TECHNICAL REPORT2014

EDITORSYOOMIN JEAN
ROLF DACHASTRONOMICAL INSTITUTE
UNIVERSITY OF BERN

Technical Report 2014
IGS Central Bureau
http://www.igs.org

Editors: Y. Jean, R. Dach
Astronomical Institute, University of Bern
Published in May 2015

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 2015, by Yoomin Jean, Rolf Dach (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 2014 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 2014.
This report is available online as PDF version at
ftp://igs.org/pub/resource/pubs/2014_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
Central Bureau

11

R. Neilan, S. Fisher, G. Walia, R. Khachikyan, D. Maggert, G. Mize,
A. Craddock, and J. Ceva

II

Analysis Centers

19

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

21

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

35

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

41

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

52

M. Fritsche, Z. Deng, M. Ge, T. Nischan, M. Uhlemann, G. Beeskow,
A. Brandt, M. Bradke, and M. Ramatschiv

Contents
Geodetic Observatory Pecný (GOP)
No report submitted
Centre National d’Etudes Spatiales/Collecte Localisation Satellites (CNES/CLS)

62

S. Loyer, F. Mercier, F. Perosanz, H. Capdeville, A. Mezerette, andL. Lestarquit
Jet Propulsion Laboratory (JPL)67

S. Desai, W. Bertiger, M. Garcia-Fernandez, 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)

72

C. Hackman, S. M. Byram, V. J. Slabinski, J. Tracey, and J. R. Rohde
University of Wuhan (WHU)81

C. Shi, M. Li, Q. Zhao, and Y. Lou
EUREF Permanent Network (EPN)89

C. Bruyninx, A. Araszkiewicz, E. Brockmann, A. Kenyeres, R. Pacione,
W. Söhne, G. Stangl, K. Szafranek, and C. Völksen
SIRGAS

101

L. Sánchez

III Data Centers
Infrastructure Committee
I. Romero

vi

111
113

Contents
Crustal Dynamics Data Information System (CDDIS)

115

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

127
129

R. Schmid
Bias and Calibration Working Group133

S. Schaer
Clock Products Working GroupNo report submitted
Data Center Working Group141

C. Noll
Ionosphere Working Group145

A. Krankowski, Y. Cherniak, I. Zakharenkova, R. Langley, M.D. Butala, A. Komjathy, T.F. Runge, B.D. Wilson, X. Pi, A.J. Mannucci,
M. Hernandez–Pajares, and P. Vergados
Multi–GNSS Working Group161

O. Montenbruck and P. Steigenberger
Space Vehicle Orbit Dynamics Working GroupNo report submittedvii

Contents
Real–Time Service

171

L. Agrotis, M. Caissy, A. Ruelke, and S. Fisher
Reference Frame Working Group179

P. Rebischung, B. Garayt, and Z. Altamimi
RINEX Working GroupNo report submitted
Tide Gauge Benchmark Monitoring Project187

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

203

Part I

Executive Groups

1

IGS Governing Board
Technical Report 2014
The Development of the IGS in 2014
– The Governing Board’s Perspective
Urs Hugentobler
Technische Universität München, Munich, Germany

1 Introduction
Since its founding twenty years ago the IGS developed rapidly as a service of the IAG.
The IGS tracking network grew from some 30 stations to well over 400 today, with orbit
quality improving from a level of several decimeters down to a few centimeters. Since
its beginning the IGS provides, on an openly available basis, the highest quality GNSS
data, products and services for a large variety of applications that benefit the scientificcommunity and society. This impressive success and achievement of a collaborative effort
were commemorated at the anniversary workshop “Celebrating 20 Years of Service” heldin June 2014 in Pasadena, California. There were several other accomplishments in 2014,
such as the launch of a new website, the extension of the MGEX network to more than
100 tracking sites worldwide, and the revision of the Terms of Reference. But the IGS
also continues to face challenges, such as the difficulty to find a new Analysis Center
Coordinator. This report describes some highlights, and challenges, in 2014 as well as
related GB activities.

2 IGS Operational Activities
The daily routine operations are the heart of the IGS. Various components of the service
ensure that tracking data and products are made publicly available every day. About 440
tracking stations are maintained and operated globally, by many institutions and station
operators, making tracking data available at different time latencies, from daily RINEX

3

IGS Governing Board
files to real–time streams. The amount of IGS tracking data and products held by eachof the four global Data Centers on permanently accessible servers increased over the lastyear by 2 TB to a total of 11 TB (135 million files) while significant additional storage
capabilities are provided by regional Data Centers. Twelve Analysis Centers and a numberof Associate Analysis Centers utilize tracking data from 70 to more than 350 stations togenerate precision products up to four times per day. Product Coordinators combine theseproducts on a continuous basis and assure the quality of the products made available tothe users. About 700 IGS final, rapid, ultra–rapid and GLONASS–only product files,
and 126 ionosphere files are made available per week as well as daily troposphere files formore than 300 stations. A total of 640 million tracking data files (60 TB) and 110 million
product files (15 TB) were downloaded in 2014 from CDDIS, one of the four global Data
Centers, by more than 10,000 unique hosts – demonstrating the intense interest of users
in IGS data and products. The Central Bureau has the responsibility for day–to–day
management, interaction with station operators, and answering typically some 150–200
questions and requests from users per month. All these activities are performed year
round, on a day–by–day basis, with high redundancy and reliability – an impressive effort
which is only possible by a strong engagement of many individuals and the support ofmore than 240 institutions worldwide.

3 IGS Highlights in 2014
The highlight of 2014 was without question the 20th Anniversary IGS Workshop. It
demonstrated that with constructive collaboration, the IGS has accomplished over the
past twenty years what no single entity could do alone and provided the forum to discuss
the future developments of our service. On August 28 the launch of the new and extensively
reorganized IGS website at www.igs.org, which was developed with strong support fromUNAVCO, could be announced. Our Real–Time Service is running smoothly and withan availability exceeding 99% under the auspice of our Real–Time Analysis Coordinator.
At the end of 2014, about 500 users from 66 countries worldwide were registered at theCB, most of them from academia, from engineering services and from GNSS equipment
and software manufacturers. The MGEX network has grown to some 120 multi–GNSS
tracking stations. Six Analysis Centers compute orbits for three new satellite systems. A
RINEX3 transition plan, developed under the guidance of the Infrastructure Committee,
was endorsed by the Governing Board; the plan defines the steps required for a transition
to long filenames for RINEX3 files, a prerequisite for the transition of the multi–GNSS
IGS activities into routine operations. The reprocessing activities are almost completedwith the contribution to ITRF2014 being finalized. The 2014 highlights were accompanied
by several major challenges, the most important being the departure of Jake Griffiths as
Analysis Center Coordinator.

45 Revision of Terms of Reference

4 IGS Workshop “Celebrating 20 Years of Service”
The highlight of 2014 was the IGS workshop held from June 23 to 27 in Pasadena, California, USA, where 189 attendees celebrated 20 years of service. It was a forum to lookback to the impressive achievements of the IGS in the last twenty years, to determine
the status of the IGS today, and to discuss the steps for the next twenty years in fruitfultechnical, organizational and strategic discussions.
Rolf Dach, as the chair of the Scientific Organizing Committee, together with Shailen
Desai and Andrzej Krankowski, put together an excellent scientific program, while theLocal Organizing Committee, led by Ruth Neilan and Steve Fisher, strongly supported
by Allison Craddock, made sure that we could work in an excellent environment taking
advantage of the facilities of the CalTech Campus. The workshop format allowed enoughtime for discussions and splinter meetings. The program included an ice breaker party,
a conference dinner and an Anniversary Colloquium, and was complemented by thrilling
matches transmitted from the Soccer World Championships in Brazil. During the breaks
we were served excellent coffee, and the whole week was favored by the best Californian
weather.
The scientific program included plenary and poster sessions focusing on the Real–Time
Service and its applications, the progress and developments in the MGEX project, the
IGS infrastructure, antenna calibrations, format issues, the reference frame and the reprocessing effort, orbit modeling effects in IGS products, ionosphere and troposphere modeling, and diverse applications of IGS products. The workshop presentations, posters,
and recommendations, including videos recorded from the presentations, can be found at
http://igs.org/presents. The Workshop compendium is available at http://kb.igs.
org/hc/en-us/articles/204895687.

5 Revision of Terms of Reference
After a first discussion of modifications of the Terms of Reference (ToR) at the December
2013 GB meeting the proposed changes prepared by the CB and Executive Committee
were extensively discussed at the June 2014 GB meeting and approved by email vote on
October 15, 2014. The new ToR include three important changes:
1. The mission statement of the IGS was updated, now explicitly mentioning the open
availability of data and products as a basic principle of the IGS.
2. In order to underline the importance of the IGS Real–Time Service the Real–Time
Analysis Coordinator was designated a voting member of the GB. The number ofvoting members thus was increased up to 19 and Loukis Agrotis, the IGS Real–Time
AC was welcomed as a new member of the GB.

5

IGS Governing Board
3. The position of a Chair–elect as non–voting member was installed in order to allow
for a smoother transition from one GB chair to the next with an overlap period ofat least one year.
Finally, the definition of the different product types was cleaned up throughout the text.

6 Governing Board Meetings in 2014
The GB discusses the activities of the various components, sets policies and monitors
the progress with respect to the agreed strategic plan using newly developed tools. The
Board met three times in 2014. A GB business meeting took place on April 27 associatedwith the EGU General Assembly in Vienna, the 43rd GB meeting took place on June
22 with a wrap–up meeting on June 27. The 44th GB meeting, the regular end–of–year
meeting, took place on December 15 during the AGU Fall Meeting in San Francisco.
The IGS Executive Committee – 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 – has met five times in 2014 by teleconference.
Topics covered at the different meetings included the preparations for the IGS Workshop in
June, the update of the Terms of Reference, the progress of the Multi–GNSS Experiment,
Real–Time Service and RINEX3, the launch of the new IGS website, and the search for a
new ACC.
A summary of the GB meeting in December 2014 may be found in IGS Mail 7024 and in
the IAG Newsletter of January 2015. Tab. 1 lists the important events in 2014.
Table 1: IGS events in 2014
Date
Apr. 27
Jun. 22

Jun. 23–27
Oct. 15
Dec. 15

6

Event
GB Business Meeting in Vienna (EGU)
43rd GB Meeting in Pasadena with wrap–up meeting on June 27– Reappointment of Chuck Meertens for a further term of four years– Extension of MGEX project until end of 2015
IGS Workshop “Celebrating 20 Years of Service” in Pasadena, USA
Updated Terms of Reference approved by the GB– Loukis Agrotis new voting member of the GB
44th GB Meeting in San Francisco (AGU)– Gary Johnston elected as new Chair of the GB– Rolf Dach elected as Analysis Center Representative– Carine Bruyninx re–elected as Network Representative8 Outreach

7 Governing Board Membership
A number of changes in the GB membership took place in 2014. As the term of Urs Hugentobler as Chair of the GB ended 2014, a Search Committee consisting of Urs Hugentobler(Chair), Chris Rizos and John Dow sought candidates for the position. Marek Ziebart(University College London) and Gary Johnston (Geoscience Australia) were ready tostand for election by the GB and gave very strong and visionary statements on theirideas for the future development of the IGS. Both received strong support by the voting
members of the GB. However Gary Johnston was elected as the new Chair of the IGS for
2015–2018.
Two positions were up for elections, namely an Analysis Center Representative and a
Network Representative, as the terms of Urs Hugentobler and Carine Bruyninx ended at
the end of 2014. Six candidates agreed to stand in the elections, which were organized
by a Nominating Committee consisting of Chuck Meertens (Chair), Carey Noll, and Ralf
Schmid. The candidates were Rolf Dach, Mathias Fritsche and Tom Herring as Analysis
Center Representatives, and Carine Bruyninx, Ludwig Combrinck and Yuki Hatanaka
as Network Representatives. All candidates received strong support from the Associate
Members. As a result of the election Rolf Dach (University of Bern, Switzerland) was
elected as Analysis Center Representative and Carine Bruyninx (Royal Observatory of
Belgium, Brussels) was re–elected as Network Representative.
With the update of the Terms of Reference the Real–Time AC became a voting member of
the GB. Loukis Agrotis (ESA/ESOC) was welcomed as a new voting member of the GB in
October 2014. Unfortunately Jake Griffiths decided to leave NGS and ended his position
as Analysis Center Coordinator on May 18. Jake’s departure was a severe loss to the IGS;
his position was taken over by Kevin Choi who demonstrated excellent competences ascoordinator of the IGS analysis activities.
All WG chairs whose terms concluded at the end of 2014 were unanimously extended by
the GB until 2016 based on their contributions as demonstrated at the IGS Workshop:
Andrzej Krankowski as Chair of the Ionosphere WG, Oliver Montenbruck as Chair of theMulti–GNSS WG, Stefan Schaer as Chair of the Bias and Calibration WG, Ralf Schmid
as Chair of the Antenna WG, Tilo Schöne as Chair of the TIGA WG, and Marek Ziebart
as Chair of the Space Vehicle Orbit Dynamics WG. Tab. 2 lists the members of the IGS
Governing Board for 2014.

8 Outreach
The IGS is well represented on the GGOS Coordinating Board. It plays a leadershiprole in the International Committee on GNSS (ICG), co–chairing Working Group D on
Reference Frames, Timing and Applications, and facilitating a resolution for use of ITRS

7

IGS Governing Boardby all GNSS providers, and the International GNSS Monitoring and Assessment (IGMA)
Subgroup within ICG Working Group A. In these roles the IGS participated in the ICG–9
meeting in November 2014 in Prague, Czech Republic. The IGS is also well–represented
in the International Earth Rotation and Reference Systems Service (IERS), in IAG Sub–
Commission 1.2 on reference frames, in the RTCM SC104, and others.
IGS has been involved with many outreach activities in 2014. The following list provides
a selection of presentations at international meetings and articles in geospatial magazines.
As in previous years the IGS was also given visibility as session organizers of, or presentersin, IGS–related sessions at conferences such as those of the EGU in Vienna and AGU in
San Francisco.
Selection of presentations at international meetings:• Munich Satellite Navigation Summit 2014, Munich, Germany, March 26, Panel Discussion with Georg Weber in session “Precise Point Positioning” on IGS Real–Time
Service.
• Munich Satellite Navigation Summit 2014, Munich, Germany, March 27, Munich,Panel Discussion with Chris Rizos and Urs Hugentobler in session “Monitoring of
the System Earth and Disaster Monitoring” on IGS products.
• Chinese Satellite Navigation Conference 2014, Nanjing, China, May 12–15, Montenbruck, Hugentobler, Steigenberger: “Recent Progress of IGS Multi–GNSS Experiment”.
• Wuhan University, Wuhan, China, May 26, Montenbruck, Hugentobler, Steigenberger: “The IGS Multi–GNSS Experiment (MGEX)”.
• Hong Kong Polytechnic University, HK, May 28, Rizos: “The International GNSS
Service (IGS) in a Multi–Constellation GNSS World”.
• FIG Congress, Kuala Lumpur, Malaysia, June 19, Rizos: “The IGS in a Multi–GNSSWorld”.
• 6th Asia–Oceania Regional Workshop on GNSS, Phuket, Thailand, October 9–11,
Rizos: “IGS Activities in Multi–GNSS and Real–Time Service”.
• 9th Meeting of the ICG, Prague, Czech Republic, November 9–14, Rizos, Neilan:“The IGS in its 20th Anniversary Year: New GNSS Activities Related to MGEX
and the Real–Time Service”.
Reports, Brochures, Flyers:• Technical Report 2013

• IGS Network Fact Sheet• Contribution to IERS Annual Report 20128

9 Outlook

9 Outlook
The year 2015 poses a number of challenges. The transition to RINEX3 was approved andhas to be implemented in the course of 2015. The Multi–GNSS Experiment is progressing
towards a Pilot Service, the network is further extended, new satellites are launched, andthe tracking data will be integrated into the standard IGS directory trees. It is the taskof the Governing Board to define the criteria triggering the end of the experiment phase
based on a concept note that will be drafted during 2015. A new ionosphere scintillation
product is under preparation. The Real–Time Service is moving towards Full Operational
Capability. To define the next steps forward the RT WG Chair plays a pivotal role andthe vacant position should again be filled.
Most critical is the transition to a new Analysis Center Coordinator by the end of 2015, atask of the highest priority. The challenge to find the next ACC also indicates that after
20 years the existence of the IGS cannot be taken for granted. The permanent operationof the IGS requires an every–day effort by the engaged institutions and many enthusiastic
individuals. Continuous effort is required to increase the sustainability of the Service,
which is today indispensable for numerous applications.
As outgoing Chair I would like to thank the Governing Board members for the cooperationand support they have given over the past four years, as well as all those associated with the
IGS for their continuing effort and support for advancing our Service. The IGS remains
an impressive organization, with a large number of individuals from many institutions
from all over the world devoting their expertise and investing their time to the IGS in an
exemplary spirit of cooperation. I wish our new GB Chair all the best and much successin leading the IGS into an exciting future.

9

IGS Governing Board
Table 2: IGS Governing Board Members 2014 (*: voting members, §: Executive Committee)
MemberAffiliation

Country

FunctionUrs Hugentobler*§

TU München

Germany

Loukis Agrotis*

ESA/ESOC

Germany

Zuheir Altamimi*

Institut Nationalde l’Information
Géographique et Forestière
BIPM
UNAVCO
Institut Nationalde l’Information
Géographique et Forestière
Royal Observatoryof Belgium
Natural Resources Canada
Naval Research Laboratory
Chinese Academy ofSurveying and Mapping
Jet Propulsion Laboratory
IGS Central Bureau, JPL

FranceBoard Chair
Analysis Center Representative
Real–Time Analysis Coordinator(since Oct. 2014)
IAG Representative

FranceUSA
FranceBIPM/CCTF Representative
Data Center Representative
IERS Representative

Belgium

Network Representative

CanadaUSA
Chinaformer Real–Time WG Chair
Clock Product CoordinatorAppointed

USA
USA

USA

Analysis Center Representative
IGS Central Bureau
Secretariat
Reference Frame Coordinator,
IGS Representative
to IAG Sub–commission 1.2
Analysis Center Coordinator

USA
Australia
Japan
PolandTroposphere WG Chair
Appointed
Appointed
Ionosphere WG Chair

CanadaUSA
Germany

IGS/RTCM RINEX WG Chair
Appointed
Multi–GNSS WG Chair

Felicitas Arias
Fran Boler*
Claude Boucher*Carine Bruyninx*
Mark Caissy
Michael Coleman*
Yamin Dang*
Shailen Desai*
Steve Fisher
Bruno Garayt*
Jake Griffiths*

Institut Nationalde l’Information
Géographique et Forestière
NOAA, NGSFrance(replaced by Kevin Choi in May 2014)

Christine Hackman
Gary Johnston*
Satoshi Kogure*
Andrzej Krankowski

Ruth Neilan*§

USNO
Geoscience Australia
JAXA
University of Warmia andMazury in Olsztyn
Natural Resources Canada
UNAVCODLR/German Space
Operations Center
IGS Central Bureau, JPL

Carey Noll
Chris Rizos*§NASA/GSFC
Univ. of New South Wales

Ignacio Romero
Laura Sanchez*
Stefan Schaer
Ralf Schmid
Tilo Schöne
Tim Springer*§

ESA/ESOC
DGFISwisstopo
DGFI
GFZ Potsdam
ESA/ESOC

Marek Ziebart

University College London

Ken MacLeod
Chuck Meertens*§
Oliver Montenbruck

USA

Director of IGS Central Bureau
Secretary
USA
Data Center WG Chair
Australia
President of IAG since July 2011
(before: appointed)
Germany
Infrastructure Committee Chair
Germany
Network Representative
Switzerland Bias and Calibration WG Chair
Germany
Antenna WG Chair
Germany
TIGA WG Chair
Germany
Analysis Center Representative
IGS Representative to IERS
Chair of Associate Members Committee

10

UKSpace Vehicle Orbit Dynamics WG
Chair

IGS Central Bureau
Technical Report 2014
R. Neilan1 , S. Fisher1 , G. Walia1 ,R. Khachikyan2 , D. Maggert3 , G. Mize3 ,A. Craddock4 , J. Ceva4
1. NASA/Jet Propulsion Laboratory, Caltech, Pasadena, California
2. Raytheon, Inc., Pasadena, California
3. UNAVCO, Inc., Boulder, Colorado
4. SBAR, Inc., Pasadena, California

1 Introduction
The Central Bureau supports IGS 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 the CB information
system (CBIS) where the IGS web, ftp and mail services are hosted. Specific responsibilities of the Central Bureau are outlined in the IGS Terms of Reference (see www.IGS.org).
The CB is hosted at the California Institute of Technology/Jet Propulsion Laboratory andis funded by NASA. It contributes significant staff, resources and coordination to advancethe IGS mission.
In 2014, the CB staff included part time contributions by the individuals listed in Tab. 1
together with their corresponding roles within the CB. Regrettably, funding limitations
have resulted in an approximate 1.5 fte reduction in the CB staff since October 1 that is
anticipated to continue through at least the NASA fiscal year ending in September 2015.

2 Board Participation
R. Neilan and S. Fisher continued to fulfill designated GB responsibilities on behalf of the
CB in 2014. The entire CB staff helps to facilitate the GB meetings and interaction, and11

IGS Central Bureau
Table 1: Central Bureau staff members 2014
Name

Role

Ruth Neilan
Steve Fisher
Gaurav Walia
Robert Khachikyan

Director
Operations Manager
Development Manager
Information Systems Manager
Co–Network Coordinator (through September)
Co–Network Coordinator
Database/web Developer
Management Support
Outreach and Communications Specialist

David Maggert
Gary Mize
Juan Ceva
Allison Craddock

acts on behalf of the GB to implement decisions and defined action items. Three meetingsof the Governing Board were coordinated in 2014 (Vienna/April, Pasadena/June, and San
Francisco/December), as well as 5 tele–conference meetings of the Executive Committee
through the year. Minutes of these meetings are available by request from the CB. The
CB also continued participating on other IAG and services Boards in 2014: R. Neilan
participates on the GGOS Coordinating Board and Executive Committee and S. Fisher
fulfills one of the two IERS Directing Board positions allocated to IGS (though NASAsupport for this activity was temporarily suspended due to budgetary constraints as of
October 1).

3 Associate Members and GB Elections
The CB helped the IGS Associate Member Committee review and renew the IGS Associate
List, which is done routinely every other year, and supporting the Governing Board andChair elections by operating the online polling system. The current Associate Member
and GB Member lists are available online at http://igs.org/about/organization.

4 Terms of Reference Review
A review of the IGS Terms of Reference was facilitated by the CB and approved during
the December GB meeting. The updated version has been published online at http://kb.igs.org/hc/en-us/articles/204189428.

12

7 Website Development

5 IGS 20th Anniversary Workshop Organization
All of the local preparations, registrations and coordination with program committee
were conducted by the CB. Approximately 190 people attended the 5 day long workshop, which included plenary presentations, Working Group splinter meetings, posters
and social events. Information about the Workshop, including the key recommendations
that were developed, are published online at http://kb.igs.org/hc/en-us/sections/
200369263.

6 Strategic Plan/ Progress
The year of 2014 marked the second full year of formal monitoring of progress on Strategic
Plan objectives. The 2014 update of the IGS Dashboard of performance metrics tracked by
the CB is published online at http://kb.igs.org/hc/en-us/sections/200623533. The
2015 Strategic Implementation Plan which defines the principal IGS activities throughthe year was compiled by the CB with input from the Component leads and approved by
the GB during the December meeting. It is published online at http://kb.igs.org/hc/
en-us/sections/200287408.

7 Website Development
The updated IGS website was released in beta in May for broad review by IGS participants
and users. The first production release in October marked the official switchover to the
new site, though the old website remnants active for legacy purposes. With this release,the phase I development goals were completed that resulted in the following improvements
in 2014:• New navigation and graphics were introduced.

• All content was re written or otherwise updated.

• A consistent template for WG content was introduced and working with WGs to
improving information content.
• Most key processes have been migrated to globally available external servers.

• Knowledge Base functionality was implemented and populated with all relevant information from the old IGS website.
• Workflows for backup and disaster recover across all CB servers were reviewed anddocumented.

13

IGS Central Bureau• The Site Log Manager database application was released for production use by the
IGS station operators– Completed testing phase, now in production with approximately 45 registeredusers representing all of the largest station operators and a majority of stations.
– The database has been populated with all categories of IGS stations – full IGS,
MGEX, RTS, proposed, dormant, etc.
– The external user interface is via the website network page.
– Information is updated by the Station Operators either within the database or
by text or XML log exchange.
– Supporting XML metadata exchange, scripts schema implemented, have identified improvements to this that we are coordinating through the data center
WG.
– Database is used to generate the main IGS SINEX file, working on a single
unified SINEX file that includes additional select MGEX and RTS stations to
be fully integrated within IGS.
– Participated in 2014 IGS Workshop with poster and breakout demonstrationof the Site Log Manager.
– Videos and user documentation are in the KB at http://kb.igs.org/hc/
en-us/sections/200562873.

8 Network/station management
There are 453 official stations within the IGS network at the end of 2014. Eighteen newstations were added in the past year (Tab. 2) that required significant coordination withstation operators in processing the applications, and verifying station meta data and data
files. Five stations that had been decommissioned in 2014 were deleted from the active
network list. Additional site data and meta data were processed and verified for 17 new
MGEX (now totaling 115) stations, and processing and verification of metadata for 18
NGA stations whose historical data was provided to IGS was completed. Thirty–nine new
equipment models were added to the rcvr_ant.tab and available sketches with their ARP
definitions were added to the antenna.gra.

149 Project Support, Committee and Working Group Participation
Table 2: New IGS stations in 2014
StationLocation

ARUC
DAKR
GODN
GODS
GRAC
JFNG
KIRI
KRGG
MELI
METG
NAUR
POHN
SEYG
TONG
TUVA
SEJN
LCK3
LKC4

Aruch–Yerevan, Armenia
Dakar, Senegal
Greenbelt, MD, USA
Greenbelt, MD, USA
Caussols, France
Jiufeng, China
Betio, Kiribati
Kerguelen Islands
Melilla, Spain
Metsahovi, Finland
Nauru, Nauru
Pohnpei, Micronesia
Pointe Larue, Seychelles
Naku’alofa, Tonga
Funafuti, Tuvalu
Sejong, Korea
Lucknow, India
Lucknow, India

9 Project Support, Committee and Working Group
Participation
The CB has continued to broadly support the IGS Working Groups and Projects. Progressin 2014 has included:• Regular coordination with IC on broad range of network and other matters, participating in RINEX3 transition planning.
• Operate RTS website, caster, user registrations, user support. Maintain redundantstation streams from 75 priority stations. Participate in RT WG activities to develop
the IGS/RTS network.
• Coordinating with COSMIC to participate within IGS, helping to define COSMIC/LEO ground subnetwork and shared stations.
• Supporting MGEX website, integrated MGEX station meta data within SLM.

• Participate on Antenna WG and maintain antenna and equipment files on IGS website.
• Interface with all other WGs as necessary on a variety of topics.

15

IGS Central Bureau
Table 3: External meetings where the CB participated in 2014
Month

LocationJanuary
February
March/April
April
May

Geneva, Switzerland (IAG/GGOS Plenary Session)
Greenbelt, MD (IGS/SGP Meetings at Goddard)
Paris, France (10th Meeting of WDS Science Committee)
Vienna, Austria (SGP Programmatic Meetings)
Boulder, CO (IGG10 location scouting/planning with
State Department and UN–OOSA)New York, NY and Washington, DC (UN GGIM, GGOS Forum,plus SGP meetings at Headquarters)
Boulder, CO (Programmatic meetings with UNAVCO and UCAR)New Delhi, India (SciDataCon 2014)
Prague, Czech Republic (ICG–9)
Washington, DC (PNT Advisory Board Meeting,
Programmatic meetings NASA HQ)
San Francisco, CA (IGS and GGOS Board and related meetings)

July
AugustOctober/November
November
December
December

10 IGS User Support
The CB provides the first level of technical and other support on behalf of IGS to anyone
who inquires through the IGS website and CB mail (support@ and cb@). In 2014 just over
2900 emails were sent through these addresses, which is consistent with the last several
years that this has been monitored by the CB. The Knowledge Base support systemthat was implemented this year includes trouble ticketing functionality which we haveintegrated with the current e–mail based support system to help provide better response
and efficient tracking of support issues.

11 Outreach/External Participation
The CB has continued to aggressively reach out to external stakeholders on behalf of the
IGS by broadly participating in external meetings that relate to the IGS interests (Tab. 3),
participating in policy interactions with various groups (Tab. 4), and by promoting standards for the open exchange GNSS data, products and information with the appropriate
standards organizations (Tab. 5).

16

11 Outreach/External Participation

Table 4: Policy interactions where the CB participated in 2014
Organization

CB’s role/activities

UN

International Committee on GNSSUN

GGIM Global Geodetic
Reference Frame WG
World Data System
Global Geodetic Observing System

ICSU
IAG
NASA

CB co–chairs the WG–A activities
and is supporting planningfor the 10th Anniversary ICG Meeting
CB participates on the WG on behalf of IGS
CB represents IGS membership in WDS
CB Director is a Coordinating Board andEC member
CB routinely interacts within NASA on GNSS
and related policy matters within
the US government and scientific organizations

Table 5: Standards for open GNSS data and exchange supported by the CB in 2014Group

Activities

IGS Infrastructure Committee
IGS Antenna Working Group
RTCM/RINEX WG
RTCM/Real–time GNSSIGS Data Center WG

GNSS site and networks standards
Maintenance of the IGS equipment files
Participate RINEX3 activities
Participate RTCM SC–104 activities
Participating in XML definition for exchange ofsite metadata, extending upon scripts definition
Participate in interchangeability/interoperability
monitoring standards definition

UN–ICG

17

IGS Central Bureau

12 Funding Development
Although the CB extended considerable programmatic effort to sustain its funding, now
through the NASA/Space Geodetic Program, CB funding was reduced significantly from2013 levels.

13 IGS Institute (IGSI)IGSI is now an essential, integral part of the CB. In 2014, the IGSI:• Business plan was updated (available by request).

• Supported registrations and vendor contracts for the Pasadena Workshop.
• Supported website/IT, branding and marketing activities.

• Is developing capacity/programs to accept contributions to support IGS activities
to be pursued in 2015.

14 Publications• 2014 IGS Performance Dashboard• IGS 2013 Technical Report section• 2012 IERS Annual Report – IGS section• 2014 Workshop Compendium• SGP/ICO project plan and activity report• Updated RTS and Network brochures, solicited other WG’s to provide one page
summary brochures for IGS portfolio.
• Reviewed quality of service table and found that no updates are needed18Part II

Analysis Centers

19

CODE Analysis Center
Technical Report 2014
R. Dach1 , S. Schaer2 , S. Lutz1,2 , D. Arnold1 ,H. Bock1 , E. Orliac1 , L. Prange1 , A. Villiger1 ,L. Mervarta , A. Jäggi1 , G. Beutler1 ,E. Brockmann2 , D. Ineichen2 , A. Wiget2 ,A. Rülke3 , D. Thaller3 , H. Habrich3 , W. Söhne3 ,J. Ihde3 , P. Steigenberger4 , 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• Institut für Astronomische und Physikalische Geodäsie, Technische Universität
München (IAPG, TUM), Munich, Germany
The operational computations are performed at AIUB, whereas IGS–related reprocessing
activities are usually carried out at IAPG, TUM. All solutions and products are generated
with the latest development version of the Bernese GNSS Software (Dach et al. 2007).
aInstitute of Geodesy, Czech Technical University in Prague, Czech Republic

21

CODE Analysis Center

2 CODE products available to the public
A wide range of GNSS solutions based on a rigorously combined GPS/GLONASS dataprocessing scheme is computed at CODE. The products are made available through anonymous ftp at:
ftp://ftp.unibe.ch/aiub/CODE/ or http://www.aiub.unibe.ch/download/CODE/
An overview of the files is given in Tab. 1.
Within the table the following abbreviations are used:
ddd
Day of Year (DOY) (three digits)
yyyy Year (four digits)
wwww
GPS WeekyyYear (two digits)
wwwwd GPS Week and Day of weekyymm Year, Month
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 (continued)
CODE rapid products available at ftp://ftp.unibe.ch/aiub/CODE
CODwwwwd.EPH_M
CODwwwwd.EPH_R
CODwwwwd.EPH_P
CODwwwwd.EPH_P2
CODwwwwd.EPH_5D
CODwwwwd.ERP_M
CODwwwwd.ERP_R
CODwwwwd.ERP_P
CODwwwwd.ERP_P2
CODwwwwd.ERP_5D
CODwwwwd.CLK_M
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 final rapid GNSS orbits
CODE early rapid GNSS orbits
CODE 24–hour GNSS orbit predictions
CODE 48–hour GNSS orbit predictions
CODE 5–day GNSS orbit predictions
CODE final rapid ERPs belonging to the final rapid orbits
CODE early rapid ERPs belonging to the early 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 clock product related to the final rapid orbit, clock RINEX format
CODE early 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 based on CODE rapid ionosphere
product, 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

CODE Analysis Center
Table 1: CODE products available through anonymous ftp (continued)
CODE ultra–rapid products available at ftp://ftp.unibe.ch/aiub/CODE
COD.EPH_U
COD.ERP_U
COD.TRO_U
COD.SNX_U.Z
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
SINEX file from the CODE ultra-rapid solution
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 GPS and GLONASS satellites

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 referring to the
COD–orbits from the long–arc analysis in clock RINEX format
GPS satellite and receiver clock corrections at 5–sec intervals referring 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 referring to the
COF–orbits from the pure one–day analysis in clock RINEX format
GPS satellite and receiver clock corrections at 5–sec intervals referring 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
With GPS week 1706,
CODE started to generate a pure 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 2014.

The network used by
CODE for the final processing is shown in Fig. 1. Almost 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. 2014.
In Sect. 3.1 we give an overview of important development steps in the year 2014. Section 3.2 describes the new generation of the CODE rapid products and Section 3.3 provides
details on the extended empirical orbit model used at CODE .

3.1 Overview of changes in the processing scheme in 2014
Table 3 gives an overview of the major changes implemented during year 2014. Details on
the analysis strategy can be found in the IGS analysis questionnaire at the IGS Central
Bureau (ftp://ftp.igs.org/pub/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

CODE Analysis Center

Table 3: Selected modifications of the CODE processing over 2014
Date

DoY/Year

Description

16-Mar-2014

075/2014

Vienna non–tidal atmospheric pressure loading model switched fromversion 2 to 4 (no effect on the products because it is deactivated withscaling factors, see Dach et al. 2013)04-Jun-2014

155/2014

Major revision of the ultra–rapid and rapid product generation:• Separated product generation and NEQ manipulation tosignificantly speed up the processing• Automatic datum definition verification• New: SINEX from ultra-rapid solution, currently with daily
resolution of the Earth rotation parameters• Setup of Z (and X/Y ) satellite antenna offsets(Z included in SNX)
• A new product line extracted from the middle day of a rapid andultra-rapid solution is implemented

10-Jun-2014

158/2014

Start to produce bias-SINEX (BIA) result files from ionosphereprocessing

10-Jun-2014

160/2014

Start to submit middle-day solutions for the IGS rapid combination froma subsequent ultra-rapid solution

12-Jun-2014

162/2014

Start to post the middle-day submissions to the IGS separately with thelabel _M files to ftp server

22-Sep-2014

264/2014

Increase the number of stations in the clock final solution(new limit is 150)

23-Sep-2014

265/2014

Increase the number of stations in the clock rapid solution(new limit is 120)

24-Sep-2014

266/2014

Clock rapid: backsubstitution of epoch parameters using only phasemeasurements (as done in final clock estimation)

14-Nov-2014

292/2014

Global ionosphere map estimation completely redesigned,
temporal resolution increased from 2 hours to 1 hour

03-Dec-2014

337/2014

Activate a completely revised RINEX data download system:• Efficient download with a multi–threading Perl tool
• Construct an XML database on the content of each RINEX file
• Evaluation of the XML database instead of the original RINEX
files for observation statistic generation

16-Dec-2014

347/2014

Improvement in the program for Helmert Transformation to be used forthe automated datum definition verification

26

3 Changes in the daily processing for the IGS

3.2 Enhancing the CODE rapid product generation
The procedure to compute ultra-rapid solutions at CODE was deeply revised in 2013
(reported in Lutz et al. 2014) . The processing of the observations results in normal
equation (NEQ) files from which different ultra-rapid solutions can be derived. Eachultra-rapid update may produce in the same way also a solution taylored for the IGS
rapid solution with a set of Earth rotation parameters (offset and drift) referring to noon
and an estimated orbit arc from midnight to midnight for the day before the ultra-rapid
solution itself.
Starting with day 155 of year 2014 (04–June–2014) the traditional rapid solution from
CODE is submitted as the “early rapid solution” in the morning. In that case the orbit
is extracted from the end of a three day solution (see Figure 2(a)). By construction thisorbit is extracted from the most uncertain part of the arc.
The quality of the orbit can significantly be improved if the orbit arc is continued what
is, e.g., done with the subsequent ultra-rapid runs as illustrated in Figure 2(b) . The
submission schedule for the IGS rapid allows to update the rapid solution extended by
the normal equation from the ultra-rapid computation for 12:00 UTC . This new so-called“final rapid solution” is used to replace the previously submitted CODE rapid solution forthe combination.
Even if the extension of the orbit is only based on an ultra-rapid solution considering
for instance a lower number of tracking stations, the quality of the GNSS orbits in the“final rapid solution” is already close to those in the CODE final orbits. For applications
that are not so critical in time, these orbits may be interesting. For that reason they are
specifically indicated with _M on the AIUB’s FTP server (see Table 1). This allows to use
the availability of these files to trigger a certain processing based on these new “final rapid
solution” .

rapid day n−2(120 stations)rapid day n−1(120 stations)rapid day n(120 stations)rapid 3−day solution

rapid day n−1(120 stations)rapid day n(120 stations)ultra day n+1(90 stations)rapid 3−day solution

orbit interval
for the rapid(a) Early rapid solution

orbit interval
for the rapid(b) Final rapid solution

Figure 2: Principle to extract the early and final rapid products from the rapid and subsequentultra–rapid solutions.

