2013 TECHNICAL REPORTEDITORS
Rolf Dach
Yoomin Jean
astRonomical instituteuniveRsitY of BeRn

Technical Report 2013
IGS Central Bureau
http://www.igs.org

Editors: R. Dach, Y. Jean
Astronomical Institute, University of Bern
Published in May 2014

IGS Central Bureau
Jet Propulsion Laboratory, M/S 238–540
4800 Oak Grove Drive
Pasadena, CA 91109–8099 USA
Tel: +1 − 818 − 354 − 2077
Fax: +1 − 818 − 393 − 6686
E–mail: cb@igs.org
Website: http://www.igs.org

National Aeronautics and Space Administration
Jet Propulsion Laboratory
California Institute of Technology
Pasadena, California, USA

International GNSS Service

International Association of Geodesy
International Union of Geodesy and Geophysics

Astronomical Institute, University of Bern
Bern, Switzerland
Compiled in April 2014, by Rolf Dach, Yoomin Jean (Eds.)

Abstract
Applications of the Global Navigation Satellite Systems (GNSS) to Earth Sciences are
numerous. The International GNSS Service (IGS), a federation of government agencies,
universities and research institutions, plays an increasingly critical role in support of
GNSS–related research and engineering activities. This Technical Report 2013 includes
contributions from the IGS Governing Board, the Central Bureau, Analysis Centers,
Data Centers, station and network operators, working groups, pilot projects, and others
highlighting status and important activities, changes and results that took place andwere achieved during 2013.
This report is available online as PDF version at
ftp://igs.org/pub/resource/pubs/2013_techreport.pdf.
The IGS wants to thank all contributing institutions operating network
stations, data centers or analysis centers or supporting the IGS in any otherform. All contributions are welcome. They guarantee the success of the IGS
also in future.

Contents
I

Executive Groups

1

Governing Board

3

U. Hugentobler

II

Central Bureau
R. Neilan, S. Fisher, R. Khachikyan, A. Craddock, D. Maggert, andG. Walia

11

Analysis Centers

19

Analysis Center Coordinator
No report submitted
Center for Orbit Determination in Europe (CODE)

21

R. Dach, S. Schaer, S. Lutz, C. Baumann, H. Bock, E. Orliac, L. Prange,
D. Thaller, L. Mervart, A. Jäggi, G. Beutler, E. Brockmann, D. Ineichen,
A. Wiget, G. Weber, H. Habrich, W. Söhne, J. Ihde, P. Steigenberger, andU. Hugentobler
Natural Resources Canada (NRCan)

35

Y. Mireault, R. Ghoddousi–Fard, B. Donahue, and F. Lahaye
European Space Agency/European Space Operations Center (ESA/ESOC)

41

T. A. Springer, L. Agrotis, J. Feltens, M. van Kints, N. Romero, F. Dilssner,
C. Flohrer, W. Enderle, E. Schoenemann, and R. Zandbergen
GeoForschungsZentrum (GFZ)

51

G. Gendt, Z. Deng, M. Ge, T. Nischan, M. Uhlemann, G. Beeskow,
A. Brandt, and M. Bradkev

Contents
Geodetic Observatory Pecný (GOP)

65

J. Dousa and P. Vaclavovic
Centre National d’Etudes Spatiales/Collecte Localisation Satellites (CNES/CLS)

72

S. Loyer, F. Perosanz, F. Mercier, H. Capdeville, A. Mezerette, and J.–
C. Marty
Jet Propulsion Laboratory (JPL)77

S. Desai, W. Bertiger, B. Haines, D. Kuang, C. Selle, A. Sibois,
A. Sibthorpe, and J. Weiss
Massachusetts Institute of Technology (MIT)No report submitted
National Geodetic Survey (NGS)No report submitted
Scripps Institution of Oceanography (SIO)
No report submitted
United States Naval Observatory (USNO)

81

C. Hackman, S. M. Byram, V. J. Slabinski, J. Tracey , and J. R. Rohde
University of Wuhan (WHU)
No report submitted
EUREF Permanent Network (EPN)89

C. Bruyninx, E. Brockmann, H. Habrich, A. Kenyeres, W. Söhne, G. Stangl,
K. Szafranek, and C. Völksen
SIRGAS

103

L. Sánchez

III Data Centers
Infrastructure Committee
I. Romero

vi

115
117

Contents
Crustal Dynamics Data Information System (CDDIS)

121

C. Noll
Scripps Institution of Oceanography (SIO)
No report submitted
Institut National de l’Information Géographique et Forestière (IGN)
No report submitted
Korean Astronomy and Space Science Institute (KASI)No report submitted

IV Working Groups, Pilot Projects
Antenna Working Group

131
133

R. Schmid
Bias and Calibration Working Group137

S. Schaer
Clock Products Working GroupNo report submitted
Data Center Working Group144

C. Noll
Ionosphere Working Group147

A. Krankowski, Y. Cherniak, and I. Zakharenkova
Multi–GNSS Working Group

153

O. Montenbruck
Space Vehicle Orbit Dynamics Working GroupNo report submittedvii

Contents
Real–Time Pilot ProjectNo report submitted
Reference Frame Working Group165

P. Rebischung, B. Garayt, X. Collilieux, and Z. Altamimi
RINEX Working Group173

K. MacLeod, L. Agrotis, and R.Dach
Tide Gauge Benchmark Monitoring Project

177

T. Schöne, R. Bingley, Z. Deng, J. Griffiths, H. Habrich, A. Hunegnaw, M. Jia, M. King, M. Merrifield, G. Mitchum, R. Neilan, C. Noll,
E. Prouteau, L. Sánchez, N. Teferle, D. Thaller, P. Tregoning, G. Wöppelmann, and P. Woodworth
Troposphere Working Group
C. Hackman and S. Byram

viii

183

Part I

Executive Groups

1

The Development of the IGS in 2013
– The Governing Board’s Perspective
Urs Hugentobler
Technische Universität München, Munich, Germany

1 Introduction
Since nearly 20 years the IGS provides the highest quality and openly available GNSS
data, products and services for a large variety of applications that benefit the scientificcommunity and society. This is possible with the strong support of more than 240 institutions and organizations worldwide and a large number of individuals devoting theirexpertise and valuable time to the IGS. The Governing Board discusses the activitiesof the various IGS components, sets policies and monitors the progress with respect tothe agreed strategic plan using newly developed tools. The work is however done within
the components. In the following sections, highlights and core activities as well as GB
activities are presented.

2 IGS Highlights in 2013
A milestone in 2013 was the launch of the IGS Real-Time Service on April 1st, 2013.
Already a few minutes after the official announcement by IGS-Mail the first users registeredat the IGS CB caster. By the end of the year the number of new users grew to about
550. Since its launch the Service, under the coordination of Loukis Agrotis (ESA/ESOC),
provided three streams of orbit and clock products with a remarkable availability of 99.7%.
Significant progress has also been registered by the GB with respect to the other IGS key
project Ű the Multi-GNSS Experiment (MGEX). The MGEX network grew to some 100
multi-GNSS stations by the end of the year, tracking data is stored in a campaign directoryat the global Data Centers, and five Analysis Centers are providing regular or occasional
orbit and clock products.
A large effort was invested into the second reprocessing activity by the Analysis Centers,
the Analysis Center Coordinator, and the Reference Frame Coordinator. Standards were
defined, software packages updated in order to reanalyze 20 years of IGS tracking data

3

IGS Gorverning Board
with the most up-to-date models and the highest consistency. Considerable effort was also
spent by the IGS CB, with essential contributions from UNAVCO, for the developmentof the new IGS web site and the Site Log Manager. Both were under beta-testing by
the end of the year and soon ready to be launched. Finally, preparations started for the
IGS Anniversary Workshop that will be held on June 23-27, 2014, in Pasadena. Rolf
Dach (AIUB) as the chair of the Scientific Organizing Committee, together with Shailen
Desai (JPL) and Andrzej Krankowski (UWM) developed an exciting draft program, while
Allison Craddock and the IGS CB are coordinating the local facilities.
Not always in the primary focus but indeed essential for the IGS are all the operational
activities, including the maintenance of the tracking network by the station operatorswith the support of the Network Coordinator, the data holding for free access at the Data
Centers, the data analysis and operational preparation of highest precision products at
the Analysis Centers, the coordination and supervision of the activities by the Product
Coordinators, and finally the work contributed by the Working Groups focusing on various
topics of relevance for the IGS, and the Central Bureau assuming responsibility for thegeneral management and day-to-day operations of the IGS. Of considerable importancefor the governance of the IGS is strategic planning and monitoring of the activities withrespect to the Strategic Plan with the use of new monitoring tools. Finally, activities also
include fostering of links with GGOS and ohter organizations, as well as the presentationof IGS activities and strategy at a number of workshops and conferences. Last but notleast: We have a new IGS logo!

3 IGS Real–Time Service
The IGS Real-time Service (RTS) was launched on April 1st, 2013, after a big effort overmany years. Significant developments were required in order to reach this milestone. A
global real-time tracking network needed to be put in place, including configuration andmanagement of communications and data distribution; algorithms needed to be developed;
products to be generated; combined and validated; and the necessary standards and realtime formats and protocols needed to be developed. The effort was led by the RealTime WG with Mark Caissy (NRCan) as the Chair and Loukis Agrotis (ESA/ESOC)
as the Analysis Coordinator. At the time of the successful launch of the RTS, threeorbit and clock product streams were provided based on real-time data from some 150
globally distributed stations processed by eight Analysis Centers. Throughout the year
the RTS had a remarkable performance with an availability of 99.7% demonstrating thatthe redundancy concept being used was indeed very robust. Since the start of the RTS
until end of the year about 270 registered at the CB caster and 280 registered at the BKG
caster, in addition to the 2191 users already registered at the BKG server since 2008.

4

5 Governing Board Meetings in 2013

4 Strategic planning
The Central Bureau under the lead of Steve Fisher collected a wealth of information in theform of Key Performance Indicators (KPI) that could be used to monitor the performanceof the IGS according to our new strategic planning process. These KPI document that
the IGS made progress with respect to all objectives listed in the Strategic Plan 20132016. The monitoring tools proved to be very valuable, and allow the GB to obtaina comprehensive overview of the actual IGS performance with respect to the Strategic
Plan. As only one interesting result, the in-kind contribution received from the about 240
organizations and institutions contributing to the IGS was conservatively estimated as 10
Mio US$ per year. Some of the objectives in the Strategic Plan, in particular related tomaintenance and diversification of funding sources require additional effort. Based on the
input by the different components of the IGS the Strategic Implementation Plan for 2014
was established.
In 2013 the Call for Proposals for a new Analysis Center Coordinator was issued. An early
identification of the next ACC allows for a smooth transition until the end of 2015, when
the term of NGS hosting this important function since 2008 comes to an end.
In time for the 20th anniversary of the IGS our new logo was approved by the Board at its
December meeting. The logo was designed by Prim Prim Studio, a small design company
from Lithuania, and with the strong engagement of Allison Craddock from the IGS CB.
The distinctive logo has the appearance of a stylized navigation satellite and is thus very
appropriate. It will become associated with the IGS over the coming decade.

5 Governing Board Meetings in 2013
The IGS Governing Board met three times in 2013. GB business meetings took place
on April 7th during the EGU General Assembly in Vienna and on September 4th during
the IAG Scientific Assembly. The regular end-of-year meeting took place on December
8 during the AGU Fall Meeting in San Francisco. The IGS Executive Committee Ű
consisting of Urs Hugentobler, Chuck Meertens, Ruth Neilan, Chris Rizos, Tim Springer
and with regular participation of Steve Fisher, Allison Craddock, and of WG Chairs as
required Ű has met eight times in 2013 by teleconference.
A summary of the GB meeting in December 2013 may be found in IGS Mail 6849. Tab. 1
lists the important events in 2013.

5

IGS Gorverning Board
Table 1: IGS events in 2013
April 1
April 7
September 4
December 3
December 8

Launch of IGS Real–Time Service
GB Business Meeting in Vienna (EGU)
GB Business Meeting in Potsdam (IAG Scientific Assembly)
Issue of Request for Proposals for the next ACC
42nd GB Meeting in San Francisco (AGU)– Fran Boler elected as Data Center Representative– Laura Sanchez elected as Network Representative– Gary Johnston appointed GB member– Satoshi Kogure appointed GB member– Michael Coleman assigned as new Clock Product Coordinator– new IGS logo approved

6 Governing Board Membership
A significant change in the GB membership took place in 2013. Two positions were up
for election, namely a Data Center Representative and a Network Representative as theterms of Cary Noll and Gary Johnston ended at the end of 2013. Five candidates agreed
to stand in the election, which was organized by an Election Committee consisting of
Chuck Meertens (Chair), Carey Noll, and Ralf Schmid. The candidates were Fran Boler,
Ludwig Combrinck and Jong Uk (James) Park as Data Center Representatives, and LauraSánchez and Graeme Blick as Network Representatives. All candidates received strong
support from the Associate Members. As a result of the election Laura Sánchez (DGFI)
was elected as Network Representative and Fran Boler (UNAVCO) was elected as Data
Center Representative.
The Board is pleased that both Carey Noll (GSFC) and Gary Johnston (GA) continue
serving as GB members, Carey Noll as Chair of the Data Center WG and Gary Johnston
as a new appointed member. At the meeting Satoshi Kogure from Japan Aerospace
Exploration Agency (JAXA) was also appointed to the GB. Although not representing
his agency, Satoshi is very involved in QZSS and in the Asia Pacific multi-GNSS activities,
as well as in the International Committee on GNSS (ICG) and thus complements the IGS
GB with extensive expertise. The terms of appointed GB members Richard Wonnacott
and James Park ended at the close of 2013. The GB thanks both of them for theircontributions at many GB meetings over the years.
At the end of 2013 Ken Senior (NRL) stepped down as Clock Product Coordinator after
many years. Ken started his work as Clock Products Coordinator and WG Chair in
2003 and since then significantly enhanced the performance of the IGS Rapid and Finaltimescales. At the GB meeting in December the Board approved Michael Coleman (NRL)
as new Clock Products Coordinator. Mark Caissy (NRCan) stepped down as RT WG
Chair at the end of 2013. Over the last ten years he was the driver for our newest
product, the IGS Real-Time Service. With much enthusiasm he pushed the undertaking

67 Outreachforward and brought it to a successful launch.
The terms of Bruno Garayt (IGN) as the Reference Frame Coordinator as well as of Nacho
Romero (ESA/ESOC) as the Chair of the Infrastructure Committee drew to a close by theend of 2013. IGN as well as ESA/ESOC renewed their support and the Board unanimously
agreed that Bruno Garayt and Nacho Romero continue their important functions for afurther term of four years.
Several Working Group Chairs were routinely up for renewal, namely Christine Hackman(USNO), Chair of the Troposphere WG; Carey Noll (NASA/GSFC), Chair of the Data
Center WG; and Ken Mac Leod (NRCan), Chair of the RINEX WG. All three are readyto continue their work for the IGS and have the support of their respective institutions.
The GB unanimously renewed their terms based on their contributions Ű well documented
in the respective components reports.
Tab. 2 lists the members of the IGS Governing Board for 2013.

7 Outreach
The IGS is well represented on the GGOS Coordinating Board. It plays a leadership rolein the International Committee on GNSS (ICG), in particular by co-chairing Working
Group D on Reference Frames, Timing and Applications, and the International GNSS
Monitoring and Assessment (IGMA) Subgroup within ICG Working Group A. In theseroles the IGS participated in the ICG-8 meeting in November in Dubai. The IGS is also
well-represented in the International Earth Rotation & Reference Systems Service (IERS)
and in IAG Sub-Commission 1.2 on reference frames, in the RTCM SC104, and others.
IGS has been engaged in many outreach activities in 2013. The following list is a selectionof presentations at international meetings and articles in geospatial magazines. As inprevious years the IGS was also given visibility as session organizers of, or presenters in,
IGS-related sessions at conferences such as those of the EGU in Vienna, the IAG Scientific
Assembly in Potsdam, and AGU in San Francisco.
Selection of presentations at international meetings:• European Geosciences Union General Assembly 2013, April 10, Vienna, Steigenberger, "Status and Perspective of the IGS Multi-GNSS Experiment (MGEX)"• U.S. Institute of Navigation Pacific PNT Symposium, April 22-25, Honolulu, Hawaii,
Rizos, "The IGS MGEX Experiment as a Milestone for a Comprehensive MultiGNSS Service"• 4th Chinese Satellite Navigation Conference, May 15, Wuhan, China, Hugentobler,"International GNSS Service - New Products for Real-Time Applications"• EUREF Symposium 2013, May 29, Budapest, Hungary, Hugentobler, "Real-Time
7

IGS Gorverning Board
and Multi-GNSS - Key Projects of the International GNSS Service"• Hexagon International Conference, June 3-6, Las Vegas, Nevada, Rizos, "The International GNSS Service (IGS) in a Multi GNSS World"• IGNSS 2013, July 18, Surfers Paradise, Australia, Montenbruck, "The Multi-GNSS
Experiment of the International GNSS Service"• 4th International Colloquium Scientific and Fundamental Aspects of the Galileo Programme, December 12, Prague, Czech Republic, Montenbruck "IGS-MGEX: Preparing the Ground for Multi-Constellation GNSS Science"
Selection of articles:• Montenbruck, O., Steigenberger, P., Khachikyan, R., Weber, R., Langley, R.B., Mervart, L., Hugentobler, U.: “IGS–MGEX: Preparing the Ground for Multi–Constellation
GNSS Science”, in Proceedings of the 4th International Colloquium Scientific andFundamental Aspects of the Galileo Programme.
• Montenbruck, O., Rizos, C., Weber, R., Weber, G., Neilan, R., Hugentobler, U.:
Getting a Grip on Multi–GNSS, The International GNSS Service Multi GNSS Campaign; GPS World, Vol. 24, Nr. 7.
• Rizos, C., “Multi–GNSS: Now and in the Future”, Coordinates Vol. IX, Sept. 2013
• Springer, T., “Multi–GNSS Monitoring”, Inside GNSS, Nov./Dec. 2013
Reports, Brochures, Flyers:• IGS Strategic Plan 2013–2016• IGS Progress Report 2008–2012• IGS Overall Brochure• IGS Quality of Service Fact Sheet• IGS Real–Time Service Fact Sheet

8 Outlook
The year 2014 already promises the next highlight, our Anniversary Workshop on June
22-27 at JPL in Pasadena, CA, celebrating 20 years of service. We are all looking forward
to this important event. In 2014 we will also see the launch of a new IGS website and Site
Log Manager. Rapid progress is expected in the Multi-GNSS Experiment as it prepares
the IGS for a seamless integration of the new and upcoming GNSS constellations into its
processing streams and products. To accomplish our goals we seek the support of newgroups willing to contribute to this effort. Preparations for launching Full Operational

88 Outlook
Capability in the Real-Time Service are underway. The reprocessing campaign will beterminated providing to the users and to ITRF2013 consistent IGS products covering 20
years and adhering to the most up-to-date models and standards.
The IGS GB thanks all participants and supporters of the IGS for their efforts invested
in the past year. Only with the continuous efforts of the network operators, operators ofdata centers and analysis centers, the product coordinators, WG, PP and committee chairs
and members, the Central Bureau, and the continuous support by numerous institutions
worldwide the IGS is able to serve a large user community with the provision of the highest
quality GNSS products.

9

IGS Gorverning Board
Table 2: IGS Governing Board Members 2013 (*: voting members, EC: Executive Committee)
MemberInstitution

Country

FunctionUrs Hugentobler (EC)*

Technische Universität München

Germany

Zuheir Altamimi*

Institut National de l’Information
Géographique et Forestière
Bureau International desPoids et Mesures
Institut National de l’Information
Géographique et Forestière
Royal Observatory of Belgium
Natural Resources Canada
Chinese Academy of Surveying and
Mapping
Jet Propulsion Laboratory

FranceBoard Chair, Analysis Center
Representative
IAG Representative

Felicitas Arias
Claude Boucher*Carine Bruyninx*
Mark Caissy
Yamin Dang*
Shailen Desai*
Steve Fisher
Bruno Garayt*

Jake Griffiths*
Christine Hackman
Gary Johnston*Andrzej Krankowski
Ken MacLeod
Chuck Meertens*
Oliver Montenbruck
Ruth Neilan (EC)*
Carey Noll*
James Park*
Chris Rizos (EC)*Ignacio Romero
Stefan Schaer
Ralf Schmid
Tilo Schöne
Ken Senior*
Tim Springer (EC)*

Richard Wonnacott*Marek Ziebart

10FranceFranceBIPM/CCTF
Representative
IERS Representative

Belgium
CanadaChina

Network Representative
Real–Time WG Chair
Appointed

USA

Analysis Center
Representative
IGS Secretariat

IGS Central Bureau, Jet Propulsion
Laboratory
Institut National de l’Information
Géographique et Forestière

USA

NOAA, National Geodetic Survey
United States Naval Observatory
Geoscience Australia
University of Warmia and Mazury
in Olsztyn
Natural Resources Canada

USA
USA
Australia
PolandUNAVCODLR/German Space Operations
CenterIGS Central Bureau, Jet Propulsion
Laboratory
Goddard Space Flight Center

USA
Germany

Korean Astronomy and Space Science
Institute
University of New South WalesSouth Korea

ESA/European Space Operations
CentreFederal Office of Topography

Germany

Deutsches Geodätisches
Forschungsinstitut
Deutsches GeoForschungs–Zentrum
PotsdamNaval Research Laboratory
ESA/European Space Operations
CentreGermany

President of IAG
since July 2011
(before: appointed)
Infrastructure Committee
Chair
Bias and Calibration
WG ChairAntenna WG Chair

Germany

TIGA WG Chair

USA
Germany

Chief Directorate:
National Geo–spatial Information
UniversityCollegeLondon

South Africa

Clock Product Coordinator
Analysis Center
Representative,
IGS Representative to IERS,
Chair of Associate Members
Committee
Appointed

FranceCanadaUSA
USA

Australia

Switzerland

UK

Reference Frame
Coordinator,
IGS Representative to
IAG Sub–commission 1.2
Analysis Center Coordinator
Troposphere WG Chair
Network Representative
Ionosphere WG Chair
IGS/RTCM RINEX WG
Chair
Appointed
Multi–GNSS WG Chair
Director of IGS Central
Bureau, Secretary
Data Center Representative,
Data Center WG Chair
Appointed

Space Vehicle Orbit
Dynamics WG ChairIGS Technical Report 2013
Central Bureau
R. Neilan1 , S. Fisher1 , R. Khachikyan2 ,A. Craddock3 , D. Maggert4 , and G. Walia1
12
34NASA/Jet Propulsion Laboratory, Caltech, Pasadena, California
Raytheon, Inc., Pasadena, California
SBAR, Inc., Pasadena, California
UNAVCO, Inc., Boulder, Colorado

1 Introduction
The IGS Central Bureau (CB) is hosted at the California Institute of Technology/Jet
Propulsion Laboratory and is funded by NASA. The Central Bureau supports IGS management focusing on two principal functions: 1) executive management of the service,including international coordination and outreach, and 2) coordination of IGS infrastructure, including the IGS tracking network and information management systems. Specific responsibilities of the Central Bureau are outlined in the IGS Terms of Reference:
http://igs.org/organization/orgindex.html. Accomplishments during 2013, as well
as plans for 2014, are outlined within this report.

2 Executive Management• Developed 2013–2016 Strategic Plan and monitoring progress.

• Supported 2013 Associate Member selection and Governing Board election.

• Supported Governing Board meetings in Vienna, Potsdam and San Francisco.

• Supported Executive Committee activities and teleconferences approximately every
other month.
• Supported IAG 150th Anniversary meetings and activities.
• Local coordination of 2014 IGS workshop was initiated.

11

IGS Central Bureau• Compiled official service reports for IERS and IAG.

• Terms of Reference were reviewed resulting in a number of proposed changes presented to the Governing Board.

3 Project Support, Committee and Working Group
Participation• Supporting key activities in all areas.

• Supporting Real–time Service launch. Operate RTS product distribution center andwebsite, support RTS user registrations, user support.
• Supporting M–GEX and outreach efforts with Multi–GNSS.

• Supporting development of multi–GNSS monitoring capabilities through the International Committee on GNSS (ICG).
• Supporting Infrastructure Committee activities.

• Participating on Antenna, RINEX, Reference Frame Working Groups.

4 Develop Funding• Significant coordination of Space Geodetic Program for NASA funding of CB.

• Development of overall strategic goals and monitoring of Key Performance Indicators(KPI) strongly relates to funding development for entire IGS.
• The IGS Institute business plan was drafted and presented to the Governing Board
at the December meeting.
• An Industry sponsor program was drafted to develop sponsors to support 2014 Workshop and other activities.

5 Monitor progress on Strategic Plan
• The annual Component Report template was modified to collect progress information.
• An end of year progress assessment was completed. A dashboard of Key Performance
Indicators is being developed and will be posted on the IGS website in early 2014.

12

7 Network Infrastructure and Information• Working groups were requested to self assess the impacts of their groups on strategic
goals as part of the year–end progress assessment.
• A target service performance specification has been drafted. Monitoring data is
included in the KPI dashboard.

6 Website/Marketing Communications• A new IGS logo was developed and approved by the Governing Board.

• The first phase of website modernization was almost completed at year–end. Features include: modern content management system improves maintainability, web
2.0 features built–in, simplified navigation, new logo and branding, hosted externalfrom JPL to allow unrestricted global access, bibliography, knowledgebase, search,
video section, and social media integration.
• Next phase development will facilitate third party content management for the Working Groups.
• All IGS brochures and distribution materials have been updated.

7 Network Infrastructure and Information• Site Log Manager (SLM) database application was released in Beta.

• An improved network page with extended metrics is published on website:
http://igs.org/network/network.php• Coordinating with IC to address various network issues.

• Better defining/streamlining procedures for accepting new stations into the IGS.

• UNAVCO resources have been fully integrated into station management and user
support function.
• Finalized and published the IGS Site Guidelines.

• CB caster (http://rt.igs.org) is hosting the IGS combination streams IGS01,
IGS02, IGS03, and RTCM3EPH01.
• CB caster (http://rt.igs.org) is accepting approximately 115 streams from station providers where about 75% of are typically transmitting data.
• Deleted 14 decommissioned stations from the network.

• Automated the process of updating the igs08.atx to allow Antenna Working Group
13

IGS Central Bureau
Chair to publish the standard w/o any delay.
• Changed the CMP designation to BDS throughout the IGS network and the products
generated from the CB.
• Added 71 equipments to the rcvr_ant.tab and their available sketches with their
ARP definitions in the antenna.gra.
• Supported MGEX to grow to 98 stations.

• Accepted the following stations to IGS Network:
AREV – Arequipa, Peru

BNOA – Benoa, Indonesia
BSHM – Haifa, Israel
BTNG – Bitung, Indonesia
CKIS – Rarotonga, Cook Islands
DYNG – Dionysos, Greece
FTNA – Maopo’opo, Wallis and Futuna
KOUG – Kourou, France (French Guiana)
MOIU – Eldoret, Kenya
PALV – Palmer Station, Antarctica
WARK – Warkworth, New Zealand

8 User support• Knowledgebase system has been implemented at CB.

• The CB user support burden has been compounded principally by introduction of
the Real–time Service (RTS), and also by the Multi–GNSS project.
• CB Mails numbered 2,915 in 2013 (2,801 in 2012).

• Formal trouble ticketing and resolution application are being investigated as needs
grow.

9 Meetings/Outreach
The following meetings that relate to IGS were supported by the CB in 2013.

14

9 Meetings/Outreach

Table 1: CB meetings in 2013
Date

Location

Meeting

December 2013

San Francisco, CA

December 2013
November 2013

Washington DC
Dubai, UAE

September 2013

Pasadena, CA

September 2013

Tokyo, Japan

September 2013

Nashville, TN

August 2013

Potsdam, Germany

July 2013

Cambridge, UK

May 2013
April 2013

Washington DC
Paris, France

April 2013

Vienna, Austria

March 2013

Langley, Virginia

February 2013

Vienna, Austria

January 2013

San Diego, CA

IGS Governing Board meeting and related meetings,
GGOS GB, GIAC, BNC Meetings
PNT Advisory Panel meeting
8th Meeting of the International Committee
on Global Navigation Satellite Systems (ICG)
WG on Reference Frames, Timing and Applications
International GNSS Monitoring and Assessment(IGMA)CEOS SIT Technical Workshop– local organization supported by GGOS/IGS
Remote attendance of World Data System ScientificCommittee Meeting
Programmatic meetings on GNSS monitoring and
IGS real–time services in conjunction with ION
IAG General Assembly, IGS Governing Boardand related meetings
Cambridge Summit and UN Global Geospatial
Information Management (UN GGIM)PNT Advisory Panel Meeting
8th Meeting of Scientific Committee of the World
Data Systems
Remotely organized and attended programmatic
meetings organized around EGU (GB, GGOS, etc.)
28th Meeting of CEOS Strategic ImplementationTeam
UNOOSA committee meeting on the Peaceful Useof Outer SpaceION International Technical Meeting
RTCM Committee Meeting

15

IGS Central Bureau

10 Policy Interactions
The Central Bureau has supported a number of policy interactions on behalf of IGS in
2013.
• NASA policy participation.
• UN–ICG participation.

• UN–GGIM GGRF WG participation.
• WDS participation.

• Many interactions through GGOS and GIAC.

11 Standards Supported
The Central Bureau has supported development/maintenance of a number of important
standards activities affecting IGS in 2013.
• Support IC in site and networks standards.

• Support Antenna Working Group in maintaining IGS antenna files.
• Support RINEX WG.

• Support RTS interests in RTCM SC–104.

• Interchangeability/interoperability monitoring Standard supported through ICG.

12 Publications• 2013–2016 IGS Strategic Plan

• 2008–2012 IGS Progress Report• 2012 IGS Technical Report section• 2012 IERS Annual Report• 2011–2013 IAG Mid–term Report16

13 Plan for 201413 Plan for 2014
• Executive Support: Continue fulfilling the IGS executive responsibilities resulting in
effective management and governance of the service. Provide local organization to
20th anniversary Workshop.
• Project Support, Committee and Working Group Participation: Continue supporting all WG activities. Emphasis on achieving RTS FOC.
• Develop funding: Develop industry sponsor program. Evaluate ways to recover costof operating service.
• Monitor progress on Strategic Plan: Update IGS dashboard at least once during
year.
• Website/Marketing and Communications: Phase II website development – improve
content, add 3rd party development workflows for WGs.
• Coordinate network infrastructure and information: finalize SLM, convert selected
RTS stations to full IGS stations.
• Service Performance Targets: Continue monitoring defined service availability.

• User support: Improve efficiency in handling many user support requests by implementing the Site Log Manager application (SLM), a web based Knowledge Base
(KB), and trouble ticketing technologies.
• Outreach: Emphasis on IGMA and UN–GGRF–WG activities.

• Refine the network with more robust stations in key areas providing more GNSS
coverage.

17

IGS Central Bureau

18

Part II

Analysis Centers

19

Center for Orbit Determination in Europe (CODE)
R. Dach1 , S. Schaer2
S. Lutz1 , C. Baumann1 , H. Bock1 , E. Orliac1 , L. Prange1 ,D. Thaller1,3 , L. Mervarta , A. Jäggi1 , G. Beutler1
E. Brockmann2 , D. Ineichen2 , A. Wiget2
G. Weber3 , H. Habrich3 , W. Söhne3 , J. Ihde3
P. Steigenberger4 , and U. Hugentobler4
12
34

Astronomical Institute, University of Bern, Bern, Switzerland
E–mail: code@aiub.unibe.ch
Federal Office of Topography swisstopo, Wabern, Switzerland
Federal Agency of Cartography and Geodesy,Frankfurt a. M., Germany
Institut für Astronomische und Physikalische Geodäsie,Technische Universität München, Munich, Germany

1 The CODE consortium
CODE, the Center for Orbit Determination in Europe, is a joint venture of the following
four institutions:• Astronomical Institute, University of Bern (AIUB), Bern, Switzerland,• Federal Office of Topography swisstopo, Wabern, Switzerland,• Federal Agency of Cartography and Geodesy (BKG), Frankfurt a. M., Germany, and• Institut für Astronomische und Physikalische Geodäsie, Technische Universität
München (IAPG, TUM), Munich, Germany.
The operational computations are performed at AIUB whereas reprocessing activities areusually carried out at IAPG, TUM. All solutions and products are produced with thelatest development version of the Bernese GNSS Software (Dach et al. 2007).
aInstitute of Geodesy, Czech Technical University in Prague, Czech Republic

21

Dach, Schaer et al.: Center for Orbit Determination in Europe

2 CODE products available to the public
A wide variety of GNSS solutions based on a rigorously combined GPS/GLONASS dataprocessing scheme is computed at CODE. The products are made available through anonymous ftp:
ftp://ftp.unibe.ch/aiub/CODE/ or http://www.aiub.unibe.ch/download/CODE/
An overview of the files is given in Tab. 1.
In the table the following abbreviations are used:yyyy Year (four digits)
ddd
Day of Year (DOY) (three digits)yyYear (two digits)
wwww
GPS Week
yymm Year, Monthwwwwd GPS Week and Day of week
Table 1: CODE products available through anonymous ftp.
CODE final products available at ftp://ftp.unibe.ch/aiub/CODE/yyyy/
yyyy/CODwwwwd.EPH.Z
yyyy/CODwwwwd.ERP.Z
yyyy/CODwwwwd.CLK.Z
yyyy/CODwwwwd.CLK_05S.Z
yyyy/CODwwwwd.SNX.Z
yyyy/CODwwwwd.TRO.Z
yyyy/CODGddd0.yyI.Z
yyyy/CODwwwwd.ION.Z
yyyy/CODwwww7.SNX.Z
yyyy/CODwwww7.SUM.Z
yyyy/CODwwww7.ERP.Z
yyyy/COXwwwwd.EPH.Z
yyyy/COXwwww7.SUM.Z
yyyy/CGIMddd0.yyN.Z
yyyy/P1C1yymm.DCB.Z
yyyy/P1P2yymm.DCB.Z
yyyy/P1P2yymm_ALL.DCB.Z
yyyy/P1C1yymm_RINEX.DCB
yyyy/P2C2yymm_RINEX.DCB

22

CODE final GNSS orbits
CODE final ERPs belonging to the final orbits
CODE final clock product, clock RINEX format, with a sampling of
30 sec for the satellite and reference (station) clock corrections and5 minutes for all other station clock corrections
CODE final clock product, clock RINEX format, with a sampling of
5 sec for the satellite and reference (station) clock corrections and5 minutes for all other station clock corrections
CODE daily final solution, SINEX format
CODE final troposphere product, troposphere SINEX format
CODE final ionosphere product, IONEX format
CODE final ionosphere product, Bernese format
CODE weekly final solution, SINEX format
CODE weekly summary file
Collection of the 7 daily CODE-ERP solutions of the week
CODE final GLONASS orbits (for GPS weeks 0990 to 1066;
27-Dec-1998 to 17-Jun-2000)
CODE weekly summary files of GLONASS analysis
Improved Klobuchar–style ionosphere coefficients, navigation RINEX
formatCODE monthly P1−C1 DCB solution, Bernese format,
containing only the GPS satellites
CODE monthly P1−P2 DCB solution, Bernese format,
containing all GPS and GLONASS satellites
CODE monthly P1−P2 DCB solution, Bernese format,
containing all GPS and GLONASS satellites and all stations used
CODE monthly P1−C1 DCB values directly extracted from RINEX
observation files, Bernese format, containing the GPS and GLONASS
satellites and all stations used
CODE monthly P2−C2 DCB values directly extracted from RINEX
observation files, Bernese format, containing the GPS and GLONASS
satellites and all stations used

2 CODE products available to the public
Table 1: CODE products available through anonymous ftp (cont).
CODE ultra–rapid products available at ftp://ftp.unibe.ch/aiub/CODE
COD.EPH_U
COD.ERP_U
COD.TRO_U
COD.SUM_U
COD.ION_U
COD.EPH_5D

CODE ultra–rapid GNSS orbits
CODE ultra–rapid ERPs belonging to the ultra–rapid orbit product
CODE ultra–rapid troposphere product, troposphere SINEX format
Summary of stations used for the latest ultra–rapid orbit
Last update of CODE rapid ionosphere product (1 day) complemented with
ionosphere predictions (2 days)
Last update of CODE 5–day orbit predictions, from rapid analysis, including all
active GLONASS satellites

CODE rapid products available at ftp://ftp.unibe.ch/aiub/CODE
CODwwwwd.EPH_R
CODwwwwd.EPH_P
CODwwwwd.EPH_P2
CODwwwwd.EPH_5D
CODwwwwd.ERP_R
CODwwwwd.ERP_P
CODwwwwd.ERP_P2
CODwwwwd.ERP_5D
CODwwwwd.CLK_R
CODwwwwd.TRO_R
CODwwwwd.SNX_R.Z
CORGddd0.yyI
COPGddd0.yyI
CODwwwwd.ION_R
CODwwwwd.ION_P
CODwwwwd.ION_P2
CODwwwwd.ION_P5
CGIMddd0.yyN_R
CGIMddd0.yyN_P
CGIMddd0.yyN_P2
CGIMddd0.yyN_P5
P1C1.DCB
P1P2.DCB
P1P2_ALL.DCB
P1P2_GPS.DCB
P1C1_RINEX.DCB
P2C2_RINEX.DCB
CODE.DCB
CODE_FULL.DCB

CODE rapid GNSS orbits
CODE 24–hour GNSS orbit predictions
CODE 48–hour GNSS orbit predictions
CODE 5–day GNSS orbit predictions
CODE rapid ERPs belonging to the rapid orbits
CODE predicted ERPs belonging to the predicted 24–hour orbits
CODE predicted ERPs belonging to the predicted 48–hour orbits
CODE predicted ERPs belonging to the predicted 5–day orbits
CODE rapid clock product, clock RINEX format
CODE rapid troposphere product, troposphere SINEX format
CODE rapid solution, SINEX format
CODE rapid ionosphere product, IONEX format
CODE 1–day or 2–day ionosphere predictions, IONEX format
CODE rapid ionosphere product, Bernese format
CODE 1–day ionosphere predictions, Bernese format
CODE 2–day ionosphere predictions, Bernese format
CODE 5–day ionosphere predictions, Bernese format
Improved Klobuchar–style coefficients, RINEX format
1–day predictions of improved Klobuchar–style coefficients
2–day predictions of improved Klobuchar–style coefficients
5–day predictions of improved Klobuchar–style coefficients
CODE sliding 30–day P1−C1 DCB solution, Bernese format,
containing only the GPS satellites
CODE sliding 30–day P1−P2 DCB solution, Bernese format,
containing all GPS and GLONASS satellites
CODE sliding 30–day P1−P2 DCB solution, Bernese format,
containing all GPS and GLONASS satellites and all stations used
CODE sliding 30–day P1−P2 DCB solution, Bernese format,
containing only the GPS satellites
CODE sliding 30–day P1−C1 DCB values directly extracted from RINEX
observation files, Bernese format, containing the GPS and GLONASS satellites
and all stations used
CODE sliding 30–day P2−C2 DCB values directly extracted from RINEX
observation files, Bernese format, containing the GPS and GLONASS satellites
and all stations used
Combination of P1P2.DCB and P1C1.DCB
Combination of P1P2.DCB, P1C1.DCB (GPS satellites), P1C1_RINEX.DCB(GLONASS satellites), and P2C2_RINEX.DCB

Note that as soon as a final product is available the corresponding rapid, ultra–rapid, or predicted products
are removed from the anonymous FTP server.

