundamental parameter. The IAG conventional W0 value and the so-called IERS W0 value diﬀer
by −2.6 m2 s−2 , corresponding to a level diﬀerence ofabout 27 cm. To avoid confusion among users of geodetic products, it is necessary to present only one W0
global reference value. It is clear that the relationshipbetween TCG and TT does not depend anymore on thegeoid deﬁnition, since LG was declared as a deﬁning
constant. However, it is desirable that the IAU Standards and the IERS Conventions include the IAG conventional W0 value instead of the 1998 value recommended by [Groten 1999, 2004]. The main implicationof a new W0 value for the IAU/IERS timescales is related to the accuracy in the realization of the International Atomic Time (TAI). It presently corresponds
to a coordinate timescale defined in a geocentric reference frame with the SI second as realized on the rotating geoid as the scale unit. Therefore, TAI still has areference to the geoid (W0 ), while TT does not have

1112

Inventory of Standards and Conventions: 3 Evaluation of numerical standards

it anymore. This is a potential source of inconsistency
because it is usually considered that TAI is a realization of TT. However, a redeﬁnition of the TAI scaleconsidering the IAG conventional W0 value will be required when the clock accuracy (i.e. timescale accuracy)
reaches about 7 · 10−17 to 9 · 10−17 . The best possible
accuracy today is about 2 · 10−16, which corresponds toa potential diﬀerence accuracy of about 20 m2 s−2 ; i.e.,ten times larger than the diﬀerence between the IAG
conventional W0 value and the IERS W0 value [Petit,
2015, pers. communication]. In any case, the reformulation of the TAI deﬁnition is under the responsibility of the General Conference of Weights and Measuresthrough the Consultative Committee on Time and Frequency.
In the future, the development of a new Geodetic Reference System based on a consistent system of best estimates of major parameters related to a geocentric level
ellipsoid shall be considered. This should involve thecollection of best estimates including uncertainties anda documentation of the parameter estimation, and thecomputation of derived parameters. According to its
Terms of Reference, the BPS shall take the responsibility for this task involving all experts in the ﬁeld.

Summary of recommendations on numerical standards:
Recommendation 0.1 : The used numerical standards
including time and tide systems must be clearly documented for all geodetic products.
Recommendation 0.2 : Astronomical, geodetic or
geophysical standards including or requiring a W0
reference value should adopt the IAG conventional
W0 value issued by the IAG resolution No. 1 (2015),
i.e. W0 = 62 636 853.4 m2s−2 .
Recommendation 0.3 : A new Geodetic Reference
System GRS20XX based on a consistent estimationof best estimates of the major parameters related toa geocentric level ellipsoid should be developed.

4.1 Celestial reference systems and frames

1113

4 Product-based review of standards and conventions
This chapter focuses on the assessment of the standards
and conventions currently adopted and used by IAG
and its components for the generation of IAG products.
With the compilation of such a product-based inventory,
the BPS supports GGOS in its goal to obtain consistentgeodetic products and it provides also a fundamental
basis for the integration of geometric and gravimetricparameters, and for the development of new products.
GGOS as an organization is built on the existing IAG
Services, and under this “unifying umbrella”, all the
products provided by the diﬀerent IAG Services are
considered GGOS products. This declaration and also
Section 7.5 “Products available through GGOS ” fromthe GGOS publication [Plag et al. 2009] serve as thebasis to specify the major products of IAG and GGOS,
addressing the following topics:
Section 4.1 Celestial reference systems and frames,
Section 4.2 Terrestrial reference systems and frames,
Section 4.3 Earth orientation parameters,
Section 4.4 GNSS satellite orbits,
Section 4.5 Gravity and geoid,
Section 4.6 Height systems and their realizations.
The sections for each of these products (or topics) wereorganized in a similar structure. The ﬁrst part givesa brief overview, followed by a description and discussion of the present status, and ﬁnally open issues are
identiﬁed and recommendations are provided. Despiteof this similar structure, the character of these sections
is partly diﬀerent as a consequence of the current situation regarding the availability of IAG products in thediﬀerent ﬁelds and organizational issues of the IAG Services. IAG products exist for the celestial and terrestrial reference frame (Sections 4.1 and 4.2) as well as
for the EOP (Section 4.3) which are provided by the
responsible Product Centers of the IERS. The GNSS
satellite orbits addressed in Section 4.4 are provided by
the IGS. This technique-speciﬁc product was includedin the inventory, since the GNSS orbits are used fora wide range of applications. For the gravity ﬁeld andgeoid (Section 4.5) as well as for the height systems
and their realizations (Section 4.6), oﬃcial IAG products still need to be deﬁned and implemented. Due tothis fact the character of these two corresponding sections diﬀers from the others.
It should also be noted, that this list of topics and IAG
products is by far not complete and it can be extended
by adding other products in an updated version of thisdocument. Furthermore, the ongoing GGOS activities

towards the development of integrated products will
have to be considered in a future version of such an
inventory.

4.1 Celestial reference systems andframes
4.1.1 Overview
By the nature of this topic, the IAU has always been
responsible for celestial reference systems and celestialreference frames. However, in the course of technological development many more organizations and working groups have been involved in the more recent past
where observations in the radio frequency regime havesuperseded optical observations. Due to its dominating
volume of observations, the International VLBI Service
for Geodesy and Astrometry (IVS) [Schuh et al. 2012]
was the key supplier of observations and analysis capability in the recent past. The IVS was established in
1999 as an international collaboration of organizations
operating or supporting VLBI components to support
geodetic and astrometric work on reference systems andEarth science research by operational activities. Due tothe basics of its technique, the IVS is a joint service of
IAG and IAU. On the IAG side, the IVS represents the
VLBI technique in GGOS and interacts closely with the
IERS, which is tasked by IAU and IUGG with maintaining the ICRF and ITRF, respectively.
As a result of this organizational structure, the IAG,
through IVS, has an indirect responsibility for the celestial reference frame at radio frequencies. The VLBI
data provide the direct link between the celestial andthe terrestrial reference frame, and, at the same time,
determines the Earth orientation parameters. Since theconsistency between both frames is an important issue
that should be addressed by the scientiﬁc community(see IUGG Resolution No. 3, 2011), the topic is subjectof this inventory.
The IAU resolution No. B2 from the IAU General Assembly in 1997 resolved (a) that as from 1 January 1998,
the IAU celestial reference system shall be the International Celestial Reference System (ICRS) as speciﬁedin the 1991 IAU Resolution on reference frames andas deﬁned by the IERS [Arias et al. 1995]; (b) thatthe corresponding fundamental reference frame shallbe the International Celestial Reference Frame (ICRF)

1114

constructed by the IAU Working Group on reference
frames; (c) that the Hipparcos Catalogue shall be theprimary realization of the ICRS at optical wavelengths;and (d) that the IERS shall take appropriate measures,in conjunction with the IAU Working Group on reference frames, to maintain the ICRF and its ties tothe reference frames at other wavelengths. According
to this IAU resolution, the ICRS has been realized by
the ICRF since January 1, 1998, which is based on theradio wavelength astrometric positions of compact extragalactic objects determined by VLBI.
The IERS has been charged with the responsibility ofmonitoring the ICRS, maintaining its realization, theICRF, and improving the links with other celestial reference frames. Since 2001, these activities have been
run jointly by the ICRS Center (at the Observatoirede Paris and the US Naval Observatory) of the IERS
and the IVS, in conjunction with IAU (see e.g., IERS
Annual Report 2010 [Souchay et al. 2013]).

4.1.2 International Celestial Reference System
Following the IAU Resolution B2 (1997), the ICRS replaced the Fifth Fundamental Star Catalogue (FK5)as the fundamental celestial reference system for astronomical applications. The ICRS is an idealized Barycentric Celestial Reference System (BCRS), with its axes
kinematically non-rotating with respect to the distantobjects in the universe [Petit et al. 2010]. These axes
are deﬁned implicitly through the set of coordinates ofextragalactic objects, mostly quasars, BL Lac sources
and a few Active Galactic Nuclei (AGN), as determinedin the most precise realization of the ICRS, the ICRF
(for more information see [Petit et al. 2010]).
The recommendations of the IAU Resolution A4 (1991)
specify that the origin of the ICRF is to be at thebarycenter of the solar system and the directions of its
axes should be ﬁxed with respect to the quasars. It isfurther recommended that the celestial reference system has its principal plane as close as possible to themean equator at J2000.0 and the origin of this principal plane was close as possible to the dynamic equinoxof J2000.0. The VLBI observations used to establish
the extragalactic reference frame are used to monitor
the motion of the celestial pole in space. In this way,
the VLBI analyses provide corrections to the conventional IAU models for precession and nutation (see Section 4.3).

Inventory of Standards and Conventions: 4 Product-based review

4.1.3 International Celestial Reference Frames
4.1.3.1 History of ICRS realizations
The initial realization of the IERS Celestial Reference
System, RSC(IERS) 88 C01 [Arias et al. 1988] contained 228 extragalactic radio sources in total. Thisﬁrst catalogue was computed by combining the VLBI
solutions of three US agencies (Goddard Space Flight
Center (GSFC), Jet Propulsion Laboratory (JPL) andNational Geodetic Survey (NGS)). In the adjustment
process the right ascension of the source 3C273B was
ﬁxed to its conventional FK5 value [Hazard et al. 1971].
23 out of the 228 radio sources were chosen to deﬁne
the axes directions of this ﬁrst frame. This initial realization can be considered as the intangible basis of
the celestial frame, since all subsequent realizations directly or indirectly refer to this initial set of coordinate
axes. Between 1988 and 1994, several celestial reference
frames were determined on a regular basis following theﬁrst one, all of which were referred to the respective previous realization of ICRS by No Net Rotation (NNR)
constraints.
As speciﬁed in the IAU Resolution No. 2 (1997), theICRF, i.e. the ﬁrst realization of the ICRS, is basedon the positions of extragalactic objects measured by
VLBI. Adopted by the IAU Working Group on Reference Frames (WGRF), it was determined by the VLBI
solution of the GSFC at National Aeronautics and Space
Administration (NASA) [Ma et al. 1998, 1997]. The catalogue provides the positions and uncertainties of 608
radio sources, including 212 deﬁning sources used forthe global NNR condition, to realize the axes of the
ICRF [Arias et al. 1990] with respect to previous IERS
celestial reference frames [Arias et al. 1991; Ma et al.
1997].
There were two extensions of ICRF: ICRF-Ext. 1 [Gambis 1999] and ICRF-Ext. 2 [Fey et al. 2004]. For both
extensions the original ICRF positions of the deﬁning
sources remained unchanged, thus preserving the initial
ICRF orientation ﬁxed.
4.1.3.2 The current realization, the ICRF2Within the common IAU/IVS Working Group entitled“The Second Realization of the International Celestial
Reference Frame – ICRF2 ” a new version of ICRF has
been computed [Fey et al. 2009, 2015], which was accepted by the IAU at its General Assembly in Rio deJaneiro, Brazil, in August 2009 (see IAU Resolution
No. B3, 2009) and by IUGG Resolution No. 3 (2011). It
contains the positions of 3414 compact radio sources,

4.1 Celestial reference systems and frames

including a selected set of 295 deﬁning sources. The
stability of the axes is approximately 10 µas, making
ICRF2 nearly twice as stable as its predecessor, also accompanied by an improved noise level of about 40 µas
and a more uniform sky distribution including more
deﬁning sources on the southern hemisphere.
The overall characteristics of the ICRF2 solution are described in [Fey et al. 2009, 2015]. The a-priori models
for geophysical eﬀects and precession/nutation used forthe ICRF2 computations generally followed the IERS
Conventions 2003 [McCarthy et al. 2003]. Speciﬁcally,corrections for solid Earth tides, the pole tide, ocean
loading, and high frequency EOP variations were madeusing the IERS Conventions 2003. Other important effects were modeled using– Atmosphere pressure loading corrections according
to Petrov et al. [2004],– The Vienna Mapping Function (VMF1) tropospheremodel of Böhm, Werl, et al. [2006],– The antenna thermal deformation model of Nothnagel [2009],– A-priori gradients model according to MacMillan etal. [1997].
4.1.3.3 Recent and future developments
Recently, the IAU Division A Working Group entitled“Third Realization of the International Celestial Reference Frame (shortly ICRF 3)” has been formed. The
aim of the IAU WG is to compute and present the next
ICRF3 to the IAU General Assembly in 2018. The developments are supported by the IAG Sub-Commission
1.4 “Interaction of Celestial and Terrestrial Reference
Frames”. Improvements are foreseen by the inclusionof observations at higher radio frequencies and a possible radio-optical link with ESA’s optical astrometry
mission Gaia.

1115

4.1.4.2 ICRS definition and its realization
The deﬁnition and realization of the ICRS are given in
the IERS Conventions [Petit et al. 2010] on the basis ofseveral IAU resolutions. The IAU Resolution A4 (recommendation VII, 1991) recommends under (1) “thatthe prinicipal plane of the new conventional celestial reference frame be as near as possible to the mean equator
at J2000.0 and that the origin of the principal plane be
as near as possible to the dynamical equinox of J2000.0 ”.
These rather imprecise deﬁnitions result from the factthat old realizations were usually not as precise as thecurrent conventional deﬁnition. A series of ICRS realizations has been computed so far, and in each of thosethe datum has been deﬁned with respect to the previous
realization by applying NNR conditions. But this is depending on the quality, number and distribution of thedeﬁning radio-sources used in the NNR condition. By
applying this procedure, inconsistencies of the predecessor can aﬀect the reference frame deﬁnition (mainly
the orientation) of new (more precise) frames.
4.1.4.3 ICRF computations
Both, ICRF and ICRF2, have been computed by only
one IVS Analysis Center using a single software package and thus, this individual solution is not controlled
through a combination process of several software packages and combination strategies. Currently, formal errors of the ICRF determined by VLBI are probably
too optimistic since they do not take into account uncertainties of a number of technique-speciﬁc parameters. Examples are antenna axis oﬀsets, thermal expansion modeling, inﬂuences of uncertain technique-speciﬁcmodel components and source structure eﬀects. Moreover, the imbalance of VLBI observatories on the northern and the southern hemisphere is not quantiﬁed at all.
4.1.4.4 Consistent estimation of the ICRF, ITRF andEOP

4.1.4 Discussion of the present status
4.1.4.1 General issues
The organizational structure regarding the deﬁnition
and realization of the celestial reference system is rather
complex. Quite a large number of organizations, services and other entities are involved. Although the responsibilities for the deﬁnition of the ICRS and themaintenance of the ICRF are resolved in the IAU resolutions (see Sections 1.2.4 and 4.1.1), the complex structure in this ﬁeld requires an eﬃcient and regular exchange of information to ensure eﬀectiveness of the work.

The IUGG Resolution No. 3 (2011) recommends, thatthe highest consistency between the ICRF, the ITRF
and the EOP as observed and realized by IAG and its
components such as the IERS should be a primary goalin all future realizations of the ICRS. At present, both
frames (the ICRF and ITRF) and their integral EOP
solutions are not fully consistent with each other as they
are computed independently by separate IERS ProductCenters. Although the IUGG recommendation has notbeen fulﬁlled yet, studies in this direction have been initiated, e.g. DGFI has performed a simultaneous estimation of CRF, TRF and EOP series [M. Seitz et al. 2014].

1116

On the international level, this topic is addressed by the
IAU Working Group “ICRF 3 ” and by the IAG SubCommission 1.4 “Interaction of celestial and terrestrialreference frames”. This topic was also addressed at the
IERS Retreat in Paris 2013 (see www.iers.org/IERS/
EN/Organization/Workshops/Retreat2003.html).
The recommendations of this IERS Retreat provide somerelevant questions related to this issue (see Section 4.1.6).

4.1.5 Interaction with other products
Through the VLBI observations there is a direct link of
the celestial reference frame with– Terrestrial reference frames and– Earth orientation parameters.
The interactions of the ICRF with the ITRF and EOP
also provide indirect links to the dynamic reference
frames of satellite orbits and to other parameters, which
are derived from the mentioned products.

4.1.6 Open problems and recommendations
4.1.6.1 General issue on ICRS/ICRF
As a consequence of the complex organizational interactions, the current ICRF has to be considered a joint
IAU/IAG product. Therefore, this product is part ofthis inventory. It helps to address important scientiﬁcquestions, like the consistency between the celestial andterrestrial frame. Moreover, the objectives and goalsof GGOS require not only an Earth-ﬁxed frame, butalso the link to an inertial frame and the interactions
between both described by the EOP. The responsibleorganizations are asked to clarify in which way the
ICRS/ICRF may be labeled a GGOS product.

4.1.6.2 ICRF computations
It remains to be considered whether the next ICRS realization shall be estimated from a combination of different analysis center solutions computed with diﬀerent
software packages to ensure redundancy and a reliable
quality control of the ﬁnal product. The precision of thecoordinates of radio sources forming the ICRF steadily
gets better due to more accurate observations and improved analysis methods. Therefore, it shall be investigated if source position instabilities must be included.

Inventory of Standards and Conventions: 4 Product-based review

4.1.6.3 Consistency of ICRF, ITRF and EOP
Important questions taken from the recommendationsof the IERS Retreat 2013 are: (1) How consistent is the
ICRF with the ITRF and EOP? (2) Is the ICRF decoupled enough from the ITRF so that radio sources do notneed to be included in the ITRF computations and viceversa? (3) What is the gain if ICRF, ITRF and EOP are
estimated in a common adjustment? It is recommended
that these questions should be addressed to the IAU
WG “ICRF 3 ” and to the IAG Sub-Commission 1.4 “Interaction of celestial and terrestrial reference frames”.
Moreover groups that can do these studies are encouraged to contribute.
Summary of recommendations on ICRS/ICRF:
Recommendation 1.1 : The responsible organizations
are asked to clarify in which way the ICRS/ICRF
may be labeled a GGOS product.
Recommendation 1.2 : It should be considered by theorganizations and their responsible working groups,
whether the next ICRS realization, the ICRF3, shouldbe estimated from a combination of diﬀerent analysis center solutions, as well as of diﬀerent observing
frequencies.
Recommendation 1.3 : Research groups are encouraged to perform the previously mentioned studies regarding the consistency of ICRF, ITRF and EOP.

4.2 Terrestrial reference systems andframes
4.2.1 Overview
A Terrestrial Reference System (TRS), also denoted as
Earth-ﬁxed global reference system, is a spatial reference system co-rotating with the Earth, in which points
at the solid Earth’s surface undergo only small variations with time. These variations are mainly due togeophysical eﬀects caused by various dynamic processes
and forces from external bodies. In the nomenclature,
we distinguish between a reference system, which isbased on theoretical considerations and conventions,and its realization, which is called the reference frame(see, e.g., [Kovalevsky et al. 1989], IERS Conventions
2010 [Petit et al. 2010]).
Terrestrial reference frames (TRF) are needed to refer
the geodetic observations and estimated parameters toa unique global basis. High accuracy, consistency andlong-term stability is required for precisely monitoring4.2 Terrestrial reference systems and frames

global change phenomena as well as for precise positioning applications on and near the Earth’s surface.
The importance of geodetic reference frames for manysocietal and economic beneﬁt areas has been recognizedby the United Nations too. In February 2015, the UN
General Assembly adopted its ﬁrst geospatial resolution ”A Global Geodetic Reference Frame for Sustainable Development ” (see www.un.org/en/ga/search/
view_doc.asp?symbol=A/RES/69/266
andwww.
unggrf.org/).
The ITRS has been formally adopted and recommended
for Earth science applications [IUGG 2007]. The IERS
is in charge of deﬁning, realizing and promoting the
ITRS. Deﬁnition, realization and promotion of the ITRS
is the responsibility of the IERS. The regularly updated
IERS Conventions (latest version [Petit et al. 2010])
serve as the necessary basis for the mathematical representation of geometric and physical quantities.
The International Terrestrial Reference Frame (ITRF)
is a realization of the ITRS, consisting of three-dimensional positions and time variations (e.g., constant velocities) of IERS network stations observed by space
geodetic techniques. Currently the contributing spacetechniques are VLBI, SLR, GNSS and DORIS.
Realizations of the ITRS are published by the ITRS
Center hosted at the Institut National de l’Information
Géographique et Forestiere, France (IGN). Within the
re-organised IERS structure (since 2001), the ITRS Center (formally called ITRS Terrestrial Reference Frame
Section) is supplemented by ITRS Combination Centers which were included as additional IERS components to ensure redundancy for ITRF computations andto allow for a decisive validation and quality control of
the combination results. ITRS Combination Centers are
established at DGFI, IGN, and since 2012 at the JPL
in Pasadena (USA).
Until now, twelve releases of the ITRF were publishedby the IERS, starting with ITRF 88 and ending with
ITRF 2008, each of which superseded its predecessor(see Chapter 4 of the IERS Conventions 2010, [Petit etal. 2010]). An updating of ITRS realizations was performed every few years, since the tracking networks ofspace techniques are evolving, the period of data extends, and also the modeling and data analysis strategies as well as the combination methods were improved
with time. Furthermore, large earthquakes can aﬀect
station positions and velocities over large regions. Up
to ITRF 2000, long-term global solutions (comprisingstation positions and velocities) from four techniques(VLBI, SLR, GNSS and DORIS) were used as input

1117

for the ITRF generation. Starting with ITRF 2005, the
ITRF computations were based on time series of station positions and EOP including variance-covarianceinformation from each of the techniques’ combination
centers.
The next section provides a brief summary about thecurrent ITRS realization, the ITRF 2008. Please note,at the time when this document was prepared for publication in the IAG’s geodesists handbook (status: January 15, 2016), the computations for the ITRF 2014
were almost ﬁnalized. It is expected that the ITRF 2014
will be released by the ITRS Center early 2016 and it
will then replace the ITRF 2008.
4.2.2 The current ITRS realization, the
ITRF 2008
The ITRF 2008 is the current realization of the ITRS
based on reprocessed solutions of the four space techniques VLBI, SLR, GNSS and DORIS [Altamimi etal. 2011]. The input data used for its elaboration aretime series of station positions and daily EOP. The
data were reprocessed by several individual analysis
centers for the diﬀerent space techniques according to
the speciﬁcations given in the ITRF 2008 call for participation. It was speciﬁed that the input data shallconform to the IERS Conventions 2003 (the up-to-dateversion at that time) [McCarthy et al. 2003]. The individual time series were combined per-technique by thefour responsible technique-speciﬁc combination centers,
namely the National Ressources Canada (NRCan) for
the IGS [Ferland 2010; Ferland et al. 2008], the IGG ofthe University Bonn, Germany, for the IVS [Böckmann
et al. 2010], the Agenzia Spaziale Italiana (ASI) for the
ILRS [Bianco et al. 2000; E. Pavlis et al. 2010] and theCollecte Localisation par Satellite (CLS) in cooperation
with the Center National d’Etudes Spatiales (CNES),
France, and GSFC at NASA, USA, for the IDS [Valetteet al. 2010]. A summary of the input ﬁles is given on
the ITRF web site: http://itrf.ensg.ign.fr/ITRF_
solutions/2008/input_data.php.
Table 4.1 summarizes the major characteristics of the
ITRF 2008 input data. We should recall that the ITRF
2008 input data are resulting from an intra-technique
combination of individual solutions provided by 11 ACs
in the case of GNSS and 7 ACs for the other techniques.
To ensure consistency of the ITRF 2008 input data, allcontributing ACs are supposed to use common processing standards and models for the data analysis.
Two solutions were computed by the ITRS Combination Centers at IGN and DGFI. The method of theInventory of Standards and Conventions: 4 Product-based review

1118

Table 4.1: Input data sets for ITRF 2008 (TC: Techniques’ Combination Center, NEQ:
constraint-free normal equation, AC: Analysis Center). In addition also geodetic local tie
information is used as input for the ITRF computations.
TechniqueService / TC# ACs
per technique

Data

Time period

GNSS
VLBI
SLR
DORIS

IGS/NRCan
IVS/IGG
ILRS/ASI
IDS/CLS-CNES-GSFC

11
7
7
7

Weekly solutions
24 h session NEQ
14/7 day solutions
Weekly solutions

1997.0 – 2009.0
1980.0 – 2009.0
1983.0 – 2009.0
1993.0 – 2009.0

IGN works on the solution level by a simultaneous estimation of similarity transformation parameters withrespect to the combined frame along with the adjustment of station positions, velocities and EOP [Altamimi
et al. 2011]. The strategy applied at DGFI is based on
the normal equation level. The station positions, velocities and EOP are estimated in a common adjustment[Angermann et al. 2009; M. Seitz et al. 2012]. Despitesome diﬀerences between both strategies, the generalprocedure for the ITRF 2008 computation is very similar.
The procedure is based on two main steps:– The accumulation (stacking) of the time series pertechnique to generate technique-speciﬁc solutions or
normal equations.
– The combination of the per-technique solutions or
normal equations.
The ITRF 2008 solution computed at IGN was releasedby the ITRS Center as the oﬃcial ITRF2008 [Altamimi
et al. 2011]. All ITRF 2008 data ﬁles and results areavailable at the ITRF web site itrf.ign.fr/ITRF_
solutions/2008/.
The ITRF 2008 solution computed at DGFI is labelled
as DTRF 2008 [M. Seitz et al. 2012]. This solution isavailable at the anonymous ftp server of DGFI ftp.
dgfi.tum.de/pub/DTRF2008.
A comparison between the DTRF 2008 and ITRF 2008
has been performed by DGFI to quantify the diﬀerence
between these two realizations [M. Seitz et al. 2012,2013]. The comparisons were done technique-wise by
performing similarity transformations in order to investigate the level of agreement for the datum parameters
as well as for the station positions and velocities. With
respect to the datum parameters, the two realizations
show an overall agreement in the order of 5–6 mm. The
RMS diﬀerences for the station positions and velocities
are given in Table 4.2. However, the results of this comparison do not fully reﬂect the overall accuracy of theterrestrial reference frame, since both realizations are
based on identical input data and the impact of various

eﬀects (e.g., non-linear station motions) is not considered. The current ITRF results indicate that the GGOS
requirements are not achieved yet. According to [Plaget al. 2009] the terrestrial reference frame should to beaccurate at a level of 1 mm and to be stable with time
at a level of 0.1 mm/yr.
The topic of an external evaluation of the terrestrial reference frames is mainly studied within a speciﬁc Working Group of IAG Sub-Commission 1.2, the WG 1.2.1“External Evaluation of Terrestrial Reference Frames”[Collilieux et al. 2014]. The aim of this task force isto review all methods that allow evaluating the accuracy of a TRF. Methods that involve data sets thathave not been used in the TRF computation will beespecially emphasized (e.g., tide gauges, gravity, geophysical models).

4.2.3 Discussion of the present status
4.2.3.1 ITRS definition vs. its realization
According to the IERS Conventions [Petit et al. 2010]
the ITRS deﬁnition fulﬁls the following principles:– It is geocentric, the center of mass being deﬁned forthe whole Earth, including oceans and atmosphere;– The unit length is the meter (SI). This scale is consistent with the TCG time coordinate for a geocentric
local frame, in agreement with IAU and IUGG (1991)
resolutions;
Table 4.2: RMS values of the similarity transformation between DTRF 2008 and ITRF 2008
at the reference epoch 2005.0.
Techniquepositions[mm]velocities[mm/yr]

GNSS
VLBI
SLR
DORIS

1.33
0.38
2.02
3.22

0.19
0.09
0.82
0.98

4.2 Terrestrial reference systems and frames– Its orientation was initially given by the Bureau International de l’Heure (BIH) orientation of the BIH
Terrestrial System (BTS) at epoch 1984.0;– The time evolution of the orientation is realized byusing a no net rotation (NNR) condition with regard
to horizontal tectonic motions over the whole Earth.
In the following we compare the ITRS deﬁnition with
its realization:
Origin: The ITRF origin is realized by SLR observations. Through the orbit dynamics SLR determines
the Center of Mass (CM). According to the IERS
Conventions 2010 [Petit et al. 2010] the ITRF origin should be considered as the mean Earth center ofmass, averaged over the time span of SLR observations used and modeled as a secular (linear) function
in time. It can be regarded as a crust-based TRF withthe origin realized as a mean CM [Blewitt 2003; Donget al. 2003; Petit et al. 2010; X. Wu et al. 2015]. In atruly CM-based frame, the SLR origin coincides with
CM not only in mean but at any epoch, if the station
coordinates and the satellite orbits are adjusted together and if the ﬁrst degree gravity ﬁeld coeﬃcientsare ﬁxed to zero. However, accessible for the user areat present only mean (linear) geocentric station coordinates due to the linear ITRF station motion model.
If an instantaneous geocentric position is required, it
is recommended in the IERS Conventions [Petit etal. 2010] (see Section 4.2.5) to substract the so-called
geocenter motion (i.e. the vector from the crust-based
ITRF origin to the instanteneous center of mass)from the ITRF position vector. However, the expression “geocenter motion” is deﬁned diﬀerently in thegeodetic literature [e.g., Dong et al. 2003], and moreover a commonly accepted model available to accountfor this eﬀect is not available yet. Although SLR is
the most precise observation technique to realize the
ITRS origin, it has to be considered that the SLR
results may be aﬀected by the so-called network effect due to a relatively sparse network and due to theblue-sky eﬀect if atmospheric loading is not considered [Collilieux et al. 2009].
Scale: The ITRS scale is speciﬁed to be consistent
with the TCG time coordinate (IAU and IUGG resolutions, 1991), whereas its realization is consistent
with the terrestrial time (TT). The diﬀerence between both time scales is about 0.7 · 10−9 (see Section 3.1), equivalent to a height diﬀerence of 4.5 mm
at the surface of the Earth. The ITRS scale is realized by SLR and VLBI observations and similar as forthe origin the results are aﬀected by relatively sparse
networks. As a result of the ITRF2008 combinations,
IGN found a scale diﬀerence between VLBI and SLR

1119

of 1.05 ppb at epoch 2005.0 [Altamimi et al. 2011].
This result could not be conﬁrmed by the DTRF2008
computations of DGFI [M. Seitz et al. 2012], that
resulted in a scale diﬀerence between 0.09 and 0.55
ppb. The authors argued that this uncertainty mainly
arises from the sensitivity of the scale realization withrespect to the handling of the local ties.
Orientation and its time evolution: The orientation of the coordinate axes of the reference frame
could, theoretically, also be deﬁned by the Earth’s
gravity ﬁeld, namely the second degree spherical harmonic coeﬃcients which are related to the orientationof the principal axes of inertia. This deﬁnition of theorientation is not used in practice because its determination is not as precise as for the origin, and thesatellite orbits are not so sensitive with respect toits variations. Instead, these reference frame parameters are realized by external NNR conditions. Thisis done by successive transformations with respect
to the previous ITRF realization. Thus, its realization depends on the network geometries and the stations used for the deﬁnition, including the weighting.
The orientation rate of the ITRF2000 was aligned tothat of the geological model NNR-NUVEL-1A [Argus
et al. 1991; DeMets et al. 1990, 1994], which is also
the reference for the succeeding realizations, i.e., theITRF2005 and ITRF2008. As deformation zones are
neglected in the geological model and plate motions
are averaged over long time periods (up to 1 Myr),
there are diﬀerences with respect to present-day motions (see next paragraph).
Various studies have been performed on the NNR reference frame and its implication for the ITRF [Altamimi
et al. 2012; Argus et al. 2011; DeMets et al. 2010; Drewes
2009; Kreemer et al. 2006]. As an example, Figure 4.1
shows the discrepancies between the Actual Plate KInematic Model (APKIM) [Drewes 2009] and the geophysical NNR-NUVEL-1A model. The station velocities differ with a rate of 1.1 mm/yr around a rotation polewith a latitude of about −60◦ and a longitude of about120◦ [Drewes 2012] and the diﬀerences show a systematic pattern. However, their size is in the same order ofmagnitude as the discrepancies between diﬀerent models that are presently available [Altamimi et al. 2012].
Some notes on the deﬁnition of the kinematic frame:
The NNR frames mentioned above are a useful geodetic construct but not that useful for geophysical considerations because it is clear that the plates rotate
relative to the mantle and geophysical models (Earthrotation, Glacial Isostatic Adjustment (GIA), etc.) aremostly based on mean-mantle frames. Various studies
have been performed to deﬁne “absolute” plate motions

Inventory of Standards and Conventions: 4 Product-based review

1120





















































Fig. 4.1: Differences of horizontal station velocities between APKIM 2005 and NNR-NUVEL-1A model.

with respect to the Earth’s mantle by moving hot spots[e.g., Doubrovine et al. 2012; Torsvik et al. 2008, 2010].
The results published by Doubrovine et al. [2012] provide a net lithosphere rotation with respect to the mantle described by a rotation pole at latitude −41.36◦,
longitude 65.89◦ with a rate of 0.185◦/Myr, which isslightly higher than those of Torsvik et al. [2008, 2010](0.165◦ /Myr and 0.14◦ /Myr, respectively). The published velocity vectors will have rates at the level ofabout 15 to 20 mm/yr. For example, if the secular driftof the pole is to be interpreted, a mantle ﬁxed frame
is the appropriate one to compare to GIA models. The
observed drift of the pole is about 0.9◦ /Myr, and thus
the contribution from the diﬀerence between the NNR
and mantle ﬁxed frame is not negligible.
4.2.3.2 Modelling of station positions anddisplacements
The instantaneous position of a station X(t), which is
ﬁxed to the Earth’s crust, is deﬁned in Chapter 4 of the
IERS Conventions 2010 [Petit et al. 2010] as the sum ofa regularizedstation position XR (t) and conventionalcorrections n ∆Xn (t),X (t) = XR (t) +∆Xn (t) .
(4.1)
n

In the conventional secular approach, the regularized
station position itself is parameterized by a linear model
describing the position at any epoch ti by the positionat the reference epoch t0 plus a constant velocity multiplied by the time diﬀerence (ti − t0 )XR (ti ) = XR (t0 ) + Ẋ(t0 ) · (ti − t0 ).