27

CODE Analysis Center

3.3 Studies for Updating the ECOMThe Empirical CODE Orbit Model (ECOM, Beutler et al. 1994) was developed in theearly 1990s, motivated by the lack of reliable satellite information. It is widely used in the
IGS and allows for a successful modeling of non-gravitational accelerations — especiallyinduced by solar radiation pressure — acting on GPS satellites.
The ECOM decomposes the perturbing accelerations into three orthogonal directions~er × ~eD. ~rs − ~r
.
.
~eD =
, ~eY = −, ~eB = ~eD × ~eY ,|~rs − ~r||~er × ~eD |(1)where ~rs and ~r are the geocentric vectors of the Sun and the satellite, respectively, and ~er isthe unit vector associated with ~r. The vector ~eD is the unit vector in the direction satelliteSun, ~eY points along the satellite’s solar panel axis, and ~eB completes the orthogonal
system. The total acceleration of a satellite due to solar radiation pressure can then be
written as~a = ~a0 + D(u)~eD + Y (u)~eY + B(u)~eB ,(2)where ~a0 is a selectable a priori model, and where u is the satellite’s argument of latitude.
In the original ECOM the functions D(u), Y (u) and B(u) are represented as Fourier
series truncated after the once-per-revolution (1pr) terms. Springer et al. 1999 proposed
the so-called reduced ECOM,
D(u) = D0
Y (u) = Y0

(3)

B(u) = B0 + Bc cos u + Bs sin u ,which was used for the IGS contributions of CODE until 5 January 2015. Up to 2005
the reduced ECOM was set up on top of the ROCK-T models, then on top of an a priori
model derived from the parameters of the ECOM (Springer et al. 1999; Dach et al. 2009).
From July 2013 to January 2015 the reduced ECOM was used at CODE without any apriori model ~a0 , after having implemented albedo modeling.
When applied to GLONASS satellites, the ECOM reveals shortcomings, which map into
spurious signals in time series of geophysically interesting parameters, like geocenter coordinates or Earth rotation parameters (ERPs). These problems grew creepingly with theincreasing influence of the GLONASS in recent years (Meindl 2011; Meindl et al. 2013).
Rodriguez-Solano et al. 2014 documented a significant reduction of the spurious signals
by replacing the reduced 5-parameter ECOM for GPS and GLONASS by an adjustablebox-wing model.
The mentioned problems asked for a thorough review of the ECOM. Arnold et al. 2015
showed that the largest deficit of the ECOM, when applied to GLONASS satellites (which
are of an elongated shape), is the lack of periodic terms in the ~eD -direction. Guided by28

3 Changes in the daily processing for the IGS
x pole differences w.r.t. IERS 08 C04
16
D4B1
D2B1
14

COF
GLONASS−harmonics

12

µas

10

8

6

4

2

0

10

20

100

200

300

500

days

Figure 3: Amplitude spectra of differences of the polar motion coordinate x w. r. t. IERS 08
C04 for solutions obtained using the old ECOM (COF) and the extended ECOM
with periodic D-terms up to 2pr (D2B1) and 4pr (D4B1). The spurious amplitude at
120 days is significantly reduced by the new ECOM.

theoretical considerations and the spectral analysis of accelerations predicted by a priori
models, the authors proposed the following extended ECOM:
D(u) = D0 +nD
X

{D2i,c cos 2i∆u + D2i,s sin 2i∆u}nBX{B2i−1,c cos(2i − 1)∆u + B2i−1,s sin(2i − 1)∆u} ,i=1

Y (u) = Y0
B(u) = B0 +

i=1

(4)

.
where ∆u = u − us , us is the argument of latitude of the Sun. The extended ECOM
thus contains even-order periodic terms in ~eD -direction and odd-order periodic terms in~eB -direction. The introduction of these terms significantly reduced the spurious signals
in time series of geocenter coordinates and ERPs (see Fig. 3), slightly decreased the orbit
misclosures at the day boundaries and considerably reduced spurious patterns in residuals
obtained within an SLR validation of the GNSS satellite orbits.
As a result of the review of the ECOM performed in Arnold et al. 2015, the CODE
IGS contributions are based on the extended ECOM (4) with nD = 2 and nB = 1 (i. e.,
including up to 4pr terms in D and 1pr terms in B) since 4 January 2015 (GPS week1826).
29

CODE Analysis Center

4 CODE contribution to the IGS–MGEX campaign
Since 2012 CODE contributes to the IGS Multi-GNSS EXperiment (MGEX) aiming at the
integration of new GNSS into existing processing chains. In 2014 CODE’s focus was on
removing bottlenecks in the Bernese GNSS Software that so far prevented the processingof more than three GNSS (GPS, GLONASS, Galileo) together. Besides the software also
the MGEX orbit and clock processing chains have been updated to BeiDou and QZSS
processing capability. Satellite clock estimates and related inter-frequency biases (IFB)
are now also provided for GLONASS. This means that CODE is now able to provide
orbits and satellite clock corrections (plus related biases) for the GNSS GPS, GLONASS,
Galileo, BeiDou (MEO and IGSO), and QZSS in a fully integrated solution.
This capability has been demonstrated on MGEX data of the whole year 2014. The
increasing number of tracking stations providing RINEX3 data (via MGEX and nonMGEX sources), the different characteristics of the involved GNSS (regional vs. global
navigation systems), and the fact that not all MGEX stations track all GNSS, made itnecessary to pay more attention to the station selection. From the RINEX pool station
subsets optimized for only one GNSS at the same time are selected paying attention toa good station distribution for the GNSS in question, respectively. The sub-networks are
merged. When forming baselines for the double-difference processing weakly observed
GNSS (QZSS, BeiDou) are preferred. Thanks to the station selection and the constantly
improving MGEX network satellite clock corrections could be provided at a rate of almost
100 percent for most involved satellites at the end of 2014. The overall number of selected
stations is limited to 130.
2.0

150

RMS of linear clock fit [ns]SLR residuals [cm]

100

50

0

−50

1.5

1.0

0.5

−100

−150
−90

−45

0
Beta [deg]

(a)

45

90

0.0
-90

-45

0

45

90

β [deg](b)

Figure 4: SLR residuals (a) and RMS of daily linear fit through estimated epoch-wise satellite
clocks (b) of QZS-1 as a function of the elevation angle of the Sun over the satellite’s
orbital plane (beta). The impact on orbit and clock estimates from ignoring the switch
of QZSS’s attitude steering mode at beta angles of ±20 degrees (Inaba et al. 2009) isclearly visible.

30

5 CODE contribution to IGS repro2
The analysis of the long time series of CODE MGEX products clearly shows that certain
models (e.g., the ECOM SRP model (Springer et al. 1999)) and assumptions (e.g., yawattitude mode is nominal) working fine for GPS and GLONASS must be re-consideredor improved if new GNSS are involved. On the other hand the MGEX results confirm
that the clocks of some new GNSS spacecraft (i.e., Galileo, QZSS, GPS IIF) are so stablethat their estimated clock corrections are suitable for orbit validation purposes (see, e.g.,
Fig. 4). These results suggest that our focus in 2015 should be on qualitative aspects,
such as the introduction of the updated ECOM RPR model (Arnold et al. 2015), attitude
modeling, and satellite antenna phase center modeling for the new GNSS. Furthermore
it is planned to deliver the CODE-MGEX ("com") products (available at ftp://cddis.
gsfc.nasa.gov/gnss/products/mgex) with a shorter delay in the future.

5 CODE contribution to IGS repro2
Detailed information on the CODE contribution to the IGS repro2 effort were alreadyprovided in Dach et al. 2014 .
In April 2014, the results are posted to the CDDIS server (ftp://cddis.gsfc.nasa.
gov/gnss/products/repro2/). Table 4 provides the list of files. The long-arc series(COD) have been published on the CODE’s FTP server (ftp://ftp.unibe.ch/aiub/
Table 4: CODE repro2 products available in weekly subdirectories at ftp://cddis.gsfc.nasa.
gov/gnss/products/repro2/.
Files generated from three–day long–arc solutions:co2wwwwd.eph.Z
co2wwwwd.snx.Z
co2wwwwd.tro.Z
co2wwww7.erp.z
co2wwww7.sum.Z

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/satellite antenna offsets from the long–arc
solution in SINEX format
GNSS 2–hour troposphere delay estimates obtained from the long–arc solution introposphere SINEX format
GNSS ERP (pole, UT1−UTC) solution, collection of the 7 daily CO2–ERP
solutions of the week in IGS IERS ERP format
Analysis summary for 1 week

Files generated from pure one–day solutions:cf2wwwwd.eph.Z
cf2wwwwd.snx.Z
cf2wwwwd.tro.Z
cf2wwww7.erp.Z
cofwwww7.sum.Z

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/satellite antenna offsets from the pureone–day solution in SINEX 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

31

CODE Analysis Center
REPRO_2013/). The publication of the reprocessing series includes the file ftp://ftp.
unibe.ch/aiub/REPRO_2013/CODE_REPRO_2013.ACN containing a detailed description of
the models used.

References
Arnold, D., M. Meindl, G. Beutler, R. Dach, S. Schaer, S. Lutz, L. Prange, K. Sosnica,
L. Mervart, and A. Jäggi. CODE’s new empirical orbit model for the IGS. Journal of
Geodesy, under review, 2015.
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/docs/DOCU50.pdf. User manual.
Dach R, E. Brockmann, S. Schaer, G. Beutler, M. Meindl, L. Prange, H. Bock, A. Jäggi,and L. Ostini. GNSS processing at CODE: status report. Journal of Geodesy 83(3–4):
353–366, 2009, doi: 10.1007/s00190-008-0281-2 .
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.
Dach, R., 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, and U. Hugentobler. CODE IGS
Analysis Center Technical Report 2013. In R. Dach, and Y. Jean, editors, IGS 2013
Technical Reports, pages 21–34, 2014. IGS Central Bureau.
Inaba, N., A. Matsumoto, H. Hase, S. Kogure, M. Sawabe, and K. Terada. Design Conceptof Quasi Zenith Satellite System. Acta Astronautica, 65(7–8):1068–1075, 2009, doi:
10.1016/j.actaastro.2009.03.068 .
Lutz, S., G. Beutler, S. Schaer, R. Dach, and A. Jäggi. CODE’s new ultra-rapid orbit
and ERP products for the IGS. GPS Solutions, accepted 2014, in press doi: 10.1007/
s10291-014-0432-2 .

32

References
Meindl M. Combined Analysis of Observations from Different Global Navigation Satellite
Systems. Geodätisch-geophysikalische Arbeiten in der Schweiz, Vol 83, Eidg. Technische Hochschule Zürich, Switzerland, 2011
Meindl M., G. Beutler, D. Thaller, A. Jäggi, and R. Dach. Geocenter coordinates estimatedfrom GNSS data as viewed by perturbation theory. Advances in Space Research, Vol
51(7):1047–1064, 2013 doi: doi:10.1016/j.asr.2012.10.026 .
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.
Rodriguez-Solano C. J., U. Hugentobler, P. Steigenberger, M. Blossfeld, and M. Fritsche.
Reducing the draconitic errors in GNSS geodetic products. Journal of Geodesy, 88:(6):559–574, 2014. doi: 10.1007/s00190-014-0704-1.
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

CODE Analysis Center

34

NRCan Analysis Center
Technical Report 2014
Brian Donahue, Reza Ghoddousi–Fard,
Yves Mireault, François Lahaye
Natural Resources Canada, Canadian Geodetic Survey
615, Booth Street, Ottawa ON, Canada K1A 0E9
E–mail: francois.lahaye@nrcan-rncan.gc.ca

1 Introduction
This report covers the major activities conducted at the NRCan Analysis Center (NRCan–AC) and product changes during the year 2014 (products labelled ’em*’). Additionally,changes to the IGS stations operated by NRCan are briefly described. Readers are referredto the Analysis Coordinator website (http://acc.igs.org) for historical combination
statistics of the NRCan–AC products.

2 NRCan Core Products
There were no major changes for NRCan–AC Ultra–Rapid, Rapid and Final (GLONASS)
core products in 2014. The Bernese GNSS Software supporting these will be updated toversion 5.2 during 2015. There were no major changes to the NRCan–AC Real–Time GPS
correction stream.
During 2014 the NRCan–AC re–estimated its core GPS products for the years 1994 to
2014. This contribution to the 2nd IGS reprocessing campaign (repro2) was carried out
using JPL’s GIPSY–OASIS Software v6.3 running on Linux servers. The NRCan repro2
products (em2) were estimated following the latest set of IGS recommended models. Also
during 2014 the NRCan–AC Final GPS products were upgraded using GIPSY–OASIS
v6.3 with the latest recommended IGS models starting with 2014–03–30. For details on
the NRCan–AC Final GPS (emr) and repro2 (em2) strategies please refer to the IGS
central bureau summary. (ftp://igs.org/pub/center/analysis/emr.acn)

35

NRCan Analysis Center
Table 1 summarizes the products available from the NRCan–AC. The Final and Rapid
products are available from the following anonymous ftp site: ftp://rtopsdata1.geod.
nrcan.gc.ca/gps/products

3 Ionosphere and DCB monitoring
Daily and near–real–time ionosphere products and DCB estimates continue to be generated internally. Following a recommendation made at the 2014 IGS workshop, hourly TEC
maps are being included in NRCan’s daily files since 2014–07–29. Contribution of daily
TEC maps to Final IGS combined global ionosphere products are awaiting evaluation by
IGS ionosphere working group chair.

4 NRCan stations contributing to the IGS network
In addition to routinely generating all core IGS products, NRCan is also providing publicaccess to GPS/GNSS data for more than 60 stations. This includes 38 stations currently contributing to the IGS network through the Canadian Geodetic Survey’s Canadian Active Control System (CGS–CACS), the CGS Regional Active Control System(CGS–RACS), and the Geological Survey of Canada’s Western Canada Deformation Array (GSC–WCDA). The NRCan contribution to the IGS network includes 22 GNSS + 16
GPS only stations. In addition, several of the most important sites have multiple monuments in order to monitor the stability of the monument and the quality of the GNSS
observations. These NRCan core sites with multiple monuments are listed in Tab. 2. Several upgrades to the CGS–CACS were completed in 2014 and these are listed in Tab. 3.
Figure 1 shows a map of the NRCan GPS/GNSS network as of January 2015. Further
details about NRCan stations and access to NRCan public GPS/GNSS data and site logs
can be found at http://geod.nrcan.gc.ca or from the following anonymous ftp site:
ftp://rtopsdata1.geod.nrcan.gc.ca/gps

36

4 NRCan stations contributing to the IGS network
Table 1: NRCan–AC Products

Product
Repro2em2wwwwd.sp3
em2wwwwd.clk
em2wwwwd.snx
em2wwww7.erp

Final (weekly)
emrwwwwd.sp3
emrwwwwd.clk
emrwwwwd.snx
emrwwww7.erp
emrwwww7.sum

Rapid (daily)
emrwwwwd.sp3
emrwwwwd.clk
emrwwwwd.erp

Ultra–Rapid (hourly)
emuwwwwd_hh.sp3
emuwwwwd_hh.clk
emuwwwwd_hh.erp

Description
GPS only• Time Span 1994–11–02 to 2014–03–29• Use of JPL’s GIPSY–OASIS II v6.3
• Daily orbits, ERP and SINEX• 5–min clocks• Submission for IGS repro2 combination
GPS only• Since 1994 and ongoing• Use of JPL0 s GIPSY–OASIS II v6.3
• Daily orbits, ERP and SINEX• 30–sec clocks• Weekly submission for IGS Final combination

GPS+GLONASS• Since 2011-Sep-11 and ongoing• Use of Bernese Software 5.0• Daily orbits and ERP• 30–sec clocks• Weekly submission for IGLOS Final combination• Station XYZ are constrained, similar to our Rapid solutions

GPS only• From July 1996 to 2011-05-21• Use of JPL0 s GIPSY-OASIS (various versions)• Orbits, 5-min clocks and ERP(30–sec clocks from 2006-Aug-27)• Daily submission for IGR combination
GPS only• From early 2000 to 2013–09–13, hour 06• Use of Bernese Software v5.0
• Orbits, 30–sec clocks and ERP (hourly)• Submission for IGU combination (4 times daily)
GPS+GLONASS• Since 2013-09-13, hour 12• Use of Bernese Software v5.0

37

NRCan Analysis Center• Orbits and ERP (hourly)• 30–sec GNSS clocks (every 3 hours)• 30–sec GPS-only clocks (every other hours)• Submission for IGUIGV combination (4 times daily)

Real–TimeGPS only• Since 2011–11–10• Custom software (HPGPS.C)• RTCM messages:– orbits & clocks:1060 (at Antenna Reference Point)– pseudorange biases: 1059
• Interval: 5 sec

alrt
eur2
reso
tukt

holm

invk
bcrk

iqal
whit

bake
yell

atli

nain
chur

sch2
stj2

kuuj

drao

stjo

flin

will
prds

sask

picl
dubo
winn

hrst

ross
mchn

pary

baie
escu
pper
she2
vald lpoc
hlfx
frdn
algo cags
nrc1
kngs
pwel

2015 Jan 27 20:51:05

Figure 1: NRCan Public GPS/GNSS Stations (CGS–CACS in blue, CGS–RACS in red and
GSC–WCDA in green).

38

4 NRCan stations contributing to the IGS network

Table 2: NRCan Multiple Monument GNSS Sites
Site

Stations

ALGO

algo, alg2, alg3

CHUR
DRAO
NRC1

chur, chu2
drao, dra3, dra4
nrc1, nr23

PRDS
STJO

prds, prd2, prd3
stjo, stj2, stj3

YELL

yell, yel2, yel3

Remarks
Secondary stations installed 2006–01–06
No alg2 data from 2012–12–21 to 2014–11–27
Secondary station installed 2010–08–02
Secondary stations installed 2013–10–29
Secondary stations installed 2008–12–23
nr23 data is private
Secondary stations installed 2014–07–09
Secondary stations installed 2009–07–02
stj3 jointly operated with CNES since 2013–07–10(now part of REGINA network)
Secondary stations installed 2008–11–14
yel2 jointly operated with CNES since 2013–07–10(now part of REGINA network)

Table 3: NRCan Station Upgrades in 2014
Station

Date

frdn
vald
chu2
flin
dubo
prd2
prd3
eur2
alg2

2014–01–31
2014–01–31
2014–02–18
2014–02–24
2014–02–26
2014–07–09
2014–07–09
2014–08–10
2014–11–27

RemarksTPS NETG3 to NET–G3A upgrade
TPS NETG3 to NET–G3A upgrade
TPS NETG3 to NET–G3A upgrade
TPS NETG3 to NET–G3A upgrade
TPS NETG3 to NET–G3A upgrade
New station installed at PRDS site
New station installed atPRDS site
Station upgraded from GPS–only to GNSS
Station repaired and brought back on–line after an extended outage.

39

NRCan Analysis Center

Acknowledgment
ESS Contribution number/Numéro de contribution du SST: 20140427
c Her Majesty the Queen in right of Canada 201540

ESA/ESOC Analysis Center
Technical Report 2014
T.A. Springer, F. Dilssner, W. Enderle, J. Feltens,
M. van Kints, I. Romero, E. Schoenemann, 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 2014.

2 Overview 2014
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 2014 day 140, from there on our normal Final products.
– 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 Analysis Center– 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 2014
– 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 calibrations 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 2014 were the following:• Upgrade of the ESA/ESOC GNSS Sensor Station network• Using a box–wing model for the GNSS satellites to a priori model the Solar andEarth Albedo radiation pressure

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. Furthermore, the
ESA products are one of the most complete GNSS products. In fact ESA/ESOC was thefirst 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 between subsequent solutions. Another uniquefeature is that our rapid products are, besides being one of the best, also one of the mosttimely available products. Normally our GNSS rapid products are available 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 significant difference.
The largest change, or rather improvement, we made in our processing in 2014 was that
we started using a box–wing model for the GNSS satellites to a priori model the Solar–
and Earth Albedo radiation pressure. The GNSS block type specific models were tested
thoroughly in the scope of our IGS reprocessing and the results were presented at the43

ESA Analysis Center
IGS workshop in 2014 (Springer et al. 2014). As significant improvements were observed
for most, if not all, estimated parameters it was decided to use the a priori box–wingmodeling for our IGS reprocessing efforts. After completing the reprocessing the box–
wing model usage was activated for the generation of all our routine IGS products in
April 2014. For our IGS final products this started with the products of GPS week
1789. As a consequence our agreement with the combined IGS orbit shows a significantly
degradation. Despite the fact that the quality of all our products, including our orbits,
improved, our orbits now deviate more from the combined IGS orbit product then they
did before. This may be explained by the fact that most of the IGS analysis centers do
not model the radiation pressure on the satellite adequately. The box–wing model gives
rise to very significant radial and cross-track orbital differences, see Fig. 1, which can not
be absorbed by the orbital parameters that are commonly estimated by the different IGS
ACs. The improvement of all our estimated parameters does clearly indicate that theseradial– and cross–track orbital differences are real and have to be taken into account. For2015 we are planning to invest significantly more time into this topic to further improve
our understanding and modeling capabilities regarding the different radiation pressures
acting on the GNSS satellites. With future GNSS satellites having a much higher area
to mass ratio the accurate modeling of the radiation pressure is becoming much more
important.

Figure 1: Radial (left) and Cross–track (right) differences between the original ESA final orbits
and the ES2 reprocessed orbits using the box–wing model.

44

2 Overview 2014

2.4 Multi–GNSS (MGEX)
We periodically analyze the data from the IGS Multi–GNSS Experiment (MGEX). At
the current stage we prefer the detailed analysis of the MGEX data over routine analysis. The orbit and clock products from two 16 day periods we analyzed in detail weremade available to the general public on the MGEX servers. The second 16 day period
period we analyzed, centralized GPS weeks 1783 and 1784 in March 2014, included all theactive GNSS satellites from all the GNSS constellations: GPS, GLONASS, GALILEO,
BEIDOU, and QZSS. This gives rise to solutions including a maximum of 74 activelytransmitting GNSS satellites in that period. We provided our orbit and clock products
for these two weeks which should enable multi–GNSS precise point positioning. The maininteresting features and challenges we have found so far in our MGEX analysis activities
were presented at the IGS workshop in June 2014 (Garcia-Serrano et al. 2014) and may
be summarized as:• Strong elevation dependent pattern in the BEIDOU pseudo range residuals for the
MEO satellites• Strong azimuthal dependent pattern in the GALILEO carrier phase residuals, clearlyan azimuthal ANTEX pattern needed• Severe inconsistency between the three GPS phase signals (L1, L2, and L5); a periodic effect with an amplitude of 50 mm clearly visible
2.4.1 Estimation of Satellite Antenna Phase Center Corrections for BEIDOU
In support of the IGS Multi–GNSS Experiment (MGEX), ESA/ESOC has put in significant effort to derive initial phase center corrections for the L–Band transmitter antenna
arrays aboard the Inclined Geosynchronous (IGSO) and Medium Earth Orbiting (MEO)
BEIDOU spacecraft (Dilssner et al. 2014). Almost one and one–half year of BEIDOU
triple–frequency (B1, B2, B3) measurement data – gathered between February 2013 andMay 2014 by 39 ground stations of the MGEX tracking network – was used to derive thesatellites0 antenna phase center offsets (PCOs) and variations (PCVs) for the ionosphere–
free linear combinations B1–B2 and B1–B3, respectively. Processing was carried out indaily batches using the most recent version of ESOC0 s multi–GNSS analysis software, theNavigation Package for Earth Observing Satellites (NAPEOS version 3.8). The parameterization of the PCVs was done in the conventional IGS–style, that is, using piece–wiselinear functions of the satellite nadir angle with 13 (MEO) and 9 (IGSO), respectively,
linear segments (Fig. 2). The estimates were found to agree to within 0.1–1 millimeter(PCVs) and 1–2 decimeter (z–PCOs) with independently–computed values from Wuhan
University0 s GNSS Research Center (J. Guo).
Applying these initial PCO/PCV corrections to the BEIDOU observables gives an improved performance compared to the currently recommended standard offset values (x =45

ESA Analysis Center

Figure 2: Satellite– and block–specific IGSO (top) and MEO (bottom) PCV estimates together
with error bars representing the formal errors from the variance–covariance matrix.
Results for IGSO–4/5 are not shown for reasons of clarity.

0.6 m, y =0.0 m, z =1.1 m). Initial comparisons of overlapping orbit solutions suggest thatthe orbit accuracy (3D–RMS) of the MEO spacecraft is substantially improved by morethan a third. The orbital component that benefits most from the improved phase centermodeling is the MEOs along–track component (see Fig. 3). Similar improvements against
the standard offset parameters were reported to us by GFZ (Z. Deng).

Figure 3: Day-to-day orbit overlap differences (RMS) computed for each MEO spacecraft over a
five–month processing period. The standard PCO–only solution is shown in red, theadvanced PCV–based solution in blue46

4 GNSS Sensor Station Upgrade

3 Reprocessing Activities
ESA/ESOC has participated in the first IGS reprocessing efforts (repro1) for the IGS
contribution to the realization of the International Terrestrial Reference Frame 2008 (ITRF
2008) and will also participate in the reprocessing for the ITRF2014. For this reprocessing
effort ESA will process all historic GNSS data of the IGS from 1994 to 2014. In thisreprocessing the years 1994 to 2008 are reprocessed using only GPS observations, butfrom 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 (label "es1"). The mostrecent ESA reprocessing products, currently based on the ITRF2008, are available fromour ftp server: ftp://dgn6.esoc.esa.int/igs/repro2 (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 weare 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.

4 GNSS Sensor Station Upgrade
ESA/ESOC contributes to the IGS the data of its GNSS station network, see Fig. 4, whichcurrently comprises 10 stations at ESA ESTRACK core/cooperation locations; Kourou(KOUR), Redu (REDU), Maspalomas (MAS1), Cebreros (CEBR), Villafranca (VILL),
Kiruna (KIRU), Malargue (MGUE), New Norcia (NNOR), Malindi (MAL2), as well 1
station installed in Tahiti (FAA1) in close cooperation with Meteo France. ESOC isproviding worldwide data from those 10 stations for all GNSS constellations as a result of
having completed the upgrade of the equipment at all the current installations over thelast few years. ESA/ESOC is as well focusing on the establishment of collaborations withthird parties to install new stations at various new locations around the world such as therecently complete Santa Maria Island in the Azores and Awarua in New Zealand, and soon
to come Japan, Malaysia and Dubai, as shown in the map above. Following the acquisitionof a large number of Septentrio PolarRx4 receivers and Septentrio Chokering MC antennas
plus 4 Leica AR25 rev.4 antennas in 2011–2012, now the entire ESA GNSS network now
operates these Septentrio receiver/antenna combinations, with the exception of MGUE,
MAL2, MAS1 and FAA1 where the Leica antennas are used. The Polar Rx4 Septentrio
receivers installed provide all observations for the GNSS constellations as available: GPS,GLONASS, GALILEO, QZSS, BEIDOU, SBAS, EGNOS, etc. As of mid–2013, ESOC
has been contributing with daily, hourly and high rate multi–GNSS RINEX 3 data to the47

ESA Analysis Center

Figure 4: ESA/ESOC GNSS Station Network.

MGEX effort. Also, since the beginning of 2013, ESOC has been providing NBS (NavBits)
data from this same set of stations to Eumetsat to support LEO satellite occultation
processing. The ESOC station network also supports the new RINEX 3 file naming as
promoted within the IGS for the mainstream adoption of the RINEX 3 format, as well as
retaining the distribution of the legacy GPS+Glonass RINEX 2.11 files.

5 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/ESOC0 s activities for the ionosphere in the frame of the IGS since2004 can briefly be summarized 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 et al. 2009 and Feltens et al. 2010)48

5 Ionosphere Modeling Activities• 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 ESOC0 s NAPEOS software
allowing for GPS+GLONASS based ionosphere estimation• Summer 2014: : Mathematical algorithms of a new 3D TEC and electron densities
assimilation approach worked out and coded as new NAPEOS component.
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 et al. 2009 and Feltens et al. 2010, working out recommendations for a new ionosphere monitoring system.
In summer 2013, the IONMON became an integral part of ESOC0 s NAPEOS software.
ESOC0 s actual ionosphere model development efforts are clearly 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, toan 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
was not yet dense enough to perform reliable and stable least squares fits. This was also oneof the results from the Iono Study conducted in 2009–10. The mathematical algorithms
for this new 3D assimilation approach were worked out and coded as new component of
NAPEOS in 2014. From its design, the assimilation scheme shall also enable NRT & RTprocessing and upgrade time resolutions down to several minutes, i.e. simple, fast androbust algorithms are required.

49

ESA Analysis Center

5.1 Actual / Future Activities
The 3D assimilation model code within NAPEOS has still to be tested. Once the new
assimilation approach in NAPEOS will be operational, ESOC0 s ionosphere processing
will be switched over from the current single layer modelling to this new 3D modelling
technique. This will then also concern ESOC0 s ionosphere products delivered to the IGS,
including new aspects such as 3D IONEX.
A follow-up study to the Iono Study of 2009–10 is currently under planning.
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, other ionosphere-related activities are ongoing at
ESOC:• Establishment of a new model for the plasmasphere in a cooperative effort with
the German Aerospace Center (DLR) in Neustrelitz, Germany. This plasmaspheremodel will then complement the new 3D assimilation approach.
• Establishment of an ionospheric & tropospheric media calibration service to be operationally used by the ESOC Flight Dynamics Department.
• Routine contributions to ESA0 s Space Situational Awareness (SSA) service – spaceweather
part.

6 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 2014.
Practically 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 accurate, 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
is also 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, 2009. Available at
ftp://dgn6.esoc.esa.int/napeos

50References
Feltens, J., M. Angling, N. Jakowsk, Ch. 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-OPSGN, Iss. 1/0, 26/06/2009, 2009.
Feltens, J., M. Angling, N. Jackson–Booth, N. Jakowsk, M. Hoque, Ch. Mayer,
M. Hernández-Pajares, A. García-Rigo, R. Orús-Perez, A. Aragón-Ange, andJ. Miguel Juan Zornoza. Recommendations for a New European Ionosphere Monitoring System. DOPS-SYS-RP-5001-OPS-GN Iss. 1/0, 20/01/2010, 2010.
Dilssner, F., T. Springer, E. Schönemann, and W. Enderle. Estimation of Satellite Antenna
Phase Center Corrections for BEIDOU. IGS Workshop 2014, June 23–27, Pasadena
USA, 2014.
Garcia-Serrano, C., L. Agrotis, F. Dilssner, J. Feltens, M. van Kints, I. Romero,
T. Springer, and W. Enderle. The ESA/ESOC Analysis Center Progress and Improvements. IGS Workshop 2014, June 23-27, Pasadena USA, 2014.
T. Springer, M. Otten, C. Flohrer, F. Pereira, F. Gini, and W. Enderle. GNSS Satellite
Orbit Modeling at ESOC. IGS Workshop 2014, June 23–27, Pasadena USA, 2014.

51

GFZ Analysis Center
Technical Report 2014
M. Fritsche, Z. Deng, M. Ge, T. Nischan,
M. Uhlemann, G. Beeskow, A. Brandt,
M. Bradke, M. Ramatschi
Helmholtz-Zentrum Potsdam
Deutsches GeoForschungsZentrum (GFZ)
Department 1: Geodäsie und Fernerkundung
Telegrafenberg A 17, 14473 Potsdam, Germany
E-mail: mathias.fritsche@gfz-potsdam.de

1 SummaryDuring 2014 the standard IGS product generation was continued with minor changes in theprocessing software EPOS–8. The GNSS observation modeling was adapted to conformto the GFZ repro–2 (2nd IGS Reprocessing campaign) settings for IGS Final productgeneration.
End of 2014 the repro–2 processing for IGS (GF2) and TIGA (GT2) was nearly finished.
Newly re-runs for GF2 and GT2 became necessary, because a preliminary SINEX combination of repro–2 submissions revealed systematic problems for GFZ SINEX submissions
related to station network scale and length of day (LOD) estimates.
A routine multi–GNSS processing including GPS, GLONASS, BeiDou and Galileo has
been set up similar to the IGS Rapid processing scheme.
At the end of February 2014, Dr. Gerd Gend retired from GFZ and such also resigned
as head of the IGS analysis center. We would like to take the opportunity to express
our sincere appreciation and gratitude to him for his longstanding efforts within the IGS
community but also for his collegial spirit over many years.

52

3 Operational data processing and latest changes

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

3 Operational data processing and latest changes
The EPOS–8 processing software is following the IERS Conventions 2010 (Petit andLuzum 2010). The station network used in the processing is shown in Fig. 1. For the
IGS Final, Rapid and Ultra Rapid about 200, 110, and 95 sites are used, respectively.
The sites providing GLONASS observation data is steadily increasing. Some processing
related information is given in Tab. 2.
Recent changes in the processing strategy are listed in Tab. 3. Major changes in thestrategy for observation modeling have been applied in order to have identical strategies
for repro–2 and operational products. From the IGS Final combination it was noticed,that due to switching to the repro–2 modeling standards a significant bias was introducedin length of day (LOD) estimates (see Fig. 2). The root cause of this LOD bias was
identified to be a misused C20 –term in the gravity field model. Instead of applying theC20 –term delivered along with the EGM2008 gravity model, the corresponding value listed
in Tab. 6.2 of the IERS Conventions 2010 was introduced. Figure 3 shows LOD differenceswith respect to the IGS Final LOD time series when applying different gravity field models.
The jump of about 0.6 ms/d which is also obvious from the IGS Final combination resultsin Fig. 2 can clearly be attributed to the application of the inconsistent C20 –term.
Table 1: List of products provided by GFZ AC
Final(GLONASS since week 1579)

gfzWWWWD.sp3
gfzWWWWD.clk
gfzWWWWD.snx
gfzWWWW7.erp
gfzWWWW7.sum
gfzWWWWD.tro

Daily orbits for GPS/GLONASS satellites
5–min clocks for stations and 30–sec clocks for GPS/GLONASS satellites
Daily SINEX files
Earth rotation parameters
Summary file including Inter-Frequency Code Biases (IFB) for GLONASS
1–hour tropospheric Zenith Path Delay (ZPD) estimates

Rapid(GLONASS since week 1579)

gfzWWWWD.sp3
gfzWWWWD.clk
gfzWWWWD.erp

Daily orbits for GPS/GLONASS satellites
5–min clocks for stations and GPS/GLONASS satellites
Daily Earth rotation parametersUltra(every 3 hours; provided to IGS every 6 hours; GLONASS since week 1603)

gfuWWWWD.sp3
gfzWWWWD.erp

Adjusted and predicted orbits for GPS/GLONASS satellites
Earth rotation parameters

53

GFZ Analysis Center

Table 2: Recent Processing changes
IGS
Product
Ultra
Rapid
Final

# Sites95
110
200# Sites with
with GLONASS
65
80
115

Duration [h]
≈1
≈2
≈4

""

GPS only

GPS + GLO

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

Table 3: Recent Processing changes
Date2014-06-05
2014-09-03

IGS
w1795
w1807

IGR/IGUw1795.4—

2014-10-15
2014-12-02

w1812
w1820

w1814.4
w1821.3

ChangeMeta data retrieval from SEMISYS
2nd order ionosphere correction applied
Troposphere modeling based on VMF–1 mapping function
Switch to gravity model EGM2008 and ocean tide model FES2004
Bug fix C20 term in gravity model EGM2008

For the reprocessing GF2/GT2 submissions following changes were implemented:
Bug fix C20 –term in gravity model EGM2008
Bug fix 2nd-order ionospheric correction calculation54

3 Operational data processing and latest changes

LOD Difference [ms/day]AC Final LOD Differences with IGS Final
0.0

COD

-0.2

EMR

-0.4

ESA

-0.6

GFZ

-0.8

GRG

-1.0

JPL

-1.2

MIT

-1.4

NGS

-1.6

SIO

-1.8

IRF

-2.0

IGR

1760

1770

1780

1790
1800
Time [GPS weeks]

1810

1820

1830
NOAA NGS, 24.01.2015 19:19 (GMT)∆ LOD [µs/d]

Figure 2: Differences in length of day (LOD) of Analysis Center submissions with respect to IGS
Final combined LOD product. Note the jumps for GFZ solution at GPS weeks 1812and 1820.

