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International GNSS Service

Technical Report 2012
IGS Central Bureau
http://www.igs.org

Editors: R. Dach, Y. Jean
Astronomical Institute, University of Bern
Published in April 2013

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
http://www.igs.org

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

International GNSS Service

International Association of Geodesy
International Union of Geodesy and Geophysics

Edited by Rolf Dach, Yoomin Jean
Astronomical Institute, University of Bern, Switzerland,Compiled in February and March, 2013.

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 2012 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 2012.
This report is available online as PDF version at
ftp://igs.org/pub/resource/pubs/2012_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

II

Executive Reports

1

The Development of the IGS in 2012 — The Governing Board’s Perspective
U. Hugentobler

3Central Bureau
R. Neilan, S. Fisher, R. Khachikyan, J. Ceva, A. Craddock, N. Donnelly,
D. Maggert, and G. Walia

13

Analysis Centers

19

Analysis Center Coordinator
J. Griffiths and K. Choi

21

Center for Orbit Determination In Europe
R. Dach, 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, U. Hugentobler

35

Natural Resources Canada
Y. Mireault, B. Donahue, R. Ghoddousi–Fard, P. Tétreault, F. Lahaye

47

European Space Operations Centre
T. A. Springer, L. Agrotis, J. Feltens, M. van Kints, N. Romero, F. Dilssner,
C. Flohrer, W. Enderle, R. Zandbergen

51

GeoForschungsZentrum
G. Gendt, M. Ge, T. Nischan, M. Uhlemann, G. Beeskow, A. Brandt

61

Geodetic Observatory Pecný
No report submitted

67

Centre National d’Etudes Spatiales/Collecte Localisation Satellites
S. Loyer, F. Perosanz, H. Capdeville, A. Mezerette, F. Mercier, J.–C. Marty

67v

Contents
Jet Propulsion Laboratory
S. Desai, W. Bertiger, B. Haines, D. Kuang, C. Selle, A. Sibois,
A. Sibthorpe, and J. Weiss

73

Massachusetts Institute of Technology
T. A. Herring and R. W. King

79

National Geodetic Survey
No report submitted

86

Scripps Institution of Oceanography
No report submitted

86

United States Naval Observatory
C. Hackman, S. Byram, V. Slabinski, and J. Tracey

86

Wuhan University
C. Shi, M. Li, Q. Zhao, X. Lei, J. Liu

93

EUREF Permanent Network
C. Bruyninx, H. Habrich, A. Kenyeres, W. Söhne, G. Stangl, C. Völksen

101

SIRGAS
L. Sánchez

111

III Data Centers

121

vi

Infrastructure Committee
I. Romero

123

Crustal Dynamics Data Information System
C. Noll

129

Scripps Institution of Oceanography
No report submitted

137

Institut National de l’Information Géographique et Forestière
A. Duret, and B. Garayt

137

Korean Astronomy and Space Science InstituteNo report submitted

139

Contents

IV Working Groups, Pilot Projects

139

Antenna Working GroupR. Schmid

141

Bias and Calibration Working Group
S. Schaer

149

Clock Products Working GroupNo report submitted

153

Data Center Working Group
C. Noll

153

Ionosphere Working GroupA. Krankowski and R. Sieradzki

157

Multi–GNSS Working GroupO. Montenbruck

163

Space Vehicle Orbit Dynamics Working GroupNo report submitted

171

Reference Frame Working GroupP. Rebischung, B. Garayt, X. Collilieux, Z. Altamimi

171

Real–Time Pilot Project
M. Caissy and L. Agrotis

179

RINEX Working GroupK. MacLeod, L. Agrotis, and R. Dach

185

Tide Gauge Benchmark Monitoring Project
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, P. Woodworth, G. Wöppelmann

189

Troposphere Working Group
C. Hackman and S. Byram

195

vii

Part I

Executive Reports

1

The Development of the IGS in 2012
The Governing Board’s Perspective
U. Hugentobler
Technische Universität München
Institut für Astronomische und Physikalische Geodäsie
Arcisstr. 21; 80333 Munich; Germanye–mail: urs.hugentobler@bv.tum.de

1 Introduction
The year 2012 was a successful year for the IGS. The most prominent event was the
IGS Workshop in Olsztyn, Poland, in July where a wide range of activities associatedwith the IGS were presented and discussed. Focus areas at the workshop as well as inseveral Governing Board meetings were the challenging multi-GNSS activities organized in
IGS’ Multi–GNSS Experiment (MGEX) as well as the preparations for the launch of the
IGS Real-time Service. Essential for the IGS are all the operational activities, including
the maintenance of the tracking network by the station operators with the support of
the Network Coordinator, the data holding for free access at the Data Centers, the data
analysis and operational preparation of highest–precision products at the Analysis Centers,
the coordination and supervision of the activities by the Product Coordinators, and finally
the work contributed by the Working Groups focusing on various topics of high relevancefor the IGS, and the Central Bureau assuming responsibility for the general managementand day-to-day operations of the IGS. Important work in 2012 in addition includes the
preparation of updated site guidelines, the preparations for the upcoming next reprocessing
undertaking, the definition of the goals and objectives for the Strategic Plan 2013–2016,
the fostering of the interactions with neighboring organizations as well as the presentationof IGS activities and strategy at a number of workshops and conferences.

2 IGS Operational Activities
Although the following sections focus on recent IGS accomplishments, the IGS could notexist without the daily, routine activities performed by the various operational components

3

Hugentobler: Governing Boardof the service. About 440 stations are maintained and operated globally by many institutions and station operators, making tracking data available at different latencies, fromdaily RINEX files to real–time streams for free public use. The IGS tracking data amountheld by each of the four global Data Centers on permanently accessible servers increased in
the last year by over 1 Tb (15 million files). Significant additional storage capabilities areprovided by regional Data Centers. Twelve Analysis Centers and a number of Associate
Analysis Centers utilize tracking data from 70 up to more than 350 stations to generate
and to control the quality of highest–precision products up to four times per day. Product
Coordinators combine these products on an operational basis and assure the quality ofthe products made available to the users. Nearly 700 IGS final, rapid, ultra–rapid and
GLONASS–only product files as well as 140 ionosphere files are made available per week
as well as daily troposphere files for more than 300 stations. The interest of users on IGS
products is documented by the download statistics that records typically over 150 000 file
(25 Gb) downloads per day (CDDIS statistics). The Central Bureau assumes responsibility for day–to–day management, interaction with station operators, and answering to atypical number of 150–200 questions and requests from users per month. All these activities are performed all year and day–by–day, with high redundancy and reliability basedon the pooled resources of more than 200 institutions worldwide. Only the day–by–day
contribution of a large number of engaged individuals makes this impressive undertaking
possible.

3 IGS Workshop 2012 in Olsztyn, Poland
The most prominent IGS event in 2012 was, without doubt, the IGS Workshop thattook place in Olsztyn, Poland, from 23–27 July. The workshop was attended by about
230 participants and was a great success. It took place in the excellent facilities of the
University of Warmia and Mazury and in a lovely region of Poland. The workshop,
organized by Andrzej Krankowski and his team, was accompanied by a diversified social
program, including an ice breaker party, conference dinner, city tour, sailing regatta, visits
in castle, planetarium, and observatory; with excellent weather experienced all week.
The workshop format developed by the Scientific Organizing Committee led by Shailen
Desai, JPL, was excellent as it left ample room for interaction and discussions, and thescientific program found the appropriate balance between the different topics of interest to
the IGS today. The mornings were devoted to plenary sessions with invited presentations
focusing on selected topics covering the wide scope of the IGS. Lunch time followed byposter sessions allowed time for discussion and interaction between the participants, while
the splinter sessions in the second half of the afternoon allowed the working groups tomeet, discuss their “hot” topics and formulate their recommendations.
The scientific sessions covered the status and achievements of the IGS Multi–GNSS Experiment; the IGS network infrastructure and real–time activities; modeling of observations and station motions; modeling of atmosphere delays and applications; space vehicle44 Events and Highlights in 2012
dynamics and attitude; clock modeling and time scale realization; antenna calibration;
geodetic applications of IGS products; the relevance of the IGS for the geodetic and wider
community. Jointly with the IGS Workshop the meeting of the WG-A “Compatibility andInteroperability” of the International Committee on GNSS (ICG) took place, which was
an opportunity for interaction and exchange between IGS and system providers.
The workshop presentations, posters, and recommendations can be found at http://www.
igs.org/presents/poland2012/. A short workshop summary may be found in IGSMAIL#6635 .

4 Events and Highlights in 2012
The IGS Governing Board met a total of four times in 2012. A GB business meeting
took place on April 25 during the EGU General Assembly in Vienna, a regular meeting(July 22) and a wrap–up GB meeting (July 27) was associated with the IGS Workshop in
Poland, and finally the regular end-of-year meeting took place on December 2 during theAGU Fall Meeting in San Francisco. The IGS Executive Committee - consisting of Urs
Hugentobler, Chuck Meertens, Ruth Neilan, Chris Rizos, Tim Springer and with regularparticipation of John Dow and Steve Fisher and of WG Chairs as required — has met ten
times in 2012 by teleconference.
The Multi–GNSS Experiment (MGEX) is one of the key projects of the IGS and shows
significant progress since its launch in February 2012. The focus of this cornerstone experiment is the data flow, the understanding of observables, the characterization of the
tracking equipment, and the generation of products, targeting the launch of a Pilot Projectin 2015. To achieve this goal contributions from all IGS components are essential. The
project is open and everybody who is interested to contribute is invited to join. After the
IGS workshop, Robert Weber stepped down as Chair of the GNSS WG which coordinates
MGEX. The GB thanked Robert for his engagement over many years and welcomed Oliver
Montenbruck from DLR/GSOC, Germany, as the new Chair of the working group thatwas renamed to Multi–GNSS WG. The very successful Workshop on GNSS Biases held inBern from January 18–19 addressed very significant issues related to the implementationof multi–GNSS within IGS.
The upcoming IGS Real–Time Service is our second key project. The redundancy concept
is convincing and the demonstrated product accuracy mature for the launch of the Service.
Initial Operational Capability is planned for early 2013, providing real–time GPS orbit
and clock corrections as well as experimental GLONASS corrections, with Full Operational
Capability later in 2013. The Service will rapidly develop into a Multi–GNSS Service. Its
focus are geophysical applications, e.g., natural hazards monitoring in the framework of
GGOS, but it will support a large variety of applications in positioning, navigation, timetransfer, system monitoring and others. NRCan committed to support Mark Caissy for
another year as the Chair of the RT WG to allow for continuity in leadership in the process5

Hugentobler: Governing Boardof launching the RT Service, while ESA continues the support of Loukis Agrotis as the
RT ACC.
The IGS/RTCM RINEX WG is preparing a plan for the transition from RINEX 2.11 to
RINEX 3.0x over the next few years. While tracking data from GNSS–capable equipment
shall be solely available in RINEX 3 after a target date to be specified, tracking data fromlegacy receivers will continue to be available in RINEX 2 for the foreseeable future. The
IGS GB affirmed the transition to RINEX 3 and the further elaboration of the transition
plan.
The Infrastructure Committee invested much effort in a thorough revision of the IGS Site
Guidelines. The guidelines were available for public review and were approved at the July
GB meeting subject to final comments being integrated. At its July meeting the GB
assigned Robert Khachikyan, CB staff member, as Network Coordinator. With this, oneof the key positions within the IGS CB is again filled. Finally, the GNSS Research Centerat Wuhan University joined the IGS as a new Analysis Center.
Summaries of the GB meetings may be found in IGSMAIL #6635 and IGSMAIL #6706.
Table 1 lists the important events in 2012.

Table 1: IGS events in 2012

January 18-19 IGS Workshop on GNSS Biases
February 1 Start of MGEX
April 25 GB Business Meeting in Vienna (EGU)
July 22 40th GB Meeting in Olsztyn, Poland• Robert Khachikyan assigned as Network Coordinator
July 23-27 IGS Workshop in Olsztyn, Poland
joint Meeting with ICG WG-A “Compatibility and Interoperability”
July 27 GB Workshop Wrap-up Meeting• Oliver Montenbruck assigned as Chair of the Multi–GNSS WG• approval of new Site Guidelines
December 2 41st GB Meeting in San Francisco (AGU)• Steve Fisher assigned as IGS CB Secretary67 Outreach

5 Strategic Planning
During 2012 the new IGS Strategic Plan 2013–2016 was developed by the IGS CB and EC
as an updated version of the current Strategic Plan 2008–2012, including elements thatallow for a better monitoring and reporting of progress. As a preparatory step a SWOT
(Strengths, Weaknesses, Opportunities, and Threats) analysis was performed by membersof the GB and selected stakeholders, analyzing strengths, weaknesses and opportunitiesof the IGS, and threats that the IGS faces. The analysis resulted in three goals thatessentially correspond to the goals formulated in the current plan. The goals are further
sub-divided into several objectives which in turn are decomposed into initiatives. Targets
and measures are being defined allowing to assess the status of each objective with respect
to the target for regular monitoring by the GB. At the same time the CB prepared a
Progress Report for the period 2008–2012 that records and quantifies, based on the annual
implementation plans, the progress made by the IGS in the different fields addressed by
the Strategic Plan. The final version of the two documents will be available early 2013.

6 Governing Board Membership
In 2012 no elections took place. The GB membership of Steve Fisher as IGS CB Secretary
was approved by the Board. Given the successful review of the work of the IGS Working
Groups and Pilot Projects documented with the very successful IGS Workshop in Olsztyn,
the GB extended the terms of those WG and PP Chairs whose terms terminated endof 2012 by another two years.
Table 2 lists the members of the IGS Governing Board for 2012.

7 Outreach
The IGS is well represented on the GGOS Coordinating Board. It plays a leadership role in
the International Committee on GNSS (ICG), in particular by co–chairing Working GroupD on Reference Frames, Timing and Applications, and by participating in the planningfor the International GNSS Monitoring and Assessment System (iGMAS). The IGS is also
well represented in the International Earth Rotation & Reference Systems Service (IERS)
and in IAG Sub–Commission 1.2 on reference frames, in the RTCM SC104, and others.
IGS has been involved with many outreach activities in 2012. The following list provides
a selection of presentations at international meetings and articles in geospatial magazines.
In addition the IGS CB together with the RT WG prepared a one-pager that states thereasons for the IGS involvement in real–time activities. The IGS was also given visibility
as session organizers of, or presenters in, IGS–related sessions at conferences such as thoseof the EGU in Vienna and AGU in San Francisco.

7

Hugentobler: Governing Board
Presentations at international meetings• PPP–RTK Symposium, March 12–13, Frankfurt/Main, U. Hugentobler:“From GPS to GNSS — Challenges and Prospects”.
• FIG Working Week, May 6–10, Rome, R. Neilan:“The IGS in Support of Science and Society — new Roles, New Challenges, New
Products”.
• 3rd China Satellite Navigation Conference, May 15–19, Guangzhou, C. Rizos:“The IGS in the Multi–GNSS Era: New Roles, New Products, New Challenges”.
• Asia Oceania Geoscience Society, August 13–17, C. Rizos and R. Neilan:“New Roles, New Challenges and New Products for the International GNSS Service(IGS)”.
• 3rd Colloquium Galileo Science, August 31–September 2, Copenhagen, R. Weber:“The IGS Multi-GNSS Global Experiment”.
• INTERGEO, October 9–11, Hannover, C. Rizos:“The International GNSS Service (IGS): Supporting the Geospatial Industry”.
• ICG–7, November 5–9, Beijing, C. Rizos:“The IGS: A Multi-GNSS Service”.
Articles• Caissy, M., L. Agrotis, G. Weber, M. Hernandez–Pajares, U. Hugentobler: “Coming
Soon: The IGS Real-Time Service”, GPS World, June 2012.
• Rebischung, P., J. Griffiths, J. Ray, R. Schmid, X. Collilieux, B. Garayt: “IGS08:
the IGS realization of ITRF2008”, GPS Solutions, 16(4):483–494.
• Rizos, C.: “GNSS Service Analysis Workshop Held in Poland”, GIM International
Magazine, November 2012.
• Weber, R., U. Hugentobler, R. Neilan: “IGS M–GEX — The IGS Multi-GNSS
Global Experiment”, Proceedings of the 3rd International Colloquium on Scientificand Fundamental Aspects of the Galileo Program.
One–pager• “Why Is IGS Involved in Real-Time GNSS?” (ftp://igs.org/pub/resource/pubs/
IGS_why_in_RT.pdf)

88 Outlook

8 Outlook
The year 2013 again promises a number of highlights. In the beginning of 2013 Initial
Operational Capability for the IGS Real–Time Service will be declared as a new open
service. Full Operational Capability is planned later in 2013. Rapid progress is expectedin the Multi–GNSS Experiment which prepares IGS to a seamless integration of the new
and upcoming GNSS constellations into its processing chains and products. Also for the
beginning of 2013 the launch of the second reprocessing campaign (repro2) is planned forwhich a multitude of preparatory steps were performed in 2012 by the Analysis Center
Coordinator and Reference Frame Coordinator together with the Analysis Centers. Finally
the new Strategic Plan 2013–2016 will be implemented early 2013. For 2014 we can alreadylook forward to our next workshop at JPL in Pasadena, CA, coinciding with the 20th
anniversary of the IGS.
The IGS GB thanks all participants and supporters of the IGS for their efforts invested
in the past year. Only with the continuous efforts of the network operators, operators ofdata centers and analysis centers, the product coordinators, WG, PP and committee chairs
and members, the Central Bureau, and the continuous support by numerous institutions
worldwide the IGS can remain in the leading position in a rapidly developing GNSS
environment.