(4.2)

Taking into account today’s high accuracy of the space
geodetic observations, non-linear station motions caused

by various geohysical phenomena (e.g., postseismic deformations, volcanic activities, atmospheric or hydrological loading eﬀects) become signiﬁcant [e.g., Bevis
et al. 2014; Blossfeld et al. 2014; X. Wu et al. 2015].
Below we discuss the consequences of the conventional
linear approach in the context with non-linear station
motions:– The displacements of reference markers on the crust
are modeled by conventional correction models (4.1),
considering the eﬀects on stations due to solid Earthtides, ocean loading, rotational deformation due topolar motion and ocean pole tide loading [Petit et al.
2010]. Even if these various eﬀects are conventionally modeled, one has to keep in mind that model
uncertainties, and possible model errors could aﬀect
the corrections of the instantaneous station position.
Geophysical eﬀects that are not considered in theconventional corrections will become visible as residuals in the position time series.
– For the non-conventional displacements due to e.g.
non-tidal atmospheric or hydrological environmental loads, the IERS Conventions 2010 do not recommend any correction model at the moment (e.g.
due to the fact that the current models are not accurate enough). Various investigations [e.g., van Dam
et al. 2012; Davis et al. 2012] have shown that periodic variations in the time series of station positions
with amplitudes up to several centimeters are causedby neglected corrections such as surface loading. As
an example Figure 4.2 shows the time series of theresidual non-linear station motions for GNSS station
Irkutsk (Russia) in comparison with the loading signal. In case of SLR solutions, atmospheric loading
can even cause a bias due to the so-called blue-sky
effect [Sośnica et al. 2013].

4.2 Terrestrial reference systems and frames

1121

30
20

GNSS estimates
Loading model

Up [mm]

10
0
−10
−20
−30
1996

1998

2000

2002

2004

2006

2008

2010

Fig. 4.2: Time series of GNSS height estimations for station Irkutsk, Russia. The atmospheric pressure loading timeseries provided by the Goddard VLBI group were used (see gemini. gsfc. nasa. gov/ aplo ; [Petrov et al. 2004]).

– Other issues are non-linear station motions causedby post-seismic behaviour after an earthquake [e.g.,
Freymueller 2010; Sánchez et al. 2013], which are currently modeled by piece-wise linear functions (segments) with positions and constant velocites. Besides
the mentioned geophysical phenomena, also anthropogenic eﬀects like, e.g. yearly groundwater withdrawal [Bawden et al. 2001] may aﬀect ITRF stations
in some regions.
Other possibilities are modeling discrepancies of thetechnique-dependent internal reference points, suchas GNSS phase center oﬀsets and variation models
for satellites and stations [Schmid et al. 2009] andcorrections for radio antenna thermal deformations[Nothnagel 2009].
– It should be noted that in the upcoming ITRF2014
realization non-tidal loading signals derived from geophysical models will be considered and an extended
parameterization has been implemented for the station motions.

Combined epoch solutions: As supplement to classical multi-year reference frames, the combination of
the space-geodetic data can be also performed epochwise (e.g., weekly). In these so-called Epoch Reference Frames (ERFs), the non-linear station motions
are directly estimated [Blossfeld et al. 2014]. These
combined epoch solutions are called ERF. The IAG/
IERS JWG 1.4 “Strategies for epoch reference frames”
investigates strategies for the computation of ERFs.

4.2.3.3 Input data for ITRF computations

Below some ongoing studies and research activities concerning the modeling of station motions and the handling of non-linear eﬀects are shortly summarized:

For a particular ITRS realization, the speciﬁcations forthe input data, i.e. solutions and/or normal equationsin SINEX format, are given in the call for participationof the IERS, which is released by the ITRS Center.
Such a call speciﬁes which parts of the IERS conventions should be obeyed, including updates. It is also
stated that, whenever departures from the recommendations of the IERS Conventions are preferred, it isrequested that the eﬀects of those deviations were documented.

Improved geophysical modeling: The Joint Working Group (JWG) 1.2 of the IAG and the IERS “Modeling environmental loading effects for reference frame
realizations” investigates approaches to model the remaining eﬀects (e.g., atmospheric and hydrologicalloading) and to validate the results.
New parameterization: Additionally to the current
linear model, parameters of trigonometric functionsor splines can be estimated to account for the observed seasonal station position variations. For a better description of post-seismic displacements a newparameterization is needed (e.g., logarithmic postseismic functions).

Each intra-technique solution is a combination of several Analysis Center (AC) solutions as shown in Table 4.1 (11 individual GNSS solutions and 7 individual
solutions for the three other space techniques). Moreover, diﬀerent software packages are in use by the ACs
for processing space geodetic observations. The current
status is that the standards and conventions used by allthese ACs are not always clearly (or fully) documented
and the corresponding AC log-ﬁles are not up to datein some cases. In order to achieve consistent results for
the ITRF it must be ensured that the data provided
by all contributing individual ACs are based on uniﬁed
standards and conventions.

1122

So far, only a selected subset of available data are usedby the services for generating the ITRF input data,e.g.,: In case of GNSS some ACs only use GPS andsome use GPS and GLONASS, but other GNSS are
not considered by the IGS so far. For SLR low sphericalsatellites and SLR data to GNSS satellites are not usedin International Laser Ranging Service (ILRS) computations.
4.2.4 Interaction with other products
The ITRF is a key geodetic product, that provides thebasis for precise positioning on the Earth’s surface andfor Earth orbiters as well as for many practical applications (e.g., navigation, surveying, mapping) and globalchange research in Earth sciences. How well the reference frame can be realized has important implications for Earth system studies and for the monitoringof global change phenomena. There is an interaction between the terrestrial reference frame and all the otherproducts addressed in this inventory, such as– Celestial reference frames– Earth orientation parameters– Satellite orbits– Gravity ﬁeld models– Heights
4.2.5 Open problems and recommendations
In this section we summarize the issues that were discussed in Section 4.2.3 and some recommendations areprovided. Open issues were identiﬁed in particular in
the following ﬁelds:
Reference frame definition
The origin of the ITRS is deﬁned in the CM of thewhole Earth system, including oceans and atmosphere,
whereas it is realized as a mean CM, averaged over thetime span of the SLR observations used and modeled asa secular (linear) function of time [Petit et al. 2010]. The
problem is that over shorter time scales (e.g., annual orinterannual), the realized origin moves with respect to
the CM by a few millimeters. According to the IERS
Conventions 2010 [Petit et al. 2010], the so-called “geocenter motion” should be substracted from the ITRF
origin (realized as mean CM) if an instantaneous geocentric position is required. However, as mentioned in
Section 4.2.3 the expression “geocenter motion” is deﬁned diﬀerently in the geodetic literature and a commonly accepted geocenter motion model does not exist
yet.

Inventory of Standards and Conventions: 4 Product-based review

Concerning the scale of the ITRS, it is deﬁned in TCG
time scale (consistent with IAU and IUGG (1991) resolutions), whereas its realization refers to TT. To avoid
inconsistencies, the relation between both time scales(see equation 3.1) must always be considered correctly
if observations and/or products refer to diﬀerent timesystems. Concerning the realization of the scale, theITRF2008 shows a signiﬁcant scale oﬀset between VLBI
and SLR [Altamimi et al. 2011], which is not visible in
the DTRF2008 solution of DGFI [M. Seitz et al. 2012].
This scale issue needs to be further studied by taking
into account the new ITRF2014 computations.
The orientation of the ITRS is realized by external NNR
conditions, whereas for each particular realization successive transformations with respect to the previous
ITRF realization are performed, and thus this procedure depends on the network geometries and the stations used for the transformations. The orientation rateis aligned to that of the geological model NNR-NUVEL1A. Although this method has several shortcomings (seeSection 4.2.3), it is used as it ensures continuity withprior ITRFs. The present results show that the uncertainties related to the reference frame deﬁnition are amajor error source for the ITRS realization, and further
improvements should be achieved to fulﬁl the GGOS requirements.
Integration of space techniques
A major limiting factor for the integration of the diﬀerent space geodetic techniques, the inter-technique combination, is the rather inhomogeneous distribution of
stations and the sparse distribution of high quality colocation sites with reliable local tie vectors. Current
ITRF results indicate that the discrepancies between
intra-technique solutions and the local tie vectors are
too large for many co-location sites. For about half ofthe co-locations, the diﬀerences are above 1 cm, whichindicates that the GGOS goals for the accuracy of theterrestrial reference frame are not fulﬁlled yet. Thus,
it is obvious that the long-term maintenance of colocation sites, their spatial distribution, and the qualityof the local tie measurements need to be improved. In
addition to the classical co-location on Earth, a challenge for the future would be the co-location of sensors
in space.
Handling of non-linear station motions
The diﬀerent approaches for the handling of non-linear
station motions (see Section 4.2.3) should be studied
in detail by making use of the upcoming ITRF2014
results and other suitable data. The IAG and IERS
JWG 1.2 “Modeling environmental loading effects for4.3 Earth Orientation Parameters (EOP)1123

reference frame realizations” is encouraged to investigate approaches to model these eﬀects and to validate the results. An extended parameterization to estimate the “residual” non-linear station motions has
been implemented for the ITRF2014 computations andthe respective results should be studied in detail. Also
the IAG/IERS JWG 1.4 “Strategies for epoch reference
frames” (ERF) is encouraged to investigate strategies
for the computation of ERFs. The ERFs should not
replace the classical secular frames, but may be considered as a useful supplement.

Recommendations how to deal with this topic for future ITRS realizations should be provided.
Recommendation 2.4 : To ensure consisent ITRF results the conventions and processing standards should
be consistently applied by the Services (IGS, ILRS,
IVS, IDS) and their ACs.

Input data for ITRF computations

4.3.1 Overview

In practice it is questionable, whether all partial solutions for the ITRF are based on exactly the same standards and conventions. To get an overview about thecurrent situation it is recommended that the Services(IGS, ILRS, IVS, IDS) together with all contributing
ACs compile documentation of the present status of thestandards and conventions currently applied in the software packages used for the data processing. Such a compilation of the processing standards has been performed
already by the IDS, which is given as an example. A table summarizing the standards that are used by the IDS
Analysis Centers with respect to their ITRF2014 submissions is available at ids-doris.org/combination/
contribution-itrf2014.html. The eﬀorts of the IGS
to tabulate models used by its Analysis Centers should
also be mentioned. For this purpose the corresponding
information is summarized on a Google docs spreadsheat and can be updated by the IGS Analysis Centersto reﬂect model updates. These eﬀorts should be continued (and strengthened) by the IAG Services to ensurethat the processing standards are consistently appliedby all Analysis Centers as a prerequisite for consistentproducts.
Summary of recommentations on ITRS/ITRF:
Recommendation 2.1 : The realization of the geodetic datum should be consistent with its deﬁnition.
The orgin of the ITRS should be unambigously deﬁned. It is highly recommended to perform further
studies related to the SLR and VLBI scale issue.

4.3 Earth Orientation Parameters(EOP)

Earth orientation and Earth rotation are two aspects ofthe same physical eﬀect. Earth rotation describes thechange of the orientation of the Earth’s body with respect to a space ﬁxed reference frame. Astronomy, satellite geodesy, or precise navigation require an accurate
knowledge of the orientation of the Earth in a quasi inertial reference frame. Various disciplines of geosciences
depend on the gravitational and geodynamic impactof rotation. Earth rotation is one of the impulses ofthe dynamics of the Earth system and the interactions
between individual components, such as the exchangeof angular momentum between atmosphere, ocean andsolid Earth, or the coupling mechanism between the
Earth’s core and mantle [Plag et al. 2009; F. Seitz et al.
2010]. Both requirements, orientation and rotation, will
be fulﬁlled if the Earth Orientation Parameters (EOP)
are given as functions of time, usually as a combinationof diurnal time series with analytic models.
Practically, the EOP are the parameters representing
the rotation part of the transformation between two
reference frames, a terrestrial and a celestial frame.
According to the deﬁnition by the IERS, these twoframes are actual realizations of the geocentric International Terrestrial Reference System (ITRS) and theGeocentric Celestial Reference System (GCRS) or the
Barycentric Celestial Reference System (BCRS):
ITRS

rotation−−−−−−−−−→

GCRS

translation−−−−−−−−−→BCRS.

Recommendation 2.2 : The station networks and thespatial distribution of high quality co-location sites
should be improved. This recommendation is fundamental to achieve the GGOS accuracy requirements
for the terrestrial reference frame and to ensure its
long-term stability.

The ITRS orientation is given by the IUGG Resolution
2 (2007). It is operationally maintained in continuity
with past international agreements (BIH orientation).
The initial orientation at 1984.0 is the orientation givenby the Bureau International de l’Heure (BIH) Terrestrial System (BTS84).

Recommendation 2.3 : The handling of non-linear
station motions should be further studied by also taking into account the new results of the ITRF2014.

The GCRS speciﬁcation (IAU Resolution A4, 1991, andupdate: IAU Resolution B1.3, 2000) follows a geocentric celestial relativistic metric. The orientation of theInventory of Standards and Conventions: 4 Product-based review

1124

GCRS is derived from the BCRS (IAU Resolution B2,
2006). The diﬀerent metrics of GCRS and BCRS imply a slight diﬀerence of the respective orientations,which are called geodesic precession and geodesic nutation [Fukushima 1991].
The BCRS is assumed to be oriented according to the
ICRS (IAU Resolution B2, 2006). The latter is recommended to show no global rotation with respect to a setof distant extragalactic objects. According to IAU Resolution B2 (1997) the initial orientation of the ICRS isgiven through the IERS celestial reference frame of theyear 1995 (IERS95) as described by the ICRS ProductCenter [Arias et al. 1995] within the IERS.
Since the EOP depend on the actual realizations of theconventional terrestrial and celestial reference frames,
the EOP system should be readjusted as soon as a newrelease of ITRF or ICRF is adopted.
The transformation of cartesian coordinates from ITRS
to GCRS at the date t is split into three segments
ITRS
polar
motion

GCRS
W (t)

Q(t)

TIRS

R(t)

CIRS

precessionnutation

Earth rotation
where Q(t), R(t), and W (t) are rotation matrices andR(t) ﬁts to the mean physical rotation of the Earth. The
meaning of “mean” still has to be speciﬁed. The choiceof the intermediate systems TIRS (Terrestrial Intermediate Reference System) and CIRS (Celestial Intermediate Reference System) is delaminated by the convention on R(t) being an elementary rotation around thez-axis. Hence TIRS and CIRS have a common z-axis,
called the celestial pole, which approximates a meanrotation axis of the Earth. Q(t) and W (t)−1 represent
the motion of that celestial pole in the GCRS and ITRS
respectively. If the celestial pole is choosen according to
the IAU 2000/2006 resolutions, it will be called Celestial Intermediate Pole (CIP).
According to IAU 2000 Resolution B1.7, the CIP separates the motion of the rotation axis of the ITRS in the
GCRS into a celestial and a terrestrial part. The convention is such that [Capitaine 2013; Petit et al. 2010]:– the celestial motion of the CIP includes the part ofprecession-nutation with periods greater than 2 daysin the GCRS and the retrograde diurnal part of polar
motion (including the Free Core Nutation (FCN)),– the terrestrial motion of the CIP includes the part ofpolar motion which is outside the retrograde diurnalband in the ITRS and the motion in the ITRS corresponding to nutations with periods smaller than 2
days.
As outlined in the IERS Conventions 2010 [Petit et al.
2010], the motion Q(t) of the CIP in the GCRS is realized by the IAU 2006/2000A precession-nutation model[Wallace et al. 2006] plus additional time-dependent
corrections derived by the IERS from space geodetic observations. The motion W (t)−1 of the CIP in the ITRS
is provided by the IERS through time series derived
from space geodetic observations and models including
variations with frequencies outside the retrograde diurnal band. The implementation of the IAU 2000 and
IAU 2006 resolutions for the transformation is detailed
in the IERS Conventions 2010 [Petit et al. 2010].
In 2013, IAG and IAU set up a new Joint Working
Group “Theory of Earth Rotation” [Ferrándiz et al.
2015]. The purpose of this JWG is promoting the development of theories of Earth rotation that are fully
consistent and that agree with observations and provide
predictions of the EOP with the accuracy required tomeet future needs as recommended by, e.g., GGOS.
Concerning the realization of EOP products, the EOP
are represented by the ﬁve following quantities (as speciﬁed the latest IAU 2000/2006 version of the terrestrialcelestial transformation):– δX = X − Xmodel, δY = Y − Ymodel : corrections
to the x- and y-coordinates of the CIP unit vector
in the celestial system GCRS using the model IAU
2000/2006,– ∆UT1 = UT1 − UTC : diﬀerence of mean solar time
(Universal Time UT1) and Coordinated Universal
Time (UTC) vice the averaged atomic time,– xp , yp : Cardan angles of the polar wobble W (t) =R3 (−s′ )R2 (xp )R1 (yp ), traditionally called “pole coordinates”. The x- and y-coordinates of the CIP unit
vector in the terrestrial system ITRS are sin(xp ) andcos(xp ) sin(−yp ).
The IERS is responsible for providing the time seriesof xp , yp , ∆UT1, δX, δY on an operational basis derived from the various space geodetic techniques (VLBI,SLR/LLR, GNSS and DORIS). The EOP products areavailable from the database of the IERS (see www.iers.
org). Two Product Centers are responsible for the EOP
generation, namely the IERS Earth Orientation Center and the IERS Rapid Service/Prediction Center [seeGambis et al. 2014; IERS 2014; Luzum et al. 2014].

4.3 Earth Orientation Parameters (EOP)

4.3.2 IERS Earth Orientation Center
The IERS Earth Orientation Center is responsible formonitoring of long-term EOP, publications for time dissemination and leap second announcements. It is located at the Observatoire de Paris in France (see hpiers.
obspm.fr/eop-pc). The general procedure for the generation of the EOP series is described in various publications [e.g., Bizouard et al. 2009b; Gambis 2004; Gambis et al. 2003, 2011].
The Earth Orientation Center provides the following
main products:
Bulletin B contains ﬁnal daily Earth orientation datafor one month (see ftp://hpiers.obspm.fr/iers/
bul/bulb_new/bulletinb.pdf)
Bulletin C contains announcements of leap seconds
in UTC (see ftp://hpiers.obspm.fr/iers/bul/bulc/BULLETINC.GUIDE)
Bulletin D contains an announcement of the value∆UT1 = UT1 − UTC (see ftp://hpiers.obspm.
fr/iers/bul/buld/BULLETIND.GUIDE)
EOP 08 C04 contains long term Earth orientation data
(see ftp://hpiers.obspm.fr/iers/eop/eopc04/
C04.guide.pdf)
In the next section the EOP 08 C04 long term series isaddressed in more detail.
4.3.2.1 Realisation of EOP time series
The Earth Orientation Center of the IERS, located at
Paris Observatory, SYRTE, has the task to provide theinternational reference time series for the EOPs, referred as “IERS C04” (Combined C04), resulting froma combination of EOP series derived from individual
space geodetic techniques. The latest C04 solution, referred as EOP 08 C04, became the oﬃcial C04 solution since February 2010. The EOP 08 C04 time series
is available from 1962 to the present and it contains
smoothed values of xp , yp , UT1-UTC, LOD, δX, δY
at 1-day intervals w.r.t. IAU 2006/2000A precessionnutation model and consistent with ITRF2008. EOP 08
C04 is updated twice a week with a latency of 30 days
and the data are stored in yearly ﬁles since 1962 and in
one ﬁle 1962–now. A documentation for this EOP series
is given by [Bizouard et al. 2009b] and in the Annual
Reports of the IERS (see [IERS 2014]).
In the past, EOP combined series were based on individual solutions derived by the analysis centers for thediﬀerent space techniques, i.e., VLBI, SLR/LLR and
GNSS. Nowadays, Technique Centers, i.e. IVS, ILRS,

1125

IGS and IDS are providing combined solutions based on
individual analysis center contributions. The solutions
used for the computation of the EOP 08 C04 series areshown in Table 4.3. More information on these input
solutions along with their accuracies is provided in the
IERS Annual Reports (see [Gambis et al. 2014]).
Table 4.3: EOP series used in the computation of the EOP 08
C04 series (see [Gambis et al. 2014] for more details).
EOP component

EOP series used in the combination

Pole coordinatesand LODIGS Final Combined
IGS Rapid Combined
IVS Combined
ILRS Combined∆UT1

IVS Combined
Intensive VLBI solutions

Celestial pole
offsets

IVS Combined

As described by Bizouard et al. [2009b] the computationof the EOP 08 C04 series is based on several processing
steps.
– Each given EOP series (see Table 4.3) is transformed
to the choosen ITRF/ICRF pair by removing an estimated linear drift.
– UT1−UTC is regularized (by removing zonal tides)
and replaced by UT1−TAI to remove leap second
jumps, whereas TAI denotes International Atomic
Time.
– For each given series an intermediate reference solution is computed from the former combined solution
by four-point window Lagrange interpolation andextrapolation; the reference series, which should contain the main part of the signal, is then subtracted
from the input series; the diﬀerence is used in the
combination.
– The trends of LOD in GNSS and SLR series, which
are usually induced by non-modeled orbit errors andhigh correlations between LOD and orbit parameters, are determined by Vondrak ﬁltering [Vondrak
1977] of (LODGNSS/SLR − LODVLBI ) and removed.
– The resulting series are combined with the “combined smoothing method” [e.g., Vondrak et al. 2000]
including weighting, outliers search and high frequency ﬁltering.
– The ﬁnal values are obtained by interpolating the ﬁltered series at 1 day intervals, adding back the intermediate reference series, reconstructing UT1−UTCand adding back the zonal tides.
By applying the above described procedure, the EOP
series is determined separately from the terrestrial and1126

celestial reference frame. In the past, this has caused
discrepancies at the level of 300 µas between the IERS
C04 series and current ITRF realizations [see Bizouard
et al. 2009b]. In the latest ITRF realizations, the ITRF
2005 [Altamimi et al. 2007], ITRF2008 [Altamimi et al.
2011; M. Seitz et al. 2012] and the upcoming ITRF2014
realization, the time series of station positions havebeen estimated simultaneously with the EOP. It is essential for many applications to ensure the consistency
between the C04 series and the ITRF with a good accuracy. For that purpose, the EOP Product Center has
developed together with the ITRS Product Center astrategy for the alignment of the EOP results to thelatest ITRF realization. As described in [Bizouard etal. 2009a] this is done in two ways: using (1) the upgraded procedure of the EOP Product Center and (2)CATREF combination of IGN, France, incorporating
the routinely available SINEX ﬁles by the techniqueservices. The procedure of the EOP Product Centerat Paris Observatory is routinely performed where the
CATREF combination is to be done at regular intervals(e.g., every 6 months).
The following accuracy for the C04 series has been reported by Bizouard et al. [2009b]: The EOP 08 C04
series has been compared with the preceding version
EOP 05 C04. The diﬀerences between both series are
21 ± 30 µas and −58 ± 34 µas for the xp and yp , respectively. For UT1, LOD and the celestial pole oﬀsets thediﬀerences are very small and much below their standard deviations. For the latest EOP 08 C04 series theauthors give an accuracy of about 30 µas for the pole
coordinates and about 15 µs for LOD, which is as goodas the oﬃcial IGS combined series.
Besides the EOP 08 C04 series, other combined Earthorientation series (e.g., SPACE2008, COMB2008, POLE
2008) have been computed [Ratcliﬀ et al. 2010]. These
series are available from JPL’s Geodynamics and Space
Geodesy Group via anonymous ftp: ftp://euler.jpl.
nasa.gov/keof/combinations/2008.

4.3.3 IERS Rapid Service/Prediction Center
The IERS Rapid Service/Prediction Center is responsible for providing predicted EOP and measured EOP on
a rapid turnaround basis, primarily for real-time users
and others needing EOP information sooner than thatavailable in the ﬁnal series published by the IERS Earth
Orientation Center. It is located at the United States
Naval Observatory (USNO) in Washington, D.C., USA(see www.usno.navy.mil/USNO/earth-orientation).
The general procedure for the generation of the real-

Inventory of Standards and Conventions: 4 Product-based review

time EOP and predictions is described in various publications [e.g., Luzum et al. 2014; McCarthy et al. 1991;
Stamatakos et al. 2007].
The IERS Rapid Service/Prediction Center provides
the following main products:
Bulletin A contains xp , yp and UT1-UTC including
their errors at daily intervals and predictions for one
year into the future (see ftp://maia.usno.navy.
mil/ser7/readme.bulla).
Standard Rapid EOP Data contain quick-look weekly estimates of the EOP since 1973-01-02 (ﬁle finals.all) or since 1992-01-01 (ﬁle finals.data) and predictions for the next 365 days (see ftp://maia.
usno.navy.mil/ser7/readme.finals).
Daily Rapid EOP Data contain quick-look daily estimates of the EOP (ﬁle finals.daily) for the last
90 days and predictions for the next 90 days (seeftp://maia.usno.navy.mil/ser7/readme.finals).
GPS Daily Rapid EOP Data contain quick-lookdaily estimates of the EOP (ﬁle gpsrapid.daily) forthe last 90 days and predictions for the next 15 days
(see ftp://maia.usno.navy.mil/ser7/readme.gps
rapid).
4.3.3.1 Realisation of real-time EOP and predictions
The algorithm used by the IERS Rapid Service/Prediction Center for the determination of the quick-look
Earth Orientation Parameters is based on a smoothing(weighting) cubic spline interpolation with adjustablesmoothing ﬁt to contributed observational data [Luzumet al. 2014; McCarthy et al. 1991]. Biases and rates withrespect to the EOP 08 C04 series are determined using
a robust linear estimator. The data contributing to thedetermination of the quick-lock Earth orientation parameter are displayed in Table 4.4. More informationon these input solutions along with their accuracies isgiven in [Luzum et al. 2014]. The authors also provide
the accuracy of the EOP predictions. As an example,
the diﬀerences between the EOP predictions producedby the daily solutions and the EOP 08 C04 series areshown in Table 4.5.

4.3.4 Discussion of the present status
4.3.4.1 Input data
As shown in Tables 4.3 and 4.4, individual and intratechnique combined solutions are used as input data
for the computation of the EOP series and predictions.

4.3 Earth Orientation Parameters (EOP)1127

Table 4.4: EOP series used in the determination of the quicklock Earth orientation parameter. The IGS and USNO GPS results provide LOD, the derivative of UT1. (see [Luzum et al.
2014] for more details).
EOP component

EOP series used in the combination

Pole coordinates

IGS Final Combined
IGS Rapid Combined
IGS Ultra Combined
IVS Combined
ILRS Combined
Individual SLR and VLBI series∆UT1

IVS Combined
Individual VLBI solutions
IGS Ultra Combined
USNO GPS UTCelestial pole
offsets

IVS Combined
Individual VLBI solutions

Table 4.5: Root mean square of the differences between the EOPtime series predictions produced by the daily solutions and the
08 C04 combination solutions for 2013 (the values are extracted
from Table 3a of [Luzum et al. 2014]). Note that the prediction
length starts counting from the day after the date of the solution
epoch.

formation on the general procedure, but an overall documentation of the mathematical foundations is missing. Thus, it is diﬃcult to evaluate the present combination procedure and to assess their impact on the
EOP results. The same holds for the description of the
combination procedure for the generation of real-time
EOP and predictions, where some general information
is available (see the references given in Section 4.3.3),
but a detailed documentation of the mathematical foundations is missing.
4.3.4.3 Consistency between EOP and ITRF
Consistency between ITRF and EOP has been achieved
for the two latest ITRS realizations, the ITRF2005 and
ITRF2008, by simultaneously estimating the relevant
parameters in a common adjustment. However, the procedure of the alignment between the combined EOP XX
C04 series and the ITRF results is not described inmuch detail [see Bizouard et al. 2009a].

4.3.5 Interaction with other products
Days infuture

xp
µas

xp
µas

UT1-UTC
µs

1
5
10
20
40
90

0.327
1.81
3.46
6.75
12.9
23.8

0.228
1.22
1.94
2.66
4.12
16.5

0.058
0.214
0.525
1.88
2.82
8.49

The intra-technique combinations have been performedby the Technique Centers (i.e., IGS, ILRS, IVS) fromseveral individual analysis center (AC) solutions by using various software packages. Although the standards
and conventions used by all these ACs should follow
the IERS Conventions as close as possible, the current
status is that they are not always clearly (or fully) documented and in some cases the corresponding AC logﬁles are not up to date. Thus, it is diﬃcult to exactly
know the underlying standards and models for the processing of the input data. In order to achieve consistent
EOP results it must be ensured that the data provided
by all contributing ACs are based on identical standards
and conventions.
4.3.4.2 Combination procedure
As described in Section 4.3.2, the combination procedure for the determination of the EOP 08 C04 seriesconsists of several processing steps. The relevant publications [see Bizouard et al. 2009a,b] give some more in-

The space geodetic observations provide a direct link of
the EOP with
– Celestial reference frames– Terrestrial reference frames– Low degree gravity ﬁeld coeﬃcients (i.e., C21 /S21 )– Satellite orbits
In addition there is a link to those parameters, that arederived from the above mentioned products.