700
600
500
400
300
200
100
0
−100
−200
−300
−400

egm2008_C20 IERS − igs
eigen − igs
egm2008_C20 EGM − igs

2014−Aug−31

2014−Sep−01

2014−Sep−02

2014−Sep−03

2014−Sep−04

2014−Sep−05

2014−Sep−06

Figure 3: Differences in length of day (LOD) estimates with respect to IGS Final combined
LOD product (igs) based on different internal GFZ solutions. eigen: EIGEN_GL04C
gravity model, egm2008_C20 IERS : EGM2008 gravity model but with supplemented
IERS2010 C20 -term (from Tab. 6.2 in Petit and Luzum 2010); egm2008_C20 EGM :EGM2008 gravity model.

55

GFZ Analysis Center

IGS (307)

TIGA_only (487)

Figure 4: Global distribution of the reprocessed GPS stations for IGS (GF2) and TIGA-only(GT2) solutions.

4 Reprocessing activities
GFZ is contributing to the 2nd IGS and TIGA Reprocessing Campaigns. For the IGS/TIGA
reprocessing the GPS data from a globally tracking network of 307/794 stations has been
included (Deng et al. 2014a, b). The GF2 time series extend to end of 2014 (GPS week1824) whereas GT2 time series are provided until end of 2012 (GPS week 1720). The
distribution of the GPS stations involved in GF2/GT2 is shown in Fig. 4.
Initial GF2 and GT2 reprocessing solutions were also affected by using an improper C20 –term in the EGM2008 gravity model as described in section 3. Accordingly, both solutions
have been re-generated and re-submitted in January 2015.

5 Metadata Management Tool SEMISYSFor the precise analysis of GNSS observation data a variety of metadata from different
sources is required. In particular, validated integrity of station and satellite related metadata information is required in order to deliver consistent products. Station and satellite
meta information is usually distributed and maintained by ASCII based files. To ease
the handling of metadata and to improve the trackability of changes to meta information,
the Operational Data Center (ODC) group of the GFZ developed a Sensor Meta Information System (SEMISYS) for the central, format independent and validated storage ofstation and satellite metadata based upon a relational database (Bradke et al. 2014). Figure 5 provides a schematic overview on the basic system design of SEMISYS and relations
according to the data flow.
Following processing related meta information is currently stored in SEMISYS:

56

Batch Mode – File output
 Generation of processing files
 Common used: IGS site logs for each project SNX files for each project Merged ANTEX file
 GFZ internal:
 NANU/NAGU sum file
 Satellite parameters file
 Coordinate and OLOAD file
 Station selection, ant/rec file …

BackupsDaily cronjob

PostgreSQL 9.2
Database

Web-based Graphical User Interface (GUI) PHP 5.3 based multi-user system
 Project and role based protected access to metadata Automatic generation of forms and data validation (incl. Site
Log Manager)
 Interactive map generation by different criteria based on a
JavaScript map API
 Export of meta data (IGS site logs, SNX, tables)

SEMISYS
Modular core application

Email
Changelog

Batch Mode – Monitoring Daily automatic monitoring of: IGS site logs (IGS, MGEX, etc.)
 ANTEX (IGS, EPN) NANU/NAGU (GPS, GLO, GAL)
 Ocean loading values(OLOAD)
 Perl 5.12 based cronjobs

EmailChangelog

External FTP server
Heterogenic sources

ApacheHTTP server

6 Multi-GNSS data processing

http://semisys.gfz-potsdam.de

GFZ FTP server
ftp://ftp.gfz-potsdam.de/GNSSGFZ EPOS.P8
GNSS analysis
softwareFigure 5: Basic system design of the Sensor Meta Information System (SEMISYS), data flow
and client/server communication.

– station meta information extracted from IGS site logs
– hardware meta information (receiver, antenna, radome)– satellite parameter for GPS, GLONASS, Galileo, BeiDou, QZSS and SBAS
– notice advisories from GPS, GLONASS, and Galileo (NANU, NAGU)– antenna phase center model (ANTEX) from different sources (GFZ, IGS, EPN)
– initial station coordinates– ocean loading displacements (retrieved from http://holt.oso.chalmers.se/loading)
GFZ has started to use SEMISYS in order to regularly generate up–to–date metadata
related processing files required to run the EPOS–8 software environment. In principle,
also metadata files in different file formats used by other processing software packages
could be generated and provided to external users.

6 Multi-GNSS data processing
Since end of 2012 with a total of 14 operational satellites, BeiDou constitutes the thirdsatellite navigation system next to GPS and GLONASS that offers a fully operationalnavigation service for China and surrounding regions. Tracking of the BeiDou satellites
is supported by a subset of stations from the MGEX network. Based on that continuous
observation data of satellites in geostationary orbit (GEO) and inclined geosynchronous57

GFZ Analysis Center
orbit (IGSO) can be provides as well as partial tracking of the four satellites in medium
Earth orbit (MEO) is enabled.
At GFZ an upgraded version of EPOS.P8 software is used for processing dual-frequency
GPS+BDS data. Ambiguity–fixing was also set up for BeiDou IGSO and MEO typesatellites. The ionosphere–free linear combination of B1 (1561.098 MHz) and B2 (1207.140
MHz) frequencies is applied for estimation of satellite orbits, clocks, and other relevant
parameters. The a priori BeiDou orbits are taken from the broadcast navigation message
files, which are available from the MGEX network. More details are described in Denget al. 2014c, d.
Since 28th January, 2014 GFZ generates IGR-like GPS+BeiDou orbits and 5 min clock
products routinely. For the analysis, GPS and BeiDou data of the MGEX and IGS networks is used. Starting with 8th July, 2014 (doy 200) besides GPS and BeiDou, also
GLONASS and GALILEO are included in the analysis. Table 4 gives an overview on thenumber satellites included per system and the frequencies used for product generation.
Associated final products are provided as GBM products (ftp://ftp.gfz-potsdam.de/pub/GNSS/products/mgex).
In order to check the quality of the GBM orbits the median daily RMS of orbit differenceswith respect to GFZ rapid orbit GFR are computed (doy 200 to 250 in 2014, Deng et al.
2014e). Statistical results are shown in Fig. 6. Looking at GPS, the RMS values for mostof the satellites are on a level of about 1.5 cm. The RMS for GLONASS satellites is on theorder of 3 cm. Since the GFR orbit has an accuracy of approximately 2.5 cm, 3.0 cm for
GPS and GLONASS, respectively, the accuracy of the GBM GPS and GLONASS orbits
are assumed to be on a similar order of magnitude.
Besides the orbit differences with respect to GFR, the RMS of the differences from overlapping orbit positions (4 hours interval) has been evaluated. Figure 7 shows the daily
median RMS of the orbit overlaps for each satellite. Corresponding RMS values are below
10 cm for most of the GPS satellites, while they vary between 10 and 20 cm for GLONASS.
For GALILEO satellites, we find an RMS of about 10 cm. For BeiDou, there are three different types of orbits: GEO, IGSO and MEO. Because of the weak observation geometry
and the lack of orbit change with respect to the ground tracking station network, GEO
satellites reveal the largest RMS value of 1 to 2 meter. The IGSO and MEO satellites
have RMS values of 40 cm and 12 cm, respectively.
Fortunately, all BeiDou and Galileo satellites are equipped with laser reflectors. An independent validation of the microwave-based satellite orbits can be performed via SLR
measurements (mainly the radial component). Figure 8 shows the resulting mean bias andstandard deviation for different satellite types which indicate the achieved orbit accuracies
for that satellites (Uhlemann et al. 2014) currently observed by the International Laser
Ranging Service.

58

6 Multi-GNSS data processing
Table 4: Used observation types and number of satellites in the multi-GNSS data processing
Satellite SystemGPS
GLONASS
BeiDouGalileoMedian orbit difference RMS [cm]GPS# of Satellites

Observation Types

31
24
14
3

L1/L2
L1/L2
B1/B2
E1/E5aGLONASS

5

3
2
1
0

Figure 6: Daily
median
RMS
[cm]
of
orbit
differences
between(GPS+GLONASS+BeiDou+Galileo) and GFR (GFZ IGS Rapid) solution.

180

4 hour overlap RMS [cm]GPS

GLONASSGALILEO

BeiDou

GBM

GEO

IGSO
MEO

100

40
20
10
0

Figure 7: Daily median RMS [cm] of the differences from overlapping orbit positions (4 hours
interval).

59

GFZ Analysis Center

0.4

Bias (colored)

SLR residuals [m]Stdv (grey)

0.2
0.0
−0.2
−0.4
MEO

IGSO

GEO

E11 E12 E19 C11 C08 C10 C01
GAL

BDS

Figure 8: SLR residual statistics. The bias (colored) and STDV (grey) are given for individual
Galileo and BeiDou satellites.

60References

References
Bradke, M., T. Nischan, and M. Ramatschi. GFZ Sensor Meta Information System – Next
generation IGS metadata handling. IGS workshop 2014, Pasadena USA, 23–27 June,2014.
Deng, Z., M. Ge, M. Uhlemann, and Q. Zhao. Precise orbit determination of BeiDou
Satellites at GFZ. IGS workshop 2014, Pasadena USA, 23–27 June, 2014a.
Deng Z., G. Gendt, and T. Schöne. TIGA Reprocessing at GFZ. IGS Workshop 2014,
Pasadena USA, 23–27 June, 2014b.
Deng Z., G. Gendt, T. Schöne, T. Nischan, and M. Fritsche. IGS 2nd Reprocessing at
GFZ. IGS Workshop 2014, Pasadena USA, 23–27 June, 2014c.
Deng Z., M. Uhlemann, G. Dick, M. Fritsche, and J. Wickert. Multi-GNSS Processing
at GFZ and Tropospheric Products. COST ES1206 WG meeting, Varna Bulgaria,
September, 2014d.
Deng Z., Q. Zhao, T. Springer, L. Prange, and M. Uhlemann. Orbit and Clock Determination – BeiDou. IGS workshop 2014, Pasadena USA, 23–27 June, 2014e.
Petit, G. and B. Luzum (eds). IERS Conventions (2010). Number 36. Verlag des Bundesamtes für Kartographie und Geodäsie, Frankfurt am Main, Germany, 2010. ISBN3-89888-989-6. IERS Technical Note No. 36.
Uhlemann, M ., Z. Deng, and M. Fritsche. Multi-GNSS Orbit and Clock Products of the
GFZ Analysis Centre. Geodätische Woche, Berlin Germany, 7–9 October, 2014.

61

CNES–CLS Analysis Center
Technical Report 2014
S. Loyer1 , F. Mercier2 , F. Perosanz2 ,H. Capdeville1 , A. Mezerette1 , L. Lestarquit2
1
2

Collecte Localisation Satellites
31520 Ramonville Saint Agne, France
E–mail: igs-ac@cls.fr
Centre National d’Etudes Spatiales
31400 Toulouse, France

1 Introduction
The GINS CNES/GRGS software (Marty et al. 2011) is routinely operated in order todeliver to IGS, final GPS and GLONASS products. We process zero–difference GNSS
observations and the details of our strategy are described in Loyer et al. 2012. Moreinformation on our AC activity can also be found at: www.igsac-cnes.cls.fr.
In 2014, the activities were dominated by our contribution to REPRO2 campaign.

2 Operational products delivery
Since GPS week 1786 the GRG satellite clock solution is aligned using a combinationof the best stations clocks. This significantly improves the Allan variance of each daily
GRG clock solution. There is no specific processing to achieve a correct behavior of theirreference between successive days. This improves significantly the RMS of GRG clocks
relatively to the combined solution as shown on Fig. 1.

62

3 Participation to REPRO2 campaign

Figure 1: GRG GPS satellites clock solutions RMS improvement after week 1786 (from IGS
Analysis Center Coordinator).

3 Participation to REPRO2 campaign
As we became an Analysis Center in 05/2010, REPRO2 was in fact our first experience ina massive reprocessing campaign and has proven to be a heavy but instructive experiencefor our group. In March 2014, we delivered 18348 files including GPS products starting
01/01/1998 and GLONASS products starting 01/01/2009.

3.1 Standards and models
Most of the standards we used followed the recommendations of the Analysis Center
Coordinator. The main specificities of our processing were the use of the Eigen6S2 Time
Variable Gravity (TVG) field model (up to degree and order 12), ocean tide loading
displacement derived from FESS2012 model, second order ionospheric corrections and
GPT2/VMF1 tropospheric model.
Dedicated tests have been realized in order to quantify the impact of TVG model on IGS
products (Loyer et al. 2014). Results are summarized in Tab. 1.
The main conclusion was that the impact of TVG on IGS products is sufficiently high toconsider today these effects (especially on the EOP), but small enough that our solution
could be combined to other ACs’s.
63

CNES Analysis Center
Table 1: Impact of gravity field variations on GNSS products
Product

ImpactDetailResiduals<0.1 mm on phase
un–differenced observations

Not significant

Orbit

RMS 3D ∼ 4 mm
SSA ∼ 0.3 mm

Below todays ACs differences

Orbit frametranslations±4 mm

Dominated by seasonal variations

EOP

Few tens of uas in xp/yp

Order of magnitude of IGS ACs discrepancies
LOD differences linked to C20 differences

Stations
Coordinates

East/North: <1 mm RMS
Up : 2.5 − 3 mm RMS

Dominated by seasonal variations

Figure 2: WRMS of station coordinates differences between static and TVG field model solutions(from P. Rebischung, IGN).

In addition, in the framework of the ITRF14 realization, a comparison of GR2 station
coordinate series with a preliminary combination from all contributing ACs have beenkindly provided by IERS. A spectral analysis of the coordinate differences clearly showsan annual signal of 2−6 mm affecting the Up and North component which was questioning
our participation to the combined coordinate solution. After intensive investigations we
discovered that we used a bad parameterization of the GPT2/VMF1 tropospheric model.
We hope that an a posteriori correction of the series will be possible.
64

3 Participation to REPRO2 campaign

3.2 Zero difference ambiguity fixing
Fixing zero–difference ambiguity before 2004 has proven to be an unexpected challenge.
This corresponds to the times when cross–correlated receivers were dominating the IGS
network. After intensive investigations, we came to the conclusion that P1–C1 biases
provided by the IGS were not compatible with our processing strategy in the case of
ROGUE8000 and Trimble receivers. Mercier et al. 2014 has demonstrated that a set of
biases per receiver “family” can be identified and would help in fixing ambiguities.

3.3 P1–C1 DCB
Discrepancies in the GPS P1–C1 DCB have been observed according to the receiver makeand manufacturer. In particular, receivers that produces both the P1 and C1 observable
have a similar behavior, while other type of receiver and in particular Trimble receiver havea different P1–C1 DCB. The difference is satellite dependent and can reach up to 40 cm (seeFig. 3), and therefore the traditional approach in geodetic processing to separate biases
into a purely receiver dependent and a purely satellite dependent part is not accurate andwe are working on an improved model that will take into account this observation.
Moreover, high gain antenna measurements of a few GPS satellites have been made at
CNES in experiments made as preparatory work for the future GNSS signal observatory(DCT/RF/SR). These measurements have revealed signal distortion specific to each satellite that closely explains the observed difference between receiver types. Making the link
between the biases determined from the high gain antenna measurements and the observed
geodetic receiver bias would allow to better monitor and correct the signal biases. Thiscan improve the accuracy of PPP and the success rate of i–PPP positioning.
We are currently working on a new modeling of GNSS signal biases that could include
measurements made with high gain antenna

Figure 3: P1–C1 difference with IGS P1C1 DCB files according to receiver make.

65

CNES Analysis Center

4 Contribution to MGEX
Our main short time objective is to provide the IGS with fully hybridized GPS + GLONASS+ Galileo final products. To reach this goal several software implementations have beenrealized and are routinely tested in parallel to our operational activities. The major improvements include the capabilities to:• Mix RINEX2 and 3 files• Choose and manage the frequencies used for the processing (and the pre–processing)• Include automatically new MGEX stations and new satellites• Consider PCO/PCV and attitude laws provided by MGEX working group
Preliminary results derived from a dual frequency simultaneous processing of respectively
31, 23 and 3, GPS, GLONASS and Galileo satellites are very encouraging.

Reference
Lestarquit, L. and F. Mercier. P1–C1 DCB determination using a high gain antenna
coupled to the LCI method. Receiver type impact. IGS Workshop 2014, Pasadena
California, June 23–27, 2014.
Loyer, S., F. Perosanz, F. Mercier, and H. Capdeville. 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
Loyer, S., J-M. Lemoine, and F. Perosanz. Time Variable Gravity (TVG). IGS Workshop
2014, Pasadena California, June 23–27, 2014.
Loyer, S., F. Mercier, H. Capdeville, A. Mezerette, and F. Perosanz. GR2 Reprocessing
from CNES/CLS IGS Analysis Center: specificities and results. IGS Workshop 2014,
Pasadena California, June 23–27, 2014.
Marty J.C., S. Loyer, F. Perosanz, F. Mercier, G. Bracher, B. Legresy, L. Portier,
H. Capdeville, F. Fund, J.M. Lemoine, R. Biancal. GINS : the CNES/GRGS GNSS
scientific software. 3rd International Colloquium Scientific and Fundamental Aspectsof the Galileo Programme, ESA Proceedings WPP326, 31 August – 2 September 2011,
Copenhagen, Denmark, 2011.
Mercier, F., F. Perosanz, S. Loyer, and H. Capdeville. Wide–Lane ambiguity fixing anomalies observed in Repro2 solutions. IGS Workshop 2014, Pasadena California, June
23–27, 2014.

66

JPL Analysis Center
Technical Report 2014
S. Desai, W. Bertiger, M. Garcia-Fernandez,
B. Haines, D. Kuang, C. Selle, A. Sibois,
A. Sibthorpe, 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 2014, the Jet Propulsion Laboratory (JPL) continued to serve as an Analysis Center(AC) for the International GNSS Service (IGS). We contributed operational and reprocessed orbit and clock solutions for the GPS satellites; position, clock and tropospheresolutions 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 2014, including
our contribution to the second IGS reprocessing campaign (Repro 2).
Table 1 summarizes our contributions to the IGS Rapid and Final products. All of ourcontributions are based upon daily solutions centered at noon and spanning 30–hour. Eachof our daily solutions is determined independently from neighboring solutions, namely
without applying any constraints between solutions. Of note, JPL began to operationallydeliver high–rate (30–second) Final GPS clock products to the IGS starting October 26,
2014.
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

67

JPL Analysis Center
Table 1: JPL AC Contributions to IGS Rapid and Final Products
Product

Description

Rapid/Final

jplWWWWd.sp3
jplWWWWd.clk
jplWWWWd.clk_30s
jplWWWWd.tro
jplWWWWd.erp
jplWWWWd.yaw
jplWWWWd.snx
jplWWWW7.sum

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

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

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 ourcontributions to the IGS. Starting GPS week 1816 (October 26, 2014), we transitioned
our operational IGS contributions to use GIPSY/OASIS version 6.3 and our Repro 2 processing configuration. Prior to this date we used GIPSY/OASIS version 6.2 to generate
our products. A complete description of our current operational processing approach,also used for Repro 2, can be found at: http://igscb.jpl.nasa.gov/igscb/center/
analysis/jpl.acn. 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).
Our Repro 2 processing approach includes the following most notable improvements:• Application of second order ionospheric corrections (Garcia-Fernandez et al. 2013).

• Revised empirical solar radiation pressure model named GSPM13 (Sibois et al. 2014).
• 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.

Each of the changes were incrementally tested using a 1–year test period before they were
accepted into our processing configuration.
68

5 Acknowledgments

3 Contribution to IGS "Repro 2" Reprocessing Campaign
At JPL we used our Repro 2 processed configuration to generate Final products (seeTab. 1) for GPS week 658 (August 16, 1992) onward (Desai et al. 2014). Our Repro
2 submission to the IGS was completely delivered on November 7, 2014 and included
products spanning GPS weeks 729–1773 (December 25, 1993 to October 25, 2014). Our
Repro 2 products for the full period, GPS week 658 onward, are available at the ftp site
indicated below. As mentioned above, we then transitioned our operational submissions
to the same Repro 2 processing configuration for October 26, 2014 onward. The full set of
reprocessed and operational products, with a consistent Repro 2 approach, are available
at:
1. ftp://sideshow.jpl.nasa.gov/pub/jpligsac in IGS formats, and2. ftp://sideshow.jpl.nasa.gov/pub/JPL_GPS_Products/Final in GIPSY formats.
High-rate (30–second) GPS clock products were delivered to the IGS for the period May
5, 2000 onward, and are also available in native GIPSY format for that period. Also of
note, daily JPL SINEX files are now available for our complete reprocessing period, GPS
week 658 onward. Furthermore, our reprocessed products include our so–called “wide-lanephase 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.
Figure 1 shows that the most significant improvements to the JPL orbit products from
Repro 2 relative to our products from the first IGS reprocessing campaign (Repro 1) arefor 2003 onward. Meanwhile, the most significant improvements to the clock products areprior to 2002. These clock precision improvements are a result of the significant efforts
made towards identifying and using stable reference clock sites in these earlier years. For
the recent years, 2003–2011, orbit and clock precision is improved by 10–30 percent.

4 Future WorkIn 2015, JPL will continue to submit operational Rapid and Final GPS products to the
IGS using our Repro 2 processing configuration.

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.
c 2015 California Institute of Technology. Government sponsorship acknowledged.
69

JPL Analysis Center

3-D Orbit Precision (cm)12
Repro 1
Repro 2

10
8
6
4
2
0
1992

1996

2000

2004
Year

2008

2012

Figure 1: Precision of GPS orbit solutions from JPL’s contributions to the IGS Repro 1 and 2
campaigns. Precision is measured using the annual median of daily RMS of differences
during the middle 5 hours of the 6–hour overlapping period of adjacent–day solutions.

Clock Precision (picosec)

350
300
Repro 1
Repro 2

250
200
150
100
50
0
1992

1996

2000

2004
Year

2008

2012

Figure 2: Precision of GPS clock solutions from JPL’s contributions to the IGS Repro 1 and 2
campaigns. Precision is measured using the annual median of daily RMS of differences
during the middle 5 hours of the 6–hour overlapping period of adjacent–day solutions.
The Repro 1 clock precision for the periods 1996–2001 is 350–1200 picoseconds, and istherefore above the scale of the plot.

70References

References
Bertiger, W., S. Desai, B. Haines, N. Harvey, A. Moore, S. Owen, and J. Weiss (2010),
Single receiver phase ambiguity resolution with GPS data, J. Geodesy, 84(5), 327–337,
doi:10.1007/s00190-010-0371-9.
Desai, S. D., W. Bertiger, M. Garcia-Fernandez, B. Haines, N. Harvey, C. Selle, A. Sibois,
A. Sibthorpe, and J. P. Weiss (2014), JPL’s reanalysis of historical GPS data for thesecond IGS reanalysis campaign, Fall AGU, San Francisco, CA, December 15–19.
Garcia–Fernandez, M., S. D. Desai, M. D. Butala, and A. Komjathy (2013), Evaluationof different approaches to modeling the second-order ionosphere delay on GPS measurements, J. Geophys. Res., 118(12), 7864-7873, doi:10.1002/2013JA019356.
Lagler, K., M. Schindelegger, J. Bohm, H. Krasna, and T. Nilsson (2013), GPT2: Empirical slant delay model for radio space geodetic techniques, Geophys. Res. Lett., 40(6),1069–1073, doi:10.1002/grl.50288.
Lyard, F., F. Lefevre, T. Letellier, and O. Francis, Modeling the global ocean tides:
Insights from FES2004 (2006), Ocean Dyn., 56(5–6), 394–415, doi:10.1007/s10236006-0086-x.
Ray, R. D., Precise comparisons of bottom-pressure and altimetric ocean tides (2013),
J. Geophys. Res., 118, 4570–4584, doi:10.1002/jgrc.20336.
Sibois, A., C. Selle, S. Desai, A. Sibthorpe, and J. Weiss (2014), An update empiricalmodel for solar radiation pressure forces acting on GPS satellites, IGS Workshop,
Pasadena, CA, June 23–27.
Sibthorpe, A., W. Bertiger, S. D. Desai, B. Haines, N. Harvey, and J. P. Weiss (2011), An
evaluation of solar radiation pressure strategies for the GPS constellations, J. Geodesy,
85(8), 505-517, doi:10.1007/s00190-011-0450-6.
Weiss, J. P., W. Bertiger, S. D. Desai, B. J. Haines, and C. M. Lane (2010), Near real time
GPS orbit determination: Strategies, performance, and applications to OSTM/Jason2, Adv. Astronaut. Sci., 137, 439–452.

71

USNO Analysis Center
Technical Report 2014
C. Hackman, S. M. Byram, V. J. Slabinski,
J. C. Tracey, J. R. Rohde
United States Naval Observatory
3450 Massachusetts Avenue Northwest
Washington DC 20392, USA
Tel: +1–202–762–1444
E–mail: christine.hackman@usno.navy.mil

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 directs AC activities, chairs the
IGS TWG, and serves on the IGS Governing Board. Dr. Sharyl Byram oversees productionof 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.

72

2 Product Performance in 2014
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 positioning (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
Service/Prediction Center uses UTGPS to improve post–processed and predicted estimatesof 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 Product Performance in 2014
Figures 1–4 show the 2014 performance of USNO rapid and ultra–rapid GPS products,
with summary statistics given in Tab. 1. USNO rapid orbits had a median weighted RMS(WRMS) of 17 mm with respect to (wrt) the IGS rapid combined orbits. The USNO ultra–
rapid orbits had median WRMSs of 19 mm (24–h post–processed segment) and 38 mm (6–hpredict) wrt the IGS rapid combined orbits. These values are largely the same as the 2013
values (16, 19 and 38 mm).
USNO rapid (post–processed) and ultra–rapid 6–h predicted clocks had median 162 ps
and 1603 ps RMSs wrt IGS combined rapid clocks, compared to 146 and 1902 ps in 2013.
Though by this measure the rapid clocks lost 11% precision, the ultra–rapid clocks gained
16 %.
USNO rapid polar motion estimates had (x, y) 186 and 108 micro arc sec RMS differences
wrt IGS rapid combined values. USNO ultra–rapid polar motion estimates differed (RMS;x, y) from IGS rapid combined values by 105 and 110 micro arc sec for the 24–h post–processed segment. The USNO ultra–rapid 24–h predict–segment values differed (RMS;x, y) from the IGS rapid combined values by 338 and 278 micro arc sec. While the rapid
and ultra–rapid post–processed estimate precision was slightly worse than the 2013 values(130, 99; 105, 60), the ultra–rapid prediction precision remained virtually the same as the2013 value (338, 278).
The USNO AC began incorporating measurements from the Russian GLONASS GNSS
into processing in 2011 (Byram and Hackman 2012a, b) and has been computing a fullset of test rapid and ultra–rapid combined GPS+GLONASS products since 2012. The
1Prior to 2009, the rapid products were computed using Jet Propulsion Laboratory (JPL) GPS Inferred
Positioning System (GIPSY ) (Webb and Zumberge 1997).
2International Earth Rotation and Reference Systems Service

73

USNO Analysis Center

WRMS, USNO GPS Orbits WRT IGS Rapid Combined Orbits
150
Median (mm):rapid: 17
ultra, past: 19
ultra, pred: 38

mm

100

50

0
0

50

100

150

200
250
day of year, 2014

ultra, predultra, past

300

350

400

rapid

Figure 1: Weighted RMS of USNO GPS orbit estimates with respect to IGS Rapid Combination,
2014. “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.
RMS, USNO GPS Clock Estimates WRT IGS Rapid Combined Clocks
6000
Median (ps):rapid: 162
ultra, pred: 1603

ps

4000

2000

0
0

50

100

150

200
250
day of year, 2014
ultra, pred

300

350

400

rapid

Figure 2: RMS of USNO GPS rapid clock estimates and ultra–rapid clock predictions with respect to IGS Rapid Combination, 2014.

74

2 Product Performance in 2014

USNO Rapid Polar Motion WRT IGS Rapid Combined
500
RMS (x, y, micro arc sec): 186, 108
400
300

micro arc sec

200
100
0
-100
-200
-300
-400
-500
0

50

100

150

200
250
day of year 2014

dx, rapid

300

350

400

dy, rapid

Figure 3: USNO rapid polar motion estimates minus IGS Rapid Combination values, 2014.

USNO Ultra-Rapid Polar Motion WRT IGS Rapid Combined1000
RMS (x, y, micro arc sec): past: 105, 110; pred: 338, 278

micro arc sec

500

0

-500

-1000
0

50

100

150

200
250
day of year 2014

dx, pastdy, past

dx, pred

300

350

400

dy, pred

Figure 4: USNO ultra–rapid polar motion estimates minus IGS Rapid Combination values, 2014.

75

USNO Analysis Center
Table 1: Precision of USNO Rapid and Ultra–Rapid Products in 2014 (All statistics computedwith 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

1/1/2014 –12/31/2014

17

units: 10–6 arc sec

ultra–rapid

rapid

past 24h

6h predict

19

38

x: 186y: 108

ultra–rapid

rapid

ultra–rapid

past 24h

24h predict

past 24h

6h predict

x: 105
y: 110x: 338y: 278162

1603

ultra–rapid products are expected to be incorporated into the IGS “IGV” combination in
2015; they will also replace USNO’s current ultra–rapid submissions to the IGS Combined
Ultra–rapid “IGU” at that time.
In 2014, seven–parameter Helmert transformations computed between USNO and IGS
ultra–rapid GLONASS orbits had median RMSs of 45 and 107 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–processedsegment of the IGS ultra–rapid GPS–only (aka IGU) values, RMS, by 138 and 92 micro
arc sec, respectively. These data are shown in Tab. 2/Figs. 5–6.
Table 2: Precision of USNO Ultra–Rapid GPS+GLONASS Test Products in 2014 (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

76

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

dates

past 24h

6h predict

1/1/2014 – 12/31/2014

45

107

past 24h
x: 138, y: 92

2 Product Performance in 2014

RMS, 7-Par Helmert Transform btwn USNO, IGS Ultra-Rapid GLO Orbits
300
Median (mm): ultra, past: 45; ultra, pred: 107
250

mm

200

150

100

50

0
0

50

100

150

200
250
day of year 2014

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, 2014. “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 5.0 Software.
USNO Test GPS+GLONASS Ultra-Rapid Polar Motion wrt IGU
24-h post-processed segments compared
500
400
300

micro arc sec

200
100
0

-100
-200
-300
RMS (x, y, micro arc sec): 138, 92
-400
-500
0

50

100

150

200
250
day of year, 2014

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, 2014.

77

USNO Analysis Center
The USNO AC acquired Bernese GNSS Software V5.2 in 2013 and plans to release official
AC products generated using it in 2015. The GPS+GLONASS rapid and ultra–rapid
solutions referenced above have been generated using Bernese GNSS Software V5.2 since
December 2014.

3 USNO AC Conference Presentations/Publications
USNO AC members played an active role at the 2014 IGS Workshop (23–27 June 2014;
Pasadena, CA), contributing three posters and chairing three sessions: Plenary Session
09A, GNSS–Derived Troposphere Delays, Poster Session 05, Estimation and Applicationof GNSS–Based Troposphere Delay, and the IGS Troposphere Working Group meeting.
They also presented their research results at symposia such as ION GNSS+ 2014 and theAmerican Astronomical Society Division on Dynamical Astronomy. Their publications are
as follows:
S. Byram and C. Hackman. IGS Final Troposphere Product Update. IGS Workshop
2014, Poster Session PS05, Pasadena CA, 2014.
S. Byram and C. Hackman. Multi–GNSS Based Processing at the USNO. IGS Workshop
2014, Poster Session PS11, Pasadena CA, 2014.
J. Dousa, S. Byram, G. Gyori, O. Böhm, F. Zus, and C. Hackman. Development Towards
Inter-Technique Tropospheric Parameter Comparisons and Their Exploitation. IGS
Workshop 2014, Plenary Session PY09, Pasadena CA, 2014.
C. Hackman, S.M. Byram, V.J. Slabinski, and J.C. Tracey. USNO GPS/GLONASS PNTProducts: Overview, and GPS+GLONASS vs. GLONASS Only PPP Accuracy.
Proc. 2014 IEEE/Institute of Navigation (ION) Position Location and Navigation
Symposium, 793–803, 2014.
C. Hackman, S.M. Byram, V.J. Slabinski, J.C. Tracey, and J.R. Rohde. USNO Analysis
Center Progress 2012–2014, IGS Workshop 2014, Poster Session PS01, Pasadena
CA, 2014.
C. Hackman. Mitigating the Impact of Predicted–Satellite–Clock Errors on GNSS PPP
Positioning. Proc. ION 2014 International Technical Meeting, 743–50, 2014.
U. Hugentobler and C. Hackman. International GNSS Service (IGS)–Products and Models for Precise GNSS Analyses. COST Action ES1206 Meeting, Munich, Germany,
36 pp, 2014.
V. Slabinski. When did the Mean Solar Day Equal 86,400 SI Seconds? Am. Astron. Soc. Div. on Dynamical Astronomy 2014 Meeting, Session 300, Philadelphia
PA, 2014.
J.C. Tracey. Analysis of GNSS Signal Strength. Proc. ION GNSS+ 2014, 1270–3, 2014.

78

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. of 2012 IEEE/ION Position Location andNavigation Symposium, 659–63, 2012b.
Dach, R., U. Hugentobler, P. Fridez, and M. Meindl. Bernese GPS Software Version 5.0(User Manual). Astronomical Institute, University of Bern, 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.

79

USNO Analysis Center

80

WHU Analysis Center
Technical Report 2014
C. Shi, M. Li, Q. Zhao, Y. Lou
GNSS Research Center, Wuhan University
Wuhan, China
E–mail: shi@whu.edu.cn

1 Introduction
The IGS Analysis Center of the Wuhan University (WHU) has contributed to the International GNSS Service (IGS) since 2012 with a regular determination of the precise
GPS+GLONASS ultra–rapid and rapid products. All the products are produced withthe latest development version of the Positioning And Navigation Data Analyst (PANDA)
Software (Liu and Ge 2003).
In this report we give a summary of the IGS related activities at WHU during the year
2013.

2 PANDA software
The PANDA software package is capable of simultaneously processing various types ofmeasurements from GNSS, SLR, KBR, star trackers and accelerometers in order to estimate ground station coordinates, ZTDs, ERPs and orbits for GNSS satellites, LEOs
and GEOs. Various methods for kinematic, dynamic and reduced–dynamic precise orbit
determination of LEO satellite orbits are developed in this software package.
Both least–squares estimator (for post–processing) and square–root information filter (forreal–time processing) are implemented in the state estimator module (Liu and Ge 2003)
for PANDA. In order to speed up the data processing, an efficient approach of removal
and recovery of station coordinate and ambiguity parameters is employed in the least–squares estimator (Shi et al. 2010). Besides, the ambiguity–fixing can also be performedin network mode or precise point positioning mode, significantly improving the positioning
accuracy of WHU final solutions.

81

WHU Analysis Center
Table 1: List of products provided by WHU
WHU Rapid GNSS products
whuWWWD.sp3
whuWWWD.clk
whuWWWD.erp

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

WHU Ultra–rapid GNSS products
whuWWWD_HH.sp3
whuWWWD_HH.erp

Orbits for GPS/GLONASS satellites;provided to IGS every 6 hours
Observed and predicted ERPs provided to IGS every 6 hours

Figure 1: Weighted RMS of WHU ultra–rapid orbits.

3 WHU Analysis Products
The list of products provided by WHU is summarized in Tab. 1.
The quality of the WHU ultra–rapid product is shown in Fig. 1. The accuracy of thepredicted ultra–rapid orbit product is 3cm, measured as the WRMS compared with the
IGS ultra–rapid orbit (IGU).

82

4 MGEX Activities

Figure 2: MGEX tracking stations.

4 MGEX Activities

IGS started the Multi–GNSS Experiment (MGEX) campaign since 2012 (Montenbruck
et al. 2014). Up to now, more than 90 MGEX tracking stations collect data from theMulti–GNSS system including GPS, GLONASS, Galileo, BeiDou, and QZSS. WHU analyzes MGEX data (Fig. 2) and provides precise satellite orbit and clock solutions basedon PANDA software. BeiDou orbit and clock products from WHU (called “WHM”) areavailable at: ftp://cddis.gsfc.nasa.gov/pub/gps/products/mgex.
The accuracy of the GPS satellite orbit provided by GPS+GLONASS combined solution
from WHU is about 1cm (1D) compared with IGS final solution (Fig. 3).
The accuracy of the GLONASS satellite orbit provided by GPS+GLONASS combined
solution from WHU is about 3cm (1D) compared with IGL final solution (Fig. 5).
The accuracy of the Beidou IGSO (C08) and MEO (C11) satellite orbit provided by
GPS+Beidou combined solution from WHU is about 10 cm validated by SLR data. (Fig. 5
and Fig. 6 ).
The accuracy of the Galileo satellite orbit using GPS+Galileo combined solution from
WHU is about 10 cm validated by SLR data. (Fig. 7 and Fig. 8 ).

83

WHU Analysis Center

Figure 3: GPS orbit compared with IGS final solution.

Figure 4: GLONASS orbit compared with IGL final solution.