23

Dach, Schaer et al.: Center for Orbit Determination in Europe

Table 2: CODE final products available in the product areas of the IGS data centers.
Files generated from three–day long–arc solutions:
CODwwwwd.EPH.Z
CODwwwwd.SNX.Z
CODwwwwd.CLK.Z
CODwwwwd.CLK_05S.Z
CODwwwwd.TRO.Z
CODwwww7.ERP.Z
CODwwww7.SUM

GNSS ephemeris/clock data in daily files at 15–min intervals in SP3 format,
including accuracy codes computed from a long–arc analysis
GNSS daily coordinates/ERP/GCC from the long–arc solution in SINEX
formatGPS satellite and receiver clock corrections at 30–sec intervals refering to the
COD–orbits from the long–arc analysis in clock RINEX format
GPS satellite and receiver clock corrections at 5–sec intervals refering to the
COD–orbits from the long–arc analysis in clock RINEX format
GNSS 2–hour troposphere delay estimates obtained from the long–arc
solution in troposphere SINEX format
GNSS ERP (pole, UT1−UTC) solution, collection of the 7 daily COD–ERP
solutions of the week in IGS IERS ERP format
Analysis summary for 1 week

Files generated from pure one–day solutions:
COFwwwwd.EPH.Z
COFwwwwd.SNX.Z
COFwwwwd.CLK.Z
COFwwwwd.CLK_05S.Z
COFwwwwd.TRO.Z
COFwwww7.ERP.Z
COFwwww7.SUM

GNSS ephemeris/clock data in daily files at 15–min intervals in SP3 format,
including accuracy codes computed from a pure one–day solution
GNSS daily coordinates/ERP/GCC from the pure one–day solution in
SINEX format
GPS satellite and receiver clock corrections at 30–sec intervals refering to the
COF–orbits from the pure one–day analysis in clock RINEX format
GPS satellite and receiver clock corrections at 5–sec intervals refering to the
COF–orbits from the pure one–day analysis in clock RINEX format
GNSS 2–hour troposphere delay estimates obtained from the pure one–day
solution in troposphere SINEX format
GNSS ERP (pole, UT1−UTC) solution, collection of the 7 daily COF–ERP
solutions of the week in IGS IERS ERP format
Analysis summary for 1 week

Other product files (not available at all data centers):
CODGddd0.yyI.Z
CKMGddd0.yyI.Z
GPSGddd0.yyI.Z

GNSS 2-hour global ionosphere maps in IONEX format, including satellite
and receiver P1−P2 code bias values
GNSS daily Klobuchar-style ionospheric (alpha and beta) coefficients in
IONEX format
Klobuchar-style ionospheric (alpha and beta) coefficients from GPS
navigation messages represented in IONEX format

Note that the COD–series is identical with the files posted at the CODE’s aftp server, see Tab. 1.

24

3 Changes in the daily processing for the IGS
Since GPS week 1706,
CODE has generated apure one–day solution(label “COF”) in addition to the traditional
three–day long–arc solution (label “COD”). The
result files from both series are submitted to the
IGS data centers hosting
GNSS
the products. The reGPS only
lated files are listed in
Tab. 2.
Figure 1: Network used for the GNSS final processing at CODE by
the end of 2013.

The network used by
CODE for the final processing is shown in Fig. 1. Nearly 80% of the stations support GLONASS (red stars).

3 Changes in the daily processing for the IGS
The CODE processing scheme for daily IGS analyses is constantly subject to updates andimprovements. The last technical report was published in Dach et al. (2013).
In Section 3.1 we give an overview of important development steps in the year 2013.
Section 3.2 reports on the improvements in the CODE ultra-rapid product generation andSection 3.3 provides details on the update of the final clock product computation.

3.1 Overview of changes in the processing scheme in 2013
Tab. 3 gives an overview of the major changes implemented during the year 2013. Details
on the analysis strategy can be found in the IGS analysis questionnaire at the IGS Central
Bureau (ftp://igs.org/igscb/center/analysis/code.acn).
Several other improvements not listed in Tab. 3 were implemented, too. Those mainly
concern data download and management, sophistication of CODE’s analysis strategy,
software changes (improvements), and many more. As these changes are virtually not
relevant for users of CODE products, they will not be detailed on any further.

25

Dach, Schaer et al.: Center for Orbit Determination in Europe
Table 3: Selected modifications of the CODE processing in 2013.
Date

DoY/Year

Description

27-Feb-2013

054/2013

28-Feb-2013

055/2013

09-Jun-2013

160/2013

23-Jun-2013
08-Jul-2013
11-Jul-2013
14-Jul-2013

174/2013
188/2013
192/2013
195/2013

R26 was tracked by several stations for three days (054 to 056):
25 GLONASS or 32+25=57 GNSS satellites
Daily check of GLONASS frequency channel numbers
Alarming scheme established (as soon as an anomaly gets detected for
doy -1)
If less than 10 complete RINEX files for the 5 sec clock densification areavailable (to be used as potential reference clocks) also incomplete
RINEX files (with missing epochs in the result files) are allowed to be
used as reference clock
Weekly ERP files are merged from daily results
New ERP file generation used for IGS ultra-rapid submission
New ERP file is also used for orbit prediction
Change orbit model for final product line:• change JPL Ephemeris from DE405 to DE421• enable Albedo model according to Rodriguez-Solano et al. (2012)• enable Antenna thrust (GPS: block-specific according to
http://acc.igs.org/orbits/thrust-power.txt ;GLONASS: assumed averaged value of 100 W)• disable the a priori radiation pressure model (Springer et al. 1999)
Improved observation identification allowing for potential quarter-cycle
identfication implemented for all product lines
No VMF coefficients available from TU Vienna:• 19-Jul to 28-Jul-2013 (DoY 200-209) coefficients from Universityof New Brunswick (based on NCEP) used
• 29-Jul to 02-Aug-2013 GPT/GMF used for rapid products (final
again with coefficients from Vienna)
Relocation of the University’s Linux cluster into another building;all IGS-related activities are managed on a backup system
Submission from the nominal system recovered after system tests andback-synchronisation
Make sure that accuracy code zero in precise orbit files cannot appear fora valid satellite
Accuracy code cleaned up in precise orbit files for weeks 1706 to 1756 on
CODE’s FTP server
Allow for independent reference clocks for 30 s and 5 s final clock products
Change orbit model for rapid/ultra-rapid product line:• change JPL Ephemeris from DE405 to DE421• enable Albedo model according to Rodriguez-Solano et al. (2012)• enable Antenna thrust (GPS: block-specific according to
http://acc.igs.org/orbits/thrust-power.txt ;GLONASS: assumed averaged value of 100 W)• disable the a priori radiation pressure model (Springer et al. 1999)
High-rate (30 s) clock solution uses exclusively stations from “regular”
daily RINEX archives; RINEX files from real-time streams are only used
for ultra-high-rate (5 s) clock product generation (before, real-time based
RINEX files have occasionally been used for generating the high-rate
clock product)
Allow more iterations for screening the observation file for thephase-based interpolation of the 5 min clock solutions to 30 s and 5 s
respectively
Start submitting ultra-rapid products (orbits, ERPs) generated with the
new scheme, see Section 3.2

19-Jul to 02-Aug-2013

20-Aug to 30-Aug-2013
05-Sep-2013
13-Sep-2013

256/2013

20-Sep-2013

263/2013

02-Oct-2013
01-Nov-2013

275/2013
305/2013

03-Nov-2013

307/2013

10-Nov-2013

314/2013

12-Nov-2013

316/2013

26

3 Changes in the daily processing for the IGS

3.2 Updating the CODE ultra-rapid product generation
Comparing the ultra-rapid orbits from CODE with the IGS combined product and thesolutions from other analysis centers by a 7-parameter Helmert transformation, large rotations, especially around the z-axis, were present since a long time.
In a first step, an inconsistent use of Earth rotation parameters (ERP) was identified.
Different sets were used for the integration and prediction of the ultra-rapid orbits in theinertial frame on the one hand and for the transformation back to the terrestrial frame on
the other hand. This problem could be solved by using one single set of ERPs covering thetime span for all affected calculations. The impact of this change made at 11-July-2013
can be seen in a significant reduction of the scatter of the z-rotation parameter in Fig. 2.
In a second step, a redesign of the ultra-rapid product generation was realized. Now, one
set of consistent orbital elements and ERPs is derived from combining normal equations.
The orbits are represented in the best possible way over the observed time interval withtwo days of observations, followed by an integration over the last observed 48 hours.
Nine empirical parameters are set up for the predicted part of the ultra-rapid product.
The ERPs are parameterized with 24 hours linear pieces in the observed and a linear
extrapolation for the predicted part. The new products have been submitted since 12Nov-2013 and were again included with weight in the combination a few days later. Thissecond change reduced the z-rotation even more (see Fig. 2) and improved the consistency
to the other ultra-rapid contributions which can be recognized in the decrease of the RMS
and weighted RMS of the CODE solution compared to the combined IGS ultra-rapid
product (see Fig. 3).
As another benefit from the new procedure, CODE now provides ERP files not only forthe midnight and noon but for all ultra-rapid update versions (00 h, 06 h, 12 h and 18 h).
800
RZ
RX
RY

600
400
[uas]

200
0
-200
-400
-600
-800
01Mar13

01Apr1301May13

01Jun1301Jul1301Aug13

01Sep1301Oct13

01Nov1301Dec1301Jan14

Figure 2: Rotation parameters for the z-, x- and y-axis from the Helmert transformation between
CODE’s submitted ultra-rapid orbits and the combined IGS product. The switch toconsistent ERPs took place at 11-Jul-2013, the complete redesign at 12-Nov-2013.

27

Dach, Schaer et al.: Center for Orbit Determination in Europe
160
RMS
WRMS

140
120
[mm]

100
80
60
40
20
0
01Mar13

01Apr1301May13

01Jun1301Jul1301Aug13

01Sep1301Oct13

01Nov1301Dec1301Jan14

Figure 3: RMS and weighted RMS (WRMS) of the CODE ultra-rapid orbits derived from the
combination of the IGS ultra-rapid product. At 12-Nov-2013 the first results from theredesigned ultra-rapid procedure were submitted.

3.3 Experience with RINEX-files based on real-time streams
Over several weeks in Summer 2013, the IGS final clock combination revealed some problems with the contribution from CODE. Many stations were excluded from the combination as they were exhibiting an abnormal behaviour compared to solutions from othercontributing analysis centers and therefore the combined solution.
After some investigations it was found that the problem was due to the different contentsof the RINEX files either downloaded directly as daily RINEX file with a sampling of 30 s
or constructed from the 15-minutes RINEX files with the 1 Hz high–rate sampling basedon real-time stream data. Although it seems to be legitimate to expect that the data
should be strictly the same (apart maybe for some gaps due to networking issues), using
one file upon the other may produce significantly different results for the same station1 .
The effect of these differences in the RINEX files on the solution is illustrated in Fig. 41Note, none of the stations have indicated by the NULLANTENNA antenna type that the antenna phasecenter corrections have already been applied before streaming the data.

KOUC 291/2013
Daily
Real−time0

Clock [ns]Clock [ns]

10

−10

−20

−30
0

1

2

3

4

5

6

7

8

9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Time [hod]

13
12
11
10
9
8
7
6
5
4
3
2
1
0
−1
−2
−3
−4
−5
−6
−7
−8
−9
−10
−11
−12
−13

KOUC 291/2013
Rec. clock diff.

0

1

2

3

4

5

6

7

8

9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Time [hod]Figure 4: Receiver clock corrections for site KOUC on day 291 of year 2013 estimated using adaily RINEX file stemming from daily/hourly dumps and from real-time data flow
(left) and the difference between the two solutions (right).

28

4 CODE contribution to the IGS–MGEX campaign
which displays the receiver clock correction estimates for station KOUC on day 291 ofyear 2013 as obtained when processing the data files in precise point positioning mode.
Differences up to 13 ns could be observed on that day.
CODE is using the 1 Hz high–rate sampling RINEX files for the densification of the 30 s
clock products to 5 s. Until this problem was identified, CODE was using indifferently
RINEX files produced from daily/hourly dumps or from a real-time data flow. The clock
generation procedure was adjusted in order to guarantee that the real-time data is onlyused to densify the clocks down to 5 s but not for generating the 30 s products. The
massive rejection of CODE solutions in the IGS combination has stopped since then.

4 CODE contribution to the IGS–MGEX campaign
Since 2012 CODE contributes to the IGS “Multi GNSS EXperiment” (MGEX) with themain goal to gain experience with the RINEX3 data format and the integration of the
new GNSS Galileo into existing processing chains and into the Bernese GNSS Software.
CODE has established an extensive raw data monitoring to RINEX3 data. The RINEX3
data monitoring bases on a XML–inventory that is generated as soon as the file is downloaded and copied into our database. All further requests for information or statistics
only access the XML–database, which is much more efficient than scanning each individual RINEX observation file for each individual request. Some standard extracts from theXML–inventory are freely available at ftp://ftp.unibe.ch/aiub/mgex/. Some of the(a) GPS(b) Galileo(c) BeiDou

Figure 5: Number of available satellites per GNSS in the RINEX3 files (available in ftp://ftp.
unibe.ch/aiub/mgex/plots); one line corresponds to one station.

29

Galileo E11
Galileo E12
Galileo E19
Galileo E20

15
10
5
0

50

100

150

Day of year 2013

Figure 6: Three-day long arc fit through
CODE Galileo orbits of consecutive
days estimating for the six initialconditions, three constant and three
once–per–revolution terms definedaccording to Beutler et al. (1994).

1.0

Galileo E11
Galileo E12
Galileo E19
Galileo E20

0.8
0.6

90

0.4

60

0.2

30

0.0

300
350
2012

35

85

Day of year

135
2013

185

0

absolute value of (β) (in deg)

RMS of longarc fit (in cm)

20

RMS of linear clock fit (in ns)

Dach, Schaer et al.: Center for Orbit Determination in Europe

Figure 7: RMS of daily linear fit through estimated epoch-wise Galileo satellite
clocks (big dots). The shaded areas
mark the eclipsing seasons of E11,E12 (green) and of E19, E20 (black).
The curves show the absolute valueof the elevation of the Sun w.r.t. thesatellite’s orbital planes (β) with thesame color code as the boxes.

information is even available in a graphical form, see Fig. 5 as examples. Apart fromRINEX3 files of the MGEX project meanwhile also numerous non-MGEX stations areincluded in the database. Thanks to the increasing number of MGEX stations and theconsideration of stations belonging to the EUREF Permanent Network (EPN), the numberof monitored stations providing RINEX3 data is meanwhile exceeding one hundred.
This data is used along with “regular” RINEX2 data in a fully-integrated, triple-GNSS,
double-difference processing, which delivers orbit positions (middle day of a 3-day long arc)of all active GPS, GLONASS, and Galileo satellites. The main changes during 2013 are theinclusion of the two additional Galileo IOV satellites launched in 2012 and the introductionof a station selection for the RINEX3 stations. An evaluation of the orbit quality isprovided in Fig. 6 . The time series of generated CODE MGEX orbits currently spansfrom GPS-week 1690 (DOY 150/2012) to 1763 (DOY 299/2013). A newly establishedprocessing chain solves for epoch-wise GPS and Galileo satellite clock corrections in azero-difference processing, based on the same data set as used for the double-difference
solution. The time series of Galileo clock corrections currently spans from GPS-week 1710
(DOY 288/2012) to 1763 (DOY 299/2013).
In order to support the IGS community with Galileo products and allow comparisonswith other groups’ results, the CODE MGEX products are available at ftp://cddis.
gsfc.nasa.gov/gnss/products/mgex (solution ID com stands for CODE-MGEX). The
next goals are the inclusion of BeiDou into the CODE MGEX processing, the extension of
the com orbit and clock time series, and the analysis of these extended time series (e.g.,systematic beta-angle dependency of the estimated Galileo satellite clock corrections, as
shown in Fig. 7).
30

5 CODE contribution to IGS repro2

5 CODE contribution to IGS repro2
CODE contributes witha new reprocessing series
to the IGS repro2 initiative. The effort has
started from RINEX observation files to review
the station selection (seeFig. 8).
The intervalfrom the beginning of1994 (GPS week 0730)
to the end of 2013 (GPSGNSSweek 1773) is covered.
GPS only
For the first years a GPSonly solution has been Figure 8: Network used for the GNSS reprocessing from CODE.
generated whereas starting with the year 2002 (GPS week 1147) a fully combined GPS/GLONASS solution wascomputed. Some more statistical information is provided in the plots of Fig. 9.
The re-processing follows the strategy from the operational CODE final processing scheme
as it was in Summer 2013. It generally follows the IERS conventions 2010 (Petit and Luzum2010) as well as the guidelines from the IGS (http://acc.igs.org/reprocess2.html).
As the operational solution series from CODE, the submission of the solution to the IGS
server at CDDIS will include a pure one-day (COF) as well as the corresponding three-day
long-arc (COD) solution. A comparison of the quality (median of the RMS per GNSS) of
fitting three consecutive days of the orbit solution is given in Fig. 10 . The long-arc series

94 95 96 97 98 99 00 01 02 03 04 05 06 07 08 09 10 11 12 13

45
40
35
30
25
20
15
10

250

GPS − only
GPS/GLONASS
total

200
Start of GLONASS
processing

50

Number of stations

Number of satellites

55

GPS
GLONASS
total

94 95 96 97 98 99 00 01 02 03 04 05 06 07 08 09 10 11 12 13300

Start of GLONASS
processing

60

150

100

50

5
0
50000

51000

52000

53000

MJD

54000

(a) Number of satellites

55000

56000

50000

51000

52000

53000

54000

55000

56000

MJD

(b) Number of stations

Figure 9: Statistical information on the CODE reprocessing result

31Dach, Schaer et al.: Center for Orbit Determination in Europe

94 95 96 97 98 99 00 01 02 03 04 05 06 07 08 09 10 11 12 13

94 95 96 97 98 99 00 01 02 03 04 05 06 07 08 09 10 11 12 13
20

GPS satellites
GLONASS satellites

Median of RMS in cm

Median of RMS in cm

20

15

10

5

0

GPS satellites
GLONASS satellites
15

10

5

0
50000

51000

52000

53000

MJD

54000

55000

56000

(a) COF series: Pure one-day solutions

50000

51000

52000

53000

54000

55000

56000

MJD

(b) COD series: Three day long-arc solutions

Figure 10: Median from the RMS of a three-day long arc fit through orbits of consecutive daysof the CODE reprocessing solution(COD) will also be published on the CODE’s FTP server (ftp://ftp.unibe.ch/aiub/
REPRO_2013/) in early 2014. The publication of the reprocessing series will include thefile ftp://ftp.unibe.ch/aiub/REPRO_2013/CODE_REPRO_2013.ACN containing a detailed
description of the models used.

References
Beutler, G., E. Brockmann, W. Gurtner, U. Hugentobler, L. Mervart, and M. Rothacher.
Extended Orbit Modeling Techniques at the CODE Processing Center of the International GPS Service for Geodynamics (IGS): Theory and Initial Results. Manuscripta
Geodaetica, 19(6):367–386, April 1994.
Dach, R., G. Beutler, H. Bock, P. Fridez, A. Gäde, U. Hugentobler, A. Jäggi, M. Meindl,
L. Mervart, L. Prange, S. Schaer, T. Springer, C. Urschl, and P. Walser. Bernese GPS
Software Version 5.0. Astronomical Institute, University of Bern, Bern, Switzerland,jan 2007. URL http://www.bernese.unibe.ch/docs50/DOCU50.pdf. User manual.
Dach, R., S. Schaer, S. Lutz, M. Meindl, H. Bock, E. Orliac, L. Prange, D. Thaller,
L. Mervart, A. Jäggi, G. Beutler, E. Brockmann, D. Ineichen, A. Wiget, G. Weber,
H. Habrich, J. Ihde, P. Steigenberger, and U. Hugentobler. CODE IGS Analysis
Center Technical Report 2012. In R. Dach, and Y. Jean, editors, IGS 2012 Technical
Reports, pages 35–46, 2013. IGS Central Bureau.
Petit, G. and B. Luzum (Eds). IERS Conventions (2010). IERS Technical Note 36,
Bundesamt für Kartographie und Geodäsie, Frankfurt am Main, 2010. URL http://www.iers.org/IERS/EN/Publications/TechnicalNotes/tn36.html.

32

References
Rodriguez-Solano, C. J., U. Hugentobler, P. Steigenberger, and S. Lutz. Impact of Earthradiation pressure on GPS position estimates. Journal of Geodesy, 86(5):309–317,
2012. doi: 10.1007/s00190-011-0517-4.
Springer, T. A., G. Beutler, and M. Rothacher. A new Solar Radiation Pressure Modelfor the GPS Satellites. GPS Solutions, 3(2):50–62, 1999.
All publications, posters, and presentations of the Satellite Geodesy research group at
AIUB are available at http://www.bernese.unibe.ch/publist .

33

Dach, Schaer et al.: Center for Orbit Determination in Europe

34

NRCan Analysis Center Report 2013
Y. Mireault, R. Ghoddousi–Fard, B. Donahue, and F. Lahaye
Natural Resources Canada, Canadian Geodetic Survey
615, Booth Street, Ottawa, ON, Canada K1A 0E9
E-mail: Yves.Mireault@NRCan.gc.ca

1 Introduction
In 2013, the Geodetic Survey Division (GSD) of Natural Resources Canada (NRCan)changed its name to the Canadian Geodetic Survey (CGS) and merged within the Surveyor
General Branch (SGB). This report addresses the major product changes and events that
occurred within NRCan during the year 2013.

2 Review of 2013
Readers are referred to the Analysis Coordinator website (http://acc.igs.org) for historical combination statistics of the NRCan–AC products. There were no major changes
made to NRCan–AC Rapid and Final core products in 2013. However, a few changes tothe Ultra–Rapid processing strategy are worth mentioning.

2.1 GNSS Ultra–Rapid Products
Although GNSS Rapid/Final orbit and clock products have been produced for more than
two years, our Ultra–Rapid solution was still a ’GPS–only’ solution until early September 2013. The Ultra–Rapid GNSS implementation required several changes and carefulplanning in order to keep the same product quality and availability. Our ultimate goal
was to generate 30s GNSS clocks on an hourly basis to satisfy our CSRS–PPP clientsprocessing GNSS kinematic data. At the end of 2013, we were able to generate GNSS
orbits on an hourly basis but due to computer resources constraints, we are currently able
to generate 30s GNSS clocks only every 3h, i.e. at 00h, 03h, 06h, ... and 21h. For theremaining hours, 30s ’GPS–only’ clocks are generated. Our first official contribution to
the IGS Ultra–Rapid GLONASS combination (IGV) was on September 9, 2013, hour 12(i.e. emu17571_12).

35

NRCan AC
Table 1: Main characteristics of NRCan Ultra–Rapid Products Generation

Characteristics

BeforeFrom2013 September 09

2013 September 09(emu17571_12)(emu17571_12)‘GPS only’

GPS/GLONASS

StationOrbit

1 x 50 stations

3 x 30 stations

Clusters

Clock

1 x 45 stations

1 x 45 stations

Sp3

15 min15 minClk

30 sec30 secOrbit

HourlyHourly (GNSS)

Interval(1)Cycle(2)Every 3h for
Clock

Hourly_00 _03 _06 _09..._21 (GNSS)

Hourly for_01 _02 _04 _05 _07 _08..._22_23

Orbit

Less than 1h(‘GPS only’)

Less than 1h15 (GNSS)
Less than 2h for(3)

Latency

ClockLess than 1h30

_00 _03 _06 _09..._21 (GNSS)

Less than 1h30 for_01 _02 _04 _05 _07 _08..._22 _23(‘GPS only’)(1) Product intervals.
(2) Processing cycle.
(3) Latency from the last available data.

Tab. 1 shows the main characteristics of the new NRCan GNSS Ultra–Rapid products(EMU). Fig. 1 and Fig. 2 show the Ultra–Rapid GPS and GLONASS orbit precision
during 2013. The graphs are divided in two parts: a 0–24h estimated portion and a 24–
48h predicted portion. Each portion is divided into 3h bins to better see the orbit behavior
when predicted time increases. The NRCan Ultra–Rapid clock precision is shown in Tab. 2.
For completeness, NRCan Rapid and Final products are also included.

36

2 Review of 2013

EMU versus IGR
2013, Jan 1 - Dec 31
20

20

Median Orbit RMS (cm)

Estimated Portion

Predicted Portion

15

15

10

10

5

5

0

0
3

6

9

12

15

18

21

24

3

6

9

12

15

18

21

24

Time Interval (hours)

Figure 1: GPS Ultra–Rapid Orbit Median RMS for 2013.

EMU versus IGL
2013, Jul 19 - Dec 31
20

20

Median Orbit RMS (cm)

Estimated Portion

Predicted Portion

15

15

10

10

5

5

0

0
3

6

9

12

15

18

21

24

3

6

9

12

15

18

21

24

Time Interval (hours)

Figure 2: GLONASS Ultra–Rapid Orbit Median RMS for 2013.

37

NRCan AC
Table 2: Orbit and Clock Median RMS of NRCan–AC Products for 2013

Orbits(1) (cm)Product

Clocks(2) (ns)GPS

GLONASSGPS

GLONASSEMU estimated (00–24h)(3)

2

2

0.09

0.08(4,5)

00–03 h03–06 h09–12 h21–24 h

4
4
5
10

7
8
10
18

Not meaningful!

2.0

4.0

0.07

EMU predicted(3)EMR Rapid and Final (3)0.08(4)(1) Orbit RMS after applying a 7–parameter Helmert transformation.
(2) Clock RMS after proper clock alignment.
(3) Comparison against IGR for GPS and IGL for GLONASS.
(4) Comparison against ESA Final products after proper clock alignment and individual
satellite bias removal.
(5) Better RMS than GPS due to comparisons made on a satellite by satellite basis.

3 Ionosphere and DCB Monitoring

Daily global ionosphere maps using nearly 400 GPS stations are being generated internallyand are expected to be submitted to IGS in 2014. Near real–time ionosphere maps continue
to be generated internally both in the form of near real–time spherical harmonic coefficientsand since day 300, 2013 also as daily IONEX files containing 96 maps per day. During
2013, the number of high–rate stations being processed for near real–time ionosphere map
generation has increased to about 165. GPS P1–P2, P1–C1 and P2–C2 as well as receiverspecific P1–C1 DCBs are estimated daily.
Schematic regional and global ionospheric irregularity maps from GPS phase rate statistics(Ghoddousi-Fard et. al 2013) based on RT–IGS stations are generated internally in nearreal–time. A historical database of these statistics is continuously accumulated for on–
going scintillation studies.

38Reference

Reference
Ghoddousi-Fard, R., P. Prikryl., and F. Lahaye. GPS Phase Difference Variation Statistics:
A Comparison between Phase Scintillation Index and Proxy Indices, Advances inSpace Research, 52(8), 2013. doi: 10.1016/j.asr.2013.06.035.

39

NRCan AC

40

The ESA/ESOC IGS Analysis Center
T.A. Springer, L. Agrotis, J. Feltens, M. van Kints,
N. Romero, F. Dilssner, C. Flohrer, W. Enderle,
E. Schoenemann, and R. Zandbergen
European Space Operations Center
Darmstadt, Germany

1 Introduction
The IGS Analysis Center of the European Space Agency (ESA) is located at the European
Space Operations Center (ESOC) in Darmstadt, Germany. The ESA/ESOC Analysis
Center has been involved in the IGS since its very beginning in 1992. In this report wegive a summary of the IGS related activities at ESOC in 2013.

2 Overview 2013
2.1 Routine Products
The ESA/ESOC IGS Analysis center contributes to all the core IGS analysis center products, being:• Reprocessed Final GPS products (repro2)– Provided from 1995 to 2013

– Based on 24–hour solutions using 150 stations GPS–only, until 2008
– Based on 24–hour solutions using 110 stations GPS+GLONASS, from 2009
– Consisting of Orbits, Clocks (300s), daily SINEX coordinates, and EOPs
– Clocks with 30s sampling are also generated but not made publicly available• Final GNSS (GPS+GLONASS) products– Provided weekly, normally on Friday after the end of the observation week41

ESA/ESOC AC– Based on 24–hour solutions using 150 stations– True GNSS solutions obtained by simultaneously and fully consistently processing of GPS and GLONASS measurements, using a total of around 55 GNSS
satellites– Consisting of Orbits, Clocks (30s), daily SINEX coordinates and EOPs, andIonosphere• Rapid GNSS (GPS+GLONASS) products– Provided daily for the previous day– Available within 3 hours after the end of the observation day– Based on 24–hour solutions using 110 stations– True GNSS solutions obtained by simultaneously and fully consistently processing of GPS and GLONASS measurements, using a total of around 55 GNSS
satellites– Consisting of Orbits, Clocks, Ionosphere, and EOPs
– Rapid SINEX coordinates and EOPs available as well
• Ultra–Rapid GNSS (GPS+GLONASS) products– Provided 4 times per day covering a 48–hour interval; 24 hours of estimatedplus 24 hours of predicted products– Available within 3 hours after the end of the observation interval which startat 0, 6, 12, and 18 hours UTC– Based on 24 hours of observations using 110 stations– True GNSS solutions obtained by simultaneously and fully consistently processing of GPS and GLONASS measurements, using a total of around 55 GNSS
satellites– Consisting out of Orbits, Clocks, and EOPs
– Separate Ionosphere estimates and predictions• Real–Time GNSS services– Generation of two independent real–time solution streams– Analysis center Coordination– Generation and dissemination of the IGS Real Time Combined product stream• GNSS Sensor Stations42

2 Overview 2013
– A set of 10 globally distributed GNSS sensor stations– Station data available in real–time with 1 second data sampling
Besides these core products ESA is very active in different working groups. Most notably are our efforts in the Real–Time Service where besides being one of the analysis
centers we are also responsible for the analysis center coordination. Also our efforts in thescope of MGEX, the antenna calibarations and satellite orbit modeling working groups
are significant.
An up to date description of the ESA IGS Analysis strategy may always be found at:
ftp://dgn6.esoc.esa.int/products/esa.acn

2.2 Product Changes
The main changes in our processing in 2013 were the following:• Improved reference frame alignment and consistency between the different products• Upgrade of the ESA/ESOC GNSS Sensor Station network• Some minor modifications were made in the handling of the GPS–GLONASS intersystem biases• Integration of Ionosphere estimation into the NAPEOS software allowing for
GPS+GLONASS based ionosphere estimation

2.3 Product Highlights
The main highlight of the ESA/ESOC Analysis center products is that they are one of
the best products available from the individual IGS analysis centers. Secondly the ESA
products are one of the most complete GNSS products. In fact ESA was the first IGS
analysis center to provide a consistent set of GNSS orbit and clock products. Our GNSS
products constituted the very first products that could, and are, used for true GNSS
precise point positioning. In particular for this purpose, the sampling rate of our final
GPS+GLONASS clock products is 30 seconds.
Another special feature of the ESA products is that they are based on completely independent 24 hour solutions. Although this does not necessarily lead to the best products,
as in the real world the orbits and EOPs are continuous, it does provide a very interesting
set of products for scientific investigations as there is no aliasing and no smoothing.
An other unique feature is that our rapid products are, besides being one of the best,
also one of the most timely available products. Normally our GNSS rapid products areavailable within 2 hours after the end of the observation day whereas the official GPS–only
IGS products become available only 17 hours after the end of the observation day, a very

43

ESA/ESOC AC
significant difference.
In 2013 we have made some small modifications in the initialization and alignment of
the GPS–GLONASS Intersystem biases (ISB’s). The ISB values are now initialized in
our preprocessing using the broadcast orbit information from both GPS and GLONASS.
In this way the estimated GLONASS clocks remain aligned to the GLONASS broadcast
clocks. Consequently the ISB values reflect to a large extend the time difference between
the GPS and GLONASS time frames.
In the scope of 2013 we improved our reference frame alignment and the consistency
between our different products. Our orbit and clock products now come from the sameprocess based on the same reference frame realisation. Thanks to changes in the NAPEOS
3.7 version, which we started to use in November 2012, we are now also able to use justa subset of the stations for the reference frame alignment. The improved alignment ofour products is clearly visible in the IGS combination, in particular the rotations. So ourorbit, clock and SINEX products are now all 100% consistent which was not the case prior
to this change. This change took effect in GPS week 1730. However, we noticed thatthe absense of translational constraints did significantly impact the sigma of our clock
products. To avoid this negative influence from our improved reference frame alignment
we have introduced translational constraints from GPS week 1737.

3 Reprocessing Activities
ESA/ESOC has participated in the first IGS reprocessing efforts (repro1) for the IGS contribution to the realisation of the International Terrestrial Reference Frame 2008 (ITRF2008)
and will also participate in the reprocessing for the ITRF2013. For this reprocessing effort
ESA will process all historic GNSS data of the IGS from 1994 to 2013. In this reprocessing
the years 1994 to 2008 are reprocessed using only GPS observations, but from 2009 onwards the reprocessing fully includes the GLONASS observations and thus provides true
GNSS solutions.
The products from the first ESA official reprocessing efforts, based on the ITRF2005
reference frame, are available from the official IGS data centers with the label "es1". The
most recent ESA reprocessing products, based on the ITRF2008, are available from theofficial IGS data centers with the label "es2".
An interesting difference between our es1 and es2 reprocessing is that, as mentioned before,
from 2009 onwards our es2 products are GNSS products. Also for our es2 products we dogenerate 30 second clock estimates. We produce these high–rate clock products because
we are also very active in processing GNSS data from Low Earth Orbiting (LEO) receivers.
For LEO processing high–rate clocks are very much needed to get accurate orbits based
when using the well–known PPP approach for precise orbit determination.

44

4 GNSS Sensor Station Upgrade

4 GNSS Sensor Station Upgrade

ESA/ESOC is operating a network of globally distributed GNSS sensor stations, supporting internal and external projects (i.e. GRAS GSN, IGS, ESA Space Tracking Stations)as well as distributing the data for the scientific community (IGS and EUREF).
Until 2010 the ESOC GNSS sensor stations were limited to tracking either GPS or GPS
and GLONASS. In recent years we have seen the start of the evolution of the existing
GNSS and the emergence of new constellations. For the existing GNSS new satellites andsignals are becoming available to the user segment, including new civilian signals for GPS(L2C and L5), CDMA modulation for GLONASS (L3). The completely new constellations
that are starting to emerge are the European Galileo, the Japanese QZSS, and the Chinese
BeiDou system.
Thus at ESA/ESOC we recognized that our ESOC GNSS sensor station network needed to
be upgraded with state–of–the–art technology. A dedicated assessment was made, trading
off between the technical requirements and the commercial market costs of the GNSS
equipment required for the upgrade. This resulted in the procurement of 25 Septentrio
PolaRx4 receivers and 25 Septentrio Choke Ring MC antennas, for which a deployment
schedule was drafted in early 2012. This upgrade should allowed ESOC to keep its high–level of quality and reliability in GNSS operations and increased the data availability. The
upgrade has been replacing the station equipment of the current ESOC GNSS network
but also expanded the number of stations in order to enhance the geographical coverageand provide better depth of coverage for all the GNSS constellations. With the data of
our stations we participate in the MGEX project providing Rinex 3 files with data from
GPS, GLONASS, Galileo, BeiDou, and QZSS.
Fig. 1 shows the status of the ESOC GNSS sensor stations as of January 2014. Of theexisting 10 GNSS sensor stations 7 were upgraded in 2012 to multi–GNSS receivers andantennas. The remaining 3 (KIRU, REDU and MAL2) were upgraded in the 1st, 3rd
and 4th quarter of 2013, respectively. In addition, a Septentrio PolaRx4 replaced themulti–GNSS JAVAD Delta receiver at MGUE in the 4th quarter of 2013, yielding a fully
homogenous receiver network. Advances were also made for the installation of a new
GNSS station at ESA’s Santa Maria (Azores) site, expected to be operational in the 1stquarter of 2014.
During 2013 agreements with several third parties were negotiated to install GNSS stationsin Japan, Russia, New Zealand, Malaysia, Thailand, with the objective of expanding the
ESA/ESOC GNSS network. Negotiations with third parties in U.S.A, India, U.A.E andCanada have also been initiated, but are still in a preliminary stage.

45

ESA/ESOC AC

Figure 1: Status of the ESOC GNSS sensor stations as of January 2014.