4.3.6 Open problems and recommendations
4.3.6.1 Input data
In practice it is not clear, if all solutions contributing to
the EOP combinations are based on exactly the same
standards and conventions. To get an overview about
the current situation it is recommended that the Services (IGS, ILRS, IVS, IDS) together with all contributing ACs compile documentation of the present status of
the standards and conventions currently applied in thesoftware packages used for the data processing. Basedon the outcome of such an inventory, the Services should
initiate steps to ensure that the processing standards
are consistently applied by all ACs as a prerequisite forconsistent EOP results. See also the recommendations
for the input data used for the ITRF computations.

1128

4.3.6.2 Combination procedure and consistency
The combination procedures, which are currently applied for both the determination of the long-term EOP
series and for near-real time and predicted EOP should
be described in more detail, including the mathematical foundations. This holds also for the alignment of
the EOP series with the ITRF realizations. This would
be the basis to evaluate the present methodology andto address important questions, e.g.,: (1) How are the
EOP series aligned with the ITRF and ICRF? (2) How
are the EOP determined beyond the epochs of the observations used for the ITRF2008? (3) How is the regular updating of the series performed? (4) What are
the major limitations for the accuracy of the near-realtime and predicted EOP? As discussed during the IERS
Retreat in Paris in June 2013 (www.iers.org/IERS/
EN/Organization/Workshops/Retreat2013.html), it
should be investigated how the EOP predictions could
be improved by reducing the latency of the last data
point and by improved AAM and OAM update schedules, i.e., updates with 6 hour versus 24 hour latency.
An important issue is also the consistency between TRF,
CRF and EOP (see IUGG Resolution No. 2, 2011) as
already discussed in Sections 4.1 and 4.2.
Summary of recommendations on EOP:
Recommendation 3.1 : The Services should document the present status of the standards and conventions implemented in their software packages used for
determining EOP results.
Recommendation 3.2 : The procedures used for generating the EOP series and the near-real time andpredicted EOP should be described in more detail,including mathematical foundations.
Recommendation 3.3 : Concerning the EOP predictions, it is recommended to investigate how the results can be improved by reducing the latency of thelast data point and by more frequently updating the
AAM and OAM data.
Recommendation 3.4 : Methodologies and proceduresfor the generation of consistent TRF, CRF and EOP
should be investigated.

Inventory of Standards and Conventions: 4 Product-based review

clocks provide the basis for mm-level positioning for realizing global and regional reference systems, geophysical studies, surveying, deformation monitoring, and cadastre.
The Analysis Centers of the IGS process observationsof global GNSS tracking networks on a regular basis inorder to provide a variety of products. One of the IGS
core products are the ﬁnal orbits. These orbits are generated by the IGS Analysis Center Coordinator (ACC)
as a weighted mean of the individual AC orbits [Beutler
et al. 1995; Griﬃths et al. 2009], see Figure 4.3. They
are provided with a latency of 12 – 18 days.
Due to advances in observation modeling and processing strategies since the establishment of the IGS in
1994, the orbit quality has steadily improved. In orderto achieve the highest product quality also for the orbits of the early years and to achieve consistency withcurrent operational orbits, the IGS conducted a ﬁrst
reprocessing campaign covering the time period 1996 –2008. These data were also used for the computation of
ITRF2008. A second reprocessing covering 1994 – 2014provides the input for ITRF2014. Users are advised touse the latest generation of reprocessed products toachieve the highest level of accuracy as well as consistency with the operational products for time periods
where the reprocessed products are not available.
The individual analysis centers contributing to the ﬁnal
orbit combination are:
COD Center for Orbit Determination in Europe, Switzerland
EMR Natural Resources Canada, Canada
ESA European Space Agency, Germany
GFZ Deutsches GeoForschungsZentrum, Germany
GRG GRGS-CNES/CLS, France
JPL Jet Propulsion Laboratory, USA
MIT Massachusetts Institute of Technology, USA
NGS National Geodetic Survey, USA
SIO Scripps Institution of Oceanography, USA

4.4 GNSS satellite orbits
Global Navigation Satellite Systems (GNSS) like the
US American GPS and the Russian GLONASS are themost popular space geodetic techniques with a wide
range of applications. Precise GNSS satellite orbits andFig. 4.3: Generation of the IGS final orbit and clock products.

4.4 GNSS satellite orbits1129

4.4.1 Summary of standards

4.4.2.4 Attitude

The standards listed in Table 4.6 are based on the recommendations for the 2nd IGS reprocessing campaign,see acc.igs.org/reprocess2.html. Due to mostly outdated analysis log ﬁles, the compliance of the ACs withthese standards could not be veriﬁed.

The basic attitude condition of a GNSS satellite is thatthe navigation antenna points to the center of the Earthand the solar panels are oriented perpendicular to theSun. To fulﬁl these conditions, the satellite has to rotate
around its z-axis. The speed of this rotation depends
on the elevation of the Sun above the orbital plane.
Due to technical restrictions, the implementation of theattitude control deviates from this ideal case. Several
models for the attitude of GNSS satellites are available
but these models are not widely used at the moment.

4.4.2 Discussion and deficiencies
4.4.2.1 Solar radiation pressure modeling
Modeling of the Solar Radiation Pressure (SRP) is probably the largest error source of today’s GNSS orbits.
Deﬁciencies in the SRP modeling are visible as harmonics of the draconitic year in orbital [Griﬃths et al.
2013] and other parameters: station positions [AmiriSimkooei 2013; J. Ray et al. 2008], geocenter [Hugentobler et al. 2005], and Earth Rotation Parameters (ERP)[Steigenberger 2009]. A comparison of diﬀerent SRP
models can be found in Sibthorpe et al. 2011.
Recent developments that at least partly reduce thesesystematic errors include an adjustable box-wing model[Rodriguez-Solano et al. 2014], the extended Empirical
CODE Orbit Model [Arnold et al. 2015], a cuboid box
model for the Galileo IOV satellites [Montenbruck et al.
2015], and a box-plate model for GIOVE-B [Steigenberger et al. 2015].

4.4.2.2 Albedo
Earth radiation pressure or albedo in particular aﬀects
the scale of the orbits. Although several authors [e.g.,
Rodriguez-Solano et al. 2011; Ziebart et al. 2007] haveshown the beneﬁts of including albedo, this eﬀect is not
yet considered by all ACs.

– GPS block II, IIA, IIR satellites [Kouba 2009a]– GPS block IIA satellites [Rodriguez-Solano et al. 2013]– GPS block IIF satellites [Dilssner 2010]– GLONASS-M satellites [Dilssner et al. 2010]

4.4.2.5 Satellite antenna model
GNSS measurements refer to the electrical phase centerof the transmission and receiving antennas. The mean
diﬀerences between the mechanically well-deﬁned antenna reference point of the receiver antennas and thecenter of mass for the satellite antennas are called Phase
Center Oﬀsets (PCOs). Variations of the actual phasecenter depending on azimuth and elevation of the transmitted/received signal are called Phase Center Variations (PCVs). As usually no ground calibrations areavailable for the transmitting antennas, satellite antenna phase center oﬀsets and variations were estimatedfrom global GNSS data to derive antenna models for
GPS and GLONASS.

4.4.2.3 Antenna thrust

The current model igs08.atx [Rebischung et al. 2012]
considers only block-speciﬁc PCVs and satellite-speciﬁc
PCOs. Satellite antenna phase center variations for nadir
angles larger than 14◦ (important for Low Earth Orbiter (LEO) processing) were recently determined by
the Center for Orbit Determination in Europe (CODE)[Jäggi et al. 2012] and added to igs08.atx [Schmid etal. 2013].

When transmitting navigation signals, GNSS satellites
experience an acceleration in radial direction depending on the power of the emitted signals called antenna
thrust. Rodriguez-Solano et al. [2012] report a 5 mmradial orbit change when considering antenna thrust in
GPS orbit determination. Transmit power levels for the
GPS satellites are available at acc.igs.org/orbits/
thrust-power.txt but no information is available for
GLONASS and the emerging GNSS.

In the current model, azimuthal variations of the GNSS
satellite antennas [Schmid et al. 2005] are not yet considered. One could also think of estimating satellitespeciﬁc antenna PCVs to account for deviations of theindividual transmitting antennas from the block-speciﬁcmean values. In view of the emerging GNSS it is a critical issue that the satellite antenna oﬀsets and phasecenter variations of Galileo satellites are unknown. For
BeiDou and QZSS only the antenna oﬀsets are known.

Inventory of Standards and Conventions: 4 Product-based review

1130

Table 4.6: Selected standards of the IGS for its second reprocessing campaign.
General Standards
Reference Frame
Antenna Model
P1C1 Code Biases
Phase Wind-Up
Gravity Field
Non-Tidal Loading
Higher-order Ionosphere
A Priori Troposphere Delay

Troposphere Mapping

IERS 2010 Conventions [Petit et al. 2010]
IGS08 [Rebischung et al. 2012]
igs08.atx [Rebischung et al. 2012]
ftp://ftp.unibe.ch/aiub/bcwg/cc2noncc
according to J. Wu et al. [1993]
EGM2008 [N. Pavlis et al. 2012]
not applied
2nd and 3rd order applied[Fritsche et al. 2005; Hernández-Pajares et al. 2011]
Local meteorological measurements or Global Pressure and Temperature (GPT) model [Böhm et al. 2007] to compute hydrostaticdelays according to [Davis et al. 1985]
Global Mapping Function (GMF) [Böhm, Niell, et al. 2006] orVienna Mapping Function 1 (VMF1) [Böhm, Werl, et al. 2006]

4.4.2.6 Non-tidal loading

4.4.4 Open problems and recommendations

It is currently not recommended to apply non-tidal loading corrections at the observations level. However, aliasing eﬀects can be introduced by this procedure [Dachet al. 2011]. In addition, one should be aware that atmospheric loading is partly compensated when using
GMF/GPT [Kouba 2009b; Steigenberger et al. 2009].

The BPS has identiﬁed open problems in the ﬁeld of
GNSS orbit modeling and recommendations for further
studies. These include:

4.4.2.7 Subdaily ERP modelGriﬃths et al. [2013] found subdaily alias errors in IGS
orbit, coordinate, geocenter, and ERP products. They
attribute these errors to deﬁciencies of the IERS subdaily ERP model and conclude that an improved modelis needed to mitigate these errors.
4.4.3 Links to other products
Changes in the orbit modeling directly aﬀect the following geodetic products:– Terrestrial Reference Frame (TRF)– TRF densiﬁcation, e.g., IAG Reference Frame Sub–
Commission for Europe (EUREF)– GNSS satellite orbits and clocks– Earth Orientation Parameters (EOP)– Time-dependent Total Electron Content (TEC) maps
– Troposphere Zenith Total Delay (ZTD) time series
Changes in the orbit modeling aﬀect the following products utilizing GNSS satellite orbits:– LEO satellite orbits– Static gravity ﬁeld
– Time-dependent gravity ﬁeld
– Time series of sea surface heights– Time series of ice sheet and glacier elevations– The consistency of the orbit solutions submitted by
the IGS Analysis Centers has to be assured.
– An improved model for subdaily variations in Earth’s
rotation is required.
– Radiation pressure modeling and aliasing of orbital
errors into geodetic parameters needs to be further
studied.
– The impact of diﬀerent arc lengths (1-day vs. 3-day)on geodetic parameters needs to be assessed.
– Satellite antenna oﬀsets are required for Galileo,
IRNSS, and SBAS satellites.
– Satellite antenna phase center variations are requiredfor BeiDou, Galileo, IRNSS, QZSS, and SBAS.
– Attitude models are required for BeiDou, Galileo,
IRNSS, and SBAS satellites.
– Transmit power level is required for BeiDou, Galileo,
GLONASS, IRNSS, QZSS, and SBAS satellites.
Summary of recommendations on GNSS orbits:
Recommendation 4.1 : The impact of analysis strategies such as radiation pressure modeling and orbit arc
length on derived geodetic parameters should be investigated in detail.
Recommendation 4.2 : An improved model for subdaily variations in Earth’s rotation should be developed.
Recommendation 4.3 : Satellite operators should beurged to provide detailed information about satellite dimensions, surface properties, attitude models,antenna oﬀsets, antenna phase patterns, and radio
emission power.

4.5 Gravity and geoid

4.5 Gravity and geoid
Gravity and geoid related products are collected by several IAG Services, which all together compose the International Gravity Field Service (IGFS). The overall goalof the IGFS is to coordinate the servicing of the geodetic
and geophysical community with gravity ﬁeld-relateddata, software and information. The combined data of
the IGFS entities should include satellite-derived global
models, terrestrial, airborne, satellite and marine gravity observations, Earth tide data, GNSS leveling data,
digital models of terrain and bathymetry, as well as
ocean gravity ﬁeld and geoid from satellite altimetry.
Both the static components and the temporal variations of the gravity ﬁeld will be covered by the IGFS.
The organizational structure of the IGFS is shown in
Figure 4.4.
The IGFS is not handling gravity ﬁeld data distribution directly – IGFS functions as a unifying service forthe following gravity-ﬁeld related IAG Services – “IGFS
Centers”:
ICGEM International Center for Global Gravity Field
Models – distribution of satellite and surface
spherical harmonic models;
BGI
Bureau Gravimétrique International – collection, archiving and distribution of gravity
data;
ISG
International Service for the Geoid – collection and distribution of geoid models, collection and distribution of software for geoid
computation, and organization of technicalschools on geoid determinations;
ICETInternational Center for Earth Tides – collection and archiving of global Earth tide data;
IDEMS International Digital Elevation Model Service– Global Digital Terrain Models.
The general character of the products oﬀered by the
IGFS Services is slightly diﬀerent from products of other
IAG Services. While, for example, the ITRF is generated by a combination of products or observations
provided by various other IAG Services, IGFS products are singular products either representing observations or geophysical models. Geophysical models usually are based on various data or observations, which
are taken from a number of sources (e.g. satellite mission data, terrestrial observations). This implies that
products from the IGFS as a minimum should indicate the standards applied for their generation. In manycases this can be guaranteed, but there are also otherproducts for which this hardly is possible. Often huge
software packages are used for product generation, in

1131

which speciﬁc standards and conventions have been implemented. These standards and conventions often are
unknown or not speciﬁed together with the product.
In the following sections the products oﬀered by the
IGFS Services are brieﬂy described and references forthese products are provided. In the subsequent tables
for each identiﬁed product an inventory of the standards applied for the generation of these products isgiven (on a best knowledge basis). This information is
extracted from the available information provided on
the services web sites or the related documentation.

4.5.1 ICGEM – International Center for Global
Earth Models
The International Center for Global Earth Models collects and distributes historical and actual global gravity
ﬁeld models of the Earth and oﬀers calculation service
for derived quantities. In particular the tasks include:
Collecting and archiving of all existing global gravity
ﬁeld models, maintaining an online archive for getting
access to global gravity ﬁeld models, providing web
based visualization of the gravity ﬁeld models, theirdiﬀerences and their time variation, oﬀering a service
for calculating diﬀerent functionals of the gravity ﬁeld
models, and providing tutorials on spherical harmonics
and the theory used by the calculation service.
The products of ICGEM are:
– Global gravity ﬁeld model spherical harmonic series
in ICGEM format (static and time series);– Global topography model spherical harmonic series
in ICGEM format (topography heights and gravitational potential);– Gravity functionals and topography on freely selectable grids by calculation service: height anomaly,
geoid height, gravity disturbance, gravity anomaly,
Bouguer anomaly, gravity, gravitation, radial gravity
gradient, equivalent water height.
More details about tasks and products can be foundat the service web site icgem.gfz-potsdam.de/ICGEM/ICGEM.html and within the following references:– Description of the ICGEM format:
icgem.gfz-potsdam.de/ICGEM/documents/ICGEMFormat-2011.pdf;– [Barthelmes 2013], icgem.gfz-potsdam.de/ICGEM/
theory/str-0902-revised.pdf.

Inventory of Standards and Conventions: 4 Product-based review

1132

Fig. 4.4: Organizational structure of the IGFS

4.5.2 BGI – Bureau GravimétriqueInternational
The overall task of the Bureau Gravimetric International (BGI) is to collect, on a world-wide basis, all measurements and pertinent information about the Earthgravity ﬁeld, to compile them and store them in a computerized data base in order to redistribute them onrequest to a large variety of users for scientiﬁc purposes.
The products of the BGI are:
– Collection of land, marine gravity data and reference
gravity stations;– Data from absolute gravity stations (see mirror site:
agrav.bkg.bund.de);– High resolution grids and maps of the Earth’s gravity anomalies (Bouguer, isostatic and surface freeair), computed at global scale in spherical geometry(World Gravity Map (WGM) 2012);– Regional gravity anomaly grids (derived from EGM
2008);– Gridded estimates of (i) gravity accelerations, (ii)gravity disturbances, (iii) quasi-geoid undulations,and (iv) deﬂection of the vertical components fromthe ultra high resolution global gravity ﬁeld model
GGMplus [Hirt et al. 2013];– Predicted gravity values – normal gravity is computed using Somigliana formula in the GRS80 system.
More details about tasks and products can be found at
the service web site bgi.omp.obs-mip.fr/ and in thefollowing references:– Land gravity data format (EOL) / Sea gravity data
format (EOS):
bgi.omp.obs-mip.fr/content/download/720/
4949/file/BGI_EOL_EOS_Data_format.pdf;– Fortran routine to extract [Longitude / Latitude /Bouguer] ﬁelds from EOL data ﬁle:bgi.omp.obs-mip.fr/content/download/721/
4952/file/conveol2xyz.pdf;– Determination of normal gravity (BGI document):
bgi.omp.obs-mip.fr/content/download/723/
4969/file/BGI_Formules_Pesanteur_Normale.
pdf;– Déﬁnition des anomalies gravimétriques (in French):
bgi.omp.obs-mip.fr/content/download/724/
4972/file/FORMUL00.pdf;– Gravity deﬁnitions & anomaly computations(National Geospatial-Intelligence Center (NGA)
document):
bgi.omp.obs-mip.fr/content/download/725/
4975/file/computations.pdf.

4.5.3 ISG – International Service for the Geoid
The activities of the International Service for the Geoid(ISG) are on educational, research, and data collection: Main tasks of the ISG are to collect geoid dataon a worldwide scale (geoid repository), to collect anddistribute software for geoid determination (software
download), to conduct research on procedure for geoid
determination (projects), to organize geoid schools, andto edit and distribute the Newton’s Bulletin.
The products of the ISG are:

4.5 Gravity and geoid– Regional geoid models;– Geoid software (local geoid estimation; harmonic manipulator; ellipsoidal gravity model manipulator; computation of terrain eﬀects on gravimetric quantities);– International schools on geoid determination and thematic schools.

1133– Ocean tides loading computation: There are available
computations for a number of tide models and for aset of stations. There is missing a detailed descriptionof these ﬁles in order to identify the standards andconventions applied for these products.

More details about tasks and products can be found at
the service web site: www.isgeoid.polimi.it/index.
html. No product related references are available at the
ISG web site. For regional geoid models the related reference in many cases is indicated.

More details about tasks and products can be found at
the service web site: www.upf.pf/ICET/. No productrelated descriptions are available at the ICET web site,
but an extensive bibliography related to Earth tides
is available. In general it seems that the web sites are
outdated.

4.5.4 ICET – International Center for Earth
Tides

4.5.5 IDEMS – International Digital Elevation
Model Service

The terms of reference of the International Center for
Earth Tides (ICET) can be summarized as follows:– Collection of all available measurements related to
Earth tides;– Evaluation of these data by convenient methods ofanalysis in order to reduce the very large amountof measurements to a limited number of parameterswhich should contain all the desired and needed geophysical information;– Comparison of the data from diﬀerent instruments
and diﬀerent stations distributed all over the world,
evaluating their precision and accuracy from the pointof view of internal errors as well as external errors;– Help solving the basic problem of calibration by organizing reference stations or realizing calibration devices;– Filling gaps in information and data;– Building a data bank allowing immediate and easycomparison of earth tides parameters with diﬀerent
Earth models and other geodetic and geophysical parameters;– Ensuring a broad diﬀusion of the results and information to all interested laboratories and individual
scientists.
The products of the ICET are:– Tidal analysis results for gravimetric stations: For alarge number of stations tidal loading computations
can be downloaded. A detailed description of theseﬁles in order to identify the standards and conventions applied for these products is missing. Results
for tilt stations, strain stations, barometric stations
and wells are not available from the web site (linkerror);

This service currently is not active and will be reconﬁgured. The following paragraphs reﬂect the status until
2014 and shall provide some ﬂavour about the tasks ofthis service. The International Digital Elevation Model
Service (IDEMS) web site provides a focus for distribution of data and information about Digital Elevation
Models (DEMs), relevant software and related datasets(including representation of inland water within DEMs)
which are available in the public domain. Currently, thissite has links to a number of Global Digital Elevation
Models (GDEM) and hosts the ACE GDEM. Information on analysis of the SRTM dataset will be added as
it becomes available.
The service does not provide products via its web site.
It provides links to other project or satellite mission web
sites where digital elevation models are made available.
Some of the links are not active (web site outdated).
As this service does not provide digital products noinventory of standards and conventions can be generated. The following digital elevation data bases are addressed via the web site: SRTM, ACE, ACE2, ASTER,GLOBE, GTOPO30, NED.
Some information on tasks and products can be foundat the service site www.cse.dmu.ac.uk/EAPRS/iag/.
The web site provides a bibliography for relevant publications, which should be helpful for those who wantto make use of global digital elevation models.

4.5.6 IGFS Products Inventory of Standards
From the descriptions of products provided in the previous sections the following products of the IGFS, which
need to follow certain standards and conventions canbe identiﬁed:

1134– Global gravity ﬁeld model as static and time variable
spherical harmonic series (ICGEM 1);– Gravity ﬁeld functionals on a grid (ICGEM 2);– Land and marine gravity data (BGI 1);– Absolute gravity stations (BGI 2);– Regional geoid solutions (ISG 1).
Those products which are not mentioned above either
shall not be regarded as a data product (e.g. geoid software, schools) or are not speciﬁed in suﬃcient detail inorder to identify if standards and conventions play arole.
Table 4.7 provides a summary of the identiﬁed standards and conventions of the above mentioned products for diﬀerent classes of standards. In order to keep
a complete overview and later on to identify dependencies between other product classes (e.g. geometricproducts deﬁned in Sections 4.1 to 4.4) we intentionally left in all standards, even if there is no dependency
at all for the gravimetric products.

Inventory of Standards and Conventions: 4 Product-based review

This fact is unacceptable and should be addressed (andsolved) within GGOS.
Summary of recommendations on gravity ﬁeld:
Recommendation 5.1 : A centralized web access to
all IGFS products and services maintained by the
IGFS should be established. This shall include descriptions of the various products provided under the
IGFS.
Recommendation 5.2 : IGFS products need to beclearly speciﬁed in terms of standards and conventions as well as algorithms applied.
Recommendation 5.3 : Inactive services and/or outdated information should not be considered anymore
as inherent part of the IGFS.
Recommendation 5.4 : All IGFS products to be delivered under the umbrella of GGOS should be publicly available for research applications. Otherwise
these products should not be advertised anymore as
GGOS supported products. The IGFS should provide
a list of its products, which are declared as GGOS
products.

4.5.7 Open problems and recommendations
The IGFS web site should act as an umbrella for all its
services. It is strongly recommended to renew this web
site and to provide descriptive documentation about theservices and its products. Ideally, a document describing the products of the IGFS Services and the standards
and conventions applied shall be made available there.
More detailed information can be provided at the individual services web sites.
The services of the IGFS shall ensure that all metadata
required to make use of their products are delivered
together with the products. In order to make productconversions to diﬀerent representations or reference systems the required algorithms could be described in the
IGFS Services documentation. For this purpose it isrecommended to create a unique document per service(or even better for the IGFS), where these algorithms
are described in detail.
Some services of the IGFS provide poorly structured
and sometimes outdated information about their products. In order to keep these services alive an update of
the services web sites is strongly recommended. This
speciﬁcally addresses the ICET and IDEMS.
Further remark on BGI and IDEMS: Much of the collected data of these services is not in the public domain.
Although they appear as IAG Services, these data are
not available for research within IAG, i.e. they are notdelivered even to researchers working in IAG projects.

4.6 Height systems and their realizations
4.6.1 Overview
Currently, a formal GGOS height systems product oran IAG Height Systems Service does not exist. However, the availability of geodetic space techniques, especially GNSS and dedicated-gravity ﬁeld missions (i.e.,
CHAMP, GRACE, GOCE), motivates the combinationof current geodetic products to determine gravity ﬁeldrelated heights. This combination is normally performed
following the relation h − H − N = 0. The ellipsoidal
heights (h) are derived from GNSS positioning while
the geoid or quasi-geoid models (N ) are computed combining satellite and terrestrial (aerial, marine) gravity
data. The physical heights (H) are usually obtained
from spirit levelling (+ gravity reductions) referring tolocal vertical datums.
The determination of ellipsoidal heights is expected toconform to the IERS and IGS standards, since theseheights depend on the geocentric Cartesian coordinatesand on the size, orientation, and position of the reference ellipsoid used for their transformation into ellipsoidal coordinates. For the computation of the (quasi-)
geoid, a compilation of standards (like the IERS conventions) is not available. The processing of CHAMP,GRACE and GOCE data is well-documented in the4.6 Height systems and their realizations

1135

Table 4.7: Summary of the identified standards and conventions for gravity and geoid related products. The acronym n/a denotes“not applicable for this product”. This means that according to our assessment there is no dependency between the product and thestandard. If “unknown” is stated, it means that according to our assessment that there is or might be a dependency of the product on
this standard, but that no information could be found in the available product descriptions.

General Standards & Conventions

ICGEM 1ICGEM 2

BGI 1

BGI 2

ISG 1

Speed of light

n/a

n/a

n/a

n/a

n/a

Time System

n/a

n/a

n/a

n/a

n/a

n/a

Reference ellipsoid indicated in
product

Gravitational constant of the Earth

Newton’s gravitational constant

Reference ellipsoidchosen by user

FA and Bouguer
anomalies based on
GRS67

Equatorial radiusof the Earth

Reference radius provided in
product.

Reference ellipsoidchosen by user.

FA and Bouguer
anomalies based on
GRS67

n/a

Reference ellipsoid indicated in
product

Flattening of the
Earth

n/a

Reference ellipsoidchosen by user

FA and Bouguer
anomalies based on
GRS67

n/a

Reference ellipsoid indicated in
product

Terrestrial reference frame

n/a

n/a

n/a

n/a

Reference frame
indicated in
product

Celestial reference
frame

n/a

n/a

n/a

n/a

n/a

Earth’s Gravity
Field

ICGEM 1ICGEM 2

BGI 1

BGI 2

ISG 1

A priori model

n/a

n/a

n/a

n/a

n/a

Permanent tidesystemPermanent tidesystem indicated in
product

Permanent tidesystem chosen byuser

unknown

unknown

Permanent tidesystem indicated in
product

Earth
Orientation Parameters

ICGEM 1ICGEM 2

BGI 1

BGI 2

ISG 1

A priori
informationn/aReference ellipsoidchosen by user

n/a

IERS polar motion
coordinates

Reference ellipsoid indicated in
product

Interpolation of apriori values

n/a

n/a

n/a

n/a

n/a

Subdaily ocean
tidal effects

n/a

n/a

n/a

n/a

n/a

Atmospheric tidal
effects

n/a

n/a

n/a

n/a

n/a

Nutation model

n/a

n/a

n/a

n/a

n/a

Precession model

n/a

n/a

n/a

n/a

n/a

Subdaily nutation

n/a

n/a

n/a

n/a

n/a

UT1 libration

n/a

n/a

n/a

n/a

n/a

Inventory of Standards and Conventions: 4 Product-based review

1136
Table 4.7 continued

Station
Coordinates

ICGEM 1ICGEM 2

BGI 1

BGI 2

ISG 1

Solid Earth tides

n/a

n/a

n/a

Potential, wave
groups, delta
factorsn/aPermanent tide

n/a

n/a

n/a

unknownn/aSolid Earth pole
tide

n/a

n/a

n/a

unknownn/aOceanic pole tide

n/a

n/a

n/a

unknownn/aTidal Ocean
Loading

n/a

n/a

n/a

Wave groups, amplitudes, phasesn/a

Non-tidal ocean
loading

n/a

n/a

n/a

unknownn/aTidal atmosphericloading

n/a

n/a

n/a

unknownn/a

Non-tidal atmospheric loading

n/a

n/a

n/a

unknownn/a

IGFS
Specific Standards

ICGEM 1ICGEM 2

BGI 1

BGI 2

ISG 1

Horizontal coordinates (latitude/
longitude) referencen/aEllipsoidal coordinates for reference
ellipsoid

unknown

GRS80

Coordinate reference indicated in
product

Vertical coordinates (height)
referencen/aHeight above reference ellipsoid

Indicated per data
point

Physical height

Height above indicated reference
ellipsoid

Spherical harmonicseries truncationn/aTruncation degree
defined by user

n/a

n/a

n/a

Gaussian filter(filter length, filter
degree)n/aFilter parameters
defined by user

n/a

n/a

n/a

Standard densityof Earth crustn/a2670 kg/m3

2670 kg/m3

n/a

unknown

Air pressure
correction

n/a

n/a

unknownStandard atmosphere & barometric admittancen/a

speciﬁc guidelines [Dahle et al. 2007; T. Gruber et al.
2010; Lühr et al. 2002]. However, the computation of
the long-wavelength constituents of the (quasi-)geoid(degree n ≤ 180 in a spherical harmonic expansion) produces diﬀerent results depending on the combination ofsatellite-based gravity data and the processing strategy
used for the estimation of the spherical harmonic coefﬁcients. The medium to short-wavelength componentsof the (quasi-)geoid (n > 180) are usually estimated by
combining terrestrial (airborne, marine) gravity data
and the gravitational eﬀects of the topography derived
from digital terrain models. In this case, information

about the mass density (either by digital density models or density hypotheses) is also necessary.
For the treatment of the terrestrial gravity, the standards published with the International Gravity Standardization Net 1971 (IGSN71) [Morelli et al. 1974] andthe International Absolute Gravity Basestation Network (IAGBN) [Boedecker 1988] are available. Nevertheless, there are still large data bases referring to theold gravity reference called Potsdam system [Borrass
1911]. Gravity surveys with geophysical purposes (e.g.,
oil exploration) are in general not freely available andthe standards applied to their processing are not clear.