9

Hugentobler: Governing Board
Table 2: IGS Governing Board Members 2012 (∗: voting members, EC: Executive Committee)
Member

∗ Urs

(EC)

Hugentobler∗ Zuheir Altamimi
Felicitas Arias∗ Claude Boucher∗ Carine Bruyninx
Mark Caissy∗ Yamin Dang
∗ Shailen Desai

Institution

Country

Function

Technische Universität
MünchenGermany

Board Chair, Analysis
Center Representative

Institut National del’Information Géographiqueet Forestière
Bureau International desPoids et Mesures
Institut National del’Information Géographiqueet Forestière
Royal Observatory of
BelgiumNatural Resources Canada

FranceIAG Representative

FranceFranceBIPM/CCTF
Representative
IERS Representative

Belgium

Network Representative

CanadaReal-Time WG Chair

Chinese Academy ofSurveying and Mapping
Jet Propulsion Laboratory

China

Appointed

USA

Analysis Center
Representative
Reference Frame
Coordinator, IGS
Representative to IAG
Sub–commission 1.2
Analysis Center
Coordinator
Troposphere WG Chair∗ Bruno Garayt

Institut National del’Information Géographiqueet Forestière

France∗ Jake Griffiths

NOAA, National Geodetic
SurveyUnited States Naval
Observatory
Geoscience Australia

USA

Australia

Network Representative

University of Warmia andMazury in Olsztyn
Natural Resources Canada

PolandIonosphere WG Chair

CanadaUNAVCO, Inc.

USA

IGS/RTCM RINEX WG
Chair
Appointed

DLR/German Space
Operations Center

Germany

Multi–GNSS WG ChairIGS Central Bureau, Jet
Propulsion Laboratory
Goddard Space Flight Center

USA

Korean Astronomy andSpace Science Institute
University of New SouthWales
ESA/European Space
Operations Centre
Federal Office of Topography

South Korea

Director of IGS Central
Bureau, Secretary
Data Center Representative,
Data Center WG Chair
Appointed

Australia

President of IAG

Germany

Infrastructure Committee
Chair
Bias and Calibration WG
Chair

Christine Hackman∗ Gary Johnston

Andrzej Krankowski
Ken MacLeod∗ Chuck Meertens

Oliver Montenbrucksince July 2012

∗ Ruth Neilan (EC)∗ Carey Noll
∗ James Park
∗ Chris Rizos (EC)Ignacio Romero
Stefan Schaer

10

USA

USA

Switzerland8 Outlook

Table 2: IGS Governing Board Members 2012 (∗: voting members, EC: Executive Committee),cont.
MemberInstitution

Country

Function

Ralf Schmid

Deutsches Geodätisches
Forschungsinstitut
Deutsches
GeoForschungsZentrum
PotsdamNaval Research Laboratory

Germany

Antenna WG Chair

Germany

TIGA WG Chair

Tilo Schöne∗ Ken Senior∗ Tim Springer (EC)Robert Weber
until July 2012

∗ Richard Wonnacott
Marek Ziebart

USA

Clock Product Coordinator

ESA/European Space
Operations Centre

Germany

Vienna University ofTechnology

Austria

Analysis Center
Representative, IGS
Representative to IERS,
Chair of Associate Members
Committee
GNSS WG Chair

Chief Directorate: National
Geospatial Information
University College London

South Africa

Appointed

UK

Space Vehicle Orbit
Dynamics WG Chair

11

Hugentobler: Governing Board

12

IGS Technical Report 2012
Central Bureau
R. Neilan1 , S. Fisher1 , R. Khachikyan2 , J. Ceva3 ,A. Craddock3 , N. Donnelly5 , D. Maggert4 and G. Walia1
1
2
3
4
5

NASA/Jet Propulsion Laboratory, Caltech, Pasadena, California
Raytheon, Inc.
SBAR, Inc.
UNAVCO, Inc
Land Information New Zealand (LINZ)

1 Introduction
The IGS Central Bureau (CB) is hosted at the California Institute of Technology/Jet
Propulsion Laboratory and is funded by NASA. The Central Bureau supports IGS management focusing on two principal functions:
1. executive management of the service, including international coordination and outreach, and
2. coordination of IGS infrastructure, including the IGS tracking network and related
information management systems.
Specific responsibilities of the Central Bureau are outlined in the IGS Terms of Reference:
http://igs.org/organization/orgindex.html .
The CB has been strengthened in 2012. Additional resources provided by NASA have enabled an expansion of CB staff. The CB Director is now partially tasked within the NASA’s
Space Geodesy Project. Her efforts within the IGS are now backfilled by other staff members: Juan Ceva came on board part time in April, Allison Craddock in September, bothpart time; and Steve Fisher has been fully dedicated to IGS since November. Robert
Khachikyan was appointed Network Coordinator at the 40th GB meeting in Poland. Dave
Maggert at UNAVCO supports IGS and network coordination, and provides extremely
valuable support to the IGS CB and IGS in general. Nic Donnelly interned (on loan from
LINZ) at the CB in early 2012 gaining insight into CB tasks and made good progress ina path forward for definition of geodetic meta–data.

13

Neilan et al.: Central Bureau

2 Network Status
The Central Bureau currently monitors 440 official IGS stations of which approximately
84% are actively transmitting data. Only 244 stations are GPS only. All others are
GNSS. Approximately 107 IGS stations transmit real–time data to the IGS Real Time
Pilot Project.
16% data missing are due to temporary outages, while others are actively being worked
on to restore operation. Eighteen of these stations are NGA stations for which we are
evaluating data prior to release to Analysis Centers. The NGA stations currently have
two issues that must be addressed.
1. Use of uncalibrated antenna and radome equipment. The IGS Antenna Working
group is actively working with NGS for it to become one of the official IGS antenna
calibration institutions. Once details are corrected, this issue becomes addressed.
2. Data contains 12 cycle phase slip that affects geodetic solutions. Which is a RINEX
violation, although data can possibly be processed by the Analysis Centers temporarily until manufacturer produces a receiver firmware update. A single AC confirmed
its successful processing, but others need to verify.
Three new important stations have been added to the IGS network providing not only
real–time service, but also a GNSS observation data.
BRUX Brussels, Belgium
KAT1
Katherine, North Territory, Australia
MGUE Malargue, Argentina
Due to number of RF stations retiring from service and position discontinuities, IGb08
was adopted on GPS week 1709 (07 Oct 2012). IGb08 includes 33 stations affected byposition discontinuities from IGS08 and 3 new stations co–located with decommissioned
IGS08 stations. This update increases the number of usable RF stations by about 36
and the number of usable core stations by about 15. The primary goal is to stabilize theRF alignment of the IGS products.
The Central Bureau is now hosting an official real–time caster that is accessible worldwide.
We are in alpha test mode of this new service to ensure integrity is passed and verificationand validation of products are blessed. This new service works in conjunction with theprimary IGS real–time caster by ingesting direct feeds from the IGS Real–Time Analysis
Centers. The current streams accepted are IGS clocks, orbits, and the IGS combinationfrom two different analysis centers.
Site Guidelines have been completed with the exception of the real–time section, which isin progress.

14

3 Activities in 2012
A number of Central Bureau Information System (CBIS) improvements are in progress:• The new http://www.igs.org is being tested and enhanced for its promised capabilities on an external stage server. This not only addresses accessibility issues,
but also allows working group chairs to maintain their area of workspace including
station operators for their site logs.
• The new IGS Network station list and summary page is open for testing by the
Analysis Centers. So far outcome has been positive.
– Its data is supplied by the CB Site Log Manager database.
– A full history of a site’s performance is also available.
– http://igs.org/network/network.php

3 Activities in 2012
The CB has supported IGS broadly throughout 2012. Principal activities have included:
January• Participated in Bias and Calibration Workshop in Bern, and the joint IGS RTCM
meeting just prior.
• M–GEX project support and website initiated.

February – March• Attended UNAVCO Science Workshop in Boulder and organized a one day workshop
with Nic Donnelly there on geodetic meta–data, joint with Fran Boler, lead of theSeamless Archive project.
• Neilan and Donnelly met with SOPAC personnel in San Diego to discuss meta–dataapproach and an initial demonstration.
• Preparations for IGS workshop in July began.
• Meeting of the US PNT Advisory Board in Washington, DC focused on LightSquare
spectrum issue, was attended by Neilan(and Beutler).
• Network performance metrics were specified. Development of improved network
pages began.
April – May• Neilan attended the EGU in Vienna, and the GGOS Coordinating Board Meeting.
• Neilan was elected to Vice–Chair of GGOS.
• Neilan (and Rizos) attended FIG meeting in Rome, delivered an invited IGS presentation.
• Neilan, Fisher (and Rizos) in cooperation with the Real–time Working Group drafted
one–page statement on IGS involvement with Real–time GNSS.
• Plan to renew IGS Strategic Plan is developed.
15

Neilan et al.: Central Bureau• Began compiling IGS bibliography.
• IGS contribution to IERS 2011 Annual Report was prepared.
• Network performance prototype web pages developed.

June• Extensive preparations for the IGS workshop in Poland. IGS Institute is able to process Workshop registrations, which required significant development and handling.
• GGOS held a strategic retreat in Frankfurt, facilitated by CB, which is resulting ina task matrix aligned with GGOS goals and objectives.
• CB contribution to 2011 Technical Report was prepared.
• 2013 Strategic planning process is initiated.
• 2012 SIP mid year review conducted.

July• Provided significant support to IGS Workshop.
• CB personnel supported the technical aspects of the workshop, compiled workshop
archive of Workshop proceedings: http://igs.org/presents/poland2012/• Organized and managed the GB meetings, minutes and actions, follow–up on many
workshop actions (into August).
• Khachikyan assigned as Network Coordinator to be reviewed in a years time.
• 2012 Workshop accounting completed, registration funds transferred to UWM.

August• Neilan (and Rizos) attended the AOGS meeting in Singapore. An IGS invited presentation was given by Rizos, Neilan participated in the IAG Executive, visited
Earth Observatory Singapore, NTU hosted by S. Erikson. Rizos and Dawson, metwith deputy director Paramesh.
• IGS Strategic Planning web questionnaire was opened, requesting broad feedback
from IGS stakeholders.
• 2008–2012 extensive analysis of progress completed in preparation for Strategic Plan
Development. Impact of IGS activities on strategic goals and objectives was conducted.
September• US PNT Advisory Board attended by Ceva as observer.
• Strategic planning questionnaire closes, draft summary developed.
• CB develops plan for Real–time Service support — caster and website.
• Integrated review comments into 40th GB minutes.
• IGS Institute 2011 financial report and non–profit compliance report prepared andsubmitted to US Internal Revenue Service.
• CB participates in GGOS Frankfurt retreat preparations16

3 Activities in 2012
October• ICSU World Data System Scientific Committee in Taiwan on Margins of the CO–
DATA meeting. Accreditation criteria and application developed further, IGS expected to move to Network Member, rather than regular member, due to the extensive structure of the IGS.
• Central Bureau responsibility and accountability matrix, work assignments and position descriptions developed.
• Planning meeting at UNAVCO. CBIS back–up process reviewed.
• Strategic planning strengths, weaknesses, opportunities and threats (SWOT) analysis was conducted, including feedback from the Governing Board members and other
IGS participants and stakeholders.
• Real–time Service web hosting service and portal system was procured/configured.
• 2012 Workshop proceedings and recommendations were finalized and posted on theweb.
• Fisher was assigned CB Management duties.
November• IGS participated in ICG–7 in Beijing (Altamimi, Rizos, Neilan) with our FIG partners (Lilje and Higgins). Very productive meeting. WG–D on Reference Frame,
Timing and Applications proposed 4 recommendations, all passed. Discussions continued on IGS as supporting real–time monitoring and assessment within the IGMAS
committee of ICG.
• Draft Progress Report of IGS 2008–2012 was prepared and circulated for comment.
• SWOT summary analysis distributed to the GB.
• New SP goals, objectives, tasks, targets and measures proposed, discussed at the
41st GB meeting.
• Preparations for all IGS meetings in San Francisco, including GGOS meetings, AC
splinter, Trop splinter, and IDS GB meeting.
• Organization of GGOS reception, hosted by IGS and UNAVCO, with a special “Ignite
GGOS 2012!” session led by Craddock.
• 2013 Strategic plan goals drafted.
• RT product caster set–up, testing initiated.
• Governing Board meeting preparations.
• IGS rebranding initiated.
• Seamless archive discussions initiated with UNAVCO, soon with Data Centers.
December• Demonstration RT website set–up for GB.
• Progress Report of IGS 2008–2012 was completed.
• All CB staff attended/supported 41st Governing Board meeting Dec. 2 and other
IGS/IAG/GGOS related splinter meetings around AGU.
• IERS Directing Board meeting attended by Fisher.
• 41st GB minutes were drafted and circulated for comment.
• Provided focused support to Real–time Service launch.
17

Neilan et al.: Central Bureau

4 Plans for 2013
• Publish IGS Strategic Plan 2013–2016• Develop reporting mechanism based on the plan
• Develop annual implementation plan of the SP• Modernize IGS website, migrate to outside (of JPL) servers, implement new collaborative features• Support Real–time Service launch — implement real–time processes and support at
the website• ICG engagement to continue and expand• Assist in Meta–Data Workshop, joint with GGOS and FIG• Preparations for IAG 150th Meeting in Potsdam early Sept
• Prepare for 2014 IGS 20th Anniversary Workshop, Pasadena• Improve visibility of IGS within ION• Greater engagement with Asian Pacific region• Continue support of IGS EC and GB meetings• Improve support to WG and PP chairs for better information systems

18

Part II

Analysis Centers

19

Analysis Center Coordinator
J. Griffiths and K. Choi
NOAA National Geodetic Survey
1315 East–West Highway
Silver Spring, Maryland USA
e–mail: igs.acc@noaa.gov

1 Summary of Main ACC Activities
In 2012, IGS core products (see Tab. 1) were combined and distributed in a timely manner. To ensure continued production of high-quality IGS products, the Analysis Center
Coordinator (ACC) performed high–level oversight and quality control of Analysis Center(AC) products, combination performance, and maintenance of the ACC website with updated plots. Also performed was coordination among ACs to assimilate changes made bythem and to ensure that the best analysis models and procedures are used, along with coordination among the other relevant IGS components, preparation of component reports,
and coordination of the IGS 2nd reprocessing campaign.

2 Events Impacting Product Quality and Reliability
With the exception of a few unusual delays, delivery of all IGS products was generally
uninterrupted. The addition of new ACs to the IGS Ultra–rapid and Rapid products has
improved their reliability. However, the overall high quality of those two products was
unchanged from 2011. In contrast, two changes made to the Final products in preparation
for the 2nd IGS reprocessing campaign (IG2; http://acc.igs.org/reprocess2.html)
had significant impact. The following sub-sections summarize these two changes, alongwith the other events impacting the IGS products in 2012.