84

4 MGEX Activities

Figure 5: Beidou C08 orbit validation by SLR.

Figure 6: Beidou C11 orbit validation by SLR.

85

WHU Analysis Center

Figure 7: Galileo E11 orbit validation by SLR.

Figure 8: Galileo E19 orbit validation by SLR.

86

5 Real Time Activities

Figure 9: The STD of real time clock error compared with IGS final solution.

Figure 10: The STD of real time clock error of GPS satellites.

5 Real Time Activities
IGS Real–Time Service officially launched in April 2013, and WHU is one of the first realtime analysis centers. The CLK15 and CLK16 streams published at IGS real time service
www.igs-ip.net) are the real–time precise satellite orbit and clock products by WHU.
The real time precise orbit is based on ultra–rapid products, which has been introduced in
Section 2. The performance of the real time satellite clock products is shown in Fig. 9.
The precision of clock error is about 0.06ns in 2014.The following figure shows the statistic
results of each satellite.

87

WHU Analysis Center
The statistical result of each satellite is shown in Fig. 10, and the precisions all GPS
satellites have equivalent performance during the year 2014.

Reference
Liu, J. and M. Ge. A software and its preliminary result of positioning and orbit determination. Wuhan University Journal of Natural Sciences, 8(2):603–609, 2003.
Shi, C., Y. Lou, H. Zhang, Q. Zhao, J. Geng, R. Wang, R. Fang, and J. Liu. Seismic
deformation of the M–w 8.0 Wenchuan earthquake from high–rate GPS observations.
Advances in Space Research, 46(2):228–235, 2010.
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. INSIDE GNSS, 9(1):42–49, 2014.

88

EPN Regional Network
Associate Analysis Center
Technical Report 2014
C. Bruyninx1 , A. Araszkiewicz6 , E. Brockmann2 ,A. Kenyeres4 , R. Pacione8 , W. Söhne3 ,G. Stangl5 , K. Szafranek6 , C. Völksen7
1
2
3
4
5
6
7
8

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
E–GEOS Centro di Geodesia Spaziale (ASI/CGS), Contrada Terlecchia,
75100 Matera, Italy

1 Introduction
The IAG (International Association of Geodesy) Regional Reference Frame sub–commission
for Europe, EUREF, defines, provides access and maintains the European Terrestrial Reference System (ETRS89). This is done through the EUREF Permanent GNSS Network(EPN) which is a network of continuously operating GNSS reference stations maintainedon a voluntary basis by EUREF members. EPN observation data, as well as the precise
coordinates and the zenith total delay (ZTD) parameters of all EPN stations, are publicly available. The EPN cooperates closely with the International GNSS Service (IGS);

89

EPN Associate Analysis Center
EUREF members are, for instance, involved in the IGS Governing Board, the IGS Real–Time Pilot Project, the IGS GNSS Working Group, the IGS Antenna Calibration Working
Group, the IGS 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 consistsof the Network Coordinator (managing the EPN Central Bureau), Data Flow Coordinator, Analysis Coordinator, Reference Frame Coordinator, Troposphere Coordinator, andChairs of the Real–time Analysis, Reprocessing, and multi–GNSS Working Groups.
This paper gives an overview of the main changes in the EPN during the year 2014.

2 Tracking Network
At the end of 2014, the EPN network consisted of 263 continuously operating GNSS
reference stations (Fig. 1) from which 31% also belong to the IGS. Before inclusion in the
EPN, the EPN Central Bureau (CB) checks the data quality, meta–data, data availability
and latency, 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. End of 2014, individual calibrations were used at 73 EPN
stations.
Eighteen new stations were integrated in the EPN network in 2014 (see Tab. 1). They
are indicated with triangles in Fig. 1. All new stations added to the EPN in 2014 areequipped with GPS/GLONASS tracking equipment, bringing the percentage of the EPN
stations providing GPS+GLONASS data to 79%. In addition, 160 EPN stations havea receiver capable of tracking GPS L5, although only 60 of them are actually providing
RINEX v2.11 data including L5 (see Fig. 2). At the end of 2014, 134 EPN stations (morethan half of the EPN, see Fig. 3) operated receivers that are certified “Galileo–ready”.
This does however not mean that all these stations provide Galileo observations. In fact,
only 78 of them indicate in their site log that they provide Galileo observations. As will beshown in Section 3, this does not necessarily mean that these stations are also distributing
RINEX files including Galileo observations.

3 RINEX v3
The development of the EPN network towards multi–GNSS is coordinated in a EUREF
working group (chaired by E. Brockmann) which started its activities after the EUREF
symposium 2010 in Gävle (Sweden). The EPN is working with three main data centersdefined as regional data centers (RDC).

90

3 RINEX v3

2014 Dec 24 08:36:03

Figure 1: EPN tracking stations, status in December 2014. N indicate new stations included in
the network in 2014.

2015 Jan 19 03:12:13

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

Figure 2: EPN tracking stations capable of tracking L5 indicated with 4; those in addition
including L5 in their RINEX v2.11 data are indicated by N (status in December 2014).

91

EPN Associate Analysis Center
Table 1: New stations included in the EPN in 2014
4 char–ID

Location

Replacement
or new

Sat. Tracking

Antenna Calibration
used in EPN analysis

ARJ6
CASB
HAS6
JON6
KAD6
LEK6
LOV6
NOR7
OSK6
OST6
OVE6
SKE8
SVE6
TLLG
UME6
VAE6
VIL6
VIS6

Arjeplog, Sweden
CastleBar, Ireland
Hassleholm, Sweden
Jonkoping, Sweden
Karlstad, Sweden
Leksand, Sweden
Lovo, Sweden
Norrkoping, Sweden
Oskarshamn, Sweden
Ostersund, Sweden
Overkalix, Sweden
Skellefteaa, Sweden
Sveg, Sweden
Dublin, Ireland
Umea, Sweden
Vanersborg, Sweden
Vilhelmina, Sweden
Visby, Sweden

new
new
new
new
new
new
new
new
new
new
new
new
new
new
new
new
new
new

GPS+GLO
GPS+GLO
GPS+GLO
GPS+GLO
GPS+GLO
GPS+GLO
GPS+GLO
GPS+GLO
GPS+GLO
GPS+GLO
GPS+GLO
GPS+GLO
GPS+GLO
GPS+GLO
GPS+GLO
GPS+GLO
GPS+GLO
GPS+GLO

Individual from GEO++
Type mean from IGS
Individual from GEO++
Individual from GEO++
Individual from GEO++
Individual from GEO++
Individual from GEO++
Individual from GEO++
Individual from GEO++
Individual from GEO++
Individual from GEO++
Individual from GEO++
Individual from GEO++
Type mean from IGS
Individual from GEO++
Individual from GEO++
Individual from GEO++
Individual from GEO++The IGS RINEX3 transition plan, which was endorsed by the IGS Governing Board in
December 2014, contains the new RINEX v3 file naming conventions and expects that
RINEX v3 data will be put to into the same directories as RINEX v2 data. Presently,
only the BKG RDC is hosting EPN RINEX v3 data (using the old RINEX v2 file names)
in a separate directory. Implementing the IGS RINEX3 transition plan will require a
restructuring of the EPN data centers which will need time.
In the meantime, the number of stations providing RINEX v3 files (using the RINEX
v2 file naming conventions) is still growing (see Fig. 3). Currently, 58 EPN stations aredelivering RINEX v3 data (51 of them include Galileo observations). Taking into accountthat 78 EPN stations indicate in their site log that they provide Galileo observations, thereis clearly still room for progress. Thirteen stations, mainly Leica and Javad receivers, still
provide files with RINEX v3.01 instead of v3.02. Additionally, about 15 stations in Europe
contribute data to the IGS–MGEX project.
An important requirement for the routine utilization of the RINEX v3 observation files
is the availability of quality check software. EUREF members are actively contributing
to this effort by developing and using two software packages: G–Nut/Anubis [1.2.1] (Vaclavovic and Dousa 2015) and BNC [2.12] (Weber and Mervart 2007). Both allow usefuloperations such as RINEX header manipulation and the generation of data quality statistics. Several groups run these programs and make the results in form of plots available on
their web pages: http://www.pecny.cz/GOP/index.php/gnss/data-center/euref-rnx3;

92

EPN CENTRAL BUREAU > Graphs & Maps > Number RINEX3 stations http://www.epncb.oma.be/controlpanel/graphs/number_RIN

CONTROL PANEL > GRAPHS & MAPS > NUMBER RINEX3 STATIONSNUMBER RINEX3 STATIONS

3 RINEX v3

machine-readable
fileNumber of EPN stations delivering RINEX v3 files.
Figure 3:2015 Jan 19 03:18:03

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

Figure 4: EPN tracking stations (134) capable of tracking Galileo: N submitting RINEX v3 data
to EUREF (51); 4 not (yet) submitting RINEX v3 data to EUREF.

93

1 of 102-

EPN Associate Analysis Center
http://www.swisstopo.admin.ch/swisstopo/geodesy/pnac/html/en/anubis_monitor_
r3.html
In addition, the EPN Central Bureau today already routinely cross–checks the RINEX v3
headers against the site log information (similarly to what is done for the RINEX v2 data)
and also verifies the conformity of the RINEX v3 headers with respect to the RINEX v3
format description. Station managers are notified in case errors occur. In the course of2015, the EPN CB web site will be extended with this information.

4 Data Analysis
4.1 Positions
Currently, 16 (from 18 existing) Local Analysis Centers (LACs) deliver SINEX solutions
for the weekly EPN combination. Since January 2014, the GOP LAC focuses on the
EPN reprocessing activities. The DEO LAC does not submit its solutions anymore since2009, but is planning to restart routine analysis in 2015. The new Analysis Combination
Center (Military University of Technology/Warsaw University of Technology consortium)
delivered its first weekly final EPN solution for GPS week 1768 (November 2013). To
ensure the coherence of the MUT/WUT combinations during the first months, the same
strategy as the one used by the previous ACC (BKG) was applied. Since GPS week 1774
(January 2014), only stations processed by at least three LACs are taken into considerationin the final daily and weekly solutions which enables the detection of outliers and thereliability of the solutions. However, exceptions are made for new stations which are,in the beginning of their lifetime, and still processed by less than three LACs. Since
GPS week 1787, the number of reference stations was decreased from 71 to 46 stations inorder to exclusively use EPN stations included in the most recent IGb08 realization. The
new ACC also continues to deliver rapid daily combinations (since 1770 GPS week) andultra–rapid daily combinations (since GPS week 1773) which are mainly used for rapid
monitoring of the EPN station positions.
All combinations are performed with the Bernese GNSS Software (Dach et al. 2013).
Prior to the combination process, the LAC SINEX files provided by the different LAC areautomatically checked against possible metadata inconsistencies (e.g. antenna types andcalibration models, receiver types) and problematic stations are excluded from the combination. Information about these products and coordinate time series are presented at the
EPN ACC webpage (http://www.epnacc.wat.edu.pl). For the rapid combinations, suchinformation, together with characteristics of the combined solution and the inconsistencies from the LAC SINEX files, can be found in the combination reports sent to the BKG
product center (ftp://igs.bkg.bund.de/EUREF/products/WWWW/eurWWWWmr.sum).
Fourteen of the sixteen LACs use both GPS and GLONASS data (in 2014 two LACs
updated their Bernese software and started to include GLONASS observations). The

94

4 Data Analysis

RMS of Helmert Transformation
0.005

RMS [m]

0.004

0.003

0.002

0.001

0.000
1480

1520

1560

1600

1640

1680

1720

1760

1800

1840

ASI
BEK
BKG
COE
DEO
GOP
IGE
IGN
LPT
MUT
NKG
OLG
RGA
ROB
SGO
SUT
UPA
WUT

GPSWEEK

Figure 5: Agreement (RMS of Helmert transformation) between each weekly LACs solution andthe weekly EPN combined solution.

Helmert residuals of the weekly individual solutions with respect to the combined solution have in 2014 a mean RMS of 0.6 millimeters for the horizontal components and 2.4
millimeters for the vertical component. A plot of the agreement between each weekly
LACs solution and the combined solution (see Fig. 5) is presented online at http://www.
epnacc.wat.edu.pl and in the reports available from the EPN CB.

4.2 Troposphere
Beside station coordinates, the 16 LACs also submit zenith total delay (ZTD) parameters
on a routine basis. The ZTDs are delivered with a sampling rate of 1 hour, on a weekly
basis but in daily files. Along with the ZTDs, tropospheric gradients are submitted sinceNovember 2013. The BKG has provided the EPN troposphere coordinator (TC) since2001. It has been very successful in developing the troposphere estimation and combination from a Special Project into routine operation. In June 2014, Wolfgang Söhne, who
assumed the position for more than ten years, handed over the troposphere activities to
Rosa Pacione from the Italian Space Agency/Centro di Geodesia Spaziale (ASI/CGS).
ASI/CGS started with its routine tropospheric combinations at GPS week 1800 (June2014).
The most important task of the new TC in 2014 was to implement scripts for the combination of the tropospheric solutions provided by LAC. The tropospheric combination isbased on a generalized least square method, following Pacione et al. 2011. The software
code was developed in 2008 and it is currently used also in the framework of the EUMETNET EIG GPS Water Vapour Programme (E–GVAP, http://egvap.dmi.dk). The
agreement between BKG and ASI combined tropospheric solutions, based on the data of95

EPN Associate Analysis Center
the whole year 2013 and the entire EPN, is at a sub–millimeter level in term of bias and 1
millimeter level in term of standard deviation. The format of the Tropospheric Summary
Files has also been reviewed and simplified by removing some tables.
Thanks to the growing computation power, the individual LACs enlarged their networks
in 2014. This way, almost all EPN stations are processed by at least four LACs which
improves, for example, the outlier detection. On average 254 stations are processed bymore than three LACs, 8 by two LACs and only 5 by one LACs. In the last four years ofroutine operation (2011–2014), the weekly mean biases (see Fig. 6) are within 2 millimeters
ZTD level, while their standard deviations range between 1 to 2 millimeters (see Fig. 6)
with a few outliers in the last period of routine operation. The jump in the standard
deviation time series (see Fig. 6) occurred at GPS week 1800 is related to the use of adifferent combination software starting from that GPS week.
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 EPN ZTD differences with respect toradiosonde–derived ZTDs are computed for almost 100 stations. For the stations considered, the horizontal distance between radiosonde and GNSS location is varying from lessthan 1 km up to 75 km. The standard deviation of the differences is between 4 and 20
millimeters ZTD, with worse agreement if the distance is long. Moreover, for each EPN
site plots showing monthly mean of ZTD values are available.

4.3 Reprocessing
Currently the EPN working group on Reprocessing conducts a second reprocessing campaign, EPN–Repro2 realized in the IGb08 and it is coordinated by the Bavarian Academyof Sciences and Humanities (BEK). The analysis is being carried out on the EPN datafrom 1996 till 2013 by five analysis centers. It will include three independent solutions
obtained using Bernese 5.2, GAMIT 10.5 and GIPSY 6.2 for the entire EPN and the results of two EPN subnetworks processed with Bernese GNSS Software v5.2. The analysis
strategy is very much consistent with the recent LAC guidelines for the routine processing of the EPN. The processing of the data is performed as a regional network withoutorbit, EOP and clock parameter estimation and relies completely on available reprocessed
products. Due to the lack of reprocessed combined IGS products (2nd IGS Reprocessing
campaign), the reprocessed products provided by CODE and the preliminary reprocessed
products by JPL are used.
In preparation of EPN–Repro2, a benchmark test with the different software packages,
and based on the same data and network design, has shown good agreement between
the different solutions (Völksen et al. 2014). The completion of the EPN–Repro2 daily
solutions is expected for February 2014. First results of the combination of the different
results will be presented at the next EUREF symposium in June 2015. The importance of96

4 Data Analysis

1600
5

1650

1700

1750

1800

1650

1700

1750

1800

ZT D bias [mm]

2.5

0

-2.5

Stdev of ZT D bias [mm]

-5
10

7.5

5

2.5

0
1600

GPS Week

Analysis Centres
ASI

BEK

BKG

COE

DEO

GOP

IGE

IGN

LPT

MUT

NKG

OLG

RGA

ROB

SGO

SUT

UPA

WUT

Figure 6: Weekly mean biases of LACs individual ZTD contributions with respect to the combined ZTD solution (mm ZTD); results from last 4 years of routine operation (Top).
Standard deviation of weekly mean biases of LACs individual ZTD contributions withrespect to the combined ZTD solution (mm ZTD); results from last 4 years of routine
operation (Bottom).

the reprocessing activities has also been acknowledge by installing a Dedicated Analysis
Center (DAC) for Reprocessing at the Geodetic Observatory Pecny (GOP).

97

EPN Associate Analysis Center

5 Densification of the IGS and EPN
Based on the EPN combined weekly SINEX solutions (back to mid–1996), a multi–year
EPN position and velocity solution is maintained as the densification of the IGS realization of the ITRS in Europe. This solution is computed with CATREF software (Altamimi
et al. 2007) and updated each 15 weeks. Up to GPS week 1709, the multi–year solution
was tied to IGS08, since that date the IGb08 was used. This reference frame alignmentis based on the minimum constraint approach and the consistency of the frame realization is checked. When EPN–Repro2 products will become available, the multi–year EPN
solution will be updated to be compliant with the latest standards. The EPN IGb08
densification product files (including a discontinuity table and associated residual position
time series) are available at 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 aims at providing a dense continental–scale homogeneous
station position and velocity field to support the better realization of the ETRS89 andgeophysical modeling. This densification is done by the EPN Reference Frame Coordinator(A. Kenyeres), but actually a Working Group will be formed in 2015 to support the growing
needs of the densification activities. In that frame, EUREF combines the weekly SINEX
solutions provided by European countries for their dense national active GNSS networks
with the weekly EPN SINEX solution. Then, all available weekly combined solutions arestacked to obtain the consistent cumulative position/velocity solution. Both combinations
are done using the CATREF software using the same approach and parameters as for thegeneration of the EPN IGb08 densification ensuring full consistency from the global tolocal level. The total number of stations included in the EPN densification exceeded
2500 as of December 2014. Two contributions (IGN, France and BIGF, UK) are global
solutions and therefore the EPN densification shall be considered as a global solution. The
densification products will be an essential contribution to several groups and projects as
the IAG working group on “The integration of dense velocity field in the ITRF ”, EPOS
(European Plate Observatory System) and EUPOS (European Positioning System). This
work is still in progress (see Kenyeres et al. 2014).

6 Stream and Product Dissemination
The availability of all EPN real–time streams and products at the three EUREF regional broadcasters located at ASI (http://euref-ip.asi.it:2101), BKG (http://www.
euref-ip.net) and ROB (http://www.euref-ip.be/) continued to converge in 2014. For
this purpose, the EPN CB compares on–line the status of each mountpoint at the threebroadcasters, so that the service providers, station managers and users can immediately
see if an outage is caused by one of the casters or the stream provider. The aim is full
flexibility, so that every user is able to switch between the casters without loss of availabil-98

References
ity. The on–line monitoring will be made publicly available in early 2015. For the time
being, it is not planned to mix mountpoints providing legal RTCM 3 messages with newmountpoints providing RTCM MSM messages on the three EPN broadcasters. In addition, EUREF is working on guidelines for the EPN broadcasters which will be released in
2015.
NETWORK & DATA > DATA ACCESS > REAL-TIME > PRODUCTS & DATA STREAMSREAL-TIME PRODUCTS
Mountpoint
ASI (status: 2015-01-29 15:35 UTC)
EUREF01 RTCM 3.0 - BKG
EUREF02 RTCM 3.0 - BKG
RTCM3EPH RTCM 3 - BKG

BKG (status: 2015-01-29 15:35 UTC)
RTCM 3.0 - EUREF filter combination
RTCM 3.0 - EUREF filter combination

ROB (status: 2015-01-29 15:35 UTC)
RTCM 3.0 - EUREF filter combination
RTCM 3.0 - EUREF filter combination

BKG (status: 2015-01-29 15:35 UTC)
RTCM 3.1 - ergnss-ip.ign.es:2101/ACOR0(1)
RTCM 3.1 - www.igs-ip.net:2101/AJAC0(2)RTCM 3.0 - ergnss-ip.ign.es:2101/ALAC0(1)
RTCM 3.0 - ergnss-ip.ign.es:2101/ALBA0(1)
RTCM 2.3 - ergnss-ip.ign.es:2101/ALME0(1)
RTCM 3.0 - none
RTCM 3.1 - Ordnance Survey of Northern Ireland
RTCM 3.0 - ICC Catnet
Last received on 2014-12-17 07:55 UTC
RTCM 2.3 - SRC PAS

ROB (status: 2015-01-29 15:35 UTC)
RTCM 3.1 - IGNE, Servicio de Programas Geodesicos
RTCM 3.1 - none
RTCM 3.1 - IGNE, Servicio de Programas Geodesicos
RTCM 3.1 - IGNE, Servicio de Programas Geodesicos
RTCM 2.3 - IGNE, Servicio de Programas Geodesicos
RTCM 3.0 - none
RTCM 3.1 - Ordnance Survey of Northern Ireland
RTCM 3.0 - ICC Catnet
Last received on 2014-12-17 07:55 UTC
RTCM 2.3 - SRC PAS
RTCM 3.0 - BKG
Last received on 2014-12-05 02:05 UTC
RTCM 3 - Ant Descriptor-Protected-Cartographic Institute of
Valencia
RTCM 3.1 - none
Last received on 2014-11-18 12:05 UTC
Last received on 2014-11-18 12:05 UTC
Last received on 2014-11-20 14:05 UTC
RTCM 3.1 - none
RTCM 3.0 - TU Bucharest
RTCM 3.0 - Budapest University
RTCM 2 - 9600
RTCM 2.3 - IGNE, Servicio de Programas Geodesicos
RTCM 3.1 - IGNE, Servicio de Programas Geodesicos

REAL-TIME DATA STREAMSMountpoint
ASI (status: 2015-01-29 15:35 UTC)
ACOR0
RTCM 3.1 - ergnss-ip.ign.es:2101/ACOR0(1)AJAC0
RTCM 3.1 - rgp-ip.ign.fr:2101/AJAC1(1)ALAC0
RTCM 2.3 - ergnss-ip.ign.es:2101/ALAC0(1)ALBA0
RTCM 2.1 - ergnss-ip.ign.es:2101/ALBA0(1)ALME0
RTCM 2.3 - ergnss-ip.ign.es:2101/ALME0(1)
AUT10
RTCM 3.0 - www.euref-ip.net:2101/AUT10(1)BELF0
RTCM 3.1 - www.euref-ip.net:2101/BELF0(1)BELL0
RTCM 3.0 - www.euref-ip.net:2101/BELL0(1)
BOGI0
Last received on 2014-12-17 07:55 UTC
BOR10
RTCM 2.3 - www.euref-ip.net:2101/BOR10(1)
BORJ0
BORJ1
RTCM 3.0 - www.euref-ip.net:2101/BORJ1(1)

RTCM 3.0 - BKG
Figure 7: EPN real–time monitoringat the EPN CB (under construction).

BORR0

RTCM 3.0 - icverva.icv.gva.es:2101/RTBO1(1)

RTCM 3.0 - ICV

BRST0
BRUX0
BRUX1
BRUX7
BSCN0
BUCU0
BUTE0
BZRG0
CACE0
CANT0
CANT1

RTCM 3.0 - BRST0 rgp-ip.ign.fr:2101/BRST1(1)Last received on 2014-11-18 12:05 UTC

RTCM 3.0 - www.igs-ip.net:2101/BRST0(2)
RTCM 3.0 - www.igs-ip.net:2101/BRUX0(2)

RTCM 3.0 - rgp-ip.ign.fr:2101/BSCN1(1)
RTCM 3.0 - www.euref-ip.net:2101/BUCU0(1)
RTCM 3.0 - /BUTE0(1)Never received
RTCM 2.3 - ergnss-ip.ign.es:2101/CACE0(1)
RTCM 3.1 - ergnss-ip.ign.es:2101/CANT0(1)
RTCM 2.3 - ergnss-ip.ign.es:2101/CANT1(1)

RTCM 3.0 - rgp-ip.ign.fr:2101/BSCN1(1)
RTCM 3.0 - TU Bucharest
RTCM 3.0 - Budapest University
RTCM 2.3 - www.igs-ip.net:2101/BZRG0(2)
RTCM 2.3 - ergnss-ip.ign.es:2101/CACE0(1)
RTCM 3.0 - ergnss-ip.ign.es:2101/CANT0(1)References

Altamimi, Z., P. Sillard, and C. Boucher. CATREF software: Combination and analysisof terrestrial reference frames. LAREG, Technical, Institut Géographique National,
Paris, France, 2007.
Dach, R. Bernese GNSS Software: New features in version 5.2. Document compiled by
the AIUB Bernese GNSS Software development team. http://www.bernese.unibe.
ch/docs/BSW52_newFeatures.pdf, 2013.
Kenyeres, A., T. Horvath, A. Caporali, E. Brockmann, B. Droscak, P. Franke, B. Garayt,
M. Giannou, I. Georgiev, D. Hansen, L. Huisman, I. Jumare, J. Nagl, P. Pihlak,
M. Ryczywolski, G. Stangl, and M. Valdes. Global Reference Frame Densification
Based on the Integration of Regional and National Active GNSS Network Products.
Presented at 2014 IGS Workshop, Pasadena, California, June 23–27, 2014.
Pacione, R., B. Pace, S. de Haan, H. Vedel, R. Lanotte, and F. Vespe. Combination
Methods of Tropospheric Time Series. Adv. Space Res., 47 (2):323–335, 2011. DOI:
10.1016/j.asr.2010.07.021, 2011.
Vaclavovic, P. and J. Dousa. G–Nut/Anubis – open–source tool for multi–GNSS data
monitoring. In: IAG Symposia Series, Springer, Vol. 143, 2015. (accepted.) Springer,
Vol. 143, 2015, accepted.

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EPN Associate Analysis Center
Völksen, C., A. Araszkiewicz, R. Pacione, B. Pace, and K. Szafranek. The Benchmark Testof the EPN–Repro2 campaign. Presented at EUREF Symposium, Vilnius, Lithuania,
June 3–7, 2014.
Weber, G. and L. Mervart. The BKG Ntrip Client (BNC) Report on EUREF Symposium2007 in London. Mitteilungen des Bundesamtes fuer Kartographie und Geodaesie,
Band 42, Frankfurt, 2009.

100

SIRGAS Regional Network
Associate Analysis Center
Technical Report 2014
Laura Sánchez
Deutsches Geodätisches Forschungsinstitut
der Technischen Universität München (DGFI–TUM)
Alfons–Goppel–Str. 11, 80539 Munich, Germany
E–mail: lm.sanchez@tum.de

1 Introduction
The IGS Regional Network Associate Analysis Center for SIRGAS (IGS RNAAC SIR)
was established in June 1996 under the responsibility of the Deutsches Geodätisches
Forschungsinstitut (Seemüller and Drewes 1998), since January 2015 integrated into theTechnische Universität München. The main objective of the IGS RNAAC SIR is thepermanent analysis of the SIRGAS reference frame. The present activities of the IGS
RNAAC SIR concentrate on (Sánchez 2014)• the computation of loosely constrained weekly solutions for further combinations of
the network (e.g., integration into the IGS polyhedron, computation of cumulative
solutions, etc.). These solutions are weekly delivered to the IGS in SINEX format to
be combined together with those generated by the other IGS Global and Regional
Analysis Centers. They are named sirwwww7.snx (wwww stands for the GPS week);• weekly station positions aligned to the same reference frame in which the IGS
GNSS orbits are given, i.e., the IGS reference frame. These positions are applied
as reference values for surveying applications in Latin America. Their name issiryyPwwww.crd (yy indicates the last two digits of the year).
• multi–year solutions providing station positions and constant velocities to estimate
the kinematics of the reference frame and as support for applications requiring time–dependent coordinates. They are identified by SIRyyPnn.SNX (nn being the numberof the cumulative solution computed in one year).

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SIRGAS Associate Analysis Center

2 The SIRGAS reference frame
The SIRGAS reference frame was regularly computed by the IGS RNAAC SIR as only
one common network until August 31, 2008 (GPS week 1495) (Seemüller et al. 2012).
Afterwards, due to the increasing number of stations (about 400 in December 2014),
different sub–networks were defined and, at present, the analysis strategy is based on the
combination of individual solutions including (Brunini et al. 2012)• one core network (SIRGAS–C) composed of a set of geographically well–distributedand consistently reliable reference stations (Fig. 1). 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) realizing densifications of the core network(Fig. 1). 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 new reference stations (mainly those installed by the national agencies
responsible for the local reference networks).

3 SIRGAS analysis centers
The SIRGAS–C network is processed by DGFI–TUM as IGS RNAAC SIR. The SIRGAS–
N networks are computed by the SIRGAS Local Processing Centers, which operate under
the responsibility of national Latin American organizations. At present, the SIRGAS
Local Processing Centers are:
• CEPGE: Centro de Procesamiento de Datos GNSS del Ecuador, Instituto Geográfico
Militar (Ecuador)• CNPDG–UNA: Centro Nacional de Procesamiento de Datos GNSS, Universidad
Nacional (Costa Rica)• CPAGS–LUZ: Centro de Procesamiento y Análisis GNSS SIRGAS de la Universidad
del Zulia (Venezuela)• IBGE: Instituto Brasileiro de Geografia e Estatistica (Brazil)• IGAC: Instituto Geográfico Agustín Codazzi (Colombia)• IGM–Cl: Instituto Geográfico Militar (Chile)• IGN–Ar: Instituto Geográfico Nacional (Argentina)

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3 SIRGAS analysis centers

Figure 1: SIRGAS reference network (as of January 2015).

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SIRGAS Associate Analysis Center• INEGI: Instituto Nacional de Estadística y Geografía (México)• SGM: Servicio Geográfico Militar (Uruguay)
These processing centers deliver 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 positions and velocities. The individual solutions are combinedby the SIRGAS Combination Centers currently operated by DGFI–TUM (Sánchez et al.
2012) and IBGE (Costa et al. 2012).

4 Routine processing of the SIRGAS reference frame
The SIRGAS processing centers follow unified standards for the computation of the loosely
constrained solutions (Sánchez et al. 2013). These standards are generally based on theconventions outlined by the IERS and the GNSS–specific guidelines defined by the IGS;
with the exception that in the individual 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 not compute these parameters), and positions for all stations areconstrained to ±1 m (to generate the loosely constrained solutions in SINEX format).
INEGI (Mexico) and IGN–Ar (Argentina) employ the software GAMIT/GLOBK (Herring
et al. 2010); the other local processing centers use the Bernese GPS Software Ver. 5.2(Dach et al. 2007, 2013).

5 New processing standards for the SIRGAS reference frame
Since January 2014, the SIRGAS processing centers apply the standards of the IERS
Conventions 2010 (Petit and Luzum 2010) and the characteristics specified by the IGS forthe second reprocessing of the IGS global network. The main changes with respect to theprevious processing strategy are (Sánchez et al. 2015):• Reference frame: IGS08/IGb08 (Rebischung et al. 2012)• Antenna phase center model: igs08.atx (Schmid 2011)• Tropospheric zenith delay modelling based on the Vienna Mapping Function 1(VMF1, Böhm et al. 2006) with a priori values (∼dry part) from the gridded coefficients provided by J. Böhm at http://ggosatm.hg.tuwien.ac.at/DELAY/GRID/VMFG and refinement through the computation of partial derivatives with 2–hourintervals within the network adjustment• Tidal corrections for solid Earth tides, permanent tide, and solid Earth pole tide as
described by Petit and Luzum 2010. The ocean tidal loading is reduced with the104

7 Outlook
FES2004 model (Letellier 2004) and the atmospheric tidal loading caused by thesemidiurnal constituents S1 and S2 is reduced following the model of van Dam andRay 2010. The reduction coefficients for the ocean tidal 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.
• Non–tidal loadings like atmospheric pressure, ocean bottom pressure, or surfacehydrology are not reduced.
At present, the SIRGAS processing centers are recomputing the daily normal equations
backwards until January 1997 applying these new standards.

6 Modelling post–seismic deformations in the SIRGAS region
The Maule 2010 earthquake in Chile generated the largest displacements of geodetic observation stations ever observed in terrestrial reference frames (Sánchez et al. 2013). Coordinates changed by up to 4 m, and deformations were measurable in distances of up
to more than 1000 km from the epicenter. The station velocities in the regions adjacentto the epicenter changed dramatically after the seism; while they were oriented eastward
with approximately 2 cm/y before the event, they are now directed westward with about
1 cm/y (Sánchez 2014; Sánchez et al. 2015). The 2010 Baja California earthquake in Mexico caused displacements on the dm level also followed by anomalous velocity changes.
The main problem for geodetic applications is the fact that there is no reliable reference
frame available in the region. To overcome this inconvenience, DGFI–TUM, acting as the
IGS–RNAAC–SIR, computed a new multi–year solution for the SIRGAS reference frame(Fig. 2) considering only the four years after the seismic events (mid–2010 ... mid–2014).
The obtained station positions and velocities refer to the IGb08 reference frame, epoch
2013.0. The averaged rms precision is ±1.4 mm horizontally and ±2.5 mm vertically forthe station positions at the reference epoch, and ±0.8 mm/y horizontally and ±1.2 mm/yvertically for the constant velocities. Based on this solution (called SIR14P01), a newcontinuous deformation model for SIRGAS was computed (Fig. 3) following the strategy
implemented by Drewes and Heidbach 2012. It is clear that the tectonic structure in SouthAmerica has to be redefined. The area south of 35◦ S to 40◦ S was considered as a stablepart of the South American plate. Now we see that there are large and extended crustal
deformations.

7 Outlook
The present SIRGAS activities concentrate on the reprocessing of the weekly SIRGAS
normal equations backwards until January 1997 applying the new standards. The IGS

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SIRGAS Associate Analysis Center

Figure 2: Horizontal velocities of the multi–year solution SIR14P01 (IGb08, 2013.0).

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7 Outlook

Figure 3: Post–seismic deformation model after the 2010 earthquakes in Latin America.

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SIRGAS Associate Analysis Center
RNAAC SIR takes care of the computations from 1997 until August 2008, when thefirst SIRGAS Local Processing Centers started operating. From September 2008 until
December 2013, the reprocessing includes the combination of the individual (reprocessed)
solutions delivered by the SIRGAS Local Processing Centers for the SIRGAS–N national
networks. Once the reprocessing is completed, a cumulative solution for the SIRGAS
reference frame including time series analysis and seismic effects shall be computed.

8 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 Institute forGeography and History (PAIGH) is highly appreciated. More details about the activities
and new challenges of SIRGAS, as well as institutions and colleagues working on can befound at www.sirgas.org.

References
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.
J. Geophys. Res., 111, B02406, 2006.
DOI:10.1029/2005JB003629
Brunini, C., L. Sánchez, H. Drewes, S.M.A. Costa, V. Mackern, W. Martinez,
W. Seemüller, and A.L. Da Silva. Improved analysis strategy and accessibility of
the SIRGAS Reference Frame. In: S. Kenyon, M.C. Pacino, and U. Marti (Eds.).
Geodesy for Planet Earth, IAG Symposia, 136:3–10, 2012.
Costa, S.M.A., A.L. Silva, and J.A. Vaz. Report on the SIRGAS–CON combined solution by IBGE Analysis Center. Geodesy for Planet Earth, 136:853–857, 2012. DOI:
10.1007/978–3–642–20338–1_107
Dach, R., U. Hugentobler, P. Fridez, and M. Meindl (Eds.). Bernese GPS Software Version
5.0 (User Manual). Astronomical Institute, University of Bern, 2007.
Dach, R. Bernese GPS Software: New features in version 5.2. Astronomical Institute,
University of Bern, 2013. Available at http://www.bernese.unibe.ch.
Drewes, H. and O. Heidbach. The 2009 horizontal velocity field for South America and108

References
the Caribbean. In: S. Kenyon, M.C. Pacino, and U. Marti (Eds.). Geodesy for Planet
Earth, IAG Symposia 136:657–664, 2012. DOI:10.1007/978–3–642–20338–1_81
Herring, T.A., R.W. King, and S.C. Mcclusky. Introduction to GAMIT/GLOBK, Release
10.4. Massachusetts Institue of Technology, 2010. 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
et de l’Espace, 2004.
Petit, G. and B. Luzum (Eds.). IERS Conventions (2010). IERS Technical Note, 36. Verlag
des Bundesamtes für Kartographie und Geodäsie, Frankfurt a.M., 2010.
Rebischung, P., J. Griffiths, J. Ray, R. Schmid, X. Collilieux, and B. Garayt. IGS08:
the IGS realization of ITRF2008. GPS Solutions, 16(4):483–494, 2012. DOI:
10.1007/s10291–011–0248–2.
Sánchez, L., H. Drewes, C. Brunini, and M.V. Mackern. SIRGAS core network stability.
IAG Symposia 143 (in press), 2015.
Sánchez, L., W. Seemüller, H. Drewes, L. Mateo, G. González, A. Silva, J. Pampillón,
W. Martinez, V. Cioce, D. Cisneros, and S. Cimbaro. Long–term stability of the SIRGAS Reference Frame and episodic station movements caused by the seismic activity
in the SIRGAS Region. In: Z. Altamimi and X. Collilieux (Eds.): Reference Frames
for Applications in Geosciences, IAG Symposia, 138:153–161, 2013. DOI:10.1007/978–3–642–32998–2_24
Sánchez, L., W. Seemüller, and M. Seitz. Combination of the weekly solutions delivered by the SIRGAS Processing Centers for the SIRGAS–CON Reference Frame. In:
S. Kenyon, M.C. Pacino, and U. Marti (Eds.), Geodesy for Planet Earth, IAG Symposia 136:845–851, 2012. DOI:10.1007/978–3–642–20338–1_106
Sánchez, L. IGS Regional Network Associate Analysis Center for SIRGAS (IGS RNAAC
SIR). Report of activities 2013. International GNSS Service Technical Report 2013,
pp.103–114, 2014.
Schmid, R. Upcoming switch to IGS08/igs08.atx – Details on igs08.atx. IGSMAIL–6355(http://igs.org/pipermail/igsmail/2011/006347.html), 2011.
Seemüller, W. and H. Drewes. Annual report 1997 of the RNAAC SIRGAS. In: IGS 1997
Technical Reports, 173–174, IGS CB, JPL Pasadena, 1998.
Seemüller, W., M. Seitz, L. Sánchez, and H. Drewes. The new multi–year position andvelocity solution SIR09P01 of the IGS Regional Network Associate Analysis Center(IGS RNAAC SIR). In: S. Kenyon, M.C. Pacino, and U. Marti (Eds.). Geodesy
for Planet Earth, IAG Symposia 136:877–883, 2012. DOI:10.1007/978–3–642–20338–
1_110.