4.6 Height systems and their realizations

The determination of the existing physical heights initially follows two basic conventions: (1) the geoid coincides with the mean sea level and (2) the corresponding
vertical coordinate must be the orthometric height. The
realization of these conditions was carried out by estimating the local mean sea level at selected tide gauges
and by means of geodetic levelling in combination withgravity reductions. It should be stressed that orthometric heights depend on the mass density distribution
in the Earth’s interior which is not known at a sufﬁcient degree. Any hypothesis about the density distribution creates a diﬀerent realization of the orthometric height system, but also of the geoid as a levelsurface running in the Earth’s interior over the continents. Currently, some height systems are based on
normal heights and the quasi-geoid as the reference surface. Geoid and quasi-geoid are practically identical in
marine areas, and the realization of the quasi-geoid isalso given by the local mean sea level at the reference
tide gauges. In general, the existing physical heights not
only refer to diﬀerent (unconnected) levels but are also
static (without considering variations in time) and contain large uncertainties caused primary by systematic
errors in levelling, omission or diﬀerent approximationsin the gravity reductions, and non-modeled eﬀects in
the height determination (more details in Table 4.8).
Considering these characteristics, it is clear that thestate-of-the-art allows the combination of ellipsoidal andphysical heights with (quasi-)geoid models with an accuracy varying from some cm up to 2 m. This may satisfy some practical applications, but measuring, understanding and modeling global change eﬀects with magnitudes at cm- or mm-level is not possible. The solution of these deﬁciencies requires the establishment ofa gravity ﬁeld-related global vertical reference system,
capable of supporting the standardization (uniﬁcation)of the existing height systems and the precise combination of physical and geometric heights globally. The
implementation of such a vertical reference system is amain objective of GGOS (see GGOS Focus Area 1: Unified Height System in GGOS 2020 Action Plans 2011–2015, unpublished) and the success of this initiative
has to be necessarily supported by a clear statement ofstandards and conventions.

4.6.2 Summary of standards
As a ﬁrst attempt, the inventory of the standards usedin height systems concentrates on the eﬀects removed
or retained in the diﬀerent coordinates associated withvertical positioning; i.e., those corrections (or reductions) applied to the instantaneous station positions

1137

to generate regularized or quasi-static coordinates. The
coordinates considered are: geometry on land (station
positions derived from GNSS positioning), terrestrial
gravity (relative and absolute gravity values measured
on the Earth’s surface), geopotential numbers (derived
from levelling in combination with gravity reductions),and (quasi-)geoid models. To identify which standards
have to be taken into account in this inventory, Table
4.9 summarizes the magnitude of the main eﬀects currently considered.
Apart from the eﬀects caused by secular changes (represented by the so-called station velocities), the largest
magnitudes are related to the treatment of the permanent tide (see Section 3.2). In the case of the geometrical coordinates (i.e., ITRS/ITRF), the realization of
the tide-free system is based on the elastic response of
the Earth to the semidiurnal components of the tidal
potential (cf. nominal Love numbers [Petit et al. 2010,
Chapters 6 and 7]). This approximation is called conventional tide-free system. In the terrestrial gravity andspirit levelling processing, the tide-free system assumes
the Earth in a hydrostatic equilibrium (cf. secular or
ﬂuid limit Love numbers [Munk et al. 1960]). This approximation is called tide-free system. These two diﬀerent approximations cause discrepancies up to 0.16 m in
the tide-free vertical coordinates. The computation ofthe (quasi-)geoid is done in tide-free or zero-tide system. However, some models apply the elastic response
approximation and others apply the hydrostatic equilibrium condition. In this way:
– the geometric coordinates are given in the conventional tide-free system;– the terrestrial gravity data are given in general in
the zero-tide system (following the IAG Resolution
No. 16, 1983), but some values determined before 1983
refer to the tide-free system;– the geopotential numbers are given in the tide-free,zero-tide or mean-tide system. This depends on theapplication of the so-called astronomical reduction tolevelling. This reduction produces coordinates in the
tide-free system. If the indirect eﬀect of the permanent tide is restored, they are given in the zero-tidesystem. If the astronomical reduction is not taken
into account, the geopotential numbers are assumed
to be in the mean-tide system;– the global gravity models and the derived (quasi-)
geoid models are published in conventional tide-freeor zero-tide system. The mean-tide system is also
used especially for oceanographic applications.

Inventory of Standards and Conventions: 4 Product-based review

1138

Table 4.8: Characteristics and present status of the existing physical height systems.

Characteristics

Present status
Reference level and vertical datum– Definition: the geoid according to Gauss 1876 andListing 1873.
– Basic convention: the geoid coincides with theundisturbed mean sea level.
– Realization: mean sea level averaged over a certain
period of time at an arbitrarily selected tide gauge.
– Remark: The interpretation of this convention haschanged over the years depending on the type andquality of geodetic observations and analysis strategies
available for modeling both the mean sea surface andthe geoid, e.g., [Ekman 1995; Heck 2004; Heck et al.
1990; Mather 1978; Sánchez 2012].

– There are as many vertical datums as reference
tide gauges (at present more than 100 worldwide) andthe reference levels relate to diﬀerent determination
epochs.
– Height systems based on the quasi-geoid realize thereference level and the vertical datum in the same manner because geoid and quasi-geoid are practically identical in ocean areas and at the coast lines (where thetide gauges are established).

Vertical coordinates– Definition: orthometric heights (as tacit consequence of introducing the geoid as the reference surface).
– Realization: levelling with gravity reductions (often
using normal gravity instead of observed surface gravity).
– No convention about the gravity reduction (sometimes no reduction).
– Remark: Normal heights and quasi-geoid are preferred in some countries/regions.

– Vertical coordinates realize diﬀerent orthometricheight types depending on the applied hypothesis.
– There is no unique relation between reference surface
and vertical coordinates if the geoid is not computed
using the same hypotheses applied for the orthometricheights.
– The determination of normal heights does not dependon any hypothesis, but only on the parameters of thereference ellipsoid. The same holds for the quasi-geoid.

Reference frames– The vertical control over continental areas has been
extended by means of spirit levelling along vertical networks.
– Drawbacks: levelling is very time-consuming andthe systematic errors signiﬁcantly grow with the distance from the reference tide gauge.

– Most of the vertical networks have been measured
piece-wise over very long time periods and the verticalcoordinates refer to diﬀerent epochs.
– The estimation of vertical displacements at levelling
points by spirit levelling is very diﬃcult (expensive)
and in most cases they are neglected.
– The accuracy of the heights is limited regionally by
the error propagation of spirit levelling to dm-level inremote areas and globally by the datum realization tom-level.

4.6 Height systems and their realizations

The tide-generating potential is modeled according to :– for the geometric coordinates (IERS Conventions):
Cartwright et al. [1973, 1971]. Transformation parameters to the models of Doodson [1921] and Hartmann et al. [1995] are also provided;– for the CHAMP, GRACE, and GOCE data: the sameas the IERS Conventions;– for the terrestrial gravity: in addition to Cartwright[Cartwright et al. 1973, 1971], the Longman [1959]
formulation was also widely applied before IGSN71.
In recent years, the model of Hartmann et al. [1995]
is also used.
The changes induced by the solid Earth tides (estimatedby means of Love numbers) in the IERS Conventions
are computed following the models of Wahr [1981] andMathews et al. [1995] in combination with the model
Preliminary Reference Earth Model (PREM) [Dziewonski et al. 1981]. Further corrections for the anelasticityof the mantle and resonance eﬀects caused by oceanic
currents and tides, and the Chandler wobble, the retrograde Free Core Nutation (FCN) and the prograde Free
Inner Core Nutation (FICN) are also included. The estimation of the pole tide and ocean pole tide eﬀects
is based on [Wahr 1985], but using the so-called fluidLove numbers [Munk et al. 1960], i.e., the deformation
for an Earth in hydrostatic equilibrium. Here it shouldbe mentioned again that the direct deformation of the
Earth’s surface caused by the tide-generating potential
is estimated applying (frequency-dependent) Love numbers for an elastic Earth. The ocean pole tide loading
is computed using the model of equilibrium of Desai[2002]. The pole tide and ocean pole tide loading effects in GRACE and GOCE and in terrestrial gravity
data of high-precision (absolute and superconducting
gravimetry) are computed as in the IERS Conventions.
The ocean loading eﬀects in the geometric coordinates
are modeled according to Farrell [1972] and using theconventional computation routine of Scherneck [1991]
described in the IERS Conventions. The ocean tidemodels preferred by the IERS are TPXO 7.2 [Egbert
et al. 1994] and FES2004 [Letellier et al. 2005], whilein the analysis of GRACE and GOCE data the model
FES2004 is used.
Non-tidal eﬀects (from ocean, atmosphere and hydrology) are not removed from the geometrical coordinates;i.e., these eﬀects are included in the station positions.
In the IERS Conventions, the atmospheric tidal eﬀects
caused by the solar diurnal and semidiurnal components are modeled according to [R. D. Ray et al. 2003],
while in the GRACE data processing the model of Biancale et al. [2006] is used. GOCE data processing does1139

not reduce this eﬀect directly; it is modeled together
with non-tidal eﬀects.
The non-tidal eﬀects in the case of GRACE and GOCE
are understood as short-term mass variations of theatmosphere-ocean system. The corresponding eﬀects are
reduced from the spherical harmonic coeﬃcients directly
to get a quasi-stationary representation of the Earth’s
gravity ﬁeld. The estimation of this reduction is basedon the Ocean Model for Circulation and Tides (OMCT)[Thomas 2002] combined with the numerical weathermodels produced by the European Center for Medium-Range Weather Forecasts (ECMWF). Hydrologicaleﬀects are assumed to be contained in the epoch-gravity
models computed from GRACE.
In the computation of terrestrial gravity anomalies, theatmospheric eﬀects are modeled by means of a standard
atmosphere, i.e., a spherical model considering radial
density changes only. In some cases, this approximation is reﬁned by taking into account the perturbations
caused by the terrain irregularities in the atmosphereEarth surface coupling. The estimation of this reduction
is based on an inverse Bouguer plate with the meandensity of the atmosphere.
Regarding the level diﬀerences measured by geodeticlevelling, the only applied reduction is the astronomicalcorrection; the other eﬀects (like pole tide, ocean poletide, non-tidal loading, etc.) are considered insigniﬁcant[Heck 1984].

4.6.3 Discussion and deficiencies
According to the summary presented in the previous
sections, the largest discrepancies of the existing heightsystems and their combination with geometrical heightsand (quasi-)geoid models are caused by:– diﬀerent reference levels (i.e., zero-height surfaces) in
the local height systems;– datum inconsistencies associated with the individual
vertical coordinates, e.g., no coincidence between thezero-height level of the vertical networks and the levelof the (quasi-)geoid models;– omission or diﬀerent approximations in the computation of gravity reductions in the levelling data; i.e.,
diﬀerent types of physical heights (orthometric, normal, normal-orthometric, etc.);– vertical coordinates associated with diﬀerent reference epochs (in general, dH/dt is unknown and therefore omitted);Inventory of Standards and Conventions: 4 Product-based review

1140

Table 4.9: Summary of geophysical effects and their magnitudes.
EffectGeopotential
numbers

Geometry on land

Terrestrial gravityhydrostatic equilibrium

Solid Earthpermanent tideelastic response of theEarth−0.12 m at pole,+0.06 m at equator, orhydrostatic equilibrium−0.28 m at pole,+0.14 m at equator

Periodic componentsof the Solid Earth tide(modeled as elastic
response of the Earth)at pole :−0.18 m (Moon),−0.08 m (Sun),at equator :+0.36 m (Moon),+0.16 m (Sun)Moon :µm−1.1 to +0.5 2 ,
s
Sun :
µm
−0.5 to +0.3 2sMoon :±0.056 mm per km oflevelling,Sun :±0.026 mm per km oflevelling

Solid Earth pole tide(modeled as hydrostatic
equilibrium)±0.0270 m (vert),±0.0070 m (hz)

< +0.082 µm s−2(at latitude 45◦ )±3 cm in 430 days

Oceanic pole tide(modeled as hydrostatic
equilibrium)±0.0018 m (vert),±0.0005 m (hz)equipotential surfaces
move as the geoid, but
simultaneously

at pole :+0.61 µm s−2
at equator :−0.30 µm s−2

unknown

Geoidanelastic response of
the Earth−0.19 m at pole,+0.10 m at equator

as undisturbed sea level−0.26 m at pole,+0.52 cm at equator±0.0270 m

negligible±0.0018 m

LOD variations (modeled as hydrostatic
equilibrium)

up to 1 m

0.0007 to 0.007µm
s2

negligible

negligible

Tidal ocean loading±0.10 m±(0.01 to 0.02)µm
s2

negligible

unknown

Non-tidal ocean loading

unknown

unknown

unknown

Tidal atmosphericloading±0.0015 m< 0.003 µm s−2

negligible

Non-tidal atmosphericloading

unknown−0.003 to − 0.004µm s−2 /hPa

unknown

Tidal hydrologic loading (groundwater)±0.050 m

Non-tidal hydrologic
loading (groundwater,snow, ice)

±0.050 m

Secular changes (liketectonics, GIA, subsidence, etc.)

up to 0.1 m/yr

unknown

negligible

0.05 to 0.1 µm s−2

unknown– systematic eﬀects and distortions, e.g., long-wavelength (quasi-)geoid errors, poorly modeled radial effects in GNSS positioning, over-constrained levelling
network adjustments, systematic errors in levelling,etc.;– assumptions and theoretical approximations taken
into account for the data processing; e.g., hypotheses in geoid and orthometric height computation, atmospheric delay in GNSS, neglecting ocean dynamic
topography at tide gauges, etc.;– dissimilar approaches to reduce the same eﬀect in thediﬀerent height types, in particular, the treatment of
the luni-solar permanent tide;

unknown

up to 0.1 m/yr

10 mm
in 100 to 1000 km
unknown
15 mm
in 20 to 2000 km
unknown
10 to 12 mm
in 10 to 8000 km

unknown– systematic and random errors in the diﬀerent heighttypes h, H, and N .
To overcome these deﬁciencies, it is necessary, among
other tasks,– to unify (standardize) the existing height systems;
i.e., to refer all physical heights to one and the samereference level (deﬁned and realized globally);– to introduce geopotential numbers as the primaryvertical coordinate in order to avoid inconsistencies
caused by diﬀerent gravity reductions in the height
determination;– to guarantee that geometrical and physical heights
represent the same Earth’s surface geometry; i.e., the4.6 Height systems and their realizations

so-called regularized station positions should include
consistent reductions, especially the treatment of thepermanent tide. In the same way, the secular changes
should be included in both representations: geometrical (dh/dt) and physical (dH/dt) heights;– to adopt a conventional global gravity model to be
used as the long-wavelength component in the estimation of (quasi-)geoid models of high resolution.
Table 4.10 shows some examples about the requirements and present limitations concerning the combination of physical and geometric heights.

1141

IGFS and ICGEM: to identify the most appropriate
global gravity model to compute the long-wavelengthcomponents of the global reference surface.
BGI and IAG Sub-commissions 2.1 (Gravimetry and Gravity Networks) and 2.4 (Regional
Geoid Determination): to improve the availabilityof terrestrial (shipborne and airborne) gravity data
for the computation of the medium-wavelength components of the global reference surface.
IDEMS: to identify the most appropriate elevation
models to estimate the terrain eﬀects in the (quasi-)
geoid modeling (short-wavelength components of the
global reference surface).

4.6.4 Links to other productsThis list is far from being complete and it includes expected products, which currently do not exist or havenot been considered by some IAG/GGOS components.

To best exploit the advantages oﬀered by space geodetic
techniques, especially in the combination of GNSS positioning and satellite-based (quasi-)geoid models, modern height systems should support with high precision
the integration of physical and geometrical coordinates.
For that purpose the interaction of the following IAG/
GGOS components and products is necessary

4.6.5 The IAG resolution for the definition andrealization of an International Height
Reference System (IHRS)IERS and IGS: to recognize the standards applied forthe computation of the geometric vertical coordinates
and to align (if necessary) these standards with thoseoutlined/applied by the gravity community.

A ﬁrst concrete step oriented to the establishment of aworldwide uniﬁed (standardized) vertical reference system is the release of an IAG resolution for the definition and realization of an International Height Reference System (IHRS). This resolution was issued during
the IUGG 2015 General Assembly and outlines ﬁve basic conventions for the deﬁnition of the IHRS. The deﬁnition is given in terms of potential parameters: the vertical coordinates are geopotential numbers (−∆WP =CP = W0 − WP ) referring to an equipotential surfaceof the Earth’s gravity ﬁeld realized by the IAG conventional value W0 = 62 636 853.4 m2 s−2 . The spatial reference of the position P for the potential WP =W (X) is given by coordinates X of the ITRF. This resolution also states that parameters, observations, anddata should be related to the mean tidal system/meancrust. This is in contradiction with the IAG resolution
No. 16 (1983); however, the mean tidal system is necessary to support oceanographic applications, especiallyin coastal areas. In this way, a clear statement for thetransformation of the IHRS products from one tide system to the others is required. More details about thefoundations of this IAG resolution can be found in [Ihdeet al. 2015] and [Sánchez et al. 2015].

IGS Working Group Tide Gauge Benchmark
Monitoring (TIGA) and Permanent Service
for Mean Sea Level (PSMSL): to connect the local height-zero levels to the terrestrial reference frame
and to model the sea surface topography at the reference tide gauges.

At present, the main challenge is the realization of the
IHRS; i.e., the establishment of the International Height
Reference Frame (IHRF). It is expected that the IHRF
follows the same structure as the ITRF: a global network with regional and national densiﬁcations, whose
geopotential numbers referring to the global IHRS are

GGOS Focus Area 1 Unified Height System: toassess its requirements for the deﬁnition and realization of a uniﬁed global vertical reference system.
IAG Commission 1 (Reference Frames): to identify strategies, standards and conventions needed toincrease the accuracy of the geometrical heights.
IAG Commission 2 (Gravity Field) and ISG(International Service for the Geoid): to identify strategies, standards and conventions needed toincrease the accuracy of the (quasi-)geoid modeling.
IAG Sub-commissions 1.3 (Regional Reference
Frames), 2.1 (Gravimetry and Gravity Networks) and 2.4 (Regional Geoid Determination): to assess the detailed characteristics of the existing height systems in order to extent the global
vertical reference frame activities to national and regional level.

Inventory of Standards and Conventions: 4 Product-based review

1142

Table 4.10: Requirements and present limitations concerning the combination of physical and geometric heights (taken from [Sánchez
2012]).

Requirement

Present status

Ellipsoidal heights h and (quasi-)geoid heights N mustbe given with respect to the same ellipsoid; i.e., thesame ellipsoidal parameters have to be used
– for the transformation of geocentric Cartesian coordinates into ellipsoidal coordinates,– as reference ﬁeld for the solution of the geodetic
boundary value problem,– for scaling global gravity models, etc.

– Diﬀerent ellipsoidal parameters (a, GM ) are appliedin geometry and gravity.
– h and N are given in diﬀerent tide systems; e.g,
– mean-tide system in oceanography, satellite altimetry, levelling,– conventional tide-free system in ITRF positions,
GRS80, some (quasi-)geoid models,– zero-tide system in some (quasi-)geoid models,terrestrial gravity data.

P

y
ph
a
r
og
Top

H
h

id
Geo

P

y
ph
a
r
og
Top

id
Geo

N

H
h

N

Ellipsoid( N)
Ellipsoid)oid(hEllipsPhysical heights H and (quasi-)geoid undulations N
must reﬂect the same reference surface; i.e., the heightreference surface H0 obtained by subtracting the physical height H from the ellipsoidal height h shall be consistent with the (quasi-)geoid derived from gravity (solution of the boundary value problem).

– Orthometric heights H and geoid models N obtained
from the solution of the boundary value problem arebased on diﬀerent hypotheses.
– H and N refer to diﬀerent tide systems.
– Systematic errors over long distances in levelling reduce the reliability of H0 .

p
ra
g
po
To

id =
Geo

H
h

H0

d
Ellipsoi

P
hy

hy

P

p
ra
g
po
To

Hp
h

H0

N

id
Geo
EllipsoiNd4.6 Height systems and their realizations

1143

Table 4.10 continued

Requirement

Present status

Physical heights H and ellipsoidal heights h must represent the same Earth’s surface– H and h refer to diﬀerent epochs and, in the mostcases, dH/dt is unknown.
– Diﬀerent reductions (for Earth-, ocean-, atmospherictides, ocean and atmospheric loading, post-glacial rebound, etc.) are applied.

P

P

ap
gr p
o
p
a
To
gr
o
Top

id
Geo

y(

)

h
ap
r
g
po
p
To
ra
g
o
To p

H

)

hy
(h

hy
hy (H
(h

)

H
h

N

id
Geo

)

H
h

N

d
EllipsoidEllipsoi

known. According to the GGOS objectives, the target
accuracy of these global geopotential numbers is 1·10−2
m2 s−2 . In practice, the precise realization of the IHRS
is limited by diﬀerent aspects; for instance, there are
no uniﬁed standards for the determination of the potential values WP , the gravity ﬁeld modeling and theestimation of the position vectors X follow diﬀerent
conventions, the geodetic infrastructure is not homogeneously distributed globally, etc. This may restrict
the expected accuracy of 1 · 10−2 m2 s−2 to some orders
lower (10 · 10−2 m2 s−2 to 100 · 10−2 m2 s−2 ). Consequently, the next step is to outline the minimum set offundamentals needed for a reliable and sustainable realization of the IHRS. These activities are being facedby the joint working group Strategy for the Realizationof the International Height Reference System (IHRS),
which is a common initiative of GGOS Focus Area 1,
IAG Commission 2 (Gravity ﬁeld), IAG Commission
1 (Reference Frames), IAG Inter-commission Committee on Theory (ICCT), and the International Gravity
Field Service (IGFS). The expected main result is adocument similar to the IERS conventions; i.e. a sequence of chapters describing the diﬀerent components
to be considered for the realization of the IHRS and its
practical utilization.

The activities of this working group are based on the
results presented by previous work, in particular thoseof the IAG Inter-Commission Project 1.2: Vertical Reference Frames (conventions for the deﬁnition of WorldHeight System, 2003–2011), GGOS Focus Area 1 on theuniﬁcation of height reference systems (since 2011), the
ESA project GOCE+ Height System Unification with
GOCE (2011–2014), the BPS (inventory of standards
and conventions used for the generation of IAG products, since 2009), and the Joint Working Group on Vertical Datum Standardisation (2011–2015).

4.6.6 Open problems and recommendations
To improve the standardization of the existing heightsystems, it is necessary, among other issues, that metadata describing the characteristics of the existing heightsystems be implemented. These meta-data should include for instance:– epoch and time span applied for the mean sea level
introduced as a zero-height;– changes of the mean sea level and vertical position of
the reference tide gauges;

1144– information about the levelling techniques applied toextend the vertical control through the countries;– gravity reductions applied to the measured level differences;– precision of levelling and gravity data;– epoch and tide system to which the vertical coordinates refer, etc.
When this information is available, it would be possible
to transform the existing physical heights in such a waythat they can be combined with GNSS positioning and(quasi-)geoid models consistently. For that purpose, itis necessary to involve the national agencies responsible
for the maintenance of vertical networks.
Since the vertical datum uniﬁcation is based on the
combination of levelling data (+ gravity reductions),
GNSS positioning and (quasi-)geoid modeling, it is convenient to outline the minimal requirements to be satisﬁed by those stations used for this purpose. For instance, it is well-known that the vertical coordinates
derived from GNSS positioning are strongly inﬂuenced
by systematic errors and physical phenomena that reduce their accuracy considerably. The determination of
the level discrepancies between diﬀerent height systems
should be determined including the most precise ellipsoidal heights only; i.e., at ITRF stations and regional
densiﬁcation stations like EPN, SIRGAS, NAREF, etc.
These stations must also be connected by spirit levelling to the reference tide gauges; and gravity measurements along the levelling lines must be available
for the computation of the corresponding geopotential
numbers. Complementarily, the geoid models of highresolution should be estimated in a consistent manner.
Currently, the geoid computation is not a uniﬁed or
standardized procedure, and it is possible to ﬁnd diﬀerent geoid models over the same region although they arebased on the same input data, i.e., there are as manygeoids as computations. In addition, it is usual to compute improved geoid models, if new gravity data andnew analysis strategies are available; however, it is notclear how frequently the geoid should be updated.

Inventory of Standards and Conventions: 4 Product-based review

From the organizational point of view, it is necessarythat the IAG/GGOS components named in the previous section precisely outline which products are under
their responsibility and how they are generated. As aﬁrst step, a description similar to the IERS Conventions
should be implemented for each product. The standards
outlined by each IAG/GGOS component must be classiﬁed into a hierarchical structure, showing which ofthem have to be followed by everyone, which of them
are applicable in geometry or gravity only, which ofthem are technique-speciﬁc, etc. Missing products mustbe identiﬁed and the necessary actions taken for theirgeneration. This procedure has to be extended also to
the marine and ﬂuvial areas. At present, the discussion
concentrates on the height systems on land areas; but
the vertical coordinates on water and ice areas should
also refer to the same global uniﬁed height system.
Summary of recommendations on height systems:
Recommendation 6.1: It is necessary that the IAG/
GGOS components involved in the vertical coordinate determination should outline precisely which
products are under their responsibility and how they
are generated.
Recommendation 6.2 : To achieve the standardization of the existing height systems, it is necessary,among others, that meta-data describing the characteristics of the existing height systems be implemented.
Recommendation 6.3 : Since the vertical datum
uniﬁcation is based on the combination of levelling
data (+ gravity reductions), GNSS positioning, and(quasi-)geoid modeling, the minimal requirements to
be used for stations should be outlined.

1145

5 Summary
The GGOS Bureau of Products and Standards (BPS),
a redeﬁnition of the former GGOS Bureau for Standards and Conventions (BSC) is operated by DGFI andIAPG of the Technische Universität München, within
the Forschungsgruppe Satellitengeodäsie (FGS). The
work of the BPS is primarily built on the IAG Services and the products they derive on an operational
basis from various geodetic observation techniques such
as VLBI, SLR/LLR, GNSS, DORIS, altimetry, gravity
satellite missions, gravimetry, etc. The purpose and major goal of the BPS is to support GGOS in its goal toobtain consistent products describing the geometry, rotation and gravity ﬁeld of the Earth, along with its variations in time. In this context, it is essential to provide
recommendations and guidelines to ensure that common standards and conventions are adopted and implemented by the IAG components.
According to its Terms of Reference, it is a key activity of the BPS to assess the standards and conventions
currently adopted and used by IAG and its components for the processing of geometric and gravimetricobservations as basis for the generation of IAG products. The outcome of this assessment is published inthis document. This inventory gives a brief introduction into GGOS, including its mission and objectives
and an overview about its structure. It presents some
general information on standards and conventions andsummarizes the current standards, standardized units,fundamental physical constants, resolutions, and conventions that are relevant for geodesy.
Chapter 3 provides the status regarding numerical standards, including time and tide systems and the geopo-

tential value W0 . As shown in the inventory diﬀerent
sources for numerical standards are currently in use
and the fundamental parameters are partly given in
diﬀerent time and tide systems, which is a potential
source for inconsistencies and even errors in geodetic
products. Thus, it is essential that the numerical standards and applied conventions be clearly documented
for all geodetic products.
The key element of this document is the product-based
inventory (Chapter 4) which addresses the following
major topics:
Section 4.1 Celestial reference systems and frames,
Section 4.2 Terrestrial reference systems and frames,
Section 4.3 Earth orientation parameters,
Section 4.4 GNSS satellite orbits,
Section 4.5 Gravity and geoid,
Section 4.6 Height systems and their realizations.
As a major outcome, this inventory presents for each ofthese products (or topics) the current status regarding
standards and conventions, identiﬁes gaps and inconsistencies, and provides recommendations for improvements. At the end of each section the most important
recommendations for each product (or topic) are summarized. These recommendations should be discussedwith the dedicated experts in the ﬁeld and future actions and responsibilities should be deﬁned to resolve
the remaining issues.
As the list of products addressed in the current version of this inventory is by far not complete, additional
products that may be speciﬁed as IAG products will be
included in an updated version of this document.

Inventory of Standards and Conventions: 5 Summary

1146

Glossary
AC
ACC
AGN
APKIM
ASI

Analysis Center.
Analysis Center Coordinator.
Active Galactic Nuclei.
Actual Plate KInematic Model.
Agenzia Spaziale Italiana.

GCRS
GEO
GEOSS

BCRS
BGI
BIH
BIPM
BKG
BPS
BSC

Barycentric Celestial Reference System.
Bureau Gravimetric International.
Bureau International de l’Heure.
Bureau International de Poids et Mesures.
Bundesamt für Kartographie und Geodäsie.
GGOS Bureau of Products and Standards.
GGOS Bureau for Standards and Conventions.

GGIM
GGOS
GGRF
GIA
GIAC
GIS
GMF
GNSS
GPS
GPT
GRS
GRS80
GSFC

CBE
Current Best Estimates.
CEOS
Committee of Earth Observation Satellities.
CIP
Celestial Intermediate Pole.
CLS
Collecte Localisation par Satellite.
CM
Center of Mass.
CNES
Center National d’Etudes Spatiales.
CODATA Committee on Data for Science and Technology.
CODE
Center for Orbit Determination in Europe.
CTRS
Conventional Terrestrial Reference System.
DEM
DGFI
DLR
DORIS

Digital Elevation Model.
Deutsches Geodätisches Forschungsinstitut.
Deutsches Zentrum für Luft- und Raumfahrt.
Doppler Orbit Determination and Radiopositioning Integrated by Satellite.

GFZ

IAG
IAGBN
IAPG
IAU
ICET
ICGEM
ICRF
ICRF2

ECMWF European Center for Medium-Range Weather
Forecasts.
EOP
Earth Orientation Parameters.
EPN
EUREF Permanent GNSS Network.
ERF
Epoch Reference Frame.
ERP
Earth Rotation Parameters.
ESA
European Space Agency.
EUREF IAG Reference Frame Sub-Commission for
Europe.

ICRS
ICSU
IDEMS

FA
FCN
FESG
FGS
FICN
FK5

IGN

Free-air Anomaly.
Free Core Nutation.
Forschungseinrichtung Satellitengeodäsie.
Forschungsgruppe Satellitengeodäsie.
Free Inner Core Nutation.
Fifth Fundamental Star Catalogue.

IDS
IERS
IGFS
IGG

IGS
IGSN71ILRS

Geocentric Celestial Reference System.
Group on Earth Observation.
Global Earth Observation System of Systems.
Helmholtz Centre Potsdam, German ResearchCentre for Geosciences.
Global Geospatial Information Management.
Global Geodetic Observing System.
Global Geodetic Reference Frame.
Glacial Isostatic Adjustment.
GGOS Inter Agency Committee.
Geographic Information System.
Global Mapping Function.
Global Navigation Satellite System.
Global Positioning System.
Global Pressure and Temperature.
Geodetic Reference System.
Geodetic Reference System 1980.
Goddard Space Flight Center.
International Association of Geodesy.
International Absolute Gravity Basestation
Network.
Institut für Astronomische und Physikalische Geodäsie.
International Astronomical Union.
International Center for Earth Tides.
International Center for Global Gravity Field
Models.
International Celestial Reference Frame.
Second Realization of the International Celestial Reference Frame.
International Celestial Reference System.
International Council for Science.
International Digital Elevation Model Service.
International DORIS Service.
International Earth Rotation and Reference
Systems Service.
International Gravity Field Service.
Institut für Geodäsie und Geoinformation,
University Bonn.
Institut National de l’Information Géographiqueet Forestiere, France.
International GNSS Service.
International Gravity Standardization Net
1971.
International Laser Ranging Service.

1147

IRNSS
ISG
ISO
ITRF
ITRS
IUGG
IVS

Indian Regional Navigation Satellite System.
International Service for the Geoid.
International Organization for Standardization.
International Terrestrial Reference Frame.
International Terrestrial Reference System.
International Union of Geodesy and Geophysics.
International VLBI Service for Geodesy andAstrometry.

JPL
JWG

Jet Propulsion Laboratory.
Joint Working Group.

LEO
LLR

Low Earth Orbiter.
Lunar Laser Ranging.