21

Griffiths and Choi: Analysis Center Coordinator
Table 1: IGS core product series with latency, issue times and data spans.
ID, Series

Latency

Issue times(UTC)

IGA: Ultra-Rapid(observed half)

3 − 9 hr

−24 hrat 03:00, 09:00, at 00:00, 06:00,
15:00, 21:00
12:00, 18:00

IGU: Ultra-Rapid(predicted half)

real–time+24 hrat 03:00, 09:00, at 00:00, 06:00,
15:00, 21:00
12:00, 18:00

IGR: Rapid

17 − 41 hr

IGS: Final

12 − 19 d

at 17:00, daily

Data spans(UTC)±12 hrat 12:00±12 hrat 12:00 for 7 d
weekly, each
Thursday/Friday

Remarks• for near real–timeapps• GPS & GLONASS• issued with following
IGU• for real–time apps
• GPS & GLONASS• issued with prior IGA• for near–definitive,
rapid apps
• GPS only
• for definitive apps
• GPS & GLONASS

2.1 Delays in Product Delivery
While product flow and generation were generally uninterrupted in 2012, there were a few
delays, outlined as follows:• Delays in Ultra-rapid products:– 1–July [1695_0_00 & 1695_0_06] due to logical error in ACC ftp retrieval
scripts∗ no gap in product availability due to 24 hours of predictions– 3–July [1695_2_00] combination failure due to absence of both IGU Data
Centers (DCs)∗ Ultra–rapid orbits were provided, but based on only 1 AC
∗ NASA/CDDIS planned outage & unexpected power outage at BKG DC∗ added backup DC at Royal Observatory of Belgium for increased redundancy– 26–Sep [1707_3_18 thru 1707_4_06] due to power outages at off–site location
hosting the ACC servers
22

2 Events Impacting Product Quality and Reliability∗ no gap in product availability• Delays in Rapid products– 19–Oct [1710_4] due to ACC failure to correct for issues in RINEX global
broadcast navigation (BRDC) file
∗ BRDC file issues happen from time to time; this is the first missed issue innearly 5 years∗ delayed products by ≈ 118 minutes– 25–Nov [1715_6] due to bug in combination procedures∗ orbit weight archive decreased in size, two records per day, till empty∗ delayed products by ≈ 82 minutes

2.2 New Analysis Centers
The AC at the National Geodetic Survey (NGS) developed an Ultra–rapid product andbegan contributing to the IGA/IGU combinations. Their real–time orbit predictions currently contribute with weight and perform near the middle of the group of ACs (Fig. 1).
NGS Ultra–rapid ERPs continue to be excluded since they are significantly noisier thannearly all other ACs (e.g., see Y–pole differences in Fig. 2).
The space geodesy group at Wuhan University (WHU) in China formed an AC in 2011and began contributing Ultra-rapid and Rapid products to the IGS combinations in 2012.
Their GPS and GLONASS orbits contribute fully to the Ultra-rapid combinations; theGPS part is currently performing amongst the top three ACs (Fig. 1). WHU Ultra-rapid
ERPs continue to be excluded as they often have very large departures (e.g., see Fig. 2).
WHU GPS Rapid products are included for comparison in the IGR combinations.
The added redundancy from the additional new Ultra–Rapid and Rapid ACs helps toimprove the reliability of these products lines.

2.3 Switch to Daily SINEX Integrations
Starting August 19, 2012 (GPS Wk 1702, Day 0), the IGS Final products are based ondaily terrestrial reference frame (TRF), or SINEX, integrations, marking a switch fromthe long-standing approach using weekly frames (Kouba and Mireault, 1997; Beutler etal., 1993; Ferland at al., 2000; Kouba et al., 1998). The switch to daily TRFs was inresponse to continued debate about the effects of non–tidal loading displacements on the
IGS products. Therefore, in order to facilitate further study of these effects, the IGS
adopted an approach to base the Final products on daily AC SINEX integrations. This
will allow for various models to be applied at the combination level, which should facilitate
progress toward conventional models in the future.

23

Griffiths and Choi: Analysis Center Coordinator

Figure 1: Median of the ensemble of GPS satellite orbit residuals from the 48 h IGA/IGU
combination.

Figure 2: Y–pole differences from the 24 h IGA ERP combination.

24

2 Events Impacting Product Quality and Reliability√
Products based on daily TRFs could be up to 7 ≈ 2.6 times noisier than those based on
weekly frames. Test combinations from before the switch indicated that there would be
no noticeable impact on the ERPs. Furthermore, the RMS of GPS orbits would increaseby ≈ 0.5 mm; and the RMS for the ensemble of station and satellite clocks would increaseby about 2.5 ps. Meanwhile, kinematic PPP results indicated that there would be no
noticeable change in the overall composite orbit and clock accuracy. Thus, most users
should not have noticed a change with the new orbits and clocks. The RMS of station
position residuals from the SINEX combination increased by a factor of up to 1.5, mostly in
East & Up, but much less than if the IGS errors were dominantly white noise. The North
residuals were generally less affected by the switch. Thus, the gain in temporal resolution
should be offset by little additional noise on station positions. Of course, the total producterrors, including systematic effects, are much larger than these small changes. For moredetails, see IGSMAIL #6613.
Since the adoption of daily TRFs, the relative performance of AC products remains consistent with the preliminary findings of the test period conducted before the switch. However,a comprehensive study of the impact on the IGS operational products should be made now
that more than 30 weeks have passed since the switch.
This switch to daily SINEX integrations marks the largest of changes to the IGS Final
products since 2000, when the IGS began using TRF and ERP rotations to pre-align AC
orbits (IGSMAIL #2750). This event also marks a major step toward improved inter–AC consistency w.r.t. providing truly daily products according to long-standing IGS
conventions. This is a major accomplishment and it is important to recognize the ACs fortheir tremendous efforts in the switch to daily products.

2.4 Adoption of IGb08
Starting October 7, 2012 (GPS Wk 1709, Day 0), the IGb08 update to IGS08 is used for
IGS products. The update was made to recover core reference frame stations that were
impacted by station position discontinuities induced mostly by anthropogenic sources. See
IGSMAIL #6663.

2.5 Other ACC Activities Impacting Product Quality
Study of Rotational Offset Between IGU and IGR
The IGV (test IGU GLONASS combination) was introduced on September 9, 2010, but
not widely advertised given its “experimental” status. The IGV SP3 file is mixed, withGPS and GLONASS orbits and only GPS clocks. This experimental product began with25

Griffiths and Choi: Analysis Center Coordinatorigv1601_4_06.[sum, sp3] and continues today. A recent test development in the production of the IGV was intended to improve rotational alignment, esp. in RZ, with the Rapid
orbit products, but the results were inconclusive.
Rotational misalignment of the IGS Ultra–rapid GPS orbit has been noticed for several
years. In 2010, the ACC quantified these errors (see IGSMAIL #6053), documenting large
RZ scatter (≈ 12.7 mm @ GPS) between the IGA and IGR. The underlying frame for the
IGU is intended to be similar to that of the IGR by transferring the terrestrial frameto the orbits via fixing the a priori positions of the reference frame stations. Given thesimilarity in the orbit determination strategies and even some common AC contributions,
one should expect nearly the same orbit performance of the IGRs and IGAs. Besides asmall difference in a priori EOP latency, the other main effect is probably the inclusionof the 24–hour orbit predictions when aligning the IGU AC orbits. Rotational variationsin the prediction phase are much larger than these during the observed phase.
Starting with the IGV for 1693_1_18 (18 June 2012) and ending with the IGV for
1721_3_06 (2 January 2013), a modified test combination procedure was adopted where
systematic AC orbital frame differences were determined using only the observed orbits
instead of the full 48 hours. The Helmert parameters determined in this process werethen imposed on the full 48 hours for the final IGV combination, eliminating the opportunity for orbit prediction errors to corrupt the AC orbit frame alignments. The residual
statistics and AC weights continued to be based on the full 48 hours. Results from thistest combination approach were inconclusive, suggesting that other errors dominate therotational offset with the other IGS orbits.
Study of Final Orbit Misalignment
This study was primarily motivated by biases and scatter in the AC Final orbit X– andY–rotations (RX and RY), as illustrated for ESA, NGS and SIO in Fig. 3. Also, rather
surprising results presented by Jim Ray and his colleagues at IGS Workshops and the2012 EGU General Assembly (2010, 2011, and 2012; http://acc.igs.org/studies.html)
provided additional motivation. Those presentations showed a rotational misalignment
between the IGS orbits and the IGA/IGR orbits, especially in RX and RY. Unexpectedly,
the IGR and IGA were more consistent with one another and more accurate than the IGS.
A few ideas were proposed to explain the results, including the possibility that procedural
issues exist in the Final orbit combination.
At the AC level, the Ultra–rapid and Rapid procedures transfer the terrestrial frame to theorbits by tightly constraining the a priori positions of the IGb08 reference frame stations.
The Finals AC procedures use a no–net rotation (or other removable) constraint, satisfied
over the IGb08 core network. At the combination level, prior to August 19, 2012 (GPSWk 1702, Day 0), the main procedural difference between the Final orbits and the Ultrarapid and Rapid orbits is that AC SINEX and AC ERP X– and Y–rotations were applied

26

2 Events Impacting Product Quality and Reliability

Figure 3: AC rotational offsets from the IGS Final orbit.

Figure 4: WRMS of AC orbit residuals w.r.t. IGS Finals.

27

Griffiths and Choi: Analysis Center Coordinator
for the Final orbits. This study reviewed the Final orbit combination model and found
two issues: the signs used for the AC SINEX X– and Y–rotations were incorrect and the
AC ERP rotations were no longer necessary since the switch to daily TRFs. More details
are available in a report at http://acc.igs.org/orbits/acc_report_final_rotations.
pdf.
Correcting the two issues found in this study had a significant impact on the quality of
the IGS Final orbits. Although the scatter was not impacted (Fig. 4), the changes in
the rotational offsets of the AC orbits are much clearer (e.g., see Y–rotations in Fig. 5).
In addition, the ACC Final PPP results indicate that the Final orbits are now much
more consistently aligned with the IGS frame (IGb08) than before (Fig. 6), reducing therotational offset by up to 20 µas in RX and RY.
Starting with GPS Wk 1702, Fig. 5 shows that there is a high level of inter–AC agreement,with ESA and GFZ being possible exceptions. However, what is starkly clear from Fig. 5
is that the orientation of the ESA orbits is quite different from the other ACs. Since ESA
dominates the combination, the orientation of the Final orbits disagrees with the otherACs and the IGRs by nearly equivalent amounts. ESA is currently investigating the causeof their rotational offsets relative to the other ACs. However, it is critical to note thatthese features could not be seen before the switch to daily TRFs and when the SINEX
rotation problems existed in the Final orbit combination. This fact is illustrated in Figure
6 with the improved average RX and RY offsets starting at Wk 1702 . Figures 5 and 6
highlight advantages of 1) improved inter-AC agreement with the switch to daily TRFs
and 2) correct pre–alignment of AC orbits in the Final orbit combination.

2.6 Preparations for IGS 2nd Reprocessing (IG2)
Preparations for the next reprocessing are underway. The past year was spent establishing a set of minimum analysis standards (see items in black at http://acc.igs.org/
reprocess2.html), which was finalized at the IGS Workshop in Olsztyn, Poland. Since
then, the ACs have worked to implement these minimum standards. Thus far, ACs havegenerally implemented nearly all of the minimum standards. Though a few still need toadopt models for 2nd –order ionosphere effects, Earth radiation (visible and infrared) andsatellite thrusting due to signal transmission along the antenna bore site.
In addition to the minimum analysis standards, other models are proposed and can be
adopted as each AC chooses. These are printed in red at the IG2 website. The following
preliminary schedule for IG2 was discussed at the AC splinter meeting in San Francisco,
CA on December 4, with an aim to submit IGS SINEX products to the IERS in early 2014
for the next ITRF:

28

2 Events Impacting Product Quality and Reliability

Figure 5: AC orbit Y-rotation offsets w.r.t. IGS Finals.

Figure 6: X, Y and Z Helmert rotations between PPP results using the IGS products and IGb08(see more at http://acc.igs.org/index_igsacc_ppp.html).

29

Griffiths and Choi: Analysis Center Coordinator
Time period (2013)
January thru May
June thru August
September thru November

Objective
Implement remaining minimum analysis standards
Initial processing of 1994.0 thru 2013.3 and possibly submit
to IGS for test combinations
ACs finalize their submissions and submit to IGS

3 User Interest in IGS Products
A recent analysis of the statistics for IGS product downloads at NASA’s Crustal Dynamics
Data Information System (CDDIS) indicates that the IGS Ultra–rapid GPS orbits and
ERPs are more than twice as popular as the next most downloaded product, the IGS Final
GPS products (Tab. 2).

Table 2: IGS product download rates from NASA GSFC/CDDIS (statistics courtesy of Carey
Noll). The statistics include the IGS core products, along with those from the 1st
reprocessing (IG1), the GLONASS Final orbits (IGL) and an experimental mixed GPSplus GLONASS Ultra-rapid products (IGV).

Product

GNSS

Total Hits

SP3
(%)

ERP CLK SNX(%) (%) (%)

SUM
(%)

IGU/IGA

GPS

93.7

3.1

n/a

n/a

3.2

IGS+IG1
IGR
IGL
IGV

GPS
GPS
GLO
GPS & GLO

11,711,506(≈ 4 × 2, 927, 877 daily)
1,359,656
887,986
225,515
223,562

60.7
65.6
99.1
95.0

6.8
8.7
n/a
n/a

24.8
16.9
0.3
n/a

5.8
n/a
n/a
n/a

2.0
6.4
0.6
5.0

30

4 Publications and Meeting Presentations

4 Publications and Meeting Presentations
The following sub–sections highlight a selection of papers and presentations from 2012that are relevant to the quality of the IGS products (see full list at http://acc.igs.org/
studies.html).

4.1 Antenna Calibrations• Impact of different individual GNSS receiver antenna calibration models on geodetic
positioning (2012)
by Q. Baire, E. Pottiaux, C. Bruyninx, P. Defraigne, W. Aerts, J. Legrand, N. Bergeot,
and J. M. Chevalier, poster presentation at the European Geosciences Union 2012
General Assembly• Extension of the GPS satellite antenna patterns to nadir angles beyond 14◦ (2012)by A. Jäggi, F. Dilssner, R. Schmid, R. Dach, T. Springer, H. Bock, P. Steigenberger,
Y. Andres, and W. Enderle, poster presentation at the European Geosciences Union2012 General Assembly• GNSS Absolute Antenna Calibration at the National Geodetic Survey (2012)by G. Mader, and A. Bilich, poster presentation at the European Geosciences Union2012 General Assembly• Impact of individual GNSS antenna calibration used in the EPN on positioning(2012)
by Q. Baire, E. Pottiaux, C. Bruyninx, P. Defraigne, W. Aerts, J. Legrand, N. Bergeot,
and J. M. Chevalier, presentation at the EUREF 2012 Reference Frame Sub-commission
for Europe Symposium, Paris, 6–8 June 2012
• GNSS antenna offset field test in Metsähovi (2012)by U. Kallio, H. Koivula, S. Nyberg, P. Häkli, P. Rouhiainen, and V. Saaranen,
presentation at the EUREF 2012 Reference Frame Sub-commission for Europe Symposium, Paris, 6–8 June 2012
• Differences between GPS receiver antenna calibration models and influence on geodetic positioning (2012)
by Q. Baire, W. Aerts, C. Bruyninx, E. Pottiaux, and J. Legrand, presentation at
the Fall 2012 American Geophysical Union Meeting• Towards better GNSS observations at the new IGS reference station BRUX (2012)
by W. Aerts, Q. Baire, C. Bruyninx, J. Legrand, and E. Pottiaux, invited presentation at the Fall 2012 American Geophysical Union Meeting31

Griffiths and Choi: Analysis Center Coordinator

4.2 Earth Rotation Parameters• High–accuracy subdaily ERPs from the IGS (2012)
by J. Ray and J. Griffiths, presentation at the European Geosciences Union 2012
General Assembly• High–frequency signals of oceans and atmosphere in Earth rotation (2012)by S. Böhm, presentation at the European Geosciences Union 2012 General Assembly

4.3 Ionosphere Modeling and Products• Intercomparison of approaches for modeling second order ionospheric corrections
using GNSS measurements (2012)by M. Garcia–Fernandez, M. Butala, A. Komjathy, and S. Desai, poster presentation
at the Fall 2012 American Geophysical Union Meeting