46

5 Real Time Activities

5 Real Time Activities

On of the major achievements in the Real Time area in 2013 was that in April the IGS
Real Time Pilot project transitioned into the IGS Real Time Service.
Over the last 10 years, ESOC has embarked on a program to build a Real Time GNSS software and network (receiver) infrastructure. RETINA (system for REal TIme NAvigation)
has been modeled based on ESOC’s experiences in Real Time satellite control systems andincludes many of the elements for data processing, archiving and visualisation that arecommon to such systems. ESOC is utilising this infrastructure by participating in the IGS
Real Time Service, assuming the roles of Real Time Analysis center, RT Observing Station
Data Provider and Analysis center Coordinator (ACC). In the latter role, ESOC has been
generating and disseminating the IGS Real Time Combination stream after processing theReal Time solutions from up to ten Analysis centers.
Included in the combination solutions are two streams generated by the ESOC Real Time
Analysis center. One of these uses orbit information generated by the NAPEOS software,
Springer (2009), which is operated under RETINA scheduling control and provides orbit
updates every 2 hours. The second ESOC solution stream uses the IGS rapid orbit product,
which is updated every 6 hours.
Participation in the IGS Real Time activities has stimulated the involvement of ESOCin the development of standards and formats for GNSS data and products. ESOC has
been instrumental in the decision of the IGS to join the Radio Technical Commission for
Maritime Services (RTCM), which is the primary standards setting organisation for RealTime GNSS services. NRCan and ESOC are the two agencies that represent the IGS at
the RTCM meetings. Work with the RTCM has focused on the following areas:• Development of standards and formats for transmission of multi–constellation observations in Real Time (RTCM–MSM)• Development of standards and formats for the transmission of Real Time orbit andclock products (RTCM–SSR)
In addition, the IGS took a high–level decision to form a joint RTCM–IGS working groupfor the further development of the RINEX observation format. The terms of reference of
this WG have been negotiated by ESOC and approved by the IGS Governing Board andby the RTCM.
The highlight of the (2013) Real Time ACC activities in 2013 was the launch of the official
IGS Real Time service. ESOC will retain the ACC role in this service. In order to ensure
a high availability for this service, combination processes are now running simultaneously
at two servers external to ESOC, in the UK and in Canada (NRCan).

47

ESA/ESOC AC

6 Ionosphere Modeling Activities
ESA/ESOC contributes with IONEX products to the IGS Ionosphere Working Groupsince its inception in 1998, initially with daily global ionospheric TEC maps in final mode
(11 days latency). ESA/ESOC’s activities for the ionosphere in the frame of the IGS since2004 can briefly be summarised as follows:• Spring 2004: Start routine delivery of daily global ionospheric TEC maps in rapid
mode (1 day latency)• December 2005: Start routine delivery of TEC maps in 2–hour time resolution,i.e. since then each ESA IONEX file provides 13 TEC and RMS maps per day• September 2009: Commence submission of IONEX files containing 1 and 2 days
ahead predicted TEC maps in 2–hour time resolution• February 2009 – January 2010: ESA Study: GNSS Contribution to Next Generation
Global Ionospheric Monitoring (Feltens (2009) and Feltens (2010))• July 2010: Commence combination of predicted Ionosphere Associate Analysis centers (IAACs) TEC maps and submission of combined predicted IGS IONEX files in
2 hour time resolution• February 2011: Commence submission of ESA IONEX files with 1–hour time resolution• January 2013: The IONMON became an integral part of ESOC’s NAPEOS software
allowing for GPS+GLONASS based ionosphere estimation
ESOC employs the Ionosphere Monitoring Facility (IONMON) for its ionosphere processing. IONMON algorithms were initially devoted to single layer approaches. Since 1999,
investigations were undertaken into the direction of 3D ionosphere modelling. Startingwith an extended Chapman profile approach, in the subsequent years the concept of amultilayer modelling was developed, combining empirical surface functions to describe
the horizontal structures of the ionosphere with vertical profile functions, which should, tosome limited extent, also allow for a physical interpretation of results. It was foreseen that
this new modelling should process TEC data from GNSS combined with observed electron density profiles from different sources, namely CHAMP, F3/COSMIC and ionosondein least squares fits. In relation to these IONMON developments, from March 2009 to
January 2010 the ESA Study "GNSS Contribution to Next Generation Global Ionospheric
Monitoring" was conducted, Feltens (2009) and Feltens (2010), working out recommendations for a new ionosphere monitoring system, identifying potential users, and practicaland scientific applications in terms of, among others:• Potential ionospheric observation data sources, e.g., TEC from GNSS and radio
beacons, LEO topside TEC, electron density profiles from LEO radio occultation,
ionosondes, and more48

7 Summary• Near–Real–Time (NRT) and Real–Time (RT) suitability• Predictability of the ionosphere’s state• Physical interpretability

In 2013, IONMON became an integral part of ESOC’s NAPEOS software. The inclusion
into NAPEOS enables the IONMON to nearly double the number of ground stations thatcan be processed. In addition, the IONMON can now process further GNSS data than
only GPS, e.g. GLONASS and Galileo.

6.1 Current Activities
ESOC’s actual ionosphere model development efforts are directed to 3D modelling, where
the concept had to be changed from the least squares fitting of TEC and electron density
data into a model comprising a combination of vertical and horizontal functions, to an
approach in which TEC and electron density observables from different sources will be assimilated into a background model. It turned out that, in spite of including F3/COSMIC
and CHAMP electron densities in addition to GNSS TEC observables, the data coverage
is not yet dense enough to perform reliable and stable least squares fits. The mathematical algorithms for this new 3D assimilation approach were recently worked out anddocumented in an ESOC–internal technical note (currently still draft). At the moment
the new assimilation approach is coded, based on these algorithms, as new component of
NAPEOS. From its design, the assimilation scheme shall also enable NRT and RT processing and upgrade time resolutions down to several minutes, i.e. simple, fast and robustalgorithms are required.
Once the implementation of the new assimilation approach into NAPEOS has been successfully concluded, ESOC’s ionosphere processing will be switched over from the current
single layer modelling to this new 3D modelling technique. This will then also concern
ESOC’s ionosphere products delivered to the IGS, e.g. new aspects such as 3D IONEX.
The implementation of a more sophisticated Iono prediction scheme at ESOC will be an
important future topic too. In parallel to the tasks described above, activities are ongoingto establish a new model for the plasmasphere in a cooperative effort with the German
Aerospace Center (DLR) in Neustrelitz, Germany. This plasmasphere model will thencomplement the new 3D assimilation approach.

7 Summary
The European Space Operations center (ESOC) of the European Space Agency (ESA)
Analysis Center has continued to produce "best in class" products for the IGS in 2013.
Practially all products are generated using the Navigation Package for Earth Orbiting
Satellites (NAPEOS ) software. NAPEOS is a state of the art software that is highly ac-

49

ESA/ESOC AC
curate, very efficient, robust and reliable. It enables ESA/ESOC to deliver the high quality
products as required for the IGS but also for the other space geodetic techniques DORIS
and SLR. This is important because besides being an IGS Analysis center, ESA/ESOC isalso an Analysis center of the IDS and the ILRS.

References
Springer, T., R. Zandbergen, and A. Águeda Maté. NAPEOS Mathematical Models
and Algorithms. DOPS–SYS–TN–0100–OPS–GN, Issue 1.0, Nov 2009, Available at
ftp://dgn6.esoc.esa.int/napeos
Feltens, J., M. Angling, N. Jakowsk, C. Mayer, M. Hoque, M. Hernández-Pajares,
A. García-Rigo, R. Orús-Perez, and A. Aragón-Ange. Analysis of the State of the
Art Ionosphere Modelling and Observation Techniques. DOPS–SYS–TN-0017–OPS–
GN, Iss. 1/0, 26/06/2009.
Feltens, J., M. Angling, N. Jackson-Booth, N. Jakowsk, M. Hoque, C. Mayer,
M. Hernández-Pajares, A. García-Rigo, R. Orús-Perez, A. Aragón-Ange, and J.
Miguel Juan Zornoza, Recommendations for a New European Ionosphere Monitoring
System. Iss. 1/0, DOPS–SYS–RP–5001–OPS–GN Iss. 1/0, 20/01/2010.

50

GFZ ANALYSIS CENTER OF IGS
Annual Report for 2013
G. Gendt, Z. Deng, M. Ge, T. Nischan, M. Uhlemann,
G. Beeskow, A. Brandt, and M. Bradke
Helmholtz–Zentrum Potsdam– Deutsches GeoForschungsZentrum (GFZ)
Department 1: Geodäsie und Fernerkundung
Telegrafenberg A 17, 14473 Potsdam, Germany
E–mail: gendt@gfz-potsdam.de

1 SummaryDuring 2013 the standard IGS product generation was continued with minor changes inthe software EPOS–8. A switch from weekly to daily SINEX files was performed and new
30–sec clock products were generated.
End of 2013 the processing for the 2nd IGS Reprocessing campaign was nearly finished.
The capability to process in addition to GPS and GLONASS also Galileo and BeiDoudata was demonstrated with the available M–GEX data.

2 Products
The list of products provided by GFZ is summarized in Tab. 1.

3 Data processing and latest changes
EPOS–8 is following the IERS Conventions 2010 (Petit and Luzum 2010). Recent changes
in the processing are listed below in Tab. 2. The station network used in the processing isshown in Fig. 1. For the IGS Final, Rapid and Ultra Rapid about 200, 110, and 95 sites
are used, respectively, whereas the sites providing GLONASS data is steadily increasing.
Some processing related informations are given in Tab. 3.

51

GFZ AC

Table 1: List of products provided by GFZ AC
Final(GLONASS since week 1579)

gfzWWWD.sp3
gfzWWWD.clk
gfzWWWD.snx
gfzWWW7.erp
gfzWWW7.sum
gfzWWWD.tro

Orbits for GPS/GLONASS satellites
5–min clocks for stations and 30–sec clocks GPS/GLONASS satellites
Daily SINEX files

Rapid(GLONASS since week 1579)

gfzWWWD.sp3
gfzWWWD.clk
gfzWWWD.erp

Orbits for GPS/GLONASS satellites
5–min clocks for stations and GPS/GLONASS satellites

Ultra(every 3–hours; provided to IGS every 6 hours, GLONASS since week 1603)

gfuWWWD.sp3
gfuWWWD.erp

Adjusted and predicted orbits for GPS/GLONASS satellites

Summary file incl. Inter–Frequency Code Biases (IFB) for GLONASS
1–hour ZPD estimates

Table 2: Recent Processing changes
Date

IGS

IGR/IGU

Change2012–08–19
2013–05–05
2013–09–26

w1702
w1739
w1758

–
–
w1759.4

Switch from 7–day to 1–day SINEX files
Generation of 30–sec clock products (Final only)
Implementation of albedo and antenna thrust modelling

For the reprocessing campaign following changes were implemented:
2nd order ionosphere corrections (only REPRO2)
VMF (only REPRO2)

Table 3: Number of stations and processing time for different GFZ products

52

IGS
Product#Sites#Sites
GLONASS

Duration
[h]

Ultra
Rapid
Final

95
110
200

65
80
115

∼1
∼2
∼4

3 Data processing and latest changes""

GPS only

GPS + GLO

Figure 1: Used IGS stations for combined GPS+GLONASS data processing.

3.1 New 30–sec clock product
Since middle of 2013 GFZ is generating 30–sec clock solutions for the Final network.
In a last step, after the 5–min data analysis is finished, the computation of the 30–sec
clock corrections is performed. This step is using the cleaned data including all known
ambiguities to solve in a single adjustment step all the clock corrections. This step takes
about 30 min per day. The final clock product files contain 5–min clocks for all stations,
30–sec clocks for the satellites and in addition 30–sec clocks for a few good stations to beable to switch the reference clock also for the 30–sec clocks.

3.2 Generation of daily SINEX files
Compared to the weekly SINEX files the daily SINEX files can provide better resolutionof loading displacements as well as tracking of discontinuity events, etc. At GPS week
1702 GFZ switched to the daily SINEX files for the operational final solution. The daily
SINEX files are strictly based on daily data.

3.3 Albedo and antenna thrust modelling
For the albedo modelling the analytical model from Rodriguez–Solano et al. (2012) was
implemented. The thruster power is not well documented for all satellites, so the following
values are used at the moment:• Antenna power default is set to 80 Watts for all satellites.
• For GPS satellites the values are defined as follows:

53

GFZ AC
Block I/II/IIA
Block IIR–A/B
Block IIR–M
Block IIF

: 76 Watts: 85 Watts: 198 Watts: 249 Watts (154 Watts if no M–CODE)

The activation of the albedo modelling is resulting in a scale “jump” of the orbits of about+0.05 ppb (Fig. 2).

4 Processing of M–GEX data at GFZIn 2012 the IGS started the MGEX campaign (Montenbruck 2013) where Multi–GNSS
station data from a global ground tracking network are collected and made public to thecommunity in RINEX 3 format (MacLeod 2013). The stations receive the data fromthe new GNSS systems, such as Galileo, BeiDou, and QZSS. About 80 MGEX tracking
stations are available to the project in late 2013. Based on these MGEX data GFZ provides
precise satellite orbit and clock solutions from a combined processing of GPS+Galileo or
GPS+BeiDou observation data.

COD
EMR
ESA
GFZ
GRG
JPL
MIT
NGS
SIO
IGR

Scale of Final Orbits (AC solutions minus IGS Final)
1.0(weekly means)

Orbit scale [ppb]

0.5

0.0

-0.5

-1.0
1710

1720

1730

1740
Time [GPS weeks]

1750

1760

1770

NOAA NGS, 11.01.2014 19:30 (GMT)

Figure 2: Scale changes in GFZ Final orbits due to the introduction of albedo modelling in week
1759 (plot from ACC web site).

54

4 Processing of M–GEX data at GFZ

NYA2

REYK
UCAL
UNBD/S/3
USN4

STFU
AUT0

KIR8
MYVA
HOFN
MAR7 METG
ONS1
POTS
DLF1
BRUX
GOP6/7
BRSTREDUGRAB
WTZR/Z/3
OBE4
ZIMJ/3
GRAC
TLSE
M0SE
CEBR

KZN2
ULAB
TASH
CHOF
WUH2
JFNG

LLAG

GMSD

MAO0
LMMF
SGOC

KOUG
NKLG

SIN0/1

NURK

JOG2
FTNA

AREG

THTG

CHPG

CONZ

WIND

REUN

NRMG

HARB/HRAG
CUT0

LPGS

KRGG

UNX2/3
WARK
OUS2

RGDG
.RIO2
OHIX

IGS (~100)
GPS only

MGEX (60)
GPS+GALMGEX (27)
GPS+BDS

Figure 3: Global network of IGS (green) and MGEX stations, which were set up for data processing. The 60 Galileo–MGEX stations (blue) realize a good global coverage for practical
Galileo orbit determination purposes, whereas a lot of the 27 BeiDou–MGEX stations(red) are concentrated in Europe.

4.1 Galileo data processing
The study of Uhlemann et al. (2013) is a demonstration of what is possible with the current
MGEX tracking network. The focus lies on precise orbit and clock determination of thefour Galileo In–Orbit–Validation (IOV) satellites and also the investigation of station
tracking behaviour and orbit issues for a test period of 10 weeks.
It was shown that the Galileo orbits can be determined with accuracies of 5 to 10 cm, which
was additionally underlined through comparisons with external solutions of other MGEX–
ACs (see Fig. 4) and Satellite Laser Ranging (SLR) observations. The investigations haveclearly shown that the contribution of SLR measurements was very useful to identify thesource of the periodic variations in the clock estimates. The adjusted satellite clocks andtheir stabilities are in a level of about 20ps and suffer only from obvious orbit modellingproblems during eclipsing periods.
A further enhancement of EPOS–8 was the introduction of Galileo ambiguity fixing.
The integer carrier–phase ambiguities are fixed for GPS and Galileo separately. Baseline
lengths up to 4000 km were allowed in both cases. To resolve the double–difference ambiguities for Galileo the available stations were grouped according their (receiver–dependent)
observation types:• Group 1: L1C/L5Q (e.g. BRUX)• Group 2: L1X/L5X (e.g. POTS)

Only between stations belonging to the same group it was in a first step allowed to select55

GFZ AC

15

com
gfm
tum

E11
10
5
0
15
E12

WRMS [cm]

10
5
0
15
E19
10
5
0
15
E20
10
5
0
1738

1740

1742

1744

1746

1748

GPS−Week

Figure 4: Weighted RMS (WRMS) of individual MGEX–AC orbits with respect to the combined
result for all Galileo–IOV satellites (Note: E20 out–of–service around GPS–week 1745)

56

4 Processing of M–GEX data at GFZFixed ambiguities [%]

400
300

80

200
100

60
GAL WL
1738

1740

Num. of amb.

GAL NL
1742

1744

1746

Number of ambiguities

500

100

0
1748

GPS−Week

Figure 5: Galileo ambiguity fixing success rates for wide–lane (blue) and corresponding narrow–lane (red) ambiguities as well as the total number of ambiguities (black).

the linear independent baselines until afterwards all remaining baselines were defined.
The statistic of the Galileo wide–lane (WL) and narrow–lane (NL) ambiguities is given
in Fig. 5. It can be seen that, despite their low overall number, it is possible to fix theGalileo ambiguities with a success rate of only about 85%. This may be a result from thevery long baseline lengths, because only max. 30% of the baselines are shorter then 1000
km, or it may come from the different observation types which are given in the network.
These effects will be studied further.

4.2 BeiDou data processing
Currently the Chinese BeiDou constellation provides observation data of five Geostationary–
Earth–Orbit (GEO) satellites, five Inclined–GeoSynchronous–Orbit (IGSO) satellites andfour Medium–Earth–Orbit (MEO) satellites.
Based on tracking data of BeiDou–capable receivers from the MGEX network up to 27
global distributed stations (red circles in Fig. 3) are selected to estimate orbit and clockparameters of the BeiDou satellites. The orbit analysis is based on a time period of 2
weeks, namely GPS–weeks 1753 and 1759.
4.2.1 Processing Scheme
An upgraded version of EPOS.P8 software is used for the processing of dual–frequency
GPS+BeiDou data. The general processing strategy is similar to the GPS+Galileo processing scheme, ambiguity–fixing was also set up for BeiDou IGSO and MEO satellites.
The ionosphere–free linear combination of B1 (1561.098 MHz) and B2 (1207.140 MHz) isused and the a priori orbits are taken from the broadcast navigation message files, which
are provided by MGEX. The observation data are processed in daily batches and normal

57

GFZ AC200
alongacrossradialMean overlap RMS [cm]

GEO
150

100
IGSO

MEO

50

0

C01 C02 C03 C04 C05 C06 C07 C08 C09 C10 C11 C12 C13 C14

Figure 6: Mean orbit overlap RMS[cm] in along, across and radial.

equations (NEQs) are kept to generate 3–day solutions.
4.2.2 Results
To check the orbit quality the RMS of the orbit overlap differences (4 hours) in along–track,cross–track and radial directions are taken. The statistic results are given in Fig. 6. GEOs
have a larger RMS than IGSOs and MEOs, because the GEO orbit determination suffers
clearly from the weak observation geometry and the lack of orbit dynamics which result
higher RMS values. The individual results of the four MEOs are more homogeneous thanthe others which are related to our orbit modelling experiences for this kind of satellites.

5 Reprocessing activities
GFZ is contributing to the IGS and TIGA Reprocessing Campaign. For the IGS/TIGA
reprocessing the GPS data of the global tracking network of 307/794 stations for the timespan from begin of 1994 until end of 2012 (GPS weeks 730 to 1720) were reprocessed. The
numbers of reprocessed GPS satellites/stations are given in Fig. 7 and the distribution of
the GPS stations is shown in Fig. 8. The reprocessing is performed on the local Linuxcluster with a maximum number of 40 computers/servers. With EPOS.P8 a high degreeof automation of the individual processing jobs can be achieved.
Since the processed number of TIGA stations can reach up to 560 daily (Fig. 7) and
EPOS.P8 can process up to 250 stations in a single job, the TIGA stations must be split
into several sub–networks. One of the sub–networks is the IGS reprocessing network,
which has been done with a processing scheme similar to GFZ IGS routine analysis. A
flow diagram of the TIGA reprocessing is shown in Fig. 9.

58

5 Reprocessing activities

600

32
IGS_REPRO sites
TIGA_REPRO sites

30

GPS Satelites
400
28
300
26
200
24

100
0

number of satellites

number of stations

500

1995

1997

1999

2001

2003

2005

2007

2009

2011

22
2013

Figure 7: Weekly number of stations and satellites included in the IGS/TIGA reprocessing.
TIGA reprocessing is based on the same set of IGS stations, so that the difference
to IGS reprocessing shows the number of processed TIGA–only stations.

IGS (307)

TIGA_only (487)

Figure 8: Global distribution of the reprocessed GPS stations for IGS and TIGA–only.

59

GFZ AC

1234567589

31#44

1234
3565789A

1234D7F
6564C96DEA7A


7544D8F4
85A

A12B4567589
B12C489DE4
A565789A

46564
D69
484
3DA5ADA54

DA54!
DA54"""31#4441234D7F
6564C96DEA7A

4!
4"""

899546DD4
DA5A

75485A


Figure 9: The IGS reprocessing scheme is similar to GFZ routine IGS analysis processing scheme.
Its orbit and clock products are introduced and fixed for TIGA reprocessing to clean
the data. The final TIGA solution is the result of a NEQ stacking (clusters + IGS
reprocessing).

60

5 Reprocessing activities

50

20
IGS

15
Mean RMS [cm]overlap Mean RMS [cm]Repro1

40

30

20

5

10

0

10

1995

1997

1999

2001

2003

(a)

2005

2007

2009

2011

2013

0

1995

1997

1999

2001

2003

2005

2007

2009

2011

2013

(b)

Figure 10: Mean RMS values of IGS processing orbit overlaps (4 hours) [left] and of transformed
GFZ IGS reprocessing orbits w.r.t. the reprocessing (1994.0–2008.0) and the IGS
Final orbits (2008.0–2013.0) [right]. The solid line represents a 100–day median.

The TIGA data reprocessing is done in two steps, first precise satellite clocks, orbits and1–day normal equations are generated from the IGS REPRO2 using the IGS stations.
In the second step the TIGA stations, which are not already included in IGS REPRO2,
named TIGA–only stations, are processed. The IGS REPRO2 satellite clock and orbit
products are introduced and fixed to clean the observation data in PPP mode.
Because of the large number of the TIGA–only stations up to 2 sub–networks are buildand processed in network mode. The final TIGA solution is the result of a Normal Equation (NEQ) stacking of all sub–networks. For connecting the sub–networks 30 globally
distributed IGS REPRO2 stations are selected and processed together with the TIGA–
only sub–networks. The 30 connecting stations are different for each sub–network andare selected automatically from the IGS REPRO2 stations for each day according to its
distribution and post fit. If the number of TIGA REPRO2 stations is smaller than 250,
the TIGA–only stations will be processed with the IGS REPRO2 stations together as
TIGA final solution, and no sub–network is needed.
To quantify the internal consistency of the GPS satellite orbits, the overlap of 2 consecutive
1–day orbit arcs was checked. The daily mean RMS of the overlaps serve as quality
indicator, and are shown in Fig. 10(a) [left]. In the first year the RMS is on a level of
15-−50 cmand falls below 10 cmin 2012.
Since the Repro2 combination solutions are not available, the GFZ Repro2 orbits arecompared to Repro1 orbits (ig1 1994.0 – 2008.0) and the IGS Final orbits (igs 2008.0 –2013.0) by 7–parameter similarity transformations. The mean RMS of the transformed reprocessed orbits w.r.t. the ig1/igs orbits is shown in Fig. 10(b) [right]. The RMS decreases
rapidly from about 15 cm in 1994 to about 2 cm in the mid of 1995.

61

GFZ AC

6 Meta Data Management with SEMISYS
The precise analysis of GNSS observation data is based upon a variety of metadata fromdifferent sources, including station and satellite metadata. A high evaluation quality must
be ensured by the consistency and integrity of these meta information.
The station and satellite meta information are currently maintained in ASCII based files,
that makes the extraction of key information used for the data evaluation difficult. To
get rid of the restrictions caused by the file based metadata management, the Operational
Data Center (ODC) group of the GFZ developed a Sensor Meta Information System(SEMISYS) for the centralized, format independent and validated storage of station andsatellite metadata based upon a relational database.
The system is used for the handling of approximately 1600 stations analysed in different
projects (e.g. IGS, MGEX, TIGA, etc.) at GFZ. It contains the following meta information:• Station meta information extracted from IGS site logs,• Hardware meta information (receiver, antenna, radome) extracted from the IGS
rcvr_ant.tab, and IGS antenna.gra• Satellite parameter for the GNSS systems GPS, GLONASS, Galileo, BeiDou, QZSSand SBAS extracted from different sources (ANTEX, formats and specifications of
the satellite manufacturers).
• Notice advisories from GPS, GLONASS, and Galileo (NANU,NAGU)
Our approach leads to the following advantages:
1. Centralized, easy and fast on–demand access to all meta information concerning the
IGS station network,
2. Easy build–up of connections between metadata (finding similarities, differences or
specific information),
3. Easy maintenance of station meta information based on a web editor (no files necessary anymore),
4. Validation of all (and not only mandatory) site log entries(no confusion about formatting and units etc.),
5. Easy evaluation and exchange of the database generated site logs for all Analysis
Centres (AC’s),
6. Project across storage of station metadata(no invalid, inconsistent site logs of one
and the same station across different projects).
All necessary information can be accessed via web or command line and can thus be ideally62Referencesused for automated processing tasks.

References
Petit, G. and B. Luzum (Eds). IERS Conventions (2010). IERS Technical Note No. 36,
Verlag des Bundesamtes für Kartographie und Geodäsie, Frankfurt am Main, 2010.
Rodriguez–Solano, C. J., U. Hugentobler and P. Steigenberger. Adjustable box–wing model
for solar radiation pressure impacting GPS satellites. Advances in Space Research, 49(7):1113–1128, Elsevier, ISSN 0273–1177, 2012. doi: 10.1016/j.asr.2012.01.016. (software download from: http://www.iapg.bv.tum.de/albedo/).
Dilssner, F., T. Springer, G. Gienger and J. Dow. The GLONASS–M satellite yaw–attitude
model. Advances in Space Research, 47(1):160–171, 2011.
Uhlemann, M., M. Ramatschi, and G. Gendt. GFZ’s Global Multi–GNSS Network And
First Data Processing Results. IAG Scientific Assembly 2013, Potsdam, Germany,
2013.
Deng, Z., G. Gendt., and T. Schöne. Status of the IGS TIGA Tide Gauge data reprocessing
at GFZ. IAG Scientific Assembly 2013, Potsdam, Germany, 2013.
Montenbruck, O. Multi–GNSS Working Group. In: Meindl, M., R. Dach, Y. Jean (Eds):
IGS Technical Report 2012, IGS Central Bureau, pp. 163–170, 2012.
MacLeod, K.(Ed.) RINEX: The Receiver Independent Exchange Format, Version 3.02.
International GNSS Service (IGS), RINEX Working Group and Radio Technical Commission for Maritime Services Special Committee 104 (RTCM-SC104). IGS Central
Bureau. 2013.

63

GFZ AC64

GOP Analysis Center Report 2012–2013
J. Dousa and P. Vaclavovic
Geodetic Observatory Pecny
Research Institute of Geodesy,
Topography and Cartography,
Ondrejov 244, 250 65 Czech Republic
E-mail: jan.dousa@pecny.cz

1 Introduction
The Geodetic Observatory Pecny (GOP) Analysis Centre (AC) of the Research Instituteof Geodesy, Topography and Cartography (RIGTC) has contributed to the International
GNSS Service (IGS) since 2004 with a regular determination of the precise GPS ultra–
rapid products.
This technical report addresses two domains. First, the status of the core GOP AC
contribution to the IGS. Second, other activities related to the IGS working groups.

2 Contributions to the ultra–rapid products
The ultra–rapid orbits are determined using a highly efficient strategy of the 6-hour raw
data pre-processing followed by a consecutive normal equation stacking based on themodified Bernese GNSS Software Version 5.0 (Dach et al. 2007). Unfortunately, ouroriginal plan in 2013 to replace the software with the up–to–date release Ver. 5.2 was
not accomplished due to the lack of the manpower and an overall financial situation at
the GOP/RIGTC. Actually, most of this work was postponed for the next year. In spiteof the said problems, we were able to provide sufficient support to operate smoothly ourofficial contribution to the IGS over the whole period 2012–2013. A few problems occurred
only due to the data unavailability or due to internal IT problems, such as the processing
server hardware failure during the GPS week 1767. From the above reasons there were
no changes in the strategy or the network used in the GOP regular ultra–rapid productdetermination. The modifications thus consisted in regular updates of the satellites’ andreceivers’ antenna phase centre offset and variation model (IGS08_week.ATX) only.

65

GOP ACThe original GOP orbit end Earth rotation parameter products are available via the GOP
local data centre too:• ftp://ftp.pecny.cz/LDC/prod_GOP/GLOBAL/ORB/WWWW/gogWWWWD_HR.erp.Z• ftp://ftp.pecny.cz/LDC/prod_GOP/GLOBAL/ORB/WWWW/gogWWWWD_HR.sp3.Z

2.1 Experimental GLONASS ultra–rapid orbits and their exploitation
In parallel to the GOP contribution to the official IGS ultra–rapid GPS orbits, the second
GOP solution contributed to the IGS experimental GPS+GLONASS ultra–rapid orbits
operationally during the period of GPS weeks 1602–1712. This production was interrupted
in GPS week 1712 due to the repetitive problems with the GLONASS broadcast ephemeris.
We used the TEQC tool (Estey and Meertens 1999) for merging individual GPS andGLONASS ephemeris RINEXN files in the GOP data centre. A long unavailability ofthe software update fixing this specific problem generated too many manual interventions
which, in general, was the main reason to stop this parallel solution. Unfortunately, due tothe lack of the manpower we haven’t yet started this experimental solution and we decided
to postpone it until, first, we finalize the development of our own RINEX quality checking
tool for the multi-GNSS observations and navigation messages (G–Nut/Anubis, see below)
and, second, we update the Bernese GNSS Software to Version 5.2 (together with merging
our internal modifications from the previous version and adapting our complex system of
the processing for new formats and software functionalities).
Besides the generation of the GLONASS predicted orbits, GOP has regularly exploited
both IGS official (GPS) and unofficial (GPS+GLONASS) ultra–rapid products for nearreal–time zenith tropospheric path delay estimations since June 2001 and May 2011, respectively. Based on the long-term experience with the unofficial product we can statethat since the beginning it has provided stable and reliable quality for our operational
solution of sensing the troposphere in near real–time (Dousa and Vaclavovic 2013). Additionally, our results showed that the tropospheric parameters estimated using GPS and
GPS+GLONASS are of a comparable quality, while the latter even slightly better most
likely because of improved multi-GNSS geometry.

2.2 Quality monitoring for the orbit predictions
Since 2009, the IGS ultra–rapid orbits have been routinely monitored at GOP (available at
the web: http://www.pecny.cz → GNSS → precise orbits). The real–time portion of the
IGS ultra–rapid orbit predictions, which usually ranges between 3–10 hours, are compared(with a delay) to the IGS rapid orbits. However, the comparison process is running in realtime, thus reading all inputs at epochs when they become available meaning that any delayin the ultra–rapid product is implicitly included in the monitoring results. Additionally,
the comparison statistics are separated into hourly prediction intervals and dependency

66

3 IGS related developments and activities
graphs can visualize satellite specific degradations in the orbit prediction. More details
on the monitoring were provided in Dousa (2011) and the GOP AC summary in the IGS
Technical Reports 2011.

3 IGS related developments and activities
Due to the lack of the institutional financial support, the GOP had to concentrate to theproject-related works. The below are brief summaries of tasks we contributed (or we may
contribute in future) to individual IGS working groups and which have been supported bynational projects.

3.1 G–Nut/Anubis — development of new multi–GNSS monitoring tool
As described previously, with our aim to support a multi–GNSS ultra–rapid product development (at least for GPS, GLONASS and Galileo soon), we needed a flexible tool for thedata quality checking for all future GNSS observations. Together with the development of
the G–Nut software library (Vaclavovic et al. 2013) for various end-user applications, we
could initiate a project that uses part of the library for the above requirements. The firstrelease of the G–Nut/Anubis tool was made available to public in July 2013 (Vaclavovic
and Dousa 2013) through the web: http://www.pecny.cz → GNSS → software. The
current version supports reading RINEX 2.11 and RINEX 3.02 formats and includes functionality such as a) header data monitoring, b) quantitative data monitoring – numberof observations, signals, satellites, frequencies/bands, data gaps, small data pieces andothers; all with respect to header information and real data content, c) qualitative data
monitoring – cycle slip and clock jump detection, code multipath and noise estimation, d)standard point positioning and satellite azimuth/elevation calculation.
The tool supports observations from all GNSS (GPS, GLONASS, Galileo, BeiDou) andtheir augmentations (SBAS, QZSS). While the quantitative monitoring statistics are provided to all above mentioned constellations, the limits still remain in the support of navigation messages from the Chinese BeiDou system and from the augmentation satellites
including relevant algorithms for the observation pre-processing. On the other hand, we
have developed a new generic algorithm for the code multipath and noise monitoring for all
available constellations, frequencies/bands and signals, details are provided in Vaclavovic
and Dousa (2013). The tool has been tested on the data available from the IGS M-GEX
and EUREF experimental campaigns. The example plots showing a year history for two
stations from the EUREF permanent network is provided in Fig. 1

67

GOP ACAXPV - code multipath [EURv3]
60

GPSM5X
GPSM2X
GPSM2W
GPSM1C
GLOM2P
GLOM2C
GLOM1P
GLOM1CGALM8XGALM7XGALM5XGALM1XBDSM7I
BDSM6I50
40

Code MP [cm]

30

Jan

Feb

Mar

Apr

May

Jun

Jul

Aug

Sep

Oct

Nov

20
10
0

Dec

2013

BSCN - code multipath [EURv3]
60

GPSM5X
GPSM5Q
GPSM2X
GPSM2W
GPSM2S
GPSM1C
GLOM2P
GLOM1CGALM8QGALM7XGALM7QGALM5XGALM5QGALM1XJan

50
40

Code MP [cm]

30

Feb

Mar

Apr

May

Jun

Jul
2013

Aug

Sep

Oct

Nov

20
10
0

Dec

Figure 1: Pseudorange multipath estimated for all GNSS signals observed at the EUREF station
AXPV (top) and BSCN (bottom) during January–November, 201368

3 IGS related developments and activities
IGS01

ZTD Bias [mm]

25

IGS02

CNS91

20
15
10
5

METS0

NICO0

ONSA0

PDEL0

POTS0

REYK0

TUBO0

VIS00

WTZR0

ZIM20

NICO0

ONSA0

PDEL0

POTS0

REYK0

TUBO0

VIS00

WTZR0

ZIM20

MATE0

METS0

IGS02

MALL0

KIR00

ISTA0

HOFN0

HERT0

GOPE0

DENT0

CASC0

BUCU0

BRST0

IGS01

25
ZTD StdDev [mm]

BOR10

BELF0

0

CNS91

20
15
10
5

MATE0

MALL0

KIR00

ISTA0

HOFN0

HERT0

GOPE0

DENT0

CASC0

BUCU0

BRST0

BOR10

BELF0

0

Figure 2: Tefnut ZTD comparisons with respect to EUREF final products – biases (left) andstandard deviations (right)

3.2 Real–time troposphere products based on IGS Real–Time Service
Since 2012, the GOP has been developing the G–Nut/Tefnut and G–Nut/Geb applications to apply the Precise Point Positioning (Zumberge et al. 1997) for the tropospheremonitoring and the positioning, respectively, both in the post–processing and real–timemodes. In February 2013, we initiated an experimental real–time GNSS data processing
campaign for 18 European and 18 global stations in the preparation of supporting existingor future meteorological applications. The IGS01, IGS02 real–time precise orbit and clock
products from the IGS (Caissy et al. 2012) as well as from individual global product fromthe CNES (Laurichesse 2011) were operationally exploited in this campaign.
The assessment of the real–time zenith path delays, see Fig. 2 and results are in detail
discussed in Dousa and Vaclavovic (2014). Together with the monitoring of coordinate
residuals in a pseudo–kinematic positioning mode, it revealed that the quality of theindividual CNES real–time product is slightly better than the quality of any IGS combined
product. This indicates a room for a possible improvement in the combination process.

69

GOP ACOn the other hand, no overall differences between combined products applying either
the epoch-wise combination or the Kalman filtering were observed and thus no generalpreference on individual product use identified.

3.3 GOP-TropDB – development of troposphere evaluation tool
The GOP-TropDB high-performance databased development was initiated at GOP in 2011as a tool of the third generation for an intra–/inter–technique tropospheric parameter comparisons. At the IGS workshop in Olsztyn, it was recognized as a suitable instrument for a
flexible automated comparison within the IGS Troposphere WG in future. From this time
we consult our developments and planned functionalities with the Tropospheric WG Chair,
Dr. Christine Hackmann from USNO. The GOP-TropDB implementation and technicalaspects were provided in Dousa and Gyori (2013). During 2013, the database was tested
with preliminary inclusion of tropospheric products from space geodetic techniques (GNSS,VLBI, DORIS), meteorological observations (radio sounding, water vapour radiometers,
in-situ measurements) as well as numerical weather model data fields. A feedback was also
provided about specific problems in the IGS final tropospheric product. Finally, a special
attention was given to the development of the more accurate tropospheric wet delay ties
in order to support as much as precise comparison for collocated station from various
observing techniques in particular with significant differences in altitudes. The extension
towards new auxiliary data and models (EGM2008, GPT2, etc.), support of data fromnumerical weather fields, definition of new tropospheric ties, and finally, initial examples
already demonstrating basic database functionalities were provided in Gyori and Dousa(2013).

Acknowledgement
The development of the G–Nut/Anubis tool for multi-GNSS observation and navigation
data monitoring was partly supported by the project of the Czech Ministry of Eduction,
Youth and Science (No. TB01CUZK006). The development of the G–Nut/Tefnut and
G–Nut/Geb applications for the real–time troposphere and position estimation and the
GOP–TropDB were supported by the Czech Science Foundation (No. P209/12/2207).

References
Caissy, M., L. Agrotis, G. Weber, M. Hermandez-Pajares, and U. Hugentobler. Comming
Soon: The International GNSS Real-Time Service. GPS World, 2012.
Dach, R., U. Hugentobler, P. Fridez, and M. Meindl (eds). Bernese GPS Software Version
5.0. Astronomical Institute, University of Berne, Berne, Switzerland, 2007.