NAREF
NASA

North American Reference Frame.
National Aeronautics and Space Administration.
National Geospatial-Intelligence Center.
National Geodetic Survey.
National Institute of Standards and Technology.
No Net Rotation.
National Ressources Canada.
IAU Division A Working Group NumericalStandards for Fundamental Astronomy.

NGA
NGS
NIST
NNR
NRCan
NSFA
OGC
OMCT

Open Geospatial Consortium.
Ocean Model for Circulation and Tides.

PCO
PCV
PREM
PSMSL

Phase Center Oﬀset.
Phase Center Variation.
Preliminary Reference Earth Model.
Permanent Service for Mean Sea Level.

QZSS

Quasi-Zenith Satellite System.

SBAS
SI
SIRGAS
SLR
SOFA
SRP

Space Based Augmentation System.
International System of Units.
Geocentric Reference Frame for the Americas.
Satellite Laser Ranging.
Standards of Fundamental Astronomy.
Solar Radiation Pressure.

TCG
TDB
TEC
TIGA
TRF

Geocentric Coordinate Time.
Barycentric Dynamical Time.
Total Electron Content.
Tide Gauge Benchmark Monitoring.
Terrestrial Reference Frame.

TRS
TT

Terrestrial Reference System.
Terrestrial Time.

UN
USNO
UTC

United Nations.
United States Naval Observatory.
Coordinated Universal Time.

VLBI
VMF1

Very Long Baseline Interferometry.
Vienna Mapping Function 1.

WG
WGM
WGRF

Working Group.
World Gravity Map.
IAU Working Group on Reference Frames.

ZTD

Zenith Total Delay.

1148

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icalNotes/tn36.html.
Petrov, L. and J.-P. Boy (2004): “Study of the atmospheric pressure loading signal in Very Long Baseline Interferometry Observations”. Journal of Geophysical Research 109(B03405).
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Plag, H.-P. and M. Pearlman, eds. (2009): Global Geodetic Observing System – Meeting requirements of a
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Ratcliﬀ, T. and R. Gross (2010): Combinations of Earth
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Ray, J., Z. Altamimi, X. Collilieux, and T. van Dam(2008): “Anomalous harmonics in the spectra of GPS
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Ray, R. D. and R. M. Ponte (2003): “Barometric tides
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Rebischung, P., J. Griﬃths, J. Ray, R. Schmid, X. Collilieux, and B. Garayt (2012): “IGS08: the IGS realization of ITRF2008”. GPS Solutions 16(4), pp. 483–
494. doi: 10.1007/s10291-011-0248-2.

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IAG Scientific Services
International Bureau on Weights and Measures
Bureau International des Poids et Mesures (BIPM)– Time Department –Director of Department: Elisa Felicitas Arias (France)
http://www.bipm.org/metrology/time-frequency/

The Time Department is one of the four scientific departments of the BIPM. The activities at the Time Department
are focused on the maintenance of the SI second and theformation of the international reference time scales.
The BIPM provides, together with the US Naval Observatory, the IERS Conventions Centre, with the responsibilityof the establishment and publication of the IERS Conventions, providing standards and models for applications in
the fields of geodesy, geophysics and astronomy.
The establishment and maintenance of the International
System of Units (SI) at the BIPM constitutes a fundamental contribution to the activities relating to the IAG.

International Time Scales at the BIPM
The BIPM Time Department maintains the atomic timescales Coordinated Universal Time (UTC); the UTC rapid
solution (UTCr); and the realization of Terrestrial Time
TT(BIPM).
Coordinated Universal Time (UTC) is computed every
month and published BIPM Circular T. It is identical inrate to International Atomic Time TAI, their difference is
the integral number of (leap) seconds inserted in UTC toapproximate Earth’s rotation time UT1. The frequency
stability of UTC, expressed in terms of an Allan deviation,is estimated to 3 × 10-16 for averaging times of one month.
About 500 industrial clocks located in more than 70
national laboratories contribute to the calculation of thetimescales at the BIPM. Some of these laboratories
develop and maintain primary frequency standards –among them caesium fountains – that contribute to theimprovement of the accuracy of TAI. Twelve primary
frequency standards contributed to improve the accuracy of
TAI in 2015, including ten caesium fountains developed

and maintained in metrology institutes in China, France,
Germany, India, Italy, the Russian Federation, the United
Kingdom and the USA. Measurements of a Frenchrubidium secondary frequency standard have been also
regularly reported and included for improving the accuracyof TAI. The scale unit of TAI has been estimated to matchthe SI second to about 2 × 10-16 in average over the year.
The laboratories contributing to the formation of UTC
maintain representations of the international time scale
denominated UTC(k). Routine clock comparisons ofUTC(k) are undertaken using different techniques andmethods of time transfer. All laboratories contributing to
the calculation of UTC at the BIPM are equipped for
GNSS reception. GPS C/A observations from time andgeodetic-type receivers are used with different methods,
depending on the characteristics of the receivers. Dualfrequency receivers allow performing iono-free solutions.
Also combination of code and phase measurements of GPS
geodetic-type receivers (GPS PPP) is used in thecomputation of UTC. The observations of GLONASS are
regularly used for the computation of UTC, combined withGPS links. Some laboratories are equipped of two-way
satellite time and frequency transfer (TWSTFT) equipment
allowing time comparisons independent from GNSS
throughgeostationary
communication
satellites.
Combinations of TWSTFT and GPS PPP links arecomputed whenever possible. The statistical uncertainty oftime comparisons is at the sub-nanosecond level for thebest time links. In the frame of the cooperation between the
BIPM and the RMOs, the BIPM is implementing frequentcampaigns for characterizing the delays of GPS equipment
operated in a group of selected laboratories distributed in
the metrology regions with the aim of decreasing thecalibration uncertainty. The first campaign including nineinstitutes in three regions concluded at the end of 2015.

IAG Scientific Services

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The result is an improvement of the calibration uncertainty
in a factor of about 3 with respect to the previous 5 ns
value conventionally assigned to calibrated equipment(http://www.bipm.org/jsp/en/ TimeCalibrations.jsp). The
second campaign will start beginning of 2016, and we
expect to confirm that this uncertainty agrees with the timestability of the equipment. Results of campaigns organizedby the regions will maintain the calibration of all
equipment used for clocks comparison in UTC. TWSTFT
links have been calibrated in Europe confirming
nanosecond order uncertainty.
Research on time and frequency transfer techniques
resulted in the achievement of 1 × 10-16 frequency transfer
by GPS PPP with integer ambiguity resolution.
Since 1 July 2013 the Time Department has been
publishing the rapid solution UTCr every Wednesday(ftp://62.161.69.5/pub/tai/publication/utcr/). About 50
laboratories contribute to UTCr, representing 70% of theclocks in UTC; in consequence the frequency stability of
the rapid solution is similar to that of UTC.
Because TAI is computed on a monthly basis and has
operational constraints, it does not provide an optimalrealization of Terrestrial Time (TT), the time coordinate of
the geocentric reference system. The BIPM therefore
computes an additional realization TT(BIPM) in postprocessing, which is based on a weighted average of theevaluation of the TAI frequency by the primary frequency
standards. The last updated computation of TT(BIPM),
named TT(BIPM14) has an estimated accuracy of order3 u 10-16. The monthly extension of TT(BIPM) can bedirectly derived from TAI (ftp://tai.bipm.org/TFG/
TT(BIPM)/TTBIPM.14).
The process of improvement of the algorithm for UTC
has concluded in the period of this report. After the
implementation of the quadratic model for the clock
frequency prediction, fundamental changes were made in
the algorithm for the clock weighting. We have introduced
a new concept where the clock weight is based on its
frequency predictability, instead of using the frequency
stability as an estimator; these changes positively impact
the clock weight distribution and the stability of TAI in the
short and long terms.
Radiations other than the caesium 133, most in the
optical wavelengths, have been recommended by theInternational Committee for Weights and Measures(CIPM) as secondary representations of the second. Thesefrequency standards are at least one order of magnitude
more accurate than the caesium. Their use for time
metrology is conditioned by the progress in very accurate
frequency transfer, allowing comparisons of thesestandards at the level of their performances. Substantial
progress has been made in the use of optical fibres forfrequency comparisons over up to 1000 km, but still work
is to be done for extending these comparisons to time andfor the implementation of permanent fibre links betweenUTCcontributing
laboratories.
Intercontinental
comparisons are still under study using space techniques.
The time and frequency metrology community is engaged
in a collective effort for solving this issue, since one of theinterests is the redefinition of the SI second.
The computation of TAI is carried out every month andthe results are published monthly in BIPM Circular T.
When preparing the Annual Report, the results shown inCircular T may be revised taking into account any
subsequent improvements made to the data. Results arealso available from the BIPM website (www.bipm.org), as
well as all data used for the calculation. The broad realtime dissemination of UTC through broadcast and satellite
time signals is a responsibility of the national metrology
laboratories and some observatories, following therecommendations of the International Telecommunication
Union (ITU-R).

Conventions and references
Research work is also dedicated to space-time reference
systems. The BIPM provides, in partnership with the US
Naval Observatory, the Conventions Product Centre of theInternational Earth Rotation and Reference Systems
Service (IERS). The last version of the IERS Conventions(2010) has been published in the IERS Technical Note
N°36, also at http://www.iers.org/nn_11216/IERS/EN/
Publications/TechnicalNotes/tn36.html). Regular updates
are published on the internet (last one on 19 June 2015)(http://62.161.69.131/iers/convupdt/convupdt.html). In theframe of the International Astronomical Union (IAU)
activities, and in cooperation with the IERS Centre for theInternational Celestial Reference System, staff of the Time
Department contributes to the elaboration of the third
version of the International Celestial reference Frame(ICRF3).

On the adoption of a continuous referencetime scale (without leap seconds)
The BIPM has actively participated to the work of theInternational Telecommunication Union (ITU) in thediscussions on the adoption of a continuous time scale as
the world reference that involves interrupting the
introduction of leap seconds in UTC. The decision by theWorld Radiocommunication Conference 2015 (WRC-15)
calls for further studies regarding current and potential

International Bureau on Weights and Measures (BIPM)

future reference time-scales, including their impact andapplications. A report will be considered by the WorldRadiocommunication Conference in 2023. Until then, UTC
shall continue to be applied as described in
Recommendation ITU-R TF.460-6 and as maintained by
the BIPM. WRC-15 also calls for reinforcing the links
between ITU and the International Bureau of Weights andMeasures (BIPM). ITU would continue to be responsibleforthedisseminationoftime
signals
via
radiocommunication and BIPM for establishing andmaintaining the second of the International System ofUnits (SI) and its dissemination through the reference timescale.

Activities planned for 2016-2018
x Calculation and dissemination of UTC through themonthly publication of BIPM Circular T; computationand improvement of the rapid UTC; computation ofTT(BIPM)1159

x Improvement of techniques of time and frequency transfer, in particular- Studying some observed effects increasing the noise
in some time transfer techniques (diurnals in
TWSTFT, drift between TWSTFT and GPS links,etc.);- Comparison of optical frequency standards requiring
an accuracy at the level of 10-17 – 10-18;
x Testing novel statistical tools for clock noisecharacterisation in view of their application in theconstruction of the reference time scale;
x Continuing operating in cooperation with the USNO the
IERS Conventions Centre;
x Supporting the organization of the next comparison ofabsolute gravimeters in 2017;
x Continuing the cooperation with the IERS for the establishment of space references;x Liaising with the relevant organizations, such as: IUGG,
IAG and GGOS, IERS, IAU, ITU-R, IGS, and the International Committee for GNSS (ICG).

IAG Scientific Services

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International Earth Rotation and Reference Systems
Service (IERS)
Chair of the Directing Board: Brian Luzum (USA)
Director of the Central Bureau: Daniela Thaller (Germany)https://www.iers.org/

Development

Products

The IERS was established as the International Earth Rotation Service in 1987 by the International Astronomical
Union and the International Union of Geodesy and Geophysics, and it began operation on 1 January 1988. Since
2001, the IERS works in a new organizational structure; in
2003, the new name of the Service, without changing its
abbreviation, was adopted. The IERS is a member of the
ICSU World Data System (WDS).

IERS collects, archives and distributes products to satisfy
the objectives of a wide range of applications, research andexperimentation. These products include the following:
x International Celestial Reference Frame;
x International Terrestrial Reference Frame;x Final daily earth orientation data updated monthly;x Rapid service estimates of near real-time earthorientation data and their predictions updated four times
per day;x Announcements of the differences between astronomical and civil time for time distribution by radio stations;x Leap second announcements;
x Products related to global geophysical fluids such as
mass and angular momentum distribution;
x Annual reports and technical notes on conventions andother topics;
x Long-term earth orientation information.

Objectives
The primary objectives of the IERS are to serve the astronomical, geodetic and geophysical communities by
providing the following:x The International Celestial Reference System (ICRS)
and its realization, the International Celestial Reference
Frame (ICRF);
x The International Terrestrial Reference System (ITRS)
and its realization, the International Terrestrial
Reference Frame (ITRF);
x Earth orientation parameters required to study earthorientation variations and to transform between the
ICRF and the ITRF;
x Geophysical data to interpret time/space variations in
the ICRF, ITRF or earth orientation parameters, andmodel such variations;x Standards, constants and models (i.e., conventions) encouraging international adherence.

The accuracies of these products are sufficient to support
current scientific and technical objectives including thefollowing:
x Fundamental astronomical and geodetic reference
systems;x Monitoring and modeling earth rotation/orientation;
x Monitoring and modeling deformations of the solid
earth;x Monitoring mass variations in the geophysical fluids,
including the atmosphere and the hydrosphere;
x Artificial satellite orbit determination;x Geophysical and atmospheric research, studies of dynamical interactions between geophysical fluids and thesolid earth;x Space navigation.

International Earth Rotation and Reference Systems Service (IERS)

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Structure

IERS Directing Board, as of June 2016

The IERS accomplishes its mission through the following
components:
x Technique Centers: International GNSS Service, International Laser Ranging Service, International VLBI
Service, and International DORIS Service;x Product Centers: Earth Orientation Center, Rapid
Service/Prediction Center, Conventions Center, ICRSCenter, ITRS Center, and Global Geophysical Fluids
Center with Special Bureaus for the Atmosphere, for the
Oceans, for Hydrology, and for Combination;
x ITRS Combination Centers at Deutsches Geodätisches
Forschungsinstitut at TU München (DGFI-TUM),
Institut Géographique National (IGN), Jet Propulsion
Laboratory (JPL);x Analysis Coordinator;
x Central Bureau;x Directing Board;x Working Groups: WG on Site Survey and Co-location,
WG on Combination at the Observation Level, WG on
SINEX Format, WG on Site Coordinate Time Series
Format.
Some of these components (e.g., Technique Centers) may
be autonomous operations, structurally independent from
IERS, but which cooperate with the IERS. A participatingorganization may also function as one or several of thesecomponents.

Zuheir Altamimi (France), ITRS Center Representative
Christian Bizouard (France), Earth Orientation Center
Representative
Jean-Paul Boy (France), GGFC Representative
Aleksander Brzezinski (Poland), IAU Representative
Hugues Capdeville (France), IDS Representative
Ludwig Combrinck (South Africa), ILRS Representative
Rolf Dach (Switzerland), IGS Representative
Bryan Dorland (USA), ICRS Center Representative
Rüdiger Haas (Sweden), IVS Representative
Christine Hackman (USA), Rapid Service/Prediction
Center Representative
Thomas Herring (USA), Analysis Coordinator
Brian Luzum (USA), Chair of the IERS Directing Board
Chopo Ma (USA), IVS Representative
Chuck Meertens (USA), IVS Representative
Axel Nothnagel (Germany), IAG / IUGG Representative
Erricos C. Pavlis (USA), ILRS Representative
Gérard Petit (France), Conventions Center Representative
Bernd Richter (Germany), GGOS Representative
Jérôme Saunier (France), IDS Representative
Daniela Thaller (Germany), Director of the Central
BureauIAG Scientific Services

1162

International DORIS Service (IDS)
Chair of the Governing Board: Pascal Willis (France)
Director of the Central Bureau: Laurent Soudarin (France)
http://ids-doris.org/

Terms of Reference (TOR)
Accepted by the IAG Executive Committee at the XXIIIthIUGG General Assembly, Sapporo, Japan, July 1, 2003.
Revised by the IDS TOR Working Group, and approvedby the IDS Governing Board on, June 23, 2011.
Addenda issued by the IDS Governing Board, approvedby the IAG Executive Committee at the XXVIth IUGG
General Assembly, Prague, Czech Republic, June 26, 2015

Introduction
The DORIS (Doppler Orbit determination and Radiopositioning Integrated on Satellite) system for satellite orbit
determination and precise positioning was developed by
the Centre National d’Etudes Spatiales (CNES) in conjunction
with the Institut Géographique National (IGN) and theGroupe de Recherche de Géodesie Spatiale (GRGS).
A proof of concept for the International DORIS Service(IDS) was conducted through a pilot phase prior to theestablishment of the International DORIS Experiment in1999 by the International Association of Geodesy (IAG).
The IDS formally began on July 1, 2003 after the IAG
official approval at the IUGG General Assembly in
Sapporo. The IDS is an IAG Service and operates in close
cooperation with the International Earth rotation andReference systems Service (IERS).

The IDS Mission
The primary objective of the IDS is to provide a service tosupport geodetic and geophysical research activities
through DORIS data and derived products.

The IDS collects, archives and distributes DORIS
observation data sets of sufficient accuracy to satisfy theobjectives of a wide range of applications andexperimentations. From these data sets the following
products are derived:x Coordinates and velocities of the IDS tracking stations
x Geocenter and scale of the Terrestrial Reference Framex High accuracy ephemerides of the DORIS satellites
x Earth orientation parameters (EOPs)
The accuracies of these products are sufficient to support
current scientific objectives including:x Realization of global accessibility to and theimprovement of the International Terrestrial Reference
Frame (ITRF)
x Monitoring deformations of the solid Earthx Monitoring crustal deformation at tide gauges
x Monitoring variations in the hydrosphere (sea level, icesheets, etc.)x Orbit determination for scientific satellites

The IDS Organization
The IDS accomplishes its mission through the following
components:
x Satellites carrying a DORIS receiverx Network of tracking stations
x Data Centers
x Analysis Centers, Associate Analysis Centers andAnalysis Coordinatorx Combination Centerx Working Groups
x Central Bureau
x Governing Board

International DORIS Service (IDS)

1163

Satellites Carrying a DORIS Receiver

Data Centers

Since July 2003, the CNES and the European Space
Agency (ESA) have provided DORIS data to the IDS. Data
from additional agencies are expected and welcome.
DORIS receivers are flown on LEO satellites for precise
orbit determination as well as for geodetic applications.
Satellites with DORIS receivers are listed on the IDS
website at http://ids-doris.org/.
A representative of the DORIS system serves as avoting member of the Governing Board.

The Data Centers are in direct contact with the CNES,
which provides the DORIS data. The Data Centers archive
the DORIS data, derived products, and ancillary
information required to process these data.
A representative of the Data Centers serves as a voting
member of the Governing Board.

Tab. 1 DORIS data available at IDS Data Centers (June 2016)

Analysis Centers, Associate Analysis Centers andAnalysis Coordinator
The Analysis Centers (ACs) are committed to provide atleast one of the above IDS products on a regular basis.
Expertise in DORIS data analysis and operational
capability are essential factors in the selection of Analysis
Centers. ACs adhere to IDS recommendations for thecreation of high-quality products and their timely archiving
and distribution. Currently, only groups providing IDS
products routinely may be considered as Analysis Centers.

Satellite

Start

End

Type

SPOT-231-MAR-90
04-NOV-92

04-JUL-90
15-JUL-09

Remotesensing

TOPEX/
Poseidon25-SEP-92

01-NOV-94

Remotesensing

SPOT-301-FEB-94

09-NOV-96

Remotesensing

SPOT-401-MAY-98

24-JUN-13

Remotesensing

Tab. 2 List of IDS Analysis Centers and Associate
Analysis Centers (June 2016)

SPOT-511-JUN-02

11-DEC-15

Remotesensing

Analysis Center

Country

Software

Jason-1

15-JAN-02

21-JUN-13

Altimetry

ESA/ESOC

Germany

NAPEOS

13-JUN-02

08-APR-12

Altimetry,
Environment

Geod. Observatory Pecny

Czech Rep.

BerneseNASA/GSFCUSAGEODYN

Jason-2

12-JUL-08–

Altimetry

IGN

FranceGIPSY/OASISCryosat-2

30-MAY-10–

Altimetry

INASAN

RussiaGIPSY/OASIS

HY-2A

1-OCT-11–

Altimetry

CNES/CLSFrance

GINS/DYNAMO

SARAL

14-MAR-13–

Altimetry

Associate Analysis Center

Jason-3

17-JUN-16–

Altimetry

GFZ

Germany

EPOS-OCSENTINEL-3A

16-FEB-16–

Altimetry

ESA/ESOC

Germany

NAPEOS

ENVISAT

Network of Tracking Stations
The IDS network is composed of DORIS permanent
tracking stations located at host institutions and maintainedby the IGN. A list of the sites (past and present) is included
on the IDS website at http://ids-doris.org/.
The network also includes additional DORIS stations
proposed by the IDS to observe during specific campaignsof scientific interest.
A representative of the Network serves as a voting
member of the Governing Board.

The Analysis Coordinator assists the Analysis Centersand monitors their activities to ensure that the IDS
objectives are carried out. The Analysis Coordinator,
working with the Analysis Centers, is expected to provide
quality control, performance evaluation, and continued
development of appropriate analysis standards. The
Analysis Coordinator, with the support of the Combination
Center, is also responsible for the appropriate combinationof the Analysis Centers products into a single set ofprescribed data products.
The Analysis Coordinator and a representative of theAnalysis Centers serve as voting members of theGoverning Board.

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Associate Analysis Centers provide specialized orderived products, not necessarily at regular intervals (suchas precise orbits, station positions, Earth Orientation
Parameters, ionospheric products, tropospheric delays, or
any scientific data products of a missionspecific nature).
They are recognized as such by the Governing Board, uponrecommendation of the Analysis Coordinator. The
Associate Analysis Centers are encouraged to present theirresults at IDS meetings and to submit their final results in
IDS Data Centers for dissemination to researchers andother users. An Associated Analysis Center (AAC) may
become an Analysis Center after demonstrating its
expertise and operational capability during a test period.
Combination Center
The IDS appoints a Combination Center (CC) to combine
individual AC solutions and to generate IDS data products
for submission to the IERS for the formulation of theperiodic update of the ITRF and other geodetic products.
The CC is selected by the Governing Board every four
years through a Call for Participation initiated six months
prior to the end of the current CC term. Interested centerssubmit proposals outlining their plan for operation of the
CC and the resources that they will commit.
A representative of the Combination Center serves as avoting member of the Governing Board.
Working Groups
IDS Working Groups provide expertise on particular topics
related to the IDS components and on development ofparticular IDS product(s) or service(s) relying on the IDS
infrastructure.
All Working Groups are created when needed andretired by the IDS Governing Board when their work has
been completed or they are no longer needed. EachWorking Group must develop a charter that includes a
mandate, a list of specific tasks, a schedule, and an
identified Chairperson.
The Chairpersons of the Working Groups are nonvoting members of the IDS Governing Board (see below).
Central Bureau
The Central Bureau (CB) is the executive arm of the IDS
Governing Board and as such is responsible for the generalmanagement of the IDS consistent with the directives,
policies and priorities set by the Governing Board.
In this role the CB, within available resources,
coordinates IDS activities, facilitates communications,maintains documentation, and organizes reports, meetings,

and workshops. The CB responds to external inquiries
about the IDS, promotes the use of IDS data and products,
and coordinates interactions with other services, including
the IERS.
The CB supports the Combination Center in combining
the various Analysis Centers products and providing all
information necessary to validate the final combined
products.
The CB operates the information system for the IDS andproduces the IDS Annual Reports and IDS Associates
directory. The CB coordinates the publication of otherdocuments required for the satisfactory planning and dayto-day operation of the Service, including standards andspecifications regarding the performance, functionality andconfiguration requirements of all Service elements.
Although the Chairperson of the Governing Board is theofficial representative of the IDS to external organizations,the CB, consistent with the directives established by theGoverning Board, is responsible for the day-to-day liaison
with such organizations.
The long-term function of the IDS is assured throughredundancy and emergency contingency plan for all of its
components except for the CB. The Central Bureau serves
for a term of four years. One year prior to the end of eachterm, the GB formally reviews the performance of theCentral Bureau. At the behest of the GB, the CB may be
asked to reconfirm its commitment to serve another four
years. If the CB agrees, it submits a proposal for GB
approval. If the CB declines or if the GB chooses tochange CB operators, the GB announces a Call for
Proposals for a new IDS Central Bureau to take over
responsibilities including a six-month transition phase withthe outgoing Central Bureau.
In summary, the Central Bureau performs primarily along-term coordination role to ensure that IDS participants
contribute to the Service in a consistent and harmonious
manner and adhere to IDS standards.
The Director of the Central Bureau serves as a voting
member of the Governing Board.
Governing Board
The principal role of the Governing Board (GB) is to set
policy and to exercise broad oversight of all IDS functions
and components. It also controls general activities of theService, including restructuring, when appropriate, tomaintain Service efficiency and reliability.
The Governing Board (GB) consists of eleven voting
members and a number of nonvoting members. The
membership is chosen to try to strike the right balance
between project specialists and the general community.
The voting membership of the GB is distributed as follows:International DORIS Service (IDS)Elected by IDS Associates (see below):
Analysis Centers’ representative:
Data Centers’ representative
Analysis Coordinator:
Members-at-Large:
Appointed members:
Director of the Central Bureau:
IERS representative to IDS:
IAG representative to IDS:
Combination Center representative:
DORIS System representative (CNES):
Network representative (IGN):
Total number of voting members:

1165

1
1
1
2
1
1
1
1
1
1
11

During their mandate, the Working Group chairpersons are
GB members with voice but without vote.
The elected members have staggered four-year terms,
with elections every two years. There is no limit to thenumber of terms that a person may serve, however he or
she may serve only two terms consecutively as an elected
member. The Analysis Center representative, the Data
Center representative, and one Member-at-Large areelected during the first two-year election. The Analysis
Coordinator and the other Member-at-Large are elected in
the second two-year election. Although no formula isprescribed, efforts should be made to keep the GB
membership properly balanced with regard to supportingorganizations and geographic representation.
Members of the GB become IAG Fellows with theappropriate rights and privileges, as described on the IAG
website, after an initial two-year period.
Composition of the IDS Governing Board (June 2016):
x Richard Biancale, CNES, France, Member at Large
x Hughes Capdeville, CLS, France, Analysis Coordinationx Jean-Michel Lemoine, CNES, France, Analysis Coord.
x Pascale Ferrage, CNES, France, System Representativex Brian Luzum, GSFC, USA, IERS Representativex Guilhem Moreaux, CLS, France, Combination Center Repr.
x Carey Noll, GSFC, USA, Data Flow Coordinatorx Michiel Otten, ESOC, Germany, IAG Representativex Jérôme Saunier, IGN, France, Network Representativex Laurent Soudarin, CLS, Director of Central Bureau
x Pascal Willis (Chair) IGN/IPGP, Analysis Center Repr.
x Marek Ziebart, UCL, UK, Member at Large

Five members of the GB are elected by the IDS
Associates. A nominating committee conducts theelections for membership on the IDS Governing Board.
The nominating committee consists of three members. The
Chair of the nominating committee is appointed by the
Chair of the GB, and must be a member of the GB not
currently up for re-election. The GB chooses the remaining
two members of the nominating committee from the list of
IDS Associates.
The nominating committee solicits nominations fromthe IDS Associates for each position to be filled; at least
two candidates are required for each position. The Central
Bureau runs the election. All IDS Associates are eligible tovote. Election is by a simple majority of votes received foreach position. The two Member-at-Large positions arefilled by the two candidates receiving the most votes; avote by the GB will resolve any situation of a tie.
Appointed Members
The IAG and IERS representatives to the IDS Governing
Board are appointed by the IAG Executive Committee andby the IERS Directing Board, respectively, for a maximumof two four-year terms. The DORIS System representative
and the Network representative are appointed by CNES
and IGN, respectively, for four-year terms without
limitation. The Director of the Central Bureau and the
Combination Center representative are the two otherappointed members.
In case of a resignation from the Governing Board, theCB, after consulting with the appropriate IDS components,
nominates a replacement candidate for election by the GB.
The replacement will serve until the end of the term of theresigned Board member.
GB Decisions
Most decisions at GB meetings are to be made by consensus orby a simple majority vote of the voting members present,
provided that there is a quorum consisting of at least six voting
members of the GB. GB decisions can be made through email
or other correspondence by a majority vote of the GB voting
membership. Changes in the IDS Terms of Reference andChairperson of the GB can only be made by a 2/3 majority ofthe members of the GB, i.e., by seven or more votes.

GB Elections
GB Meetings
The GB elects a Chairperson from its members to serve aterm of four years with the possibility of re-election for
one additional term. The Chairperson does not vote on GB
decisions, except in the case of a tie. The Chairperson is
the official representative of the IDS to external organizations.

The Board shall meet at least annually and at such othertimes as shall be considered appropriate by the
Chairperson or at the request of three members. The
Central Bureau provides the secretariat of the GB.

1166

IDS representatives to the IERS and the IAG
Through the existing reciprocity agreement between the
IDS and the IERS, the IDS Analysis Coordinator serves as
the DORIS Technique Center representative to IERS, andas such, subject to Governing Board approval, is a memberof the IERS Directing Board (together with another person
selected by the IDS Governing Board). This arrangement
ensures full cooperation between the two services.
IDS Associates
IDS Associates are persons representing organizations thatparticipate in any of the IDS components. A participating
institution can submit a person s name, email, and primary
IDS function in its organization to the Central Bureau for
application to become an IDS Associate, with a limit often. The Governing Board approves all memberships. The
Governing Board reserves the right to appoint additional
associates who do not participate in any IDS components
but who contribute significantly to the IDS or whose
activities rely on DORIS data and products. Such names
are nominated directly by the IDS GB.
The Central Bureau maintains the current list of IDS
Associates and makes the list available on the IDS website.
IDS Associates vote for the incoming Analysis Centers’representative, the Data Centers’ representative, theAnalysis Coordinator, and the Members-at-Large
representatives as members of the GB.
The GB must approve the list of IDS Associates eligible
for voting in the elections at least three months prior to theelection process. For the purposes of the election, current
and former GB members are also considered IDS Associates.
IDS Associates are considered IAG Affiliates.

IAG Scientific Services

International GNSS Service (IGS)1167

International GNSS Service (IGS)
Chair of the Governing Board: Gary Johnston (Australia)
Director of the Central Bureau: Ruth Neilan (USA)
http://www.igs.org/

Overview
Planning for the years 2016-2019, the International GNSS
Service (IGS) has a number of activities and tasks topursue, both externally and internal to the organization.
The mission of the IGS is to provide the highest-quality
GNSS data and products in support of the terrestrialreference frame, Earth rotation, Earth observation andresearch, positioning, navigation and timing and otherapplications that benefit society.
The IGS is comprised of more than 200 organizations inover 100 countries, and has a fundamental tracking
network of 500 stations. Recent key efforts are theextension of IGS tracking network observations andanalytical capabilities to include new GNSS and signals, aswell as development and expansion of IGS real-time
GNSS capabilities.
These efforts are particularly appropriate to the IGS
Multi-GNSS Experiment (MGEX), which is now a full
IGS Pilot Project, as well as the IGS Real-Time Service(IGS RTS). Much work undertaken by the IGS is basedon its global tracking network, which requires continuous
maintenance and extension, in close cooperation with thecontributing agencies and institutions, to ensure long-term
usability and sustainability.
A key undertaking through 2016 will be thedevelopment of the next IGS Strategic Plan for the period
2017-2020. The IGS Strategic Plans dating back to 2002
are available in the new IGS Knowledge Base (KB):
http://kb.igs.org/
The IGS develops annual strategic implementation plansthat summarize the measurable progress of variousorganizational components within the service. The 2015
IGS Implementation Plan is also available in the IGS
Knowledge Base.