4.4 Orbit Modeling and Products• IGS preparations for the next reprocessing and ITRF (2012)
by J. Griffiths, P. Rebischung, B. Garayt, and J. Ray, presentation at the European
Geosciences Union 2012 General Assembly• Modeling of the GIOVE-B clock as a tool for studying radiation pressure models(2012)
by U. Hugentobler, O. Montenbruck, C. Rodriguez–Solano, and P. Steigenberger,
poster presentation at the European Geosciences Union 2012 General Assembly• Multi–technique combination at observation level with NAPEOS (2012)by M. Otten, C. Flohrer, T. Springer, and W. Enderle, presentation at the European
Geosciences Union 2012 General Assembly• Non–conservative GNSS satellite modeling: long-term behavior (2012)
by C. Rodriguez–Solano, U. Hugentobler, P. Steigenberger, K. Sosnica, and M. Fritsche,poster presentation at the European Geosciences Union 2012 General Assembly• Characterizing GPS Block IIA shadow and post-shadow maneuvers (2012)
by J. Weiss, Y. Bar–Sever, W. Bertiger, S. Desai, N. Harvey, and A. Sibthorpe,poster presentation at the European Geosciences Union 2012 General Assembly• Rotational errors in IGS orbit & ERP products (2012)
by J. Ray, J. Griffiths, P. Rebischung, J. Kouba, and W. Chen, presentation in orbit
modeling plenary session at IGS 2012 Workshop, Olsztyn, Poland

32

References• Do annual geopotential variations affect IGS products? (2012)
by J. Ray, S. Bettadpur, J. Ries, T.–S. Bae, X. Collilieux, T. van Dam, K. Choi,
and J. Griffiths, presentation for the AC/RF/CP WG Splinter Meeting at the IGS
2012 Workshop, Olsztyn, Poland• IGS classic products, status and towards the future (2012)
by J. Griffiths and K. Choi, presentation in opening plenary session at IGS 2012
Workshop, Olsztyn, Poland• The impact of temporal geopotential variations on the GPS constellation (2012)by S. Melachroinos, F. Lemoine, J. Nicholas, N. Zelensky, D. Chinn, O. Bordyugov,
B. Beckley, and S. Luthcke, poster presentation at the Fall 2012 American Geophysical Meeting• Space tie and local tie for combined GNSS-SLR analysis (2012)by D. Thaller, K. Sosnica, R. Dach, and A. Jäggi, poster presentation at the Fall2012 American Geophysical Meeting• Sub–daily Alias and Draconitic Errors in IGS Orbits (2012)
by J. Griffiths and J. Ray, GPS Solutions, doi: 10.1007/s10291-012-0289-1

5 Events in 2013
• Maintain existing products, as usual.

• Perform comprehensive analyses to establish IGS/IGR/IGU errors since the switch
to daily TRFs and corrections to the IGS Final orbit combination.
• Coordinate second reprocessing campaign, along with performing combinations of
the repro2 orbits and clocks. The project is expected to deliver combined SINEX
files to the IERS by early 2014. This will require coordinated processing and deliveryof AC products to Data Centers and test combinations.
• Investigate possibility of GLONASS clock combinations using s/w and results fromBias Working Group.

References
Beutler, G., J. Kouba, and T. Springer. Combining the orbits of the IGS processing
centers. In IGS Workshop Proceedings: 1993 IGS Analysis Center Workshop, J. Kouba(ed.), Ottawa, Canada, pp. 20–58, 1993.
Ferland, R., J. Kouba, and D. Hutchison. Analysis methodology & recent results of the
IGS network combination. Earth Planets Space, 52:953–957, 2000.

33

Griffiths and Choi: Analysis Center Coordinator
Kouba, J. and Y. Mireault. Analysis Coordinator Report. International GPS Service for
Geodynamics (IGS) 1996 Annual Report, pp. 55–100, 1997.
Kouba, J., J. Ray, and M. M. Watkins. IGS Reference Frame Realization, Earth Planets Space. In IGS Workshop Proceedings: 1998 Analysis Center Workshop, J. M. Dow,
J. Kouba, and T. Springer (eds.), European Space Operations Centre, Darmstadt, Germany, pp. 137–171, 1998.

34

Center for Orbit Determination in Europe (CODE)
R. Dach1 , S. Schaer2
S. Lutz1 , M. Meindl1 , H. Bock1 , E. Orliac1 , L. Prange1 ,D. Thaller1 , L. Mervarta , A. Jäggi1 , G. Beutler1
E. Brockmann2 , D. Ineichen2 , A. Wiget2
G. Weber3 , 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, and• Institut für Astronomische und Physikalische Geodäsie, Technische Universität
München (IAPG, TUM), Munich, Germany.
The operational computations are performed at AIUB whereas reprocessing activities areusually carried out at IAPG, TUM. All solutions and products are produced with thelatest development version of the Bernese GNSS Software (Dach et al., 2007).
aInstitute of Geodesy, Czech Technical University in Prague, Czech Republic

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

2 CODE products available to the public
A wide variety of GNSS solutions based on a rigorous combined GPS/GLONASS dataprocessing scheme is computed at CODE. The products are made available through anonymous ftp:
ftp://ftp.unibe.ch/aiub/CODE/ or http://www.aiub.unibe.ch/download/CODE/
An overview of the files is given in Tab. 1.
Table 1: CODE products available through anonymous ftp.
CODE ultra–rapid products available at ftp://ftp.unibe.ch/aiub/CODE
COD.EPH_U
COD.ERP_U
COD.TRO_U
COD.SUM_U
COD.ION_U
COD.EPH_5D

CODE ultra–rapid orbits, updated every 6 hours
CODE ultra–rapid ERPs belonging to the ultra–rapid orbit product
CODE ultra–rapid troposphere product, troposphere SINEX format
Summary of stations used for the latest ultra–rapid orbit
Last update of CODE rapid ionosphere product (1 day) complemented with
ionosphere predictions (2 days)
Last update of CODE 5–day orbit predictions, from rapid analysis, including all
active GLONASS satellites

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

36

CODE rapid orbits
CODE 24–hour orbit predictions
CODE 48–hour orbit predictions
CODE 5–day orbit predictions
CODE rapid ERPs belonging to the rapid orbits
CODE predicted ERPs belonging to the predicted 24–hour orbits
CODE predicted ERPs belonging to the predicted 48–hour orbits
CODE predicted ERPs belonging to the predicted 5–day orbits
CODE rapid clock product, clock RINEX format
CODE rapid troposphere product, troposphere SINEX format
CODE rapid solution, SINEX format
CODE rapid ionosphere product, IONEX format
CODE 1–day or 2–day ionosphere predictions, IONEX format
CODE rapid ionosphere product, Bernese format
CODE 1–day ionosphere predictions, Bernese format
CODE 2–day ionosphere predictions, Bernese format
Improved Klobuchar–style coefficients, RINEX format
1–day predictions of improved Klobuchar–style coefficients
2–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

2 CODE products available to the public
Table 1: CODE products available through anonymous ftp (cont.).
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

CODE final GNSS orbits, CODE’s official IGS orbit product
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, but
5 minutes for all remaining station clock corrections
CODE final clock product, clock RINEX format, with a sampling of
5 sec for the satellite and reference (station) clock corrections, but
5 minutes for all remaining station clock corrections
CODE daily SINEX product
CODE final troposphere product, troposphere SINEX format
CODE final ionosphere product, IONEX format
CODE final ionosphere product, Bernese format
CODE weekly SINEX product
CODE weekly summary files
CODE ERPs from a weekly solution
CODE precise GLONASS orbits (for GPS weeks 0990 to 1066)
CODE weekly summary files of GLONASS analysis
Navigation messages containing improved Klobuchar–style ionospherecoefficients
CODE monthly P1−C1 DCB solutions, Bernese format,
containing only the GPS satellites
CODE monthly P1−P2 DCB solutions, Bernese format,
containing all GPS and GLONASS satellites
CODE monthly P1−P2 DCB solutions, Bernese format,
containing all GPS and GLONASS satellites and all stations used

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.

With GPS week 1706
CODE started to generate a pure one–day solution (label “COF”) in
addition to the usual
three–day long–arc solution (label “COD”). A
detailed description is
given in Sect. 3.2 of thisreport. The result files
GNSS
from both series are subGPS only
mitted to the IGS data
centers hosting the prod- Figure 1: Network used for the GNSS final processing at CODE by
the end of 2012.
ucts. The files are listed
in Tab. 2.
The network used by CODE for the final processing is shown in Fig. 1. About 70% of thestations support GLONASS (red stars).
37

Dach, Schaer et al.: Center for Orbit Determination in Europe
Table 2: CODE final products available in the product directories of the IGS data centers.
Files generated from three–day long–arc solutions:
CODwwwwd.EPH.Z
CODwwwwd.ERP.Z
CODwwwwn.SNX.Z
CODwwwwd.CLK.Z
CODwwwwd.CLK_05S.Z
CODwwwwd.TRO.Z
CODwwww7.ERP.Z
CODwwww7.SUM
CODwwww7.SNX.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 ERP (pole, UT1−UTC) solution belonging to the COD–orbit files in
IGS IERS ERP format
GNSS daily coordinate/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
GNSS weekly station coordinates, SATAs, GCCs, and daily sets of ERPs in
SINEX format stacked from the seven long–arc solutions of the week

Files generated from pure one–day solutions:
COFwwwwd.EPH.Z
COFwwwwd.ERP.Z
COFwwwwd.SNX.Z
COFwwwwd.CLK.Z
COFwwwwd.CLK_05S.Z
COFwwwwd.TRO.Z
COFwwww7.ERP.Z
COFwwww7.SUM
COFwwww7.SNX.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 ERP (pole, UT1−UTC) solution belonging to the COF–orbit files in
IGS IERS ERP format
GNSS daily coordinate/ERP/GCC from the pure one–day solution in SINEX
formatGPS 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
GNSS weekly station coordinates, SATAs, GCCs, and daily sets of ERPs in
SINEX format stacked from the seven pure one–day solutions of the week

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

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. (2012).
In Sect. 3.1 we give an overview of important development steps in the year 2012. Section 3.2 provides details on the biggest change in the processing scheme and modelling,which results in the parallel submission of the traditional three–day long–arc and a new
pure one–day solution series.
38

3 Changes in the daily processing for the IGS
Table 3: Selected modifications of the CODE processing, in 2012.
Date

DoY/Year

Description

14-Feb-2012
14-Feb-2012
29-Mar-2012

045/2012
045/2012

23-Apr-2012
22-Jun-2012

114/2012
174/2012

Reduce baseline lengths for ambiguity resolution in rapid processing
Several problems concerning GPS quarter–cycle bias handling solved
GPS quarter–cycle bias handling changed:
No ambiguity resolution at all for satellites with (potential)
quarter–cycle problems
Maximum 300 (instead of 250) stations allowed for final processing
SINEX daily solution from rapid processing stored without
regularization
Serious leap second problem in the software
ultra–rapid 18:00 submission of day 186 is OK again.
Daily SINEX files based on one–day and three–day orbital arcs
started for parallel test processing
Transform ERP to offset and drift in SINEX files (NEQ
representation)
FES2004 ocean tidal loading coefficients updated(small changes with respect to the prev. file)
Troposphere gradient values in Troposphere SINEXAll NEQs are normalized at the diagonal for inversion
List of model changes for all product lines:• Troposphere gradient model from TANZ to Chen and Herring(1997)• IERS 2010 conventions (Petit and Luzum, 2010) including, e.g.,
new potential models for orbit integration:
Earth: from JGM3. to EGM2008; Ocean tides: from OT_CSR30
to OT_FES2004
Update of the subdaily pole and nutation model
List of model changes for final product line:• Vienna non–tidal atm. pressure loading (Wijaya et al., 2011) withscaling factors (forced to zero for IGS product generation)• CODE weekly solution only for solution verification• CODE traditional three–day solution bases on three–day
coordinate set instead of weekly coordinates after an automatedverification of the fiducial sites• Start a new pure one–day solution series in parallel with the label
COF for orbits, ERP, SINEX, and clocks with a fully automatedverification of the datum stations• GLONASS–GPS translation parameters are deleted from thenormal equations for IGS product generation• Delete parameters for long–term monitoring instead of constrain
them during the product generation• Numerous consistency tests for all product generation steps

01..04-Jul-2012
10-Jun-2012

162/2012

02-Aug-2012
05-Aug-2012
19-Aug-2012
16-Sep-2012

218/2012
232/2012
260/2012

16-Sep-2012
16-Sep-2012

260/2012
260/2012

07-Oct-2012
07-Oct-2012
11-Nov-2012

281/2012
281/2012
316/2012

Magnetic pole table updated using GMPOLE program (1980–2015)
ANTEX model update from IGS08_1700 to IGS08_1706 withchanged Z–offset values for a subset of satellites
Use IGb08 instead of IGS08 for geodetic datum definition
Minor change in ambiguity resolution
Bugfix for computation of formal error of pole rates and LOD(all ERP files contained wrong formal errors)

39

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

3.1 Overview of changes in the processing scheme in 2012
Table 3 gives an overview of the major changes implemented during the year 2012. Details
on the analysis strategy can be found in the IGS analysis questionnaire at the IGS Central
Bureau (ftp://igscb.jpl.nasa.gov/igscb/center/analysis/code.acn).
Several other improvements not listed in Tab. 3 were implemented, too. Those mainly
concern data download and management, sophistication of CODE’s analysis strategy,
software changes (improvements), and many more. As these changes are virtually not
relevant for users of CODE products, they will not be described in detail.

3.2 Details on selected model changes
Test solutions for weeks 1692 to 1705
The biggest update of the IGS processing scheme at CODE was initiated by the transition
from weekly to daily coordinates for the IGS final product series, which is motivated by
the opportunity to correct for non–tidal atmospheric pressure loading at post–processing
level. This deep change in the IGS product generation was prepared by a ten–week parallel
test campaign.
Two solution series have been generated by CODE for this test campaign:• A pure one–day solution where the datum definition was based on the verified set ofdatum stations from the weekly solution.
• A three–day long–arc solution where the coordinate, troposphere, Earth rotation,and geocenter coordinate parameters for the first and third day have been pre–eliminated before connecting them with the parameters for the middle day. The
datum definition was also based on the verified set of datum stations from theweekly solution.
In both cases the GNSS–translation parameters have been introduced from the weekly
solution. The traditional solution as it has been computed by CODE since years basedon three–day long–arcs for the orbits and the weekly coordinates (daily estimates for
the Earth rotation parameters also from the weekly solution) is the third solution forcomparisons. The main question for this test period was how the shorter (and therefore
noisier) coordinate estimates may degrade the orbit quality.
From the numerous comparisons done at CODE at that time the differences in the station
coordinates are provided in Fig. 2 and the differences in the GNSS satellite orbits in Fig. 3.
The main conclusions from this comparison are in short:40

3 Changes in the daily processing for the IGS
Coord: one week Orbit: three days
Coord: one week Orbit: three days
Coord: one day Orbit: three days

compared withcompared withcompared with

Coord: one day
Coord: one day
Coord: one day

Orbit: three days
Orbit: one day
Orbit: one day

Coord: one week Orbit: three days
Coord: one week Orbit: three days
Coord: one day Orbit: three days

Coord: one day
Coord: one day
Coord: one day

Orbit: three days
Orbit: one day
Orbit: one day

4RMS(∆coord) in mm

RMS(∆coord) in mm

4compared withcompared withcompared with

3

2

1

0

3

2

1

0
168

175

182

189

196

203

210

217

224

231

238

245

252

259

Day of year 2012

168

175

182

189

196

203

210

217

224

231

238

245

252

259

Day of year 2012(a) RMS of direct differences(b) RMS after a seven–parameter transformation

Figure 2: Coordinate comparison of the two test solutions and the traditional CODE solution.
Day of year 2012
168

175

182

189

196

203

210

217

224

Day of year 2012
231

238

245

252

259

175

182

189

196

203

210

217

224

231

238

245

252

259

168

175

182

189

196

203

210

217

224

231

238

245

252

259

4
8
12

GPS

8
12
16
20

16
20

24

24

28

28

32

32

4

4

GLONASSGLONASS

GPS

4

168

8
12
16
20

24
GPS
GLONASS
total

8
12
16
20

24
GPS
GLONASS
total
168

175

182

189

196

203

210

217

224

231

238

245

252

259

Day of year 2012
0

10

20

30

Orbit difference in mm

Day of year 201240(a) Three–day long–arc orbits with one–day coordinates wrt. pure one–day solution for orbits andcoordinates

0

10

20

30

40

Orbit difference in mm(b) Three–day long–arc orbits with one–day coordinates wrt. three–day long–arc orbits with weekly
coordinates

Figure 3: RMS from the orbit differences over the three coordinate components.