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van Dam, T. and R. Ray. S1 and S2 atmospheric tide loading effects for geodetic applications. 2010. Data set accessed 2013–06–01 at http://geophy.uni.lu/
ggfc-atmosphere/tide-loading-calculator.html.

110Part III

Data Centers111

Infrastructure Committee
Technical Report 2014
Ignacio Nacho Romero
ESA/ESOC, Germany
E–mail: Ignacio.Romero@esa.int

1 Summary of Activities in 2014
The infrastructure committee consists of the members listed in Tab. 1. The IC broadly
participated and helped organize the IGS workshop 2014 in Pasadena, coordinating one
poster session, one presentation session and two splinter sessions. We produced the RINEX
3 transition plan drafts and revised it as need after all the inputs, and got it approvedin the December 2014 GB meeting. We helped to monitor adherence to the RINEX 2.11
standard in the IGS data centers; no evolution of the RINEX 2.11 format is allowed andthus no data from Beidou, etc should be present in those files. We helped to promote theuse of RINEX 3 data using the specified “long names”.
Table 1: Current Members: re–appointed in December 2013 for terms up to December 2015
Name

Affiliation

Carine Bruyninx
Lou Estey
Gary Johnston
Nacho Romero (Chairman)
Mike Schmidt
Axel Ruelke

ROB
UNAVCO
GA
ESOC
NRCan
BKG

2 Activity plan in 2015
• Continued IGS workshop 2014 recommendations implementation:– Implementation of the RINEX 3 transition plan (as detailed below)

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Infrastructure Committee
Table 2: Ex–officio Members
Name

Affiliation

Steve Fisher
Kevin Choi
Mark Caissy
Bruno Garayt
Carey Noll
Michael Coleman

Central Bureau
Analysis Coordinator
Real time Working Group Chair
Reference Frame Coordinator
Data Center Working Group Chair
Clock Products Coordinator– To help promote a GNSS metadata XML exchange format with IGS and international partners– To start an L1 CA Navigation Bit Stream system• RINEX 3 transition plan continued implementation following the steps outlined in
the plan approved by the GB in December 2014 meeting:– NC/IC actions; new station IDs, site log new field, adapting site guidelines,
adapting the IGS Station Log Manager– DC actions; Accept and check new long–name files, write Rx3 streams to thecorrect names, consider effect on product files storage– AC actions; encourage all ACs to process RINEX 3 files with new names,
RFWG to consider SINEX changes to accommodate the new ’a9’ station IDs,consider the impact on clock and tropo files as well.
• To better support the Network Coordinator by having more frequent telecons between the IC Chair and the NC, so as to coordinate the inclusion of all used stations
into the IGS network to return to “one network” and to more effectively monitor the
Data Center file holdings.

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CDDIS Global Data Center
Technical Report 2014
C. NollNASA Goddard Space Flight Center
Code 690.1, Greenbelt, 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 Dataand Information System (EOSDIS) Distributed Active Archive Centers (DAACs); EOSDIS data centers serve a diverse user community and are tasked to provide facilities tosearch and access science data and products. The CDDIS is also a regular member of theInternational Council for Science (ICSU) World Data System (WDS).
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 2014 are summarized below; thisreport also includes any recent changes or enhancements made to the CDDIS.

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CDDIS Data Center

2 System Description
The CDDIS archive of IGS data and products are accessible worldwide through anonymous
ftp (ftp://cddis.gsfc.nasa.gov). The CDDIS has recently implemented web–based
access to the archive (http://cddis.gsfc.nasa.gov/archive). The CDDIS is locatedat NASA’s Goddard Space Flight Center (GSFC) and is available to users 24 hours perday, 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 11.7 Tbytes in size of which 11 Tbytes(95%) is devoted to GNSS data, products (710 Gbytes), and ancillary information. Alldata and products are accessible through subdirectories of ftp://cddis.gsfc.nasa.gov/
gnss (a symbolic link to ftp://cddis.gsfc.nasa.gov/gps).

3.1 GNSS Tracking Data
3.1.1 Operational Data Archive
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 (or receive) data holdings not routinely transmitted to the CDDIS by an operational or regional
data center. Tab. 1 summarizes the types of IGS operational GNSS data sets archived at116

3 Archive Content
Table 1: GNSS Data Type Summary
Data Type
Daily GNSS
Hourly GNSS
High–rate GNSS
Satellite GPS

Sample Rate
30 sec.
30 sec.
1 sec.
10 sec.

Data Format

Available On–line

RINEX and compact RINEX
Compact RINEX
Compact RINEX
Compact RINEX

Since 1992
10+ years
Since May 2001
Since 2002

Table 2: GNSS Data Archive Summary for 2014
Data Type(GNSS)

Avg. No.
Sites/Day

No.
Unique Site

Daily
HourlyHigh–rate

475
310
166

534
341
200

Avg.
Volume/Day
1,100 Mb
383 Mb
2,096 Mb

Total
Volume/Year
400 Gb140 Gb765 Gb

No.
Files
735K
6,705K
9,750K

Directory
Location/gnss/data/daily/gnss/data/hourly/gnss/data/highrate

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.
The CDDIS archives four major types/formats of GNSS data, all in RINEX format, as
described in Tab. 1. 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 175K daily station days from534 distinct GNSS receivers were archived at the CDDIS during 2014. 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. Although these data are retained on–line, 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 341 hourly sites (over 6.7 million files) were archived
during 2014.
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 200 high–rate sites (nearly 10
million files) were also archived in the CDDIS in 2014.
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

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Table 3: GNSS MGEX Data Archive Summary for 2014
Data Type(GNSS)

Avg. No.
Sites/Day

No.
Unique Site

No.
Files

Avg.
Volume/Day

Daily
HourlyHigh–rate

100
50
40

115
54
47

35.1K
17.1K
13.6K

500 Mb100 Mb1,350 Mb

Directory
Location/gnss/data/campaign/mgex/daily/gnss/campaign/mgex/data/hourly/gnss/campaign/mgex/data/highrate

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–specificnavigation 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.sta
tus) 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 datadelivered 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 thecontents of such a summary file.
3.1.2 MGEX Archive
During 2014 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. 3. Daily status files are also provided
that summarize the MGEX data holdings; however, data quality information, generated for
operational GNSS data holdings, is not available through the software created by CDDIS
to summarize data in RINEX V3 format. Products derived in support of MGEX by three
to six ACs are also available through the CDDIS (/gnss/products/mgex/WWWW).
The CDDIS also added a merged, multi–GNSS broadcast ephemeris file containing GPS,GLONASS, Galileo, BeiDou, QZSS, and SBAS ephemerides from MGEX stations. Thisfile, generate by colleagues at the Technical University in Munich (TUM) and Deutsches
Zentrum für Luft– und Raumfahrt (DLR), is similar to the daily and hourly concatenated broadcast message files provided by the CDDIS for the operational data sets; it
contains all the unique broadcast navigation messages for the day. The file is denoted
brdmDDD0.YYp.Z and found in daily subdirectories within the MGEX archive at CDDIS

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3 Archive Content(/gnss/data/campaign/mgex//daily/rinex3/YYYY/DDD/YYp).
In order to promote usage of RINEX V3 and allow users (and data centers) to become
familiar with the format and file naming conventions, ESA began delivery of data fromMGEX stations using both RINEX V2 and V3 filename formats. The CDDIS established a daily subdirectory for these files within the daily MGEX directory structure(/gnss/data/campaign/mgex/daily/rinex3/YYYY/DDD/crx).
Colleagues at TUM and DLR are also providing GPS and QZSS CNAV (civilian navigation) data on an operational basis within MGEX. These messages are collected from a
sub–network (ten stations) of MGEX stations and are provided in a merged daily file ina format similar to RINEX. These files are named brdxDDD0.YYx.Z and stored in a daily
subdirectory within the MGEX archive at CDDIS (/gnss/data/campaign/mgex/daily/rinex3/YYYY/cnav).
Colleagues at DLR provided a new product, differential code biases (DCBs) for the
MGEX campaign. This product was derived from GPS, GLONASS, Galileo, and BeiDou
ionosphere–corrected pseudorange differences and is available in the bias SINEX format.
Two files are available, daily satellite and daily satellite and station biases, for 2013–2014
in CDDIS directory /gnss/products/mgex/dcb. Additional details on the DCB productare available in IGSMail message 6868 sent in February 2014.

3.2 IGS Products
The CDDIS routinely archives IGS operational products (daily, rapid, and ultra–rapid orbits and clocks, ERP, and station positions) as well as products generated by IGS working
groups and pilot projects (ionosphere, troposphere, real–time clocks). Tab. 4 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 fromGLONASS 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 Project,and current IGS Real–Time Service, since 2009.
In 2014, the IGS analysis centers provided products for the second IGS reprocessing campaign (repro2). The CDDIS will provide support through upload of files from the ACs
and online archive of these products (/gnss/products/WWWW/repro2).

119

CDDIS Data Center
Table 4: GNSS Product Summary
Product Type

Number of
ACs/AACs

VolumeOrbits, clocks,
ERP, positions
Troposphere

14+Combinations

1.2 Gb/week

Combination

Ionosphere

4+Combination

Real–time clocks
Repro2 products

Combination
9

2.6 Mb/day,
940 Mb/year
4 Mb/day
1.5 Gb/year
6.0 Mb/week
500 Mb/week

Directory/gnss/products/WWWW (GPS, GPS+GLO)/glonass/products/WWWW (GLO only)/gnss/products/troposphere/YYYY/gnss/products/ionex/YYYY/gnss/products/rtpp/YYYY/gnss/products/WWWW/repro2

Note: WWWW=4–digit GPS week number; YYYY=4–digit year; GLO=GLONASS

3.3 Real–Time Activities
In 2013, the CDDIS staff configured a server and began testing a real–time caster to provide
a real–time streaming capability at GSFC and support the IGS Real–Time Service (IGS
RTS). The CDDIS successfully tested obtaining product streams from the BKG and IGS
casters and providing access to these streams to authorized users. Work continued in 2014
to make the system operational and in spring 2014, the CDDIS caster was fully installed
for broadcasting product streams in real–time. The caster runs the NTRIP (Network
Transport of RTCM via internet Protocol) format.
The majority of the work in 2014 involved development of a registration process that satisfied NASA security requirements and collected information required by the IGS RTS. As
stated previously, the CDDIS is one of NASA’s EOSDIS DAACs and through EOSDIS, hasaccess to a world–class user registration process, the EOSDIS User Registration System(URS), with over 100K users in its system. Since the NTRIP–native registration/accesssoftware was not compatible with NASA policies, the CDDIS developed software to interface the caster and the URS within a generic Lightweight Directory Access Protocol(LDAP) framework. The module was specifically developed to easily interface with multiple user verification systems and was given back to the NTRIP community for possible
inclusion in future releases. The user registration form is available on the CDDIS website;
once completed, the data are passed to the URS, which generates an email to the user
with a validation link. The user accesses the link and the URS validates the form’s data;
this process is accomplished within a minute or less. The user’s validated access request
is submitted to CDDIS staff for access authorization to the CDDIS caster. This second
step is not yet automated and can take several hours to configure depending on the timeof day. Furthermore, users registering in this system have access to the entire suite of
EOSDIS products across all 12 EOSDIS DAACs.

120

4 System Usage
Initially, the CDDIS caster is providing access to product streams from both the BKG
and IGS casters. Data streams have also been tested, provided through JPL for receivers
in NASA’s Global GPS Network. This network of roughly seventy globally distributed,
geodetic quality, dual frequency receivers, will add 1Hz data streams to those current
available from the IGS RTS.
Once the CDDIS caster is operational, the system will serve as a third primary casterfor the IGS RTS, thus providing a more robust topology with redundancy and increased
reliability for the service. User registration, however, for all three casters is unique; therefore current users of the casters located at the IGS and BKG will be required to register
through the CDDIS registration process in order to use the CDDIS caster.
The CDDIS has also developed software to capture real–time data streams into fifteen–
minute high–rate files. This capability requires further testing as the CDDIS caster becomes operational and data streams from real–time stations are added.

3.4 Supporting Information
Daily status files of GNSS data holdings, reflecting timeliness of the data delivered aswell as statistics on number of data points, cycle slips, and multipath, continue to begenerated by the CDDIS. By accessing these files, the user community can receive a quick
look at a day’s data availability and quality by viewing a single file. The daily status files
are available through the web at URL ftp://cddis.gsfc.nasa.gov/reports/gnss. 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 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/reports/gnss. The
CDDIS also maintains an archive of and indices to IGS Mail, Report, Station, and other
IGS–related messages.

4 System Usage
Fig. 1 summarizes the usage of the CDDIS for the retrieval of GNSS data and products
in 2014. This figure illustrates the number and volume of GNSS files retrieved by theuser community during 2014, categorized by type (daily, hourly, high–rate, MGEX data,121

CDDIS Data Center
products). Nearly 370 million files (over 50 Tbytes), excluding robot downloads, weretransferred in 2014, with an average of nearly 30 million files per month. Fig. 2 illustrates
the profile of users accessing the CDDIS IGS archive during 2014. The majority of CDDIS
users were once again from hosts in Europe, Asia, and North America.

5 Recent Developments
5.1 CDDIS Website
Work on an update of the CDDIS website was completed in early 2014. In addition
to a refresh of the appearance of the website, the content was reviewed and updated.
An application for the enhanced display and comparison of the contents of IGS, ILRS,
and IDS site logs was completed in 2014. The Site Log Viewer is an application for theenhanced display and comparison of the contents IAG service site logs. Through the Site
Log Viewer application, users can display a complete site log, section by section, display
contents of one section for all site logs, and search the contents of one section of a site log
for a specified parameter value. Thus, users can survey the entire collection of site logs
for systems having particular equipment or characteristics.
A second application, the CDDIS Archive Explorer, is currently under development to aid
in discovering data available through the CDDIS. The application will allow users, particularly those new to the CDDIS, the ability to specify search criteria based on temporal,
spatial, target, site designation, and/or observation parameter in order to identify dataand products of interest for download. Results of these queries will include a listing ofsites (or other metadata) or data holdings satisfying the user input specifications. Such auser interface will also aid CDDIS staff in managing the contents of the archive.

5.2 Next Generation Hardware
Funding was identified in 2013 to procure a computer system refresh for the CDDIS.
The CDDIS system engineer reviewed current and near–term requirements and developed
a hardware procurement strategy. Hardware was procured in mid–2014 with installation
beginning in late 2014 and scheduled for completion and testing in early 2015. The system
will be installed within the EOSDIS computer facility and network infrastructure providing a more reliable/redundant environment (power, HVAC, 24–hour on–site emergency
personnel, etc.) and network connectivity; a disaster recovery system will be installed
in a different location on the GSFC campus. The new system location will address thenumber one operational issue CDDIS has experienced over the past several years, namely,
the lack of consistent and redundant power and cooling in its existing computer facility.
Multiple redundant 40G network switches will also be utilized to take full advantage of122

include a listing of sites (or other metadata) or data holdings satisfying the user in
5 Recent Developments
a user interface will also aid CDDIS staff in managing
the contents of the archive.

No. Tbytes
No. Million Files

250

30
200

25
20

150

15

100

10
50

5
0

Number of Million Files

35

Number of Tbytes

Oceania
1%

300

40

Other
16%

North
America
23%

0
Daily

HourlyHigh-Rate

MGEX

Products

Type of GNSS Fileher metadata) or data holdings satisfying the user input specifications. Such
Figure 1: Number and volume of GNSS files transferred from the CDDIS in 2014.
DDIS staff in managing
the contents of the archive.
Figure 1: Number and volume of GNSS files transferredFigure 2: Geographfrom the CDDIS in 2014.
users of the C
Oceania
1%300
No. Tbytes
No. Million Files

5.2
250

Africa0%SouthAmerica
Next Generation Hardware 0%

Number of Million Files

Other
Funding was identified
in 2013 to procure a computer system refresh for the CDD
16%engineer
reviewed current and near-term
requirements and developed a hardware
200
Europe32%with installation beginning in late 20
Hardware was procured in mid-2014
150
completionand testing in early 2015. The system will be installed within the EO
and network infrastructure
providing a more reliable/redundant environment (powNorth
100 emergency America
site
personnel, etc.) and network connectivity; a disaster recovery syste
different location23%
on the GSFC campus. The new system location will address the50
issue
CDDIS has experienced over the past several years, namely, the lack of co
power and cooling in its existingAsia
computer facility. Multiple redundant 40G netwo
28%
0
utilized to take full advantage of a high-performance network infrastructure by uh-Rate MGEX
Products
network paths for all outgoing and incoming streams along with dedicated 10G
GNSS Filebetween its primary operations and its backup operations. The CDDIS will also tr
Figure 2: Geographic distribution of IGS users of the CDDIS in 2014.
85% of its operation services over to virtual machine (VM) technology for both min a loadFigurebalancing
configuration
which willallow additional instances to be incr
me of GNSS files transferred
2: Geographic
distributionof IGS
to demand and users
will ofallow
maintenance(patching, upgrades, etc.) to proceed wit
DIS in 2014.
the CDDIS
in 2014.
user or any downtime. CDDIS will be utilizing a large (XX Tbyte)
storage system123
future growth of the archive.
ardware5.3
Developments
3 to procure a computer
systemMetadata
refresh for the
CDDIS. The CDDIS systemd near-term requirements and developed a hardware procurement strategy.
The CDDIS has recently made modifications to the metadata extracted from inco
mid-2014 with installation beginning in late 2014 and scheduled forfiles pushed to its archive. These enhancements have facilitated cross discipl
y 2015. The system will be installed within the EOSDIS computer facility
providing environment
information (power,
about CDDIS
holdings to other data portals su
oviding a more reliable/redundant
HVAC, archive
24-hour on-

CDDIS Data Centera high–performance network infrastructure by utilizing fully redundant network paths forall outgoing and incoming streams along with dedicated 10G network connections between
its primary operations and its backup operations. The CDDIS will also transition approximately 85% of its operation services over to virtual machine (VM) technology for both
multiple instance services in a load balancing configuration which will allow additional instances to be increased or decreased due to demand and will allow maintenance (patching,upgrades, etc.) to proceed without interruption to the user or any downtime. CDDIS will
be utilizing a large (XX Tbyte) storage system to easily accommodate future growth of
the archive.

5.3 Metadata Developments
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 has implemented Digital Object Identifiers (DOIs) to select IGS data sets(daily GNSS data). DOIs can provide easier access to CDDIS data holdings and allow
researchers to cite these data holdings in publications. Landing pages are available foreach of the DOIs created for CDDIS data products and linked to description pages on
the CDDIS website; an example of a typical DOI description (or landing) page, for daily
Hatanaka–compressed GNSS data files, can be viewed at: http://cddis.gsfc.nasa.
gov/Data_and_Derived_Products/GNSS/daily_gnss_d.html. DOIs will be assigned toadditional GNSS data and product sets in the near future.

6 Publications
The CDDIS staff attended several conferences during 2014 and presented papers on or
conducted demos of their activities within the IGS, including:
C. Noll, P. Michael, N. Pollack, L. Tyahla, “Supporting GGOS through the Crustal Dynamics Data Information System”, Abstract EGU2014–7174 presented at 2014 EGU General Assembly, Vienna Austria, 28 Apr.–02 May.
C. Noll, F. Boler, H. Habrich. “Data Centers: Status and Progress”, presented at IGS
20th Anniversary Workshop, Pasadena CA, 23–27 Jun.

124

7 Future Plans

C. Noll, P. Michael, “Recent Developments at the CDDIS”, presented at IGS 20th Anniversary Workshop, Pasadena CA, 23–27 Jun.
P. Michael, C. Noll, J. Roark. “CDDIS Real–Time Developments”, presented at IGS
20th Anniversary Workshop, Pasadena CA, 23–27 Jun.
C. Noll, P. Michael, N. Pollack. “Recent Developments in Space Geodesy Data Discovery
at the CDDIS”, Abstract IN11C–3623 presented at 2014 Fall Meeting, AGU, San Francisco, Calif., 15–19 Dec.
P. Michael, C. Noll, J. Roark. “CDDIS Near Real–Time Data for Geodesy Based Applications”, Abstract IN43C-3709 presented at 2014 Fall Meeting, AGU, San Francisco,Calif., 15–19 Dec.
Electronic versions of these and other publications can be accessed through the CDDIS on–line documentation page on the web at URL http://cddis.gsfc.nasa.gov/
Publications/Presentations.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 Infrastructure Committee, the Data Center Working Group, andother IGS data centers to develop a transition plan and introduce RINEX V3 data into
the “operational” GNSS data directory structure, making it easier for users to access thesedata.
The CDDIS plans to make its real–time caster operational in the coming year as partof the IGS Real–Time Service. CDDIS staff will work with the IGS to identify stations
for streaming to its caster. Future activities in the real–time area include capturing thestreams for generation of 15–minute high–rate files for archive. This capability requires
further testing as the CDDIS caster becomes operational and data streams from real–timestations are added. The CDDIS staff will need to develop a revised interface software to
the EOSDIS’ next generation URS (version 4). The staff will also automate the processof adding users to the CDDIS caster configuration files.
CDDIS has traditionally used ftp for delivery of data for the archive from both data centers
and analysis centers. While this has worked well over the years, transition to the new
system provides an opportune time time to look at updating this method to a web–based
approach that can utilize the EOSDIS URS infrastructure. CDDIS will investigate thebest methods to incorporate a web–based approach that will continue to allow suppliers
to use existing scripts without significant modification but also tie authentication into the
URS.
125

CDDIS Data Center

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: +1–301–614–6542
Fax:+1–301–614–6015
E–mail: Carey.Noll@nasa.gov
WWW: http://cddis.gsfc.nasa.gov
Website: 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.

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, 2010.
ISSN: 0273–1177, 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.

126Part IV

Working Groups, Pilot Projects

127Antenna Working Group
Technical Report 2014
R. Schmid
Deutsches Geodätisches Forschungsinstitut
der Technische Universität München (DGFI-TUM)
Alfons-Goppel-Str. 11, 80539 München, Germany
E-mail: schmid@tum.de

1 North reference point (NRP)As outlined in IGSMAIL-6987, the Antenna Working Group elaborated a definition of
the so-called north reference point (NRP) that was added to the IGS file antenna.gra(available at ftp://igs.org/pub/station/general) at the end of October 2014. The
NRP designates the element of the antenna that has to be oriented toward the northdirection. There are four major features:• MMI: man-machine interface• NOM: north orientation mark (placed on antenna by manufacturer)• RXC: receiver connector (connect antenna to external receiver)• UNK: unknown

If a north orientation mark (NOM) is present and can be clearly identified, it will usually
be selected to be the NRP. If not, in most cases a receiver connector (RXC) or a manmachine interface (MMI) can serve as the NRP instead. If none of the four major features
is applicable, antenna.gra provides twelve secondary features and connector designations
in order to define the azimuthal antenna orientation.
A considerable amount of time had to be spent on the compilation of the NRP definitions
for all antenna types registered in antenna.gra in accordance with the phase center corrections contained in igs08_wwww.atx on the one hand and further calibrations performedby the IGS calibration institutions on the other hand. In some cases, the NRP definition
had to be harmonized between different institutions. The NRP designator was added both129

Antenna Working Groupto the individual antenna.gra sketches and to the machine-readable section at the end of
the file.
At the beginning of January 2015, antenna.gra contained 201 different antenna types.
For 189 of them, one of the major features was applicable (NOM: 87, MMI: 45, RXC: 43,
UNK: 14). Help on identifying the NRP of outdated or uncalibrated equipment (antenna
types with NRP = UNK) is greatly appreciated.

2 Updates and content of the antenna phase center model
Table 1 lists 11 updates of the absolute IGS antenna phase center model igs08_wwww.atx
that were released in 2014. Eight of them are related to changes of the satellite constellation, and three times an update of the model was released, when new receiver antenna
calibrations became available. Further details on all model changes can be found in thecorresponding IGSMAILs whose numbers are also given in Tab. 1.
Table 2 gives an overview of the data sets contained in the IGS phase center model. The
numbers refer to igs08_ 1822.atx that was released in December 2014. For GPS andGLONASS, there are 83 and 92 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.
At the IGS Workshop 2014 in Pasadena, it was recommended to adopt conventional phasecenter offset (PCO) values for Galileo, BeiDou and QZSS satellite antennas taking into
account the IGS-conventional axis definition related to the yaw-steering attitude mode.
A draft version of igs08_wwww.atx including the new GNSS already exists. It will be
published together with a paper on GNSS satellite geometry and attitude models. For
the time being, conventional PCO values can be found on the web pages of 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 264 different receiver antenna types. 85 of them are certain combinationsof an antenna and a radome, whereas the remaining 179 antenna types are not covered bya radome. As Tab. 2 shows, igs08_ 1822.atx contains, among others, 126 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, altogether 163 different antenna types (126 ROBOT+ 34 COPIED + 3 CONVERTED) are currently approved for installation. The remaining
101 types (90 FIELD + 11 CONVERTED) are no longer allowed, but their calibration values are still necessary for existing installations (see Sect. 3) as well as for reprocessing
purposes.

130

2 Updates and content of the antenna phase center model

Table 1: Updates of the phase center model igs08_ wwww.atx in 2014 (wwww: GPS week of therelease date; Model updates restricted to additional receiver antenna types are only
announced via the IGS Equipment Files mailing list.)
Week

Date

IGSMAIL

1780

21-FEB-14

6866

1781

28-FEB-14—

1785

28-MAR-14

—

1787
1788

08-APR-14
14-APR-14

6895
6899

1793

19-MAY-14

6914

1804

04-AUG-14

6953

1805

11-AUG-14

6955

1808

05-SEP-14

6965

1816

31-OCT-14

6989

1822

10-DEC-14—

ChangeAdded G064, R714 (R18)
Decommission date: G049 (G30), R724
Added TPSPN.A5
NONE
Corrected date: G010
Added TRM55970.00
NONE
Decommission date: G036
Added G049 (G06)
Added R754
Decommission date: R714 (R18)
Added G067
Decommission date: G049 (G06)
Added STXS9+X001A
NONE
Added G068, R755
Decommission date: G039, R725
Added AERAT1675_ 120
SPKE
Corrected date: R725, R755
Added LEIGG03
NONE
Added G035 (G03)
Decommission date: G033
Added G069
Decommission date: G035 (G03)
Corrected NRP: JAV_ GRANT-G3T
NONE
Corrected name: STXS9PX001A
NONE
Added JAVTRIUMPH_ 1M
NONE
JAVTRIUMPH_ 1MR NONE
JAVTRIUMPH_ 2A
NONE
JAVTRIUMPH_ LSA NONE

Table 2: Number of data sets in igs08_ 1822.atx (released in December 2014)
Satellite antennas
GPS
GLONASS
Galileo
BeiDou
QZSS

Number83
92
0
00Receiver antennas
ROBOT
FIELD
COPIEDCONVERTED

Number
126
90
34
14

131

Antenna Working Group
Table 3: Calibration status of 452 stations in the IGS network (logsum.txt of 9 January 2015,
igs08_ 1822.atx) compared to former years

Dates
DEC 2009
MAY 2012
JAN 2013
JAN 2014
JAN 2015

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%
80.1%

18.3%
8.2%
7.7%
7.8%
7.5%

20.2%
17.2%
15.5%
13.5%
12.4%

3 Calibration status of the IGS network
Table 3 shows the percentage of IGS tracking stations with respect to certain calibration
types. For this analysis, 452 IGS stations as contained in the file logsum.txt (available
at ftp://igs.org/pub/station/general) on 9 January 2015 were considered. At thattime, 102 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_ 1822.atx that was released in December 2014.
Eight 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 about 80% of all IGS stations. Whereas the portion of stations
with phase center corrections derived from relative field calibrations (purely elevationdependent) hardly changed in recent years, a steady decrease of IGS stations covered byuncalibrated 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”.

132Bias & Calibration Working Group
Technical Report 2014
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 2014
• 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. Temporal resolution for global ionosphere modeling wasincreased at CODE in 2014 (from 2 to 1 hour).

133

Bias and Calibration Working Group5

BLOCK IIABLOCK IIR−M

BLOCK IIF

BLOCK IIR−ABLOCK IIR−B

3
2
1
0
−1
−2
−3
−4

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

DCB(p1c1) in ns

4−5

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

20BLOCK IIABLOCK IIR−M

BLOCK IIFGLONASS−M

BLOCK IIR−ABLOCK IIR−B

10
5
0
−5
−10
−15

G04
G08
G10
G26
G32
G01
G03
G06
G09
G24
G25
G27
G30
G11
G13
G14
G16
G18
G20
G21
G28
G02
G19
G22
G23
G05
G07
G12
G15
G17
G29
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 December 2014, computed at CODE.

134

2 Activities in 2014

DCB(p1p2) in ns

60

AOA BENCHMARK ACT
ASHTECH Z−XII3TJPS EGGDTLEICA GR25
NOV OEM4−G2
SEPT POLARX4TPS LEGACYTPS ODYSSEY_E
TRIMBLE NETR8AOA SNR−12 ACT
JAVAD TRE_G3T DELTA
JPS E_GGD
LEICA GRX1200+GNSSNOV OEMV3SEPT POLARX4TR
TPS NET−G3
TRIMBLE 4000SSITRIMBLE NETR9ASHTECH UZ−12
JAVAD TRE_G3TH DELTA
JPS LEGACYLEICA GRX1200GGPROSEPT POLARX2TPS EUROCARDTPS NET−G3A
TRIMBLE 5700
TRIMBLE NETRSASHTECH Z−XII3
JAVAD TRE_G3TH SIGMA
LEICA GR10
LEICA GRX1200PROSEPT POLARX3ETRTPS E_GGD
TPS NETG3
TRIMBLE NETR5

40
20
0
−20
−40
−60

Stations

DCB(p1p2) in ns

60

AOA BENCHMARK ACT
ASHTECH Z−XII3TJPS EGGDTLEICA GR25
NOV OEM4−G2
SEPT POLARX4TPS LEGACYTPS ODYSSEY_E
TRIMBLE NETR8AOA SNR−12 ACT
JAVAD TRE_G3T DELTA
JPS E_GGD
LEICA GRX1200+GNSSNOV OEMV3SEPT POLARX4TR
TPS NET−G3
TRIMBLE 4000SSITRIMBLE NETR9ASHTECH UZ−12
JAVAD TRE_G3TH DELTA
JPS LEGACYLEICA GRX1200GGPROSEPT POLARX2TPS EUROCARDTPS NET−G3A
TRIMBLE 5700
TRIMBLE NETRSASHTECH Z−XII3
JAVAD TRE_G3TH SIGMA
LEICA GR10
LEICA GRX1200PROSEPT POLARX3ETRTPS E_GGD
TPS NETG3
TRIMBLE NETR5

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 December 2014, computed at CODE.

135

Bias and Calibration Working Group• 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).
• In June 2014, we started to produce GNSS DCB result files from our clock andionosphere analysis lines in bias-SINEX format (preliminary version 0.01).
• The ambiguity resolution scheme at CODE was extended (in 2011) 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 are collected 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).
• 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/y2014/odata2_d335.txt
ftp://ftp.unibe.ch/aiub/igsdata/y2014/odata2_d335_sat.txt
Internally, the corresponding information is extracted and produced using metadata
stored in an xml database (established in December 2014). The switch to this xmlbased data monitoring did not affect the provided RINEX summaries.
• This RINEX monitoring service is provided in addition for MGEX observation data(available in RINEX3 format). See ftp://ftp.unibe.ch/aiub/mgex/y2014/.

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.

136

3 Last Reprocessing Activities

5

BLOCK IIABLOCK IIR−M

BLOCK IIFGLONASS−M

BLOCK IIR−ABLOCK IIR−B

3
2
1
0
−1
−2
−3
−4

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

4−5

Satellites

BLOCK IIR−M

GLONASS−M

5

0

−5

G01
G03
G06
G09
G24
G25
G27
G30
G05
G07
G12
G15
G17
G29
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

BLOCK IIF

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

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Bias and Calibration Working Group

DCB(p1c1) in ns

AOA BENCHMARK ACT
ASHTECH Z−XII3T
JAVAD TRE_G3TH SIGMASEPT POLARX2TPS EUROCARDTPS NET−G3
TRIMBLE NETR5AOA SNR−12 ACTDICOM GTR50
JPS EGGDTSEPT POLARX3ETRTPS E_GGD
TPS NET−G3A
TRIMBLE NETR8ASHTECH UZ−12
JAVAD TRE_G3T DELTA
JPS E_GGD
SEPT POLARX4TPS GB−1000
TPS NETG3
TRIMBLE NETR9ASHTECH Z−XII3
JAVAD TRE_G3TH DELTA
JPS LEGACYSEPT POLARX4TR
TPS LEGACYTPS ODYSSEY_E
TRIMBLE NETRS

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

Stations

DCB(p1c1) in ns

AOA BENCHMARK ACT
ASHTECH Z−XII3T
JAVAD TRE_G3TH SIGMASEPT POLARX2TPS EUROCARDTPS NET−G3
TRIMBLE NETR5AOA SNR−12 ACTDICOM GTR50
JPS EGGDTSEPT POLARX3ETRTPS E_GGD
TPS NET−G3A
TRIMBLE NETR8ASHTECH UZ−12
JAVAD TRE_G3T DELTA
JPS E_GGD
SEPT POLARX4TPS GB−1000
TPS NETG3
TRIMBLE NETR9ASHTECH Z−XII3
JAVAD TRE_G3TH DELTA
JPS LEGACYSEPT POLARX4TR
TPS LEGACYTPS ODYSSEY_E
TRIMBLE NETRS

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 December 2014, computed at CODE.

138

3 Last Reprocessing Activities

JAVAD TRE_G3T DELTA
LEICA GRX1200+GNSSTPS NET−G3
TRIMBLE NETR8JAVAD TRE_G3TH DELTA
SEPT POLARX3ETRTPS NET−G3A
TRIMBLE NETR9LEICA GR10
SEPT POLARX4TPS NETG3
TRIMBLE NETRSLEICA GR25
SEPT POLARX4TR
TRIMBLE NETR5

3

DCB(p2c2) in ns

2
1
0
−1
−2
−3
−4
−5
−6
−7

Stations
JAVAD TRE_G3T DELTA
LEICA GRX1200+GNSSTPS NET−G3
TRIMBLE NETR8JAVAD TRE_G3TH DELTA
SEPT POLARX3ETRTPS NET−G3A
TRIMBLE NETR9LEICA GR10
SEPT POLARX4TPS NETG3
TRIMBLE NETRSLEICA GR25
SEPT POLARX4TR
TRIMBLE NETR5

3

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 December 2014, computed at CODE.

139

Bias and Calibration Working Group

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 2013, Astronomical Institute, University of Bern, May
2014, pp. 137–143.