Figure 1 displays the organizational structure of the IGS
and includes the list of Pilot Projects and Working Groups.

Key Activities
The IGS global tracking network, and the quality of the
GNSS data acquired from it, is the basis for the generationof the aforementioned highest-quality products. Highpriority tasks for the near future include fostering the
network and data contributions, monitoring the quality ofstation data, and facilitation of its extension to include
more stations with multi-GNSS observations capability, in
real-time and with generation of products. IGS has planned
for the transition to a GNSS tracking network without
disruption of the existing long-station coordinate timeseries required for the maintenance of the reference frame.
The quality of the IGS products is continuously
monitored and improved. IGS contributes to theInternational Earth Rotation and Reference Systems
Service (IERS) for the International Terrestrial Reference
Frame (ITRF) generation. To accomplish this, IGS
Analysis Centers recompute or reprocess all data frominception, applying new models to the available data, withthe exclusion of stations that have been disturbed by earth
motion, earthquakes, antenna changes, and other factorsthat would deem the observation data not suitable for thereference frame combination determination. IGS GNSS
linkage to many dense regional networks is the key method
for accessing the ITRF globally.
IGS fully supports the IAG Global Geodetic Observing
System (GGOS) and considers its products as GGOS
products. It works with other IAG components towards therealization of GGOS Mission, Vision and Goals, see:
http://www.ggos.org

IAG Scientific Services

1168

Fig. 1 IGS Organization Chart and Association with International Scientific Organizations, 2016

The Multi-GNSS Pilot Project is expanding the IGS
tracking network, currently tracking GPS and GLONASS(Figure 2), to include GNSS observations of the latest
constellations: Galileo (European Union), BeiDou(Compass - China), QZSS (Japan), and Indian Regional

Navigation Satellite System (IRNSS), as well as laying thefoundation for tracking the modernized signals of GPS andGLONASS. Coordinated analysis of the observations andgeneration of reliable products continues to be a challenge
as the IGS strives to incorporate all GNSS.

International GNSS Service (IGS)

IGS operates a real-time network as part of the IGS
Real-Time Pilot Project (Figure 3). Currently data are
available to project participants, and real-time analysis iscoordinated by the European Space Operations Center inDarmstadt (ESA/ESOC), Germany. For more information,
visit the project page: http://igs.org/rts
IGS is an active Associate Member of the United
Nations Office for Outer Space Affairs (UNOOSA)International Committee on GNSS (ICG). One of the
ICG’s four Working Groups, the Working Group on
Reference Frame, Timing and Applications, is co-chairedby IGS, IAG and the International Federation of Surveyors(FIG). IGS was recently also named co-chair of a new
Task Force, formerly an ICG sub-committee on GNSS
Monitoring and Assessment. The Task Force is co-chairedby representatives of China and Japan, as well as the IGS.
This is recognition that IGS, due to multi-GNSS
observations and analysis, may potentially be able to takeon a greater service role for system providers by providing
independent monitoring of the available GNSS
constellations.
A challenge for the IGS in both the IGS MGEX and
Real-Time Pilot Project is data format issues. The IGS has
formalized its efforts towards standardization of multiGNSS batch and real-time observation and product formats
and protocols through cooperation with the RadioTechnical Commission for Maritime Services (RTCM).
RTCM Special Committees are chartered to address indepth radio-communication and radio-navigation areas ofconcern to the RTCM membership. The output documents
and reports prepared by these committees are usually
published as RTCM Recommended Standards and include
standards for GNSS.
The IGS is a member of the International Council for
Science (ICSU) World Data System (WDS). This is aninterdisciplinary body of ICSU, an integration of theformer Federation of Astronomical and Geophysical Data
Analysis Services (FAGS) and World Data Center System.
See: http://www.icsu-wds.org/
IGS continues to support other IAG elements, withfocus on lesser economically developed countries (LEDC).
Since 2001, IGS has been actively supporting efforts
within Africa to realize the Unification of African
Reference Frames – AFREF. This is progressing well, but
continued engagement between Africa and elements within
IAG is needed.

1169

Internally, the IGS Central Bureau (CB) is still in theprocess of a complete redesign and implementation of the
IGS website. A top goal of the design is to have a state-ofthe-art website that has shared administration with otherprincipal people within the IGS. A ‘Site Log Manager(SLM)’ was jointly developed with the University
NAVSTAR Consortium (UNAVCO), and enables station
operators to manage and update their own information. The
information within the website and the SLM will haveautomatic validation procedures built in, for efficientmanagement the over 500 stations and networks within the
IGS. The website tools and processes can be extended toother scientific services within the IAG and to GGOS.
Social networking options for the IGS are implemented,
including Twitter, Facebook, Google+, Instagram,
LinkedIn, and YouTube, see: http://igs.org/social
The IGS 2014 Workshop was held in Pasadena,
California, USA, in celebration of the 20th anniversary of
the founding of the IGS. The workshop was and washosted by the Central Bureau, and sponsored by Caltech
and the NASA Jet Propulsion Laboratory.
Geoscience Australia and University of New South
Wales hosted the IGS 2016 Workshop in Sydney,
Australia. The workshop was well attended, by over 180
people from around the world.
See http://igs.org for IGS meetings, videos andpresentations, and posters. We know that many people
cannot attend workshops, and use the website to provide
access to IGS workshop resources for all members of thecommunity.

Summary
The IGS remains a vital organization that continues to
evolve with challenging opportunities. The IGS is
preparing for a future with new additional GNSS signals
and new constellations, with the goal of generating
highest-quality products for all available GNSS -- for the
benefit of science and society. Global resources, both
funding, human intellect, information technology andanalysis continue to be required in order to ensure thelong-term success and sustainability of this service.

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International Laser Ranging Service (ILRS)
Chairman of the Governing Board: Giuseppe Bianco (Italy)
Director of the Central Bureau: Michael Pearlman (USA)Secretary of the Central Bureau: Carey Noll (USA)
Analysis Coordinator: Erricos C. Pavlis (USA)
http://ilrs.gsfc.nasa.gov/

In this document we have incorporated the IAG standards
for the use of “Committee” to replace “Working Group”
for those entities that lie within the Services.

Development
Satellite Laser Ranging (SLR) was established in the mid1960s, with early ground system developments by NASA,
SAO, and CNES. Early US and French satellites provided
laser targets that were used mainly for inter-comparison
with other tracking systems, refinement of orbit
determination techniques, and as input to the developmentof ground station fiducial networks and global gravity fieldmodels. Early SLR brought the results of orbit
determination and station positions to the meter level ofaccuracy. The SLR network was expanded in the 1970s
and 1980s as other groups built and deployed systems, andtechnological improvements began the evolution toward
the decimeter and centimeter accuracy. Since 1976, themain geodetic target has been LAGEOS (subsequently
joined by LAGEOS-2 in 1992), providing the backbone of
the SLR technique’s contribution to the realization of theInternational Terrestrial Reference Frame (ITRF). Lunar
tracking activity began in 1969 after the deployment of thefirst retro-reflector array on the surface of the Moon by the
Apollo 11 astronauts.
Tracking campaigns were initially organized through
COSPAR and through the Satellite and Lunar Laser
Ranging (SLR/LLR) Sub-commission on the Coordinationof Space Techniques for Geodesy and Geodynamics(CSTG). With strong encouragement from the President of
the CSTG, the Sub-commission Steering Committee
undertook the formation of the International Laser Ranging
Service, ILRS in April 1998, following a similar initiativethat had brought the GPS community together under theInternational GPS (now GNSS) Service, IGS, in 1993. The
ILRS is one of the space geodetic services of theInternational Association of Geodesy (IAG) and is amember of the IAG’s Global Geodetic Observing System(GGOS).
The ILRS is a major component of GGOS, providing
observations that contribute to the determination of thethree fundamental geodetic observables and theirvariations, that is, Earth's shape, Earth's gravity field andEarth's rotational motion. The ILRS continues as one of thefundamental inputs to the ITRF. Currently, 35 stations in
the ILRS network track 60 – 70 satellites in LEO, MEO,
GNSS, and synchronous orbits. Some stations in the ILRS
network support lunar ranging and ranging to the Lunar
Orbiter, with plans to extend ranging to interplanetary
missions with optical transponders.
On the current path toward mm accuracy SLR and LLRpractitioners are now building new systems and upgrading
old ones to improve ground system performance using
higher pulse repetition rates (0.1 – 2 KHz) for faster dataacquisition; smaller, faster slewing telescopes for more
rapid target acquisition and pass interleaving; capabilities
to ranging from Low Earth Orbiting (LEO) satellites to the
Earth navigation satellites; more accurate pointing for
greater link efficiency; narrower laser pulse widths for
greater precision; new detection systems for greater
ranging accuracy; greater temporal, spatial, and spectral
filtering for improved signal to noise conditions; more
automation for operational economy (24/7) and greater
temporal coverage; and modular construction and more
off-the-shelf components for lower fabrication/operations/maintenance cost.

International Laser Ranging Service (ILRS)

MissionThe ILRS collects, merges, analyzes, archives anddistributes Satellite Laser Ranging (SLR) and Lunar Laser
Ranging (LLR) observation data sets of sufficient accuracy
to satisfy the GGOS objectives of a wide range ofscientific, engineering, and operational applications andexperimentation. The basic observable is the precise timeof-flight of an ultra-short laser pulse to and from a
retroreflector-equipped satellite. These data sets are usedby the ILRS to generate a number of fundamental added
value products, including but not limited to:x Centimeter accuracy satellite ephemerides;
x Earth orientation parameters (polar motion and length ofday);
x Three-dimensional coordinates and velocities of the
ILRS tracking stations;x Time-varying geocenter coordinates;
x Static and time-varying coefficients of Earth's gravity
field;x Fundamental physical constants;
x Lunar ephemerides and librations;x Lunar orientation parameters.

Structure
The ILRS structure includes the following permanent
components:
x Tracking Station Networks and Sub-networks;
x Operations Centers;x Global and Regional Data Centers;x Analysis, Lunar Analysis, and Associate Analysis
Centers;x Central Bureau;x Governing Board and specialized Committees(Analysis; Missions; Networks and Engineering; Data
Formats and Procedures; and Transponders).
Information on these permanent components can be foundin the ILRS website (http://ilrs.gsfc.nasa.gov/). From time
to time, the ILRS also establishes temporary Study Groups
to address timely topics.

Governing Board (2015)
x Michael Pearlman, Ex-officio, Director Central Bureau
x Carey Noll, Ex-officio, Secretary Central Bureau
x Geoff Blewitt, Ex-officio, President IAG Commission 1
x Daniela Thaller, Appointed, IERS representative to
ILRS

1171

x Giuseppe Bianco, Appointed, EUROLAS Network Rep.
x Georg Kirchner, Appointed, EUROLAS Network Rep.
x Wu Bin, Appointed, WPLTN Network Representativex Toshi Otsubo, Appointed, WPLTN Network Rep.
x David McCormick, Appointed, NASA Network Rep.
x Jan McGarry, Appointed, NASA Network Rep.
x Vincenza Luceri, Elected, Analysis Center Rep.
x Erricos C. Pavlis, Elected, Analysis Center Rep.
x Horst Müller, Elected, Data Center Representativex Jürgen Müller, Elected, LLR Representativex Matt Wilkinson, Elected, At Large Representativex Ulrich Schreiber, Elected, At Large Representative,
Chair of the Governing Board
Past Governing Board Chairsx John Degnan
x Werner Gurtner (deceased)x Graham Appleby

Products
The most important aspects of the SLR and LLR
observations are absolute accuracy and long, stable time
histories at a number of sites. Accuracy approaches thelevel of a few mm for modern stations; time histories canbe 30 years or more on some satellites, and more than 45
years on the Moon. Since the inception of the service, theILRS has put the generation of official analysis products
high on its agenda. Official submissions to the IERS
include weekly solutions for station coordinates and Earth
Orientation Parameters (EOPs) submitted on a dailyfrequency. Additionally, some of the ILRS Analysis
Centers (ACs) submit estimates of GM and time-varying
geocenter motion to the IERS Global Geophysical Fluids
Center. Other user products include static and time-varying
coefficients of Earth's gravity field, accurate satellite
ephemerides for POD and validation of altimetry,
relativity, and satellite dynamics, backup POD for othermissions, and Lunar ephemeris for relativity studies andlunar libration for lunar interior studies.
The products of the Analysis, Lunar Analysis, andAssociate Analysis Centers are made available to thescientific community through the two Global Data Centers:x Crustal Dynamics Data Information System (CDDIS) at
NASA’s Goddard Space Flight Center, Greenbelt, MD,USA,
x European Data Center (EDC), at DGFI - TUM, Munich,Germany

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The high accuracy of SLR/LLR data products support
many scientific, engineering, and operational applications
including:x Realization and maintenance of the International
Terrestrial Reference Frame (ITRF)
x Access to Earth’s center of mass relative to the global
network and its time variations
x Monitoring three-dimensional deformations of the solid
Earthx Monitoring Earth rotation variations and polar motion
x Monitoring the long wavelength static and dynamic
components of Earth's gravity field.
x Supporting, via precise ranging to altimeter satellites,
the monitoring of variations in the topography of theliquid and solid Earth (ocean circulation, mean sea
level, ice sheet thickness, wave heights, vegetation
canopies, etc.)
x Calibration and validation of microwave tracking
techniques (e.g., GPS, GLONASS, Galileo, BeiDou,and DORIS)
x Picosecond global time transfer experiments
x Determination of non-conservative forces acting on
satellites
x Astrodynamical observations including determination of
the dynamic equinox, obliquity of the ecliptic, and theprecession constantx Gravitational and general relativistic tests, including
Einstein's Frame-dragging, Equivalence Principle, theRobertson-Walker b parameter, and time rate of changeof the gravitational constant, G
x Lunar physics including the dissipation of rotationalenergy, shape of the core-mantle boundary (Love Numberk2), and free librations and stimulating mechanisms
x Solar System ties to the International Celestial
Reference Frame (ICRF)

Contacts
x Michael Pearlman, Director, ILRS Central Bureau:
mpearlman@cfa.harvard.edu
x Carey Noll, Secretary, ILRS Central Bureau:
Carey.Noll@nasa.gov
x Giuseppe Bianco, Chair, ILRS Governing Board:giuseppe.bianco@asi.it
x Erricos
C.
Pavlis,Analysis
Coordinator:
epavlis@umbc.edu

Publications
The ILRS Central Bureau maintains a comprehensive
website as the primary vehicle for the distribution of
information within the ILRS community. This site can beaccessed at http://ilrs.gsfc.nasa.gov. Many ILRS andrelated publications and reports can now be accessed
online through the ILRS website including:x ILRS Terms of Reference and Working Group Charters
x ILRS Network Description and Status
x ILRS Satellite Descriptions and Tracking Information
x ILRS Service Reports (first volume published covers
year 1999)
x ILRS Meeting Reports and Presentations (Governing
Board, General Assembly, Working Group)
x ILRS Associates Directoryx ILRS Organizations and Technical Contacts
x Science and Engineering References and Reports

International VLBI Service for Geodesy and Astrometry (IVS)

1173

International VLBI Service for Geodesy andAstrometry (IVS)
Chair of Directing Board: Axel Nothnagel (Germany)
Coordinating Center Director: Dirk Behrend (USA)
http://ivscc.gsfc.nasa.gov

Development
The International VLBI Service for Geodesy and Astrometry (IVS) is an international collaboration of organizations, which operate or support Very Long Baseline Interferometry (VLBI) components. IVS was established in
1999 and became a service of IAG that year. In 2000, IVS
was recognized as a service of the International
Astronomical Union (IAU). In 2013 an agreement was
signed between the IVS and the International Council for
Science (ICSU) accepting the service as a Network
Member of ICSU’s World Data System (WDS). The IVS
interacts closely with the International Earth Rotation andReference Systems Service (IERS), which is tasked by
IAU and IUGG with maintaining the international celestial
and terrestrial reference frames (ICRF and ITRF).

Mission/Objectives
The objectives of IVS are:x To provide a service to support geodetic, geophysical,
and astrometric research and operational activities.
x To promote research and development activities in all
aspects of the geodetic and astrometric VLBI
technique.
x To interact with the community of users of VLBI
products and to integrate VLBI into a global Earthobserving system.
To meet these objectives, IVS coordinates VLBI observing
programs, sets performance standards for VLBI stations,establishes conventions for VLBI data formats and data
products, issues recommendations for VLBI data analysis

software, sets standards for VLBI analysis documentation,and institutes appropriate VLBI product delivery methods
to ensure suitable product quality and timeliness. IVS
closely coordinates its activities with the astronomicalcommunity because of the dual use of many VLBI
facilities and technologies for both astronomy and astrometry/ geodesy.

Products
VLBI data products currently available are
x
x
x
x
x

All components of Earth orientation
Terrestrial reference frame
Celestial reference frame
Tropospheric parameters
Baseline lengths

All VLBI data products are archived in IVS Data Centers
and are publicly available.

Structure / Board / Members
IVS accomplishes its goals through Permanent Components. As of 2016 the IVS has:x 32 Network Stations, acquiring high performance VLBI
data.
x 3 Operation Centers, coordinating activities of Network
Stations.
x 7 Correlators, processing acquired data, providing feedback to stations and providing processed data to analysts.
x 5 Data Centers, distributing products to users,
providing storage and archiving functions.

IAG Scientific Services

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x 28 Analysis Centers, analyzing the data and producing
results and products.
x 7 Technology Development Centers, developing new
VLBI technology.
x 1 Coordinating Center, coordinating daily and longterm activities of IVS.
All together there are 83 Permanent Components, representing 43 organizations in 21 countries, and ~300 individuals who are Associate Members. The 43 organizations
that support IVS components are IVS Member Organizations. There are also 6 Affiliated Organizations that cooperate with IVS on issues of common interest but do notsupport an IVS component.
In addition the IVS has a Directing Board to determine
policies, standards, and goals. The current IVS Directing
Board consists of the following members (alphabetical):
1. D. Behrend (USA) Coordinating Center Director
2. A. Bertarini (Germany) Correlators and Operation
Centers Representative
3. P. Charlot (France) IAU Representative
4. L. Combrinck (South Africa) IAG Representative
5. J. Gipson (USA) Analysis Coordinator
6. R. Haas (Sweden) Technology Development Centers
Representative
7. E. Himwich (USA) Network Coordinator
8. A. Ipatov (Russia) At Large member
9. R. Kawabata (Japan) At Large member
10. J. Lovell (Australia) Network Stations Representative
11. Ch. Ma (USA) IERS representative
12. A. Niell (Australia) Analysis and Data Centers
Representative
13. A. Nothnagel (Germany) Analysis and Data Centers
Representative
14. B. Petrachenko (Canada) Technology Coordinator
15. T. Schüler (Germany) Network Stations Representative
16. G. Wang (China) Member-at-Large

Committees and Working Groups
IVS currently has two active working groups, three committees, and one executive group:
x
x
x
x
x
x

Working Group 7 on Satellite Observations with VLBI.
Working Group 8 on Galactic Aberration.
Observing Program Committee (OPC).
Committee on Training and Education (CTE).
VGOS Technical Committee (VTC).
VGOS Project Executive Group (VPEG).

Publications and Meetings
IVS publishes a Biennial Report, a thrice-annual Newsletter, and Proceedings from its biennial General Meeting.
All publications are available from the Coordinating
Center and also published on the Web site. IVS holds a
General Meeting every two years, a Technical Operations
Workshop every two years, and an Analysis Workshop
every year. Information about all IVS activities is available
at the IVS Web site under the URL http://ivscc.gsfc.nasa.gov.

International Gravity Field Service (IGFS)

1175

International Gravity Field Service (IGFS)
Chair: Riccardo Barzaghi (Italy)
Director of Central Bureau: Georgios Vergos (Greece)
http://igfs.topo.auth.gr/

Objectives
IGFS is a unified "umbrella" IAG service, which will:x Coordinate collection, validation, archiving anddissemination of gravity field related data;x Coordinate courses, information materials and generalpublic outreach relating to the Earth’s gravity field;
x Unify gravity products for the needs of GGOS – theGlobal Geodetic Observing System.
The IGFS coordinates the following IAG services:x BGI (Bureau Gravimetrique International), Toulouse,
France ;x ISG (International Service for the Geoid), Politecnico di
Milano, Milano, Italy;
x IGETS (International Geodynamics and Earth Tides
Service), EOST, Strasbourg, France;x ICGEM (International Center for Global Earth Models),
GFZ, Potsdam, Germany;x IDEMS (International Digital Elevation Model Service),
ESRI, Redlands, CA, USA.
The overall goal of IGFS is to coordinate the servicing of
the geodetic and geophysical community with gravity field
related data, software and information. The combined dataof the IGFS entities will include global geopotential models,terrestrial, airborne, satellite and marine gravity observations,
Earth tide data, GPS/leveling data, digital models of terrain
and bathymetry, as well as ocean gravity field and geoidfrom satellite altimetry. Both the static and the temporalvariations of the gravity field will be covered by the IGFS.
IGFS will – in cooperation with the Services - make aspecial effort in trying to secure release of data fromnational and international institutions holding data on thespatial and temporal gravity variations, geoid and thesurface heights of the Earth, to make them widely available
to the scientific community.
IGFS will coordinate regional conferences, tutorials andschools to train young scientists and members of national
institutions in the various aspects of the gravity field
science, computations, and data collection. IGFS will
maintain a publication activity related to the gravity field,
especially through “Newton’s Bulletin”.

Structure
The Service is organized by means of the following structure:x Advisory Board;x Central Bureau;x Technical Centers;x Services.
The Advisory Board is composed of:x Directors (or their delegates) of each of theServices/Centers of IGFS;
x Chairs of the IGFS working groups;
x Presidents (or their delegates) of the IAG Commissions
related to the Service work;x A representative of the IAG Executive Committee(IAG-EC);x Two members appointed among the affiliates.
The Advisory Board:x Coordinates the scientific strategy;x Coordinates the joint activity of the Centers;x Oversees the participation of the Service in international
projects;
x Presents to the IAG-EC proposals for associating newcenters;x Elects the IGFS affiliates upon nomination by theServices/Centers or affiliates.

IAG Scientific Services

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The Advisory Board is appointed for four years between
IUGG General Assemblies. The existing Advisory Board
selects new members as required and nominates the Chairof the IGFS. The election is to be confirmed by the IAGEC. The Advisory Board makes decisions by majority
vote; it can also vote by email. The Advisory Board
decides the Terms of Reference for IGFS.

IGFS Services and Centers
The IGFS Services and Centers are the “operating arms” of
IGFS. They are committed to produce services andproducts related to the gravity field of the Earth and/or theplanets and are approved by the IAG-EC. Services andCenters can include bodies of structures external to the
IAG (e.g., the BGI which is reporting to FAGS). They will
have their own governing bodies, nominated according tointernal rules, also taking into account the interests of the
supporting entities. In particular, each governing body will
have a Director, elected according to internal rules.
Services and Centers will maintain a list of data andproducts, providing them to the general public according totheir policy of dissemination. They will deliver services in
the form of data archiving, data analysis anddissemination, software, training on gravity field
estimation, support to field campaigns etc. The activities ofeach Service/Center will be reviewed annually by the IAGEC. The IGFS Technical Centre, located at the National
Geospatial-Intelligence Agency, USA, will play a specialrole in advice on global models, geoid and gravity,
especially related to the global ultra-high resolution
geopotential models.

IGFS Central Bureau
The IGFS Central Bureau will act as the central
coordination and communication center of the IGFS. The
Central Bureau will provide: a link between the IGFS
entities, IAG, and external projects, networks ororganizations (oceanic, atmospheric, hydrologic…); a linkto the GGOS Bureaus in order to communicate theirrequirements and recommendations to the IGFS Services.
It will also implement standards and recommendations
related to gravity field observations, secure consistency
with geometric standards and promote their use within thegeoscience community. Furthermore, the Central Bureau
will maintain the IGFS website and arrange gravity field
related meetings and workshops.

Joint Study Groups
JSG 3.1: Intercomparison of Gravity and Height Changes(joint with Commissions 1, 2 and 3, description
see Commission 3)

Joint Working groups
JWG 0.1.2: Strategy for the Realization of the International
Height Reference System (IHRS)(joint with GGOS, Commission 1, ICCT,
description see GGOS)
Chair: Laura Sánchez (Germany)JWG 2.1.1: Establishment of a global absolute gravity
reference system (joint with Commission 2,
description see Commission 2 and IGETS)
Chair: Hartmut Wziontek (Germany)JWG 2.2.1: Integration and validation of local geoid
estimates (joint with Commission 2, ISG,
description see Commission 2)
Chair: Mirko Reguzzoni (Italy)

IGFS Advisory Board
S. C. Kenyon (USA)J.-P. Barriot (French Polynesia)
S. Bonvalot (France)
F. Barthelmes (Germany)
U. Marti (Switzerland)
R. Pail (Germany)
S. Bettadpur (USA)H. Denker (Germany)
Y. Wang (USA)L. Sanchez (Germany)
L. Vitushkin (Russia)
M. G. Sideris (Canada)
J. Huang (Canada)
A. Eicker (Germany)
R. Forsberg (Denmark)T. Gruber (Germany)
M. Reguzzoni (Italy)
N. Tziavos (Greece)
K. Kelly (USA)
H. Abd-Elmotaal (Egypt)
Y. Fukuda (Japan)

International Centre for Global Earth Models (ICGEM)

1177

International Centre for Global EarthModels (ICGEM)
Director: Franz Barthelmes (Germany)
http://icgem.gfz-potsdam.deTerms of Reference
The determination of the Earth’s global gravity field is oneof the main tasks of Geodesy: it serves as a reference forgeodesy itself, and it provides important information about
the Earth, its interior and its fluid envelope for all
geosciences. Thus, it is important to make the models of
the global gravity field available to the public as productsof geodesy. This becomes increasingly important as time
variations of the global gravity field can be measured with
better and better spatial and temporal resolution.
The calculation of the different functionals of thegeopotential (e.g.: geoid, gravity anomaly, gravity
disturbance, equivalent water height) from a defined global
model, on a specified grid and with respect to a definedreference system, is far from being trivial and a
responsibility of geodesy too.
Additionally, it is important to make the spatial
structure and temporal variability of the global gravity
field available to the general public in a graphic vivid
manner. In particular for temporal gravity models, aspectsof consistency in processing, reference frame, andparameterization are becoming more and more important.

Overview

x making them available on the web in a standardized
format (self-explanatory);x the possibility to provide Digital Object Identifiers(DOI) to the models, i.e. to the dataset of coefficients;
x the interactive visualization of the models (geoid
undulations and gravity anomalies);x the visualization of monthly GRACE models;x a web-interface to calculate gravity functionals from thespherical harmonic models on freely selectable grids(filtering included);x a web-interface to calculate and plot the time variationof the gravity field at freely selectable positions or overdefined basins Æ the G3-Browser (GFZ Grace Gravity
Browser);x the theory and formulas of the calculation service in
STR09/02 (downloadable);x the ICGEM web-based discussion forum;x the comparison of the models in the spectral domain;x the comparison of the models with GNSS / levellingderived geoid values;
x the visualization of surface spherical harmonics astutorial.

Services
The Models

The International Centre for Global Earth Models has been
established in 2003 as a new service under the umbrella ofthe new International Gravity Field Service (IGFS) as oneof six centers. It is mainly a web based service andcomprehends:
x collecting and long-term archiving of existing global
gravity field models; solutions from dedicated time
periods (e.g. monthly GRACE models) are included;

Currently, 153 models are listed with their references and,apart from 17 older models, all are available in form ofspherical harmonic coefficients. Models from dedicatedtime periods (e.g. monthly solutions from GRACE) of
CSR, JPL, CNES/GRGS and GFZ are also available. Since
2016 the models can be provided by Digital Object
Identifiers (DOI).

IAG Scientific Services

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Digital Object Identifiers (DOI)
Since 2016, ICGEM together with the Library of the“Wissenschaftspark Albert Einstein“ (Telegrafenberg,
Potsdam), provides the ability to assign Digital Object
Identifiers (DOI) to the models, i.e. to the datasets of thecoefficients.
The Format
The spherical harmonic coefficients are available in astandardized self-explanatory format which has been
accepted by ESA as the official format for the GOCE
project.
The Visualization
An online interactive visualization of the models (heightanomalies and gravity anomalies) as illuminated projection
on a freely rotatable sphere is available (see Fig. 1).
Differences of two models, arbitrary degree windows,
zooming in and out, are possible. Additionally, ananimation over time of the monthly solutions fromGRACE is also included. The visualization of single
spherical harmonics is possible for tutorial purposes.

Fig. 2 Snapshot of the G3-Browser; selected is a point
affected by the Sumatra earthquake of 2004; the time series
is computed from the GRGS monthly solutions

The G3-Browser (GFZ Grace Gravity Browser)
To calculate and visualize the time variation of the gravity
field at any desired point on the Earth or as mean overpredefined basins, a specific web-interface has beendeveloped. The results can be downloaded as plots or
ASCII data. Figures 2 and 3 show two examples.
Fig. 3 Snapshot of the G3-Browser; the plot shows the timeseries of the anisotropically filtered (DDK5) monthly
solutions from GFZ, JPL and CSR at a point affected by
the ice loss in Greenland
The Calculation Service

Fig. 1 Visualization (geoid) of a global gravity field model

A web-interface to calculate gravity field functionals fromthe spherical harmonic models on freely selectable grids,
with respect to a reference system of the user’s choice, isprovided (see Figs. 4 and 5). The following functionals areavailable:
x pseudo height anomaly on the ellipsoid (or at arbitraryheight over the ellipsoid)x height anomaly (on the Earth’s surface as defined)
x geoid height (height anomaly plus spherical shell
approximation of the topography)
x gravity disturbanceInternational Centre for Global Earth Models (ICGEM)

1179

x gravity disturbance in spherical approximation (atarbitrary height over the ellipsoid)
x gravity anomaly (classical and modern definition)
x gravity anomaly (in spherical approximation, atarbitrary height over the ellipsoid)x simple Bouguer gravity anomaly
x gravity on the Earth’s surface (including the centrifugal
acceleration)
x gravity on the ellipsoid (or at arbitrary height over theellipsoid, including the centrifugal acceleration)
x gravitation on the ellipsoid (or at arbitrary height overthe ellipsoid, without centrifugal acceleration)
x second derivative in spherical radius direction (atarbitrary height over the ellipsoid)x equivalent water height (water column)
Filtering is possible by selecting the range of usedcoefficients or the filter length of a Gaussian averaging
filter. The calculated grids (self-explanatory format) andcorresponding plots (Postscript or Portable Network
Graphics) are available for download after some seconds.