• The RMS between the one–day and the weekly coordinates are mainly dominated bystations where the repeatability is also higher when the weekly coordinate solutions
are generated. The datum definition is consistent for all solutions.
• In the pure one–day solution the differences of the orbits of individual satellites may
become huge with respect to three–day long–arc solutions especially for satellites
that are only marginally observed (unhealthy) or due to observation scenarios during
repositioning events of GPS satellites. In general the differences for GLONASS
satellites are bigger than for GPS satellites.
41

Dach, Schaer et al.: Center for Orbit Determination in Europe• The solution with a three–day long–arc orbit but one–day coordinate estimates keeps
the benefit from CODE’s traditional three–day long–arc orbit but is also equivalent
to a pure one–day solution regarding the station coordinates.
Having these figures and conclusions in mind CODE proposed the three–day long–arc orbit
solution with coordinates reduced to the middle day by pre–elimination to the analysis
center coordinator as the new contribution to the IGS final products.

New set of solutions since week 1706
There are several pros and cons for solutions with long–arc orbits and pure one–day solutions. The analysis center coordinator did not accept the multi–day solution as proposed
by CODE. Finally it has been agreed• to start a new product series from CODE as a pure one–day solution with the label
COF that is used for the reference frame generation and as contribution to the GPS
final orbits and• to continue the series of the three–day long–arc solution from CODE with the label
COD that is used as contribution to the GLONASS orbit product from the IGS.
The first of the two solutions should be more consistent with the contributions of the otheranalysis centers supposed that also all other groups do not apply any continuity condition
to their parameters at the day boundaries. The second solution offers by constructionsmoother orbit products over the day boundaries and better orbits for all GLONASS andmarginally observed GPS satellites.
ORBIT REPEATABILITY (GPS)
160

COF
COD

COF
COD

60
DAYS*SATELLITES140
DAYS*SATELLITESORBIT REPEATABILITY (GLONASS)
70

120
100
80
60
40

50
40
30
20
10

20
0

0
0

10

20

30

40

50

60

70

REPEATABILITY [mm](a) GPS80

90 100+

0

10

20

30

40

50

60

70

80

90 100+REPEATABILITY [mm](b) GLONASS

Figure 4: Histogram for the RMS of a three–day orbit fit during 30 days using the COF pureone–day (red bars) and the COD three–day long–arc solution (green bars).

42

3 Changes in the daily processing for the IGS
This is illustrated in Fig. 4 where the RMS of an orbit fit over three consecutive days of
the COD and COF solutions for all 56 satellites during 30 days (day 252 of year 2012 to
day 016 of year 2013) is plotted in a histogram. Due to the continuous arc over three days
the RMS for the COD solution is in general smaller than for the COF solution. Extreme
outliers on the level of several decimeters and even up to one meter do only appear in the
one–day COF solution for individual satellites that are observed only by a very limited
number of stations or during a repositioning event close to midnight. The RMS limit of
2.0 cm is exceeded in 8.2% for the COF pure one–day and in 5.0% for the COD three–day
long–arc solution for the GPS satellites. Assuming a limit of 3.5 cm for GLONASS orbit
fits there are 7.8% above for the COF pure one–day and only 3.5% for the COD three–day
long–arc solution series.

Optimized product generation since GPS week 1706
After pre–processing of the observation files of one day the final normal equation containing
all parameters is set up. In the final procedure of CODE typically about 1,600,000 observations from approx. 260 stations and 56 (sometimes only 55) satellites are processed toderive approximately 24,000 parameters where about half of them are remaining ambiguity
parameters that are immediately pre–eliminated.
A reasonable amount of the remaining parameters are so–called monitoring parametersthat are not solved in the daily GNSS solutions but they shall be included in the normal
equations for an evaluation in long–term solutions. These parameters have traditionallybeen heavily constrained when computing the solution for the day.

APL
8.86%
HOI: 0.03%

CRD
8.86%

TRA
7.54%

SAP
10.06%
SAO: 1.89%
STC: 1.89%
ORB
9.43%

TRP
50.02%

space List of parameters in the internal
space one−day normal equation from CODE
CRD: Station coordinates
TRP: Site−specific troposphere parameters
ERP: Earth rotation parameters
GCC: Geocenter coordinates
ORB: Orbital elements
STC: Stochastic orbit parameters
SAO: Satellite antenna offset parameters
SAP: Satellite antenna patterns
HOI: Higher−order iono scaling parameters
TRA: GNSS−translation parameters
APL: Scaling factors for Vienna APL model
0 Total number of parameters

space
space
789
4457
125
3
840
168
168
896
3
672
789
8910

GCC: 0.03%
ERP: 1.40%

Figure 5: Number of parameters of different types in a typical final one–day solution from CODE(in this example from day 350 of year 2012), where the shaded parameters are only introduced for long–term studies. Note, the ERPs are available with an hourly resolution
in a piece–wise linear representation.

43

Dach, Schaer et al.: Center for Orbit Determination in Europe
The new generation scheme of the daily solution is a multiple–step procedure:
1. All parameters are set up in one single normal equation file that is only stored but
not inverted.
2. From a copy of the fully blown normal equation all monitoring parameters are deleted(removal of the columns and rows related to the parameter in the normal equation).
3. Adapt the resolution in time (e.g., for Earth rotation parameters) and if needed pre–eliminate further parameters (e.g., troposphere parameters) in the reduced normal
equation applying a parameter transformation.
4. Inversion of the reduced normal equation to obtain the result files for the daily
solution.
Figure 5 shows the number of parameters in a typical one–day final solution from CODE
where it becomes clear that more than a quarter of the parameters are only introduced
for long–term studies. The removal of those parameters in step 2 of the new processing
scheme saves a significant amount of computing time.
The disadvantage from this approach is, that the procedure with the parameter removal
needs to be repeated several times to include, e.g., satellite antenna offsets in the resulting
SINEX–file. For that reason several implementations of these procedures were neededin parallel. To guarantee the consistency the resulting coordinates are requested to be
identical at the 0.01 millimeter level.
Nevertheless, this change of the algorithm leads to a significant reduction of the processing
time even if more parameters (“Scaling factors for Vienna APL model”) are computed andthe datum definition is verified for each individual solution (which means the normal
equation is solved twice, once including all fiducial sites for verification and once onlywith the accepted datum stations for the final solution). In addition, after the removal of
the parameters they do no longer have any influence on the solution which was not thecase before applying the heavy contraints with the pre-elimination.
Analogue procedures are introduced for the generation of the three–day solutions.

4 CODE contribution to the IGS–MGEX campaign
In 2012 the IGS started its “Multi–GNSS EXperiment” (MGEX). An increasing number of new or upgraded tracking stations (about 50 in late 2012) contributes to thisproject. These stations comply with the IGS standards (e.g., correct equipment information, RINEX data format) and support the RINEX 3 data format version, new signal
types for the established GNSS (e.g., L5 for GPS), and new GNSS, such as Galileo, BeiDou, and QZSS. These data are freely available and are well suited to prepare for future
developments in GNSS processing.

44

70

GIOVE-A
GIOVE-BIOV E11IOV E12RMS of 3-day orbit fit [cm]Orbit difference at day boundary [cm]References

60
50
40
30
20
10
0
140

160

180

200
220
DOY 2012

240260(a) Position differences at the day boundaries fromconsecutive orbit solutions

GIOVE-A
GIOVE-BIOV E11IOV E12
25
20
15
10
5
0
140

160

180

200
220
DOY 2012

240260(b) Three–day long–arc fit of the orbits from consecutive days

Figure 6: Quality assessment of the Galileo orbits from the CODE triple–system solution for
IGS–MGEX.

CODE contributes to MGEX by providing a triple–system orbit solution including GPS +GLONASS + Galileo on a non–operational basis. The processing procedure has been
derived from the CODE rapid processing chain: All Galileo tracking stations are added tothe usual GPS+GLONASS rapid process in a separate cluster and a combination is doneon normal equation level by stacking all common parameters.
In January 2013 the CODE MGEX products of the GPS–weeks 1690 to 1720 (days 150
to 364 of year 2012) are available at ftp://cddis.gsfc.nasa.gov/gnss/products/mgex
using the solution ID “com” for the CODE–MGEX solution. Further updates and an
extension of the product for Galileo clock corrections are in preparation.
The plots in Fig. 6 may give an impression of the current status of the Galileo orbit quality
in the CODE solution. An independent validation based on SLR–measurements over all
weeks showed an RMS of the residuals of about 8 cm for each of the two Galileo IOVsatellites (E11 and E12).

References
Chen and Herring. Effects of atmospheric azimuthal asymmetry on the analysis of space
geodetic data. Journal of Geophysical Research, 102(B9):20489–20502, 1997. doi: 10.
1029/97JB01739 .
Dach, R., G. Beutler, H. Bock, P. Fridez, A. Gäde, U. Hugentobler, A. Jäggi, M. Meindl,
L. Mervart, L. Prange, S. Schaer, T. Springer, C. Urschl, and P. Walser. Bernese GPS
Software Version 5.0. Astronomical Institute, University of Bern, Bern, Switzerland,jan 2007. URL http://www.bernese.unibe.ch/docs50/DOCU50.pdf. User manual.

45

Dach, Schaer et al.: Center for Orbit Determination in Europe
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 2011. In M. Meindl, R. Dach, and Y. Jean, editors, IGS 2011 Technical
Reports, IGS Central Bureau, pages 29–40, 2012.
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.
Wijaya, D.D., J. Böhm, H. Spicakova, M. Schindelegger, M. Karbon, D. Salstein, and
H. Schuh. Determination of atmospheric pressure loading corrections based on a newconcept of reference pressure. Journal of Geodesy, 2011. to be submitted.
All publications, posters, and presentations of the Satellite Geodesy research group at
AIUB are available at http://www.bernese.unibe.ch/publist .

46

NRCan Analysis Center Report for 2012
Y. Mireault, B. Donahue, R. Ghoddousi–Fard,
P. Tétreault, F. Lahaye
Natural Resources Canada, Geodetic Survey Division
615, Booth Street, Ottawa, ON, Canada K1A 0E9
Yves.Mireault@nrcan.gc.ca

1 Introduction
In 2012, the Geodetic Survey Division of the Natural Resources Canada (NRCan–GSD)
continued its contribution to the International GNSS Service. NRCan–GSD is also responsible for the maintenance of the National horizontal, vertical and gravitational reference
frames as well as providing the means of accessing these data in Canada. This reportaddresses the major product changes and events that occurred within NRCan during theyear 2012.

2 Review of 2012
Readers are referred to the Analysis Coordinator web site (http://acc.igs.org) for historical combination statistics of the NRCan–AC products.

2.1 Ultra–Rapid, Rapid and Final Products
There were no major changes made to NRCan–AC Ultra–Rapid and Rapid core products in2012. However, a few changes to the Final GPS processing strategy are worth mentioning.
To be consistent with the upcoming "Repro 2" campaign, the Final GPS orbit strategy
was updated. Major changes included:• Software upgrade to JPL’s GIPSY–OASIS v6.1.2;• Start processing independent days and use of IGR orbits and Bulletin A as a priori values (previous strategy used extrapolated NRCan’s ERPs and previous day
NRCan’s orbits);• Earth Albedo model turned on;• Switch from a 7–day to a 1–day TRF submissions (SINEX).
47

Mireault et al.: Natural Resources Canada
Table 1: NRCan–AC processing Events and Changes in 2012

CalendarDateGPS
Wk (day)

2012-Feb-15

1675 (3)2012-Apr-18

1684 (3)2012-Jul-01

1695 (0)2012-Jul-01

1695 (0)2012-Aug-19

1702 (0)2012-Oct-07

1709 (0)Products

Events / Changes

Ultra–Rapid,
Rapid, Final
Ultra–Rapid,
Rapid, Final
Ultra–Rapid,
Rapid, Final
GPS Final

CC2nonCC (version 6.4).

Ultra–Rapid,
Rapid, Final
Ultra–Rapid,
Rapid, Final

Switch from 7day to 1day TRF
submissions (SINEX).
IGb08 reference frame and antenna
calibration (from IGS08).

CC2nonCC (version 6.5).
Leap Second.
• JPL’s GIPSY–OASIS v6.1.2• Processing independent days and using
IGR orbits and bulletin A as a priori
values;• Earth Albedo model

Routine processing, product generation and software maintenance were shared among GSD
staff. More information about the strategies used and the various products generated canbe found in (Meindl at al., 2012). Also, Tab. 1 above gives a short summary of importantchanges and events in 2012.
Time was devoted to the final development and testing of a new Ultra–Rapid GNSS orbit
solution. This product should be available on an hourly basis sometime in 2013. At thesame time, we started developing an Ultra–Rapid GNSS clock solution. Testing will most
likely start in early 2013. Hopefully, this new product will be available by the end of 2013.
Finally, NRCan is currently preparing for the "Repro 2" campaign.

2.2 Real–Time Products
There were no major changes made to the real–time RTCM–SSR format correction feed
delivered to the Real–Time Pilot project for comparison and combination, other thanswitching to the agreed upon 5 second interval and small improvements to the message
encoding algorithm.

48

References

3 Precise Point Positioning (PPP)
Recent modeling improvements in the NRCan–PPP software include:• Autonomous second and third order ionosphere correction; the autonomy comes fromthe estimation of the station Differential Code Bias (DCB) (P1−P2) to correct theslant delays necessary for the computation of the high–order corrections; Vertical
Total Electron Content (TEC) is also estimated as a random walk;• Pole tide modeling using input x and y pole offsets (e.g. from IGS Final)• Input and use of C2 pseudoranges corrected for P2−C2 biases

One use of NRCan–PPP is CSRS–PPP, the online GNSS service offered by NRCan. Although CSRS–PPP is aimed primarily at Canadian users to provide improved positions in
Canada’s national reference frame NAD83 (CSRS), it can also be used, and in fact, is usedworldwide for improved ITRF positioning in either static or kinematic mode. The online
positioning service is based on the PPP processing methodology and the use of precise
GPS orbits and clocks estimates. In addition to NRCan’s rapid and hourly GPS orbits
and clocks, IGS Final GPS orbits and 30 second clocks are used for data observed after
December 16, 2007 and IGS "Repro 1" products are used for any data observed between
January 2, 1994 and December 15, 2007. Since August 14, 2011 CSRS–PPP also processes
GLONASS data using NRCan’s GLONASS orbits and 30 second clocks.

4 Ionosphere and Satellite DCB Monitoring
Near–real–time global ionosphere maps continue to be generated internally every 15 minutes in the form of spherical harmonic coefficients with degree and order 15 . Performanceis monitored and improvements are made when required. Recently, the number of stations
used increased to about 145 (RT–IGS stations and Canadian RT stations). Daily global
IONEX maps generation using all IGS stations is planned.
Statistics of phase rate variation for all RT–IGS stations are being computed in near–real–time as a proxy for phase scintillation studies.
GPS P1−P2, P1−C1 and P2−C2 DCBs continue to be estimated daily and smoothed as
weekly moving averages. Since January 1, 2013, receiver specific P1−C1 GPS DCBs arebeing generated daily.

References
Meindl, M., R. Dach, and Y. Jean (eds). IGS Technical Report 2011. AstronomicalInstitute, University of Bern, Bern, Switzerland, pp. 41–50, 2012.

49

Mireault et al.: Natural Resources Canada

50

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

1 Introduction
The IGS Analysis Centre of the European Space Agency (ESA) is located at the European
Space Operations Centre (ESOC) in Darmstadt, Germany. The ESA/ESOC Analysis
Centre has been involved in the IGS since its very beginning in 1992.
In this report we give a summary of the IGS related activities at ESOC in 2012.