70

References
Dousa, J. The impact of errors in predicted gps orbits on zenith troposphere delay estimation. GPS Solutions, 13(3):229–239, 2011. doi:10.1007/s10291-009-0138-z.
Dousa, J. and G. Gyori. Database for tropospheric product evaluations – implementation
aspects. Geoinformatics FCE CTU, 10:39–52, 2013. URL http://geoinformatics.
fsv.cvut.cz/pdf/geoinformatics-fce-ctu-2013-10.pdf.
Dousa, J. and P. Vaclavovic. Evaluation of ground-based gnss tropospheric products at
geodetic observatory pecny. (accepted in the IAG Symposia Series), 2013.
Dousa, J. and P. Vaclavovic. Real–time zenith tropospheric delays in support of numerical
weather prediction applications. J. Adv. Space Res., (available online 1 March 2014),
2014.
Estey, L.H. and C.M. Meertens. TEQC: The Multi–Purpose Toolkit for GPS/GLONASS
Data. GPS Solut, 3(1):42–49, 1999.
Gyori, G. and J. Dousa. GOP–TropDB developments for tropospheric product evaluationand monitoring — design, functionality and initial results. (accepted in the IAG
Symposia Series), 2013.
Laurichesse, D. The CNES Real-time PPP with undifferenced integer ambiguity resolution
demonstrator. In Proceedings of the ION GNSS 2011, September 2011, Portland,
Oregon, 2011.
Vaclavovic, P. and J. Dousa. G–Nut/Anubis — open–source tool for multi–GNSS data
monitoring with a multipath detection for new signals, frequencies and constellations.
(accepted in the IAG Symposia Series), 2013.
Vaclavovic, P., J. Dousa, and G. Gyori. G–Nut software library — state of development
and first results. Acta Geodynamica et Geomaterialia, 10(4):431–436, 2013.
Zumberge, J.F., M.F. Heflin, D.C. Jefferson, M.M. Watkins, and F.H. Webb. Precise point
positioning for the efficient and robust analysis of GPS data from large networks. J
Geophys Res, 102(B3):5005–5017, March 1997.

71

CNES/CLS Analysis Center Technical Report 2013
S. Loyer1 , F. Perosanz2 , F. Mercier2 ,H. Capdeville1 , A. Mezerette1 , and J.–C. Marty2
1
2

Collecte Localisation Satellites, 31520 Ramonville Saint Agne, FranceCentre National d’Etudes Spatiales, 31400 Toulouse, France

1 Introduction
Our contribution is limited to “final” GPS and GLONASS products. We process zero–difference GNSS observations using the GINS CNES/GRGS software (Melachroinos et al.
2011) and the processing strategy described in Loyer et al. (2012). More information on
our AC activity can also be found at: http://www.igsac-cnes.cls.fr.
Users wishing to use GRG GPS orbit and clock products in order to fix phase ambiguities
to integer values in a PPP mode (Laurichesse and Mercier 2007) should apply Wide–Lane
Satellite Biases (WSB) to their observations as described in Fund et al. (2013). TheseWSB are available at: ftp://ftpsedr.cls.fr/pub/igsac.

2 GRG products evolution
The major evolution in the routine processing concerns LOD products which were rejectedfrom the combination due to their high noise level. The reason has been identified andwas due to a high correlation between this parameter and the empirical accelerations
we were estimating (cf. http://acc.igs.org/orbits/srp-models_cnes_egu11.pdf). A
new SRP model associated to a different parameterization is under development. In themeantime, we decided week 1759, to stop estimating 1/rev term in the sun direction forblock–IIA satellites. The LOD solution improvement is clear in Fig. 1 and GRG products
are now contributing to the combination.

72

3 Changes to models, standards and processing strategy

Figure 1: Starting week 1759, GRG LOD series noise is significantly reduced. (Courtesy of
J. Griffiths NOAA/NGS http://acc.igs.org)

3 Changes to models, standards and processing strategy
Most of the models and standards changes were motivated by the preparation for the
REPRO2 reprocessing campaign. The more noticeable points are listed in Tab. 1.
Time Variable Gravity (TVG) field clearly impacts LEO orbit precision (Cerri et al.
(2010) & (2013)). The impact on MEO orbits should be small but cannot be neglected mainly through its aliasing with semi–annual and annual geophysical signals(Melachroinos et al. 2013). We choose the EIGEN6–S model (http://grgs.obs-mip.fr/
Table 1: Major model evolution
Model

Description

Gravity field

EIGEN6–S including secular rates+ annual/ semi–annual terms up to degree 12
FES2012, gravity field+station loading
Second order from IERS2010 & IGRF2011(TEC from IGS/IGR–iono grids)
GPT2 for P, T, RH & VMF1 mapping function coefficients
Applied for GPS satellites using conventional powertransmission values

Ocean tides
Ionospheric correction
Tropospheric correction
Antenna thrust73

CNES AC
2nd order Ionospheric correction (iono-free phase)(Hernandez-Pajares test case: one curve per pass)

12

computed with Gins routines and Ionex Code values

9
mm

6
3
0
12

computed from observations and P1-P2 biaises (reference)

mm

9
6
3

mm

0
4
2
0
-2
-4

differences

0

20000

40000
seconds in the day

60000

80000

Figure 2: Comparison of second order ionospheric range corrections computed from a reference
model with the GINS’s implementation.

grace/variable-models-grace-lageos/mean_fields) and associated de–aliasing products as a reference for the REPRO2 campaign. The corresponding ocean loading model
for both gravity field and station loading displacement computation is FES2012 (Carrere
et al. 2012).
In order to validate the implementation of the second order ionospheric correction, we used
the test case provided by Hernández–Pajares et al. (2007). Fig. 2 compares his reference
model to the GINS’s approach based on IONEX maps. The difference between the two(down plot) is below the millimeter level.
Antenna thrusts are taken into account for GPS satellites only as no published values
exist for GLONASS and Galileo. Two orbit solutions with and without considering thiseffect are compared in Fig. 3. The main impact is a negative bias of the satellite radial
components of around 4 mm for blocks IIA/IIR and of around 8 mm for blocks IIR–M
and II–F.
In the framework of our investigations on solar radiation pressure models, we have implemented the capability to use the sub–solar point for the phase origin of the computationof sinusoidal empirical accelerations.
Last but not least, the entire processing chain has been moved to a new CNES computing74

References(with vs w/o antenna thrust)
along
10

mm

5
0
-5
-10
-15

2.3e+04

2.3e+04

2.3e+04

Cross
10

mm

5
0
-5
-10
-15

22966.0

22966.5

22967.0

radial10mm

50IIA / IIR-A / IIR-B

-5
-10
-15

IIR-M / IIF
22966.0

22966.5

22967.0

Figure 3: Along–track, Cross–track and Radial orbit comparison with and without taking into
account antenna thrust.

facility based on a 1168 core LINUX cluster.

4 IGS M–GEX campaign data analysis
Our contribution to the IGS M–GEX experiment focuses on the Galileo satellites orbit
and clock computation as well as on the Galileo signals biases determination. Data froma global network of more than 50 stations are processed on a routine basis. GRG Galileo
orbit and clock products (called “GRM”) are available at: ftp://cddis.gsfc.nasa.gov/
pub/gps/products/mgex.
Future Galileo satellites and ground tracking stations data will be included in the processing as soon as will become available.

References
Cerri, L., J.P. Berthias, W.I. Bertiger, B.J. Haines., F.G. Lemoine, F. Mercier, J.C. Ries,
P. Willis, N.P. Zelensky, M. Ziebart. Precision orbit determination standards for the
Jason series of altimeter missions. Marine Geodesy, 33(1):379–418, 2010.
Cerri, L., J.M. Lemoine, F. Mercier, N.P. Zelensky, and F.G. Lemoine. DORIS–based

75

CNES ACpoint mascons for the long term stability of precise orbit solutions. Advances in Space
Research, 52(3):446–476, 2013.
Fund, F., F. Perosanz, L. Testut, and S. Loyer. An Integer Precise Point Positioning
technique for sea surface observations using a GPS buoy. Advances in Space Research,
51(8):1311–1322, 2013. http://dx.doi.org/10.1016/j.asr.2012.09.028
Hernández–Pajares, M., J.M. Juan, J. Sanz, and R. Orús. Second–order ionosphericterm in GPS: implementation and impact on geodetic estimates. J Geophys Res,
112(B08417), 2007.
Laurichesse, D. and F. Mercier. Integer ambiguity resolution on undifferenced GPS phasemeasurements and its application to PPP. ION GNSS 2007 20th International Technical Meeting of the Satellite Division, 25–28 September 2007, Fort Worth, TX, pp. 839–
848, 2007.
Loyer, S., F. Perosanz, F. Mercier, H. Capdeville., and J–C. Marty. Zero–difference GPS
ambiguity resolution at CNES–CLS IGS Analysis Center. Journal of Geodesy, 86(11):991–1003, 2012. doi: 10.1007/s00190--012--0559--2, Published on line: 03 April, 2012.
Carrere, L., F. Lyard, M. Cancet, L. Roblou, and A. Guillot.
FES2012:a new tidal model taking advantage of nearly 20 years of altimetry measurements. http://www.aviso.oceanobs.com/fileadmin/documents/OSTST/2012/
oral/01_thursday_27/03_tides/04_TID_Carrere2.pdf
Marty, J.C., S. Loyer, F. Perosanz, F. Mercier, G. Bracher, B. Legresy, L. Portier,
H. Capdeville, F. Fund, J.M. Lemoine, and R. Biancale. GINS: the CNES/GRGSGNSS scientific software. 3rd International Colloquium Scientific and Fundamental
Aspects of the Galileo Programme, ESA Proceedings WPP326, 31 Aug.– 2 Sep. 2011,
Copenhagen, Denmark, 2011.
Melachroinos, S.A., F.G. Lemoine, D.S. Chinn, N.P. Zelensky, J.B. Nicholas, andB.D. Beckley. The effect of seasonal and long–period geopotential variations on the
GPS orbits. GPS Solutions, 2013. doi: 10.1007/s10291--013--0346--4, published online 27 Nov. 2013.

76

JPL IGS Analysis Center Report 2013
S. Desai, W. Bertiger, B. Haines, D. Kuang,
C. Selle, A. Sibois, A. Sibthorpe, and J. Weiss
Jet Propulsion Laboratory
California Institute of Technology
4800 Oak Grove Drive, M/S 238-600
Pasadena, CA 91001, U.S.A.
E-mail: shailen.desai@jpl.nasa.gov
Tel. +1–818–354–6102

1 Introduction
In 2013, the Jet Propulsion Laboratory (JPL) continued to serve as an Analysis Center(AC) for the International GNSS Service (IGS). We contributed orbit and clock solutions
for the GPS satellites, position, clock and troposphere solutions for the ground stations
used to determine the satellite orbit and clock states, and estimates of Earth rotation
parameters (length–of–day, polar motion, and polar motion rates). This report summarizes the activities at the JPL IGS AC in 2013 and our preparations for the 2014 IGS
reprocessing campaign.
Tab. 1 summarizes our contributions to the IGS Rapid and Final products. All of our conTable 1: JPL AC Contributions to IGS Rapid and Final Products.

Product

Description

Rapid/Final

jplWWWWd.sp3
jplWWWWd.clk
jplWWWWd.tro
jplWWWWd.erp
jplWWWWd.yaw
jplWWWWd.snx
jplWWWW7.sum

GPS orbits and clocks
GPS and station clocks
Tropospheric estimates
Earth rotation parameters
GPS yaw rate estimates
Daily SINEX file
Weekly solution summary

Rapid & Final
Rapid & Final
Rapid & Final
Rapid(d=0–6), Final(d=7)
Rapid & Final
Final
Final

77

JPL ACtributions are based upon daily solutions centered at noon and spanning 30–hours. Each ofour daily solutions is determined independently from neighboring solutions, namely without applying any constraints between solutions. We have been delivering daily SINEX
files starting with GPS week 1702.
The JPL IGS AC also generates Ultra–Rapid orbit and clock products for the GPS constellation (Weiss et al. 2010). These products are generated with a latency of less than
2 hours and are updated hourly. Although not submitted to the IGS, our Ultra–Rapid
products are available in native GIPSY formats at:
ftp://sideshow.jpl.nasa.gov/pub/JPL_GPS_Products/Ultra.

2 Processing Software and Standards
The JPL AC continues to utilize the GIPSY/OASIS software package to generate our contributions to the IGS. Starting GPS week 1738 (April 28, 2013), we used GIPSY/OASIS
version 6.2 to generate our IGS contributions. A complete description of our current processing approach can be found at: http://igscb.jpl.nasa.gov/igscb/center/analysis/
jpl.acn. Of note, we continue to use empirical GPS solar radiation pressure models developed at JPL instead of the DYB–based strategies that are commonly used by other
IGS analysis centers. This choice is based upon an extensive evaluation of various internal and external metrics after testing both approaches with the GIPSY/OASIS software(Sibthorpe et al. 2011).

3 Preparations for 2014 IGS Reprocessing Campaigns
In November 2012 we completed a preliminary reanalysis of historical GPS data from August 16, 1992 to present in the IGS08 reference frame, and made these products publicallyavailable (Desai et al. 2011). They are available at:• ftp://sideshow.jpl.nasa.gov/pub/jpligsac in IGS formats, and• ftp://sideshow.jpl.nasa.gov/pub/JPL_GPS_Products/Final in GIPSY formats.

A notable benefit of these preliminary reprocessed IGS08–products is that they include ourso–called “wide–lane phase bias” (WLPB) file for the entire time span of the products. The
WLPB files enable single–receiver phase ambiguity resolved positioning when used with
the GIPSY/OASIS software (Bertiger et al. 2010) and our GPS orbit and clock products.
Also of note, high–rate (30–second) GPS clock products in native GIPSY format were also
generated in this preliminary reanalysis for the period May 5, 2000 to present. They arealso generated operationally in native GIPSY format for our Rapid and Final solutions.

78

References
Our contributions to the 2014 reprocessing campaign are expected to benefit from theresults and experience gained from our preliminary analysis. Over the course of 2013 wetested various modifications to our processing standards that we will implement for the2014 reprocessing campaign, as well as operations. These modifications include:• Application of second order ionospheric corrections (Garcia–Fernandez et al. 2013).

• Revised empirical solar radiation pressure model named GSPM13, following Sibthorpe
et al. (2010).
• Antenna thrust models per IGS recommendations.

• Modern ocean tide loading, using GOT4.8 (Ray 2013) (appendix) instead of FES2004(Lyard et al. 2006).
• GPT2 troposphere models and mapping functions (Lagler et al. 2013).
• Elevation–dependent data weighting.

We will deliver the full suite of products listed in Tab. 1 to the 2014 IGS reprocessing
campaign, and also include high–rate (30–second) GPS clock products for May 5, 2000
onwards. We also plan to include high–rate (30–second) GPS clock products in our operational deliveries to the IGS when our new processing standards become operational.

4 Future Activities
Our primary focus in 2014 is to support the second IGS reprocessing campaign and existing
operations.

5 Acknowledgments
The work described in this report was performed at the Jet Propulsion Laboratory, California Institute of Technology under a contract with the National Aeronautics and Space
Administration.

References
Bertiger, W., S. Desai, B. Haines, N.Harvey, A. Moore, S. Owen, and J. Weiss. Single
receiver phase ambiguity resolution with GPS data. J. Geodesy 84(5):327–337, 2010.
doi:10.1007/s00190–010–0371-9.
Desai, S. D., W. Bertiger, B. Haines, J. Gross, N. Harvey, C. Selle, A. Sibthorpe, and79

JPL ACJ. P. Weiss. Results from the Reanalysis of Global GPS Data in the IGS08 Reference
Frame. Fall AGU, San Francisco, CA, December 5–9, 2011.
Garcia–Fernandez, M., S. D. Desai, M. D. Butala, and A. Komjathy. Evaluation of different
approaches to modeling the second–order ionosphere delay on GPS measurements.
J. Geophys. Res. 118(12):7864–7873, 2013. doi:10.1002/2013JA019356.
Lagler, K. M. Schindelegger, J. Bohm, H. Krasna, and T. Nilsson. GPT2: Empirical slantdelay model for radio space geodetic techniques. Geophys. Res. Lett. 40(6):1069–1073,
2013. doi:10.1002/grl.50288.
Lyard, F., F. Lefevre, T. Letellier, and O. Francis, Modeling the global ocean tides:
Insights from FES2004. Ocean Dyn., (56):394–415, 2006. doi:10.1007/s10236–006–
0086–x.
Ray, R. D., Precise comparisons of bottom–pressure and altimetric ocean tides. J. Geophys. Res., 118:4570–4584, 2013. doi:10.1002/jgrc.20336.
Sibthorpe, A., J. Weiss, N. Harvey, D. Kuang, and Y. Bar–Sever. Empirical modeling ofsolar radiation pressure forces affecting GPS satellites. Fall AGU, San Francisco, CA.,2010.
Sibthorpe, A., W. Bertiger, S. D. Desai, B. Haines, N. Harvey, and J. P. Weiss. An
evaluation of solar radiation pressure strategies for the GPS constellations. J. Geodesy,
85(8):505–517, 2011. doi:10.1007/s00190–011–0450–6.
Weiss, J. P., W. Bertiger, S. D. Desai, B. J. Haines, and C. M. Lane. Near real time GPS
orbit determination: Strategies, performance, and applications to OSTM/Jason–2.
Adv. Astronaut. Sci., 137:439–452, 2010.

80

United States Naval Observatory (USNO)
Analysis Center Report 2013
C. Hackman, S. M. Byram, V. J. Slabinski,
J. C. Tracey, and J. R. Rohde
United States Naval Observatory
3450 Massachusetts Avenue Northwest
Washington DC 20392, USA
E-mail: christine.hackman@usno.navy.mil
Tel. +1–202–762–1428

1 Introduction
The United States Naval Observatory (USNO), located in Washington, DC, USA has
served as an IGS Analysis Center (AC) since 1997, contributing to the IGS Rapid andUltra–rapid Combinations since 1997 and 2000, respectively. USNO contributes a fullsuite of rapid products (orbit and clock estimates for the GPS satellites, earth rotation
parameters (ERPs), and receiver clock estimates) once per day to the IGS by the 1600
UTC deadline, and contributes the full suite of ultra–rapid products (post–processed andpredicted orbit/clock estimates for the GPS satellites; ERPs) four times per day by thepertinent IGS deadlines.
USNO has also coordinated IGS troposphere activities since 2011, producing the IGS Final
Troposphere Estimates and chairing the IGS Troposphere Working Group (IGS TWG).
The USNO AC is hosted in the GPS Analysis Division (GPSAD) of the USNO Earth Orientation Department (EOD). Dr. Christine Hackman, GPSAD chief, directs AC activities,
chairs the IGS TWG, and serves on the IGS Governing Board. Dr. Sharyl Byram oversees production of the IGS Final Troposphere Estimates. All GPSAD members, including
Dr. Victor Slabinski, Mr. Jeffrey Tracey and contractor Mr. James R. Rohde, participate
in AC work.
USNO AC products are computed using Bernese GPS Software (Dach et al. 2007)1 . Rapid
products are generated using a combination of network solutions and precise point posi1

Prior to 2009, the rapid products were computed using Jet Propulsion Laboratory (JPL) GPS Inferred
Positioning System (GIPSY ) (Webb and Zumberge 1997).

81

USNO ACtioning (PPP; Zumberge et al. (1997)). Ultra–rapid products are generated using network
solutions. IGS Final Troposphere Estimates are generated using PPP.
GPSAD also generates a UT1–UTC–like value, UTGPS, five times per day. UTGPS isa GPS–based extrapolator of VLBI–based UT1–UTC measurements. The IERS2 Rapid
Combination/Prediction Service uses UTGPS to improve post–processed and predicted
estimates of UT1–UTC. Mr. Tracey oversees UTGPS.
USNO rapid, ultra–rapid and UTGPS products can be downloaded immediately after computation from http://www.usno.navy.mil/USNO/earth-orientation/gps-products. IGS
Final Troposphere Estimates can be downloaded at ftp://cddis.gsfc.nasa.gov/gps/
products/troposphere/zpd.

2 Developments and Product Performance in 2013
The precision of USNO ultra–rapid products improved markedly in 2013 due to (a) lengthening of the data–observation window used for orbit/clock prediction from 27 hours to 40
hours and (b) strengthening of the geodetic ties to the IGb08 reference frame. Item (b)processing changes were implemented in USNO rapid processing as appropriate, improving
several of the rapid products as well.
Figs. 1–4 show the 2013 performance of USNO rapid and ultra–rapid GPS products, withsummary statistics given in Tab. 1. USNO rapid orbits had a median weighted RMS(WRMS) of 16 mm with respect to the IGS rapid combined orbits. The USNO ultra–
rapid orbits had median WRMSs of 17 mm (24–h post–processed segment) and 37 mm (6–h predict) with respect to the IGS rapid combined orbits, reductions of 23–24% comparedto the 2012 22/49 mm past/predict median WRMS differences.
USNO rapid (post–processed) and ultra–rapid 6–h predicted clocks had median 146 ps
and 1902 ps RMSs with respect to IGS combined rapid clocks, with the median RMS of
the ultra–rapid clocks reduced 35% from the 2012 value of 2929 ps.
USNO rapid polar motion estimates had (x, y) 130 and 99 micro arc sec RMS differenceswith respect to IGS rapid combined values. These RMS differences were 22% and 49%
improved over the 2012 (166, 195) RMS difference values. USNO ultra–rapid polar motion
estimates differed (RMS; x, y) from IGS rapid combined values by 79 and 116 micro arc
sec for the 24–h post–processed segment, 55% and 49% improved over the 2012 (175,226) RMS–difference values. The USNO ultra–rapid 24–h predict–segment values differed(RMS; x, y) from the IGS rapid combined values by 336 and 277 micro arc sec, 5% and
13% improved over the 2012 (355, 319) values.
The USNO AC began incorporating measurements from the Russian GLONASS GNSS
into processing in 2011 Byram and Hackman (2012a) and (2012b) and has been com2

International Earth Rotation and Reference Systems Service82

2 Developments and Product Performance in 2013
WRMS, USNO GPS Orbits WRT IGS Rapid Combined Orbits
WRMS, USNO GPS Orbits WRT IGS Rapid Combined Orbits

150

150
Median (mm):Medianrapid:
16(mm):
rapid:past:
16 17
ultra,
ultra, past: 17
ultra, pred: 37
ultra, pred: 37mmmm100100

50 50

0

0

0

0

50

50

100

100

150

150

200
250
200
250
day of year 2013

300

300

350

350

400

400

day of year 2013
ultra, predultra, past

rapid

ultra, predultra, past

rapid

Fig. 1.Figure
Weightedof USNOorbit estimates
respectwith
to IGS
RapidtoCombination,2013. “Ultra,
1: RMS
Weighted
RMSGPSof USNOGPS orbitwith
estimates
respect
IGS Rapid Combination,past” refers to 24-hour
post-processed
sectionof
USNO
ultra-rapid
orbits.
“Ultra,pred”
referstofirst six hours
2013. “Ultra, past” refers to 24–hour post–processed section of USNO ultra–rapidof ultra-rapid orbit
prediction.
orbits. “Ultra, pred” refers to first six hours of ultra–rapid orbit prediction.
RMS, USNO GPS Clock Estimates WRT IGS Rapid Combined Clocks
6000
Median (ps):rapid: 146
ultra, pred: 1902

ps

4000

2000

0
0

50

100

150

200
250
day of year 2013

rapid

300

350

400

ultra, predFig. 2. RMS of USNO GPS rapid clock estimates and ultra-rapid clock predictions with respect to IGS Rapid
Figure 2:
RMS of USNO GPS rapid clock estimates and ultra–rapid clock predictions with reCombination,
2013.
spect to IGS Rapid Combination, 2013.

483

USNO AC

USNO Rapid Polar Motion WRT IGS Rapid Combined400
RMS (x, y, micro arc sec): 130, 99

300

micro arc sec

200
100
0
-100
-200
-300
-400
0

50

100

150

200
250
day of year 2013
dx, rapid

300

350

400

dy, rapid

Figure 3: USNO rapid polar motion estimates minus IGS Rapid Combination values, 2013.

USNO Ultra-Rapid Polar Motion WRT IGS Rapid Combined1000
RMS (x, y, micro arc sec): past: 79, 116; pred: 336, 277

micro arc sec

500

0

-500

-1000
0

50

100

150

200
250
day of year 2013

dx, preddy, preddx, past

300

350

400

dy, past

Figure 4: USNO ultra–rapid polar motion estimates minus IGS Rapid Combination values, 2013.

84

2 Developments and Product Performance in 2013
Table 1: Precision of USNO Rapid and Ultra–Rapid Products: 1 Jan. – 31 Dec. 2013. All
statistics computed with respect to IGS Combined Rapid Products
USNO GPSsatellite orbits

USNO GPS–basedpolar motion estimates

USNO GPS–based
clock estimates

Statistic: median weighted
RMS difference
units: mm

Statistic: RMS difference

Statistic: medianRMS difference
units: ps

rapid

dates

1/1/2013 –12/31/2013

16

units: 10–6 arc sec

ultra–rapid

rapid

past 24h

6h predict

17

37

ultra–rapid

x: 130
y: 99

rapid

ultra–rapid

past 24h

24h predict

past 24h

6h predict

x: 79
y: 116

x: 336
y: 277

146

1902

Table 2: Precision of USNO Ultra–Rapid GPS+GLONASS Test Products: 1 Jan – 31 Dec 2013.
Orbit statistics computed with respect to IGV Combined Ultra–Rapid GPS+GLONASS
Products. Polar motion statistics computed with respect to past–24–hr segment of IGU
GPS–only values
USNO GLONASS
satellite orbits
Median RMS of 7–parameter
Helmert transformation
units: mm

USNO GPS+GLONASS
polar motion estimates
RMS difference
units: 10–6 arc sec

dates

past 24h

6h predict

6/27/2013 – 12/31/2013

50

117

past 24h
x: 105, y: 69

puting a full set of test rapid and ultra–rapid combined GPS+GLONASS products since2012. These estimates are not yet submitted to the IGS. In the second half of 2013,seven–parameter Helmert transformations computed between USNO and IGS ultra–rapid
GLONASS orbits had median RMSs of 50 and 117 mm for the 24–h post–processed and
6–h predict portions, respectively. Meanwhile, the USNO GPS+GLONASS ultra–rapid
24–h post–processed polar motion values differed from the 24–hr post–processed segmentof the IGS ultra–rapid GPS–only (aka IGU) values, RMS, by 105 and 69 micro arc sec,
respectively. These data are shown in Tab. 2/Figs.5–6.
The USNO AC acquired Bernese GNSS Software Ver. 5.2 in 2013 and plans to release
official AC products generated using it in 2014.

85

USNO ACRMS of 7-Par Helmert Transform btwn USNO and IGS Ultra-Rapid GLO Orbits
350
Median (mm): ultra, past: 50; ultra, pred: 117

300
250

mm

200
150
100
50
0
0

50

100

150

200
250
day of year 2013

ultra, pred

300

350

400

ultra, past

Figure 5: RMS of USNO ultra–rapid GLONASS orbit estimates with respect to IGS Combined
Ultra–rapid GLONASS orbits, 2013. “Ultra, past” refers to 24–hour post–processed
section of USNO ultra–rapid orbits. “Ultra, pred” refers to first six hours of ultra–
rapid orbit prediction. Helmert transformations computed using Bernese GPS Software Ver. 5.0.
USNO Test GPS+GLONASS Ultra-Rapid Polar Motion WRT IGU
24-h post-processed segments compared300
RMS (x, y, micro arc sec): 105, 69

200

micro arc sec

100

0

-100

-200

-300
0

50

100

150

200
250
day of year 2013

dx, past

300

350

400

dy, past

Figure 6: Difference between 24–h post–processed polar motion estimates in USNO test ultra–
rapid GPS+GLONASS solution and IGS “IGU” GPS–only ultra–rapid solution, 2013.

86

References

References
Byram, S. and C. Hackman. GNSS–Based Processing at the USNO: Incorporation of
GLONASS Observations. IGS Workshop 2012, Olstzyn, Poland, 2012a.
Byram, S. and C. Hackman. High–Precision GNSS Orbit, Clock and EOP Estimation at
the United States Naval Observatory. Proc. 2012 IEEE/ION Position Location andNavigation Symposium, 659-63, 2012b.
Dach, R., U. Hugentobler, P. Fridez, and M. Meindl (eds). Bernese GPS Software Version
5.0 (User Manual). Astronomical Institute of University of Bern, Switzerland, 2007.
Webb, F.H. and J.F. Zumberge (eds). An Introduction to GIPSY/OASIS–II: Precision
Software for the Analysis of Data from the Global Positioning System. JPL internal
publication D–11088, Jet Propulsion Laboratory, Pasadena, California, 1997.
Zumberge, J.F., M.B. Heflin, D.C. Jefferson, M.M. Watkins, and F.H. Webb. Precise Point
Positioning for the Efficient and Robust Analysis of GPS Data from Large Networks.
J. Geophys. Res., 102(B3):5005–17, 1997.

87

USNO AC

88

EUREF Permanent Network
C. Bruyninx1 , E. Brockmann2 , H. Habrich3 , A. Kenyeres4 ,W. Söhne3 , G. Stangl5 , K. Szafranek6 , and C. Völksen7
1
2
3
4
5
6
7

Royal Observatory of Belgium (ROB), Av. Circulaire 3,1180 Brussels, Belgium, E–mail: C.Bruyninx@oma.be
Bundesamt für Landestopografie swisstopo, Seftigenstrasse 264,
3084 Wabern, Switzerland
Bundesamt für Kartographie und Geodäsie (BKG),
Richard–Strauss–Allee 11, 60598 Frankfurt am Main, Germany
FOMI Satellite Geodetic Observatory, 1592 Budapest,
P.O. Box 585, Hungary
Institute for Space Research, Schmiedlstr. 6, 8042 Graz, Austria
Military University of Technology, Gen. Sylwestra Kaliskiego 2,
00–908 Warsaw, Poland
Bavarian Academy of Sciences and Humanities,
Alfons–Goppel–Str. 11, 80539 München, Germany

1 Introduction
The IAG (International Association of Geodesy) Regional Reference Frame sub–commission
for Europe, EUREF, is responsible for defining, providing access and maintaining the European Terrestrial Reference System (ETRS89) (Bruyninx et al. 2010). The EUREF
key infrastructures are the EUREF Permanent GNSS Network (EPN) and theUnited European Levelling Network (UELN). The EPN is a network of continuously operating GNSS reference stations maintained on a voluntary basis by EUREF members.
Its primary purpose is to provide access to the ETRS89 by making publicly available the
GNSS tracking data as well as the precise coordinates of all EPN stations. The EPN
cooperates closely with the International GNSS Service (IGS, Dow et al. (2009)); EUREF
members are involved in the IGS Governing Board, the IGS Real–Time Pilot Project, the
IGS GNSS Working Group, the IGS Antenna Calibration Working Group, the Troposphere
Working Group, the IGS Multi GNSS Experiment (MGEX), and the IGS Infrastructure
Committee.
The EUREF Technical Working Group (TWG) defines the general policy of the EPN
following proposals by the EPN Coordination Group. This Coordination Group consists

89

EPN RNAACof the Network Coordinator (managing the EPN Central Bureau), Data Flow Coordinator,
Analysis Coordinator, Reference Frame Coordinator, Troposphere Coordinator, Chair of
the Real–time Analysis project, and Chair of the Reprocessing Project.
This paper gives an overview of the main changes in the EPN over the year 2013.

2 Tracking Network
2.1 New Stations
By the end of 2013, the EPN network consisted of 246 continuously operating GNSS reference stations (Fig. 1) from which 32% also belong to the IGS. Before inclusion in the
EPN, the EPN Central Bureau checks the data quality, meta–data, data availability andlatency, and the availability of absolute antenna calibrations for the proposed station.
These absolute antenna calibrations can be type mean calibrations (provided by the IGS)
or individual calibrations (see Baire et al. (2013)). The antenna calibration file used within
the EPN (ftp://epncb.oma.be/pub/station/general/epn_08.atx) contains these individual antenna calibrations complemented with the type mean calibrations from the IGS.
End of 2013, individual calibrations were used at 59 EPN stations amongst which 19(ANKR, BRUX, BUCU, BZRG, GANP, HOFN, METS, NICO, ORID, PENC, POTS,
REYK, RIGA, SASS, SOFI, WARN, WROC, WTZR, and ZIM2) are also belonging to
the IGS.

2013 Dec 17 07:54:29

Figure 1: EPN tracking stations, status Dec. 2013. N indicate new stations included in the
network in 2013.

90

2 Tracking Network
Table 1: New stations included in the EPN in 2013
4 char–ID

Location

Replacement
or New

Sat. Tracking

Antenna Calibration
used in EPN analysis

BRON

Bron, France

new

GPS+GLO+GAL

Type mean from IGS

GPS+GLO
GPS+GLO
GPS+GLO+GAL
GPS+GLO+GAL
GPS+GLO+GAL

Type mean from IGS
Type mean from IGS
Type mean from IGS
Type mean from IGS
Individual from GEO++

GPS+GLO
GPS+GLO
GPS+GLO

Type mean from IGS
Type mean from IGS
Type mean from IGS(but already former)

CAKO
DUB2
DYNG
ILDX
PEN2

Cakovec, Croatia
Dubrovnik, Croatia
Dionysos, GreeceIle d’Aix, France
Penc, Hungary

new
DUBR
new
new
PENC

PORE
POZE
ZADA

Porec, Croatia
Pozega, Croatia
Zadar, Croatia

new
new
new

(not yet former)

As soon as a station fulfils all requirements, it is included in the EPN. Data communication
problems, influencing a reliable upload to the EPN data centres (regional and local ones)
is one of the main reasons delaying the integration of a new station. However, almost all
proposed stations are accepted within six months after their initial proposal. Interested
station managers can check EPN guidelines for a proposed station to become an EPN site
at http://epncb.oma.be/_networkdata/proposed.php.
Eight new stations were integrated in the EPN network in 2013: CAKO, DUB2, DYNG,
ILDX, PEN2, PORE, POZE, and ZADA. They are indicated with triangles in Fig. 1. Moredetails are provided in Tab. 1. Two of the stations are replacements of decommissioned
EPN stations (mostly due to construction work near the antenna).

2.2 Multi–GNSS Tracking
All new stations added to the EPN in 2013 are equipped with GPS/GLONASS tracking
equipment, bringing the percentage of the EPN stations providing GPS+GLONASS data
to 73%. In addition, 96 EPN stations (Fig. 2) operate equipment that is certified “Galileo–
ready”, and 45 of them upload RINEX v3 data including Galileo observations to thedata centre maintained by the BKG (Bundesamt für Kartographie und Geodäsie). The
development is significant taking into account that in August 2008 only 8 and in March2013 33 stations were delivering RINEX v3 data. At present, the most dominant Multi–
GNSS contribution comes from Leica receivers. More than half of the data are not yet offormat 3.02. The development of routine RINEX v3 quality checks, as shown in Fig. 4, isa primary requirement to enhance the EPN to a Multi–GNSS observing network.
In addition, 31 of the 33 new antennas/radomes (new stations or replacements at existingstations) introduced in the EPN during 2013 are capable of tracking new signals from91

EPN RNAAC

2014 Jan 20 03:18:04

http://www.epncb.oma.be/

Figure 2: EPN tracking stations capable oftracking Galileo:
N submitting
RINEX v3 data to EUREF; 4 not(yet) submitting RINEX v3 data to
EUREF.

2014 Jan 20 03:12:06

http://www.epncb.oma.be/

Figure 3: EPN tracking stations capable oftracking L5 indicated with 4; thosein addition including L5 in their
RINEX v2.11 data are indicated by
N.

Figure 4: Completeness of RINEX v3 data of EPN (and MGEX) multi-GNSS stations (mid–September — mid–October 2013). Updated plots available under ftp://ftp.unibe.
ch/aiub/mgex/plots/ep30.png.

923 Data Analysis
multiple GNSS and will not require any additional hardware upgrade in the near future.
Already today 77 EPN stations have the capability of tracking GPS L5, 52 of them are
actually providing RINEX v2.11 data including L5 (see Fig. 3).

2.3 Data flow
The EPN is working with three main data centers defined as regional data centers (RDC).
The BKG and OLG (Austrian Academy of Sciences) data centers are responsible for the
daily business while the data center of the EPN Central Bureau (Royal Observatory of
Belgium) is the basis for the reprocessing activities hosting all historical EPN RINEX datawith corrected meta–data.
All EPN stations routinely submit their data to BKG and OLG in predefined ways. Already before the recommendations of the IGS Workshop 2012, both RDCs accepted files
with gzip compression (valid also for 64–bit UNIX and Windows). While the BKG RDC
already processes and distributes EPN RINEX V3 and high rate data in separate directories, the OLG DC installed this functionality only for MGEX data, but will follow in2014.

3 Data Analysis
3.1 New Analysis Combination Center
In March 2013, BKG announced H. Habrich would retire from his position as Analysis
Center Coordinator. Consequently on April 4 the EUREF Technical Working Groupissued a call for a new Coordinator. On May 28, 2013, the EUREF TWG accepted the
proposal of a consortium between the Military University of Technology (MUT, Warsaw,
Poland) and the Warsaw University of Technology (WUT) to act as the future Analysis
Combination Center (ACC) for a period of 4 years. From June 1st, 2013 to May 31, 2015,
K. Szafranek will be responsible of the ACC and from June 1st, 2015 to May 31, 2017 thistask will be taken over by A. Araszkiewicz. Besides, the ACC team consists of M. Figurski(MUT) and T. Liwosz (WUT).
The most important task for the new ACC in 2013 was to prepare new scripts for the
combination of the solutions provided by the EPN Local Analysis Centers (LAC). To
preserve the continuity, these scripts were based on the previous work of H. Habrich. The
main difference between the MUT/WUT and BKG combination is the reference frame(new solutions are tied to IGb08 instead of IGS08 for the old ones) and, as a consequence,the selection of the reference stations. Currently the alignment to IGb08 is carried out
by adding minimally constrained conditions on 71 IGS stations. MUT/WUT also uses aslightly different method of excluding stations from the LACs contributions – usually it is93

EPN RNAACa matter of 1 station when comparing BKG and MUT/WUT solutions. After an overlap
period of 3 months and several tests confirming that the quality of the combined solution
did not decrease in comparison to the hitherto delivered solutions, routine combinations by
the MUT/WUT consortium will start with GPS week 1768 and published in the beginningof 2014.
The web page of the new ACC has also been prepared (http://www.epnacc.wat.edu.pl).
Currently it presents mainly the details of the weekly combined solutions: comparisonof station coordinates, Helmert transformation parameters for each LAC solution withreference to the combined solution and link to the full combination report available fromthe EPN Central Bureau (ftp://epncb.oma.be/pub/product/reports/). The weekly
reports sent by LAC email have been shortened and now they contain only the mostimportant information. The full combined solutions are still available from the BKG
server (ftp://igs.bkg.bund.de/EUREF/products/).