Fig. 6 Table (truncated) of comparison of the models with
GPS-levelling: Root mean square (rms) about mean of
GPS / levelling minus gravity field model derived geoid
heights [m]Fig. 4 Input mask of the calculation service

Fig. 5 Example of grid and plot generation by thecalculation service: gravity disturbances of the Chicxulub
crater region from the model EGM2008

Fig. 7 Comparison of the models in the spectral domain(e.g.: GO_CONS_GCF_2_SPW_R4) with one of the mostrecent combination models (e.g. EIGEN-6C4)

IAG Scientific Services

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Data Policy
Access to global gravity field models, derived products andtutorials, once offered by the center, shall be unrestricted
for any external user.

Staff
ICGEM is hosted by GFZ Potsdam. Its staff consists ofx Franz Barthelmes
x Wolfgang Köhler
Point of Contact
Franz Barthelmes
Helmholtz Centre Potsdam
GFZ German Research Centre for Geosciences
Telegrafenberg
D-14473 Potsdam
Germany
E-mail: bar@gfz-potsdam.deFig. 8 Visualization of the improvement of satellite-onlymodels over the past decades: Geoiddifferences to themodel EIGEN-6C4 as a function of spatial resolution

Fig. 9 Visualization of the “Geoid” of the Moon

International Digital Elevation Model Service (IDEMS)

1181

International Digital Elevation Model Service (IDEMS)
Director: Kevin M. Kelly (USA)https://idems.maps.arcgis.com/home/

Introduction
The International Digital Elevation Model Service(IDEMS) is one of five centres of the International Gravity
Field Service (IGFS) of the International Association of
Geodesy (IAG). IDEMS provides a focus for distributionof data and information about digital elevation models,spherical-harmonic models of Earth’s global topography,
lunar and planetary DEM, relevant software and related
datasets (including representation of Inland Water within
Digital Elevation Models) which are available in the publicdomain.

Products
IDEMS will provide the following DEM related products:
x Compilation, tutorial-style provision and maintenanceof information on global gridded DEMs;
x Compilation of available national elevation data setswith information on data resolution, methods used for
DEM generation and links to providers;x Generation and dissemination of spherical-harmonicmodels of Earth’s global topography and bathymetry;x Compilation of geodesy-relevant DEM-studies;x Extension of the focus from Earth to Moon andterrestrial planets through compilation of information on
available planetary topography models.

Structure
IDEMS will be hosted and operated by Environmental
Systems Research Institute (Esri) (http://www.esri.com/)under the lead of Kevin M Kelly (director) and Jianbin
Duan (deputy director). Esri currently hosts two dynamic
world elevation image services: Terrain (http://www. arc
gis.com/home/item.html?id=58a541efc59545e6b7137f961
d7de883) and TopoBathy (http://www. arcgis.com/home/item.html?id=c753e5bfadb54d46b69c3e68922483bc).
These services provide online access to a global
collection of multi-resolution and multi-source elevation
data, including comprehensive metadata and source
information for its global data holdings. This collection
includes the best publicly available data and community
contributed data with resolutions ranging from 1000 meters
to 3 meters. The services provide a single endpoint fordesktop and web applications to access elevation values
and derived products. Access to IDEMS will not require
Esri software. However, for users with Esri software –which includes many academic institutions globally – anumber of pre-defined, common terrain data analysis tools
become available such as data aggregation, interpolation,
density, buffering, flow analysis, and more.
Although currently in development, operation of IDEMS
by Esri will comprise:x Set up of a dedicated website to compile anddisseminate all relevant information, data and software.
x Maintenance of the website including regular updates
and inclusion of new material as it becomes available.
x Active encouragement of users to contribute theirexperiences, studies, and information on the multitudeof global, regional and national data sets to the website.
x Close liaison of the IDEMS team members with the
producers of DEM data to obtain up-to-date information
on improved releases or clarification of processing
details.

1182

Governing Board
The Governing Board (GB) consists of five members andwill oversee the operation and general activities of theservice. Members of the GB will be appointed by the IAG
Executive committee for a maximum term of four years.
The GB is structured as follows:
Director of IDEMS:
Kevin M Kelly, USA
Deputy Director of IDEMS:
Jianbin Duan, USA
IAG/IGFS representative:
Riccardo Barzaghi, Italy
Advisory member:
Christian Hirt, Australia
Advisory member:Michael Kuhn, Australia

IAG Scientific Services

International Geodynamics and Earth Tide Service (IGETS)

1183

International Geodynamics and Earth Tide Service (IGETS)
Chair: Hartmut Wziontek (Germany)
Director of the Central Bureau: Jean-Paul Boy (France)
http://igets.u-strasbg.fr/

1. Terms of Reference
1.1 Objectives
The primary objective of the International Geodynamics
and Earth Tide Service (IGETS) is to provide a Service tomonitor temporal variations of the Earth gravity field
through long-term records from ground gravimeters,
tiltmeters, strainmeters and other geodynamic sensors.
IGETS continues the activities of the Global Geodynamic
Project (GGP) to provide support to geodetic and geophysicalresearch activities using superconducting gravimeter (SG)data within the context of an international network. IGETS
continues the activities of the International Center for Earth
Tides (ICET), in particular, in collecting, archiving anddistributing Earth tide records from long series of gravimeters,
tiltmeters, strainmeters and other geodynamic sensors.

IGETS strives to provide longǦterm gravity residuals
based on repeated absolute gravity measurements atparticular stations accessible through the Absolute Gravity
database.
IGETS also acts as the main data center of long-termseries recorded from other geodynamic sensors (spring
gravimeters, tiltmeters, strainmeters, etc.), including thehistorical dataset from the ICET databank.
IGETS may conduct comparison, validation anddistribution of tidal analysis software or any othersoftware, which can be used to process or correct gravity,
tilt or strain long time series.
IGETS may organize symposia and workshops toprovide a forum for presentation and discussion of all
aspects of IGETS activities.

2. Permanent Components

1.2 Products and Goals
IGETS is the main data center of worldwide high precision
SG records; the products hosted at the IGETS data centers are:x Raw gravity and local pressure records sampled at 1 or
2 seconds, in addition to the same records decimated at
1-minute samples (Level 1 products);
x Gravity and pressure data corrected for instrumental
perturbations, ready for tidal analysis. This product isderived from the previous datasets, and is computed by
one or several Analysis Centers (Level 2 products).
x Gravity residuals after particular geophysicalcorrections (including solid Earth tides, polar motion,
tidal and non-tidal loading effects). This product is also
derived from the previous dataset and is computed by
one or several Analysis Centers (Level 3 products).

IGETS accomplishes its objectives through the following
permanent components:
x Stations
x Analysis Centersx Data Centers
2.1 Stations
The IGETS network consists of high quality and stability
measurements of gravity, tilts and strain, including
superconducting gravimeters. Stations should comply withthe performance standards for data quality and reliability,
developed since 1997 during the Global Geodynamics
Project (GGP), specified by the Directing Board.

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2.2 Analysis Centers
The Analysis Centers are committed to produce data
products accordingly to the recommendations andspecifications defined by IGETS Directing Board, andsend their final products to the main Data Center for
dissemination to researchers and other users. They may
produce any of the IGETS products, or any of thecorrections needed to compute them.
The primary Analysis Center is responsible forcomputing SG corrected data (the Level 2 products). The
final SG residuals (the Level 3 products) are computed by
the secondary Analysis Center. The institutions currently
in charge of these tasks are given in the attachment of the
ToR; the attachment is not part of the ToR and can bechanged by the Directing Board with two-third majority.
2.3 Data Centers
The IGETS Data Centers are repositories of any data
products, including station log files. Their primaryobjectives are to collect, archive and distribute these datawith efficiency and reliability. Data centers may mirror
some of the other data centers to increase the accessibilityof the IGETS datasets.
The primary Data Center hosts all SG data products(Levels 1, 2 and 3). A secondary Data Center is hosting allother datasets, including the historical products. The
institutions currently in charge of these tasks are given in
the attachment of the ToR, and can be changed by the
Directing Board with a twoǦthirds majority of voting
members.
2.4 Central Bureau
The Central Bureau is the executive arm of the IGETS
Directing Board, and is responsible for all operational
activities of the Service. The Central Bureau coordinates
IGETS activities, facilitates communications, maintains
documentations and organizes reports, meetings andworkshops.
The Central Bureau operates on a term of four years.
One year prior to the end of each term, the IGETS
Directing Board formally reviews the performances of theCentral Bureau, and may then request the Central Bureau
to reconfirm its commitment to serve another four years. If
the Central Bureau agrees, it submits a proposal for
approval by the Directing Board. If the Central Bureau
declines, or if the Directing Board chooses to change theCentral Bureau, the Directing Board announces a call for
proposal for a new IGETS Central Bureau, to take theresponsibility including a six-month transition phase.

The Director of the Central Bureau serves as a memberof the Directing Board.
IGETS will accept proposals at any time from scientificindividuals, groups or institutions to become a new
permanent component of the service (this can be a newstation, or an analysis and/or data center). The Directing
Board will review such proposals for approval.

3. Directing Board
3.1 Role and responsibilities
The Directing Board sets the objectives, determines
policies, adopts standards, and sets the scientific andoperational goals for IGETS. The Directing Board
exercises general oversight of the activities of IGETS
including modifications to the organization that are
deemed appropriate and necessary to maintain efficiency
and reliability. The Directing Board may determine
appropriate actions to ensure the quality of the IGETS
products.
3.2 Membership
The Directing Board consists of representatives of the
IGETS
components,
members-atǦlarge,
appointed
members and ex officio members. Its members are:
Elected Members (5)x Raw Data Preparation representative;x Analysis Center representative;x Data Center representative;
x Network representative;x Scientific Product evaluation representative.
Appointed Members (5)x Director of the Central Bureau;x Absolute Gravity Data Base representative;x IAG representative;x BGI representative;x IGFS representative.
Members at large (2)x The members of the Directing Board elect the Members
at large in a second round after their nomination orelection, to insure a better geographical distribution.
3.3 Elections
IGETS associates are voting for the elected members.
The elected members have staggered fourǦyear terms.
There is no limit to the number of terms that a person may
serve, however he/she may serve only two terms
consecutively as an elected member. All IGETS associates

International Geodynamics and Earth Tide Service (IGETS)

1185

are eligible to vote. Election is by a simple majority of
votes received for each position. A vote by the Directing
Board will resolve any situation of a tie.

Attachment of the ToR

3.4 IGETS Chair
The IGETS Chair is one of the Directing Board members
and is elected by the Board for a term of four years withthe possibility of reelection for one additional term. The
Chair is the official representative of IGETS to externalorganizations.

The primary Analysis Center, in charge of computing
Level 2 products is hosted by the University of Polynesia(Tahiti, French Polynesia).
The secondary Analysis Center, in charge of computing
the final gravity residuals is the EOST (Ecole etObservatoire des Sciences de la Terre) (Strasbourg,
France).

3.5 Decisions

Data Centers

Most decisions by the Directing Board are made byconsensus or by simple majority vote of the memberspresent. In case of a tie, the Chair decides how to proceed.
If a two-thirds quorum is not present, the vote shall be held
later by electronic mail. A two-thirds vote of all Board
members is required to modify the Terms of Reference, tochange the Chair, or to replace any of the members before
their normal term expires.

The primary Data Center is the Information Systems andData Center (ISDC) at GFZ (Potsdam, Germany),
responsible for the collection of Levels-1, 2 and 3 data.
The other datasets, including the historical products, arehosted at EOST (Strasbourg, France).

3.6 Meetings
The Directing Board meets at least annually or more
frequently if meetings are called by the Chair or at therequest of at least three Board members. The Board willconduct periodic reviews of the IGETS organization andits mandate, functions, and components.

4. Definitions
4.1 Associate Members
Individuals associated with organizations that support an
IGETS component may become IGETS Associate
Members. Associate Members take part in the election of
the incoming members of the Directing Board.
4.2 Corresponding Members
IGETS Corresponding Members are individuals who
express interest in receiving IGETS publications, wish toparticipate in workshops or scientific meetings organizedby IGETS, or generally are interested in IGETS activities.

Analysis Centers

Central Bureau
The Central Bureau is hosted by the EOST (Strasbourg,
France).
Founding Committee and current Directing Board (2016)
Chair of IGETS:
H. Wziontek, Germany
Director of the Central Bureau:
J.-P. Boy, France
Raw Data Preparation Represent.: V. Palinkas, Czech
Analysis Center Representative: J.-P. Barriot, France
Data Center Representative:
C. Foerste, Germany
Network Representative:
H.-P. Sun, China
Scientific Product Evaluation Rep.: B. Meurers, Austria
Members at Large:
D. Crossley, USA
J. Hinderer, France
Absolute Gravity Database Rep.: H. Wziontek, Germany
IAG Representative:
S. Pagiatakis, Canada
BGI Representative:
S. Bonvalot, France
IGFS Representative:
N. Sneeuw, Germany

IAG Scientific Services

1186

International Gravimetric Bureau
Bureau Gravimétrique International (BGI)
Director: S. Bonvalot (France)
http://bgi.obs-mip.fr

Terms of Reference

Missions and objectives

Introduction

The main task of BGI is to collect, on a world-wide basis,
all gravity measurements (relative or absolute) and pertinent information about the gravity field of the Earth, tocompile and validate them and store them in acomputerized data base in order to redistribute them onrequest to a large variety of users for scientificapplications. With this aim, BGI has the responsibility of 4
global scientific gravity databases:- Relative gravity measurements (land surveys)- Relative gravity measurements (marine surveys)- Absolute gravity measurements (free fall techniques)- Reference gravity stations (International gravity network).

The Bureau Gravimétrique International (BGI) has beencreated in 1951 as a service of IAG during the IUGG
(International Union in Geophysics and Geodesy) General
Assembly. The initial task of BGI was to collect, on aworld-wide basis, all gravity measurements to generate a
global digital database of gravity data for any public or
private user. The technological and scientific evolutions
which occurred over the last 50 years in the area of gravimetry (improvements in field, airborne and seaborne
gravity meters, development of absolute gravity meters,
space gravity missions, etc.) provided significant increasesof the number, diversity and accuracy of the gravity fieldobservables. Following these evolutions, the BGI has contributed to provide original databases and services for awide international community concerned by the studies of
the Earth gravity field.
The BGI is an official service of the International
Association of Geodesy (IAG) and is coordinated since2003, with others IAG services (IGeS, ICET, ICGEM,IDEMS) by the International Gravity Field Service (IGFS).
It also directly contributes to the activities of the IAG
Commission 2 “Gravity Field” and of the IAG Global
Geodetic Observing System (GGOS). It is recognized by
the International Council for Science (ICSU) successively
as one of the services of the Federation of Astronomicaland Geophysical Services (FAGS) and of the World Data
System (WDS) created in 2008.

Product and services
Database of relative gravity data
The database of relative measurements contains over 12
million of observations compiled and computerized mostly
from land and marine gravity surveys. It has been extensively
used for the definition of Earth gravity field models and formany applications in geodesy, satellite orbit computation,
oceanography, geophysics, etc. It provides today the mostprecise information available on the Earth gravity field atshort wavelengths and is highly complementary to airborneand satellite gravity measurements. Database access toland and marine gravity data:- http://bgi.obs-mip.fr/data-products/Gravity-Databases/
Land-Gravity-data- http://bgi.obs-mip.fr/data-products/Gravity-Databases/
Marine-Gravity-dataInternational Gravimetrique Bureau – Bureau Gravimétrique International (BGI)

Database of absolute gravity data
The database for absolute gravity measurements was set up
in 2008 in cooperation between BGI and BKG (Bundesamt
für Kartographie und Geodäsie, Germany). This database(AGrav) has the ability to store information about gravity
observations (raw or processed data), stations, instruments,
involved institutions, contacts, etc. It has been designedwith two main objectives : (i) at providing information to
the scientific community on existing absolute gravity
stations and measurements and (ii) at ensuring storage andlong term availability of gravity data and processing details.
The database can be accessed by a web based interface which
provides publicly available meta-data as well as complete
datasets for community of users contributing to thearchive. A simple exchange format was selected which
includes all relevant information and is known by the
majority of users avoiding additional effort. In this way the
upload of absolute gravity data to the database can be doneby the owner institutions, using a web based upload form.
Database access to absolute gravity data:- http://bgi.obs-mip.fr/data-products/Gravity-Databases/
Absolute-Gravity-data- http://agrav.bkg.bund.de/agrav-meta/
Database of gravity reference stations
Reference gravity stations established and connected to theprevious IGSN71 and Potsdam reference systems havebeen previously collected and archived at BGI. For several
decades, these stations have provided the only information
available on gravity value for tying local or regional
relative gravity surveys in a global reference frame. Evenif a significant number of reference stations should havedisappeared with time, the database is still accessible at thefollowing link:- http://bgi.obs-mip.fr/data-products/Gravity-Databases/
Reference-Gravity-Stations
In a next future, this gravity reference network should
be advantageously replaced by the increasing network of
actual absolute gravity measurements as provided by the
Absolute gravity database (AGrav).
Global or regional gravity grids and models
BGI also contributes to the realization of derived gravity
products with the aim to provide relevant information on
the Earth gravity field at global or regional scales. The
products mostly used by scientific users are the World
Gravity Maps and Grids (WGM) which represent the firstgravity anomalies computed in spherical geometry taking
into account a realistic Earth model.

1187

The World Gravity Map (Fig. 1) is a set of 3 global
anomaly maps of the Earth’s gravity field realized for theCommission for the Geological Map of the World (CGMW),
UNESCO, International Union of Geodesy and Geophysics(IUGG) and International Union of Geological Sciences(IUGS). Maps available at: http://ccgm.org/en/16-catalogue
The WGM is also available as digital high resolution
global grids of Bouguer, isostatic and surface free-air
anomalies. These grids derived from available Earthgravity models (i.e. EGM2008) include high resolution
terrain corrections including the contribution of mostsurface masses (atmosphere, land, oceans, inland seas,lakes, ice caps and ice shelves). Such gravity anomalies,
which point out the density heterogeneities in the Earth’s
interior (crust, mantle…), are used in a large variety of
applications. Global or regional gravity grids available at:- http://bgi.obs-mip.fr/data-products/Grids-and-models/
wgm2012
Other services
x Delivery of DOI (Digital Object Identifier) for gravity
data set or products
x Online tools for prediction gravity at a given sitex Tools and software for data acquisition or validation

Key activities
The current activities at BGI are mostly dedicated (i) toconsolidate and validate the terrestrial gravity databases(relative and absolute measurements) and (ii) to ease theconsultation and retrieval of gravity data and products by
end-users. BGI also contributes with its supporting organizations to research and educational activities (summer schools on
gravity data acquisition and processing, provision oftutorials and educational materials in gravimetry).
x Gravity databases: The main achievements consist in
maintaining and developing the BGI databases (relative
and absolute gravity database, reference gravity
stations). The collection / compilation of new dataset(from field, marine or airborne surveys) is encouraged inorder to improve the global data coverage and accuracy.
Incoming datasets are evaluated and validated using
protocols and software developed at BGI. Global dataand products derived from satellite altimetry and gravity
missions are to be more and more frequently used tovalidate land and sea measurements.
x Gravity products: As done for the digital World Gravity
Map, new products are currently under development for
updating global or regional gravity products (maps andgrids) for educational and research purposes.

IAG Scientific Services1188

x Contribution to Newton’s Bulletin: BGI contributes
jointly with the International Service for Geoid (ISG) tothe edition of this Bulletin which publish technicalpapers on gravity data acquisition and processing.
x Contribution to the Establishment of a Global Absolute
Gravity Reference System: BGI contributes within the

IAG commission 2 “Gravity Field” and Joint Working
Group JWG2.1 to the definition of this new absolutegravity network that will replace the obsolete IGSN71.
x Contribution to International summer schools on gravity
or geoid in collaboration with ISG and IGFS.

Fig. 1 World Gravity Map

Data policy / DOI (Digital Object Identifier)Data, products or software available at BGI are mostly
dedicated to support scientific and academic activities.
Digital gravity data or products are distributed free ofcharge to research or academic institutions or to data
contributors according to the conditions given below.
Other users, individual or private companies, are invited to
specify in their request the expected use of the data andproducts. See BGI website for diffusion and charging
policies.

x Access to non-confidential or non-proprietary relative
gravity measurements is provided free of charge to
public institutions or data contributors over geographic
areas limited to 20°x20° or on the base of a maximum
number of 10000 data points (land data) and/or 100000
data points (marine data). Retrieval of full data coverage
for a whole country is not included in that case. All otherrequests (for larger datasets, for extended geographic
area or for a whole country) as well as massive data retrieval will be subject to an evaluation by BGI who
might require a specific protocol of use of the data or ask

International Gravimetrique Bureau – Bureau Gravimétrique International (BGI)

authorization of the proprietary Institutions. Charges
might be appliedx Access to the Absolute gravity database is provided freeof charge without any restriction. Data retrieval is done
through the Web interfaces at BGI and BKG mirror sites.
Confidential data or proprietary data may appear with restricted information (metadata only).
x Access to the Reference gravity stations database is provided free of charge without any restriction. Please notethat reference gravity stations (especially those determined and described decades ago) may have been
destroyed or modified.
x Access to other services is also provided free of charge:
global or regional gravity anomaly grids; Prediction ofgravity value on Earth ; Software ; Documentation, etc.
Since 2016, users are invited to make reference to thegeneric DOI (Digital Object Identifier): 10.18168 for
acknowledging BGI services. As an IAG Service, BGI has
also the ability to deliver a DOI to any institution or author
for archiving their own dataset resulting from gravity
survey or gravity data compilation. This new service will
ensure proper reference to authors and institutions who
have acquired or compiled gravity data and a better
traceability of improvements in the global gravity data
coverage from local or regional surveys.

Structure and membership
Since 2003, the BGI is one of the services of the International Gravity Field Service (IGFS) which coordinates
within the IAG, the servicing of the geodetic and geophysical community with gravity field-related data, software andinformation.
The BGI central office (management, secretariat andtechnical staff) is located in Toulouse, France, in thepremises of the Observatoire Midi-Pyrénées. Since 1998,
BGI is supported by French Institutions, Universities andLaboratories (see below) whose contributions to BGI overfour year renewable periods are defined by a covenant. The
supporting French organizations are:x Centre National d'Etudes Spatiales (CNES)
x Bureau de Recherches Géologiques et Minières (BRGM)
x Centre National de la Recherche Scientifique (CNRS)
x Institut National des Sciences de l'Univers (INSU)
x Institut National de l’Information Géographique etForestière (IGN)
x Institut de Recherche pour le Développement (IRD)x Service Hydrographique et Océanographique de laMarine (SHOM)x Institut Français de Recherche pour l’Exploitation de laMer (IFREMER)

1189

x Groupe de Recherches en Géodésie Spatiale (GRGS)x Institut de Physique du Globe de Paris (IPGP)x Ecole et Observatoire des Sciences de la Terre (EOST)
x Ecole Supérieure des Géomètres et Topographes (ESGT)x Université de Toulouse (GET/OMP)
x Université de Montpellier (Géosciences Montpellier)
Each supporting organization has a representative
member in the BGI Advisory Board. The Advisory Board(who also includes a representative member of IAG)
contributes once a year to the orientation and evaluation of
the BGI activities. The program of BGI activities is also
evaluated and discussed by the IGFS Advisory Board ateach IGFS meetings and IUGG General Assemblies. A
new partnership has been also established in 2008 between
BGI and the Bundesamt für Kartographie und Geodäsie(BKG), Germany, for the realization and the maintenanceof the global database of absolute gravity measurements(AGRAV).

Providing and referencing data to BGIAs a service of IAG/IGFS, the final task of BGI is to giveaccess to the largest scientific community to relative andabsolute measurements of the Earth gravity field andrelated information. The permanent archiving of new incoming gravity data sets is crucial to improve the coverage
and accuracy of the global gravity database and to improve
our knowledge of the Earth gravity field. It also enables
BGI to validate the gravity observations in a global reference frame and restore them in standard and unified
formats useful for various users.
BGI currently collect & provides information on:
x Relative gravity measurements from land, marine & airborne surveys
x Absolute gravity measurements
x Reference gravity base stations
x Software for gravimetric applications (data processing,modeling, etc.)
x Other gravimetry-related information (printed or digitalmaps, bibliography, etc.)
The contribution of scientists, agencies or institutions involved in these fields is welcome to ensure the best service
to the community. Contributors interested in archiving
their gravity observations as non-confidential or as proprietary data (to be defined by the contributors themselves)
are invited to contact BGI. For relative gravity observations, all kind of data from land, marine or airborne surveys can be sent to BGI. ASCII data files containing allnecessary information and quantities are preferred (station
coordinates, gravity measurements and accuracies; gravity
corrections; reference geographic, height and gravity
systems, etc.). For absolute gravity observations, the data-

1190

base is maintained on two mirror sites located in Toulouse(France), at BGI and in Frankfurt/Main (Germany), at theFederal Agency for Cartography and Geodesy (BKG).
Scientists interested to upload their observations or metadata only (site positions and approximated values for
instance) in the international Absolute Gravity database
AGRAV are invited to contact either BGI (http://bgi.obsmip.fr) or BKG (http://agrav.bkg.bund.de/agrav-meta/).
For any contribution (relative or absolute gravity data), it isreminded that BGI will keep the status of diffusion (withor without restrictions of redistribution) as specified by the
proprietary institution.
Noticex For making reference to BGI service, use doi: 10.18168
x For asking attribution of a DOI for a given dataset: sent
request to bgi@cnes.fr.
Contacts
Bureau Gravimétrique International
Observatoire Midi-Pyrénées
14, Avenue Edouard Belin
31401 Toulouse Cedex 9, France
Phone: 33-5 61 33 29 80
E-mail: bgi@cnes.fr, sylvain.bonvalot@ird.fr

Staff members & experts
S. Bonvalot (Director)
G. Balmino
A. Briais
S. Bruinsma
G. Gabalda
F. Reinquin
L. Seoane
V. Carassus
H. Wziontek
M. Diament
T. Gattacceca
O. Jamet
M-F. Lalancette
G. Martelet
I. Panet
J.-P. BoyJ.-D. Bernard
N. Le Moigne
C. Salaun
J. HindererU. Marti (IAG Representative)

IAG Scientific Services

International Service for the Geoid (ISG)

1191

International Service for the Geoid (ISG)
President: Mirko Reguzzoni (Italy)
Director: Giovanna Sona (Italy)
http://www.isgeoid.polimi.it

Mission / Objectives
The main tasks of ISG are:x to collect geoid estimates worldwide, when possible tovalidate them and to disseminate them upon request
among the scientific community: other auxiliary data
can also be collected by ISG, when useful for the geoid
determination, and might be made available with the
sharp exclusion of gravity anomaly data,x to collect, test and, when allowed, to distribute software
for the geoid determination,
x to conduct researches on methods for the geoid
determination, particularly trying to define optimal
procedures for merging all the available data, including
satellite gravity,
x to organize schools on geoid determination where boththeoretical and practical aspects are illustrated. During
the schools, students are trained in the use of therelevant software for geoid computation,
x to issue, possibly once per year, the Newton’s Bulletin,collecting papers on gravity and geoid. Also, news andresults from the other IGFS Centres are welcome,x to disseminate special publications on geoid
computations, e.g. lecture notes of the schools,
x to establish and update a webpage and a forum fordiscussing practical and theoretical aspects on geoid
computation,
x to support Agencies or scientists in computing regional
geoids.
The Newton’s Bulletin has a technical and applied nature
and will not accept papers that could be published in the
Journal of Geodesy.
Data and software given to ISG remain property of thesource, which can dictate the conditions of use and restrict

their distribution. ISG itself can indeed perform geoid
computations within different projects, but not in economic
competition with Firms or Public Organizations
institutionally devoted to that.

Products
x Software for handling global models,x Software for the local geoid estimation,x Software for the evaluation of different functionals of
the gravity field,
x Grids of local and regional geoid estimates, for specificareas and delivered in a specific file format,
x Documentation on software and data,x Newton’s Bulletin,x Lecture notes and special publications,x International Schools on geoid computation.

Future Programs/Development
Beyond institutional activities, the following ISG programs
are worth of specific mention:
x computation of improved geoids for Italy and theMediterranean area,
x support to local and regional geoid computations,especially in developing countries,
x integration of ground, air-borne, ship-borne and satellite
gravity data for geoid modelling,x participation within GGOS to the study of the heightdatum unification problem,x participation within IGFS to the validation of new
global gravity models,1192

x participation to a Joint Working Group of the IAG
Commission 2 on “Integration and validation of local
geoid estimates”,
x study of improved methodologies for the determinationof the geoid at global and local level,x organization of International Geoid Schools, possibly
one every two years.

Structure
ISG is an official IAG service which is coordinated by
IGFS and is also related to the activities of the IAG
Commission 2 on Gravity Field. Its structure, tools andactivities are illustrated in the ISG reports to the Advisory
Board of IGFS.
The Service is for the moment provided by two Centres,
one at the Politecnico di Milano and the other at NGA. The
ISG Milano Centre is supported by Italian authorities,
which nominate upon recommendation of IGFS, a
President for its international representation and a Director
for the operative management. In addition the ISG advisors
are individual members of ISG, which have or have had an
outstanding activity in the field of geoid determination andcan also represent ISG in both research and teachingactivities.
At present the following distinguished scientists are ISG
advisors:
D. Blitzkow (Brazil)
H. Denker (Germany)
R. Forsberg (Denmark)J. Huang (Canada)
W. Kearsley (Australia)
U. Marti (Switzerland)
N. Pavlis (USA)L. Sánchez (Germany)
M. Sideris (Canada)
I. Tziavos (Greece)
Finally, within the structure of ISG, Working Groups canbe established for specific purposes, limited in time.

IAG Scientific Services

Permanent Service for Mean Sea Level (PSMSL)

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Permanent Service for Mean Sea Level(PSMSL)
Director: L. J. Rickards (UK)
http://www.psmsl.org

Development
Since 1933, the Permanent Service for Mean Sea Level(PSMSL) has been responsible for the collection, publication, analysis and interpretation of sea level data fromthe global network of tide gauges. It is based at the
National Oceanography Centre (NOC), Liverpool, which is
a component of the UK Natural Environment ResearchCouncil (NERC). It is funded by NERC. The PSMSL continues to be one of the main data centres for both the International Association for Physical Sciences of the Oceans(IAPSO) and the IAG. The PSMSL operates under the
auspices of the International Council for Science (ICSU)
and reports formally to IAPSO’s Commission on Mean
Sea Level and Tides. The PSMSL is a regular member ofthe World Data System of ICSU.

Mission/Objectives
The mission of the PSMSL is to provide the community
with a full Service for the acquisition, analysis and interpretation of sea level data. Aside from its central role ofoperation of the global sea level data bank, the PSMSL
provides advice to tide gauge operators and analysts. It
occupies a central management role in the development of
the Global Sea Level Observing System (GLOSS) andhosts important international study groups and meetings on
relevant themes. Several such meetings took place in 2013
to mark the 80th Anniversary of the PSMSL.