2 ESA IGS Analysis
2.1 ESA Products
The ESA/ESOC IGS Analysis centre contributes to all the core IGS analysis centre products, being:• Reprocessed Final GPS products (repro1)– Provided from 1995 to 2008
– Based on 24 hour solutions using 150 stations– Consisting out of Orbits, Clocks (30 s), coordinates, and EOPs
• Final GNSS (GPS+GLONASS) products– Provided weekly. normally on Friday after the end of the observation week.
– Based on 24 hour solutions using 150 stations– True GNSS solutions simultaneously and fully consistently processing of GPS
and GLONASS measurements, using a total of around 55 GNSS satellites– Consisting out of Orbits, Clocks (30 s), coordinates, Ionosphere, and EOPs

51

Springer et al.: European Space Operations Centre• Rapid GNSS (GPS+GLONASS) products– Provided daily for the previous day.
– Available within 3 hours after the end of the observation day– Based on 24hour solutions using 110 stations– True GNSS solutions simultaneously and fully consistently processing of GPS
and GLONASS measurements, using a total of around 55 GNSS satellites– Consisting out of Orbits, Clocks, coordinates, Ionosphere, and EOPs
• Ultra–Rapid GNSS (GPS+GLONASS) products– Provided 4 times per day covering a 48 hour interval; 24 hours of estimated plus
24 hours of predicted products.
– Available within 3 hours after the end of the observation interval which start at
0, 6, 12, and 18 hours UTC.
– Based on 24 hours of observations using 110 stations– True GNSS solutions 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
– Seperate Ionosphere estimates and predictions• Real–Time GNSS services– Generation of two independent real–time solution streams– Analysis Centre Coordination– Generation and dissemination of the IGS Real Time Combined product stream• GNSS Sensor Stations– 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 pilot project where besides being one of the analysis
centres we are also responsible for the analysis centre coordination. Also our efforts inthe scope of the antenna calibarations and satellite orbit modeling working groups are
significant. Furthermore, we will significantly contribute to the IGS MGEX efforts.
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 Main Changes in 2012
The main changes in our processing in 2012 were the following.
• Increase the number of stations from 110 to 150 for the ESA Final products (April)• Change from weekly to daily SINEX (station coordiantes and Earth Rotation Parameters) solutions for the final products52

3 ESA Reprocessing• Update of reference frame from ITRF2008 to the IGS internal realisation of the
ITRF2008• Switch to NAPEOS version 3.7 (November)– Improved Ambiguity Resolution improvements and enhancements now giving
rise to almost always 98% of resolved ambiguities compared to 90% before– Impoved handling of intersystem biases; particularly important for GLONASS• Upgrade of the ESA/ESOC GNSS Sensor Station network

2.3 ESA Product Highlights
The main highlight of the ESA/ESOC Analysis Centre products is that they are one of
the best products available from the individual IGS analysis centres. Secondly the ESA
products are one of the most complete GNSS products. In fact ESA was the first IGS
analysis centre 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 product is 30 seconds.
Another special feature of the ESA products is that they are based on completely independent 24 hour solutions. Although this does not necessarily lead to the best products,
as in the real world the orbits and EOPs are continuous, it does provide a very interesting
set of products for scientific investigations as there is no aliasing and no smoothing.
An other unique feature of our products is that our rapid products are, besides being oneof the best rapid products, also one of the most timely available product. 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 endof the observation day, a very significant difference.

3 ESA Reprocessing
ESA/ESOC has participated in the first IGS reprocessing efforts (repro1) for the IGS contribution to the realisation of the International Terrestrial Reference Frame 2008 (ITRF08).
For this reprocessing effort ESA has processed all historic GNSS data of the IGS from 1994
to 2008. Meanwhile we have repeated the reprocessing using the ITRF08 station coordinates and the corresponding IGS08 antex corrections for the receiver and transmitter
antennas. In this reprocessing the years 1994 to 2008 are done using only GPS observations, but from 2009 the reprocessing does fully include the GLONASS observations andare true GNSS solutions.

53

Springer et al.: European Space Operations Centre
The products from the first ESA official reprocessing efforts based on the ITRF05 reference
frame are available from the official IGS data centres (label “es1”). The most recent
ESA reprocessing products, currently based on the ITRF08, are available from our ftp
ftp://dgn6.esoc.esa.int/igs/repro2 (label “es2”).
Currently only the orbit products are made available. Other products are available on
request. An interesting difference between our “es1” and “es2” reprocessing is that, as
mentioned before, from 2009 our “es2” products are GNSS products. Also for our “es2”products we do generate 30 second clock estimates. We generate these high–rate clock
products because we are also very active in processing GNSS data from Low Earth Orbiting (LEO) receivers. For LEO processing high–rate clocks are very much needed toget accurate orbits based when using the well–known PPP approach for precise orbit
determination.

4 GNSS Sensor Station Upgrade
ESA/ESOC is operating a network of globally distributed GNSS sensor stations, supporting internal and external projects (i.e. GRAS GSN, IGS, Tracking Antenna Positioning
and Monitoring) as well as distributing the data for the scientific community (IGS and
EUREF).
Following the evolution of GNSS systems, new satellites and signals are being made available to the user segment, including new civilian signals for GPS (L2C and L5), CDMA
modulation for GLONASS (L3) and development of new constellations (Galileo, BeiDou,
QZSS).
Until 2010 the ESOC GNSS sensor stations were limited to tracking either GPS or GPS
and GLONASS. It was recognized that the ESOC GNSS sensor station network needed to
be upgraded with state–of–the art technology. This should allow ESOC to keep its high–level of quality and reliability in GNSS operations. The upgrade not only envisages thereplacement of the station equipment of the current GNSS network, but also an expansionof the number of stations in order to enhance the geographical coverage.
To fulfil this purpose a dedicated assessment was made, trading off between the technical requirements and the commercial market costs of the GNSS equipment required forthe upgrade. This resulted in the procurement of 25 Septentrio PolaRx4 receivers and
25 Septentrio Choke Ring MC antennas, for which a deployment schedule was drafted inearly 2012. For the upgrade, the new Septentrio antennas are furthermore complemented
by 4 Leica AR25.R4 antennas, procured earlier, in 2011.

54

5 Real Time Activities

Figure 1: Status of the ESOC GNSS sensor stations as of January 2013

Current upgrade status and way forward
Figure 1 shows the status of the ESOC GNSS sensor stations as of January 2013. Of
the existing ten GNSS sensor stations operated and maintained by ESOC within theexisting network, 7 were upgraded in 2012 to multi–GNSS receivers and antennas. The
remaining 3 (REDU, KIRU and MAL2) are planned to be upgraded in the first quarterof 2013. Building forth on the activities for the existing network, negotiations with several
third parties were initiated during 2012, with the objective of consolidating cooperative
agreements that allow for the deployment of our new ESOC GNSS equipment at external
hosting.

5 Real Time Activities
Over the last 10 years, ESOC has embarked on a program to build a Real Time GNSS
software and network (receiver) infrastructure. RETINA (system for REal TIme NAvigation) has been modeled after ESOC’s experiences in Real Time satellite control systems
and includes many of the elements for data processing, archiving and visualisation thatare common to such systems.
ESOC is utilising this infrastructure by participating in the IGS Real Time Pilot Project,assuming the roles of Real Time Analysis Centre, RT Observing Station Data Provider
and Analysis Centre Coordinator (ACC). In the latter role, ESOC has been generating
and disseminating the IGS Real Time Combination stream after processing the Real Timesolutions from up to ten Analysis Centres.
55

Springer et al.: European Space Operations Centre
Included in the combination solutions are two streams generated by the ESOC Real Time
Analysis Centre. One of these uses orbit information generated by the NAPEOS software,
Springer at al. (2009), which is operated under RETINA scheduling control and provides
orbit updates every 2 hours. The second ESOC solution stream uses the IGS rapid orbit
product, which is updated every 6 hours.
ESOC has been contributing Real Time measurements from eight of its GNSS sensor
station network; New Norcia, Perth, Cebreros, Villaranca, Kiruna, Maspalomas, Malindi
and Kourou. Major upgrades are now in progress to the receiver network, to migrate
to multi–GNSS receiver types and to introduce RTCM streaming capabilities. This has
resulted in disruptions to the data from some of the sites.
Participation in the IGS Real Time activities has stimulated the involvement of ESOCin the development of standards and formats for GNSS data and products. ESOC has
been instrumental in the decision of the IGS to join the Radio Technical Commission for
Maritime Services (RTCM), which is the primary standards setting organisation for RealTime GNSS services. NRCan and ESOC are the two agencies that represent the IGS at
the RTCM meetings. Work with the RTCM has focused on the following areas:• Development of standards and formats for transmission of multi–constellation observations in Real Time (RTCM–MSM)• Development of standards and formats for the transmission of Real Time orbit andclock products (RTCM–SSR)
In addition, the IGS took a high–level decision to form a joint RTCM–IGS working groupfor the further development of the RINEX observation format. The terms of reference of
this WG have been negotiated by ESOC and approved by the IGS Governing Board andby the RTCM. The RINEX working group, chaired by NRCan and ESOC, is now actively
working on the definition of a new version of the RINEX format, RINEX 3.02.
The highlight of this year’s (2012) Real Time ACC activities was the preparation forlaunching the official IGS Real Time service. ESOC will retain the ACC role in thisservice, which will be launched in the first quarter of 2013. In order to ensure a highavailability for this service, combination processes are now running simultaneously at two
servers external to ESOC, in the UK and in Canada (NRCan).

6 Ionosphere Modeling Activities
ESA/ESOC contributes with IONEX products to the IGS Ionosphere Working Groupsince its inception in 1998, initially with daily global ionospheric TEC maps in final mode
(11 days latency). The ESA/ESOC activities for the ionosphere in the frame of the IGS
can be summarised as follows:• 1998: Start routine delivery of global ionospheric TEC maps (11 day latency).
56

6 Ionosphere Modeling Activities• 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.
• March 2009 – January 2010: ESA Study: “GNSS Contribution to Next Generation Global Ionospheric Monitoring” (Feltens at al., 2009; Feltens et al., 2010).
• September 2009: Commence submission of IONEX files containing 1 and 2 days
ahead predicted TEC maps in 2 hour time resolution.
• July 2010: Commence combination of predicted Ionosphere Associate Analysis
Centres (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.
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 for a
multilayer 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 at al. (2009) and Feltens et al. (2010), working out
recommendations for a new ionosphere monitoring system, identifying potential users, andpractical and scientific applications in terms of, among others:• Potential ionospheric observation data sources, e.g., TEC from GNSS and radio
beacons, LEO topside TEC, electron density profiles from LEO radio occultation,
ionosondes, and more.
• Near–Real–Time (NRT) and Real–Time (RT) suitability.
• Predictability of the ionosphere’s state.
• Physical interpretability.

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Springer et al.: European Space Operations Centre

6.1 Current Activities
Presently the IONMON is integrated into the ESOC NAPEOS software. These activities
are almost finished and the inclusion in NAPEOS will enable the IONMON to nearly double the number of ground stations that can be used. In addition the NAPEOS integration
will enable IONMON to process all GNSS data; currently it can only process GPS data.
Figure 2 compares, for one example day (17th January 2013, 18:00 UT), an old IONMON
TEC and RMS map with their counterparts computed with the IONMON integration in
NAPEOS. It clearly demonstrates the improvements, which are primarily visible whencomparing the RMS maps. The high peaks still visible in the IONMON/NAPEOS RMS
map (in Fig. 2 bottom right) indicate those areas where there are hardly any GNSS receivers available, namely South Atlantic and Pacific. Also, once included in NAPEOS,
the least squares fit for 3D modelling will be replaced by a least squares interpolation inorder to assimilate different kind of ionospheric observation data into a background model.
It turned out that, in spite of including F3/COSMIC and CHAMP electron densities in
addition to GNSS TEC observables, the data coverage is still not dense enough to perform
a reliable least squares fit. In addition, the change from least squares fitting of observation
data to an observation data assimilation into a background model will allow for an easyenhancement of time resolution, e.g., from 1 hour to several minutes.

Figure 2: Improved IONMON performance due to integration into NAPEOS (number of groundstations almost doubled, GLONASS in addition to GPS), top left: TEC old IONMON,
top right: TEC IONMON/NAPEOS, bottom left: RMS old IONMON, bottom right:
RMS NAPEOS/IONMON

58

References

6.2 Future Activities
Once being converted from least squares fits to data assimilation, the 3D model will beenhanced for NRT and RT processing and the current background model will commenced
to be upgraded for physics–based approaches, partially by exploiting already existing algorithms of the current 3D IONMON version. The implementation of physically funded
formulae will also be essential for the construction of sophisticated prediction methods.
In parallel to the tasks described above, activities are already ongoing to establish a
new model for the plasmasphere in a cooperative effort with the German Aerospace Center (DLR) in Neustrelitz, Germany. This plasmasphere model will complement the 3D
IONMON. In addition, initial test runs producing 3D IONEX files have been performed
successfully.

7 Summary
The European Space Operations Centre (ESOC) of the European Space Agency (ESA)
Analysis Center has continued to produce “best in class” products for the IGS in 2012.
Practially all products are generated using the Navigation Package for Earth Orbiting
Satellites (NAPEOS) software. NAPEOS is a state of the art software that is highly 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 Centre, ESA/ESOC
is also an Analysis Centre of the IDS and the ILRS.

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

59

Springer et al.: European Space Operations Centre

60

GFZ Analysis Center of IGS
Annual Report for 2012
G. Gendt, Z. Deng, M. Ge, T. Nischan,
M. Uhlemann, G. Beeskow, A. Brandt
Helmholtz–Zentrum Potsdam
Deutsches GeoForschungsZentrum (GFZ)
Department 1: Geodäsie und Fernerkundung
Telegrafenberg A 17, 14473 Potsdam, Germany;e–mail: gendt@gfz-potsdam.de

1 SummaryDuring 2012 the standard IGS product generation was continued with minor changes inthe software EPOS–8.
It was demonstrated to process Galileo data provide by the M–GEX activity.

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

3 Changes in the processing
EPOS–8 is following the IERS Conventions 2010 (Petit and Luzum, 2010). Recent changes
are listed in Tab. 2.
The station network used in the processing is shown in Fig. 1. For the IGS Final, Rapid
and Ultra Rapid about 200, 110, and 90 sites are used, respectively, whereas the sites
providing GLONASS data is steadily increasing.

61

Gendt et al.: GeoForschungsZentrum
Table 1: List of products provided by GFZ AC.

Final (GLONASS since week 1579)
gfzWWWD.sp3
gfzWWWD.clk
gfzWWW7.erp
gfzWWW7.snx
gfzWWW7.sum
gfzWWWD.tro

Orbits for GPS/GLONASS satellites
5–min clocks for stations and GPS/GLONASS satellites
Summary file — including Inter–Frequency Code Biases (IFB) for
GLONASS
1–hour ZPD estimates

Rapid (GLONASS since week 1579)
gfzWWWD.sp3
gfzWWWD.clk
gfzWWWD.erp

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

Ultra (every 3–hours; provided to IGS every 6 hours; GLONASS since week 1603)
gfuWWWD.sp3
gfuWWWD.erp

Adjusted and predicted orbits for GPS/GLONASS satellites

90˚

60˚

30˚

0˚

""

−30˚

−60˚

GPS+GLONASSGPS only
−90˚
−180˚

−150˚

−120˚

−90˚

−60˚

−30˚

0˚

30˚

60˚

90˚

120˚

150˚

180˚

Figure 1: Used IGS stations for combined GPS+GLONASS data processing (GLONASS tracking
sites are marked with yellow squares).

62

3 Changes in the processing

Table 2: Recent Processing changes.

Date

IGS

IGR/IGU

2012-02-13
2012-08-22

1674
1701

1674.01702.3

Change
ZPD with 30–min sampling, internallyBug fix (since 1666) in handling pole tide andatmosphere loading tide S1,S2; most visible in station
clock behaviour

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

IGS Product# of sites# of sites incl.
GLONASS

90
110
200

50
70
110

Ultra
Rapid
Final

Duration
≈ 1h
≈ 2h
≈ 4h

90˚
NYA2

60˚

POTS
WTX3

UND0

ULAB
TASH

STU0
30˚

AUT0

WUH2

LLG0

CHF0

MAO0
BAA0

SGOC

NURK

0˚

SIG0
JOGJ

THX0
HRG0
−30˚

UNX2

COX2

OUS2
OHX0

−60˚
IGS (110)
GPS only
−90˚
−180˚

−150˚

CONGO (23)GPS+GAL
−120˚

−90˚

−60˚

−30˚

0˚

30˚

60˚

90˚

120˚

150˚

180˚

Figure 2: Global network of IGS (green) and CONGO (red) stations, which were set up fordata processing. The 23 CONGO stations realize a good global coverage for practical
GALILEO orbit determination purposes.