140

Data Center Working Group
Technical Report 2014
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
The DCWG met in conjunction with the Multi–GNSS Experiment (MGEX) Working
Group during the 2014 IGS Workshop in Pasadena, CA in June 2014. The main issues
discussed at this DCWG splinter meeting revolved around supporting RINEX V3 andintegrating the MGEX archive of data in RINEX V3 format into the operational IGS
archives at the DCs. Two main topics were addressed: merging RINEX V3 data into thearchives and accepting data using the new RINEX V3 filename format.
The current parallel structure found at the DCs supporting MGEX limits the motivationof the ACs to switch to the RINEX V3 format. Integration of the two data archives will
promote use of multi–GNSS data and the new format. The MGEX Working Group hassuggested development of a transition plan for adding the MGEX data, and hence RINEX
V3 data, to the operational archives. Participants agreed that members of the IGS infrastructure (DCs, the IC, ACs, etc.) should develop this transition plan. It was proposed

141

Data Center Working Groupto include three six–month phases: a preparation phase, followed by an implementation
phase and a finalization phase, with full integration of RINEX V3 into the archives by theend of 2015. RINEX V2 for MGEX stations and stations capable of generating RINEX
V3 would end at this time.
Those ACs attending the DCWG meeting agreed to utilize the filename convention specified in the RINEX V3 documentation. The DCs, however, will need software tools tocreate these new filenames from RINEX V2 filenames until stations and receiver manufacturers can create the new filenames directly. Tools also need to be made available to
the DCs for data QC and metadata extraction as well as tools for the ACs and users toconvert RINEX V3 to RINEX V2.
The RINEX V3 format should also address navigation files. The current format documentation specifies one file per station for observation data; therefore, the format should
specify one file per station that includes navigation messages from all GNSS constellations.
A tool may need to be developed for this capability rather than depend upon generationin the receiver.
The following recommendations were generated from the June 2014 DCWG meeting:
1. Develop a transition plan that will integrate RINEX V3, including the V3 filename
convention, into the operational IGS archives by the end of 2015. (IC, DCs, ACs,
MGEX WG)– Progress: The IGS Infrastructure Committee has drafted this transition plan forcomment. The plan works toward the “one network one archive” concept, merging
the RINEX V2 and V3 files currently maintained in separate structures at the data
centers, into one archive structure. The IC has recommended the IGS Governing
Board provide guidance on next steps.
2. Provide software tools that DCs can use to continue to provide needed QC andmetadata extraction enabling creation of data status information.
– Progress: Possible tools have been discussed but not identified for general use
through the IGS infrastructure.
3. Provide software tools to support data conversion (e.g., RINEX V3 to RINEX V2.
RINEX V3 filename creation) that both DCs and ACs can use.
– Progress: The transition plan has identified the need for these tools.
The above recommendations reiterate those from the 2012 IGS Analysis Workshop:
1. The DCs recommend continuing the efforts by the Infrastructure Committee andthe RINEX WG to agree on new file names.
– Progress: The new filename convention is included in the RINEX V3 transition
plan. To date, RINEX V3 data utilized in support of MGEX are archived at data
centers (CDDIS and IGN) in separate directory structures. To improve/encouragedata access and usage, the RINEX V3 transition plan states the DCs will use the1423 Future Plans
new filenames and incorporate RINEX V3 data within the operational directory
structure.
2. Until the RINEX V3 filename convention is finalized, separate directories for distinguishing between files created from streams and by receivers will be established by
all DCs.
– Progress: The DCWG has not addressed this recommendation to archive of high–rate files from real–time streams vs. receivers. However, the RINEX V3 filename
convention has been finalized and is included in the latest RINEX V3 documentation.
With the adoption of the proposals outlined in the RINEX V3 transition plan,stream–created data will be clearly identified by filename.
3. All DCs explore transition options for a follow on compression scheme to replace
UNIX “compress” as early as possible.
– Progress: IGS users reported to DCs that the decompression tools for UNIX
compress (“.Z”) is an outdated method for data compression. It is recommended
that the IGS infrastructure change to a standard compression format as early as
possible. Plans for transition from UNIX compress to another compression scheme,e.g., gzip, will be coordinated with testing of RINEX V3 data flow.

3 Future Plans
One topic discussed at the IGS Infrastructure Committee meeting at the 2014 IGS Workshop involved metadata, particularly in the area of site logs. The IGS CB has introduced
the Site Log Manager System, which is utilized at the IGS Central Bureau for handling
IGS site logs and provides a basis for promoting the transmission of these logs in XML format. An XML/database management approach to site logs provides several advantages,
such as rapid update of site log contents, utilization of consistent information across data
centers, and availability of more accurate station metadata. The IGS CB and UNAVCO,
in conjunction with the DCWG, are proposing email discussions and/or telecons to allow
participants in this effort to collaborate and plan for a way forward in design, development, and implementation of a shared geodesy XML schema, possibly utilizing the site log
schema developed at SOPAC, for site information. If feasible the group would like to planfor future meetings on this collaboration, perhaps in conjunction with community–held
meetings (e.g., EGU, AGU, IGS workshops, etc.).
The DCWG will also work with the IGS DCs to implement the recommendations developed
during the 2012 and 2014 workshops. In particular, the DCWG will work with the MGEX
Working Group and the Infrastructure Committee to finalize the RINEX V3 Transition
Plan and work toward implementing the plan itself. Additional topics the WG hopes toaddress follow.

143

Data Center Working Group• 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.
• RINEX file naming convention: The DCWG will work with the IC and the RINEXWG on implementation of 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.
• Compression: As per a recommendation from past IGS 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, and coordinating
recommendations with the IC to develop implementation schedule. Ideally, the newcompression scheme will be made part of the RINEX V3 file naming implementation.
• Next meeting: A meeting of the DCWG is planned for the next IGS workshop in
2016.

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

144

Ionosphere Working Group
Technical Report 2014
A. Krankowski1 I. Cherniak1 , I. Zakharenkova1 ,R. Langley2 , M. D. Butala3 , A. Komjathy3 ,T. F. Runge3 , B. D. Wilson3 , X. Pi3 , A. J. Mannucci3 ,M. Hernandez–Pajares4 , P. Vergados3 ,12
3
4

Space Radio–Diagnostics Research Center
University of Warmia and Mazury in Olsztyn, Poland (SRRC/UWM)
Geodesy and Geomatics Engineering, University of New Brunswick, Canada
Jet Propulsion Laboratory, California Institute of Technology
IONSAT, Universitat Politecnica de Catalunya (UPC), Barcelona, Spain

1 Introduction
The Ionosphere Working group started the routine generation of the combined 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 are used by each analysis center: Each IAAC compute the rapid and final TEC maps independently and with different approaches including the additional usageof GLONASS data in the case of CODE.

2 Membership
The members of the ionosphere working group are listed in Tab. 1. Dr. Reza Ghoddousi–
Fard, from the Canadian Geodetic Survey of Natural Resources Canada (NRCan), hassolicited to be a member of the IGS Ionosphere WG. Taking into account that all of145

Ionosphere Working Group
Table 1: Members of the ionosphere working group
MemberAffiliation

MemberAffiliation

Dieter Bilitza
Ljiljana R. Cander
M. Codrescu
Anthea Coster
Patricia H. Doherty
John Dow
Joachim Feltens
Mariusz Figurski
Alberto Garcia–Rigo
Manuel Hernandez–Pajares
Pierre Heroux
Norbert Jakowski
Attila Komjathy
Andrzej Krankowski
Richard B. Langley
Reinhard Leitinger
Maria Lorenzo

GSFC/NASA
RAL
SEC
MIT
BC
ESA/ESOC
ESA/ESOC
MUT
UPC
UPC
NRCAN
DLR
JPL
UWM
UNB
TU Graz
ESA/ESOC

A. Moore
Raul Orus
Michiel Otten
Ola Ovstedal
Ignacio Romero
Jaime Fernandez Sanchez
Stefan Schaer
Javier Tegedor
Rene Warnant
Robert Weber
Pawel Wielgosz
Brian Wilson
Michael Schmidt
Mahdi Alizadeh
Reza Ghoddousi–Fard

JPL
UPC
ESA/ESOC
UMB
ESA/ESOC
ESA/ESOC
CODE
ESA/ESOCROB
TU Wien
UWM
JPL
DGFI
TU Vienna
NRCan

opinions about Dr. Ghoddousi–Fard’s membership application have been positive, we areglad to welcome Dr. Ghoddousi–Fard to the WG.

3 Products• 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 2 hours × 5 deg. × 2.5 deg. (UTxLon.×Lat.),– availability with a latency of 11 days

• Rapid GIM– combination of CODE, ESA, JPL and UPC iono products conducted by UWM– temporal and spatial resolution – at 2 hours × 5 deg. × 2.5 deg. (UT×Lon.×Lat.),– availability with a latency of less than 24 hours• Predicted GIM for 1 and 2 days ahead (pilot product)146

6 Announcements after IGS Workshop 2014, Pasadena, USA– combination of ESA and UPC iono products conducted by ESA– temporal and spatial resolution – at 2 hours × 5 deg. × 2.5 deg. (UTxLon.×Lat.),

4 Key accomplishments• IGS Global ionosphere predicted products for 1 and 2 days ahead (pilot product).
These new IGS products are currently based on predicted ionosphere maps preparedby UPC and ESA.
• IGS Global ionosphere maps with 1 hour time resolution. These new IGS products
are currently based on ionosphere maps prepared by UPC, ESA and CODE.
• IGS Global Ionosphere Maps (GIMs) now include differential code biases (DCBs)
for GLONASS satellites.
• The pilot phase of the new IGS ionospheric product – TEC fluctuation maps

5 Recommendations after IGS Workshop 2014, Pasadena,
USA• Higher temporal resolution of IGS combined GIMs – the IAACs (UPC, JPL, ESA
and CODE) agreed on providing their maps in IONEX format, with a resolution of
1 hour from 2015.
• Starting a new potential official product – TEC fluctuation maps using ROTI over
the Northern Hemisphere to monitor the dynamic of oval irregularities (carried out
by UWM; Krankowski), JPL (Pi) and UPC (Hernandez–Pajares) in the future to be
started as official/routine product after performance evaluation period (beginning2015).
• Close cooperation with National Central University from Taiwan regarding usageof occultation measurements from Formosat/Cosmic mission for future validation of
IGS GIMs.
• Cooperation with IRI COSPAR group for improving IRI TEC.

6 Announcements after IGS Workshop 2014, Pasadena, USA• Natural Resources Canada (NRCan) is resuming the activities on global VTEC
modelling. After a performance evaluation period, NRCan can again become an
IAAC (Reza Ghoddousi–Fard, April 2015).

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Ionosphere Working Group

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).

• The Institute of Geodesy and Geophysics (IGG), Chinese Academy of Sciences,
Wuhan, China (Yunbin Yuan, beginning 2015) is computing on a routine basis global
VTEC maps, and it can become a new IAAC after a performance evaluation period(Yunbin Yuan).
• A new proposed format (SCINTEX) for slant ionospheric information (such as S4,
sigmaPhi, ROT and STEC) has been recently proposed and is under considerationin the IGS ionospheric community due to its significance for potential applications.

7 The pilot phase of the new IGS ionospheric product– TEC fluctuation maps; Space Radio–Diagnostics Research Center,
University of Warmia and Mazury in Olsztyn, Poland (SRRC/UWM)
According to the resolution of the IGS Ionosphere Working Group, which was passed
during the IGS Workshop 2014 in Pasadena, the new product – the ionospheric fluctuation
maps – was established as a pilot project of the IGS service. Due to small changes in solar
irradiance levels and various geophysical parameters in the atmosphere and ionosphere,
TEC fluctuations are calculated as a function of a spherical geomagnetic latitude andmagnetic local time.

148

8 JPL Ionospheric Analysis Center Technical Report Contribution for 2014

Figure 3: Evolutions of the daily ROTI maps for 30 May – 4 June 2013.

In the updated version of the product, more than 700 permanent stations (available bothfrom UNAVCO and EUREF databases) have been incorporated into the analysis of theionosphere 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 a 5–minute periods with 1–minuteresolution. This ionospheric fluctuation service allows the estimation of the levels of TEC
fluctuations levels from 50 degrees to the pole (in geomagnetic coordinates). The results
are shown a visualization as daily ROTI maps in polar coordinates on a uniform 2 degree(magnetic local time) and 2 degree (geomagnetic latitude) grid. Every grid cell represents
the weighted ROTI values included in the cell.
The final TEC fluctuation maps are written in a modified IONEX format. ROTI data are
stored in ASCII format based on a grid of 2 by 2 degrees – geomagnetic latitude from 89
degrees to 51 degrees with step 2 and corresponding to magnetic local time (00–24 MLT)
along with polar coordinates from 0 to 360 degrees (Cherniak et al. 2014b, c).

8 JPL Ionospheric Analysis Center Technical Report
Contribution for 2014
The Jet Propulsion Laboratory (JPL) continued its role as an Ionospheric Associate Analysis Center (IAAC) for the International Global Navigation Satellite System (GNSS) Service

149

Ionosphere Working Group

Figure 4: The sample of ROTI–ex format body.

(IGS) in 2014. The primary objective was the retrieval, analysis and validation of GIM
products at the daily basis (Mannucci et al. 1998) and their deliveries to the NASA Crustal
Dynamics Data Information System (CDDIS). These maps were generated in IONEX format (Schaer et al. 1998) and include daily estimates of GPS satellite and ground–based
receiver DCBs, as well as 2.5◦ latitude by 5◦ longitude by 2 hour IGS standard resolution
vertical TEC (VTEC) maps. The continued deliveries of rapid and final IONEX maps
have been one of our highest priorities. In addition to our primary objective, we began modifying our software to incorporate additional GNSS signals of opportunity, suchas those provided by the GLONASS constellation. As a result, we investigated JPL’s
GIM performance upon including the additional signals, which fall within the activities of
IAAC. Preliminary results are shown below.

8.1 JPL Global Ionosphere Maps
Table 2 lists the JPL GIM products delivered daily by JPL to the CDDIS in 2014. The
maps are routinely derived using slant total electron content (STEC) arcs measured bycarrierŰphase and pseudorange ionospheric TEC observables gathered from approximately
200 sites globally, distributed as uniformly as possible, from available dual–frequency GPS
receivers in the IGS network. Both rapid and final JPL IONEX products are available
every day in 2014 and we will continue to deliver timely, and high–quality GIM products
to the CDDIS in 2015 and beyond.

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8 JPL Ionospheric Analysis Center Technical Report Contribution for 2014
Table 2: JPL AC IONEX Contributions Delivered to the CDDIS
Product
jplrJJJ0.YYi.Z
jplgJJJ0.YYi.Z

Description
Rapid (i.e., 1–day delay), GPS–derived, daily ionospheric map
Final (i.e., 3–day delay), GPS–derived, daily ionospheric map

8.2 GLONASS Impact on GIM
Numerous ground–based receivers have the capability to track both GPS and GLONASS
satellites, offering a denser set of TEC measurements for remotely sensing the ionosphere. To assess the impact of GLONASS observables on JPL GIM performance, we
conducted the following experiment. First, we estimated 2D gridded VTEC maps using
only GPS observables, and second we generated 2D gridded VTEC maps using both GPS
and GLONASS observables. Preliminary results from Butala et al. 2014 demonstrated apositive impact of GLONASS on JPL GIM products as summarized below. Despite thisconclusion, we note that there may exist inconsistencies between the GPS and GLONASS
data sets and further investigation and analyses are required. Based on our initial results,
JPL plans to integrate GLONASS measurements into our standard GIM products in 2015,
accompanied by an investigation of the contribution of GLONASS observations to GIM.
Figure 5 shows the GIM–derived receiver bias estimates at the IGS station in Brasilia(BRAZ, –15.94◦ N, –47.88◦ E) as a function of time in May 2014. Two cases are considered: using GPS data alone in red, and using GPS plus GLONASS measurements inblue. Note the GPS+GLONASS (blue) derived station biases are slightly more repeatable, exhibiting a smaller standard deviation compared to using GPS (red) data alone.
The decrease in standard deviation is more striking given the increase in unknown receiverbias parameters required to process the GLONASS data, one for each receiver and satellite
pair as opposed to only one for each receiver in the GPS only case. We plan to investigate
additional stations and monitor the behavior of the standard deviation to provide additional quality assessment of the products. Figure 6 displays a comparison of JPL GIM
VTEC to VTEC measured by an independent data source, in this study the space–borne
dual–frequency ocean altimeter Ocean Surface Topography Mission (OSTM or Jason–2,
see the OSTM/Jason–2 Products Dumont et al. 2009 or Tseng et al. 2010). The bar
chart shows the consistent and sometimes significant improvement between Jason–2 andcombined GPS and GLONASS GIM day–time VTEC. We note that the results seem spatially biased compared to the Jason–2 orbital tracks in ocean regions that are typicallyareas of generally sparser GNSS receiver coverage. In addition, Jason–2 may have its own
instrumental bias that must be accounted for in the VTEC comparison (Hausman and
Zlotnicki 2010). We will continue to analyze GLONASS observables and their impact on
GIM products.

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Figure 5: JPL GIM bias time–series for station BRAZ derived for GPS data alone (GPS) andcombined GPS and GLONASS data (GPS+GLONASS) for May, 2014. Data were notavailable for May 3–6. Note the decreased station bias standard deviation (std) in the
GPS+GLONASS result.

Figure 6: Day–time root mean square (RMS) of the difference between measured Jason–2 VTEC
and JPL GIM VTEC derived from GPS alone (red) and combined GPS and GLONASS
data (green). Each bar annotation indicates the daily improvement in the day–time
VTEC difference RMS. Note the consistent and often significant improvement of the
GPS and GLONASS GIM VTEC compared to that measured by an independentsource.

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9 Ionosphere–Related Work by Personnel Affiliated with UNB

9 Ionosphere–Related Work by Personnel Affiliated with
UNB
Activity during 2014 included development of an improved ionospheric modelling techniqueusing GPS and empirical–orthogonal–function fits. This work is an attempt to makeestimated ionospheric parameters more physically meaningful and effective. The approach
uses data–driven empirical orthogonal functions (EOF) to replace arbitrary functions tomatch better the horizontal variability of the ionosphere and estimate inter–frequency
hardware biases with the EOF–fit ionosphere representation. This modelling technique
has been implemented in both 2D and 3D scenarios and assessed with data from a regional
GPS network. It was demonstrated with the network that the approach can give better
results in terms of lower residuals compared to the standard UNB technique. Comparisonsof the outputs of the approach with independent data sources are ongoing.
Work was also carried out on the use of global and regional ionospheric corrections forfaster convergence of precise point positioning (PPP). It was demonstrated that the use ofboth global ionosphere maps and ambiguity resolution can potentially reduce the convergence time of PPP to 10–cm horizontal accuracies from 30 to 4.5 minutes (68th percentile),
under favourable ionospheric conditions. However, instantaneous ambiguity resolution
could not be achieved using ionosphere maps based on the single–layer model, and ionospheric corrections from a regional network in the form of slant delays were required forthis purpose.
In collaboration with colleagues at the Jet Propulsion Laboratory, UNB participated inseveral ionosphere–related investigations. Radio occultation data provided by UNB’s GPS
Attitude, Positioning, and Profiling (GAP) instrument, one of several making up the Enhanced Polar Outflow Probe (e–POP) platform on the Canadian CASSIOPE satellite,
has been used to study intermediate–scale plasma density irregularities in the polar ionosphere. In another study, ground–based GPS measurements have been used to study
the ionospheric impact of the 2013 Chelyabinsk asteroid’s entry into the Earth’s atmosphere. And in yet another work, ionospheric disturbances caused by the 2011 Tohoku–Oki
Earthquake have been detected at a height of 450 km using total electron content and atmospheric density perturbations derived from measurements made from instruments onboard the Gravity Recovery and Climate Experiment (GRACE) spacecraft.
In collaboration with colleagues at the University of Calgary, the relationship between
aurora and the phase scintillation index (sf) has been investigated. A possible relation
between the “phase scintillation without amplitude scintillation” phenomenon observed
at high latitudes and GPS phase fluctuations during aurora has been hypothesized. It
is shown that under–estimating the Fresnel frequency during auroral periods is causing
observation of “phase scintillation without amplitude scintillation” at auroral latitudes.
Initial investigations have also been carried out on the effect of “patchy pulsating aurora”
and auroral arcs on GPS signals. It is seen that patchy pulsating aurora, given its larger

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Ionosphere Working Groupspatial extent, affects GPS signals in a more pronounced manner than auroral arcs.

10 Publications 2014
1. Banville, S., P. Collins, W. Zhang, R.B. Langley, Global and Regional Ionospheric
Corrections for Faster PPP Convergence, NAVIGATION: Journal of the Institute of Navigation, 61(2):115–124, doi:10.1002/navi.57.
2. Bilitza, D., Altadill, D., Zhang, Y., Mertens, Ch., Truhlik, V., Richards, P., McKinnell, L–A, Reinisch, B., 2014, The International Reference Ionosphere 2012 – a model ofinternational collaboration. J. of Space Weather and Space Clim, Vol. 4, AO7, 2014.
3. Cherniak, Iu., Zakharenkova, I.E., Dzubanov, D., Krankowski, A., 2014a, Analysisof the ionosphere/plasmasphere electron content variability during strong geomagnetic
storm, Advances in Space Research, 54(4):586–594, 2014.
4. Cherniak, Iu., Krankowski, A., Zakharenkova, I.E., 2014b, Observation of the ionospheric irregularities over the Northern Hemisphere: Methodology and Service, Radio
Science, 49:653–662, 2014, DOI: 10.1002/2014RS005433.
5. Cherniak, Iu., Zakharenkova, I.E., Krankowski, A., 2014c, The approaches for theionosphere irregularities modeling on the base of ROTI mapping, Earth, Planets andSpace (EPS) 66:165, 2014, doi:10.1186/s40623-014-0165-z
6. Frappart, F., N. Roussel, R. Biancale, J.J. Martinez–Benjamin, F. Mercier, F. Pérosanz,
J. Garate–Pasquin, J. Martin–Davila, B. Perez–Gomez, C. Gracia–Gomez, R. Lopez–
Bravo, A. Tapia–Gomez, J. Gili–Ripoll, M. Hernandez–Pajares, M. Salazar–Lino, P. Bonnefond, I. Valles–Casanova, 2015, The 2013 Ibiza calibration campaign of Jason–2 andSaral altimeters, Marine Geodesy, in press.
7. Gulyaeva, T.L., Arikan, F., Hernandez–Pajares, M., and Veselovsky, I.S., 2014, North–south components of the annual asymmetry in the ionosphere. Radio Science, 49(7):485–
496.
8. Hernández–Pajares, M., Ã. Aragón–Ángel, P. Defraigne, N. Bergeot, R. Prieto–Cerdeira,and A. García-Rigo, 2014, Distribution and mitigation of higher–order ionospheric effects on precise GNSS processing, J. Geophys. Res.: Solid Earth, 119(4):3823–3837,
doi:10.1002/2013JB010568.
9. Li, Z., Yuan, Y., Wang, N., Hernandez-Pajares, M., and Huo, X., 2014, SHPTS: towards
a new method for generating precise global ionospheric TEC map based on sphericalharmonic and generalized trigonometric series functions. Journal of Geodesy, 89(4):331–
345.
10. Limberger, M., Liang, W., Schmidt, M., Dettmering, D., Hernández-Pajares, M., andHugentobler, U., 2014, Correlation studies for B–spline modeled F2 Chapman parameters154

11 Presentations/Posters/Meeting Proceedings 2014
obtained from FORMOSAT–3/COSMIC data. Ann. Geophys, 32:1533–1545.
11. Monte, E., Hernandez-Pajares, M., 2014, Occurrence of solar flares viewed with GPS:
Statistics and fractal nature, Journal of Geophysical Research: Space Physics, 119(11):9216–
9227.
12. Yang, Y.-M., A. Komjathy, R.B. Langley, P. Vergados, M.D. Butala, and A.J. Mannucci, The 2013 Chelyabinsk Meteor Ionospheric Impact Studied Using GPS Measurements, Radio Science, 49(5):341–350, doi:10.1002/2013RS005344. Paper featured on issue
cover.
13. Yang, Y.-M., X. Meng, A. Komjathy, O. Verkholyadova, R.B. Langley, B.T. Tsurutani, and A.J. Mannucci, 2014, Tohoku-Oki Earthquake Caused Major Ionospheric Disturbances at 450 km Altitude over Alaska, Radio Science, 49(12):1206–1213.
14. Zakharenkova, I., Cherniak, Iu., Krankowski, A., Shagimuratov, I.I., 2014a, Cross–hemisphere comparison of mid–latitude ionospheric variability during 1996–2009: Juliusruh vs. Hobart, 2014, Advances in Space Research, 53(2):175–189.
15. Zakharenkova, I.E., Cherniak, Iu., Krankowski, A., Shagimuratov, I.I., 2014b, Vertical
TEC representation by IRI 2012 and IRI Plas models for European midlatitudes, Advancesin Space Research, 55(8):2070–2076.
16. Zhang, W., A. Komjathy, S. Banville, and R.B. Langley, Ionospheric Modeling Using
GPS: Greater Fidelity Using a 3D Approach, GPS World, 25(2):59–65.

11 Presentations/Posters/Meeting Proceedings 2014
1. Mushini, S. E. Donovan, P.T. Jayachandran, R. Langley, P. Prikryl, and E. Spanswick,“On the Relation Between Auroral ”Scintillation“ and ”Phase Without Amplitude" Scintillation: Initial Investigations, Canadian Association of Physicists Division of Atmosphericand Space Physics Winter Workshop, Fredericton, NB, 19–21 February 2014.
2. Krankowski A., Cherniak Iu., Zakharenkova I., 2014, Current and future IGS Iono WG
activities, Workshop “Ionospheric research and applications at the ICTP and East Europe”
ICTP Telecommunications/ICT for Development Laboratory (T/ICT4D), 25 April 2014,
Trieste, Italy, (solicited).
3. Krankowski A., Cherniak Iu., Zakharenkova I.E., 2014, GNSS monitoring of the ionospheric irregularities over the Northern Hemisphere for Space Weather applications, XI
General Assembly of the EUG, Vienna, Austria, 27 April – 02 May 2014
4. Rothkaehl H., Krankowski A., Morawski M., Atamaniuk B., Zakharenkova I.E, Cherniak Iu., 2014, New advanced netted ground based and topside radio diagnostics for Space
Weather Program, XI General Assembly of the EUG, Vienna, Austria, 27 April – 02 May
2014

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5. Shagimuratov I.I., Cherniak Iu., Zakharenkova I.E., Ephishov I., Krankowski A.,
Radievsky A., 2014, The mapping of ionospheric TEC for central Russian and European regions on the base of GPS and GLONASS measurements, XI General Assembly of
the EUG, Vienna, Austria, 27 April – 02 May 2014
6. Krankowski A., Cherniak Iu., Zakharenkova I., 2014, Current and future IGS Iono WG
activities, new IGS iono product – monitoring of TEC fluctuations, IGS Workshop 2014,
June 23–27, 2014, Pasadena, California, USA, (solicited).
7. Krankowski A., Rothkaehl H., Cherniak Iu., Zakharenkova I., Otmianowska–Mazur
K., Soida M., 2014, LOFAR as new advanced radio diagnostics tools for Space Weather
Program, IGS Workshop 2014, June 23–27, 2014, Pasadena, California, USA.
8. Cherniak Iu., Krankowski A.,Zakharenkova I., 2014, Observation of the ionosphericirregularities over the Northern Hemisphere: Methodology and Service, IGS Workshop
2014, June 23–27, 2014, Pasadena, California, USA.
9. Cherniak Iu., Krankowski A., Zakharenkova I., Shagimuratov I., 2014, Validation of
the IRI model by multiinstrumental radiophysical observations, 40th COSPAR Scientific
Assembly, August 02–10, 2014. Moscow, Russia, (solicited).
10. Cherniak Iu., Krankowski A., Zakharenkova I., Shagimuratov I., 2014, The development of approaches for ionosphere irregularities modeling on the base of GNSS data, 40th
COSPAR Scientific Assembly, August 02–10, 2014. Moscow, Russia.
11. Gordon, J., A. Yau, R. Langley, and P. Bernhardt, “First Results from the Radioscience
Instruments on CASSIOPE/e–POP,” presentation to 40th COSPAR Scientific Assembly,
Moscow, 2–10 August 2014, abstract #C1.3–21–14.
12. Zakharenkova I., Cherniak Iu., Krankowski A., Shagimuratov I., 2014, Analysis of
the TEC representation by IRI model, 40th COSPAR Scientific Assembly, August 02–10,
2014. Moscow, Russia, (solicited).
13. Rothkaehl H., Krankowski A., Morawski M., 2014, New Advanced radio tools formonitoring and diagnostics near plasma environment, 2014, 31st URSI General Assembly and Scientific Symposium (31st URSI GASS), 16–23 August 2014, Beijing, China,(solicited).
14. Zakharenkova I., Cherniak Iu., Krankowski A., Shagimuratov I., 2014, Estimationof the Plasmaspheric Electron Content on the Base of FORMOSAT–3/COSMIC POD–
Antennas Measurements, 2014, 31st URSI General Assembly and Scientific Symposium(31st URSI GASS), 16–23 August 2014, Beijing, China, (solicited).
15. Mushini, S.C., E. Donovan, P.T. Jayachandran, R.B. Langley, P. Prikryl, and E.
Spanswick, “On the Relation between Auroral ”Scintillation“ and ”Phase without Amplitude“ Scintillation: Initial Investigations,” Proceedings of the XXXIst URSI General
Assembly and Scientific Symposium, Beijing, 16–23 August 2014, doi: 10.1109/URSI-

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GASS.2014.6929726.
16. Shume, E.B., A. Komjathy, R.B. Langley, O. Verkhoglyadova, M. Butala, and A.J.
Mannucci, “Phase Scintillation Estimates in the Polar Ionosphere Inferred from Radio
Occultation on Board CASSIOPE: A Summary,” Proceedings of the 27th International
Technical Meeting of The Satellite Division of the Institute of Navigation (ION GNSS+
2014), Tampa, Florida, 8–12 September 2014, pp. 1138–1141.
17. Yang, Y–M. (Oscar), A. Komjathy, X. Meng, R.B. Langley, M. Butala, E.B. Shume,
and A.J. Mannucci, “Space–Based Remote Sensing of Natural–Hazard–Induced Ionosphere–
Thermosphere Perturbations,” Proceedings of the 27th International Technical Meeting of
The Satellite Division of the Institute of Navigation (ION GNSS+ 2014), Tampa, Florida,
8–12 September 2014, pp. 1473–1477.
18. Rothkaehl H., Krankowski A., 2014, Space Weather and Ionosphere Investigationsin the Frame of LOFAR Program, 11th European Space Weather Week, Liege, Belgium,
November 17 – 21, 2014
19. Cherniak Iu., Zakharenkova I., Krankowski A., Shagimuratov I., 2014, The Ionosphere
Irregularities Modeling on the base of ROTI Mapping, 11th European Space Weather
Week, Liege, Belgium, November 17 – 21, 2014
20. Cherniak Iu., Zakharenkova I., Krankowski A., Shagimuratov I., 2014, Monitoringand Modeling of Ionosphere Irregularities Caused By Space Weather Activity on the Baseof GNSS Measurements, AGU Fall Meeting 2014, San Francisco, USA, 15–19 December
2014
21. Komjathy, A., A. Romero–Wolf, O. Verkhoglyadova, Y.–M. Yang, X. Meng, R.B. Langley, and J. Foster, “CubeSat for Natural–Hazard Estimation With Ionospheric Sciences(CNEWS): A Concept Development to Aid Tsunami Early Warning Systems,” poster
presented at American Geophysical Union, Fall Meeting 2014, San Francisco, CA, 15–19
December 2014, abstract #NH31C–3868.
22. Mushini S., E. Donovan, P. Jayachandran, R.B. Langley, P. Prikryl, E. Spanswick,and B. Jackel, “On the Effect of ”Patchy“ Aurora and Auroral Arcs on GPS Signals: Initial
Investigations,” poster presented at American Geophysical Union, Fall Meeting 2014, San
Francisco, CA, 15–19 December 2014, abstract #SA13A–3971.
23. Shume E., A. Komjathy, R.B. Langley, O. Verkhoglyadova, M. Butala, and A. Mannucci, “Intermediate Scale Plasma Density Irregularities in the Polar Ionosphere Inferredfrom Radio Occultation,” poster presented at American Geophysical Union, Fall Meeting
2014, San Francisco, CA, 15–19 December 2014, abstract #SA13B–3987.
24. Butala. M. D., A. Komjathy, T. F. Runge, B. D. Wilson, X. Pi, and A. J. Mannucci. Evaluating the Impact of GLONASS-Derived TEC Measurements on JPL GIM
and JPL/USC GAIM, IGS Workshop 2014, June 23–27, Pasadena, California, USA.

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12 Theses and Dissertations 2014
Banville, S., Improved Convergence for GNSS Precise Point Positioning. Ph.D. dissertation, Department of Geodesy and Geomatics Engineering, Technical Report No. 294,
University of New Brunswick, Fredericton, New Brunswick, Canada, 269 pp.

13 Plan for activities in 2015
The following actions to be considered:• Higher temporal resolution of IGS GIMs – 1 hour, combination conducted by UWM
to be started as official/routine product (April 2015)• 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 (Spring of 2015).
• The new IAAC from the Natural Resources Canada (NRCan) (Reza Ghoddousi–
Fard, end of March 2015)• Cooperation with IRI COSPAR group
Future improvements are determined by users’ requirements (number of users has significantly increased during the last 16 years).

References
Butala, M.D., A. Komjathy, T.F. Runge, B.D. Wilson, X. Pi, and A.J. Mannucci. Evaluating the Impact of GLONASS-Derived TEC Measurements on JPL GIM and JPL/USC
GAIM. IGS Workshop 2014, June 23-27, Pasadena, California, USA, 2014.
Cherniak, Iu., A. Krankowski, and I.E. Zakharenkova. Observation of the ionosphericirregularities over the Northern Hemisphere: Methodology and Service. Radio Science
49:653–662, 2014b. DOI: 10.1002/2014RS005433.
Cherniak, Iu., I.E. Zakharenkova, and A. Krankowski. The approaches for the ionosphereirregularities modeling on the base of ROTI mapping. Earth, Planets and Space (EPS)
66:165, 2014c. DOI:10.1186/s40623–014–0165–z
Dumont, J.P., V. Rosmorduc, N. Picot, E. Bronner, S. Desai, H. Bonekamp, J. Figa, J. Lillibridge, R. Scharroo. OSTM/Jason–2 Products Handbook. Available online: http://www.ospo.noaa.gov/Products/documents/J2_handbook_v1-8_no_rev.pdf.

158

References
Hausman, J. and V. Zlotnicki. Sea State Bias in Radar Altimetry Revisited. Marine
Geodesy, 33(S1):336-347, 2010. DOI: 10.1080/01490419.2010.487804.
Mannucci, A.J., B.D. WilsonD. N. Yuan, C.H. Ho, U.J. Lindqwister, T.F. Runge. A global
mapping technique for GPS-derived ionospheric total electron content measurements.
Radio Science, 33(3):565-582, 1998.
Schaer, S., W. Gurtner, and J. Feltens. IONEX: The IONosphere Map EXchange Format
Version 1. Proceedings of the IGS AC Workshop, Germany, February 9–11, 1998.
Tseng, K.-H., C.K. Shum, Y. Yi, C. Dai, H. Lee, D. Bilitza, A. Komjathy, C.Y. Kuo,
J. Ping, and M. Schmidt. Regional Validation of Jason–2 Dual-Frequency Ionosphere
Delays. Marine Geodesy, 33(S1):272–284, 2010.

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Multi–GNSS Working Group
Technical Report 2014
O. Montenbruck, P. Steigenberger
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. MGEX isconsidered as a preparatory step for a future multi–GNSS pilot service that will integrate
the new constellations into the established IGS product and service portfolio. A list of
current MGWG members and their respective contributions is given in Tab. 1.

2 Network
The MGEX network has continued to grow from approximately 90 stations at the beginning of 2014 to roughly 110 stations at the end of the year (Fig. 1). This has mainly
been achieved through a large number of new stations contributed by Geoscience Australia (GA). These stations now offer a notably improved coverage of BeiDou and QZSS
tracking in the Asia–Pacific region. Roughly 70 stations of the MGEX network provide
multi–GNSS real–time data streams that can be accessed through BKG’s MGEX caster(http://mgex.igs-ip.net/). About ten sites of the MGEX network are equipped withhydrogen maser clocks that offer access to a highly–stable time scale for GNSS systemcharacterization as well as orbit and clock product generation.

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Table 1: Multi–GNSS Working Group members and task areas (status in December 2014)
Name

Institution

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

AIUB
GOPE
CUT
BKG
JAXA
UNB
BACC
DLR/GSOC

Felix Perosanz
Chris Rizos
Axel Rülke
Tim Springer
Peter Steigenberger
Maik Uhlemann
Rene Warnant
Qulie Zhao

CNES
UNSW
BKG
ESOC
DLR & TUM
GFZ
ULG
Wuhan Univ.

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
Chair MGWG, MGEX coordination, network,
DCB product, data and product analysis(BeiDou, Galileo, QZSS, IRNSS)
Orbit and clock products
External representation (ICG, IGMA, ...)
Data quality control, real–time streams
Data processing strategies
Orbit and clock products, broadcast ephemeris product
Orbit and clock products
Ionosphere
BeiDouFigure 1: Distribution of MGEX stations supporting tracking of QZSS (blue), Galileo (red), andBeiDou (yellow) as of October 2014.