Products
The database of the PSMSL contains over 66000 stationyears of monthly and annual values of mean sea level(MSL) from over 2250 tide gauge stations around theworld received from approximately 200 national
authorities. On average, approximately 1500 station-yearsof data are entered into the database each year. This
database is used extensively throughout the sciences ofclimate change, oceanography, geodesy and geology, andis the main source of information for international study
groups such as the Intergovernmental Panel on Climate
Change (IPCC).
Data for all stations are included in the PSMSLMETRIC (or total) data set. The METRIC monthly andannual means for any one station-year are necessarily
required to be measured to a common datum, although, at
this stage, datum continuity between years is not essential.
The year to-year datum checks become essential, however,if the data are subsequently to be included in the PSMSL'Revised Local Reference (RLR)' component of the data set.
The 'Revised Local Reference (RLR)' dataset of the
PSMSL contains records for which time series analysis ofsea level changes can be performed. Long records fromthis dataset have been the basis of all analyses of secularchanges in global sea level during the last century. The
geographical distribution of longer RLR records contains
significant geographical bias towards the northern hemisphere, a situation which is being rectified by the establishment of the GLOSS global sea level network.
The PSMSL is also responsible for the Higher Frequency Delayed Mode (HF DM) data set of sea level
information from the GLOSS Core Network. This consistsof the original sea level measurements from each site(typically hourly values) which provide a strategic backup
to the MSL information of the main PSMSL data set.
PSMSL is working to provide data from in situ ocean
bottom pressure recorders from all possible sources, aremit given to PSMSL by IAPSO in 1999. The aim is to1194

provide consistently processed bottom pressure records
with hourly and daily sampling for use in tidal,
oceanographic and geophysical research.
In addition, the PSMSL provides a range of sea levelproducts (e.g. interactive anomaly and trend maps, tablesof sea level trends) for its users. These findings are input tonational and international scientific study groups regularly.
A range of training materials and software products arealso made available via its web site which can be consulted
for more information.

Structure/Governing Board Members
The PSMSL reports formally to the IAPSO Commission
on Mean Sea Level and Tides (President Dr. G.T.
Mitchum, USA). It is also served by an Advisory Group
which at present consists of Dr. R. Neilan (JPL, USA),
Prof. G. T. Mitchum (University of South Florida, USA),
Prof. P. L. Woodworth. (National Oceanography Centre,UK), Dr. P. Knudsen (Danish National Space Center), Dr.
R. Bingley (Nottingham University, UK), Dr. G.
Woppelmann (Universite de La Rochelle, France), Dr. T.
Aarup (IOC, UNESCO). Suggestions for improvements in
PSMSL activities may be sent directly to the PSMSL or
via the IAPSO Commission or via any member of theAdvisory Group.

Points of Contact
Permanent Service for Mean Sea Level
National Oceanography Centre
Joseph Proudman Building
6 Brownlow Street
Liverpool L3 5DA, UK.
Email: psmsl@noc.ac.uk
Web site: www.psmsl.org
Telephone: +44 (0)151-795-4800
Fax: +44 (0)151-795-4801
Staff members• L. J. Rickards (Director)• K. M. Gordon• S. Jevrejeva• A. P. Matthews• A. Hibbert• S. Williams• E. A. Bradshaw (GLOSS DM HF data set)

IAG Scientific Services

IAG on the Internet

1195

IAG on the Internet
Webmaster: Szabolcs Rózsa (Hungary)
http://www.iag-aig.org

Introduction

Publishing on the IAG Website

The IAG maintains an Internet site, which is a valuable
source of information not only about the Association itself,
but also about its scientific disciplines. The primary goal of
the website is to communicate with the IAG members, andmake information available to the wider Geosciences
community in the world as a whole.
Since the maintenance of the IAG website belongs tothe activities of the Communication and Outreach Branch(COB) it is still hosted at the Department of Geodesy and
Surveying of the Budapest University of Technology andEconomics (BME), Budapest, Hungary. The geographicaldistribution of the visitors of the IAG website can be seen
on Figure 1 for the period of September, 2015 to January, 2016.
During the past four years, the layout of the website has
been redesigned.

The IAG COB encourages all the IAG Members andGeodesists in general to publish information on the
IAG213, Fax: +36-1-463 3192.

Topic of the Month
The Topic of the Month section of the opening page aims
to promote important scientific achievements and activities
to the wider public. The latest scientific results, theestablishment of international and interdisciplinary
research projects and all other information, which may
have a great impact on the geodetic community, can beposted to this section of the website.
Since the COB intends to publish a new topic in eachmonth, Geodesists are kindly encouraged to submit new
topics to the COB e-mail address: iagcob@iag-aig.org
The Topics of the Month must include an image and ashort introduction, too. Both of them are published on the
opening page of the website, and more details are given on
separate pages.

IAG on Social MediaIn order to address the younger generations the COB has
opened the IAG page on Facebook and Twitter. As of
February 22, 2016, the page http://www.facebook.com/
InternationalAssociationOfGeodesy has 347 'likes'. The
age distribution of the likers can be seen on Figure 2.
It’s worth mentioning that the announcements on ITRF
2014 and on the February issue of the IAG Newsletter
produced more than 1400 reaches on Facebook.
The IAG Twitter site of IAG is available at:
http://www.twitter.com/iag_cob. We would like toencourage everyone who is interested in Geodesy to follow
these pages, since the latest information published on the
IAG website are available on Facebook and Twitter, too.
The followers of these pages are automatically notified
about the latest IAG news.
However our presence on the social media needs more
frequently news on Geodesy and IAG. Therefore we would
like to encourage IAG members and geodesists in generalto provide us input to be published on these sites. A good
example is the announcement of the Norwegian Mapping
Agency on the Svalbard observatory (http:// www.iagaig.org/index.php?tpl=text&id_c=79&id_t=663).
Pleasefeel free to contact the COB for publishing such geodesy
related informations , because it really helps to improve theoutreach activities of IAG.
We do appreciate your help and cooperation!

1196

General Information

Fig. 1 Geographical distribution of the page visits of the IAG website from September, 2015 and January, 2016

Fig. 2 The age distribution of Facebook likers (above: 25% of likers are women; below: 75% of likers are men)Publications of the IAG

1197

Publications of the International Association of Geodesy (IAG)

I. Journal of Geodesy
Twelve issues per year:
Annual subscription or sale by unit (Springer-Verlag)
Springer Verlag
Tiergartenstrasse 17
D – 69121 Heidelberg
Germany
www.springer.com

II. Geodesist’s Handbook
Quadrennial special issues of the Journal of Geodesy, published since 1980, contain the present IAG laws and rules,
summaries of the latest IAG General Assemblies, and thestructures and the program descriptions for all the IAG
components of the respective upcoming period.

III. IAG Symposia Series

the Quality of Geodetic Observation &Monitoring Systems (QuGOMS’11), Munich,Germany, April 13-15, 2011.
Vol. 141: Marti U. (Ed., 2014) Gravity, Geoid and Height
Systems. IAG Symposium GGHS, Venice, Italy,
October 9-12, 2012.
Vol. 142: Sneeuw N., P. Novák, M. Crespi, F. Sansò (Eds.
2016) VIII Hotine-Marussi Symposium on
Mathematical Geodesy, Rome, Italy, June 1721, 2013.
Vol. 143: Rizos Ch., P. Willis (Eds., 2016) IAG 150
Years. IAG Scientific Assembly, Potsdam,
Germany, September 1-6, 2013.
Vol. 144: Jin, S., R. Barzaghi (Eds., 2016) Proceedings ofthe 3rd International Field Service (IGFS),
Shanghai, China, June 30-July 6, 2014.
Vol. 145: Hashimoto, M. (Ed., 2016) International
Symposium on Geodesy for Earthquake andNatural Hazards (GENAH), Matsushima, Japan,
22-26 July, 2014.

Peer reviewed proceedings of selected IAG Symposia.
Available at Springer-Verlag (see under I.). Latest issues:

IV. Travaux de l’Association Internationalede Géodésie (IAG Reports)

Vol. 138: Altamimi Z., X. Collilieux (Eds., 2013)
Reference Frames for Applications inGeosciences. IAG Commission 1 Symposium,
Marne-La-Vallée, France, October 4-8, 2010.
Vol. 139: Rizos Ch., P. Willis (Eds., 2014) Earth on theEdge: Science for a Sustainable Planet. IAG
General Assembly, Melbourne, Australia, June
28 - July 2, 2011.
Vol. 140: Kutterer H., F. Seitz, H. Alkhatib, M. Schmidt(Eds., 2015) The 1st International Workshop on

The IAG Reports (Travaux de l'Association Internationalede Géodésie) are published on the occasion of the IAG
General and Scientific Assemblies every two years andcontain the reports of all IAG components and subcomponents. They were published as printed volumes until
2003 (since 1991 also available in digital form) and since2005 online only at http://www.iag-aig.org/ andhttp://iag.dgfi.tum.de/. Printed versions may be ordered at
the IAG Office (iag.office@tum.de).

General Information

1198

Geodetic Data Centres

Geodetic Publication Series

The IAG Communication and Outreach Branch (COB)
compiles and maintains a list of Geodetic Data Centres.
All data compiled in this list are regularly revised by the
IAG National Correspondents.
Considering the fact that addresses are subjected to frequent changes, the directory is stored as a file in the web tosustain the possibility of updates whenever useful. All
information is available at the IAG Website (http://
www.iag-aig.org/).
All available data are stored in the IAG Website as soon
as the responsible National Correspondent sends them tothe IAG COB (address see below). All National
Correspondents are kindly asked to inform the COB1 on
any change.

The IAG Communication and Outreach Branch (COB)
compiles and maintains a list of Geodetic Publication
Series. All data compiled in this list are regularly revisedby the IAG National Correspondents.
Considering the fact that addresses are subjected to frequent changes, the directory is stored as a file in the web tosustain the possibility of updates whenever useful. All
information is also available at the IAG Website(http://www.iag-aig.org/).
All available data are stored in the IAG Website as soon
as the responsible National Correspondent sends them tothe IAG COB (address see below). All National
Correspondents are kindly asked to inform the COB1 on
any change.

Educational Establishments for Geodesy

IAG Directory

The IAG Communication and Outreach Branch (COB)
compiles and maintains a list of addresses of Educational
Establishments for Geodesy. All data compiled in this list
are regularly revised by the IAG National Correspondents.
Considering the fact that addresses are subjected to frequent changes, the directory is stored as a file in the web tosustain the possibility of updates whenever useful. All information is also available at the IAG Website (http://
www.iag-aig.org/).
All available data are stored in the IAG Website assoon as the responsible National Correspondent sends themto the IAG COB (address see below). All National
Correspondents are kindly asked to inform the COB1 on
any change.

The IAG Directory comprises a list of addresses of geodesists who are in direct contact with the IAG by having
attended an IUGG General Assembly, IAG Scientific
Meeting, IAG Symposium in the recent years or maintainany other kind of contact. The addresses comprise thename, title, affiliation, postal address as well as phone/fax
number and e-mail address of the respective persons.
Considering the fact that addresses are subjected to frequent changes, the directory is stored as a file in the web tosustain the possibility of updates whenever useful. Any
geodesists, who is listed in the directory is kindly asked to
update this information on the IAG website directly, after
logging in to the Members’ Area. For more details, pleaserefer to the chapter IAG on the Internet in this issue.
Considering the rules of the protection of personal rights
this list is not generally open to everybody. The directoryis accessible by password for all individual IAG-members
via the IAG homepage http://www.iag-aig.org/.

1

IAG Communication and Outreach Branch (COB)
Department of Geodesy and Surveying
Budapest University of Technology and Economics
P.O.Box 91
H-1521 Budapest, Hungary
tel +36-1-463 3222/3213, Fax +36-1-463 3192
e-mail jadam@sci.fgt.bme.hu / szrozsa@iag-aig.org

IAG Delegates

1199

IAG Delegates of the IUGG Member Countries

ALBANIAEng. Msc. Bilbil Nurçe
Polytechnic University of Tirana
Civil Engineering Faculty, Department of Geodesy
Street “Muhamet Gjollesha” Nr. 54
TiranaT: 355 4 227 1417, F: 355 4 222 9045
billnurce@gmail.com

AUSTRIA
Prof. Dr. Johannes Böhm
Technische Universität Wien
Department of Geodesy and Geoinformation
Gußhausstraße 25-29
A - 1040 Wien
T: 43 1 58801 12864
johannes.boehm@geo.tuwien.ac.at

ARGENTINA
Ing. Jaime Ricardo Soto
Departamento de Agrimensura, Facultad de Ingeniería
Universidad Nacional de La Plata, Calle 47 No. 168
1900 La Plata – Prov. de Buenos Aires
T: 54 221 423 6677 int. 254
cg.snuggi@gmail.com; jrsoto1@gmail.com

AZERBAIJAN
Prof. Dr. Fakhraddin Kadirov
Geology Institute, ANAS
Av. H. Javid 29 a
1143 Baku
T: 994 12 439 2193, F: 994 12 497 5283
kadirovf@gmail.com

ARMENIA
Dr. Grigor Avetyan
Yerevan State University
1 Alex Manoogian Street
Yerevan, 0049
T: 374 10 55 47 52, F: 374 10 55 46 41
rector@ysu.am

BELGIUM
Dr. Carine Bruyninx
Koninklijke Sterrenwacht van België
Ringlaan 3
BE-1180 Brussels
T: 32 2 373 02 92, F: 32 2 374 98 22
carine.bruyninx@oma.be

AUSTRALIA
Prof. Chris Rizos
School of Surveying & Spatial Information Systems
University of New South Wales
Sydney, NSW, 2052
T: 61 2 9385 4205, F: 61 2 9313 7493
c.rizos@unsw.edu.au

BOSNIA & HERZEGOVINA
Mr.sc. Dipl.Eng. Medzida Mulic
Faculty of Civil Engineering,
Department of Geodesy University of Sarajevo
S. Tomica br.I/III
71000 Sarajevo
T: 387 33 278 444, 387 61 201 151
F: 387 33 200 158
medzida_mulic@gf.unsa.ba

1200

BRAZIL
Prof. Denizar Blitzkow
Universidade de Sao Paulo, EPUSP-PTR
Caixa Postal 61548
05413-001 Sao Paulo
T: 55 11 3091 5501, F: 55 11 3091 5716
dblitzko@usp.br
BULGARIA
Prof. D. Sc. Ivan Georgiev
Bulgarian Academy of Sciences, NIGGG
Acad. G. Bonchev Str. Bl. 3
Sofia, 1113
T: 359 2 979 2453, F: 359 2 972 08 41
ivan@bas.bg
CANADADr. Joseph Henton
Geodetic Survey Division
Natural Resources Canada
9860 West Saanich Rd.
Sidney, BC V8L4B2
T: 1 250 363 6658, F: 1 250 363 6565
jhenton@nrcan.gc.ca
CHILE
Mr. Lautaro Rivas Reveco
Instituto Geografico Militar de Chile
Nueva Santa Isabel 1640
Santiago
T: 56 2 410 9321, F: 56 2 699 0554
lrivas@igm.cl
CHINA
Dr. Prof. Yimin Dang
Chinese Acad. of Surveying and Mapping (CASM)
28 Lianhuachi Xi Rd.
Beijing, 100030
T: 86 10 6388 0701, F: 86 10 6388 0804
dangym@casm.ac.cn
CHINA - TAIPEIProf. Benjamin Fong Chao
Institute of Earth Sciences, Academia Sinica
P.O. Box 1-55 Nangkang
Taipei, Taiwan, 115
T: 886 2 2783 9910 ext 103, ext 517
F: 886 2 2783 9871
bfchao@earth.sinica.edu.tw

The Geodesist’s Handbook 2016

COLOMBIA
William Martínez
Instituto Geográfico Agustín Codazzi
División de Geodesia
Carrera 30 No. 48-51
Bogotá, D.C.
T: 57 1 369 4011, F: 57 1 369 4105
wamartin@igac.gov.co
COSTA RICA
Dr. Jorge Moya
Escuela de Topografía, Catastro y Geodesia
Universidad Nacional
Apartado 86-3000
Heredia
jmoya@una.ac.cr
CROATIADr. Tea Duplancic Leder
Faculty of Civil Engineering, Architecture and Geodesy
University of Split
Matice hvratske 15
21000 Split
T: 385 21 303 377
tleder@gradst.hr
CZECH REPUBLIC
Dr. Petr Holota
Research Inst. of Geodesy, Topography & Cartography
Ustecka 98
25066 Zdiby, Prague-East
T: 420 323 649 235; 420 284 890 907
F: 420 284 890 056
holota@pecny.asu.cas.cz
DENMARK
Mr. Niels Andersen
National Space Center, DTU
Elektrovej, Building 328, room 106
2800 Kongens Lyngby
T: 45 4525 9783, F: 45 4525 9575
na@space.dtu.dk
EGYPT
Mr. Mostafa Mousa Mohamed Rabah
National Research Institute of Astronomy and Geophysics
Helwan
T: 20 1 0106 2509 / 20 1 0048 7605
F: 20 2 2554 8020
Mostafa-rabah@yahoo.com

IAG Delegates

ESTONIA
Prof. Dr. Artu Ellmann
Dept. of Civil Engineering
Tallinn University of Technology
Ehitajate Road 519086 Tallinn
T: 372 620 2603, F: 372 620 2601
artu.ellmann@ttu.ee
F.Y.R. MACEDONIA
Prof. Dr. Zlatko Srbinoski
Ss Cyril and Methodius University
Faculty of Civil Engineering, Department of Geodesy
Blvd. Partizanski odredi 24, PO Box 560
1000 Skopje
T: 389 2 311 6066 ext. 123, F: 389 2 311 8834
srbinoski@gf.ukim.edu.mk
FINLAND
Prof. Markku Poutanen
Finnish Geodetic Institute
Geodeetinrinne 202430 Masala
T: 358 9 2955 5216, 358 40 718 2152
F: 358 9 2955 5200
Markku.poutanen@fgi.fi
FRANCE
Dr. Francoise Duquenne
5 rue Mésanges
14280 Saint-Contest
T: 33 2 3144 5562
fh.duquenne@wanadoo.fr
GEORGIADr. Tengiz Gordeziani
Javakhishvili Tbilisi State University
0160 Tbilisi
T: 995 32 717 046, F: 995 32 222 110 1277
tengizgordeziani@gmail.com
GERMANY
Prof. Dr.-Ing. Jürgen Müller
Institut für Erdmessung, Universität Hannover
Schneiderberg 50
30167 Hannover
T: 49 511 762 3362, F: 49 511 762 4006
mueller@ife.uni-hannover.de

1201

GHANA
Chief Director Thomas M. Akabza
Geology Department, University of Ghana, Legon
Accra
T: 233 24 632 5685
takabzaa@ug.edu.gh
GREECE
Prof. Elias Tziavos
School of Rural and Survey Engineering
Aristotle University of Thessaloniki, Faculty ofEngineering
541 24 Thessaloniki
T: 30 2310 996 125, F: 30 2310 995 948
tziavos@topo.auth.gr
HUNGARY
Prof. Dr. József ÁdámDepartment of Geodesy and Surveying
Budapest University of Technology and Economics
P.O. Box 91
H-1521 Budapest
T: 36 1 463 3222, F: 36 1 463 3192
jadam@sci.fgt.bme.hu
ICELAND
Mr. Magnus Gudmundsson
National Land Survey of Iceland
Stillholt 16-18
300 Akranes
T: 354 430 9000, F: 354 430 9090
magnus@lmi.is
INDIA
Dr. Vijay Prasad Dimri
CSIR-Distinguished Scientist (HAG+)
National Geophysical Research Institute (CSIR-NGRI)
Uppal Road
Hyderabad, 500 007
T: 91 40 2343 4655, F: 91 40 2343 4651
dimrivp@yahoo.com
INDONESIAMr. Hasanuddin Z. Abidin
Department of Geodetic Engineering
Institute of Technology of Bandung
Jl. Ganesa 10
Bandung 40132
T: 62 22 2534286, F: 62 21 253 0702
hzabidin@gd.itb.ac.id

The Geodesist’s Handbook 2016

1202

IRAN
Assoc. Prof. Dr. Vahid Ebrahimzadeh Ardestani
Institute of Geophysics, University of Tehran
P.O. Box 14155-6466
14394 Tehran
T: 98 21 802 1072, 98 21 8802 1077
F: 98 21 800 9560
ebrahimz@ut.ac.ir
IRELAND
Mr. Colin D. Bray, Chief Technical Officer
Ordnance Survey Ireland
Phoenix Park
Dublin 8
T: 353 1 8025 308, F: 353 1 8204 156
colin.bray@osi.ie
ISRAEL
Dr. Gilad Even-Tzur
Faculty of Civil Engineering
Technion – Israel Institute of Technology
Haifa, 32000
T: 972-4-829-3459, F: 972-4-823-4757
eventzur@tx.technion.ac.il
ITALY
Prof. Mattia Crespi
Department of Civil, Building and Environmental
Engineering
Faculty of Civil and Industrial Engineering
University of Rome “La Sapienza”
Via Eudossiana, 1800184 Rome
T: 39 06 4458 5097, F: 39 06 4991 5097
mattia.crespi@uniroma1.it
JAPAN
Prof. Kosuke Heki
Department of Natural History Sciences
Hokkaido University
N10, W8, Kita-ku, Sapporo
Hokkaido, 060-0810
T: 81 11 706 3826, F: 81 11 706 3826
heki@mail.sci.hokudai.ac.jp
KOREA
Dr. Pil-Ho Park
Korea Astronomy and Space Science Institute61-1, Hwaam-dong, Yuseong-gu
Daejeon, 305-348
T: 82 42 865 3232, F: 82 42 861 5610
phpark@kasi.re.kr

LUXEMBOURG
Ing. Germain Breger
Administration des Services du Géomètre
3, rue du Laboratoire, Ville de Luxembourg
L 1911 Luxembourg
T: 352 47 96 2394, F: 352 22 35 36
gbreger@vdl.lu
MEXICO
Dr. Enrique CabralInstituto de Geofisica - UNAM
Ciudad Universitaria
04510, Mexico, D.F.
T: 52 55 5622 4120, F: 52 55 5616 2547
ecabral@geofisica.unam.mx
MOZAMBIQUE
Mr. José Luis Quembo
CENACARTA
Caixa Postal 83
MaputoT: 285 21 300486, F: 285 21 321959
jlquembo@gmail.com
NEW ZEALAND
Dr. Matt Amos
Land Information NZ
PO Box 5501
Wellington 6145
T: 64 4 460 0559
mamos@linz.govt.nz
NICARAGUA
Mr. Marvin Corriols
IGG/CIGEO UNAN
De la Rotonda Universitaria 1 km al Sur
Villa Fontana, Apdo. Postal 6631
Managua
T: 505 22703983
marvincorriols@hotmail.com
NIGERIA
Prof. Francis I. Okeke
Department of Geoinformatics and Surveying
Faculty of Environmental Sciences,
University of Nigeria, Unugu Campus
Enugu
T: 234 803 562 7286
francisokeke@yahoo.com

IAG Delegates

NORWAYMr. Oddgeir Kristiansen
Norwegian Mapping Authority, Geodetic Institute3507 Honefoss
T: 47 3211 8299, F: 47 3211 8101
oddgeir.kristiansen@kartverket.no
PAKISTAN
Deputy Director Mr. Rauf Ahmed
Survey of Pakistan, Surveyor General's Office
Murree Road
Rawalpindi
T: 92 51 929 0213, F: 92 51 929 0229
svyofpak@yahoo.com
PERU
M.Sc. Edmundo Norabuena
Instituto Geofisico del PerúCalle Calatrava 216, Urb. Camino Real, La Molina
Lima 12
T: 51 1 436 8437, F: 51 1 436 8437
enorab@geo.igp.gob.pe
PHILIPPINES
Prof. Epifanio D. Lopez
Department of Geodetic Engineering,
University of the Philippines
Diliman 1101 Quezon City
T: 632 920 8924, F: 632 920 8924
epifanio.lopez@up.edu.ph
POLAND
Prof. Dr. Jan Krynski
Institute of Geodesy and Cartography
Modzelewskiego St. 27
02-679 Warsaw
T: 48 22 329 1904, F: 48 22 329 1950
krynski@igik.edu.pl
PORTUGAL
Eng. João Manuel Agria Torres
SPUIAGG, Instituto Geofisico do Infante D. Luis
Universidade de Lisboa
Rua de Escola Politecnica 58
1250-102 Lisboa
T: 351 21 390 3311, F: 351 21 395 3327
jatorres@iol.pt

1203

ROMANIA
Prof. Dr. Johann Neuner
Technical University of Civil Engineering
Bdul Lacul Tei, nr. 124
020396 Bucharest
T: 40 21 2433621, F: 40 21 2420793
neuner@utcb.ro, hneuner@rdslink.ro
RUSSIA
Prof. Viktor P. Savinykh
Moscow State University of Geodesy and Cartography
4 Gorokhovsky per.
105064 Moscow
T: 7 499 763 34 32, F: 7 499 267 46 81
svp@miigaik.ru
SAUDI ARABIA
Dr. Abdullah Arrajehi
King Abdulaziz City for Science and Technology(KACST)
P.O. Box 6086
Riyadh 11442
T: 966 1 488 3444 ext. 3535, F: 966 1 481 3526
arrajehi@kacst.edu.sa
SLOVAK REPUBLIC
Dr. Ladislav Brimich
Geophysical Institute, Slovak Academy of Sciences
Dubravska Cesta 9845 28 Bratislava 45
T: 421 2 5941 0600, F: 421 2 5941 0626
geofbrim@savba.sk
SLOVENIA
Prof. Dr. Bojan Stopar
University of Ljubljana, Geodetic Department
Jamova 2
SI- 1115 Ljubljana
T: 386 1 476 8500, F: 386 1 425 0681
bojan.stopar@fgg.uni-lj.si
SOUTH AFRICA
Prof. Ludwig Combrinck
University of Pretoria, HartRAO
Department of Geography, Geoinformatics andMeteorology
PO Box 443
Krugersdorp, 1740
T: +27 12 301 3224, F: +27 12 326 0756
ludwig@hartrao.ac.za

1204

SPAIN
Prof. Miguel J. Sevilla
Instituto de Astronomía y Geodesia
Facultad de Ciencias Matemáticas
Universidad Complutense
28040 Madrid
T: 34 91 394 4582, F: 34 91 394 4615
sevilla@mat.ucm.es

The Geodesist’s Handbook 2016

UNITED KINGDOM
Prof. DPhil Peter J. Clarke
School of Civil Engineering & Geosciences
G.12 Cassie Building, Newcastle University
Newcastle upon Tyne NE1 7RU, UK
T: 44 191 222 6351 (direct) or 6323, F: 44 191 222 6502
Peter.Clarke@newcastle.ac.uk

SWEDENDr. Jonas Ågren
Swedish Mapping, Cadastre and Registry Authority
Geodetic Research DivisionSE- 801 82 Gävle
T: 46 26 663 420, F: 46 26 687 594
Jonas.Agren@lm.se

USA
Prof. Dr. Jeffrey Freymueller
Geophysical Institute and Department of
Geodesy and Geophysics, University of Alaska, Fairbanks
POB 757320
Fairbanks, AK 99775-7320
T: 1 907 474 7286, F: 1 907 474 7290
jeff@giseis.alaska.edu / jeff.freymueller@gi.alaska.edu

SWITZERLAND
Mr. Adrian Wiget
Federal Office of Topography swisstopo
Senftigenstrasse 264
CH-3084 Wabern-Bern
T: 41 31 963 2469, F: 41 31 963 2459
Adrian.Wiget@swisstopo.ch

VIETNAM
Dr. Duong Chi Cong
Vietnam Institute of Geodesy and Cartography
479 Hoang Quoc Viet, Cau GiayHanoi
T: 84 4 6269 4426, F: 84 4 3754 0186
chicong.duong@gmail.com

THAILAND
Lt. Gen. Nopphadon Chotsiri, Director
Royal Thai Survey Department
Kalayanamaitri Street, Phranakhon
Bangkok, 10200
T: 66 2 221 2884
nopphadon@rtsd.mi.th
THE NETHERLANDS
Prof. Dr. Ir. Peter J. G. Teunissen
Delft University of Technology
Faculty of Civil Engineering and Geosciences
Department of Geoscience and Remote Sensing
PO Box 5048
2600 GA Delft
T: 31 15 278 2558, F: 31 15 278 3711
P.Teunissen@curtin.edu.au
TURKEY
Col. Eng. Yücel Ünver
Head of Geodesy Department
General Command of Mapping
6100 Dikimevi/Cankaya, Ankara
T: 90 312 595 2250, F: 90 312 320 1495
yucel.unver@hgk.msb.gov.tr

IAG Representatives to Scientific Bodies

1205

IAG Representatives to Scientific Bodies

IAG Services

IUGG Working Groups

x BGI: Urs Marti (Switzerland)
x BIPM: Richard Biancale (France)x ICGEM: Riccardo Barzaghi (Italy)
x IDEMS: Riccardo Barzaghi (Italy)
x IDS: Michiel Otten (Germany)x IERS: Axel Nothnagel (Germany)x IGETS: Spiros Pagiatakis (Canada)
x IGFS: Urs Marti (Switzerland)
x IGS: Chris Rizos (Australia), Zuheir Altamimi (France)
x ILRS: Geoffrey Blewitt (USA)x ISG: Roland Pail (Germany)x IVS: Ludwig Combrinck (South Africa)
x PSMSL: Per Knudsen (Denmark)x WGH (Working Group on History):
Claude Boucher (France), József Adám (Hungary)IUGG Commissions and Committees
x CCEC (Comm. on Climate & Environmental Changes):
Tonie van Dam (Luxembourg)
x CMG (Commission on Mathematical Geophysics):
Shin-Chan Han (USA)x GRC (Geophysical Risk and Sustainability):
Jeff Freymueller (USA)x SEDI (Study of Earth's Deep Interior):
J. Hagedorn (Germany)x UCDI (Union Commission for Data and Information):
Bernd Richter (Germany), Ruth Neilan (USA)x UCPS (Union Commission on Planetary Sciences):
Jürgen Oberst (Germany), Oliver Baur (Austria), Pieter
Visser (The Netherlands)
x IUGG Statutes and By-Laws Committee:
Jeff Freymueller (USA)x IUGG Capacity Building and Education Committee:
Bernhard Heck (Germany)x IUGG Visioning Committee
Chros Rizos (Australia), Chair

Other Bodies
x ABLOS (Advisory Board on the Law of the Sea):
Niels Andersen (Sweden), Juan Carlos Baez (Chile),
Sunil Bisnath (Canada), Sobar Sutisna (Indonesia)
x GEO (Group on Earth Observation):- Plenary: Hansjörg Kutterer (Germany)- Representatives to Committees nominated by GGOS
x IAU Commission A2 Rotation of the Earth:
Z. Malkin (Russia)
x ISO International Standards Organization- TC211 Geographic Information/Geomatics:
Hermann Drewes (Germany), NN- Control Body for Geodetic Registry Network:
Michael Craymer (Canada)x JBGIS (Joint Board of Geospatial Information Societies):
Chris Rizos (Australia), Hermann Drewes (Germany)x SIRGAS (Geocentric Reference System for the Americas):
Hermann Drewes (Germany)x UNOOSA (United Nations Offices for Outer Space
Affairs, UNOOSA):- International Committee on Global Navigation
Satellite Systems (ICG): Ruth Neilan (USA)- Committee on the Peaceful Use of Outer Space(COPUOS), nominated by GGOS
- United Nations Platform for Space-based Information
for Disaster Management and Emergency Response(UN-SPIDER) nominated by GGOS
x UN-GGIM (United Nations Global Geospatial
Information Management): H. Schuh (Germany)
Open Access This article is distributed under the terms of the Creative
Commons Attribution 4.0 International License (http://creativecommons.
org/licenses/by/4.0/), which permits unrestricted use, distribution, andreproduction in any medium, provided you give appropriate credit to theoriginal author(s) and the source, provide a link to the Creative Commonslicense, and indicate if changes were made.