63Gendt et al.: GeoForschungsZentrum

4 Processing of M–GEX data
The capability to process Galileo Data has been demonstrated in Uhlemann et al. (2012).
One of the main goals of this study was the precise orbit & clock determination of
GALILEO’s Giove (E01/E16) and IOV (E11/E12) satellites and also the investigationof station tracking behaviour and orbit issues. The observation data mainly stem fromthe modern “COoperative Network for GNSS Observation” (CONGO), but includes all
upgraded GFZ tracking stations which are contributing to MGEX campaign (see Fig. 2).
Finally it can be stated that Galileo satellite orbit accuracies below 10 cm can be reachedwith the chosen processing/network setup.

5 Reprocessing activities
For the IGS reprocessing 2 some improvements were implemented into the latest GFZ
software version EPOS–P8 (Tab. 4).
GPS data of the globally distributed IGS tracking network of 307 stations for the time spanfrom 1994 until end of 2012 were reprocessed (Fig. 3). In the past year GFZ has prepared
the reprocessing of the TIGA GPS network. The data will be analyzed in addition to the
IGS network with about 30 overlapping sites for co–location. About 500 GNSS stations
are available in the TIGA FTP server http://www.sonel.org. The distribution of the
TIGA stations is given in Fig. 4.

Table 4: Model for reprocessing (difference to routine processing).

64

Model

Comment

2nd order iono
GPT2
VMF
EGM2008
FES2004 model
Albedo (antenna thrust)

2nd order ionosphere correction
New empirical meteorological model
Using 6–hour VMF grid files
Updated geopotential filed (IERS2010)
New geopotential ocean tide model
Method from C.J. Rodriguez-Solano

5 Reprocessing activities

600
IGS_REPRO2
TIGA_REPRO2

Number of stations

500
400
300
200
100
0
600

800

1000

1200
GPS week

1400

1600

1800

Figure 3: Number of stations in IGS and TIGA reprocessing 2.

90˚

60˚

30˚

0˚

−30˚

−60˚

−90˚
−180˚

−150˚

−120˚

−90˚

−60˚

−30˚

0˚

30˚

60˚

90˚

120˚

150˚

180˚

Figure 4: Distribution of TIGA stations.

65Gendt et al.: GeoForschungsZentrum

References
Petit, G. and B. Luzum (Eds). IERS Conventions (2010). IERS Technical Note No. 36,
Verlag des Bundesamtes für Kartographie und Geodäsie, Frankfurt am Main, 2010.
Rodriguez–Solano, C. J., U. Hugentobler and P. Steigenberger. Adjustable box–wing model
for solar radiation pressure impacting GPS satellites. Advances in Space Research, 49(7):1113–1128, Elsevier, ISSN 0273–1177, 2012. doi: 10.1016/j.asr.2012.01.016. (software
download from: http://www.iapg.bv.tum.de/albedo/).
Dilssner, F., T. Springer, G. Gienger and J. Dow. The GLONASS–M satellite yaw–attitude
model. Advances in Space Research, 47(1):160–171, 2011.
Uhlemann, M., M. Ramatschi, and G. Gendt. GFZ’s Global Multi–GNSS Network And
First Data Processing Results. IGS Workshop 2012, 23–27 July 2012, Olsztyn, Poland,
2012.

66

CNES–CLS IGS Analysis Center Report 2012
S. Loyer1 , F. Perosanz2 , H. Capdeville1 , A. Mezerette1 ,F. Mercier2 , J.–C. Marty2
1
2

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

1 Introduction
The common CNES–CLS French team joined officially the group of the IGS Analysis
Centers in May 2010. The main motivation was to both participate in the improvement of
the combined IGS products as well as to promote an innovative undifferentiated ambiguity
fixing approach (Laurichesse and Mercier, 2007; Laurichesse et al., 2009) which has been
implemented into the GINS CNES/GRGS software (Marty et al., 2011). We contributeto the final GPS and GLONASS products and our processing strategy is described in
Loyer et al. (2012). More information on our AC activity can also be found at: http://www.igsac-cnes.cls.fr .

2 Products“GRG” products are listed in Tab. 1. From the user point of view, the GPS clock offsets delivered in GRGwwwwn.CLK files have the unique property to keep the integer nature of phaseambiguities in the ionosphere–free phase combination (Loyer et al., 2012). A preliminary
step in which Wide–Lane ambiguities are fixed is however needed. This is straightforward
by using the associated grgwwww7.WSB file containing the so called “Wide–Lane satellite Biases” available at ftp://ftpsedr.cls.fr/pub/igsac . As a consequence, GRG products
allow now ambiguity fixing in single receiver PPP mode (i–PPP) down to 30 s sampling(Petit et al., 2011; Lescarmontier, 2012; Fund et al., 2012). Starting week 1686, WSB
information was included in the header of the CLK files.

67

Loyer et al.: Centre National d’Etudes Spatiales/Collecte Localisation Satellites
Table 1: List of GRG final products delivered weekly
grgwwww7.ERP
grgwwww7.SUM
grgwwww[0-6].SNX
grgwwwwn.SP3
grgwwwwn.CLK
grgwwww7.WSB

ERP (pole, UT1–UTC) solution for 1 week in IGS IERS ERP format
Analysis summary for the week
Daily solutions for EOP and Stations coordinates in SINEX format
with complete information (covariance and constraints)
Daily GNSS ephemeris/clock at 15–min intervals(GPS + GLONASS since week 1617, GPS–only before)
Daily GPS clock at 30–sec intervals
Weekly updated daily GPS wide–lane satellite biases

3 Changes to processing and standards

Our processing changes are driven by the double objective of improving our products andfollowing the IGS and ITRF standards. Table 2 summarizes 2012 main events.

In 2012 we implemented the daily processing of the TRF (with all others AC’s). One
other major product evolution concerns our clock products (CLK files). Before week 1701,
GRG products were inconsistent with those from other ACs and were rejected from theclock product combination. After investigation, we discovered that the GRG reference
frame weekly solution was suffering from a large translation offset (up to 2 cm) in the
Z direction versus the IGb frame. Following the recommendations from the IGS ACC,
starting week 1701, GRG reference frame has been corrected from this Z translation. The
corresponding CLK products became compatible with other ACs solution and started
taking part into the combined IGS clock product (Fig. 1).
Table 2: Evolution of Processing Standards at the GRG IGS AC in 2012.
GPS week
1674
1677
1686
1692
1701
1702
1709

68

Description
Bootstrapping method to fix wide–lane ambiguities
A priori pole coordinates derived from IGS rapid products
GPS clock sampling from 300 s to 30 s
Start including WSB satellite biases values in CLK files header
Non Rotating Origin implemented for Earth rotation modeling
GRG CLK product start contributing to the IGS clock combination
Daily SINEX files delivering (see IGSMAIL #6613)
Adoption of IGb08 reference frame (see IGSMAIL #6663)

4 IGS M–GEX campaign data analysis
COD
EMR
ESA
GFZ
GRG
JPL
MIT
NGS
SIO
IGR

Final Clocks (AC solutions compared to IGS Final)
100(weekly means)

90
80

Clock Std Dev [ps]

70
60
50
40
30
20
10
0
1660

1670

1680

1690
1700
Time [GPS weeks]

1710

1720

1730

NOAA NGS, 16.02.2013 19:27 (GMT)

Figure 1: Final clock products standard deviations.

4 IGS M–GEX campaign data analysis
Following an initiative of the GNSS IGS Working Group, the M–GEX campaign started in
February 2012 (see GNSS WG section). CNES–CLS AC positively responded to the callfor participation with the main objective of evaluating the observations and computing
satellite orbits from the under–deployment Galileo system. Because only two IOV Galileo
satellites were in orbit, we processed GPS and Galileo data together. Thanks to M–GEX,
data from a dense and multi–GNSS network became available. RINEX observation files
were in the 3.0 format which had to be implemented into our different softwares. Because
receivers from several manufacturers were available we started observing the Galileo–
GPS Inter–System Biases (ISB) estimated from different equipment. IOV 1 and IOV 2
results were consistent. Discrepancies between manufacturer receiver technologies generateinconsistencies at the level of several meters in the ISB estimation (Fig. 2). Nevertheless,clock and orbit solutions could be computed, as they rely mainly on phase measurements
information.
Figure 3 shows for example, that both IOV 1 and IOV 2 on–board atomic clocks were
switched from the rubidium to the maser oscillator. The quality of the Galileo orbits
we are producing since July 2012 is at the level of few decimeters (Fig. 4) illustrating

69

Loyer et al.: Centre National d’Etudes Spatiales/Collecte Localisation Satellites
Inter systems Biases (GA12)
20
15

m

10
5
0
-5

220

240

260

280

300

differences (GA11 - GA12)
2

m

1
0
-1
-2

220

240

260

280

300

ABMF 5118K75539 TRIMBLE NETR9 4.60
BRST 5046K71749 TRIMBLE NETR9 4.61
CUT0 5023K67889 TRIMBLE NETR9 4.62
DLF1 5039K70764 TRIMBLE NETR9 4.60
DYNG 70408 TRIMBLE NETR9 4.60
FTNA 77907 TRIMBLE NETR9 4.60
GOP6 496604 LEICA GRX1200+GNS 8.51/6.111
GRAC 5117K75257 TRIMBLE NETR9 4.60
HARB 71645 TRIMBLE NETR9 4.60
KIR8 5038K70490 TRIMBLE NETR9 4.62
LMMF 5118K75440 TRIMBLE NETR9 4.60
M0SE 1830126 LEICA GR25 2.62/6.112
MAR7 5046K71737 TRIMBLE NETR9 4.62
MYVA 1700097 LEICA GR10 2.62/6.112
NKLG 70406 TRIMBLE NETR9 4.60
NURK 344 JAVAD TRE_G3TH DELTA3.4.4B0
NYA2 199 JAVAD TRE_G3TH DELTA3.4.4B0
OBE3 214 JAVAD TRE_G3TH DELTA3.3.5
OHIX 495078 LEICA GRX1200+GNS 8.51/6.110
ONS1 5018K67252 TRIMBLE NETR9 4.62
OUS2 217 JAVAD TRE_G3TH DELTA3.4.4B0
POTS 205 JAVAD TRE_G3TH DELTA3.4.4B0
REUN 5049K72288 TRIMBLE NETR9 4.60
SGOC 349 JAVAD TRE_G3TH DELTA3.4.4B0
TASH 200 JAVAD TRE_G3TH DELTA3.4.4B0
TLSE 70405 TRIMBLE NETR9 4.60
ULAB 208 JAVAD TRE_G3TH DELTA3.4.4B0
UNB3 5152K81074 TRIMBLE NETR9 4.61
USN4 SN11203000923 SEPT POLARX4TR 2.3
USN5 BFN10470205 NOV OEM6 OEM060100RN
WIND 201 JAVAD TRE_G3TH DELTA3.4.4B0
WTZZ JAVAD TRE_G3TH DELTA3.3.5 Nov2011
WUH2 301 JAVAD TRE_G3TH DELTA3.4.4B0

doy 2012

Figure 2: Upper plot: Observed Galileo (E12 = IOV 2) ionosphere–free inter–system biases on
pseudo range observations relatively to BRUX receiver (one point per receiver and perday). Bottom plot: Observed Galileo inter–system biases between IOV 1 and IOV 2.

Internal overlaps200

prn 32prn 31
prn 30prn 29prn 28prn 26prn 25prn 24prn 23prn 22prn 21
prn 20
prn 19prn 18prn 17prn 16prn 15prn 14prn 13prn 12
prn 11
prn 10
prn 09prn 08prn 07
prn 06
prn 05
prn 04
prn 03
prn 02
prn 01GIOVE E52
GIOVE E51
IOV E12IOV E11

3DRMS (cm)

150

100

50

0

180

200

220

240

260

280

300

Doy 2012

Figure 3: 3D RMS 6h orbit overlapping from 30 h solutions. Blue triangles and stars corresponding respectively to GIOVE E51 and E52 satellites. Red triangles and stars correspond70
ing respectively to IOV E11 and E12.

5 Future plans
1.5

1)

Iov1 (E1

1

msec

0.5

2)
Iov2 (E1
0
-0.5
-1

180

200

220

240

260

280

300

doy 2012
Figure 4: IOV 1 and IOV 2 satellite clock offsets estimated relatively to GPS time within theorbit determination process.

the capability to estimate precise Galileo orbits even during the constellation deployment
phase. GRG Galileo orbit and clock products (called “GRM”) are available at: ftp://cddis.gsfc.nasa.gov/pub/gps/products/mgex .

5 Future plans

As recommended by the IGS ACC, second order ionosphere effects as well as satellite antenna thrust models have been implemented in our software but are still under evaluation.
Our AC will participate in the REPRO2 campaign. Thus, a consistent set of GRG GPS
orbit/clock/WSB products will be available to users who may be interested in processing
passed campaigns in an i–PPP mode.
We will continue the investigations on the various signals biases within the GPS, GLONASS
and Galileo systems. The final goal is to fix ambiguities at the zero–difference level fromany GNSS system. We will also continue to contribute to the discussions on the biases
and format definition.

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Loyer et al.: Centre National d’Etudes Spatiales/Collecte Localisation Satellites

References
Fund F., F. Perosanz, L. Testut, and S. Loyer. An Integer Precise Point Positioning
technique for sea surface observations using a GPS buoy. Adv. In Space Research,
online since 25 September 2012. doi: 10.1016/j.asr.2012.09.028 .
Laurichesse, D. and F. Mercier. Integer ambiguity resolution on undifferenced GPS phasemeasurements and its application to PPP. ION GNSS 2007, 20th International Technical
Meeting of the Satellite Division, 25–28 September 2007, Fort Worth, TX, pp 839–84813,
2007.
Laurichesse, D., F. Mercier, J. P. Berthias, P. Broca and L. Cerri. Integer Ambiguity
Resolution on Undifferenced GPS Phase Measurements and its Application to PPP and
Satellite Precise Orbit Determination. Navig J Inst of Navig, ISSN: 00281522, 56(2):135–149, 2009.
Lescarmontier, L., B. Legresy, R. Coleman, F. Perosanz, C. Mayet and L. Testut. Vibrations of the Mertz glacier ice tongue. J Glaciolog, 58(210):665–676, 2012. doi:
10.3189/2012JoG11J089.
Loyer, S., F. Perosanz, F. Mercier, H. Capdeville and J.–C. Marty. Zero–difference GPS
ambiguity resolution at CNES–CLS IGS Analysis Center. Journal of Geodesy, 86(11):991–1003, 2012. doi: 10.1007/s00190-012-0559-2
Marty, J. C., S. Loyer, F. Perosanz, F. Mercier, G. Bracher, B. Legresy, L. Portier,
H. Capdeville, F. Fund, J. M. Lemoine and R. Biancale. GINS: the CNES/GRGSGNSS scientific software. 3rd International Colloquium Scientific and Fundamental Aspects of the Galileo Programme, ESA Proceedings WPP326, 31 August–2 September
2011, Copenhagen, Denmark.
Petit, G., A. Harmegnies, F. Mercier, F. Perosanz and S. Loyer. The time stability of
PPP links for TAI. Proc. Joint conference FCS and EFTF 2011. doi: 0.1109/FCS.2011.
5977299

72

JPL IGS Analysis Center Report, 2012
S. Desai, W. Bertiger, B. Haines, D. Kuang,
C. Selle, A. Sibois, A. Sibthorpe, and J. Weiss
Jet Propulsion Laboratory; California Institute of Technology
4800 Oak Grove Drive, M/S 238–600; Pasadena, CA 91001, U.S.A.
e–mail: shailen.desai@jpl.nasa.gov
phone: +1 − 818 − 354 − 6102

1 Introduction
In 2012, the Jet Propulsion Laboratory (JPL) continued to serve as an Analysis Center(AC) for the International GNSS Service (IGS). We contributed orbit and clock solutions
for the GPS satellites, position, clock and troposphere solutions for the ground stations
used to determine the satellite orbit and clock states, and estimates of Earth rotation
parameters (length–of–day, polar motion, and polar motion rates). This report summarizes the activities at the JPL IGS AC in 2012 and our preparations for the 2013 IGS
reprocessing campaign.
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–hours.
Each of our daily solutions is determined independently from neighboring solutions, namely
without applying any constraints between solutions. We started generating and delivering
daily SINEX files starting with GPS week 1702.
Table 1: JPL AC Contributions to IGS Rapid and Final Products.
Product

Description

Rapid/Final

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

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

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

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Desai et al.: Jet Propulsion Laboratory
The JPL IGS AC also generates Ultra–Rapid orbit and clock products for the GPS constellation (Weiss et al., 2010). These products are generated with a latency of less than
2 hours and are updated hourly. Although not submitted to the IGS, our Ultra–Rapid
products are available in native GIPSY formats at ftp://sideshow.jpl.nasa.gov/pub/
JPL_GPS_Products/ultra.