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3 Products
Despite rapid progress in the deployment of the new Indian Regional Navigation Satellite
System (IRNSS), none of the MGEX stations is presently hosting IRNSS–capable receivers.
Further efforts need to be made to deploy such receivers as a prerequisite for familiarization
with this system and for the generation of early IRNSS products.
To avoid a divergence of MGEX and legacy–IGS data holdings, a RINEX 3 transition plan
has been prepared under the lead of the IGS Infrastructure Committee (IC) and releasedby the IGS Governing Board (GB) in December 2014. The transition plan provides theframework for migrating to RINEX–3 as the primary data format and the use of RINEX–3–
style long file names, while making provisions (e.g. converters) to support the old RINEX 2
format for stations and/or analysis centers that are not able to adapt to the new standards.
Implementation of the transition plan is foreseen for 2015, after which a harmonized IGS
data archive with full multi–GNSS support will be available.
For quality control (QC) of multi–GNSS RINEX 3 files, various tools have been preparedwithin the frame of the “quality control task force”. These tools, which were presented
at the IGS Workshop (Rülke et al. 2014), include Anubis (developed by the Geodetic
Observatory Pecny), BQC (developed by the Beijing Aerospace Control Center) and the
BNC tool of BKG. Selected QC analyses have, furthermore, been conducted by Curtin
University (El-Mowafy 2014a, b, 2015a, b).

3 Products
Precise orbit and clock products supporting various subsets of old and new GNSSs arecontributed by various MGEX analysis centers (ACs) including AIUB, CNES/CLS, GFZ,
JAXA, TUM, and Wuhan University. Supported constellations include Galileo, QZSS,
and, since early 2014 also BeiDou. No IRNSS support is available, though, due to the lackof corresponding GNSS monitoring stations.
For Galileo IOV, a good internal consistency of solutions from different ACs has been
demonstrated (Prange et al. 2014a; Steigenberger et al. 2014b). Day–boundary overlaps,
orbit fits and comparisons between ACs demonstrate a precision of about 10 cm for orbit
products based on 3–day data arcs. However, systematic errors of up to ±20 cm can beclearly recognized from satellite laser ranging measurements as well as clock analyses. Dueto the exceptional stability of the hydrogen masers operated by most of the IOV satellites, radial orbit determination errors can be recognized from periodic variations in theestimated clock offsets. These radial errors, which affected all solutions in the same manner, could ultimately be traced to the use of a standalone CODE solar radiation pressure(SRP) model. While highly successful for GPS satellites with near–cubic satellite bodies,
the original CODE model with one–per–rev parameters is unable to fully account for theradiation pressure of a stretched cuboid. Use of a dedicated a priori model (Montenbruck
et al. 2014e) was found to remove the orbit–periodic errors in the Galileo orbit determination and result in a reduction of peak errors by up to a factor of four. As an alternative

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Multi–GNSS Working Groupto the cuboid a priori model, the consideration of twice–per–rev terms in an extended
version of the CODE model has been proposed by AIUB to mitigate SRP induced orbit
modeling errors. As part of the MGEX AC coordination, efforts will be made to arrive
at a harmonized, or at least consistent, formulation of SRP perturbations in the Galileo
orbit modeling.
For QZSS, orbit and clock products continue to be delivered by JAXA and TUM. Differences between the two products amount to roughly 1.3 m (3D rms; Steigenberger andKogure 2014). An improved agreement is usually obtained during periods of yaw–steering
attitude, while a moderate degradation can be observed in orbit–normal mode. Consistentmodeling of these attitude modes as well as the associated solar radiation pressure effects
has been identified as a prerequisite for further improvements of the orbit quality.
For BeiDou precise orbit and clock products are routinely generated and distributed by
Wuhan University and GFZ since early 2014 based on data of the MGEX network (Denget al. 2014). In addition, past data of Wuhan University have been made available for2013. As of mid–2014, roughly 50 stations of the MGEX network contributed BeiDouobservations, however, many of these stations are outside the visibility range of the satellites in inclined geosynchronous orbit (IGSO) and geostationary orbit (GEO) and support“only” orbit determination of satellites in medium altitude Earth orbit (MEO). For the
MEO and IGSO orbits a consistency at the few–decimeter level is achieved for the GFZand Wuhan University orbit products (Fig. 2). For GEO satellites, in contrast, substantially larger errors at the 1 to 10 m level are encountered. In particular, the along–trackcomponent is difficult to determine due to the static viewing geometry of these satellites.
As a possible means to cope with these problems, the combined processing of GNSS andSLR observations has been suggested, but no practical experience has been gained so
far.
As a contribution to improved BDS orbit determination, phase center offsets and variations
for the BeiDou MEO and IGSO satellites have been estimated by ESOC from MGEX observations (Dilssner et al. 2014). Use of theses corrections for routine orbit determinationand product generation is presently under consideration by the MGEX ACs.
Complementary to the precise orbit and clock products, TUM & DLR continue to provide
daily multi–GNSS broadcast ephemeris files for GPS, GLONASS, Galileo, BeiDou, QZSS,and Satellite Based Augmentation Systems (SBAS). Continued efforts are made to further improve the consistency of this product and to cope with receiver/firmware specificdiscrepancies in the decoded ephemerides of different stations. A systematic performancecomparison of broadcast versus precise ephemerides for legacy and new constellations has
been presented in Montenbruck et al. 2014e.
Finally, a multi–GNSS differential code bias (DCB) product covering all observed signals
and tracking modes of GPS, GLONASS, Galileo, and BeiDou is provided by DLR for
use within the MGEX project. The DCBs are based on daily averages of ionosphere–
corrected pseudorange observations (Montenbruck et al. 2014b) and include both satellite164

4 GNSS Evolution

Figure 2: Orbit differences between GFZ and Wuhan University products for the BeiDou MEO(C11–C14) and IGSO satellites (C06–C10) over a 3–month period (February to April2014).

and station–specific biases. For ease of use, 7–day averages of the satellite DCBs are also
provided. Both data sets make use of a prototype implementation of the proposed Bias
SINEX format. In view of limited variability, updates to the MGEX DCB products are
released on a quarterly basis.

4 GNSS Evolution
Within 2014, three GPS Block IIF satellites, two GLONASS–M satellites, one GLONASS–
K1 satellite, two Galileo FOC satellites and two IRNSS satellites have been launched.
The new GPS IIF satellites have replaced outdated Block IIA satellites and contribute toa continued improvement of the average clock stability and signal–in–space range error(SISRE) of this constellation. They have also increased the number of L5–capable GPS
satellites to eight, i.e., about one third of the active GPS constellation.
Only one of the FOC satellites has started transmission of signals in late 2014 following an
extended orbit raising period to partly compensate a launcher orbit injection failure. Very
early orbit and clock determination results for this satellite (E18) have been included in
TUM’s routine Galileo product for MGEX but do not yet allow a thorough performanceassessment.

165

Multi–GNSS Working Group
Despite the release of a first open service signal ICD for IRNSS, no public GNSS observations are presently available for this constellation. Orbit determination is thus limited
to satellite laser ranging measurements. Analyses of Montenbruck et al. 2015 indicate a
SISRE of the IRNSS navigation message of several meters, which is mostly consistent withthe broadcast user range accuracy.
In late April 2014, the GPS control segment has started the routine generation and transmission of CNAV messages by most of the GPS Block IIR–M and IIF satellites. These
offer a better continuity than the legacy LNAV message, but can only achieve an equal
or better SISRE performance when uploaded on a daily basis (Steigenberger et al. 2015).
Such daily uploads are routinely performed from the beginning of 2015 onwards. Combined CNAV/LNAV ephemerides files including GPS and QZSS are provided by TUM &DLR. They are based on a subset of 10 stations of the MGEX network and updated on adaily basis.

5 Standardization
The Multi–GNSS WG has contributed to further evolve the RINEX 3 standard in closeinteraction with other IGS working groups. Among others, a proposal for the incorporationof IRNSS observation data and navigation messages has be developed, which is underreview for the upcoming 3.03 version of RINEX.
For the modeling of antenna phase center offsets and variations an agreement has beenreached by the MGWG and the Antenna WG, to harmonize the axis convention of thesatellite body frame (+z in boresight direction, ±y–axis along solar panel rotation axis) for
old and new constellations. Where applicable, the positive x–axis is chosen in such a waythat the +x panel is sunlit during nominal yaw steering. A dedicated report identifying thespacecraft axis in manufacturer and IGS convention and providing antenna and reflector
coordinates is under preparation and shall be released in the first quarter of 2015 alongwith a new multi–GNSS ANTEX file.

6 Public Outreach
The MGEX website (http://igs.org/mgex) has been migrated to the new IGS web
portal and is now presented in a new layout. While efforts continue to provide up–to–
date information to all MGEX users, frequent updates of the web pages can no longer be
supported due to the introduction of a new contents management system and the shortageof IGS Central Bureau staff.
Achievements of the MGEX project have been advertised in various overview papers
and magazine articles (Montenbruck et al. 2014g, h) as well as numerous conference and166

References
workshop presentations (including Asia–Oceania Regional Workshop on GNSS, Phuket;
COSPAR, Moscow; CSNC, Nanjing; EGU, Vienna; ENC, Rotterdam; EUREF, Vilnius;
FIG Congress, Kuala Lumpur; Geodätische Woche, Berlin; IEEE Workshop on Asia–
Pacific Satellite Navigation and Positioning, Brisbane; PNT, Washington; REFAG, Luxembourg). Most notably, the achievements and status of the MGEX project were highlighted in numerous presentations of MGWG members during the IGS Workshop in
Pasadena.

Acronyms and Abbreviations
AIUB
BACC
BKG
CLS
CNES
CONGO
CUT
DLR
ESA
ESOC
GA
GFZ
GOPE
GSOC
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
Curtin University of Technology
Deutsches Zentrum für Luft– und Raumfahrt
European Space Agency
European Space Operations Center
Geoscience Australia
Deutsches GeoForschungsZentrum
Geodetic Observatory Pecný
German Space Operations Center
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
University of New South Wales

References
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1 Symposium 2014: Reference Frames for Applications in Geosciences, REFAG 2014,
Luxembourg, 2014.
167

Multi–GNSS Working Group
Beutler, G., R. Dach, U. Hugentobler, O. Montenbruck, G. Weber, and E. Brockmann.
GLONASS April – What Went Wrong? GPS World, 25(7):14–16, 2014a.
Beutler, G., R. Dach, O. Montenbruck, U. Hugentobler, G. Weber, and E. Brockmann.
GLONASS and Multi–GNSS in the IGS: Lessons learned from GLONASS Service
Disruptions. 13th Meeting of the National Space–Based Positioning, Navigation, andTiming (PNT) Advisory Board, 3–4 June 2014, Washington DC, 2014b.
Beutler, G., R. Dach, O. Montenbruck, U. Hugentobler, and G. Weber. Multi–GNSS and
Real–time Service in the IGS. 13th Meeting of the National Space–Based Positioning,
Navigation, and Timing (PNT) Advisory Board, 3–4 June 2014, Washington DC,
2014c.
Dach, R., O. Montenbruck, and L. Prange. Status of the IGS–MGEX Project. EUREF
Symposium – EUREF 2014, 3–7 June 2014, Vilnius, Lithuania, 2014.
Deng, Z., Q. Zhao, T. Springer, L. Prange, and M. Uhlemann. Orbit and Clock Determination – BeiDou. IGS Workshop 2014, 23–27 June 2014, Pasadena, CA, 2014.
Dilssner, F., T. Springer, E. Schönemann, W. Enderle. Estimation of Satellite Antenna Phase Center Corrections for BeiDou. IGS Workshop 2014, 23–27 June 2014,
Pasadena, CA, 2014.
El-Mowafy, A. GNSS Multi–frequency Receiver Single–Satellite Measurement Validation
Method. GPS Solutions, 18(4):553–561, 2014a. DOI 10.1007/s10291–013–0352–6.
El.Mowafy A. Quality Monitoring of BeiDou GEO/IGSO/MEO Satellite Observations
IEEE Workshop on Asia–Pacific Satellite Navigation and Positioning, 27–28 February,
Brisbane, QLD, 2014b.
El-Mowafy, A. and C. Hu. Validation of BeiDou Observations. Journal of Geodesy, 8(2):155–168, 2014. DOI 10.1515/jag–2013–0027
El-Mowafy, A. Diagnostic Tools Using a Multi–Constellation Single–Receiver Single–
Satellite Data Validation Method. Journal of Navigation, 68(1):196–214, 2015a. DOI
10.1017/S0373463314000526.
El-Mowafy, A. Estimation of Multi–Constellation GNSS Observation Stochastic Properties
Using a Single–Receiver Data Validation Method. Survey Review, 47(341):99–108,
2015b. DOI 10.1179/1752270614Y.0000000100.
Hugentobler, U., O. Montenbruck, and P. Steigenberger. Radiation Pressure Modelling for
Precise Orbit Determination of the Galileo IOV Satellites. 40th COSPAR Scientific
Assembly, 2–10 Aug. 2014, Moscow, 2014.
Liu, H., G. Tang, D. Imparato, H. Cui, B. Song, and C. Rizos. New Multi–GNSS Data
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Workshop 2014, 23–27 June 2014, Pasadena, CA, 2014a.
Montenbruck, O.. The IGS Multi–GNSS Experiment (MGEX). IGS Workshop 2014,23–27 June 2014, Pasadena, CA, 2014b.
Montenbruck, O., Multi-GNSS Biases. IGS Workshop 2014, 23–27 June 2014, Pasadena,CA, 2014c.
Montenbruck, O., A. Hauschild, and P. Steigenberger. Differential Code Bias Estimation
using Multi–GNSS Observations and Global Ionosphere Maps. ION International
Technical Meeting, Jan. 2014, San Diego, 2014a.
Montenbruck, O., A. Hauschild, and P. Steigenberger. Differential Code Bias Estimation
using Multi–GNSS Observations and Global Ionosphere Maps. Journal of the ION,
61(3):191–201, 2014b. DOI 10.1002/navi.64.
Montenbruck, O., U. Hugentobler, and P. Steigenberger. Recent Progress of the IGS
Multi–GNSS Experiment (MGEX). China Satellite Navigation Conference, CSNC
2014, May, Nanjiing, China, 2014c.
Montenbruck, O., P. Steigenberger, and A. Hauschild. Differential Code Bias Estimation
for New Signals and Constellations. IGS Workshop 2014, June 2014, Pasadena, CA,2014d.
Montenbruck O. Steigenberger P., Hauschild A. Broadcast vs. Precise Ephemerides: aMulti–GNSS Perspective. GPS Solutions, 19(2):321–333, 2014e. DOI 10.1007/s10291–
014–0390–8.
Montenbruck, O., P. Steigenberger, and U. Hugentobler. Enhanced Solar Radiation Pressure Modeling for Galileo Satellites. Journal of Geodesy, 89(3):283–297, 2014f. DOI
10.1007/s00190–014–0774–0.
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. Inside GNSS, 9(1):42–49, 2014g.
Montenbruck, O., P. Steigenberger, R. Khachikyan, G. Weber, R.B. Langley, L. Mervart,
U. Hugentobler. IGS–MGEX, on prépare le terrain pour les sciences et techniques
GNSS multi–constellation. XYZ, 140:35–42, 2014h.
Montenbruck, O., P. Steigenberger, and S. Riley. Orbit Determination and Broadcast
Ephemeris Assessment. ION International Technical Meeting, 26–28 Jan. 2015, Dana
Point, CA, 2015.
Nadarajah, N., P. Teunissen, J.M. Sleewaegen, and O. Montenbruck. The Mixed–Receiver
BeiDou Inter–Satellite–Type Bias and its Impact on RTK Positioning. GPS Solutions,2014. DOI 10.1007/s10291–014–0392–6.

169

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Prange, L., R. Dach, S. Lutz, and S. Schaer. IGS–related multi–GNSS activities at CODE.
ENC–GNSS 2014, Rotterdam, 15–17 April 2014, The Netherlands, 2014a.
Prange, L., P. Steigenberger, M. Uhlemann, S. Loyer, and T. Springer. Orbit and Clock
Determination – Galileo. IGS Workshop, 23–27 June 2014, Pasadena, CA, 2014b.
Rizos, C.. Multi–GNSS Measurement Biases: How the IGS’s MGEX Can Address Such
Challenges. IEEE Workshop on Asia–Pacific Satellite Navigation & Positioning, 26–28
February 2014, Brisbane, Australia, 2014a.
Rizos, C.. The IGS in a Multi–GNSS World. XXVth FIG Congress, 16–21 June 2014,
Kuala Lumpur, Malaysia, 2014b.
Rizos, C.. Activities in Multi–GNSS and Real–Time Service. 6th Asia–Oceania Regional
Workshop on GNSS, 9–11 October 2014, Phuket, Thailand, 2014c.
Rizos, C. and R.E. Neilan. The IGS in its 20th Anniversary Year: New GNSS Activities
Related to MGEX and the Real–Time Service. 9th Meeting of the UN’s International
Committee on GNSS (ICG), 9–14 November 2014, Prague, Czech Republic, 2014.
Rülke A., B. Garayt , J. Dousa, C. Noll, H. Habrich, P. Neumaier, P. Vaclavovic. MGEX
network and observation data. IGS Workshop, 23–27 June 2014, Pasadena, CA, 2014.
Steigenberger, P. and S. Kogure. Orbit and Clock Determination. IGS Workshop 2014,
June 2014, Pasadena, CA, 2014a.
Steigenberger, P., U. Hugentobler, S. Loyer, F. Perosanz, L. Prange, R. Dach, M. Uhlemann, G. Gendt, and O. Montenbruck. Galileo Orbit and Clock Quality of the IGS
Multi–GNSS Experiment. Advances in Space Research, 55 (1):269–281, 2015. DOI
10.1016/j.asr.2014.06.030
Steigenberger, P., O. Montenbruck, and U. Hugentobler. GIOVE–B Solar Radiation Pressure Modeling for Precise Orbit Determination. Advances in Space Research, 2014b.
DOI 10.1016/j.asr.2014.12.009.
Steigenberger, P., O. Montenbruck, and U. Hessels. Performance Evaluation of the EarlyCNAV Navigation Message. ION International Technical Meeting, 26–28 Jan. 2015,
Dana Point, CA, 2015.
Uhlemann, M. and M. Fritsche. Multi–GNSS Orbit and Clock Products of the GFZAnalysis Centre. Geodätische Woche, 7–9 October 2014, Berlin, Germany, 2014.
White, R. and R.B. Langley. Assessing the Preliminary Performance Impact of Including
Galileo Observables into a Precise Point Positioning Processing Scheme. IGS Workshop, 23–27 June 2014, Pasadena, CA, 2014.

170

Real–Time Service
Technical Report 2014
Loukis Agrotis1 , Mark Caissy2 ,Axel Ruelke3 , Steve Fisher4
1
2
3
4

ESA/ESOC
Natural Resources Canada
BKG
NASA/Jet Propulsion Laboratory

1 Introduction
The International GNSS Service (IGS) Real-time Service is a GNSS orbit and clock correction service that enables precise point positioning (PPP) at worldwide scales. The
RTS products enable applications such as scientific testing, geophysical monitoring, hazard detection and warning, weather forecasting, time synchronization, GNSS constellation
monitoring, imagery control and many other public-benefit applications.
The RTS is made possible through partnerships with Natural Resources Canada (NRCan),the German Federal Agency for Cartography and Geodesy (BKG), and the European
Space Agency’s Space Operations Center in Darmstadt, Germany (ESA/ESOC). Support
is provided by 160 station operators, multiple data centers, and 10 analysis centers aroundthe world. The service has been available since April 2013, after transitioning from ahighly successful Pilot Project which allowed the development, prototyping and testing of
the different elements of the Real Time infrastructure.
The International GNSS Service (IGS) has ensured open access, high–quality GNSS data
products since 1994. These products enable access to the definitive global reference frame
for scientific, educational, and commercial applications – a tremendous benefit to the
public. Through the Real-time Service (RTS), the IGS extends its capability to support
applications requiring real-time access to IGS products.

171

Real–Time Service

Figure 1: RTS Receiver Network.

2 RTS Infrastructure
The RTS is based on the IGS global infrastructure of network stations, data centers andanalysis centers that provide the "world’s standard" high–precision GNSS data products.
Figure 1 shows the distribution of sites in the current Real Time network.
The RTS product streams are combination solutions generated by processing individual
solutions from participating Real-time Analysis Centers (RTAC). The effect of combining
the different RTAC results is a more reliable and stable performance than that of any
single AC’s product. Operational responsibility for the generation of the official RTS
combination products lies with the IGS Real Time Analysis Center Coordinator (RTACC),
currently the European Space Agency’s Space Operations Center in Darmstadt, Germany(ESA/ESOC).
The RTS is supported by the IGS for free and open access by all users, as far as dissemination resources allow. The RTS has been operational since April 2013. IGS strives todeliver its products on a highly available basis, however, due to the volunteer nature of
IGS, availability of products is not guaranteed.
As NTRIP is an RTCM open standard, no special licensing is associated with its use.
Commercial entities interested in integrating RTS into their equipment should contact the
IGS Central Bureau to for additional information and support. The RTS product streams
are available through designated product distribution centers around the world. Users
may register online through the IGS Real-time Service website to subscribe to casters
operated by BKG, IGS Central Bureau and CDDIS.

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3 RTS Products

3 RTS Products
The RTS Products consist of GNSS satellite orbit and clock corrections to the broadcast ephemeris, as well as data streams from the global network of high–quality GNSS
receivers.
The RTS products are distributed as RTCM SSR correction streams broadcast over theInternet using the NTRIP protocol. The corrections are expressed within the International
Terrestrial Reference Frame 2008 (ITRF08). The initially offered products include GPS–
only correction streams, as well as an experimental GPS+GLONASS correction streamthat is anticipated to be fully integrated within the RTS in the near future. The RTS
products are disseminated in the form of RTCM SSR streams. The technical content of
the RTS products is described in the Table 1.
The products, designated at IGS01/ICG01 and IGS02, contain corrections only for the
GPS satellites. The experimental product, designated at IGS03, contains corrections for
GPS and GLONASS. The RTCM v3 streams may be used to support development andtesting of real-time Precise Point Positioning (PPP) and related applications.
The IGS continuously monitors the accuracy of its products through inter–comparison
Table 1: RTS Product Streams
CenterDescription

NTRIP Mountpoint

ESOC

GPS–only combination–epoch-wise approach (CoM/APC)

IGC01/IGS01

BKG
with TU Prague

GPS–only combination–Kalman filter approach (APC)
GPS+GLONASS combination–Kalman filter approach (APC)

IGS02
IGS03

BKG
with TU Prague

GPS and GPS + GLONASS RT orbits
and clocks using IGU orbits (CoM/APC)

CLK00/10
CLK01/11

CNES

GPS RT orbits and clocks based on IGU orbits (CoM/APC)
GPS+GLONASS orbits and clocks (CoM/APC)

CLK92/93
CLK90/91

DLR

GPS RT orbits and clocks based on IGU orbits
GPS+GLONASS orbits and clocks (DLR caster)

CLKC1/A1
CLK21

ESOC

RT orbits and clocks using NRT batch orbits every 2 hours (ESOC)and using IGU (ESOC2) (CoM /APC)

CLK50/51
CLK52/53

GFZ

RT orbits and clocks and IGU orbits (CoM/APC)

CLK70/71

GMV

RT orbits and clocks based on NRT orbit solution (CoM/APC)

CLK81/80

Geo++

RT orbits and clocks (APC) (Geo++ caster)

RTCMSSR

NRCan

RT orbits and clocks using NRT batch orbits every hour (APC)

CLK22

TUW

RT clocks based on IGU orbits (CoM/APC) (out of service)

CLK80/81

WUHAN

RT clocks based on IGU orbits (CoM/APC)

CLK15/16

173

Real–Time Serviceof results between Analysis Centers and the IGS Rapid and Final products. The orbit
and clock comparisons for the IGS01 combination over the last several years are shown in
Fig. 2 and Fig. 3. Fig. 4 shows the clock comparisons for the individual ACs, with the
IGS01 results superimposed in black. The effectiveness of the combination approach inremoving outliers in the individual AC solutions is clearly demonstrated.
Some outliers are still apparent in the combination. These are mainly caused by the larger
orbit prediction errors associated with eclipse–related events for GPS Block IIA and Block
IIF satellites. Additional Block IIF events have been associated with non–nominal ground–commanded attitude manoeuvres.
The results for the experimental GLONASS AC solutions are shown in Fig. 5 There areclear periods when some of the solutions deteriorate. These are due to RTCM encoding
errors that are currently under investigation.

IGS01/IGC01 Combination Orbit 1-D RMS Against IGS Rapids (mm)
100
90
80

70
60
50
40
30
20
10
0
29/10/2010

30/04/2011

30/10/2011

30/04/2012

30/10/2012

01/05/2013

31/10/2013

02/05/2014

01/11/2014

Figure 2: RTS Combination Daily Orbit Comparison Statistics.

174

03/05/2015

3 RTS Products

IGS01/IGC01 Combination Clock SD Against IGS Rapids (ns)1

0.9

Batch Combination

0.8

RT Combination

0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
20/07/2008

20/07/2009

20/07/2010

20/07/2011

19/07/2012

19/07/2013

19/07/2014

19/07/2015

Figure 3: RTS Combination Daily Clock Comparison Statistics.

AC Clock Standard Deviation Against IGS Rapids (ns)
1.00

BKG
0.90

CNES

0.80

DLR

0.70

ESA1
ESA2

0.60

GFZ
0.50

GMV
NRCan

0.40

WUH

0.30

IGS01
0.20
0.10
0.00
29/10/2010

30/04/2011

30/10/2011

30/04/2012

30/10/2012

01/05/2013

31/10/2013

02/05/2014

01/11/2014

03/05/2015

Figure 4: RTS AC and Combination Solution Daily Clock Comparison Statistics.

175Real–Time Service

GLONASS Orbit 1-D RMS Against ESA Rapids (mm)

1000

BKG

900

CNES

800

GMV

700

DLR

600

IGS03

500
400
300
200

100
0
21/04/2014

20/06/2014

19/08/2014

18/10/2014

17/12/2014

15/02/2015

16/04/2015

21/04/2014

20/06/2014

19/08/2014

18/10/2014

17/12/2014

15/02/2015

16/04/2015

GLONASS Solution Clock SD Against ESA Rapids (ns)

3
2.7
2.4

BKG

2.1

CNES

1.8

GMV
DLR

1.5

IGS03

1.2
0.9
0.6
0.3
0
21/04/2014

20/06/2014

19/08/2014

18/10/2014

17/12/2014

15/02/2015

Figure 5: RTS GLONASS Solution Daily Comparison Statistics.

176

16/04/2015

4 References

4 References
Caissy, M., L. Agrotis. The IGS Real–Time Service. IGS Workshop, Pasadena, California,
June 2014.
Caissy, M., L. Agrotis, G. Weber, M. Hernandez–Pajares, U. Hugentobler. The International GNSS Real–Time Service. (2012, June) GPS World, pp. 52–58.
Agrotis, L., M. Caissy, G. Weber, M. Ge, K. MacLeod, M. Hernandez–Pajares. IGS Real–
time Infrastructure: From Pilot Project to Operational Service, presented at PPP–RTK
and Open Standards Symposium, Frankfurt, March 2012.
Caissy, M., L. Agrotis. Real–Time Working Group and Real–Time Pilot Project, IGS
2011 Technical Report (http://igscb.jpl.nasa.gov/overview/pubs.html).
Caissy, M., G. Weber, L. Agrotis, G. Wübena, M. Hernandez–Pajares. The IGS Real–timePilot Project–The Development of Real-time IGS Correction Products for Precise Point
Positioning, presented at EGU, Vienna, April 2011.
Weber, G., L. Mervart, L. Agrotis, A. Stürze. Real–time Combination of GNSS Orbit andClock Correctors for Precise Point Positioning presented at IUGG/IAG General Assembly,
Melbourne, July 2011.
Agrotis, L., P. Alfaro Sanz, J. Dow, R. Zandbergen, D. Svehla, A. Ballereau. ESOC’s
RETINA System and the Generation of the IGS RT Combination, IGS Workshop, Newcastle, June 2010.
Weber, G. and L. Mervart. Real–time Combination of GNSS Orbit and Clock Correction
Streams Using a Kalman Filter Approach, ION GNSS, 2010.
Weber, G., D. Dettmering, H. Gebhard, R. Kalafus. Networked Transport of RTCM via
Internet Protocol (Ntrip), IP–Streaming for Real–Time GNSS Applications, ION GNSS,2005.
For more information, please visit the RTS website (http://rts.igs.org).

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Real–Time Service

178

Reference Frame Working Group
Technical Report 2014
P. Rebischung1 , B. Garayt2 , 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
Besides a continuous quality monitoring of the IGS SINEX combination products, themain activity of the Reference Frame Working Group in 2014 was the preparation of the
IGS contribution to ITRF2014, which will consist of daily combinations of the AC SINEX
solutions from the IGS 2nd reprocessing campaign (repro2). After an overview of theoperational IGS SINEX combination results in 2014 (Sect. 2) and a brief review of thecurrent status of the IGb08 Reference Frame (Sect. 3), this report will finally present
results from preliminary combinations of the AC repro2 SINEX solutions (Sect. 4).

2 Recent IGS SINEX combination results
Figure 1 shows the RMS of the Analysis Center (AC) station position residuals from thedaily IGS SINEX combinations of year 2014, i.e. the global level of agreement between
the AC and IGS combined station positions once reference frame differences have been
removed. Except a bump in GFZ’s RMS during weeks 1807–1820 due to an issue in theimplementation of the 2nd order ionospheric corrections, the overall tendency over 2014
was an improvement of the inter–AC agreement achieved through successive updates of
the AC’s analysis strategies listed below.
• On week 1803, MIT started using their repro2 settings for their operational products,
leading to slightly lower RMS in all three components.

179

Reference Frame Working Group
4 mm

East

4 mm

3 mm

3 mm

2 mm

2 mm

1 mm

1 mm

0 mm

North

0 mm
1780

1790

1800

1810

1820

8 mm

1780

1790

1800

1810

1820

Up

6 mm

cod

gfz

mit

4 mm

emr

grg

ngs

2 mm

esa

jpl

sio

0 mm
1780

1790

1800

1810

1820

GPS week

Figure 1: RMS of AC station position residuals from the 2014 daily IGS SINEX combinations.
All time series were low–pass filtered with a 10 cycles per year cut–off frequency.

• On week 1807, SIO made major updates to their analysis strategy. The SIO solutions
have since then been included with weight in the daily IGS SINEX combinations,
except for the pole rates.
• On week 1816, JPL started using their repro2 settings for their operational products,
leading to notably lower RMS in the vertical component.
• On week 1820, NGS made several updates to their analysis strategy, leading tonotably lower RMS in all three components.
Figures 2 and 3 show the AC Earth Orientation Parameter (EOP) residuals from the IGS
SINEX combinations of year 2014. The inter–AC agreement on EOPs has not shown any
significant evolution over 2014. The different features noted by Rebischung et al. 2014acan in particular still be observed:• Sub–seasonal and abrupt variations in the X–pole and Y–pole rate estimates ofseveral ACs, possibly due to GLONASS orbit modeling deficiencies. A particularly
abrupt excursion is visible in GRG’s residuals around week 1803.
• A strong predominance of MIT’s LOD estimates in the combination. This predominance is now known to be related to the use by MIT of inter–day constraints on
empirical orbit parameters (T. Herring, personal communication).
Finally note that GRG’s LOD estimates have been included with weight in the daily IGS
SINEX combinations since week 1777.

180

2 Recent IGS SINEX combination results

xp residuals (mas)yp residuals (mas)

0.0

0.0

cod

−0.2

−0.2

emr

−0.4

−0.4

esa

−0.6

−0.6

gfz

−0.8

−0.8

grg

−1.0

−1.0

jpl

−1.2

−1.2

mit

−1.4

−1.4

ngs

−1.6

−1.6

sio

1780

1790

1800

1810

1820

1780

1790

GPS week

1800

1810

1820

GPS week

Figure 2: AC pole coordinate residuals from the 2014 daily IGS SINEX combinations. The
individual AC time series have been shifted by multiples of 0.2 mas for clarity.

xp rate residuals (mas/d)

yp rate residuals (mas/d)

LOD residuals (ms)

0

0

0.0

cod

−1

−1

−0.1

emr

−2

−2

−0.2

esa

−3

−3

−0.3

gfz

−4

−4

−0.4

grg

−5

−5

−0.5

jpl

−6

−6

−0.6

mit

−7

−7

−0.7

ngs

−8

−8

−0.8

1780

1790

1800

1810

GPS week

1820

1780

1790

1800

1810

GPS week

1820

sio
1780

1790

1800

1810

1820

GPS week

Figure 3: AC pole rate and LOD residuals from the 2014 daily IGS SINEX combinations. The
individual AC time series have been shifted by multiples of 1 mas/d and 0.1 ms forclarity.

181

Reference Frame Working Group# RF stations# RF core stations
70

150
60
120

50
1650

1700

1750

1800

1650

GPS week

1700

1750

1800

GPS week

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

3 Status of the IGb08 Reference Frame
In 2014, the number of usable IGb08 Reference Frame (RF) stations and the number of
RF core stations used to align the IGS daily combined solutions to IGb08 have fortunately
remained fairly constant, around 132 and 63 respectively (Fig. 4). In fact, only two IGb08
stations became unusable as RF stations because of equipment changes in 2014, while twoothers stopped transmitting data. The distribution of the usable IGb08 core stations isstill rather satisfactory. However, the accuracy of the IGb08 reference station coordinates
has kept degrading because of growing station velocity propagation errors. Over 2014, theglobal level of agreement between the IGS daily combined solutions and IGb08 has beenaround 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 theReference Frame realized by the IGS products and will get worse until a new Reference
Frame based on the future ITRF2014 is adopted.

4 Preliminary results from the repro2 SINEX combinations
Eight IGS Analysis Centers (ACs) have now completed a second reanalysis campaign(repro2) of the GNSS data collected by the IGS global tracking network back to 1994, using
the latest available models and methodology, with the main purpose of providing the IGS
contribution to ITRF2014. A first round of daily combinations of the AC repro2 SINEX
solutions was performed in October 2014 and revealed quality issues in the contributions ofseveral ACs (Rebischung et al. 2014b). The concerned ACs have since then re–submitted
improved products, so that 7 out of 9 AC contributions will eventually be included withweight in the final repro2 SINEX combinations (Tab. 1). GRG’s contribution will be
included for comparison only due to outstandingly large residuals in the North and Up
components (Fig. 5). Over their common time span, only one of both GFZ contributions(i.e., GFZ’s TIGA contribution – GTZ) will be included with weight, as double weight
would otherwise be given to the GFZ AC.
Figure 5 shows the WRMS of the AC station position residuals from the latest preliminary182

4 Preliminary results from the repro2 SINEX combinations
Table 1: AC contributions to the IGS 2nd reprocessing campaign (current status)
AC

Time span(GPS weeks)

Inclusionin final repro2 SINEX combinations

COD
EMR
ESA
GFZ
GRG
JPL
MIT
GTZ
ULR

0730 – present
0769 – present
0782 – present
0730 – 1824
0938 – present
0730 – present
0730 – present
0730 – 1720
0782 – 1773

with weightwith weightwith weightwith weight after week 1721
for comparison onlywith weightwith weightwith weightwith weight

8 mm

East

8 mm

6 mm

6 mm

4 mm

4 mm

2 mm

2 mm

0 mm

North

0 mm
1996

2000

2004

2008

12 mm

2012

1996

2000

2004

2008

2012

Up

9 mm

cod

gfz

mit

6 mm

emr

grg

gtz

3 mm

esa

jpl

ulr

0 mm
1996

2000

2004

2008

2012

Figure 5: WRMS of AC station position residuals from preliminary combinations of the daily
AC repro2 SINEX solutions. All time series were low–pass filtered with a 2.5 cycles
per year cut–off frequency.

round of daily repro2 SINEX combinations. Note that the GFZ, GTZ and ULR were here
still included for comparison only. With the exception of GRG, the AC WRMS are, after
2004, homogeneously within 1 − 2 mm in the horizontal components and 3 − 4 mm in the
Up component. However, before 2000 and even more before 1997, a clear degradation of
the inter–AC agreement can be noted. Since it was much less pronounced in the resultsfrom the weekly repro1 SINEX combinations, this degradation is likely related to the useof daily data integrations in repro2.

183

Reference Frame Working Group
Table 2: WRMS of the EOP residual time series from the latest preliminary round of daily repro2
SINEX combinations. (ACs included with weight in these combinations are indicatedin bold.)AC

X–pole(µas)

Y–pole(µas)

X–pole rate(µas/d)Y–pole rate(µas/d)

LOD
(µs)

COD
EMR
ESA
GFZ
GRG
JPL
MIT
GTZ
ULR

34.7
40.0
25.6
38.6
34.7
31.0
16.9
31.9
32.5

33.3
44.5
25.8
40.5
29.5
28.1
16.4
32.1
33.4

175.4
218.2
138.6
198.9
152.2
169.3
62.7
175.9
201.5

184.0
183.0
143.5
198.1
194.5
172.5
70.1
166.0
207.8

10.8
23.8
9.8
11.9
8.3
16.2
2.0
10.5
23.5

Table 2 contains the WRMS of the EOP residual time series from the same round of
preliminary repro2 SINEX combinations. Plots of these series can be found in Rebischunget al. 2014b. A predominance of MIT’s estimates can be noted for all EOPs. It is more
pronounced for the pole rates than for the pole coordinates, and even more pronounced for
LOD, like in the operational SINEX combinations (Sect. 2). With the exception of MIT,the inter–AC agreement on EOPs is at the level of 30 − 40 µas for the pole coordinates,
150–200µas/d for the pole rates and 10 − 20 µs for LOD (after LOD bias corrections basedon the IERS Bulletin A have been applied).
The scales of the daily repro2 AC SINEX solutions show an excellent agreement witheach other, at the level of 0.3 − 0.5 mm WRMS. The inter–AC scale rate differences arein particular below 0.05 mm/yr for the 5 ACs included with weight so far (Rebischunget al. 2014b), which could favor a contribution of GNSS to the definition of the ITRF2014
scale rate. On the other hand, compared to the repro1 results, no substantial decrease of
the inter–AC origin discrepancies could be observed. The preliminary repro2 combined
geocenter time series is moreover still showing considerable differences with SLR–derived
geocenter time series (Rebischung et al. 2014b).
The final repro2 daily combined SINEX solutions will be delivered to the IERS before theend of February 2015.