3.2 Updated EPN Analysis Guidelines
To keep the EPN processing strategy up to date, several changes have been introduced
into the “Guidelines for the EPN Analysis Centres”, available from http://epncb.oma.
be/_documentation/guidelines/guidelines_analysis_centres.pdf. First, final daily
solutions became mandatory. Final weekly combined solutions are still the core EPN
product sent to the IGS as its European densification, but the daily combinations aredeveloped in parallel. To avoid overlapping among LACs and to prepare for the newchallenges which the EPN faces, the LACs have been encouraged to consider a possible
re–orientation of their contribution to the EPN. One of the LACs, GOP (Czech Republic)
has already replied to this call and decided to focus on reprocessing activities insteadof weekly routine submissions. This action required a re–distribution of several stations
processed up to now by GOP LAC. Still, in general, not more than 5 LACs are acceptedfor one EPN station, but exceptions are allowed for twin stations.
The updated analysis guidelines also recommend to use orbits and clocks consistent withthe analysis options and software used by each LAC (or to use combined IGS products)
and require to exclude the defective satellites. Concerning troposphere parameter estimation, it is now mandatory to estimate hourly troposphere parameters for each station and
it is recommended to submit tropospheric gradients (estimated using the Chen–Herringmodel (Chen and Herring 1997) or an equivalent model). The updated guidelines also
introduce the requirement of using GMF (Böhm et al. 2006) or VMF (Böhm and Schuh2004) mapping function to map the tropospheric delay. Within the discussion, the EUREF community stressed the need to develop a Troposphere SINEX format including
gradients.
Several other processing options have been also updated. Starting with GPS week 1765 theelevation cut–off angle was set to 3◦ , application of atmospheric tidal loading corrections94

3 Data Analysis
is recommended and it is mandatory to include 2nd order of ionospheric corrections andionospheric ray bending corrections.

3.3 Routine Processing
A total of 17 Local Analysis Centres submit weekly free–network solutions (SINEX format) for an EPN subnetwork. The majority of the analysis centres used the Bernese GPS
software Ver. 5.0, but in 2013, 11 LACs switched from Ver. 5.0 to Ver. 5.2 and applied the
new analysis guidelines. GPS+GLONASS data are routinely analysed by 12 LACs. The
EPN Analysis Combination Centre combines the subnetwork solutions into the daily andweekly combined EPN solutions. These solutions are tied to the most recent IGS realisation of the ITRS. They are used as input for the EPN Reference Frame Coordinator forthe generation of a multi–year EPN solution which is updated each 15 weeks, and provides
up–to–date EPN positions and velocities allowing the classification of EPN stations as:• Class A stations with positions at 1 cm accuracy at all epochs of the time span of
the used observations;• Class B stations with positions at 1 cm accuracy at the epoch of minimal varianceof each station.
Following the EUREF “Guidelines for EUREF Densifications” (Bruyninx et al. 2010), only
Class A EPN stations can be used for densifications of the ETRS89.
In addition, a smaller group of LACs is also submitting a rapid solution that is provided
less than 24 hours after the last observations and an ultra–rapid (hourly) solution provided
about one hour after the last observations to the EPN Combination Centre. Here, thedifferent solutions are combined into a rapid and an ultra–rapid EPN solution. The numberof LACs submitting these solutions varies, currently 10 LACs upload rapid and 3 LACs
upload ultra–rapid solutions.
Beside station coordinates, the 17 LACs also submit zenith total delay (ZTD) parameters
on a routine basis. The ZTD parameters are delivered with a sampling rate of 1 hour, on a
weekly basis but in daily files. Thanks to the growing computation power, the individual
LACs could enlarge their respective network. This way, almost all EPN stations areprocessed by at least four LACs which improves, e.g., the outlier detection. The weekly
mean bias and its standard deviation (Fig. 5 and 6) are well below the 2mm ZTD level
since more than three years of routine operation.
Alongside the ZTD combination which gives insight into the agreement of the individual
solutions to each other some inter–technique comparisons have been added to the website of the EPN Central Bureau. The time series of differences of EPN ZTD estimateswith respect to radiosonde–derived ZTDs are computed for almost 100 stations. For
the stations considered the horizontal distance between radiosonde and GNSS location isvarying from less than 1 km up to 70 km. The standard deviation of the differences is

95

EPN RNAAC

Figure 5: Weekly mean biases of LACs individual ZTD contributions w.r.t. the combined ZTD
solution (mm ZTD); results from routine operation since June 2001.

Figure 6: Standard deviation of weekly mean biases of LACs individual ZTD contributions
w.r.t. the combined ZTD solution (mm ZTD); results from routine operation sinceJune 2001.

96

3 Data Analysis
between 4 and 19 mm ZTD. The difference time series for co–located VLBI stations areavailable for ten stations. Here the bias of the differences is in the range of 0.3 to –7.1 mm
ZTD with standard deviation between 3.8 to 6.5 mm ZTD. It should be noted that theheight difference between the sensors has not been taken into account for the plots. A
more detailed comparison is given in Heinkelmann et. al (2013).

3.4 EPN Reprocessing
The first re–analysis of the complete EPN was concluded in 2012 under the name EPN–
Repro1 (Völksen 2011). Already then it became clear that the reprocessing of the entire
EPN will be a continuous task for the coming years, always related to the realizationof a new reference system (e.g. ITRF2008) or significant improvements in the analysis
strategies. Therefore it has been decided in the summer of 2013 to conduct a second
reprocessing of the entire EPN under the name EPN–Repro2.
While in EPN–Repro1 almost the entire group of Local Analysis Centres participated, thefocus of EPN–Repro2 lies on the generation of three entirely independent and complete
EPN solutions based on GAMIT version 10.50 (King et al. 2010), GIPSY version 6.2(Lichten et al. 1995), and Bernese GNSS Software version 5.2 (Beutler et al. (2007), Dachet al. (2013)). The analysis of historical GLONASS data is of large interest but this partof the analysis can only be carried out by Bernese GNSS Software (NAPEOS is not yet
available to one of the participating LACs). These three solutions will be generated bythree different LACs using one of the three mentioned software packages. Still, EPN–
Repro2 is also open for the participation of other LACs.
The analysis of EPN–Repro2 will be performed as a regional network based on the reprocessed products provided by CODE and JPL, because other or the combined products ofthe 2nd IGS Reprocessing campaign are not yet available. GNSS observation data will bemade available by the EPN Central Bureau and are mandatory to be used. These data arecross–checked with the station logs of the GNSS sites and meet the current IGS standards.
EPN–Repro2 will not completely follow the guidelines of the IGS but will be very muchconsistent to the routine processing of the EPN using the updated analysis guidelines.
For example the EPN–Repro2 campaign will use the individual antenna calibrations andcomplement them with type mean calibrations.
A benchmark test has been designed consisting of 32 sites covering large parts of Europe.
The test data cover a period of 4 weeks (1677–1688) with moderate and active ionosphericconditions to evaluate the performance of the different software packages. After successful
completion of the benchmark, the entire EPN will be reanalyzed and the results are
expected by the summer 2014.

97

EPN RNAAC

3.5 Local Analysis Centers Workshop
The 8th EPN Local Analysis Centers Workshop was held in at the ROB (Royal Observatory of Belgium) in Brussels from May, 15 to 16, 2013. The workshop was preceded by a half–day tutorial on the Bernese GNSS software Ver. 5.2. With 37 participants, the workshop mainly focused on discussions related to the overdue update of
the EPN analysis guidelines. The Minutes of the workshop are available from http://epncb.oma.be/_newseventslinks/workshops/EPNLACWS_2013/.

4 Densification of the IGS and EPN
The European IGS densification solution is a cumulative EPN solution which is routinely
updated each 15 weeks, uses all available weekly EPN SINEX solutions from GPS week
834 on. The SINEX solutions before GPS week 1632 have been corrected to be compliant
with the epn_08.atx/igs08.atx antenna calibration model. Since GPS week 1709, the EPN
cumulative solution is tied to the IGb08.
The EPN/IGb08 densification product files (including a discontinuity table and associatedresidual position time series) can be downloaded from the
ftp://epncb.oma.be/pub/station/coord/EPN.
More details can be found in
http://epncb.oma.be/_productsservices/coordinates.
The densification of the EPN, using the dense national active GNSS networks, was continued. The main target of this work (beyond the homogenization of the national networks)
is to compute a dense continental–scale velocity field to support an improved realizationof the ETRS89. The product will be an important input for the IAG Working Group on“Integration of dense velocity fields into the ITRF” (Legrand et al. 2013). Most of theEuropean countries are providing weekly SINEX solutions to the EPN Reference Frame
Coordinator. By the end of 2013 the total number of stations exceeded 2000. These solutions are combined with the weekly EPN solution and then stacked to obtain a consistentcumulative position/velocity solution. Two contributions (IGN, France and BIGF, UK)
are global solutions and therefore the densified EPN network will be considered as densification of the global IGS network as well. This work is still in progress (see Kenyeres
et al. (2013)).

5 EPN Real–Time Analysis Project
The EPN Project on “Real–time Analysis” is focusing on the processing of the EPN real–time data to derive and disseminate real–time GNSS products (http://www.epncb.oma.

986 Conclusions
be/_organisation/projects/RT_analysis/).
EUREF’s real–time resources have been contributing to the IGS Real–Time Service (IGS
RTS) which has been launched in March 2013 (Caissy et al. 2013). Several EPN stations
are permanently used for the orbit and clock correction processing within the IGS RTS by
the various real–time analysis centers. Moreover, the IGS RTS products have been madeavailable through the dedicated products broadcaster located at BKG (http://products.
igs-ip.net).
In view of the successful launch of the new COST action on advanced GNSS processing andproducts for Meteorology and Climate (Jones et al. 2013) significant effort has been donein the derivation of real–time ZTD estimates using IGS and EUREF real–time resources(e.g. Douša and Václavovic (2013); Pacione and Söhne (2013)).
Since 2012, EUREF is broadcasting satellite orbit and clock corrections referred to the
ETRS89 (realization ETRF2000). Two different data streams are available for the moment:• EUREF01: corrections for GPS, sampling rate 5 seconds, coming from Kalman–filter
based combination• EUREF02: corrections for GPS+GLONASS, sampling rate 5 seconds, coming from
Kalman–filter based combination
Together with the real–time broadcast ephemerides data stream, named RTCM3EPH,
users can directly derive real–time coordinates referred to ETRS89 at the level of a few
decimetres. These data streams are available from the three EUREF regional broadcasters
at BKG (http://www.euref-ip.net and http://products.igs-ip.net), at ASI (http://euref-ip.asi.it:2101/), and at ROB (http://www.euref-ip.be).

6 Conclusions
Considerable progress has been made within the EUREF Permanent GNSS Network in
2013.
73% of the 246 EPN stations now track GLONASS in addition to GPS and 45 stations
provide RINEX v3 including Galileo observations. Presently the EPN focusses on thedevelopment of routine RINEX v3 quality checks.
An EPN Local Analysis Centres Workshop was held in Brussels in May 2013. During theworkshop the LAC discussed the introduction of new analysis guidelines.
A new Analysis Combination Centre was set up in the summer of 2013. Located at
Warsaw, the MUT/WUT consortium will take over the routine combination of the EPN
LAC products in January 2014.

99

EPN RNAAC
In the fall of 2013, the updated analysis guidelines were introduced. They include thegeneration of a new daily final solution and the application of several state–of–the art
GNSS modelling techniques.
Time series of differences of EPN zenith tropospheric delay estimates with respect toradiosonde–derived ZTDs are now made available at the EPN CB for almost 100 stations
and in addition, the difference time series for co–located VLBI stations is provided for ten
stations.
EPN–Repro2 is presently prepared. It will be based on three entirely independent andcomplete EPN solutions provided with GAMIT, GIPSY and Bernese. As a first step, abenchmark campaign is underway to test the analysis strategies and the setup of the threesoftware packages. The results of EPN–Repro2 are expected for the summer of 2014.
Since GPS week 1709, the EPN cumulative solution is tied to the IGb08. In addition, adensification of the EPN is performed using weekly SINEX solutions provided by several
European countries for their dense GNSS networks. These solutions are combined with theweekly EPN solution and then stacked to obtain a consistent cumulative position/velocity
solution. The latest EPN densification already exceeds 2000 GNSS stations.
The EPN Real–Time Analysis Project is closely linked to the IGS Real–Time Service atboth the station level as the level of product distribution. EUREF is also broadcastingsatellite orbit and clock corrections allowing users to derive real–time coordinates in the
ETRS89 at few decimetres level.
More information on the EPN: http://www.epncb.oma.be/.

References
Baire, Q., C. Bruyninx, J. Legrand, E. Pottiaux, W. Aerts, P. Defraigne, N. Bergeot, andJ.M. Chevalier. Influence of different GPS receiver antenna calibration models on
geodetic positioning. GPS Solutions, doi: 10.1007/s10291-013-0349-1 (online), 2013.
Bertiger, W., S. D. Desai, B. Haines, N. Harvey, A. W. Moore, S. Owen, and J. P. Weiss.
Single receiver phase ambiguity resolution with GPS data. Journal of Geodesy, 84(5):327–337, 2010.
Bruyninx, C., Z. Altamimi, C. Boucher, E. Brockmann, A. Caporali, W. Gurtner,
H. Habrich, H. Hornik, J. Ihde, A. Kenyeres, J. Mákinen, G. Stangl, H. Van Der Marel,
J. Simek., W. Söhne, J. A. Torres, and G. Weber. The European Reference Frame:
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Beutler, G., H. Bock, E. Brockmann, R. Dach, P. Fridez, W. Gurtner, H. Habrich,
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S. Schaer, R. Schmid, T. Springer, P. Steigenberger, D. Svehla, D. Thaller, C. Urschl,
and R. Weber. Bernese GPS software version 5.0. U. Hugentobler, R. Dach, P. Fridez,
M. Meindl(eds.), Univ. Bern, 2007.
Böhm, J., A. Niell, P. Tregoning, and H. Schuh. Global Mapping Function (GMF): A
new empirical mapping function based on numerical weather model data. GeophysicalResearch Letters, 33(7), 2006. doi: 10.1029/2005GL025546.
Böhm, J. and H. Schuh. Vienna Mapping Functions in VLBI analyses. GeophysicalResearch Letters, 2004. doi: 10.1029/2003GL018984
Bruyninx, C., Z. Altamimi, A. Caporali, A. Kenyeres, M. Lidberg, G. Stangl, and J. Torres. Guidelines for EUREF Densifications. ftp://epncb.oma.be/pub/general/
Guidelines_for_EUREF_Densifications.pdf, 2010.
Caissy, M., L. Agrotis, G. Weber, and S. Fisher. The IGS Real–Time Service. Presented
at EGU General Assembly, Vienna, Austria, 2013.
Chen, G. and T. A. Herring. Effects of atmospheric azimuthal asymmetry on the analysis
from space geodetic data. J Geophys Res 102, 102(B9):20489–20502, 1997. doi: 10.
1029/97JB01739.
Dach, R. Bernese GNSS Software: New features in version 5.2. Document compiled by
the AIUB GNSS Software development team. http://www.bernese.unibe.ch/docs/
BSW52_newFeatures.pdf, 2013.
Douša, J., and Václavovic, P.. Real–time ZTD Estimates Based on Precise Point Positioning and IGS Real–time Orbit and Clock Products. Proceedings 4th International
Colloquium Scientific and Fundamental Aspects of the Galileo Programme., Prag,
Czech Republic, 2013.
Dow, J.M., R. Neilan, and C. Rizos. The International GNSS Service in a changing
landscape of Global Navigation Satellite Systems. Journal of Geodesy, 83:191–198,
2009. doi: 10.1007/s00190-008-0300-3.
Heinkelmann, R., W. Söhne, and H. Schuh. Comparison of GNSS (EUREF) and VLBI(EVGA) tropospheric delays. Presented at EGU General Assembly, Vienna, Austria,
2013.
Jones, J., G. Guerova, O. Bock, S. De Haan, G. Dick, J. Dousa, G. Elgered, R. Pacione,
E. Pottiaux, and H. Vedel. COST ES1206: Advanced GNSS Tropospheric Products for Monitoring Extreme Weather Events and Climate. Presented at EUREF
Symposium, Budapest, Hungary, May 29–31, 2013. http://www.euref.eu/symposia/
2013Budapest/02-02_Jones_GNSS4SWEC.pdf)
Kenyeres, A., T. Jambor, A. Caporali, B. Drosčak, B. Garayt, I. Georgiev, I. Jumare,J. Nagl, P. Pihlak, M. Ryczywolski, and G. Stangl. Integration of the EPN and the101

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dense national Permanent Networks. Presented at EUREF Symposium, Budapest,
Hungary, 29–31 May, 2013.
King, R. W., T. A. Herring., and S. C. McClusky. Documentation for the GAMIT GPS
analysis software 10.4. Massachusetts Institute of Technology Internal Report, USA,197 p. (http://www-gpsg.mit.edu/~simon/gtgk/GAMIT_Ref.pdf), 2010.
Legrand, J., C. Bruyninx, M. Craymer, J. Dawson, J. Griffiths, A. Kenyeres, P. Rebischung, L. Sanchez, E. Saria, and Z. Altamimi. A Collaborative Approach Toward
the Densification of the ITRF Velocity Field. Presented at AGU Fall Meeting, San
Francisco, US, Dec. 9–13, 2013.
Lichten, S. M., Y. E. Bar-Sever, E. I. Bertiger, M. Heflin, K. Hurst, R. J. Muellerschoen,
S. C. Wu, T. P. Yunck, and J. F. Zumberge. GIPSY-OASIS II: A high precision
GPS data processing system and general orbit analysis tool. Technology 2006. NASA
Technology Transfer Conference, Chicago, 1995.
Pacione, R. and W. Söhne. Exploitation fo the new IGS Real–Time Products for GNSS
meteorology. Proceedings 4th International Colloquium Scientific and Fundamental
Aspects of the Galileo Programme., Prague, Czech Republic, 2013.
Völksen, C. An Update on the EPN Reprocessing Project: Current Achievement andStatus. Presented at EUREF Symposium, Chisinau, Moldova, May 25–28, 2011.

102

IGS Regional Network Associate Analysis Center
for SIRGAS (IGS RNAAC SIR)
Laura Sánchez
Deutsches Geodätisches Forschungsinstitut (DGFI)
Alfons–Goppel–Str. 11, D–80539 München, Germany
E-mail: sanchez@dgfi.badw.de

1 The SIRGAS reference frame
The realisation of SIRGAS (Sistema de Referencia Geocéntrico para las Américas) isa regional densification of the International Terrestrial Reference Frame (ITRF) (e.g.,
SIRGAS (1997), Drewes et al. (2005), Sanchez and Brunini (2009)). At present, it iscomposed of GNSS stations only; other geodetic space techniques like VLBI, SLR or
DORIS are not involved yet. To guarantee the appropriate maintenance of the reference
frame, SIRGAS comprises (Fig. 1):• One core network (SIRGAS–C) composed of a set of geographically well–distributedand consistently reliable reference stations. The main objective of the SIRGAS–C
network is to ensure the long–term stability of the reference frame, and it is understood as the primary densification of the ITRF in Latin America and the Caribbean.
• National reference networks (SIRGAS–N) realising densifications of the core network.
The central purpose of these densifications is to provide accessibility to the reference
frame at national and local levels and to facilitate its extension by assimilating newreference stations (mainly those installed by the national agencies responsible forthe local reference networks).
The SIRGAS reference frame is calculated weekly. The SIRGAS–C network is processedby the Deutsches Geodätisches Forschungsinstitut (DGFI, Germany) since this instituteacts as the IGS Regional Network Associate Analysis center for SIRGAS (IGS RNAAC
SIR, Sanchez (2012), (2013)). The SIRGAS–N networks are computed by the SIRGAS Local Processing centers, which operate under the responsibility of national Latin Americanorganisations. At present, the SIRGAS Local Processing centers are: CEPGE (Ecuador),
CPAGS–LUZ (Venezuela), IBGE (Brazil), IGAC (Colombia), IGM–Cl (Chile), IGN–Ar(Argentina), INEGI (Mexico), and SGM–Uy (Uruguay). These processing centers deliver103

SIRGAS RNAAC

Figure 1: SIRGAS network (as of December 2013).

104

3 Kinematics of the SIRGAS reference frame
loosely constrained weekly solutions for the SIRGAS–N national networks, which are combined with the SIRGAS–C core network to get homogeneous precision for station positionsand velocities. The individual solutions are combined by the SIRGAS Combination centerscurrently operated by DGFI (Germany) and IBGE (Brazil).

2 Routine processing of the SIRGAS reference frame
The SIRGAS processing centers follow unified standards for the computation of the loosely
constrained solutions (e.g., Costa et al. (2012), Natali et al. (2009), Seemüller et al.
(2012)). These standards are generally based on the conventions outlined by the IERS
and the GNSS–specific guidelines defined by the IGS; with the exception that in theindividual SIRGAS solutions the satellite orbits and clocks as well as the Earth orientation parameters (EOP) are fixed to the final weekly IGS values (SIRGAS does notcompute these parameters), and positions for all stations are constrained to ±1 m (togenerate the loosely constrained solutions in SINEX format). INEGI (Mexico) and IGN–
Ar (Argentina) employ the software GAMIT/GLOBK (Herring et al. 2010); the otherlocal processing centers use the Bernese GPS Software Ver. 5.0 (Dach et al. 2007). At
the moment, the SIRGAS Local Processing centers align their procedures to the newstandards described in the IERS Conventions 2010 (Petit and Luzum 2010) and to thecharacteristics specified by the IGS for the second reprocessing of the IGS global network(http://acc.igs.org/reprocess2.html). The IGS RNAAC SIR applies these new standards since July 2013 and is employing the Bernese GNSS Software Ver. 5.2 (Dach et al.
(2007), (2013)). It is expected that the other processing centers start delivering solutions
based on the new standards in January 2014.

3 Kinematics of the SIRGAS reference frame
To estimate the kinematics of the SIRGAS reference frame, a cumulative (multi–year)
solution is computed (updated) every year, providing epoch positions and constant velocities for stations operating longer than two years. As the introduction of ITRF2008(i.e. IGS08/IGb08) as the reference frame for the generation of the IGS products caused a
discontinuity of some mm in the station position time series, the computation of multi–year
solutions for the SIRGAS reference frame was discontinued until getting weekly normal
equations referring to the ITRF2008 and covering a time span of at least three years. It
is decided that SIRGAS will reprocess the entire SIRGAS network following IGS procedures and applying the new standards from January 1997 to present. However, while the
SIRGAS Local Processing centers are unable to apply these, a new multi–year solution wascomputed for the SIRGAS–C core network only, i.e., for the stations processed routinely
by the IGS RNAAC SIR. Main objective of this multi–year solution is to identify possible
secular effects caused by the Maule earthquake of February 2010 in the kinematics of the105

SIRGAS RNAACSIRGAS reference frame.

4 New processing standards for the SIRGAS reference frame
The standards applied for the generation of the weekly free normal equations for the new
cumulative SIRGAS solution are:
• Basic observable: ionosphere–free linear combination;• Sampling rate: 30 sec;

• Elevation cut–off angle: 3 deg;

• Elevation–dependent weighting of observations: 1/cos2 z, with z being the zenith
distance;• Satellite orbits, satellite clock offsets, and EOP fixed to the combined IGS weekly
solutions (Dow et al. (2009), http://www.igs.org/components/prods.html) referring to the IGS08/IGb08 frame. Since the IGS products refer to IGS08/IGb08 sinceApril 2011 (GPS week 1632), the normal equations for previous weeks (backwards
until April 2010) were computed using the satellite products and EOP generated
by the IGS processing center CODE (center for Orbit Determination in Europe,
ftp://ftp.unibe.ch/aiub/CODE/);• Application of antenna phase center offsets and direction–dependent phase center
variation values consistent with the IGS08/IGb08 frame for both transmitting andreceiving antennas; i.e., spacecraft–specific z–offsets, block–specific x– and y–offsets,
and phase center variations for receiver and satellite antennas from model igs08.atx(Schmid et al. (2007), http://igs.org/igscb/station/general/pcv_archive);• Antenna radome calibrations applied if given in the model igs08.atx. Otherwise, theradome effect is neglected and the standard antenna model (radome NONE) is used;• Phase ambiguities for L1 and L2 solved using the quasi–ionosphere free (QIF) strategy of the Bernese GNSS Software Ver. 5.2 (Dach et al. 2007). In this step, theionosphere models of CODE (ftp://ftp.unibe.ch/aiub/CODE/) are provided as
input to increase the number of solved ambiguities;• The tropospheric zenith delay is modelled using the Vienna Mapping Function 1(VMF1, Böhm et al. (2006)). The a priori values (∼ dry part) are derived fromgridded coefficients based on the climate numerical models of ECMWF (European
center for Medium–Range Weather Forecasts) and made available by J. Böhm, TU
Vienna, at http://ggosatm.hg.tuwien.ac.at/DELAY/GRID/VMFG/. These a priori
values are refined by computing partial derivatives of the troposphere zenith delay
parameters (∼ wet part) with 2h intervals (using also VMF1) within the network
adjustment. In addition, to model azimuthal asymmetries, horizontal gradient pa-

106

5 Multi–year solution SIR13P01
rameters are estimated according to the model of Chen and Herring (1997);• Tidal corrections for solid Earth tide, permanent tide, and solid Earth pole tide areapplied as described in Petit and Luzum (2010). The ocean tide loading is reducedwith the FES2004 model (Letellier 2004) and the atmospheric tidal loading causedby the semidiurnal constituents S1 and S2 is reduced following the model of van Dam
and Ray (2010). The reduction coefficients for the ocean tide loading are provided
by M.S. Bos and H.–G. Scherneck at http://holt.oso.chalmers.se/loading. The
reduction coefficients for the atmospheric tidal loading are provided by T. van Dam
at http://geophy.uni.lu/ggfc-atmosphere/tide-loading-calculator.html• Ocean or atmospheric tide geocenter coefficients are not applied since this correctionis already contained in the final IGS (and CODE) products;• Non–tidal loadings as atmospheric pressure, ocean bottom pressure, or surface hydrology are not reduced;• Daily free normal equations are computed by applying the double difference strategy
using the Bernese GNSS Software Ver. 5.2 (Dach et al. (2007), (2013)). The baselines
are created taking into account the maximum number of common observations forthe associated stations;• The seven daily free normal equations corresponding to a GPS week are combinedfor computing a weekly free normal equation. Stations with large residuals in any
daily normal equation (more than ±20 mm in the horizontal component or morethan ±30 mm in the vertical component) are reduced from the corresponding daily
equation and the weekly combination is recomputed.

5 Multi–year solution SIR13P01
The input data for this new cumulative solution are the weekly free normal equations
covering the time span from April 2010 (GPS week 1580) to June 2013 (GPS week 1744).
Given that most of the existing ITRF stations in South America are affected by theearthquake in Chile in February 2010 (see e.g. Sánchez et al. 2013), further stations
located in Europe, Africa, Oceania and North America (Fig. 2) are included in the SIRGAS
computations to increase the availability of fiducial points.
Before combining the weekly normal equations, a time series analysis is performed to
identify outliers and discontinuities in the station positions. The thresholds for outliers
are defined by ±15 mm for north and east and ±30 mm for height (about fourfold themean RMS). If outliers appear sporadically (without pattern), the station is reduced fromthe respective free normal equation. If outliers reflect a discontinuity, a new position is
set up for the station. Once outliers are reduced and discontinuities are identified, theweekly normal equations are combined to a multi–year solution setting up constant station

107

SIRGAS RNAAC

Figure 2: Horizontal velocities of the SIRGAS multi–year solution SIR13P01: it covers the timespan from April 2010 to June 2013, includes 108 SIRGAS core stations and refers to
ITRF2008, epoch 2012.0. (Stations with labels are fiducial points).

velocities (i.e. only linear station position variations are considered). The geodetic datumis realised by applying not–net–rotation and not–net–translation conditions with respect
to the ITRF2008 coordinates (Altamimi et al. 2011) of selected IGb08 reference stations(Fig. 2). This procedure is carried out using the Bernese GNSS Software Ver. 5.2 (Dachet al. 2007)
The result of this computation is called solution SIR13P01 (Fig. 2). It includes positionsand velocities for 108 SIRGAS core stations referring to the ITRF2008, epoch 2012.0.
Its estimated precision is ±1.4 mm (horizontal) and ±2.5 mm (vertical) for the station
positions at the reference epoch, and ±0.8 mm/yr (horizontal) and ±1.2 mm/yr (vertical)
for the constant velocities. Stations showing very irregular post–seismic movements, like
CONZ (Concepción, Chile) or ANTC (Antuco, Chile), are excluded because constantvelocities (linear movements) are insufficient to model their behaviour (Fig. 3).
To evaluate the reliability of the SIR13P01 solution, different comparisons were performed(Tab. 1). The first comparison concentrates on the dissimilarities of the station positionsand velocities at the fiducial points, i.e. the ITRF2008 values are compared with thevalues obtained in the SIR13P01 solution for the reference stations. The same procedure
is repeated in a second comparison, but only taking into account those ITRF stations thatwere not used as fiducial points. Finally, the third comparison collates station position andvelocities of the present solution with those values estimated in the last SIRGAS multi–year
solution computed before the earthquake in February 2010 (i.e. the SIR10P01 solution,
Seemüller et al. (2010)). The first and the second comparisons show the agreement between
the new SIRGAS solution and ITRF2008; the third comparison should provide information108

5 Multi–year solution SIR13P01

Figure 3: Time series of stations strongly affected by the Chilean earthquake in February 2010(Concepción and Antuco).

109

SIRGAS RNAAC
Table 1: Comparison of the present SIR13P01 solution with ITRF2008 and the former solution
SIR10P01 (computed before the Chilean earthquake in February 2010)

Position [mm]N

E

Velocity [mm/yr]
U

N

E

U

Comparison with ITRF2008, fiducial points only
RMS

±3.2

±3.1

±3.8

±0.6

±1.1

±1.3

Min

–6.5

–4.3

–7.8

–1.8

–2.0

–2.3

Max

4.6

8.3

7.0

1.8

1.9

2.4

Mean

0.2

0.9

–0.9

–0.3

–0.1

0.6

Comparison with ITRF2008, non–fiducial points
RMS

±8.2

±12.4

±13.7

±1.3

±3.2

±3.4

Min

–21.8

–25.8

–29.0

–3.1

–19.8

–8.9

Max

14.5

25.7

37.0

6.3

7.4

7.9

Mean

–0.1

9.8

–7.2

1.3

–0.3

–2.1

Comparison with SIR10P01
RMS

±21.4

±39.5

±20.2

±1.3

±2.0

±2.7

Min

–88.3

–51.2

–26.2

–4.3

–19.8

–8.3

Max

130.5

588.3

130.59

6.8

3.7

11.5

Mean

–3.6

8.3

–5.9

1.0

–1.2

–1.3

about changes in the SIRGAS frame caused by the strong earthquake in Chile.
The discrepancies (for station positions and velocities) at fiducial points are within thecoordinate accuracy of the ITRF2008 solution. Therefore, one could conclude that the
new SIRGAS solution is appropriately aligned to this frame and it can be considered as its
regional densification in Latin America and the Caribbean. The magnitudes obtained fromthe other two comparisons are on the contrary very large, in particular in the East component (Fig. 4). This means that older reference frame solutions (ITRF2008 or SIR10P01)
differ significantly from the new realisation. Main reasons for this disagreement are:
• ITRF2008 and SIR10P01 do not reflect the effects (co–seismic and post–seismic
movements) caused by the earthquake of February 2010 in the Southern part of110

5 Multi–year solution SIR13P01

Figure 4: Horizontal (left) and vertical (right) residual position (upper two figures) and velocity(lower two figures) vectors between the SIR10P01 (before the earthquake in February2010) and the SIR13P01 solutions.

111

SIRGAS RNAACSouth America;• The weekly input solutions for ITRF2008 and SIR10P01 were computed with respect
to the IGS05 frame, while SIR13P01 was computed with respect to the IGS08/IGb08
frame;• Troposphere effects in SIR10P01 and SIR13P01 are modelled differently. Although
the atmosphere parameters estimated within the network adjustment (∼ wet part)are very similar (some mm of discrepancy), the a priori zenith delay values (∼ drypart) differ by up to 5 cm, especially at those stations located in the tropical region;• The datum realisation in SIR10P01 and SIR13P01 is based on different fiducial
points. While the old solution includes reference stations located in Latin America
only, the new solution also comprises reference stations located several thousand kmaway.

6 Outlook
Immediate plans concentrate on the reprocessing of the weekly SIRGAS normal equations
backwards until January 1997 applying the new standards and considering the entire
network. Therefore, the IGS RNAAC SIR takes care of the computations from 1997 until
August 2008, when the first SIRGAS Local Processing centers started operating. From
September 2008 until December 2013, the reprocessing includes the combination of theindividual (reprocessed) solutions delivered by the SIRGAS Local Processing centers for
the SIRGAS–N national networks.

7 Acknowledgements
The operational infrastructure and results described in this report are only possible thanks
to the active participation of many Latin American and Caribbean colleagues, who not
only make the measurements of the stations available, but also operate SIRGAS Analysis
centers processing the observational data on a routine basis. This support and that provided by the International Association of Geodesy (IAG) and the Pan–American Institutefor Geography and History (PAIGH) is highly appreciated. More details about the activities and new challenges of SIRGAS, as well as institutions and colleagues working on canbe found at http://www.sirgas.org.

112

References

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Altamimi, Z., X. Collilieux, and L. Métivier ITRF2008: an improved solution of theinternational terrestrial reference frame. Journal of Geodesy, 85(8):457–473, 2011.
doi: 10.1007/s00190-011-0444-4.
Böhm, J., B. Werl, and H. Schuh Troposphere mapping functions for GPS and very long
baseline interferometry from European center for Medium–Range Weather Forecasts
operational analysis data. Journal of Geophysical Research, 111, B02406, 2006. doi:
10.1029/2005JB003629.
Chen, G. and T.A. Herring. Effects of atmospheric azimuthal asymmetry on the analysisof space geodetic data Journal of Geophysical Research, 102(B9):20489–20502, 1997.
doi: 10.1029/97JB01739.
Costa, S.M.A., A.L. Silva, and J.A. Vaz. Processing evaluation of SIRGAS–CON network
by IBGE Analysis Center. In: Geodesy for Planet Earth, IAG Symposia, 136:859–868,
2012. doi: 10.1007/978-3-642-20338-1_108.
Dach, R., U. Hugentobler, P. Fridez., and M. Meindl (Eds.) Bernese GPS Software Version
5.0(Documentation) Astronomical Institute, University of Bern, 2007.
Dach, R. and the Bernese GNSS Software development team Bernese GPS Software: Newfeatures in version 5.2. Astronomical Institute, University of Bern, 2013. On–line
available at http://www.bernese.unibe.ch/docs/BSW52_newFeatures.pdf.
Dow, J.M., R.E. Neilan, and C. Rizos. The International GNSS Service in a changing
landscape of Global Navigation Satellite Systems Journal of Geodesy, 83:191–198,
2009. doi: 10.1007/s00190-008-0300-3.
Drewes, H., K. Kaniuth, C. Voelksen, S.M. Alves Costa, and L.P. Souto Fortes. Resultsof the SIRGAS campaign 2000 and coordinates variations with respect to the 1995
South American geocentric reference frame. In: A Window on the Future of Geodesy,
IAG Symposia, 128:32–37, 1995. doi: 10.1007/3-540-27432-4_6.
Herring, T.A., R.W. King, and S.C. Mclusky. Introduction to GAMIT/GLOBK, Release 10.4. Massachusetts Institue of Technology, 2010. On–line available at http://www-gpsg.mit.edu/~simon/gtgk/Intro_GG.pdf.
Letellier, T. Etude des ondes de marée sur les plateux continentaux. Thèse doctorale, Université de Toulouse III, Ecole Doctorale des Sciences de l’Univers, de l’Environnement
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Natali, M.P., M. Mueller, L. Fernández, and C. Brunini. CPLat: first operational experimental processing center for SIRGAS in Argentina. Journal of Geodesy, 83(3):219–226, 2009. doi: 10.1007/s00190-008-0270-5.

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Sánchez, L. IGS Regional Network Associate Analysis center for SIRGAS(IGS RNAAC
SIR). In: Meindl, M., R. Dach, Y. Jean (Eds): IGS Technical Report 2011, IGS
Central Bureau, pp. 107–115, 2012.
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Reference Frames, IAG Symposia, 134:161–166, Springer Berlin Heidelberg, 2009.
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the SIRGAS processing centers for the SIRGAS–CON reference frame. In: Geodesy for
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W. Martínez, V. Cioce, D. Cisneros, and S. Cimbaro. Long–term stability of the SIRGAS reference frame and episodic station movements caused by the seismic activity
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Part III

Data Centers

115

IGS Infrastructure Committee
Technical Report 2013
Ignacio Romero
ESA/ESOC, Navigation Support Office, Darmstadt, Germany
E–mail: Ignacio.Romero@esa.int / nacho@sacsl.es

1 Introduction
The Infrastructure Committee (IC) was established in March 2009 and is set with the taskof studying and advising on infrastructure issues to the IGS Governing Board and the IGS
Network Coordinator (NC). The latest status and recent progress of the Committee aredetailed below.

2 Membership
Current Members appointed 3 April, 2011 for terms up to December 2013:• Carine Bruyninx (ROB)• Lou Estey (UNAVCO)• Gary Johnston (GA)• Nacho Romero – Chairman – (ESOC)• Mike Schmidt (NRCan)• Georg Weber (BKG)

Ex–officio Members:• Steve Fisher – Central Bureau• Jake Griffiths – Analysis Center Coordinator• Mark Caissy – Real time Working Group Chair• Bruno Garayt – Reference Frame Coordinator• Carey Noll – Data Center Working Group Chair• Ken Senior – Clock Products Coordinator
117

INFRASTRUCTURE COMMITTEE

3 Charter
The Charter remains the same as published here:
http://igs.org/organization/iccharter.html

4 Summary of Activities in 2013
During 2013 the IC has been involved in many different activities as detailed below:• Site guidelines produced by the IC were finally accepted and published throughhttp://igs.org/network/guidelines/guidelines.html.
• Continued to support the radome–off study at co–located sites for closure in
December 2013. Added stations, ONSA and LHAZ, in the study increased thenumber of participating stations to 10. (See Tab. 1.)
During the year 2013, solutions using Network PPP have been produced and coordinated by the IC and the Reference Frame WG has analyzed the entire time series.
The results and conclusions of the study will be presented in a poster at the AGU
Fall 2013 meeting.
The final conclusion is that it is not possible to extract the radome effect at moststations from the global post-processing, even when applying correction models due
to EQ relaxing, etc.
• Investigating the NGA station data. After resolving the new ITT antenna calibration issues for GPS, the data was processed in network PPP mode and a draft
Table 1: List of stations participating in the radome–off study
Station
CRO1
TSKB
TSK2
AREQ
FAIR
YAR2
GODE
MDO1
ONSA
LHAZ

118

Radome Removal
01 Apr. 2011
01 Jul. 2011
01 Jul. 201119 Aug. 201128 Apr. 201228 Apr. 201206 Jul. 2012
22 Feb. 2013
28 Aug. 201312 Sep. 2013

Re–installation
24 Jun. 2011
30 Aug. 2011
30 Aug. 2011
03 Feb. 201204 Aug. 201228 Sep. 201213 Dec. 2012
09 Aug. 201306 Nov. 201311 Feb. 2014

Antenna
ASH701945G_M
AOAD/M_T
AOAD/M_T
AOAD/M_T
ASH701945G_M
AOAD/M_T
AOAD/M_T
AOAD/M_T
AOAD/M_B
ASH701941.B

JPLA
DOME
DOME
JPLA
JPLA
JPLA
JPLA
JPLA
OSOD
SNOW

6 Plan for 2014
report is available and has been circulated in the IC. The data processing is fine in
un-differenced mode and ambiguity fixing proceeds normally. Unfortunately in double difference mode the NGS analysis confirms that the NGA data is not correctly
fixed of 1/2 cycle problems. It is not clear how this issue could be resolved and conversations continue with NGA and their contractors. The data will therefore NOT
be merged soon with the regular data repository at CDDIS. The data is available
publicly in CDDIS in a dedicated area.
• In terms of RINEX 2/RINEX 3 the IC has been monitoring the recent problems
with the RINEX 3 definition and implementation by different means (binary translation, BNC, etc). Also, we are keeping the IGS community informed of the recent
Rx2.11 unofficial “extension” which is for experimental use.
• The IGS 2012 Workshop IC recommendations have been addressed and advanced.
• Two IC telecons have been held with good attendance across IC members and withthe raising of minutes and traceable actions.
• The IC has supported the RTPP in terms of data streaming and the NULL–ANTENNA issue, where certain antennas correct the antenna phase center variations directly on the streamed measurements, which is completely NOT allowed for
RINEX integration.

5 Strategic Plan Impact• The strategic Plan impact has been correctly filled out online.

6 Plan for 2014
• Over the next year, the IC will ensure that all the 2012 recommendations are addressed.
• The IC will continue to support transversally the IGS across all services, pilot
projects and experiments in infrastructure issues as they are discovered or brought
up to our attention.
• The IC will prepare and coordinate a poster session for the 2014 Workshop and plans
to hold a dedicated meeting during that week.

119

INFRASTRUCTURE COMMITTEE

120

CDDIS Global Data Center
Technical Report 2013
C. NollNASA Goddard Space Flight Center,
Code 690.1Greenbelt, MD 20771, USA
E-mail: Carey.Noll@nasa.gov

1 Introduction
The Crustal Dynamics Data Information System (CDDIS) is NASA’s data archive andinformation service supporting the international space geodesy community. For over
30 years, the CDDIS has provided continuous, long term, public access to the data
(mainly GNSS–Global Navigation Satellite System, SLR–Satellite Laser Ranging, VLBI–
Very Long Baseline Interferometry, and DORIS–Doppler Orbitography and Radiopositioning Integrated by Satellite) and products derived from these data required for a varietyof science observations, including the determination of a global terrestrial reference frameand geodetic studies in plate tectonics, earthquake displacements, volcano monitoring,
Earth orientation, and atmospheric angular momentum, among others. The specialized
nature of the CDDIS lends itself well to enhancement to accommodate diverse data setsand user requirements. The CDDIS is one of NASA’s Earth Observing System Data andInformation System (EOSDIS) distributed data archive centers; EOSDIS data centersserve a diverse user community and are tasked to provide facilities to search and accessscience data and products.
The CDDIS serves as one of the primary data centers and core components for the geometric services established under the International Association of Geodesy (IAG), an organization that promotes scientific cooperation and research in geodesy on a global scale.
The system has supported the International GNSS Service (IGS) as a global data center
since 1992. The CDDIS activities within the IGS during 2013 are summarized below; thisreport also includes any recent changes or enhancements made to the CDDIS.

121

CDDIS DC

2 System Description
The CDDIS archive of IGS data and products are accessible worldwide through anonymous
ftp. The CDDIS is located at NASA’s Goddard Space Flight Center (GSFC) and isavailable to users 24 hours per day, seven days per week.
The CDDIS computer system is fully redundant with the primary and secondary/failoversystem. Each system utilizes a distributed functionality (incoming, outgoing, processing,database, and map servers) and is configured with a local backup system as well as afull backup system located in a third building at GSFC. The archive is equipped with amulti–Tbyte RAID storage system and is scaled to accommodate future growth. All ftp
and web access is performed on the outgoing server. Data centers, stations, and analysis
centers push files to the CDDIS incoming server. Processing of incoming files for the on–line archive is performed in a separate environment that also includes a database server
for managing metadata extracted from incoming data.

3 Archive Content
As a global data center for the IGS, the CDDIS is responsible for archiving and providing
access to GNSS data from the global IGS network as well as the products derived fromthe analyses of these data in support of both operational and working group/pilot project
activities. The CDDIS archive is approximately 7.9 Tbytes in size of which 7.5 Tbytes are
devoted to GNSS data, products (300 Gbytes), and ancillary information. All data andproducts are accessible through subdirectories of ftp://cddis.gsfc.nasa.gov/gnss (asymbolic link to ftp://cddis.gsfc.nasa.gov/gps).

3.1 GNSS Tracking Data
The user community has access to GNSS data available through the on–line global data
center archives of the IGS. Over 50 operational and regional IGS data centers and station
operators make data (observation, navigation, and meteorological) available in RINEX format to the CDDIS from selected receivers on a daily, hourly, and sub–hourly basis. The
CDDIS also accesses the archives of the other three IGS global data centers, Scripps Institution of Oceanography (SIO) in California, the Institut Géographique National (IGN)
in France, and the Korea Astronomy and Space Science Institute (KASI) to retrieve (orreceive) data holdings not routinely transmitted to the CDDIS by an operational or regional data center. Tab. 1a and Tab. 1b below summarizes the types of IGS operational
GNSS data sets archived at the CDDIS.
Data, in RINEX V2.10 or V2.11 format, from GPS and GPS+GLONASS receivers arearchived within the main GNSS directory structure /gnss/data.

122

3 Archive Content
Table 1a: GNSS Data Type Summary
Data Type

Sample Rate

Daily GNSS
Hourly GNSS
High–rate GNSS
Satellite GPS

30 sec.
30 sec.
1 sec.
10 sec.

Data Format

AvailableOn–line

RINEX and compact RINEX
Compact RINEX
Compact RINEX
Compact RINEX

Since 1992
10+ years
Since May 2001
Since 2002

Table 1b: GNSS Data Archive Summary for 2013
Data Type

Daily GNSS
Hourly GNSS
High–rate GNSS
On–board GPS

Avg. No.
Sites/Day
475
290
155
1

Directory
Avg.
Total
Volume/Day Volume/Year Location
1100 Mb
383 Mb1900 Mb
0.5 Mb

400 Gb140 Gb695 Gb200 Mb/gnss/data/daily/gnss/data/hourly/gnss/data/highrate/gnss/data/satellite

Latency of
Majority of Data
Within 1 hourWithin 10 min.
Within 10 min.
Within 10 days

The CDDIS archives four major types/formats of GNSS data, all in RINEX format, as
described in Tab. 1a. Daily RINEX data are quality–checked, summarized, and archived to
public disk areas in subdirectories by year, day, and file type; the summary and inventory
information are also loaded into an on–line database. Nearly 153K daily station days from
520 distinct GNSS receivers were archived at the CDDIS during 2013. A complete listof daily, hourly, and high–rate sites archived in the CDDIS can be found in the yearlysummary reports at URL ftp://cddis.gsfc.nasa.gov/reports/gnss/.
Within minutes of receipt, the hourly GNSS files are archived to subdirectories by year,
day, and hour. These data are retained on–line indefinitely; the daily files delivered at theend of the UTC day contain all data from these hourly files and thus can be used in lieu
of the individual hourly files. A total of 360 hourly sites (4.5M files) were archived during
2013.
High–rate (typically 1–second sampling) GNSS data are archived in files containing fifteen
minutes of data and in subdirectories by year, day, file type, and hour. Many of thesedata files are created from real–time streams. Data from 175 high–rate sites (4.8M files)
were also archived in the CDDIS in 2013.
The CDDIS generates global broadcast ephemeris files (for both GPS and GLONASS) on
an hourly basis. These files are derived from the site–specific ephemeris data files for eachday/hour. These files are appended to a single file that contains the orbit information
for all GPS and GLONASS satellites for the day up through that hour. The merged
ephemeris data files are then copied to the day’s subdirectory within the hourly data filesystem. Within 1–2 hours after the end of the UTC day, after sufficient station–specific123CDDIS DC
Table 2: GNSS MGEX Data Archive Summary for 2013
Data Type

Average No.
Sites/Day

Average
Volume/Day

Directory Location

Daily GNSS
Hourly GNSS
High–rate GNSS

100
50
35

450 Mb90 Mb
850 Mb/gnss/data/campaign/mgex/daily/gnss/campaign/mgex/data/hourly/gnss/campaign/mgex/data/highratenavigation files have been submitted, this concatenation procedure is repeated to create
the daily broadcast ephemeris files (both GPS and GLONASS), using daily site–specificnavigation files as input. The daily files are copied to the corresponding subdirectoryunder the daily file system. Users can thus download this single, daily (or hourly) file
to obtain the unique navigation messages rather than downloading multiple broadcast
ephemeris files from the individual stations.
The CDDIS generates and updates status files, (/gnss/data/daily/YYYY/DDD/YYDD status) that summarize the holdings of daily GNSS data. These files include a list of stations.
The archive status files of CDDIS GNSS data holdings reflect timeliness of the data delivered as well as statistics on number of data points, cycle slips, and multipath. The user
community can receive a snapshot of data availability and quality by viewing the contentsof such a summary file.
The CDDIS successfully submitted a proposal to the IGS Multi–GNSS Experiment (MGEX)
call for proposals for archive and distribution of data and products. During 2013 the CDDIS continued the archiving of data from participating multi–GNSS receivers as well as
products derived from the analysis of these data. The data include newly available signals(e.g., Galileo, QZS, SBAS, and Beidou). The summary of the MGEX data holdings at
the CDDIS is shown in Tab. 2. Daily status files are also provided that summarize the
MGEX data holdings; however, data quality information available for operational GNSS
data holdings is not available through this software.
The GPS Directorate conducted the first test transmission of CNAV (civilian navigation)
messages on L2C– and L5–capable satellites in June 2013. The civilian navigation message
types will provide improved navigation through the use of the new L2C and L5 civilian
frequencies. The German Aerospace Center (DLR) and the University of New Brunswick(UNB) teamed up to collect the CNAV data with five multi–GNSS receivers in the U.S.,
Canada, South Africa, Singapore, and Australia. The team at DLR and UNB coordinatedarchive of the data with the CDDIS in support of the IGS MGEX.
Data from the permanent network of 20 GPS monitoring stations maintained by the
National Geospatial–Intelligence Agency (NGA) were archived in a special area of the
CDDIS for review by select IGS analysis centers. The data span the 2010–2012 timeframe. Once review has been completed the data will be archived in the operational124

3 Archive Content
Table 3: GNSS Product Summary
Number of
ACs/AACs

VolumeOrbits, clocks,
ERP, positions

14+Combinations

1.2 Gb/week

Troposphere

Combination

2.6 Mb/day,
940 Mb/year/gnss/products/troposphere/YYYY

Ionosphere

4+Combination

4 Mb/day,
1.5 Gb/year/gnss/products/ionex/YYYY

Real–time clocks

Combination

6.0 Mb/week/gnss/products/rtpp/YYYY

Product Type

Directory/gnss/products/WWWW(GPS, GPS+GLONASS)/glonass/products/WWWW(GLONASS only)(Note: WWWW=4–digit GPS week number; YYYY=4–digit year)

directories.

3.2 IGS Products
The CDDIS routinely archives IGS operational products (daily, rapid, and ultra–rapid
orbits and clocks, and weekly ERP and station positions) as well as products generated
by IGS working groups and pilot projects (ionosphere, troposphere, real–time clocks).
Tab. 3 below summarizes the GNSS products available through the CDDIS. The CDDIS
currently provides on–line access through anonymous ftp to all IGS products generated
since the start of the IGS Test Campaign in June 1992 in the file system /gnss/products;
products from GPS+GLONASS products are available through this filesystem. Products
derived from GLONASS data only continued to be archived at the CDDIS in a directory
structure within the file system /glonass/products .
The CDDIS also continues to archive combined troposphere estimates in directories by
GPS week. Global ionosphere maps of total electron content (TEC) from the IONEX
AACs are archived in subdirectories by year and day of year. Real-time clock comparison
products have been archived at the CDDIS in support of the IGS Real-Time Pilot Projectsince 2009.

3.3 Supporting Information
Daily status files of GNSS data holdings, reflecting timeliness of the data delivered as well
as statistics on number of data points, cycle slips, and multipath, continue to be generated

125CDDIS DC
by the CDDIS. By accessing these files, the user community can receive a quick look ata day’s data availability and quality by viewing a single file. The daily status files areavailable through the web at URL ftp://cddis.gsfc.nasa.gov/reports/gnss/status.
The daily status files are also archived in the daily GNSS data directories.
In preparation for the analysis center’s second reprocessing campaign, the CDDIS has developed site–specific reports detailing missing data. Station operators and operational
data centers can consult these lists (ftp://cddis.gsfc.nasa.gov/gnss/data/daily/
reports/missing) and if available, supply missing files to the CDDIS for inclusion in
the global data center archives.
Ancillary information to aid in the use of GNSS data and products are also accessible
through the CDDIS. Weekly and yearly summaries of IGS tracking data (daily, hourly,
and high–rate) archived at the CDDIS are generated on a routine basis. These summaries
are accessible through the web at URL ftp://cddis.gsfc.nasa.gov/pub/reports/gnss.
The CDDIS also maintains an archive of and indices to IGS Mail, Report, Station, andother IGS–related messages.

4 System Usage
Fig. 1 summarizes the usage of the CDDIS for the retrieval of GNSS data and products
in 2013. This figure illustrates the number and volume of GNSS files retrieved by theuser community during 2013, categorized by type (daily, hourly, high–rate, MGEX data,
products). Nearly 370 million files (over 50 Tbytes), excluding robot downloads, weretransferred in 2013, with an average of nearly 30 million files per month. Fig. 2 illustrates
the profile of users accessing the CDDIS IGS archive during 2013. The majority of CDDIS
users are from hosts in Europe, Asia, and North America.

5 Recent Developments
In support of the IGS Real–Time Pilot Project (RTPP) and Real–Time IGS Service, the
CDDIS has configured a server to provide a real–time streaming capability at GSFC.
The CDDIS installed the Ntrip (Networked Transport of RTCM via Internet Protocol)
software and successfully tested obtaining product streams from BKG and providing accessto streams to authorized users. A module was developed by EOSDIS colleagues to plug into
Ntrip that interfaces with an established User Registration System (URS) at NASA GSFC.
The module was specifically developed to easily interface with multiple user verification
systems and was given back to the community for possible future use. Testing continues
on the CDDIS caster installation and the Ntrip user registration module while the CDDIS
role in the Real–Time IGS Service is established.

126

5 Recent Developments

Figure 1: Number and volume of GNSS files transferred from the CDDIS in 2013.

Figure 2: Geographic distribution of IGS users of the CDDIS in 2013.

127

CDDIS DC
The CDDIS has recently made modifications to the metadata extracted from incoming
data and product files pushed to its archive. These enhancements have facilitated crossdiscipline data discovery by providing information about CDDIS archive holdings to otherdata portals such as Earth Observing System (EOS) Clearinghouse (ECHO) and future
integration into the Global Geodetic Observing System (GGOS) portal. The staff has
begun a metadata evolution effort, re–designing the metadata extracted from incoming
data and adding information that will better support EOSDIS applications such as ECHOand the metrics collection effort.
The CDDIS began discussions with the International Council for Science (ICSU) World
Data System (WDS) in 2011 to apply for membership. The CDDIS was previously accepted through the ILRS application as a network member. The WDS strives to enable
open and long–term access to multidisciplinary scientific data, data services, products andinformation. The WDS works to ensure long–term stewardship of data and data services
to a global scientific user community. In March 2013, the ICSU WDS Scientific Committee
accepted the CDDIS application for regular membership. A Letter of Agreement between
the CDDIS and ICSU was drafted and signed by C. Noll (on behalf of the CDDIS) and
D. Lowe (on behalf of EOSDIS, CDDIS funding organization).

6 Publications
The CDDIS staff attended several conferences during 2013 and presented papers on or
conducted demos of their activities within the IGS, including:Noll, C., M. Dube, N. Pollack, L. Tyahla, and P. Michael. Improvements in Space Geodesy
Data Discovery at the CDDIS, Abstract IN31C–1520 presented at 2013 Fall Meeting,
AGU, San Francisco, Calif., 09–13 Dec., 2013.
Electronic versions of this poster and other publications can be accessed through the
CDDIS on–line documentation page on the web at URL http://cddis.gsfc.nasa.gov/
reports.html.

7 Future Plans
The CDDIS will continue to support the IGS MGEX. The experiment is an excellent
opportunity to prepare the data centers for archive of data in RINEX V3. The CDDIS
will coordinate with the Data Center Working Group and other IGS data centers to
introduce RINEX V3 data into the “operational” GNSS data directory structure, making
it easier for users to access these data.

128

9 Acknowledgments
The CDDIS plans to make its real–time caster operational in the coming year as part of the
IGS Real–Time Service. Possible future activities in the real–time area include capturing
the streams for generation of 15–minute high–rate files for archive at the CDDIS.
In 2013, the IGS analysis centers will begin providing products for the second IGS reprocessing campaign (repro2). The CDDIS will provide support through upload of files fromthe ACs and online archive of these products (/gnss/products/WWWW/repro2).
Work on an update of the CDDIS website began in 2013. In addition to a refresh of theappearance of the website, the content was reviewed and updated. Applications that areunder development for data discovery (e.g., a CDDIS implementation of GSAC and a sitelog browser) will be completed in early 2014 and integrated into the new CDDIS website.
The update is planned for completion in early 2014.
The CDDIS has cooperated in the development of Geodetic Seamless Archive Centers(GSAC) with colleagues at UNAVCO, SIO, and the University of Nevada at Reno. The
activity provides web services to facilitate data discovery within and across participatingarchives. The prototype implementation of these GSAC web services at the CDDIS wasdeveloped; plans are to incorporate the application in the revised CDDIS website in early2014.
Funding has been identified in 2014 to procure a system refresh for the CDDIS. The
CDDIS system engineer will review current and near–term requirements and develop a
hardware procurement strategy.

8 Contact Information
To obtain more information about the CDDIS IGS archive of data and products, contact:
Ms. Carey E. Noll
Manager, CDDIS
Code 690.1
NASA GSFC
Greenbelt, MD 20771, USA

Phone: (301) 614–6542
Fax: (301) 614–6015
E–mail: Carey.Noll@nasa.gov
Website: http://cddis.gsfc.nasa.gov
http://cddis.nasa.gov

9 Acknowledgments
The author would like to thank the CDDIS contractor staff, Patrick Michael, Maurice Dube, Nathan Pollack, and Rebecca Limbacher (Science Systems and Applications,Inc./SSAI), Lori Tyahla (Stinger Ghaffarian Technologies/SGT), and James Roark (ADNET Systems). The recognition and success of the CDDIS in many international programs
can be directly attributed to the continued dedicated, consistent, professional, and timely
support of its staff.

129

CDDIS DC

References
Noll, C. The Crustal Dynamics Data Information System: A resource to support scientificanalysis using space geodesy. Advances in Space Research, 45(12):1421–1440, ISSN
0273–1177, 2010. doi: 10.1016/j.asr.2010.01.018.
Noll, C., Y. Bock, H. Habrich, and A. Moore. Development of data infrastructure to
support scientific analysis for the International GNSS Service. Journal of Geodesy, 83(3–4):309–325, 2009. doi: 10.1007/s00190-008-0245-6.

130

Part IV

Working Groups, Pilot Projects

131

IGS Antenna Working GroupR. Schmid
Deutsches Geodätisches Forschungsinstitut
Alfons–Goppel–Str. 11, 80539 München, Germany
E-mail: schmid@dgfi.badw.de

1 Updates and content of the antenna phase center model
Tab. 1 lists 15 updates of the absolute IGS antenna phase center model igs08_wwww.atx
for 2013. Nine of them are related to changes of the satellite constellation, and four times
an update of the model was released, when new receiver antenna calibrations became
available. With the update in GPS week 1734, erroneous spikes were removed from the
GLONASS calibrations of nearly 50 different receiver antenna types.
In GPS week 1745, the satellite antenna phase center variations (PCVs) of GPS Block II,
IIA, IIR–A, IIR–B, IIR–M and IIF were extended with correction values for nadir angles
between 15◦ and 17◦ provided by CODE (see Fig. 1 and Tab. 2). Those are based on
ionosphere–free GPS data of the low Earth orbiter (LEO) missions Jason–2, GRACE–A,
GRACE–B, GOCE, and MetOp–A and are mainly relevant for the analysis of LEO data.
Further details on all model changes can be found in the corresponding IGSMAILs whose
numbers are also given in Tab. 1.
Tab. 3 gives an overview of the data sets contained in the IGS phase center model. The
numbers refer to igs08_ 1771.atx that was released in December 2013. For GPS andGLONASS, there are 77 and 89 file entries, respectively. These numbers are bigger than
the number of actual satellites, as certain satellites were assigned with different PRN codes
or almanac slots, respectively.
During the IGS Workshop 2012 in Olsztyn, it was recommended to adopt conventional
phase center offset (PCO) values for Galileo, BeiDou and QZSS. As the update of the
ANTEX format w.r.t. manufacturer–defined spacecraft body frames and attitude modes
is still pending, the IGS phase center model does still not provide any information on the
new GNSS. For the time being, conventional PCO values can be found on the web pagesof the IGS Multi–GNSS Experiment (http://www.igs.org/mgex/).
Apart from the satellite antennas, the IGS model meanwhile contains phase center calibration values for 255 different receiver antennas. 84 of them are certain combinations of133

1 Updates and content of the antenna phase center model

Table 1: Updates of the phase center model igs08_wwww.atx (wwww being the GPS week of therelease date) in 2013. Model updates restricted to additional receiver antenna types are
only announced via the IGS Equipment Files mailing list.
week

date

IGSMAIL

1722

07–JAN–13

6711

1730

05–MAR–13

6743

1731
1734

14–MAR–13
05–APR–13

—
6753

1735

12–APR–13

—

1737
1739

26–APR–13
10–MAY–13

—
6771

1740
1745

16–MAY–13
20–JUN–13

6775
6786

1748

08–JUL–13

6789

1755

27–AUG–13

6818

1758

18–SEP–13

6825

1764

29–OCT–13—

1769

06–DEC–13

6843

1771

20–DEC–13

6845

134

changeAdded R743 (R08), R801 (R08)
Decommission date: R712 (R08), R743 (R08), R801 (R26)
Added R743 (R08), R801 (R26)
Decommission date: R801 (R08)
Added TRMR10NONE
Spikes removed from GLONASS calibrations of 46 receiverantenna types
Added TPSCR.G5
TPSH
TRMR4–3
NONE
TRMR6–4
NONE
TRMR8–4NONE
TRMSPS985
NONE
Added ITT3750323
SCIS
Added G049 (G30)
Decommission date: G035 (G30), G049 (G27)
Spikes removed from GLONASS calibrations of 2 receiverantenna types
Added G066
PCVs of GPS Block II/IIA/IIR–A/IIR–B/IIR–M/IIF satellites
extended to a maximum nadir angle of 17 degrees
Added R747
Decommission date: R728
Added NOV703GGG.R2
NONE
Added G032 (G30)
Decommission date: G049 (G30)
Added G037 (G30)
Decommission date: G032 (G30)
Added CHCX91+S
NONE
LEIICG60
NONE
NOV750.R5
NOVS
TIAPENG2100B
NONE
TIAPENG2100R
NONE
Added G027 (G30)
Decommission date: G037 (G30)
Added G049 (G30)
Decommission date: G027 (G30)

1 Updates and content of the antenna phase center model

45
Block I
Block II/IIA
Block IIR−A
Block IIR−B/M
Block IIF

PCV [mm]

30

15

0

−15
0

2

4

6
8
10
12
Nadir angle [deg]14 15 16 17

Figure 1: Extension for the GPS satellite antenna PCVs as provided by CODE. PCV values
for nadir angles ≤ 14◦ (dashed lines) are identical with the original igs08.atx values, whereas those for nadir angles > 14◦ (solid lines) were derived from LEO data.
Block IIA PCVs (green) were extended with constant values and had to be constrained.
Block I (black) could not be considered, as all Block I satellites already had been decommissioned when the first GPS–based LEO mission was launched.
Table 2: GPS satellite antenna PCV values [mm] for nadir angles between 14◦ and 17◦ in use
since GPS week 1745.
Nadir angle
Block I
Block II/IIA
Block IIR-A
Block IIR-B/M
Block IIF

14◦

15◦

16◦

17◦

−0.30
−0.90
−1.40
+12.10
+5.70

–
−0.90
−0.80
+22.00+12.40

–
−0.90
+2.00
+30.40+18.20

–
−0.90
+6.40
+40.60+23.50

Table 3: Number of data sets in igs08_ 1771.atx (released in December 2013).
satellite antennas
GPS
GLONASS
Galileo
BeiDouQZSS

number77
89
0
00

receiver antennas
ROBOT
FIELD
COPIEDCONVERTED

number
119
90
32
14

135

2 Calibration status of the IGS networkan antenna and a radome, whereas the remaining 171 antenna types are not covered bya radome. As Tab. 3 shows, igs08_ 1771.atx contains, among others, 119 absolute robot
calibrations and 90 converted field calibrations.
As elevation– and azimuth–dependent calibration values down to 0◦ elevation are mandatory for new or upgraded IGS stations, 154 different antenna types (119 ROBOT + 32 COPIED+ 3 CONVERTED) are currently approved for installation. The remaining 101 types are nolonger allowed, but their calibration values are still necessary for existing installations (seeSection 2) as well as for reprocessing purposes.

2 Calibration status of the IGS network
Tab. 4 shows the percentage of IGS tracking stations with respect to certain calibration
types. For this analysis, 437 IGS stations as contained in the file logsum.txt (available at
ftp://igs.org/igscb/station/general/) on 15 January 2014 were considered. At thattime, 103 different antenna/radome combinations were in use within the IGS network. The
calibration status of these antenna types was assessed with respect to the phase centermodel igs08_ 1771.atx that was released in December 2013.
Seven years after the adoption of absolute robot calibrations by the IGS in November
2006, state–of–the–art calibrations comprising elevation– and azimuth–dependent PCVs
down to the horizon are available for nearly 80% of all IGS stations. Whereas the portionof stations with phase center corrections derived from relative field calibrations (purely
elevation–dependent) hardly changed in recent years, a steady decrease of IGS stations
covered by uncalibrated radomes can be noticed.
This decrease results from an upgrade of the equipment at operational stations or fromthe decommissioning of stations with outdated equipment, but also from an extension of
the network with properly calibrated antennas. In order to reach a coverage of 100%, IGS
Site Guidelines do not allow converted field calibrations or uncalibrated equipment “atnew or upgraded stations”.
Table 4: Calibration status of 437 stations in the IGS network (logsum.txt of 15 January 2014,
igs08_ 1771.atx) compared to former years.

date
DEC 2009
MAY 2012
JAN 2013
JAN 2014

136

absolute calibration(azimuthal corrections
down to 0◦ elevation)

converted field calibration(purely elevation–dependent
PCVs above 10◦ elevation)

uncalibrated radome(or unmodeled
antenna subtype)

61.4%
74.6%
76.8%
78.7%

18.3%
8.2%
7.7%
7.8%

20.2%
17.2%
15.5%
13.5%

Activities of IGS Bias and Calibration
Working Group
S. Schaer
Swiss Federal Office of Topography swisstopo
Seftigenstrasse 264, CH–3084 Wabern, Switzerland
stefan.schaer@aiub.unibe.ch / stefan.schaer@swisstopo.ch

1 Introduction
The IGS Bias and Calibration Working Group (BCWG) coordinates research in the fieldof GNSS bias retrieval and monitoring. It defines rules for appropriate, consistent handling of biases which are crucial for a “model–mixed” GNSS receiver network and satellite
constellation, respectively. At present, we consider: P1–C1, P2–C2, and P1–P2 differential code biases (DCB). Potential quarter-cycle biases between different phase observables(specifically L2P and L2C) are another issue to be dealt with. In the face of GPS andGLONASS modernization programs and upcoming GNSS, like the European Galileo and
the Chinese BeiDou, an increasing number of types of biases is expected.
The IGS BCWG was established in 2008. More helpful information and related internet
links may be found at http://igs.org/projects/bcwg/. For an overview of relevant
GNSS biases, the interested reader is referred to (Schaer 2012).

2 Activities in 2013
• Regular generation of P1–C1 bias values for the GPS constellation (based on indirect
estimation, see Fig. 1) and maintenance of receiver class tables was continued at
CODE/AIUB.
• P1–P2 bias values for GPS and GLONASS (see Fig. 2 and Fig. 3.) are a by-productof the ionosphere analysis.
• The tool developed for direct estimation of GNSS P1–C1 and P2–C2 DCB values isused to generate corresponding GPS and GLONASS bias results on a regular basis(see Fig. 4, Fig. 5, and Fig. 6). Note that R26, actually representing a 25th active

137

Schaer: Bias and Calibration Working Group5

BLOCK IIABLOCK IIR−M

BLOCK IIF

BLOCK IIR−ABLOCK IIR−B

3
2
1
0
−1
−2
−3
−4

G03
G04
G06
G08
G09
G10
G26
G32
G01
G24
G25
G27
G11
G13
G14
G16
G18
G20
G21
G28
G02
G19
G22
G23
G05
G07
G12
G15
G17
G29
G30
G31

DCB(p1c1) in ns

4−5

Satellites
Figure 1: Monthly set of P1–C1 differential code biases for the GPS constellation, for January
2014, computed at CODE.

20BLOCK IIABLOCK IIR−M

BLOCK IIFGLONASS−M

BLOCK IIR−ABLOCK IIR−B

10
5
0
−5
−10
−15

G03
G04
G06
G08
G09
G10
G26
G32
G01
G24
G25
G27
G11
G13
G14
G16
G18
G20
G21
G28
G02
G19
G22
G23
G05
G07
G12
G15
G17
G29
G30
G31
R01
R02
R03
R04
R05
R06
R07
R08
R09
R10
R11
R12
R13
R14
R15
R16
R17
R18
R19
R20
R21
R22
R23
R24

DCB(p1p2) in ns

15

−20

Satellites
Figure 2: Monthly set of P1–P2 differential code biases for the GPS and GLONASS constellation,
for January 2014, computed at CODE.

138

2 Activities in 2013

DCB(p1p2) in ns

60

AOA BENCHMARK ACT
ASHTECH Z−XII3TJPS E_GGD
LEICA GRX1200+GNSSNOV OEMV3SEPT POLARX4TPS LEGACYTRIMBLE 4000SSITRIMBLE NETR9AOA SNR−12 ACT
JAVAD TRE_G3T DELTA
JPS LEGACYLEICA GRX1200GGPROROGUE SNR−8000
SEPT POLARX4TR
TPS NET−G3A
TRIMBLE 5700
TRIMBLE NETRSASHTECH UZ−12
JAVAD TRE_G3TH DELTA
LEICA GR10
LEICA GRX1200PROSEPT POLARX2TPS EUROCARDTPS NETG3
TRIMBLE NETR5

ASHTECH Z−XII3
JPS EGGDTLEICA GR25
NOV OEM4−G2
SEPT POLARX3ETRTPS E_GGDTPS ODYSSEY_E
TRIMBLE NETR8

40
20
0
−20
−40
−60

Stations

DCB(p1p2) in ns

60

AOA BENCHMARK ACT
ASHTECH Z−XII3TJPS E_GGD
LEICA GRX1200+GNSSNOV OEMV3SEPT POLARX4TPS LEGACYTRIMBLE 4000SSITRIMBLE NETR9AOA SNR−12 ACT
JAVAD TRE_G3T DELTA
JPS LEGACYLEICA GRX1200GGPROROGUE SNR−8000
SEPT POLARX4TR
TPS NET−G3A
TRIMBLE 5700
TRIMBLE NETRSASHTECH UZ−12
JAVAD TRE_G3TH DELTA
LEICA GR10
LEICA GRX1200PROSEPT POLARX2TPS EUROCARDTPS NETG3
TRIMBLE NETR5

ASHTECH Z−XII3
JPS EGGDTLEICA GR25
NOV OEM4−G2
SEPT POLARX3ETRTPS E_GGDTPS ODYSSEY_E
TRIMBLE NETR8

40
20
0
−20
−40
−60

Stations
Figure 3: Monthly set of P1–P2 differential code biases for the GPS (top) and GLONASS (bottom) receiver components, for January 2014, computed at CODE.

139

Schaer: Bias and Calibration Working GroupGLONASS satellite, did already appear in the corresponing P1–C1 bias product (seealso IGSMAIL #6581).
• The ambiguity resolution scheme at CODE was extended to GLONASS for three
resolution strategies. It is essential that self-calibrating ambiguity resolution procedures are used. Resulting GLONASS DCPB(differential code-phase bias) results arecollected and archived regularly.
• More experience could be gained concerning station-specific GLONASS-GPS intersystem translation parameters, which are estimated and accumulated as part of
CODE’s IGS analysis (but completely ignored for all submissions to IGS).
• A key achievement was the activation of a flexible, RINEX3-oriented RINEX observable selection scheme for all CODE analysis lines in August 2013.
• CODE’s enhanced RINEX observation data monitoring was continued. Examples
may be found at:
ftp://ftp.unibe.ch/aiub/igsdata/odata2_day.txt
ftp://ftp.unibe.ch/aiub/igsdata/odata2_receiver.txt
ftp://ftp.unibe.ch/aiub/igsdata/y2012/odata2_d335.txt
ftp://ftp.unibe.ch/aiub/igsdata/y2012/odata2_d335_sat.txt• This RINEX monitoring service was extended to MGEX observation data (available
in RINEX3 format). See ftp://ftp.unibe.ch/aiub/mgex/y2013/.

3 Last Reprocessing Activities
In 2012: A complete GPS/GLONASS DCB reprocessing was carried out at CODE on thebasis of 1990–2011 RINEX data. The outcome of this P1–C1 and P2–P2 DCB reprocessing
effort is: daily sets, a multitude of daily subsets, and in addition monthly sets. Analysis
and combination of these remarkably long time series must be seen as a medium-term (orlong-term) goal.

References
Schaer, S. Activities of IGS Bias and Calibration Working Group. In: Meindl, M., R. Dach,
Y. Jean (Eds): IGS Technical Report 2011, Astronomical Institute, University of Bern,
July 2012, pp. 139–154.
Schaer, S. Activities of IGS Bias and Calibration Working Group. In: R. Dach and Y. Jean
(Eds): IGS Technical Report 2012, Astronomical Institute, University of Bern, Apri2013, pp. 149–152.

140

−4

−5
R26
G03
G04
G06
G08
G09
G10
G26
G32
G01
G24
G25
G27
G11
G13
G14
G16
G18
G20
G21
G28
G02
G19
G22
G23
G05
G07
G12
G15
G17
G29
G30
G31
R01
R02
R03
R04
R05
R06
R07
R08
R09
R10
R11
R12
R13
R14
R15
R16
R17
R18
R19
R20
R21
R22
R23
R24

DCB(p1c1) in ns
4

G01
G24
G25
G27
G05
G07
G12
G15
G17
G29
G30
G31
R01
R02
R03
R04
R05
R06
R07
R08
R09
R10
R11
R12
R13
R14
R15
R16
R17
R18
R19
R20
R21
R22
R23
R24

DCB(p2c2) in ns

References

5

BLOCK IIR−B

BLOCK IIF
BLOCK IIABLOCK IIR−M

BLOCK IIR−M

BLOCK IIFGLONASS−M
BLOCK IIR−A

3

2

1

0

−1

−2

−3

−5

Satellites

GLONASS−M

50Satellites

Figure 4: Monthly set of P1–C1 (top) and P2-C2 (bottom) differential code biases for the GPS
and GLONASS constellation, for January 2014, computed at CODE.

141

Schaer: Bias and Calibration Working Group

DCB(p1c1) in ns????????????????????
ASHTECH Z−XII3
JAVAD TRE_G3TH DELTA
SEPT POLARX2TPS EUROCARDTPS NETG3
TRIMBLE NETR9AOA BENCHMARK ACT
ASHTECH Z−XII3TJPS EGGDTSEPT POLARX3ETRTPS E_GGDTPS ODYSSEY_E
TRIMBLE NETRSAOA SNR−12 ACTDICOM GTR50
JPS E_GGD
SEPT POLARX4TPS LEGACYTRIMBLE NETR5

ASHTECH UZ−12
JAVAD TRE_G3T DELTA
JPS LEGACYSEPT POLARX4TR
TPS NET−G3A
TRIMBLE NETR8

5
4
3
2
1
0
−1
−2
−3
−4
−5
−6
−7
−8
−9
−10

Stations

DCB(p1c1) in ns????????????????????
ASHTECH Z−XII3
JAVAD TRE_G3TH DELTA
SEPT POLARX2TPS EUROCARDTPS NETG3
TRIMBLE NETR9AOA BENCHMARK ACT
ASHTECH Z−XII3TJPS EGGDTSEPT POLARX3ETRTPS E_GGDTPS ODYSSEY_E
TRIMBLE NETRSAOA SNR−12 ACTDICOM GTR50
JPS E_GGD
SEPT POLARX4TPS LEGACYTRIMBLE NETR5

ASHTECH UZ−12
JAVAD TRE_G3T DELTA
JPS LEGACYSEPT POLARX4TR
TPS NET−G3A
TRIMBLE NETR8

5
4
3
2
1
0
−1
−2
−3
−4
−5
−6
−7
−8
−9
−10

Stations
Figure 5: Monthly set of P1–C1 differential code biases for the GPS (top) and GLONASS (bottom) receiver components, for January 2014, computed at CODE.