References
Rebischung, P., B. Garayt, X. Collilieux, and Z. Altamimi. IGS Reference Frame Working
Group Coordinator Report 2013. In: Dach and Jean (eds.), IGS Technical Report184References
2013, International GNSS Service, pp. 165–171, 2014a.
ftp://igs.org/pub/resource/pubs/2013_techreport.pdf
Rebischung, P., B. Garayt, X. Collilieux, and Z. Altamimi. The IGS contribution to
ITRF2013. AGU Fall Meeting 2014, San Francisco, 15–19 Dec., 2014b.
http://acc.igs.org/trf/Rebischung-AGU2014.ppt

185

Reference Frame Working Group186

Tide Gauge Benchmark
Monitoring Working Group
Technical Report 2014
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,
S. Williams, G. Wöppelmann, P. Woodworth

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 2014, the TIGA–WG has continued with the reprocessing of the TIGA network, which was in parallel to the repro2 campaign of the IGS. Nearly 800 GNSS@TG

187

TIGA Working Groupstations and IGS08b core sites are processed by the TIGA Analysis Centers. End of 2014
first submissions had been made to the IGS repro 2 for the inclusion into the ongoing
ITRF update.
The following part provides details for each TIGA component.

BLT TIGA Analysis Center/ULX Combination Center
N. Teferle, A. Hunegnaw, R. Bingley, and D. Hansen

Reprocessing
The consortium of British Isles continuous GNSS Facility (BIGF) and the University of
Luxembourg TAC (BLT) has produced minimally constrained SINEX solutions from its
reprocessing using the Bernese GNSS Software (BSW) version 5.2 for the period 1995 to2013. The BLT reprocessing strategy follows closely that of (Steigenberger et al. 2006)
while incorporating recent model developments and the latest International Earth Rotation
and Reference Systems Service (IERS) 2010 conventions (Petit and Luzum 2010). We
summarize our network DD processing in Tab. 1. In the DD strategy we have included all
IGb08 core stations in order to achieve a consistent reference frame implementation anddaily position estimates for up to 450 stations are available (See Fig. 1).

Figure 1: GPS network processed at BLT for TIGA.

188

Table 1: Summary of the GPS data processing strategy at the ULParameters

Description

GPS software
Data

Bernese Software Version 5.2 (Dach et al. 2007)
Double–differenced phase and code observations
from up to 450 stations per day
3 degree and elevation dependent weighting(w = cos2z, z: zenith angle)
Ionospheric–free linear combination (L3) is employed together
with the 2nd order correction
An a priori dry tropospheric delay (Saastamoinen) computedfrom standard atmosphere. For wet part continuous piecewise –linear troposphere parameters estimated in 2–hour intervals,
plus gradients in north–south and east–west directions at
24–hour intervals. The slant delay information is mapped to
the zenith using the VMF1 mapping function.
C04 series IERS Bulletin B
IGS absolute elevation and azimuth
dependent PCV igs08.atx fileElevation cut–off angle
Ionospheric refraction
Tropospheric refraction

Earth orientation
Antenna PCV(http://igscb.jpl.nasa.gov/igscb/station/general/pcv_archive)

Earth and polar tide
Ocean Loading
Datum

Ambiguity Resolution
Meta data

IERS2010 (Petit and Luzum 2010)
Computed using FES2004 ocean tide model(http://holt.oso.chalmers.se/loading)
No–Net–Rotation (NNR) and No–Net–Translation (NNT) withrespect to IGb08 (Rebischung et al. 2012). However, any conditions
such as NNT or No–Net–Scale (NNS) or a combination of them canbe applied since we save the normal equations of our DD processing
Resolved to integers up to 6000 km using different techniques
depending on the baseline length
Intensive meta data check189

TIGA Working Group

Combination
The University of Luxembourg (ULX) also acts as a TIGA Combination Center (TCC).
One of the objectives of the TIGA Working Group is to produce consistent station coordinates on a weekly basis in the form of SINEX files, which are useful for multi–solution
combinations, i.e. following largely the example of the routine IGS combinations. At ULX
we aim to explore the potential in improving the precision and accuracy of the station
coordinates and station velocities through network analysis. So far, only three of five TAC
solutions have been completed and are now available for a preliminary multi–year combination. These include the solutions of the British Isles continuous GNSS Facility – University of Luxembourg consortium (BLT), the GeoForschungsZentrum (GFZ) Potsdam,and of the University of La Rochelle (Fig. 2). It is noteworthy that all three contributing
TACs have analyzed global networks with a consistent set of reference frame stations, i.e.
the IGb08 core stations. Taking these individual TAC solutions ULX has computed afirst combination using two independent combination software packages: CATREF andGLOBK. A preliminary study confirms that the two independent combinations as implemented by ULX agree well and demonstrates that either of the two independent software
packages may be used by the TCC. However, the coordinate differences exhibit regionality,
i.e. they show some regional variations in scatter and biases (see Fig. 3). An issue that
requires further investigation for long–term combinations.
BLT

GFZ

MIT

ULR

Figure 2: TIGA and IGS AC solutions used for the preliminary TIGA combination in this study.
MIT solution was included to improve the redundancy in our combination. It will be
replaced when other TIGA solutions become available.

190

5
4
Differences [mm]

3
2
1
0
-1
-2
-3
-4
-5

40

80

120

160

200

240

280

320

360

40

80

120

160

200

240

280

320

360

5
4
Differences [mm]

3
2
1
0
-1
-2
-3
-4
-5

Figure 3: Coordinate differences for 400 stations between the CATREF/GLOBK combinationof eight IGS AC solutions for December 2011. Green circles represent the coordinate
differences for the X, red for the Y and blue for the Z component. For clarity the Y andZ components are offset by 3 mm. (top) The differences are arranged alphabeticallyaccording to station four characters ID. (bottom) The differences are arranged regionally according to station DOMES number ID. For example, the coordinate differences
between stations 80 and 170 (the two vertical dotted lines) show those stations locatedin North America.

191

TIGA Working Group

DGFI TIGA Processing
L. Sánchez

The Deutsches Geodätisches Forschungsinstitut, since January 2015 integrated into theTechnische Universität München (DGFI–TUM), processes a global network with about
450 continuously operating GNSS stations as contribution to the TIGA working group(Fig. 4). The analysis strategy is aligned to IERS Conventions 2010 and to the GNSS–
specific guidelines defined by the IGS for the second reprocessing of its global network(http://acc.igs.org/reprocess2.html). The main processing characteristics are:• Reference frame: IGS08/IGb08 (Rebischung et al. 2012)• Basic observable: ionosphere–free linear combination• Sampling rate: 30 sec• Elevation cut–off angle: 3 deg• Elevation–dependent weighting of observations: 1/cos2z, where z is the zenith distance• A–priori values for the estimation of satellite orbits, satellite clock offsets, and EOP
are the IGb08–based satellite products and EOP generated by the IGS processing
center CODE (Center for Orbit Determination in Europe, ftp://ftp.unibe.ch/aiub/CODE)• Phase ambiguities for L1 and L2 solved after the quasi–ionosphere free (QIF) strategy
described in Dach et al. 2007. The ionosphere models of CODE (ftp://ftp.unibe.
ch/aiub/CODE) are used as input to increase the number of solved ambiguities• Antenna phase center model: igs08.atx (Schmid 2011)• Tropospheric zenith delay modelling based on the Vienna Mapping Function 1(VMF1, Böhm et al. 2006) with a priori values (∼dry part) from the gridded coefficients provided by J. Böhm at http://ggosatm.hg.tuwien.ac.at/DELAY/GRID/VMFG and refinement through the computation of partial derivatives with 2 h intervals
within the network adjustment• Tidal corrections for solid Earth tides, permanent tide, and solid Earth pole tide as
described by Petit and Luzum 2010. The ocean tidal loading is reduced with the
FES2004 model (Letellier 2004) and the atmospheric tidal loading caused by thesemidiurnal constituents S1 and S2 is reduced following the model of van Dam andRay 2010. The reduction coefficients for the ocean tidal loading are provided by
M.S. Bos and H.–G. Scherneck at http://holt.oso.chalmers.se/loading. The

192

reduction coefficients for the atmospheric tidal loading are provided by T. van Dam
at http://geophy.uni.lu/ggfc-atmosphere/tide--loading--calculator.html• Non–tidal loadings like atmospheric pressure, ocean bottom pressure, or surfacehydrology are not reduced.
• Daily free normal equations are computed by applying the double difference strategy
using the Bernese GNSS Software V5.2 (Dach et al. 2007, 2013). The baselines
are formed by maximizing the number of common observations for the associatedstations. The processed network is classified in four clusters of ca. 120 stations each.
• The seven daily free normal equations corresponding to a GPS week are combined
into a weekly free normal equation using also the Bernese GNSS Software V5.2.
Daily and weekly solutions for the time period covered from January 2007 to December
2012 are already reprocessed. At present, a preliminary multi–year solution is being
computed to evaluate the consistency between the epoch–solutions.

Figure 4: TIGA network processed at DGFI–TUM.

193

TIGA Working Group

Tide Gauge data reprocessing at GFZZhiguo Deng

The solutions of the GFZ TIGA REPRO2 (GTZ) will also contribute to IGS 2nd Data
Reprocessing Campaign (IGS REPRO2) with the GFZ IGS REPRO2 (GFZ) solution.
Following the 2nd IGS reprocessing finished in 2010 some improvements were implemented
into the latest GFZ software version EPOS.P8 : reference frame IGb08 based on ITRF2008,
antenna calibration igs08.atx, geopotential model (EGM2008), higher–order ionosphericeffects, new a priori meteorological model (GPT2), VMF mapping function, and otherminor improvements.
The GNSS data is collected through the SONEL data center (www.sonel.org) of the
Global Sea Level Observing System (GLOSS). GNSS data of the globally distributed
tracking network of 794 stations for the time span from 1994 until end of 2012 are used
for the GFZ TIGA REPRO2.
In the IGS repro2 combination the GTZ and GFZ solution are included (IGSMAIL–7055).
Now the combination solution is now available. The station position RMS of the 9 solutions
with respect to the Repro2 daily combined solution are given in Fig. 7 (East, North and
Up in mm). The GFZ/GTZ solutions show consistent high accuracy during the whole
period.

Figure 5: Global distribution of the TIGA reprocessed GPS stations for GFZ REPRO2 (whitedots) and TIGA (green+white dots).

194

Figure 6: Weekly Number of stations and satellites included in the GFZ REPRO2 and TIGA
REPRO2. TIGA REPRO2 is based on the same set of GFZ REPRO2 stations, so thatthe difference to IGS_REPRO2 shows the number of processed TIGA only stations.

Figure 7: Station position residuals with respect to the Repro2 daily combined solutions. In
general the weighted RMS of the GFZ and GTZ station coordinates are better than
average.

195

TIGA Working GroupULR TIGA Analysis Center
M. Gravelle, A. Santamaría–Gómez, and G. Wöppelmann

The University of La Rochelle (ULR) analysis center has participated to the International
GNSS Service (IGS) Repro2 and TIGA campaigns which aim at reprocessing worldwide
GPS data for high precision products such as satellite orbits & clocks and terrestrialreference frame (station positions and velocities). The ULR analysis center has the particular aim of reprocessing the densest network of GPS stations nearby tide gauges whose
data have been collected through the SONEL (http://www.sonel.org) data assembly
center.
Daily positions estimates between 1995.0 and 2015.0 have been obtained for a set of 749
stations worldwide distributed using the GAMIT/GLOBK software. The combination andalignment of the daily network solutions to the International Terrestrial Reference Frame(ITRF2008), including estimation of station velocities, is performed using the CATREF
software.

Figure 8: Network of reprocessed stations at ULR (left) and number of stations reprocessed perday (right).

196

SONEL Data Center
M. Gravelle, M. Guichard, E. Prouteau, and G. Wöppelmann

Status of the network
The SONEL data center (www.sonel.org), hosted by the University of La Rochelle, collects, analyses and archives GNSS data and metadata from almost 800 permanent stations
nearby (<15 km) tide gauges (CGPS@TG) (Fig. 9). Among these stations, SONEL provides
the data and metadata of the 122 TIGA stations (Fig. 10). Figure 11 shows the evolutionof the number of RINEX files from GNSS@TG stations archived in SONEL. The distributionof the stations record length is plotted on Fig. 12.

Figure 9: GNSS@TG
org).

network(www.sonel.

Figure 10: TIGA GNSS network (www.sonel.
org).

Figure 11: Evolution of the number of RINEX files from GNSS@TG stations archived in SONEL(www.sonel.org).

197

TIGA Working Group

Figure 12: Stations record length histogram of the GNSS@TG in SONEL. Only stations with morethan 70% of valid data are taken into account.

Quality check plots
Tools have been developed to automate the analysis and the quality control of the collected GNSS data. Dynamic plots displaying the tracking performance of the stations are
updated daily and provided on each station webpage in the SONEL portal (Fig. 13).

Figure 13: Examples of quality check plots for SCOA station.

198

GNSS@TG geodetic ties
In addition to the data and metadata collection, SONEL strives to get the geodetic tie
between the GNSS station and the co–located tide gauge (Fig. 14). While the geodetic tie
is known only for 17% out of 779 GNSS stations archived in SONEL, this number reaches
63% for the TIGA stations (Fig. 15).

Figure 14: SONEL levelling results
diagram for St Jean de Luztide gauge.

Figure 15: Status of TIGA stations with geodetic ties available at SONEL.

Collaboration with other data centers
SONEL is recognized as GNSS at tide gauges Data Assembly Center for the UNESCO/IOC
Global Sea Level Observing System (GLOSS, http://www.gloss-sealevel.org) andstrives to develop the interoperability with the other GLOSS data centers, especially with
the Permanent Service for Mean Sea Level (PSMSL, http://www.psmsl.org) database.

Evolution of the SONEL website access
Evolution of the SONEL website access is shown in Fig. 16 and Tab. 2.
Total number of visits
Number of visitors
Number of viewed pages
Average number of viewed
pages by visit

Figure 16: Evolution of the number of visits permonth. Status at 2015/02/26.

22854
16674
56322
2.46

Table 2: Number of visits between
2014-01-01 and 2014-12-31

199

TIGA Working Group

References
Böhm, J., B. Werl, and H. Schuh. Troposphere mapping functions for GPS andvery long baseline interferometry from European center for Medium–Range Weather
Forecasts operational analysis data.
J. Geophys. Res., 111, B02406, 2006.
DOI:10.1029/2005JB003629
Dach, R., U. Hugentobler, P. Fridez, and M. Meindl. Bernese GPS Software Version 5.0(User Manual). Astronomical Institute, University of Bern, Astronomical Institute of
University of Bern, Bern, Switzerland, 2007.
Dach, R. Bernese GPS Software: New features in version 5.2. Astronomical Institute,
University of Bern, 2013. Available at http://www.bernese.unibe.ch.
van Dam, T. and R. Ray. S1 and S2 atmospheric tide loading effects for geodetic applications. 2010. Data set accessed 2013–06–01 at http://geophy.uni.lu/
ggfc-atmosphere/tide-loading-calculator.html.
Hunegnaw, A., F.N. Teferle, R.M. Bingley, and D.N. Hansen. A Multi–Year Combinationof Tide Gauge Benchmark Monitoring (TIGA) Analysis Center Products: Preliminary
Results. American Geophysical Union (AGU) Fall Meeting, 15 – 16 December, 2014,
San Francisco, 2014.
Hunegnaw, A., F.N. Teferle, R.M. Bingley, and D.N. Hansen. Status of TIGA activities
at the British Isles continuous GNSS Facility and the University of Luxembourg. The
IAG Scientific Assembly 2013, Potsdam 2013, in press, 2014.
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
et de l’Espace, 2004.
Petit, G. and B. Luzum (eds). IERS Conventions (2010). Number 36. Verlag des Bundesamtes für Kartographie und Geodäsie, Frankfurt am Main, Germany, 2010.
Rebischung, P., J. Griffiths, J. Ray, R. Schmid, X. Collilieux, and B. Garayt. IGS08:
the IGS realization of ITRF2008. GPS Solutions, 16(4):483–494, 2012. DOI:
10.1007/s10291–011–0248–2.
Santamaria-Gomez, A., C. Watson, M. Gravelle, M. King, and G. Wöppelmann. Levelling co–located GNSS and tide gauge stations using GNSS reflectometry. Journal of
Geodesy, 89:241–258, 2015.
Schmid, R. Upcoming switch to IGS08/igs08.atx – Details on igs08.atx. IGSMAIL–6355(http://igs.org/pipermail/igsmail/2011/006347.html), 2011.

200

References
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, G. Wöppelmann, and P. Woodworth. In: Dach andJean (eds.), Technical Report 2013, International GNSS Service, pp. 177–181, University of Berne, 2014. http://kb.igs.org/hc/en-us/article\underbarattachments/
200880813/2013\underbartechreport.pdf
Teferle, F.N., A. Hunegnaw, S.D.P. Williams, P.R. Foden, and P.L. Woodworth. Recent
Activities at the King Edward Point Geodetic Observatory, South Georgia, in Support
of TIGA Objectives. IGS Workshop 2014, 23–27 June, Pasadena, USA, 2014.
Steigenberger, P., M. Rothacher, R. Dietrich, M. Fritsche, A. Rülke, and S. Vey. Reprocessing of a global GPS network. Journal of Geophysical Research 111:B05402, 2006.
DOI: 05410.01029/02005JB003747.
Wöppelmann, G., M. Marcos, A. Santamaria–Gomez, B. Martin Miguez, M–N. Bouin,
and M. Gravelle. Evidence for a differential sea level rise between hemispheres over
the twentieth century. Geophysical Research Letters, 41:1639–1643, 2014.

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TIGA Working GroupAppendix A. TIGA Working Group Members in 2014
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
Simon Williams
Gary Mitchum
Mark Merrifield
Matt King

TAC, TNC, TDC
TAC
TAC

University La Rochelle
DGFI Munich
BGK, Frankfurt
GeoScience Australia
ANU
GFZ Potsdam
BGK, Frankfurt
University of Luxembourg
University of Nottingham
ex officio
ex officio
CDDIS, NASAGFZ Potsdam
PSMSL, NOC Liverpool
University of SouthFlorida
UHSLC, Hawaii
University of Tasmania

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

202

TAC
Combination
TAC/CombinationTAC
IGS Central Bureau
IGS AC coordinator
TDC
Chair TIGA–WGPSMSLGLOSS GE (current chair)
GLOSS GE (past chair)Troposphere Working Group
Technical Report 2014
C. Hackman, S. M. Byram
United States Naval Observatory
3450 Massachusetts Avenue Northwest
Washington DC 20392, USA
Tel: +1–202–762–1444
E–mail: christine.hackman@usno.navy.mil

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. IGS FTEs are produced within the USNO Earth Orientation Department
GPS Analysis Division, which also hosts the USNO IGS Analysis Center.
The IGS TWG is comprised of approximately 50 members (cf. Appendix A.). A revised
charter approved by the IGS Governing Board at the close of 2011 is shown in Appendix
B.

2 IGS Final Troposphere Product Generation/Usage 2014
USNO produces IGS Final Troposphere Estimates for nearly all of the 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 thegradient components used to compensate for tropospheric asymmetry.
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
function (Boehm et al. 2006) with IGS Final satellite orbits/clocks and earth orientation

203

Troposphere Working Groupparameters (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.
Figure 1 shows the number of receivers for which USNO computed IGS FTEs 2011–4.
The average number of quality–checked station result files submitted per day in 2014
was 326, comparable to the 2013 average value of 325. These files can be downloaded
from ftp://cddis.gsfc.nasa.gov/gps/products/troposphere/zpd; users downloaded
12.3 million files in 2014 (Noll 2015).
USNO will use Bernese GNSS Software 5.2 (www.bernese.unibe.ch/features) to compute troposphere estimates for the IGS Reprocessing 2 effort (http://acc.igs.org/
reprocess2.html).
The IGS estimates GNSS–related parameters, e.g., satellite orbits, satellite–clock corrections, in 24–hour batches, causing discontinuities to appear between parameter values
computed at the end of one 24–hr measurement block and the beginning of the next. (The
GNSS measurements themselves are recorded continuously.) IGS FTEs exhibit such day–boundary discontinuities of about 4 − 7 mm RMS (depending on location), complicating
IGS FTE use in certain meteorological applications. Research is ongoing at Technische Universität München to characterize and then minimize these discontinuities. Steps
forward were made in a bachelor’s thesis by Gauges (Gauges 2014), who, in studying day–

Number, QC-ed Tropo Files Submitted to IGS

350

update station list

improved results screening# receivers for which files submitted

400

300

250
2011
mean: 322

2012
mean: 302

2014
mean: 326

2013
mean: 325

200
0

365

730
days since 1 Jan 2011

1095

1460

Figure 1: Number of IGS receivers for which USNO produced IGS Final Troposphere Estimates,
2011–4. (Estimates were produced by Jet Propulsion Laboratory up through mid–April
2011.)

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3 IGS Troposphere Working Group Activities 2014
boundary discontinuities at 30 locations, observed that the RMS discontinuity size at agiven location was ultimately linked to the size of the zenith troposphere delay itself. A
procedure to minimize the discontinuities is under development.

3 IGS Troposphere Working Group Activities 2014
The goal of the IGS Troposphere Working Group is to improve the accuracy and usabilityof GNSS–derived troposphere estimates. It works toward this goal by coordinating (a)technical sessions at the IGS Analysis Workshop and (b) working–group projects.
The group meets twice per year: once in the fall in conjunction with the American Geophysical Union (AGU) Fall Meeting (San Francisco, CA, USA; December), and once inthe spring/summer, either in conjunction with the European Geosciences Union (EGU)
General Assembly (Vienna, Austria; April) or with the biennial IGS Workshop (location
varies; dates typically June/July).
Meetings are simulcast online so that members unable to attend in person can participate.
Members can also communicate using the IGS TWG email list.
In this section, we first summarize TWG–coordinated technical and splinter sessions which
took place at the 2014 IGS Workshop. We then report on the status of current TWG
projects. We then summarize the Fall AGU 2014 TWG splinter–group meeting.

2014 IGS Workshop technical/splinter sessions coordinated by the IGS
TWG
The IGS Workshop took place 23–27 June 2014 in Pasadena, CA. The IGS TWG coordinated three sessions: an oral plenary session in which speakers presented large–scale
projects related to estimation or application of GNSS–based troposphere estimates, aposter session in which maximum participation was sought in order to foster technicalexchange, and an IGS TWG splinter meeting.
Plenary Session PY09A, GNSS–Derived Troposphere Delays, 26 June 2014, featured thefollowing presentations (speaker’s name bolded) which also can be accessed at http://igs.org/workshop/plenary:• On the COST Action GNSS4SWEC1 project, which uses GNSS–derived troposphereestimates for severe–weather forecasting:
Advanced Global Navigation Satellite Systems Tropospheric Products for Monitor1

European Cooperation in Science and Technology (COST) Advanced Global Navigation Satellite Systems Tropospheric Products for Monitoring Severe Weather Events and Climate: http://www.cost.
eu/COST_Actions/essem/Actions/ES1206

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Troposphere Working Grouping Severe Weather Events and Climate (GNSS4SWEC), G. Guerova2 , J. Jones,
J. Douša, G. Dick, S. de Haan, E. Pottiaux, O. Bock, R. Pacione, G. Elgered, and
H. Vedel• On the World Meteorological Observation GRUAN3 project, which (among otherthings) uses GNSS–derived troposphere values to study climate change:
Global Precipitable Water Trend and its Diurnal Asymmetry Based on GPS, Radiosonde and Microwave Satellite Measurements, J. Wang4 , A. Dai, and C. Mears• On the (IGS–coordinated) development of a database/website automating the comparison of troposphere estimates derived from independent techniques (e.g., GNSS,VLBI, radiosondes, and weather models):
Development Towards Inter–Technique Troposphere Parameter Comparisons andTheir Exploitation, J. Douša5 , S. Byram, G. Gyori, O. Böhm, C. Hackman, andF. ZusPoster Session PS05, Estimation and Application of GNSS–Based Troposphere Delay(25 June, 2014) featured 18 contributions, which can be viewed at http://igs.org/
workshop/posters.
The splinter meeting (25 June 2014; simulcast via gotomeeting.com) featured the following presentations on current WG projects, plus discussion of past/future directions:• IGS Troposphere Working Group Meeting, C. Hackman• Status of Developments for Tropospheric Parameter Comparisons, J. Douša, S. Byram,
G. Gyori, O. Böhm, C. Hackman, and F. Zus• Draft Proposal for Tropospheric Format Update, R. Pacione6 and J. Douša

These presentations were distributed via the IGS TWG email list (message IGS–TWG–
102) and can also be obtained by contacting this report’s author.

IGS Troposphere Working Group Projects
As mentioned previously, the goal of the IGS Troposphere Working group is to improve
the accuracy and usability of GNSS–derived troposphere estimates. One way to assess
the accuracy of GNSS–derived troposphere estimates is to compare these estimates tothose obtained for the same time/location using independent measurement techniques,2

Sofia University (Bulgaria)
GCOS (Global Climate Observing System) Reference Upper Air Network: http://www.gruan.org
4
University at Albany, SUNY; National Center for Atmospheric Research (both USA)
5
Geodetic Observatory Pecný (Czech Republic)
6
e–GEOS SpA, ASI/CGS, Matera, Italy
3206

3 IGS Troposphere Working Group Activities 2014
e.g., VLBI (Very Long Baseline Interferometry), DORIS (Doppler Orbitography and Radiopositioning Integrated by Satellite), radiosondes, or from numerical weather models.
The IGS TWG has therefore since 2012 been coordinating the creation of a database/website
to automatically and continuously perform such comparisons.
Dr. Jan Douša, Geodetic Observatory Pecny (GOP; Czech Republic) has been spearheading the development of the database (Douša and Gyori 2013; Gyori and Douša 2015),
with contributions from other scientists at GOP and at GeoForschungsZentrum (GFZ;
Germany). This database is nearly complete: it already can (and does) download andcompare troposphere values from a wide variety of sources, compensating for horizontal
and vertical separation of measurement locations. Development of the website by whichusers can view/access the values is underway as well, with USNO augmenting initial GOP
efforts. USNO has also begun contributing to database development, as well as the sourcing of auxiliary databases/servers.
In 2014, a grant proposal, Automated Intra– and Inter–technique Troposphere Estimate
Comparisons, made to the Kontakt II Czech–US research partnership by Dr. Douša withsupporting documents authored by WG chair C. Hackman, was funded.
This funding supports, in addition to other items, travel to the US for joint US–Czech
work on the database/website. Dr. Douša thus worked with USNO scientists on further
website/database development during a Kontakt II funded USNO site visit 2–14 Nov
2014. Such short, focused co–work visits enable large steps forward, e.g., the installationof a second database at USNO, familiarization of USNO staff with database features, and
USNO–GOP joint work on designing interface structure.
Fig. 2 illustrates how the user interface to the website/database might appear. Completion of this project is expected in 2016. This system has received interest from climatologists/meteorologists, e.g., those associated with the GRUAN and COST Action
GNSS4SWEC projects, as it will simplify quality–comparison and perhaps acquisition ofdata used as input to their studies.
The IGS Troposphere Working group is also supporting a project to standardize thetropo_sinex format in which troposphere delay values are disseminated and exchanged.
At issue is the fact that different geodetic communities (e.g., VLBI, GNSS) have modified the format in slightly different ways since the format’s introduction in 1997. To takeone simple and relatively benign example, text strings STDEV and STDDEV are used
to denote standard deviation in the GNSS and VLBI communities respectively. Suchfile–format inconsistencies hamper inter–technique comparisons.
This project, spearheaded by IGS Troposphere WG members R. Pacione and J. Douša,
is being conducted within the COST Action GNSS4SWEC Working Group 3. This
COST WG consists of representatives from a variety of IAG (International Association of
Geodesy) organizations and other communities; its work is further supported by the EU-

207

Troposphere Working Groupclick-able station map, list

graphs up to six
stations withmultiple techniquecomparisonsuser definedcomparison
graph

Figure 2: Early drafts: two parts of user (website) interface to troposphere–comparison database.
(Top) User can choose locations and sources for which s/he would like to compare
values. (Bottom) User can request measurement files.

208

3 IGS Troposphere Working Group Activities 2014
REF Technical Working Group7 as well as E–GVAP8 expert teams. The WG is currently
defining in detail a format able to accommodate both troposphere values and the metadata(e.g., antenna height, local pressure values) required for further analysis/interpretation of
the troposphere estimates.

IGS Troposphere Working Group Meeting, 16 December 2014, San
Francisco, CA (simulcast via gotomeeting.com)
This meeting featured status reports on WG projects, a report from the GNSS4SWEC
team, research–paper contributions by groups unable to attend, and a discussion of troposphere–
estimate day–boundary discontinuities.
The presentations and papers were distributed via the IGS TWG email list (message
IGS–TWG–115), and can also be obtained by contacting this report’s author.
• Presentations:– IGS Troposphere Working Group Meeting, C. Hackman– GNSS4SWEC Update – G. Guerova and the GNSS4SWEC team• Discussion: cause & amelioration of day–boundary discontinuities in IGS Final Troposphere Estimates, based partly on results presented in Gauges 2014.
• Publications contributed to the meeting:– J. Böhm, G. Möller, M. Schindelegger, G. Pain, and R. Weber. “Developmentof an improved empirical model for slant delays in the troposphere (GPT2w),”
GPS Solutions, DOI 10.1007/s10291–014–0403–7, 2014. (MATLAB source code
here: http://ggosatm.hg.tuwien.ac.at/DELAY/SOURCE/GPT2w)– B. Federici, I. Ferrando, and D. Sguerso. “GM24P: GNSS monitoring to predict
potential precipitation,” Community Protection Expo, 9–11 December 2014,
Genoa IT, 2014. domenico.sguerso@unige.it– L. Morel, E. Pottiaux, F. Durand, F. Fund, K. Boniface, P. Sergio de Oliveira
Junior, and J. Van Baelan. “Validity and behaviour of tropospheric gradients
estimated by GPS in Corsica,” Advances in Space Research, 55:135–149, 2015.
http://dx/doi/org/10.1016/j.asr.2014.10.004
78

http://www.euref.eu/euref_twg.html
EUMETNET EIG GNSS Water Vapour Programme; http://egvap.dmi.dk

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Troposphere Working Group

4 How to Obtain Further Information• IGS Final Troposphere Estimates can be downloaded from: ftp://cddis.gsfc.
nasa.gov/gps/products/troposphere/zpd• For technical questions regarding them, please contact Dr. Sharyl Byram at sharyl.
byram@usno.navy.mil or Dr. Christine Hackman, christine.hackman@usno.navy.
mil.
• To learn more about the IGS Troposphere Working Group, you may:
– contact Dr. Christine Hackman at christine.hackman@usno.navy.mil– visit its website (under development): http://igs.org/projects-working-groups/
twg, and/or– subscribe to its email list: http://igscb.jpl.nasa.gov/mailman/listinfo/
igs-twg

5 Acknowledgements
Development of the troposphere–comparison database/website is supported by KONTAKT II project number LH14089. The IGS Central Bureau is thanked for allowing
use of its gotomeeting.com subscription.

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. GeophysicalResearch Letters, 33(7):L07304, 2006.
Dach, R., U. Hugentobler, P. Fridez, and M. Meindl. Bernese GPS Software Version 5.0(User Manual). Astronomical Institute, University of Bern, Astronomical Institute of
University of Bern, Bern, Switzerland, 2007.
Douša, J., S. Byram, G. Gyori, O. Böhm, C. Hackman, and F. Zus. Development Towards
Inter–technique Troposphere Parameter Comparisons and Their Exploitation. IGS
Workshop 2014, Pasadena CA, 2014.
Douša, J. and G. Gyori. Database for Tropospheric Product Evaluations – Implementation
Aspects. Geoinformatics, 10:39–52, 2013.

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References
Gauges, R. Validierung der mit GPS geschätzen Troposphärenparameter des IGS, (Validation of IGS GPS–Estimated Troposphere Parameters). Bachelor’s thesis, Technische
Universität München, Munich, Germany, 2014.
Gyori, G. and J. Douša. GOP–TropDB Developments for Tropospheric Product Evaluation and Monitoring – Design, Functionality and Initial Results. IAG Symposia
Series, 143 (in press), Springer, 2015.
Noll, C. Personal Communication. NASA Goddard Space Flight Center, http://cddis.
gsfc.nasa.gov, 2015.
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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Troposphere Working GroupAppendix A. IGS Troposphere Working Group Members
Last NameFirst Name

Institution

Country

Ahmed
Amirkhani
Bar–Sever
Bevis
Bosser
Bock
Boehm
Bosy

FurqanMohammadYoaz
Mike
PierreOlivier
Johannes
Jaroslaw

Luxembourg
Iran
USA
USA
FranceFranceAustria
Poland

Braun
Byram
Byun
CaloriCao
Chen
Colosimo
Crespi
Deng
Dick
Douša
Drummond
Ghoddousi–Fard
Guerova
GutmanHackmanHeinkelmann
Herring
Hilla
HobigerJohn
SharylSung
AndreaWei
Junping
Gabriele
MattiaZhiguoGalina
Jan
Paul
Reza
Guergana
Seth
Christine
RobertTom
SteveThomasJones
Langley
LeandroLeighton
Liu
Melachroinos
MoellerJonathanRichardRodrigoJon
GeorgeStavros
GregorUniversite du Luxembourg
Islamic Azad Univ. Tehran
Jet Propulsion Laboratory (JPL)
Ohio State University
ENSG/DPTS
IGN–LAREG
TU WienInstitute of Geodesy andGeoinformatics; Wroclaw Universityof Environmental and Life Sciences
UCAR
USNO
JPL
Univ. Roma, La Sapienza
Univ. New Brunswick
Shanghai Astronomical Observatory
Univ. Roma, La Sapienza
Univ. Roma, La Sapienza
GFZ
GFZ
GOP
TrimbleNatural Resources Canada
Univ. Sofia
NOAA
USNO
GFZ
MIT
NGS/NOAA
Onsala Space Observatory;
Chalmers Univ. of Technology
Met Office UK
Univ. New Brunswick
Hemisphere GNSS
3vGeomatics
Hong Kong Polytechnic University
Geoscience Australia
TU Wien

212

USA
USA
USA
Italy
Canada
China
Italy
Italy
Germany
Germany
PolandUSA
CanadaBulgaria
USA
USA
Germany
USA
USA
SwedenUK
CanadaUSA
Canada/UK
Hong Kong
Australia
Austria

Appendix A. IGS Troposphere Working Group Members
Moore
Negusini

Angelyn
Monia

Nordman
PacionePalamartchouk
Penna
Perosanz
Pottiaux
Prikryl

MaariaRosa
Kirill
Nigel
Felix
Eric
Paul

RockenRoggenbuck
Rohm
RomeroSantosSchaerSchoenChris
Ole
WitoldNacho
MarceloStefanSteffen

SguersoDomenico

Soudarin
TeferleTraceyvan der Marel
Wang
WillisLaurent
NormanJeffrey
Hans
Junhong
PascalXu
Zhang

Zong–qiu
Shoujian

JPL
Inst. Radioastronomy (IRA);
Nat’l. Inst. Astrophysics (INAF)
Finnish Geodetic Inst.
ASI/CGS
Univ. Newcastle
Univ. Newcastle
CNES
Royal Obs Belgium
Communications ResearchCentre, Canada
GPS Solutions
BKG
Univ. Wroclaw
Canary Advanced Solutions
Univ. New Brunswick
AIUB
Inst. Erdmessung, Leibniz
Univ. HannoverLab. Geodesy, Geomatics,
GIS; Univ. Genoa
Collecte Localisation Satellites
Universite du Luxembourg
USNO
TU Delft
UCAR/NCAR
Inst. de Physique du Globede Paris
Liaoning TU
Wuhan Univ.

USA
Italy
Finland
Italy
UK
UK
FranceBelgium
CanadaUSA
Germany
PolandSpain
CanadaSwitzerland
Germany
Italy
FranceLuxembourg
USA
Netherlands
USAFrance
China
China

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Troposphere Working GroupAppendix 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/land214

Appendix B. IGS Troposphere Working Group Chartercoverage are obtained; these solutions however are discontinuous in geographic locationand time.

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.

Reference[1] Schreiner, W., C. Rocken, S. Sokolovskiy, S. Syndergaard, and D. Hunt, Estimates ofthe 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, J Geod,
85:395–413, DOI 10.1007/s00190–010–0434–y, 2011.

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EDITORaStronomIcal InStItUte
UnIverSIty of Bern

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

International Council for Science
World Data System