142

References????????????????????
LEICA GR10
SEPT POLARX3ETRTPS NETG3
TRIMBLE NETRSASHTECH UZ−12
LEICA GR25
SEPT POLARX4TRIMBLE NETR5

JAVAD TRE_G3T DELTA
LEICA GRX1200+GNSSSEPT POLARX4TR
TRIMBLE NETR8JAVAD TRE_G3TH DELTA
LEICA GRX1200GGPROTPS NET−G3A
TRIMBLE NETR93

DCB(p2c2) in ns

2
1
0
−1
−2
−3
−4
−5
−6
−7

Stations????????????????????
LEICA GR10
SEPT POLARX3ETRTPS NETG3
TRIMBLE NETRSASHTECH UZ−12
LEICA GR25
SEPT POLARX4TRIMBLE NETR5

JAVAD TRE_G3T DELTA
LEICA GRX1200+GNSSSEPT POLARX4TR
TRIMBLE NETR8JAVAD TRE_G3TH DELTA
LEICA GRX1200GGPROTPS NET−G3A
TRIMBLE NETR93

DCB(p2c2) in ns

2
1
0
−1
−2
−3
−4
−5
−6
−7

Stations
Figure 6: Monthly set of P2–C2 differential code biases for the GPS (top) and GLONASS (bottom) receiver components, for January 2014, computed at CODE.

143

IGS Data Center Working Group 2013
C. NollNASA Goddard Space Flight Center,
Code 690.1, Greenbelt, MD 20771, USA
E-mail: Carey.Noll@nasa.gov

1 Introduction
The IGS Data Center Working Group (DCWG) was established in 2002. The DCWG
tackles many of the problems facing the IGS data centers as well as develops new ideas
to aid users both internal and external to the IGS. The direction of the IGS has changed
since its start in 1992 and many new working groups, projects, data sets, and products
have been created and incorporated into the service since that time. The DCWG wasformed to revisit the requirements of data centers within the IGS and to address issues
relevant to effective operation of all IGS data centers, operational, regional, and global.

2 Recent Activities
A Data Center Working Group meeting was held during IGS 2012 Workshop in Olsztyn,
Poland. Recommendations where made resulting from presentations during the workshop
and from splinter meeting discussions. Major topics discussed were the proposed changes
to the RINEX file naming convention, handling multiple releases of files at the data centers,
and archiving RINEX V2 and V3 at the data centers.
The Data Center Working Group continues to address these recommendations A new
file naming convention to support RINEX V3 data has been proposed but remains in
discussion within the RINEX Working Group. Although filename changes directly affectoperations, resulting in a significant workload for data centers, a new convention willremove some difficulties DCs have experienced in handling two major versions of RINEX
files. For example, the confusion that can be caused by the fact that both RINEX V2 andV3 files currently share the same filename structure.
The DCWG coordinated the directory structure utilized by the data centers in supportof the IGS Multi–GNSS Experiment (MGEX). Because of the experimental nature of144

3 Future Plans
MGEX, the data and products are archived in a directory structure separate from theoperational directories containing data in RINEX V2 format. At the request of the IGS
Infrastructure Committee, all RINEX V3 data available previously at the data centers
have been consolidated within the MGEX directory structure thus simplifying access forthe user community. Care must be taken, however, by both data suppliers and the data
centers to ensure that, until a new RINEX V3 file naming convention is adopted, that
RINEX V2 and V3 data remain in separate directories since they utilize the same filename
structure.

3 Future Plans
In 2014–2015, the DCWG will continue to work on addressing recommendations from the
IGS 2010 and 2012 workshops. Topics the WG hopes to address follow.
• Support of the IGS Infrastructure Committee: A major focus of the DCWG will
be to support the IC in its various activities to coordinate the resolution of issues
related to the IGS components. These activities will address recommendations fromrecent IGS Workshops including assessment and monitoring of station performanceand data quality, generating metrics on these data.
• Repro2: The DCWG will work with the IGS ACC and coordinate the archival of
IGS repro2 products at the IGS Global Data Centers.
• RINEX file naming convention: The DCWG will work with the IC and the RINEXWG on the new IGS RINEX file naming convention.
• Data center harmonization: The working group will consider methodologies for ensuring key data sets are available at all GDCs. Following recommendations fromthe IGS 2010 Workshop, the WG will coordinate with GDCs to ensure all GDCs
archive data from all IGS stations as identified on the IGS network website; ODCs
push data, and any subsequent resubmissions, from their stations to ALL GDCs and
ODCs issues advisory for ALL resubmissions.
• Compression: As per a recommendation from the IGS 2010 and 2012 workshops,
the DCWG will develop a plan for the introduction of a new compression scheme
into the IGS infrastructure by evaluating tests of available tools, surveying the IGS
infrastructure, making a recommendation on a new IGS compression scheme, andcoordinating recommendations with the IC to develop implementation schedule.
• Real–time data streams/high–rate GNSS data handling: IGS data centers mustensure that files generated from these streams are sufficiently reliable. The DCs
must also coordinate to ensure consistent copies of high–rate files are archived. This
recommendation from 2010 IGS Workshop includes definition and development of1) tool for comparison of RINEX files from various construction approaches, 2)

145

DATA CENTER WG
minimum requirements for acceptance of an accumulated data stream of observations
as a RINEX file in IGS data archives, 3) mandatory/optional observation types
to be included, 4) procedures to fill the gaps in the case data streams have beeninterrupted. This activity should be coordinated with the RTPP, ACs, DCs, and IC.
A related recommendation resulted from the 2012 IGS Analysis Workshop statingthat until the RINEX V3 filenaming convention is finalized, separate directories for
distinguishing between files created from streams and by receivers will be establishedby all DCs.
• Next meeting: A meeting of the DCWG is planned for the 2014 IGS Workshop in
July 2014.

4 Membership• Carey Noll (NASA GSFC/USA), Chair• Yehuda Bock (SIO/USA)• Ludwig Combrinck (HRAO/South Africa)• Bruno Garayt (IGN/France)• Jake Griffiths (NOAA/USA), ex–officio• Heinz Habrich (BKG/Germany)• Michael Moore (GA/Australia) (tbc)• Ruth Neilan (JPL/USA), ex–officio• Markus Ramatschi (GFZ/Germany)• Jim Ray (NOAA/USA)• Nacho.Romero (ESA/Germany)• Mike Schmidt (NRCan/Canada)• Giovanni Sella (NOAA/USA)• Grigory Steblov (RDAAC/Russia)• Dave Stowers (JPL/USA)146

IGS Ionosphere Working Group
Technical Report 2013
A. Krankowski, Y. Cherniak, and I. Zakharenkova
Geodynamics Research Laboratory
University of Warmia and Mazury(GRL/UWM)
in Olsztyn, Poland

1 General goals
The Ionosphere Working group started the routine generation of the combine Ionosphere
Vertical Total Electron Content (TEC) maps in June 1998. This has been the main activity so far performed by the four IGS Ionosphere Associate Analysis Centers (IAACs):
CODE (Center for Orbit Determination in Europe, Astronomical Institute, University ofBerne, Switzerland), ESOC (European Space Operations Center of ESA, Darmstadt, Germany), JPL (Jet Propulsion Laboratory, Pasadena, California, U.S.A), and UPC (Technical University of Catalonia, Barcelona, Spain). Independent computation of rapid andfinal VTEC maps is used by the each analysis centers: Each IAACs compute the rapid
and final TEC maps independently and with different approaches including the additional
usage of GLONASS data in the case of CODE.

2 Membership
Dieter Bilitza
M. Codrescu
Patricia H. Doherty
Joachim Feltens
Alberto Garcia–Rigo
Pierre Heroux
Attila Komjathy
Richard B. LangleyMaria Lorenzo
Raul Orus
Ola Ovstedal
Jaime Fernandez Sanchez
Javier Tegedor
Robert Weber
Brian Wilson
Mahdi Alizadeh

GSFC/NASA
SEC
BC
ESA/ESOC
UPC
NRCAN
JPL
UNB
ESA/ESOC
UPC
UMB
ESA/ESOC
ESA/ESOC
TU WienJPL
TU Vienna

Ljiljana R. Cander
Anthea Coster
John Dow
Mariusz Figurski
Manuel Hernandez–Pajares
Norbert Jakowski
Andrzej Krankowski
Reinhard Leitinger
A. Moore
Michiel Otten
Ignacio Romero
Schaer Stefan
Rene Warnant
Pawel Wielgosz
Michael Schmidt

RAL
MIT
ESA/ESOC
MUT
UPC
DLR
UWM
TU Graz
JPL
ESA/ESOC
ESA/ESOC
CODE
ROB
UWM
DGFI

147

IONOSPHERE WG

3 Productsa) final GIM (please note that GIMs also include GPS and GLONASS stations’ andsatellites’ DCBs)• combination of CODE, ESA, JPL and UPC iono products conducted by UWM• temporal and spatial resolution – at 2hr ×5◦ ×2.5◦ (UT×Lon.×Lat.)• availability with a latency of 11 daysb) rapid GIM• combination of CODE, ESA, JPL and UPC iono products conducted by UWM• temporal and spatial resolution – at 2hr ×5◦ ×2.5◦ (UT× Lon.×Lat.)• availability with a latency of less than 24 hoursc) predicted GIM for 1 and 2 days ahead (pilot product)• combination of ESA and UPC iono products conducted by ESA• temporal and spatial resolution – at 2hr ×5◦ ×2.5◦ (UT× Lon.×Lat.)

4 Key accomplishmentsa) IGS Global ionosphere predicted products for 1 and 2 days ahead (pilot product). This
new IGS products are currently based on predicted ionosphere maps prepared by UPC
and ESA.
b) IGS Global ionosphere maps with 1 hour and 15 min. time resolution (pilot products).
This new IGS products are currently based on ionosphere maps prepared by UPC and
ESA.
c) IGS Global Ionosphere Maps (GIMs) now include differential code biases (DCBs) for
GLONASS satellites.
d) The pilot phase of the new IGS ionospheric product – TEC fluctuations maps

5 The pilot phase of the new IGS ionospheric product – TEC
fluctuations maps
It is known that GNSS radio signals passing through the ionosphere suffer varying degrees
of rapid variations of their amplitude and phase – signal fluctuations, referred as scintil-148

5 The pilot phase of the new IGS ionospheric product – TEC fluctuations maps
lations, are created by random fluctuations of the medium’s refractive index, which arecaused by inhomogeneities inside the ionosphere. These effects are caused by the presenceof a wide range of scale size irregularities in the ionosphere.
Currently, there is a high demand to increase the precision and reliability of GNSS positioning. The spatial and temporary dynamics of the ionosphere fluctuations depends on
geophysical conditions, and knowledge of this is very important, especially during space
weather events. For this reason several approaches to analyze the ionospheric total electron
content (TEC) fluctuations effects on GNSS signals have been carried out.
The ionospheric fluctuations service for the Northern hemisphere mid–latitudes and sub–auroral regions is strongly actual as a lot of GNSS precise positioning users are locatedin this area. The IGS service, illustrated the variability of the TEC fluctuations, waspresented in 2012 and developed in 2013.
According to the resolution of the IGS Ionosphere Working Group, which has been passed
during the IGS Workshop 2012 in Olsztyn, the new product – the ionospheric fluctuations
maps – was established as a pilot project of the IGS service.
Taking into account that the Earth ionosphere is formed by superimposing of Earth magnetic field and Solar irradiance level for the geomagnetic field the TEC fluctuations arecalculated as a function of a spherical geomagnetic latitude and magnetic local time.

Figure 1: The locations of the stations
around the North Geomagnetic
Pole.

Figure 2: The grid of ROTI maps in polar coordinates with grid 2 degree (magnetic
local time) and 2 degree (geomagnetic
latitude).

149

IONOSPHERE WG

Figure 3: The example of ROTI map forthe geomagnetic quiet day.

Figure 4: The example of ROTI map for thegeomagnetic disturbed day.

In the updated version, more than 700 permanent stations (available both from UNAVCO
and EUREF databases) have been involved into analysis of the ionosphere fluctuation
service. In order to describe the TEC variability in the ionosphere, the Rate of TEC(ROT) and its deviation – Rate of TEC Index (ROTI) are used. The ROT is calculated
as the difference of two geometry–free observations for consecutive epochs. The ROTI
represents the ROT deviation over 5 minute periods with one minute resolution. This
ionospheric fluctuations service allows to estimate the levels of TEC fluctuations for spatial
range from 50 degree of the north geomagnetic latitude to the North Geomagnetic Pole.
The results have visualization as daily ROTI maps in polar coordinates with grid 2 degree(magnetic local time) and 2 degree (geomagnetic latitude). The every grid cell represents
the average weighted value of ROTI values included in this cell.
The final TEC fluctuations maps are written in the modified IONEX format. During thepilot phase the graphical form of the products can be found at: http://igsiono.uwm.
edu.pl.

6 Publications 2012–2013
Bilitza D., Brown S. A., Wang M. Y., Souza J. R., Roddy P. A. Measurements and IRI
model predictions during the recent solar minimum, Journal of Atmospheric and Solar–
Terrestrial Physics, 86:99–106. 2012.
Cherniak Iu. V., Zakharenkova I. E., Krankowski A., Shagimuratov I. I. Plasmasphericelectron content derived from GPS TEC and FORMOSAT–3/COSMIC measurements:
solar minimum condition, Advances in Space Research, 50(4):427–440. 2012.
DOI:10.1016/j.asr.2012.04.002

150

7 Plan for activities in 2014:
Galkin I. A., Reinisch B. W., Huang X., Bilitza D. Assimilation of GIRO data into areal–time IRI, Radio Science, 47(4). 2012. DOI: 10.1029/2011RS004952.
Hernández–Pajares M, García–Rigo A., Sanz J., Monte E., Aragón–Àngel A., GNSS measurement of EUV photons flux rate during strong and mid solar flares. Space Weather
10(12). 2012. DOI:10.1029/2012SW000826.
Hernández–Pajares M, Juan J. M., Sanz J., Aragón–Àngel A. Propagation of medium
scale traveling ionospheric disturbances at different latitudes and solar cycle conditions,Radio Science, 47(6). 2012. DOI: 10.1029/2011RS004951.
Shagimuratov I. I., Krankowski A., Ephishov I., Cherniak Yu., Wielgosz P., Zakharenkova
I. High latitude TEC fluctuations and irregularity oval during geomagnetic storms, Earth,Planets and Space, 64(6):521–529. 2012.
Sieradzki R., Cherniak Iu., Krankowski A. Near–real time monitoring of the TEC fluctuations over the northern hemisphere using GNSS permanent networks, Advances in Space
Research, 52(3):391–402. 2012. DOI:10.1016/j.asr.2013.03.036.
Zakharenkova I. E., Krankowski A., Shagimuratov I. I., Cherniak Yu. V., Krypiak–Grego
rczyk A., Wielgosz P., Lagovsky A. F. Observation of the ionospheric storm of October
11, 2008 using FORMOSAT–3/COSMIC data, Earth, Planets and Space, 64(6):505–512.
2012. DOI:10.5047/eps.2011.05.019.
Zakharenkova I., Krankowski A., Bilitza D., Cherniak Yu., Shagimuratov I. I., Sieradzki
R. Comparative study of foF2 measurements with IRI–2007 model predictions duringextended solar minimum, Advances in Space Research, 51(4):620–629. 2013.
DOI:10.1016/j.asr.2011.11.015.
Zakharenkova I., Cherniak Iu., Krankowski A., Shagimuratov I. Analysis of electron content variations over Japan during solar minimum: observations and modeling, Advancesin Space Research, 52(10):1827–1836. 2013. DOI:10.1016/j.asr.2012.09.043.
Zakharenkova I., Cherniak Iu., Krankowski A., Shagimuratov I. I. Cross–hemisphere comparison of mid–latitude ionospheric variability during 1996–2009: Juliusruh vs. Hobart,
Advances in Space Research, 53(2):175–189. 2013. DOI:10.1016/j.asr.2013.10.027.

7 Plan for activities in 2014:
The following actions to be considered:• Higher temporal resolution of IGS GIMs – 1 hour and less, combination conductedby UWM to be started as official/routine product.
• Predicted IGS GIMs – 1 and 2 days ahead, combination conducted by UWM to be
started as official/routine product.

151

IONOSPHERE WG• Starting a new official/operational product – TEC fluctuation changes over North
Pole to study the dynamic of oval irregularities (carried out by UWM to be started
as official/routine product after performance evaluation period.
• The new the IAAC from GNSS Research Center (GRC), Wuhan University, China.
• Cooperation with IRI COSPAR group

Future improvements are determined by users’ requirements (number of users has significantly increased during the last 15 years).

152

Multi–GNSS Working GroupO. Montenbruck
DLR, German Space Operations Center
Oberpfaffenhofen, 82234 Wessling, Germany
E–mail: oliver.montenbruck@dlr.de

1 Introduction
The Multi–GNSS Working Group (MGWG) has been established by the IGS to build up
experience in the use of new satellite navigation systems and modernized signals. As partof this task, the MGWG coordinates the performance of the Multi–GNSS Experiment(MGEX) which comprises the build–up of a new network of sensor stations, the characterization of the user equipment and space segment, the development of new concepts
and data processing tools, and, finally, the generation of early data products (Rizos et al.
(2013), Montenbruck et al. (2013b), (2013d)). MGEX is considered as a preparatory stepfor a future multi–GNSS pilot service that will integrate the new constellations into theestablished IGS product and service portfolio. A list of current MGWG members andtheir respective contributions is given in Tab. 1.

2 Network
Since the beginning of 2013, the MGEX network has grown substantially and now includes
roughly 90 stations (Dec. 2013; Fig. 1). A large number of new stations have been madeavailable by DLR (CONGO) and ESA. In addition, CNES has added multiple new stationsof their REGINA network that are of particular value in view of their remote location. The
network now provides good global coverage for Galileo tracking. QZSS and regional+global
BeiDou tracking is also supported, but more stations tracking these systems are still
desired to improve tracking coverage and geometry. Incorporation of Australia/Pacifica
stations from Geoscience Australia is presently delayed due to lacking manpower andpending technical constraints (RINEX generation, compatibility of R/T formats with BKG
infrastructure). Further efforts will also be required to acquire new stations supporting
the Indian Regional Navigation Satellite System (IRNSS).

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MULTI–GNSS WG

Table 1: Multi–GNSS Working Group members and task areas (status Dec. 2013)
Name

Institution

Task areas

Rolf DachJan Dousa
Ahmed El–Mowafy
Heinz Habrich
Satoshi Kogure
Richard Langley
Huiciu (Yolanda) Liu
Hans v.d. Marel
Oliver Montenbruck

AIUB
GOPE
CUT
BKG
JAXA
UNB
BACC
TUD
DLR/GSOC

Felix Perosanz
Chris Rizos
Tim Springer
Rene Warnant
Peter Steigenberger
Maik Uhlemann

CNES
UNSW
ESOC
ULG
TUM/IAPG
GFZ

Orbit and clock products, SP3 format extension (SP3d)
Quality control
Quality control
Data archives
Orbit and clock products, QZSS mission interface
Public outreach, GNSS constellation monitoring
Quality control
System characterization
Chair MGWG, MGEX coordination, network,
DCB product,data and product analysis(BeiDou, Galileo, QZSS, IRNSS)
Orbit and clock products
External representation (ICG, IGMA,...)
Data processing strategies
Ionosphere
Orbit and clock products, broadcast ephemeris product
Orbit and clock products

MGEX Offline Network (14 Sep 2013, 88 Stations)

GAL
BDS
QZSS

Figure 1: Distribution of MGEX stations supporting tracking of QZSS (blue), Galileo (red), andBeiDou (yellow) as of Dec. 2013.

154

3 Products
The MGEX network offers a large fraction of real–time stations and is thus well prepared
to incorporate new constellations into real–time precise–point–positioning services. Real–
time data streams from all supporting stations are publicly made available at the MGEX
caster hosted by BKG (http://mgex.igs-ip.net/). For ease of use, the vendor–specificdata formats received from individual stations are translated into the new RTCM 3.2
format (RTCM 2013), which offers a standardized framework for real–time transfer ofmulti–GNSS observation and ephemeris data and enables a consistent conversion to offline
RINEX data.
While MGEX collects a huge amount of data, numerous problems (e.g. suspicious/wrong
observation types, inconsistent RINEX file headers, wrong PRNs, bad data, inconsistent/wrong broadcast ephemeris parameters) exist, which affect the practical use of thosedata. No systematic data screening and quality control (QC) has been performed so far
and no dedicated infrastructure is available. To cope with this issue a “quality control task
force” has been established within the MGWG in late 2013. It will review QC tools (Anubis, BQC, BNC) and concepts independently developed at GOPE (Vaclavovic and Dousa
2013a), (2013b)), BACC, BKG and CUT (El-Mowafy (2013a), (2013b)) with the final goalof setting up a QC environment for the MGEX network and performing systematic QC ofpast and new MGEX observation data.

3 Products
Precise orbit and clock products of new GNSSs are contributed by various MGEX analysis
centers including AIUB, CNES/CLS, GFZ, JAXA, TUM, and, most recently, ESA. Whilesome of these products are only available for limited test periods, products for Galileo
and QZSS are routinely provided by at least two MGEX analysis centers. The cross–comparison and satellite laser ranging validation indicate a very encouraging performance(with accuracies at the few decimeter level) but provides evidence of systematic errors(Hackel et al. (2013), Montenbruck et al. (2013d), (2013e), Prange et al. (2013a), (2013b),(2013c); Steigenberger et al. (2013b), (2013c)) that are most likely related to solar radiationpressure modeling issues. In case of Galileo, initial performance improvements have been
demonstrated through use of a box–wing solar radiation model, but further research will be
required to approach the accuracy level currently achieved for GPS and GLONASS. Also,
efforts need to be made to properly consider the constellation–specific attitude modes incommon GNSS orbit determination software packages.
So far, no BeiDou precise orbit and clock products are made available by any IGS or non–
IGS institution but a combined multi–GNSS broadcast ephemeris is offered as part of the
MGEX project. While limited in accuracy, this product can still be used for a wide rangeof basic applications and serves as a substitute until precise products will be contributed
for all GNSSs.

155

MULTI–GNSS WG

YS

ON

YS

ON

Figure 2: Satellite laser ranging residuals of Galileo–IOV (top) and QZSS (bottom) orbit products (Montenbruck et al. 2013e). Notable variations of the orbit quality with theSun–angle above the orbital plane (β–angle) can be recognized for both systems. For
QZSS, differences between orbit normal mode (ON) and yaw–steering mode (YS) can,furthermore, be noted.

4 Biases
GNSS observations are affected by group and phase delays in the space and user segments,
which need to be properly characterized to fully exploit their inherent precision. In thecontext of modernized and emerging navigation systems the multiplicity of signals causes
a major challenge for a consistent processing of GNSS observations (Montenbruck andHauschild 2013). Various efforts have therefore been made to characterize inter–signal,
inter–frequency and inter–system biases within the MGEX project(Odijk and Teunissen(2013a), (2013b), Montenbruck et al. (2014), Springer et al. (2013)). The routine generation of a GPS, Galileo and BeiDou product for differential code biases (DCBs) is foreseen
for early 2014.
By way of example, Fig. 3 illustrates differential code biases of the Galileo–IOV satellites
for E1 and E5a signals as derived from MGEX observations and compares those to values
obtained by the Galileo control segment.

5 GNSS Evolution
Within the MGEX context, a variety of individual system studies have been performed
for characterization of new navigation systems such as BeiDou (Montenbruck and Steigenberger 2013), Montenbruck et al. (2013a)) and IRNSS (Langley et al. (2013), Thoelert et al.
(2013)). Satellite launches and constellation changes have routinely been monitored andcompiled(Langley (2013a), (2013b), (2013c), Montenbruck and Langley (2013)).

156

5 GNSS Evolution

10.00
8.00

Galileo DCB(E1-E5a) [ns]

6.00
4.00
2.00
0.00
-2.00
-4.00
-6.00
-8.00
-10.00
Jan 01
2013
10.00

E101(E11)
E101(E11)
Jan 31E102(E12)
E102(E12)
Mrz 02

Apr 01E103(E19)
E103(E19)

E104(E20)
E104(E20)

Mai 01

Mai 31E103(E19)

E104(E20)

Jun 308.00

Galileo DCB(E1-E5a) [ns]

6.00
4.00
2.00
0.00
-2.00
-4.00
-6.00
-8.00
-10.00
Jan 01
2013

E101(E11)

Jan 31E102(E12)

Mrz 02

Apr 01

Mai 01

Mai 31

Jun 30Figure 3: Galileo E1–E5a differential code biases of Galileo IOV satellites (top) for pilot–only
tracking (solid squares), and combined pilot–data tracking (open diamonds) as compared to DCBs from BGDE5aE1 Broadcast Group Delay parameters transmitted in the
Galileo navigation message (bottom) for the first half of 2013 (from Montenbruck et al.
(2014)).

157

Radial [m]4
3 G05 G07 G12 G15 G17 G29 G31 G01 G25 G24 G27
2
1
0
-1
-2
-3
2013
-4

Along-track [m]

4
3
2
1
0
-1
-2
-3
2013
-4

Cross-track [m]MULTI–GNSS WG

4
3
2
1
0
-1
-2
-3
2013
-4

15.Jun15.Jun15.Jun

17.

19.

21.

0.03+/-0.15m

23.

25.

27.

29.

-0.45+/-0.87m

17.

19.

21.

23.

25.

27.

29.

-0.01+/-0.47m

17.

19.

21.

23.

25.

27.

29.

Figure 4: Accuracy of GPS CNAV broadcast ephemeris data transmitted during the June 2013
test campaign relative to IGS precise orbit products.

In June 2013 the first GPS CNAV test campaign has been supported by the Multi–GNSS
Working Group (Montenbruck et al. 2013c). Test data have been collected with a selected
set of global DLR and UNB stations. The data were decoded, analyzed and made publicly
available through CDDIS for interested users. CNAV includes novel information such as
Earth orientation parameters and inter–signal group delay corrections. The comparison
with precise IGS orbits (Fig. 4) furthermore exhibits an improved smoothness and reduced
discontinuities of CNAV broadcast orbits, even though the overall accuracy is presently
still similar to that of the legacy navigation message (LNAV).

6 Standardization
The Multi–GNSS WG has contributed to further evolve the RINEX3 and RTCM3 standards for multi–GNSS use and to extend the SP3 format (version “SP3d” proposal for >85
satellites) in close interaction with other IGS working groups.

158

7 Public Outreach

7 Public Outreach
The MGEX website (http://igs.org/mgex) continues to serve as a primary portal for
MGEX related information and access to the MGEX data repository. During the reporting
period regular updates have been performed in an effort to provide up-to–date information
on GNSS constellations as well as MGEX data and products. In view of access restrictions
for Chinese users, a mirror site (http://igsws.unavco.org/mgex/) has been implemented
by UNAVCO.
Achievements of the MGEX project have been advertised in various overview papers andmagazine articles (Rizos et al. (2013), Montenbruck et al. (2013b),(2013d)) as well as
numerous conference and workshop presentations (including CSNC, Wuhan; EGU, Vienna; ENC, Vienna: EUREF Symp. Budapest; HxGN LIVE Conf., Las Vegas; Joint
Int. Symp. on Deformation Monitoring, Nottingham; National GPS/GNSS Symposium,
Tokyo; Int. Symp. on GNSS Istanbul; SBAS Iono Meeting, Bath) given by individual
members of the Multi–GNSS Working Group.

159

MULTI–GNSS WG

Acronyms and Abbreviations
AIUB
BACC
BKG
CLS
CNES
CONGO
CUT
DLR
ESA
ESOC
GFZ
GOPE
IAPG
JAXA
MGM–netREGINA
RTCM
TUD
TUM
ULG
UNB
UNSW

Astronomisches Institut der Unversität Bern
Beijing Aerospace Control Center
Bundesamt für Kartographie und Geodäsie
Collecte Localisation Satellites
Centre National d’Etudes Spatiales
Cooperative Network for GNSS Observation
Curtun University of Technology
Deutsches Zentrum für Luft– und Raumfahrt
European Space Agency
European Sapce Operations Center
Deutsches GeoForschungsZentrum
Geodetic Observatory Pecný
Institute of Astronomical and Physical Geodesy
Japan Aerospace Exploration Agency
Multi–GNSS Monitoring Network
REseau GNSS pour l’IGS et la Navigation
Radio Technical Commission for Maritime Services
TU Delft
Technische Universität München
Université de Liège
University of New Brunswick
Univesity of New South Wales

References
El-Mowafy, A. Real–Time Validation of BeiDou Observations in a Stand–alone Mode.
Proceedings of the ION 2013 Pacific PNT Meeting, Honolulu, Hawaii, Apr. 2013,
pp. 106–114, 2013a.
El-Mowafy, A. GNSS Multi–frequency Receiver Single–Satellite Measurement Validation
Method. GPS Solutions, 2013b. doi: 10.1007/s10291-013-0352-6.
Hackel, S., P. Steigenberger, U. Hugentobler, M. Uhlemann, and O. Montenbruck. Galileo
Orbit Determination using Combined GNSS and SLR Observations. accepted for:GPS Solutions, 2013.
Hauschild, A., O. Montenbruck, and P. Steigenberger. Short–Term Analysis of GNSS
Clocks. GPS Solutions, 17(3):295–307, 2013. doi: 10.1007/s10291-012-0278-4.
Hugentobler, U., C.J. Rodriguez-Solano, and P. Steigenberger. Stable Satellite Clocks for
Orbit Model Validation. 4th Int. Colloquium on Scientific and Fundamental Aspectsof the Galileo System, Dec. 2013, Prague, 2013.

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Langley, R.B. Russian SBAS Luch–5B in Orbital Slot. GPS World, 24(1):27, 2013a.
Langley,
R.B.
IndianRegional
Navigation
Satellite
StartsSignalTransmissions.
GPS World
website.
http://www.gpsworld.com/
indian-regional-gnss-satellite-starts-signal-transmissions/,
posted25 Jul. 2013b.
Langley, R. B. The Almanac. GPS World, 24(8):47–50, 2013c.
Langley, R. B., S. Thoelert, and M. Meurer. IRNSS Signal Close–up. GPS World, 24(9):18, 2013.
Montenbruck, O. and R. B. Langley. Galileo IOV–3 Broadcasts E1, E5, E6 Signals. GPS
World, 24(1):18+27, 2013.
Montenbruck, O. and A. Hauschild. Code Biases in Multi–GNSS Point Positioning. ION
International Technical Meeting 2013, 28–30, Jan. 2013, San Diego, 2013.
Montenbruck, O. and P. Steigenberger. The BeiDou Navigation Message. IGNSS Symposium 2013, 16–18 Jul., Outrigger Gold Coast, Qld, Australia, 2013.
Montenbruck, O., A. Hauschild, and P. Steigenberger. Differential Code Bias Estimation using Multi–GNSS Observations and Global Ionosphere Map. ION International
Technical Meeting, 26–28 Jan. 2014, San Diego., 2014.
Montenbruck, O., A. Hauschild, P. Steigenberger, U. Hugentobler, P. Teunissen, and
S. Nakamura. Initial Assessment of the COMPASS/BeiDou–2 Regional Navigation Satellite System. GPS Solutions, 17(2):211–222, 2013a. doi: 10.1007/
s10291-012-0272-x
Montenbruck, O., Ch. Rizos, R. Weber, G. Weber, R. Neilan, and U. Hugentobler. Gettinga Grip on Multi–GNSS: The International GNSS Service MGEX Campaign. GPS
World, 24(7):44–49, 2013b.
Montenbruck, O., R. B. Langley, and P. Steigenberger. First Live Broadcast of GPS CNAV
Messages. GPS World, 24(8):14–15, 2013c.
Montenbruck, O., P. Steigenberger, R. Khachikyan, G. Weber, R. B. Langley, L. Mervart,and U. Hugentobler. IGS–MGEX: Preparing the Ground for Multi–Constellation
GNSS Science. 4th Int. Colloquium on Scientific and Fundamental Aspects of theGalileo System 4–6 Dec. 2013, Prague, 2013d.
Montenbruck, O., P. Steigenberger, and G. Kirchner. GNSS Satellite Orbit Validation
Using Satellite Laser Ranging. 18th International Workshop on Laser Ranging, 11–15
Nov. 2013, Fujiyoshida, Japan, 2013e.

161

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Odijk, D. and P. Teunissen. Characterization of between–receiver GPS–Galileo inter–system biases and their effect on mixed ambiguity resolution. GPS Solutions, 17(4):521–533, 2013a.
Odijk, D. and P. J. G. Teunissen. Estimation of Differential Inter–System Biases between
the Overlapping Frequencies of GPS, Galileo, BeiDou and QZSS. 4th Int. Colloquium
on Scientific and Fundamental Aspects of the Galileo System, 4–6 Dec. 2013, Prague,
2013b.
Prange, L., S. Lutz, R. Dach, S. Schaer, and A, Jäggi. A MGEX data analysis at CODE
– current status. EGU General Assembly 2013, April 7–12, 2013, Vienna, Austria,
2013a.
Prange, L., R. Dach, S. Schaer, S. Lutz, and A, Jäggi. Experiences with IGS MGEX data
analysis at CODE. EUREF Symposium 2013, May 29–31, 2013, Budapest, Hungary,
2013b.
Prange, L., R. Dach, S. Lutz, S. Schaer, and A, Jäggi. The CODE MGEX orbit and clock
solution. IAG Scientific Assembly 2013, IAG Scientific Assembly 2013, Sep. 1–6, 2013,
Potsdam, Germany, 2013c.
Rizos, C., O. Montenbruck, R. Weber, G. Weber, R. Neilan, and U. Hugentobler. The IGS
MGEX Experiment as a Milestone for a Comprehensive Multi–GNSS Service. ION
Pacific PNT Meeting 2013, 22–25 April 2013, Honolulu, 2013.
RTCM. RTCM Standard 10403.2. Differential GNSS (Global Navigation Satellite Systems)
Services– Version 3 with Ammendment 1., RTCM, Arlington, VA, 12 Jul. 2013.
Springer, T., E. Schönemann, F. Dilssner, L. Agrotis, W. Enderle. GNSS Analysis in a
Multi–GNSS and Multi–Signal Environment. AGU Fall Meeting, 9–13 Dec. 2013, San
Francisco, USA, 2013.
Steigenberger, P., U. Hugentobler, A. Hauschild, and O. Montenbruck. Orbit and Clock
Analysis of Compass GEO and IGSO Satellites. Journal of Geodesy, 87(6):515–526,
2013a. doi: 10.1007/s00190-013-0625-4
Steigenberger, P., S. Hackel, U. Hugentobler, and O. Montenbruck. One year of Galileo
IOV orbit and clock determination. EGU General Assembly 2013, Vienna, 7–12
Apr. 2013b.
Steigenberger, P., U. Hugentobler, L. Prange, R. Dach, M. Uhlemann, G. Gendt, S. Loyer,
F. Perosanz, and O. Montenbruck. Quality assessment of Galileo Orbit and Clock
Products of the IGS Multi–GNSS Experiment (MGEX); G51B-01. AGU Fall Meeting,
9–13 Dec. 2013, San Francisco, USA, 2013c.
Thoelert, S., O. Montenbruck, and M. Meurer. IRNSS–1A – Signal and Clock Characterization of the Indian Regional Navigation System. GPS Solutions, 2013. doi:
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Vaclavovic, P. and J. Dousa. G–Nut/Anubis – open–source tool for multi–GNSS data
monitoring. IAG General Assembly, 2–6 Sep. 2013, Potsdam, 2013a.
Vaclavovic, P. and J. Dousa. Anubis – A tool for Quality Checl of Multi–GNSS Observation
and Navigation Data. 4th Int. Colloquium on Scientific and Fundamental Aspects of
the Galileo System, 4–6 Dec. 2013, Prague, 2013b.

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164

IGS Reference Frame Working Group
Coordinator Report 2013
P. Rebischung1 , B. Garayt2 , X. Collilieux1 , and Z. Altamimi1
1

2

IGN LAREG, Univ Paris Diderot, Sorbonne Paris Cité
5 rue Thomas Mann, 75205 Paris Cedex 13, France
E–mail: paul.rebischung@ign.fr
IGN SGN

1 Introduction
The Reference Frame Working Group (RFWG) activities were not marked by any major
event in 2013. The two next sections will therefore simply give a brief overview of the recent
IGS SINEX combination results and review the current status of the IGb08 Reference
Frame. Section 4 finally summarizes the RFWG recommendations to the IGS Analysis
Centers in view of the 2nd IGS reprocessing campaign.

2 Recent IGS SINEX combination results
Fig. 1 shows the RMS of the Analysis Center (AC) station position residuals from thedaily IGS SINEX combinations of year 2013, i.e. the global level of agreement between
the AC and IGS combined station positions once reference frame differences have been
removed. Except for SIO, which has been excluded from the IGS combinations since GPS
week 1709, the AC station position residuals have remained at fairly stable levels over2013. The overall agreement between the daily terrestrial frames of the leading ACs is
now at the level of 1 mm for horizontal station positions and 3 mm for station heights. A
comparative study of the AC station position time series since the switch to daily SINEX
integrations (Ray et al. 2013) nevertheless revealed several short–period AC–dependentfeatures.

165

REFERENCE FRAME WG
4 mm

East

2 mm

4 mm

North

2 mm

0 mm

0 mm
1730

1740

1750

1760

8 mm

1770

1730

1740

1750

1760

1770

Up

4 mm

cod

gfz

mit

emr

grg

ngs

esa

jpl

sio

0 mm
1730

1740

1750

1760

1770

GPS week

Figure 1: RMS of AC station position residuals from the 2013 daily IGS SINEX combinations.
All time series were low–pass filtered with a 10 cycles per year cut–off frequency.

Fig. 2 and 3 show the AC Earth Orientation Parameter (EOP) residuals from the IGS
SINEX combinations of year 2013. With a few noticeable exceptions (NGS for pole coordinates; MIT for the Length of Day – LOD), the AC EOP residuals show rather homogeneoushigh–frequency scatters. Several problematic features can however be noticed in specific
AC EOP estimates:• Because of unexpectedly small formal errors, the MIT LOD estimates have overwhelmed the IGS combined LODs since GPS week 1726. The disproportion of the
MIT LOD formal errors remains unexplained yet.
• Pronounced sub–seasonal and abrupt variations can be noticed in the COD X–
pole and Y–pole rate estimates. There are indications that these excursions, aswell as smaller features in the ESA and GFZ Y–pole rate estimates, are caused by
GLONASS orbit modeling problems (T. Springer, personal communication).
• Comparable excursions are visible in the EMR X–pole and pole rate estimates,
but remain unexplained. (EMR does not make use of GLONASS data.) Due toespecially large offsets, the EMR pole rate estimates were thus rejected from the
IGS combinations of weeks 1760–1762.

3 Status of the IGb08 Reference Frame
Fig. 4 illustrates the progressive decay of the IGS08/IGb08 Reference Frames (RF) since
the adoption of IGS08 on GPS week 1632 (April 17, 2011; IGSMAIL #6354). The abrupt

166

3 Status of the IGb08 Reference Frame
xp residuals (mas)yp residuals (mas)

0.1

0.1

0.0

0.0

−0.1

−0.1

cod

0.1

0.1

0.0

0.0

−0.1

−0.1

emr

0.1

0.1

0.0

0.0

−0.1

−0.1

esa

0.1

0.1

0.0

0.0

−0.1

−0.1

gfz

0.1

emr

esa

gfz

0.1

0.0

0.0

−0.1

−0.1

grg

0.1

grg

0.1

0.0

0.0

−0.1

−0.1

jpl

0.1

jpl

0.1

0.0

0.0

−0.1

−0.1

mit

0.1

mit

0.1

0.0

0.0

−0.1

−0.1

ngs

0.1

0.1

0.0

0.0

−0.1

cod

−0.1

sio
1730 1740 1750 1760 1770

GPS weekngs

sio
1730 1740 1750 1760 1770

GPS week

Figure 2: AC pole coordinate residuals from the 2013 daily IGS SINEX combinations.

167

REFERENCE FRAME WG

xp rate residuals (mas/d)

yp rate residuals (mas/d)

0.5

0.5

0.0

0.0

−0.5

−0.5

cod

LOD residuals (ms)
0.05
0.00
−0.05

cod

0.5

0.5

0.0

0.0

0.00

−0.5

−0.5

−0.05

emr

0.05

emr

0.5

0.5

0.0

0.0

0.00

−0.5

−0.5

−0.05

esa

esa

0.5

0.05

0.0

0.0

0.00

−0.5

gfz

0.5

−0.05

gfz

0.0

−0.5

−0.5

grg

0.5

0.5

0.0

0.0

gfz

−0.5

jpl

grg
0.05
0.00
−0.05

jpl

0.5

0.5

0.0

0.0

0.00

−0.5

−0.5

−0.05

mit

0.5

0.5

0.0

0.0

−0.5

esa

0.5

0.0

−0.5

emr

0.05

0.5

−0.5

cod

−0.5

ngs

0.05

mit

0.00
−0.05

ngs

0.5

0.0

0.0

0.00

−0.5

−0.5

−0.05

1730 1740 1750 1760 1770

GPS week

mit

0.05

0.5

sio

jpl

ngs

0.05

sio
1730 1740 1750 1760 1770

GPS weeksio1730 1740 1750 1760 1770

GPS week

Figure 3: AC pole rate and LOD residuals from the 2013 daily IGS SINEX combinations.

168

3 Status of the IGb08 Reference Frame# RF stations# RF core stations
70

150
60
120

50
1650

1700

GPS week

1750

1650

1700

1750

GPS week

Figure 4: Numbers of usable RF stations and RF core stations in recent weekly/daily IGS combined SINEX solutions.

increase visible in Fig. 4 corresponds to the adoption of IGb08 on GPS week 1709 (October
7, 2012; IGSMAIL #6663). Since then, the overall number of usable RF stations has
started decreasing again at a rather constant rate. In 2013, nine IGb08 stations thus
became unusable as RF stations because of position discontinuities, seven of them due
to equipment changes. Eleven other IGb08 stations were decommissioned or stopped
transmitting data.
On the other hand, the number of RF core stations used to align the IGS daily combined
solutions to IGb08 has fairly constantly remained around 65 during 2013. As illustrated
in Fig. 5, the distribution of the usable IGb08 core stations was still rather satisfactory at
the end of 2013, except two inevitable holes in South America/South Atlantic and Eastern
Asia/North Pacific.

Figure 5: Distribution of the 64 IGb08 core stations used to align the IGS combined solutionof December 31, 2013 (green dots). The small black dots correspond to the 27 otherunusable IGb08 core stations.

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REFERENCE FRAME WG

10 mm

East
North

5 mm

Up
0 mm
1996

1998

2000

2002

2004

2006

2008

2010

2012

2014

Figure 6: RMS of the residuals from 7–parameter similarity transformations between theweekly/daily IGS combined solutions and the IGS08/IGb08 Reference Frames. The igb
weekly solutions (IGSMAIL #6401) were used for the period before GPS week 1632.
The operational IGS combined solutions were used afterwards.

Fig. 6 finally illustrates another aspect of the progressive ageing of the IGS08/IGb08
Reference Frames. Since the latest IGS data inputs into ITRF2008 (2009.5), the accuracyof the IGS08/IGb08 reference station coordinates has indeed steadily degraded becauseof growing station velocity propagation errors. The global level of agreement between
the IGS daily combined solutions and IGb08 is now at the level of 4 mm for horizontal
station positions and 10 mm for station heights, about twice as in 2009. This growing
disagreement is a concern for the accuracy and stability of the Reference Frame realized
by the IGS products and will get worse until a new Reference Frame based on the future
ITRF2013 is adopted.

4 Preparation of the 2nd IGS reprocessing campaign
One of the main motivations for the 2nd IGS reprocessing campaign (repro2) is to provide
the IGS contribution to the next ITRF realization (ITRF2013). To make this contribution
as strong and useful as possible, a set of recommended GNSS stations has been provided
to the IGS ACs participating to repro2 (IGS–ACS–MAIL #849) along with several station
selection guidelines reminded hereafter:• Process all available IGb08 core stations to ensure a minimal common base between
AC solutions in view of their combination.
• Avoid “jumping networks”, i.e. radically different station selections from one day to
the next.
• To the extent possible, include:– all available IGb08 stations;– all GNSS stations co–located with other techniques, including the co–locatedstations in ITRF2008 as well as some new or improved DORIS, SLR and VLBI

170

References
co–locations;– the NGA stations, provided the availability of new data corrected for half–cycle
phase offsets;– specific stations selected in view of strengthening the next IGS Reference Framein the South America, Pacific and Africa areas.
• Consider the inclusion of TIGA stations.
Several recommended non–IGS stations are already in the process of becoming part of the
IGS network. Others have been submitted to the IGS Central Bureau in cooperation withthe station operators.

References
Ray, J., J. Griffiths, X. Collilieux, and P. Rebischung. Subseasonal GNSS positioning errors. Geophysical Research Letters, 40(22):5854–5860, 2013. doi: 10.1002/
2013GL058160

171

REFERENCE FRAME WG

172

RINEX Working Group Report 2013
Ken MacLeod1 , Loukis Agrotis2 , and Rolf Dach3
1
2
3

Natural Resources Canada
European Space Operations Centre
Astronomical Institute, University of Bern

1 Introduction
The RINEX Working Group (RWG) was formed as a partnership between the IGS andthe Radio Technical Commission for Maritime Services, Special Committee 104 (RTCM–
SC104). Currently the working group consists of about 50 members with the numbers
equally split between the two groups. Within the IGS, the RWG performs two roles: oneis the development and documentation of the RINEX data format and the other is towork within the RTCM to develop messages and protocols that meet the needs of the IGS
community.

2 Activities in 2013
In January of 2013, after several years of discussion and message content refinement,
RTCM–SC104 approved the RTCM Multiple Signal Message (RTCM–MSM) binary format. The first release only supported: GPS, GLONASS and Galileo. However, QZSSand BeiDou support was added later in the year. The RTCM–MSM binary observation
message format is fully interoperable with RINEX 3.02. Both RTCM–MSM and RINEX
3.02 use the same signal naming and phase alignment protocols. Further, all RTCM–MSM
high precision observations types: pseudorange, phase, doppler, carrier to noise ratio andloss of lock, meet RINEX 3.0x measurement and protocol standards. The developmentof the RTCM–MSM format will enable GNSS users to either process binary data directly(file or internet stream) or convert the MSM binary format into RINEX 3.0x (without aloss of information). Lastly, at the May RTCM meeting the Galileo ephemeris message
was approved.
In April of 2013 RINEX 3.02 was jointly released by the IGS/RTCM RINEX working
group. RINEX 3.02 supports the following constellations: GPS, GLONASS, Galileo,

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RINEX WG
QZSS, BeiDou and SBAS. As mentioned above RINEX 3.02 and RTCM–MSM observations both specify the same signal definition and phase alignment protocol. This level ofintegration and interoperability between RINEX and RTCM–MSM will make it easier touse both formats. Another new feature introduced in RINEX 3.02 is the specification ofa new more descriptive file naming convention.
Summary of the RINEX working group’s tasks completed in 2013:• RTCM–MSM phase aligned binary observation format approved by the RTCM–
SC104 (Jan. 2014)– RTCM–MSM currently supports GPS, GLONASS, Galileo, QZSS and BeiDou• Released RINEX 3.02 in April of 2013. RINEX 3.02 supports the following GNSS
constellations: GPS, GLONASS, Galileo, QZSS, BeiDou and SBAS.
• RTCM Galileo Ephemeris approved by RTCM.

• RINEX 3.02 is supported by GNSS equipment vendors and IGS partners (BKG’s,
BNC software). IGS analysis center support for RINEX 3.02 has started.
• The development of RINEX 3.02 Quality Control (QC) tools has begun. Some basic
QC tools (multipath, cycle slip and percentage good data) are currently available.
• RINEX 3.02 interoperability testing is ongoing within the IGS MGEX project.

• In mid–November it was observed that some RINEX 3.02 providers were using theold RINEX 3.01 BeiDou B1 frequency codes. This inconsistency is currently being
resolved within the MGEX project.
• Attended RTCM Meetings: January, 2013 (San Diego, CA), May, 2013 (Nante,
France) (Loukis Agrotis) and September, 2013 (Nashville, TN)

3 Plan for 2014
During the 2014 calendar year the RINEX Working Group will focus its efforts on thefollowing tasks:• Update the RINEX 2.11 and 3.0X documentation to provide a clear and concise
description of the standard to meet the needs of the GNSS community.
• Release a RINEX 3.02 update annually or as required.

• Support IGS partner and GNSS vendor adoption of RINEX 3.02.
• Further develop RINEX 3.02 QC tools.

• Work with both IGS and RTCM partners to test interoperability between RINEX
174

3 Plan for 20143.02 files created by different applications. Verify that RINEX 3.02 files are compliant with the standard i.e. contain mandatory records, properly defined records,
correct codes and phase aligned observations.
• IGS RINEX 3.02 testing and development will be done as part of the IGS MGEX
project.
• Planned additions to RINEX 3.0X include GPS CNAV ephemeris.
Within the RTCM–SC104 the RWG will contribute to the development of the following
binary messages that would enable the creation of a complete RINEX file from either a
GNSS receiver stream or an RTCM–MSM file:• Station description (RINEX header information)• Receiver description information such as: serial, model and firmware number andalso state information such as: CPU load; internal temperature; number of satellite
vehicles tracked and a station change control mechanism called: Issue of Data Station(IODS).
• Antenna Description: serial and model number and IODS.
• Meteorological Sensor Description and IODS.
• Meteorological Observations and IODS.

• The IODS is designed to notify both real–time and file based users that a station’s
equipment or software/firmware has changed and that the change may affect theusability of the observation data.
Other RTCM Messages:• Extend RTCM–State Space Representation (RTCM–SSR), satellite orbit and clock
correction messages to support Galileo, QZSS and BeiDou.
– Develop RTCM–SSR messages to support atmospheric and ionospheric correction messages (both station and network types).
• Develop ephemeris messages to support QZSS, BeiDou and GPS(CNAV).

• Develop a position report message that contains position and accuracy (variance/covariance)
information.

175

RINEX WG

176

The IGS Tide Gauge Benchmark Monitoring
Working Group
T. Schöne, R. Bingley, Z. Deng, J. Griffiths, H. Habrich,A. Hunegnaw, M. Jia, M. King, M. Merrifield, G. Mitchum,R. Neilan, C. Noll, E. Prouteau, L. Sánchez, N. Teferle,
D. Thaller, P. Tregoning, G. Wöppelmann, and P. Woodworth

1 Introduction
In support of climate and sea level related studies and organizations concerned herewith,
the Tide Gauge Benchmark Monitoring Working Group (TIGA–WG) of the IGS provides
vertical geocentric positions, vertical motion and displacements of GNSS stations at ornear tide gauges. To a large extend the TIGA–WG uses the infrastructure and expertiseof the IGS.
The main aims of the TIGA Working Group are:
• Maintain a global virtual continuous GNSS @ TG network• Compute precise coordinates and velocities of GNSS stations at or near tide gauges
with a significant delay to allow as many as possible stations to participate. Provide
a combined solution as the TIGA official product.
• Study the impacts of corrections and new models on the GNSS processing of thevertical coordinate. Encourage other groups to establish complementary sensors to
improve the GNSS results, e.g., absolute gravity sites.
• Provide advice to new applications and installations.
For the year 2013, the TIGA–WG has continued to prepare the reprocessing of the TIGA
network, which is in parallel to the repro2 campaign of the IGS. Test sets of data (weekly
SINEX solutions) have been circulated between groups to ensure consistency in exchange
formats. Four groups are currently reprocessing TIGA and GNSS@TG data (e.g., Denget al. (2013), Hunegnaw et al. (2013)). Nearly 800 GNSS@TG stations and IGS08b coresites are processed. In peak times, e.g. GFZ (see Fig. 1) processes up to 794 stations, 580
of them near tide gauges. The numbers are similar for the other groups.

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TIGA WG

Figure 1: Number of GNSS@TG stations and number of satellites processed for the TIGA repro2
by GFZ Potsdam. At peak times nearly 800 GNSS stations are reprocessed.

Also significant progress has been made by the SONEL data center (http://www.sonel.
org), hosted by the University of La Rochelle. The SONEL portal allows users to accessmeta data information, download data, and view processing results. Frequent updates
and information exchange with TIGA Data Center hosted by NASA at CDDIS ensuresup–to–date information.
As an ongoing task, SONEL in cooperation with the TIGA–WG identifies potential new
TIGA stations and encourages and assists station manager to participate. In addition,
stations with data outages and/or significant data gaps are identified. Station operators
are contacted to get data access. The SONEL data center is recognized as the GNSS and
TIGA data center for UNESCO/GLOSS/IOC. The progress is documented by, e.g., thegrowing number of archived RINEX files.

2 Recent TIGA related publications
Burgette, R., C.S. Watson, J.A. Church, P. Tregoning, and R. Coleman. Characterizing
and minimizing the effects of noise in tide gauge time series: relative and geocentricsea level rise around Australia. Geophy. J. Int., 194(2):719–736, 2013.
King, M.A., M. Keshin, P.L. Whitehouse, I.D. Thomas, G.A. Milne, and R.E.M. Riva.
Regional biases in absolute sea level estimates from tide gauge data due to residual
unmodeled vertical land movement. Geophysical Research Letters, 39:, 2012. L14604
doi: 10.1029/2012GL052348.
Olivares, G. and F.N. Teferle. A Bayesian Monte Carlo Markov Chain Method for Param-178

eter Estimation of Fractional Differenced Gaussian Processes. IEEE Transactions on
Signal Processing, 61(9):2405–2412, 2013.
Rudenko, S., N. Schön, M. Uhlemann, G. Gendt. Reprocessed height time series for GPS
stations. Solid Earth, 4(1):23–41, 2013.
Sánchez, L.. Towards a vertical datum standardisation under the umbrella of Global
Geodetic Observing System. Journal of Geodetic Science, 2(4):325–342, 2013. doi:
10.2478/v10156-012-0002-x.
Santamaría–Gómez, A., M–N. Bouin, X. Collilieux, and G. Wöppelmann. Time–
Correlated GPS Noise Dependency on Data Time Period. International Associationof Geodesy Symposia, 138:119–124, 2013.
Santamaría–Gómez, A., M–N. Bouin, and G. Wöppelmann. Improved GPS data analysis
strategy for tide gauge benchmark monitoring. International Association of Geodesy
Symposia, 136:11–18, 2012.
Schöne, T., R. Bingley, Z. Deng, J. Griffiths, H. Habrich, A. Hunegnaw, ,M. Jia, M. King,
M. Merrifield, G. Mitchum, R. Neilan, C. Noll, E. Prouteau, L. Sánchez, N. Teferle,
D. Thaller, P. Tregoning, P. Woodworth, and G. Wöppelmann. The Tide Gauge
Benchmark Monitoring Project. In: Dach and Jean (eds.): Technical Report 2012, International GNSS Service, pp. 189–194, ftp://igs.org/pub/resource/pubs/2012_techreport.pdf, 2013.
Schöne, T.. GNSS at Tide Gauges, German Climate Observing Systems. Inventory reporton the Global Climate Observing System, (GCOS)Self–published by DWD, Offenbacha. M., 130 pages.
Deng, Z., G. Gendt., and T. Schöne. Status of the tide Gauge data reprocessing at GFZ.
International Association of Geodesy Scientific Assembly, 150th Anniversary of theIAG, Potsdam, 1.–6. Sep., 2013.
Hunegnaw, A., F.N. Teferle, R.M. Bingley, and D.N. Hansen. Status of Reprocessing andCombinations of TIGA Analysis Center Solutions at BLT. IAG Scientific Assembly
2013, IAG 150 Years, 1–6 September, Potsdam, Germany, 2013.

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TIGA WG

3 TIGA Working Group Members in 2013
Table 1: TIGA Working Group Members in 2013
Name

EntityHost Institution

Country

Guy Wöppelmann
Laura Sánchez
Heinz Habrich
Minghai Jia
Paul Tregoning
Zhiguo Deng
Daniela Thaller
Norman Teferle
Richard Bingley
Ruth Neilan
Jake Griffith
Carey Noll
Tilo Schöne
Philip Woodworth
Gary Mitchum
Mark Merrifield
Matt King

TAC, TNC, TDC
TAC
TAC

University La Rochelle
DGFI Munich
BGK, Frankfurt
GeoScienceAustralia
ANU
GFZ Potsdam
BGK, Frankfurt
University of Luxembourg
University of Nottingham
ex officio
ex officio
CDDIS, NASAGFZ Potsdam
PSMSL, Liverpool
University of South Florida
UHSLC, Hawaii
University of Tasmania

FranceGermany
Germany
Australia
Australia
Germany
Germany
Luxembourg
UK
USA
USA
USA
Germany
UK
USA
USA
Australia

180

TAC
TAC
Combination
TAC/CombinationTAC
IGS Central Bureau
IGS AC coordinator
TDC
Chair TIGA–WGPSMSLGLOSS GE (current chair)
GLOSS GE (past chair)

3 TIGA Working Group Members in 2013

Figure 2: The SONEL TIGA data center (University La Rochelle, France) provides an accesspoint for meta information (http://www.sonel.org). The GNSS data base is synchronized with the TIGA Data Center (TDC) at CDDIS (NASA, USA). In addition,
informations are exchanged and updated with the PSMSL (http://www.psmsl.org)
and GLOSS data centers (e.g., http://www.ioc-sealevelmonitoring.org).

Figure 3: Development of the number of RINEX files for GNSS@TG available trough the SONEL
data center.

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TIGA WG

182

IGS Troposphere Working Group 2013
C. Hackman and S. M. Byram
United States Naval Observatory
3450 Massachusetts Avenue Northwest
Washington DC 20392 USA
E-mail: christine.hackman@usno.navy.mil
Tel. +1–202–762–1428

1 Introduction
The IGS Troposphere Working Group (IGS TWG) was founded in 1998. The United States
Naval Observatory (USNO) assumed chairmanship of the WG as well as responsibility for
producing IGS Final Troposphere Estimates (IGS FTE) in 2011.
Dr. Christine Hackman chairs the IGS TWG. Dr. Sharyl Byram oversees production of the
IGS FTEs. Both are part of the GPS Analysis Division (GPSAD) in the Earth Orientation
Department at USNO. GPSAD also hosts the USNO IGS Analysis Center.
The IGS TWG comprises approximately 50 members (cf. Appendix A.). A revised charter
approved by the IGS Governing Board (GB) at the close of 2011 is shown in Appendix
B.

2 IGS Final Troposphere Product
Generation/Improvements/Usage 2013
USNO produces IGS Final Troposphere Estimates for the 350+ stations of the IGS network. Each 24–hr site result file provides five–minute–spaced estimates of total troposphere zenith path delay (ZPD), north, and east gradient components, with the gradient components used to compensate for tropospheric asymmetry. These files can be
downloaded from ftp://cddis.gsfc.nasa.gov/gps/products/troposphere/zpd; users
downloaded 10.3 million files in 2013 (Noll 2014).
IGS Final Troposphere estimates are generated via Bernese GPS Software 5.0 (Dach et al.
2007) using precise point positioning (PPP; Zumberge et al. (1997)) and the GMF mapping

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TROPOSPHERE WG
function (Boehm et al. 2006) with IGS Final satellite orbits/clocks and earth orientation
parameters (EOPs) as input. Each site–day’s results are completed approximately three
weeks after measurement collection as the requisite IGS Final orbit products become
available. Further processing details can be obtained from Byram and Hackman (2012).
USNO will use Bernese GNSS Software 5.2 (http://www.bernese.unibe.ch/features)to compute troposphere estimates for the IGS Reprocessing 2 effort (http://acc.igs.
org/reprocess2.html).
Several improvements in quality–control and number of stations processed were made in
2013. An error in implementing antenna–height changes was corrected with the affected
station–days reprocessed and re–archived (Hackman 2013). Detection of missing input
data and result outliers was strengthened; faster raw–data download and result uploadroutines were implemented as well. The average number of quality–checked station result
files submitted per day in 2013 thus improved 7% to 324 from its 2012 average value of
302. The authors thank Drs. James Perlt (Bundesamt fuer Kartographie & Geodaesie)
and Jan Dousa (Geodetic Observatory Pecny; GOP) for alerting them to quality–control
issues.

3 IGS Troposphere Working Group Activities 2013
3.a Automating comparisons of troposphere estimates obtained using
different measurement techniques
At the 2012 IGS Workshop (Olstzyn, Poland), the IGS TWG submitted the following
recommendation to the IGS Governing Board, which accepted it:“By the next [2014] IGS Workshop, establish automated, on–going comparison of IGS final troposphere estimates (FTEs) with results from other techniques/ACs with the goal of establishing the accuracy of IGS FTEs.”• Jan Dousa and his GOP colleagues developed a database performing the desired
comparisons between troposphere values obtained from different techniques such as
GPS, VLBI, radiosonde and numerical–weather models. This database is flexible
enough to handle additional data types as desired.
• Comparison of troposphere values from different techniques requires an understanding of the exact point in space to which a given estimate corresponds. Several suchpotential inter–technique reference–point discrepancies have been resolved.
• It was originally proposed (Byram and Hackman 2012) that corrections applied tonon–co–located troposphere estimates be performed using equations given in Tekeet al. (2011). Dousa and colleagues have developed further refinements (Gyori andDousa 2014) that will likely be used instead.

184

3 IGS Troposphere Working Group Activities 2013

3.b Other activities• A joint US–Czech grant proposal, “Automated Intra– and Inter–technique Troposphere Estimate Comparisons,” was made to the Kontact II Czech–US research partnership by GOP’s Jan Dousa with supporting documents authored by USNO/WG
chair Christine Hackman. The US Department of State is the executive agent.
• A variety of future initiatives were discussed at the 10 December 2013 working–groupmeeting: please see Section 3.c.2 below.

3.c 2013 working–group meetings and associated future initiatives
The IGS TWG presently meets twice per year: once in the spring/summer at either
the European Geosciences Union (EGU) meeting or the IGS Workshop, and once at theAmerican Geophysical Union Fall Meeting (December). 2013 meetings were as follows:
3.c.1 5 June 2013:
The chair was unable to travel to Europe in Spring 2013, causing the WG to conduct its
first–ever online–only meeting 5 June 2013 courtesy of the IGS gotomeeting.com membership. Presentations were made on a) WG business and progress on automating thetroposphere estimate comparisons (C. Hackman), b) tropo–comparison database development at GOP (J. Dousa) and c) the COST1 GNSS4SWEC initiative (G. Guerova,
Univ. Sofia).
3.c.2 10 December 2013, San Francisco, CA (with gotomeeting.com coverage):
Presentations were made by a) C. Hackman (WG business, updates on tropo–comparison
project), and b) J. Dousa (details of the tropo–comparison project), with c) a paper andpresentation by D. Sguerso’s Univ. of Genoa group on their 14–year set of tropospheredelays for the French–Italian border region submitted as a contribution to the meeting as
well.
This meeting included lively discussion on a variety of new/old topics as well:Re–establishment of comparison of IGS analysis–center troposphere estimates withIGS Final Estimates:
Comparison of troposphere estimates computed at IGS analysis centers to the IGS
Final Estimates has been discontinued for several years. Discussions at this meeting indicated that there is significant interest in re–establishing these comparisons.
Action on this will therefore be forthcoming.
1

COST: European Cooperation in Science and Technology; http://www.cost.eu

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TROPOSPHERE WG
Standardization of “tropo_sinex” format: The sinex_tro ver. 0.01 format originally proposed in 1997 for distribution of IGS troposphere values (http://igscb.jpl.nasa.
gov/igscb/data/format/sinex_tropo.txt) was not a “true” SINEX format: whilesome blocks were borrowed from SINEX, non–SINEX blocks were introduced as well.
This format was unofficially adopted/put into use and later extended to accommodate troposphere gradients, but meanwhile, other space–geodesy techniques had
adopted the format and not all technique communities named gradient (and other)parameters the same way. For example, while the IGS uses N/E gradient labels
TGNTOT/TGETOT as well as STDEV, VLBI uses GRN_EST/GRE_EST, and
STDDEV (note extra “D”), e.g., http://ivs.nict.go.jp/mirror/products-data/sinex_v2_trop.txt
IGS TWG action toward officially standardizing/adopting some troposphere SINEX–
like format was proposed informally several times in 2013 due to (a) development of
the automated tropo–comparison database and (b) COST GNSS4SWEC/EUREF
initiatives toward addressing the problem.
Attendees of the 10 December 2013 IGS TWG meeting agreed that while the WG
needs to take action on this, it also would be wise to finish one large project (theautomated tropo–comparison database) before beginning another. It is likely that
this matter will therefore be discussed in light of “Should this be the next big WG
project?” at the 2014 IGS Workshop.
Repro 2 troposphere estimates, day–boundary discontinuities, and meteorology/
climate–change–community needs:
Repro 2 troposphere processing has not yet begun because it will be performed using PPP and must therefore await completion of the Repro 2 orbits/clocks/EOPs.
The meteorology/climate–change user community, e.g., COST GNSS4SWEC WG3,plans to use Repro 2 troposphere values for their research and is thus interested in Repro 2 estimate quality. The day–boundary discontinuities in troposphere estimatesassociated with the IGS–prescribed 24–hour processing window create problems forthe meteo community. A vigorous discussion of IGS standards vs meteo–community
needs thus ensued at the 10 December 2013 TWG meeting.
The meteo and IGS parties agreed to continue working together on this since no one
present knew how to create a win–win solution. IGS President Urs Hugentobler has
since volunteered to assign a bachelors–thesis project of studying the discontinuities
in IGS troposphere estimates. His assistance is gratefully acknowledged.

4 Presentations Contributed to Working–Group Meetings
The following can be obtained by contacting the lead author of this report:

186

References
5 June 2013:• J. Dousa and G. Gyori. GOP Tropo Database. 11 pp.
• C. Hackman. IGS TWG Meeting. 43 pp.

• J. Jones, G. Guerova, O. Bock, S. de Haan, G. Dick, J. Dousa, G. Elgered, R. Pacione, E. Pottiaux, and H. Vedel. Advanced GNSS Tropospheric Products for Monitoring Severe Weather Events and Climate (GNSS4SWEC). Originally presented
at COST Earth System Science and Environmental Domain Committee Hearing 17
September 2012. 30 pp.
10 December 2013:• J. Dousa. GOP–TropDB: IGS TropoWG – Progress Report. 7 pp.
• C. Hackman. IGS Troposphere Working Group Meeting. 13 pp.

• G. Agrillo, B. Federici, L. Labbouz, D. Sguerso, and A. Walpersdorf. A Space–
Temporal Monitoring of ZTD Parameters on 14 Years in French–Italian Neighbouring Area. Originally presented at the VIII Hotine–Marussi Sympsium, Rome, June
2013. 43 pp.
• D. Sguerso, L. Labbouz, and A. Walpersdorf. 14 Years of GPS Tropospheric Delaysin the French–Italian Border Region: a Data Base for Meteorological and Climatological Analyses. 8 pp.

References
Byram, S. and C. Hackman. Computation of the IGS Final Troposphere Product by the
USNO. IGS Workshop 2012, Olstzyn, Poland, 2012.
Boehm, J., A. Niell, P. Tregoning., and H. Schuh. Global Mapping Function (GMF): A
New Empirical Mapping Function Based on Numerical Weather Model Data. Geophysical Research Letters, 33(7), L07304, 2006. doi: 10.1029/2005GL025546.
Dach, R., U. Hugentobler, P. Fridez, and M. Meindl (eds). Bernese GPS Software Version
5.0 (User Manual). Astronomical Institute, University of Bern, Switzerland, 2007.
Gyori, G., and J. Dousa. GOP–TropDB Developments for Tropospheric Product Evaluation and Monitoring – Design, Functionality and Initial Results. In review at International Association of Geodesy Symposia, 2014.
Hackman, C. IGS Troposphere Working Group email IGS–TWG–60. http://igscb.jpl.
nasa.gov/mailman/listinfo/igs-twg, 2013.

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Hackman, C. and S. Byram. IGS Troposphere Working Group 2012. In: R. Dach, Y. Jean
(Eds): IGS Technical Report 2012, IGS Central Bureau, pp. 195–202, 2013.
Noll, C. NASA Goddard Space Flight Center. http://cddis.gsfc.nasa.gov, personalcommunication, 2014.
Teke, K., J. Böhm, T. Nilsson, H. Schuh, P. Steigenberger, R. Dach, R. Heinkelmann,
P. Willis, R. Haas, S. García–Espada, T. Hobiger, R. Ichikawa, and S. Shimizu.
Multi–Technique Comparison of Troposphere Zenith Delays and Gradients During
CONT08. Journal of Geodesy, 85(7):395–413, 2011. doi: 10.1007/s00190-010-0434--y.
Zumberge, J. F., M. B. Heflin, D. C. Jefferson, M. M. Watkins, and F. H. Webb. Precise
Point Positioning for the Efficient and Robust Analysis of GPS Data from Large
Networks. J. Geophys. Res., 102(B3):5005–17, 1997.

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References

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Appendix A. IGS Troposphere Working Group Members
Last NameFirst Name

Institution

Country

Ahmed
Amirkhani
Bar–Sever
Bevis
BosserBosy

FurqanMohammadYoaz
Mike
PierreJaroslaw

Luxembourg
Iran
USA
USA
FrancePoland

Braun
Byram
Byun
CaloriChen
Colosimo
CrespiDick
Dousa
Drummond
Ghoddousi–Fard
Guerova
GutmanHackmanHeinkelmann
Herring
Hilla
Hobiger
Jones
Langley
Leighton
Liu
Moeller
Moore
NegusiniJohn
SharylSung
AndreaJunping
Gabriele
MattiaGalina
Jan
Paul
Reza
Guergana
Seth
Christine
RobertTom
SteveThomasJonathanRichard
Jon
GeorgeGregorAngelyn
Monia

Nordman
PacionePenna
Perosanz
Pottiaux
PrikrylRockenSantosSchaerSchoenSguersoSoudarin
TeferleTraceyvan der Marel
Wang
WillisXu
Zhang

Maaria
Rosa
Nigel
Felix
Eric
Paul
Chris
MarceloStefanSteffen
Domenico
Laurent
NormanJeffrey
Hans
Junhong
PascalZong–qiu
Shoujian

Universite du Luxembourg
Islamic Azad Univ. Tehran
Jet Propulsion Laboratory (JPL)
Ohio State University
ENSG/DPTS
Institute of Geodesy and Geoinformatics;
Wroclaw University of Environmental
and Life Sciences
UCAR
USNO
JPL
Univ. Roma La Sapienza
Shanghai Astronomical Observatory
Univ. Roma La Sapienza
Univ. Roma La Sapienza
GFZ
GOP
TrimbleNatural Resources Canada
Univ. Sofia
NOAA
USNO
GFZ
MIT
NGS/NOAA
Natl. Inst. of Info. & Comm. Tech. (NICT)Met Office UK
Univ. New Brunswick
3vGeomatics
Hong Kong Polytechnic University
TU Wien
JPL
Inst. Radioastronomy (IRA);
National Inst. Astrophysics (INAF)
Finnish Geodetic Inst.
ASI/CGS
Univ. Newcastle
CNES
Royal Obs Belgium
Communications Research Centre, Canada
GPS Solutions
Univ. New Brunswick
AIUB
Inst. Erdmessung, Leibniz Uni HannoverLab. Geodesy, Geomatics, GIS; Univ. Genoa
Collecte Localisation Satellites
Universite du Luxembourg
USNO
TU Delft
UCAR/NCAR
Inst. de Physique du Globe de Paris
Liaoning TU
Wuhan Univ.

190

USA
USA
USA
Italy
China
Italy
Italy
Germany
PolandUSA
CanadaBulgaria
USA
USA
Germany
USA
USA
Japan
UK
CanadaCanada/UK
Hong Kong
AustriaUSA
Italy
Finland
Italy
UK
FranceBelgium
CanadaUSA
CanadaSwitzerland
Germany
Italy
FranceLuxembourg
USA
Netherlands
USAFranceChina
China

Appendix B. IGS Troposphere Working Group Charter

Appendix B. IGS Troposphere Working Group Charter
IGS TROPOSPHERE WORKING GROUP CHARTERGNSS can make important contributions to meteorology, climatology and other environmental disciplines through its ability to estimate troposphere parameters. Along withthe continued contributions made by the collection and analysis of ground–based receivermeasurements, the past decade has also seen new contributions made by space–based
GNSS receivers, e.g., those on the COSMIC/FORMOSAT mission [1]. The IGS therefore
continues to sanction the existence of a Troposphere Working Group (TWG).
The primary goals of the IGS TWG are to:• Assess/improve the accuracy/precision of IGS GNSS–based troposphere estimates.
• Improve the usability of IGS troposphere estimates.

o Confer with outside agencies interested in the use of IGS products.

o Assess which new estimates should be added as “official” IGS products, andwhich, if any, official troposphere product sets should be discontinued.
• Provide and maintain expertise in troposphere–estimate techniques, issues and applications.
Science background
The primary troposphere products generated from ground–based GNSS data are estimatesof total zenith path delay and north/east troposphere gradient. Ancillary measurementsof surface pressure and temperature allow the extraction of precipitable water vapor fromthe total zenith path delay.
Water vapor, a key element in the hydrological cycle, is an important atmosphere greenhouse gas. Monitoring long–term changes in its content and distribution is essential forstudying climate change. The inhomogeneous and highly variable distribution of the atmospheric water vapor also makes it a key input to weather forecasting.
Water vapor distribution is incompletely observed by conventional systems such as radiosondes and remote sensing. However, ground– and space–based GNSS techniques provide complementary coverage of this quantity. Ground–based GNSS observations produce
continuous estimates of vertically integrated water vapor content with high temporal resolution over a global distribution of land–based locations; coverage is limited over theoceans (where there is no land). Conversely, water vapor can be estimated from space–borne GNSS receivers using ray tracing techniques, in which case solutions with high vertical resolution (laterally integrated over few hundred kilometers) and good oceanic/landcoverage are obtained; these solutions however are discontinuous in geographic locationand time.

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Be it resolved that the IGS troposphere WG will:• Support those IGS analysis centers providing official IGS troposphere products.

• Increase awareness/usage of IGS troposphere products by members of the atmospheric, meteorology and climate–change communities. Solicit the input and involvement of such agencies.
• Create new IGS troposphere products as needed (as determined by consultation withthe potential user community).
• Determine the uncertainty of IGS troposphere estimates through comparison of solutions with those obtained from independent techniques, or through other means
as appropriate.
• Promote synergy between space–based and ground–based GNSS techniques throughinteraction with researchers in both fields.

References:[1] Schreiner, W., C. Rocken, S. Sokolovskiy, S. Syndergaard and D. Hunt. Estimates of the
precision of GPS radio occultations from the COSMIC/FORMOSAT–3 mission. GRL
34, L04808, doi:10.1029/2006GL027557, 2007.
[2] Teke, K., J. Böhm, T. Nilsson, H. Schuh, P. Steigenberger, R. Dach, R. Heinkelmann,
P. Willis, R. Haas, S. García–Espada, T. Hobiger, R. Ichikawa and S. Shimizu. Multi–
technique comparison of troposphere zenith delays and gradients during CONT08.
Journal of Geodesy, 85(7):395–413, 2011. doi: 10.1007/s00190-010-0434-y.

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EDITOR
Astronomical Institute
University of BernIGS C entral B ureau
J et P ropulsion L aboratory
MS 238-540
P asadena , CA 91109 USA
P hone : +1 (818) 354-2077
F ax : +1 (818) 354-8545
http://www.igs.org
cb@igs.org

IGS is a Service of:International Association of Geodesy
International Union of Geodesy and Geophysics

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