2 Processing Software and Standards
The JPL AC continues to utilize the GIPSY/OASIS software package to generate ourcontributions to the IGS. Starting February 5, 2012, we used GIPSY/OASIS version 6.1.2
to generate our IGS contributions. A complete description of our current processing
approach can be found at: http://igscb.jpl.nasa.gov/igscb/center/analysis/jpl.
acn. Of note, we continue to use empirical GPS solar radiation pressure models developedat JPL instead of the DYB–based strategies that are commonly used by other IGS analysis
centers. This choice is based upon an extensive evaluation of various internal and external
metrics after testing both approaches with the GIPSY/OASIS software (Sibthorpe et al.,2011).

3 Preparations for 2013 IGS Reprocessing Campaigns
In November 2012 we completed a preliminary reanalysis of historical GPS data from
August 16, 1992 to present in the IGS08 reference frame, and made these products publically available. They are available at ftp://sideshow.jpl.nasa.gov/pub/jpligsac
in IGS formats, and at ftp://sideshow.jpl.nasa.gov/pub/JPL_GPS_Products/Finalin native GIPSY formats. A notable benefit of these preliminary reprocessed IGS08–
products is that they include our so–called “wide–lane phase bias” (WLPB) file for theentire time span of the products. The WLPB files enable single–receiver phase ambiguity
resolved positioning when used with the GIPSY/OASIS software (Bertiger et al., 2010)
and our GPS orbit and clock products. Also of note, high–rate (30–second) GPS clock
products in native GIPSY format were also generated in this preliminary reanalysis forthe period May 5, 2000 to present. They are also generated operationally in native GIPSY
format for our Rapid and Final solutions.
Figures 1 and 2 provide a measure of the precision of the GPS orbit and clock products
from this preliminary reanalysis, and are compared to our submissions to the last IGS05
reprocessing campaign. Products from our preliminary reanalysis have demonstrated anaverage variance reduction of 25% and 12% in GPS satellite orbit and clock precision for
1996–2011, respectively (Desai et al., 2011). Furthermore, an additional 0.6 satellites per
day are included in our preliminary IGS08 reanalysis compared to our IGS05 submissions.
Results for 1992–1995 are especially affected by the sparse availability and distribution of
the ground network.
74

3 Preparations for 2013 IGS Reprocessing Campaigns

Daily Median of 3D
Orbit Precision (cm)30
IGS05 Products
IGS08 Products

25
20
15
10
5
0
1992

1996

2000

Year

2004

2008

2012

Figure 1: GPS satellite orbit precision of preliminary reanalysis of historical data from August
16, 1992 to present. Precision is measured as RMS of 3–D orbit overlap differences foreach GPS satellite using middle 5 hours of 6–hour daily overlap.

Daily Median ofClock Precision (ns)0.2
IGS05 Products
IGS08 Products

0.15
0.1

0.05
0
1992

1996

2000

Year

2004

2008

2012

Figure 2: GPS satellite clock precision of preliminary reanalysis of historical data from Aigust
16, 1992 to present. Precision is measured as RMS of clock overlap differences for eachGPS satellite using middle 5 hours of 6–hour daily overlap.

75

Desai et al.: Jet Propulsion Laboratory
Our contributions to the 2013 reprocessing campaign are expected to benefit from theresults and experience gained from our preliminary analysis. We expect to apply thefollowing changes to our processing standards for JPL’s contributions to the 2013 reprocessing campaign.
1. Second order ionospheric corrections (Garcia–Fernandez et al., 2012).
2. S1/S2 atmospheric loading corrections.
3. Modified empirical solar radiation pressure models, e.g. (Sibthorpe et al., 2010).
4. Antenna thrust models.
Development and testing of these changes started in 2012 and are expected to be completed
in early 2013. We will deliver the full suite of products listed in Tab. 1 to the 2013 IGS
reprocessing campaign, and also include high–rate (30–second) GPS clock products for1996 onwards. We also plan to include high–rate (30–second) GPS clock products in ouroperational deliveries to the IGS before the end 2013.

4 Future Activities
Our primary focus in 2013 is to develop, test, and tune our software and processing
standards in support of the second IGS reprocessing campaign, and to deliver products to
the IGS for at least 1994–2012.

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

References
Bertiger, W., S. Desai, B. Haines, N. Harvey, A. Moore, S. Owen, and J. Weiss. Single
receiver phase ambiguity resolution with GPS data. J. Geodesy, 84(5):327–337, 2010.
doi: 10.1007/s00190-010-0371-9 .
Desai, S. D., W. Bertiger, B. Haines, J. Gross, N. Harvey, C. Selle, A. Sibthorpe, andJ. P. Weiss. Results from the Reanalysis of Global GPS Data in the IGS08 Reference
Frame. 2011 Fall Meeting, AGU, San Francisco, CA, USA, 05–09 December, 2011.

76

References
Garcia–Fernandez, M., M. Butala, A. Komjathy, and S. Desai. Intercomparison of approaches for modeling second order ionospheric corrections using GNSS measurements.
2012 Fall Meeting, AGU, San Francisco, CA, USA, 03–07 December, 2012.
Sibthorpe, A., J. Weiss, N. Harvey, D. Kuang, and Y. Bar–Sever. Empirical modeling ofsolar radiation pressure forces affecting GPS satellites. AGU Fall Meeting, San Francisco,
CA, USA, December 13–17, 2010.
Sibthorpe, A., W. Bertiger, S. D. Desai, B. Haines, N. Harvey, and J. P. Weiss. An evaluation of solar radiation pressure strategies for the GPS constellations. J. Geodesy, 85(8):505–517, 2011. doi: 10.1007/s00190-011-0450-6 .
Weiss, J. P., W. Bertiger, S. D. Desai, B. J. Haines, and C. M. Lane. Near real time GPS
orbit determination: Strategies, performance, and applications to OSTM/Jason–2. Adv.
Astronaut. Sci., 137:439–452, 2010.

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Desai et al.: Jet Propulsion Laboratory

78

MIT IGS Analysis Center Report for 2012
T. A. Herring, R. W. King
Room 54–820A, MIT
77 Massachusetts Avenue, Cambridge, MA 02139
e–mail: tah@mit.edu;
phone: +1 617 253 5941

1 Introduction
In this report, we discuss the changes from our MIT analysis that have been made during
the 2012 and some of the results obtained for satellite phase center variations, ground–based radome changes, and the changes when we moved to daily processing. Overall,
except for changes due to daily processing, our analysis procedures have remained thesame as reported in last year’s report.
We look in some detail at the results when the radome was removed from YAR2 for 128
days between days 144–272 of 2012. The results of this analysis are currently inconclusive
based on global analysis of these data. Local analysis of the data indicates that the impactof the radome is rather small (dNEU 0.6, 1.5 and −2.0 mm) but the systematic multipath
at the site, not changed by removing the radome may have a bigger impact.

2 MIT products
MIT generates weekly submissions to the IGS final orbit and clock products. With theswitch to daily processing, our submissions consist of (where WWWW is GPS week and[0−6] are the values between 0 and 6):
mit<WWWW>7.sum which is a summary file consisting of site statistics (phase andposition root–mean–square (RMS) scatters, RMS scatter of clock fits to linear trendsof the reference clocks for each day of the week, RMS scatters of the orbit overlaps(3.75 hrs on both sides of each orbit) and Earth orientation parameters (EOP)
estimates in IERS standard format.
mit<WWWW>7.erp.Z Earth rotation parameters for 9–days IERS format

79

Herring and King: Massachusetts Institute of Technology
mit<WWWW>[0-6]. sp3.Z Daily GPS satellite orbits tabulated at 15 minute intervals
with satellite clock estimates.
mit<WWWW>[0-6].clk.Z Daily GPS satellite clocks tabulated at 30–second intervals
for the satellites and reference ground station. Other ground station clocks aretabulated at 15 minute intervals.
mit<WWWW>[0-6].snx.Z Daily coordinate and EOP SINEX file with minimum constraints applied to orient the solution to the IGS08 reference frame.
We also make available through ftp://everest.mit.edu binary global files for daily andweekly solutions, radiation parameter constraints, and position time series. GAMIT/GLOBK
users can directly use these products. The global position and orbit files have estimatesof the satellite phase centers, loosely constrained, and are a resource for analyzing theestimates of the these offsets. The estimates of the phase centers should be tightly constrained if consistency with the IGS models is needed. The files containing process noise
values for solar radiation parameters can be used to apply similar orbital constraints to
those used in the MIT analysis (see discussion below).

3 Analysis methods
Our approach to forming networks has remained the same as reported last year. We still
use six networks each with 50 stations and network with two overlapping sites between eachpair of networks. Since the networks are formed dynamically each day there is variation’s
day–to–day in the selection of sites. We do have a core list of stations, including the IGS
reference sites and selected clock sites, which will be included in the network if they areavailable. This year we also added additional sites around Antarctica but have now become
available and who’s data are available through the international archives. In figure 1 weshow the distribution of sites used throughout the year in the MIT processing. Becauseof the dynamic site distribution not all sites are used all the time, there is however a coregroup of sites, shown in magenta, that are used in nearly every day of processing.

3.1 Switch to daily processing
Starting on GPS week 1702, day 232 of 2012, August 19, the MIT processing was switched
to daily ITRF estimates. The implementation of this change was done primarily by introducing process noise into the daily position estimates in the MIT weekly solutions. Prior
to the switch, the MIT orbits were determined using a smoothing Kalman filter with thestation positions estimated, but not varying, during the week. With the daily processing,
the same type of analysis is performed accept that process noise, in the form of a random
walk allowing one meter changes each day, was introduced into the Kalman filter run.
With the implementation of the daily processing, daily SINEX files are generated andsubmitted without daily orbit files.
80

3 Analysis methods

60˚

30˚

0˚

8 sites less than 7days
24 sites 7−30 days
42 sites 30−90days
196 sites 90−360days
75 sites All year

−30˚

−60˚

180˚

270˚

0˚

90˚

180˚

Figure 1: Distribution of sites used during 2012 in the MIT processing. Sites that are not used
all the time arise because of availability of data and the selection criterion used to form
global networks. Sites that appear only a few times occur because of lack of data fromsites in the region that would normally be used in the processing. A total of 345 sites
were included in the processing during the year.

3.2 Solar radiation parameter estimation and Clock Estimation
The procedures used in the MIT analysis for determining the solar radiation pressure
parameters and the clock estimates remain unchanged from last year’s report. The valuesof the once–per–revolution solar radiation parameter process noise values are available
from the ftp://everest.mit.edu ftp site in the MIT_SRP folder. Even with the daily
processing, one set of parameters is used from each week unless there is a specific issue
that needs to be manually accounted for

3.3 Position estimate quality after switch to daily processing
In Tab. 1, we compare the median we did RMS scatters of the position estimates for theperiod in 2012 after the change to daily processing (August 19) with the corresponding
period from 2011 went weekly processing was being carried out. This seems to be little
impact on the position RMS scatter of switching to daily processing. The slight degradation might be due to the weekly solutions forcing positions to not change during theweek. In the daily processing, the site positions are able to change day–to–day during theweek. In general we conclude that daily processing has not impacted the position WRMS
significantly. In terms of orbit agreement, the MIT daily orbits are more consistent with
the IGS final orbit after the change. The only change in the MIT processing was thetreatment of the station positions being stochastic during each of the weekly processing
runs.
81

Herring and King: Massachusetts Institute of Technology
Table 1: Median weighted RMS (WRMS) scatter of MIT position estimates for the periods
Aug 19−Dec 31, 2012 (after switch to daily processing) and the same interval in 2011
when weekly processing was performed. In both analyses, the orbits from the MIT
solutions were used in the position determinations.

Analysis

North
(mm)

East
(mm)

Height(mm)# sites

Daily 2012/8/19 to 2012/12/31
Daily 2011/8/19 to 2011/12/31

1.3
1.3

1.4
1.3

4.8
4.6

286
316

4 Ancillary analyses
4.1 Satellite phase center characteristics
In our routine analyses we also estimate positions of the satellite phase centers. For the
products that we submit to the IGS, including SINEX files, the phase center offsets aretightly constrained to their values given in the ANTEX file. In Tab. 2, we give the meanvalues of the adjustments to the XYZ positions of the satellite phase center locations since
the adoption of the IGS08 system for the 2012 processing. Due to the week selection,
up to 49 weekly estimates are available. Analysis of the temporal behavior of the offsets
show there are systematic variations with time and in the X and Y components suggestthat there are yaw modeling errors that are being absorbed into the phase center position
estimates. We are still analyzing results.
We are saving the average values of the phase residuals as a function of elevation angle
at individual stations and as a function of nadir angle for satellites. In Fig. 2, we show
the average residuals, for the last 60 days of 2012, as a function of nadir angle for PRN 16(noted last year for having systematic residuals) and PRN 24 (latest Block IIF satellite
to launch). While the magnitude of the patterns is small, they are indicative of small
remaining errors in the satellite antenna phase center models. Since there are variationsin the estimates of the positions of the phase centers relative to center of mass between
satellites of the same type, variations in the nadir dependence could also be expected. (Thephase residuals are generated with the nominal phase center position and hence some partof the pattern seen does reflect possible offsets in this location. In the case of PRN 16, theestimated offset is quite small and would have only a small effect on the pattern).

4.2 Radome removal tests: YAR2
During 2012, radomes were removed for YAR2, FAIR, and GODE to determine the impactof the radome on the positions estimates. We are looked at the changes in the positions82

4 Ancillary analyses

Table 2: Mean values of the adjustments to the IGS08 phase center locations based on analysisof data after GPS week 1632.
PRN

Type

Mean dX
(mm)

RMS
(mm)

Mean dY
(mm)

RMS
(mm)

Mean dZ
(mm)

RMS
(mm)

#

01
02
03
04
05
06
07
08
09
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27∗
28
29
30
31
32

IIF
IIR–B
IIA
IIA
IIR–M
IIA
IIR–M
IIA
IIA
IIA
IIR–A
IIR–M
IIR–A
IIR–A
IIR–M
IIR–A
IIR–M
IIR–A
IIR–B
IIR–A
II–A
IIR–B
IIR–B
IIF
IIF
IIA
IIA
IIR–A
IIR–M
IIA
IIR–M
IIA

−2.5
33.3
5.6
−7.9
25.9
−0.7
18.6
−14.7
−22.6
−5.3
−3.6
36.0
20.0
26.1
31.2
40.8
31.6
40.1
37.6
29.4
28.8
25.0
38.6
−2.8
−10.7
−10.5
−19.6
23.5
37.6
−2.8
18.9
9.5

9.4
30.3
21.6
18.9
31.4
19.8
11.2
13.5
7.8
19.4
17.0
19.4
21.0
24.4
24.6
24.9
31.3
29.9
33.5
33.7
33.1
29.2
23.6
16.6
11.5
19.3
7.3
22.0
33.0
17.0
11.7
20.9

−19.4
−5.9
−4.8
23.6
−3.7
−5.7
4.3
51.1
3.4
14.2
−14.5
−14.5
−2.1
−1.7
−5.1
−10.8
−4.6
−6.1
−9.3
−2.2
2.0
2.5
−2.4
−31.5
−29.8
4.3
37.8
3.7
−7.9
−9.6
0.0
39.4

14.6
10.5
26.1
10.1
9.8
13.2
8.6
30.2
13.4
10.6
8.3
9.0
8.5
7.6
10.4
9.9
8.4
10.1
11.4
10.5
10.2
15.0
7.4
5.8
15.4
23.6
13.1
7.2
9.9
19.4
7.8
21.7

−72.9
−53.6
5.6
−88.4
−48.6
−2.0
−31.7
−53.4
−96.6
−93.2
50.8
−109.4
10.4
−8.2
−95.3
−3.1
−52.9
−54.8
−17.2
32.3
−40.8
−70.1
−7.1
−293.5−122.6−123.4
−91.0
−16.5
−77.1
13.6
−39.9
−15.4

69.0
73.1
82.9
71.9
66.5
7.3
57.5
67.9
61.0
56.9
83.6
49.3
50.8
61.4
84.3
81.4
67.7
86.8
56.4
62.7
77.1
73.7
43.9
53.8
69.6
88.0
53.8
55.6
87.3
66.3
59.8
69.6

49
49
49
49
49
49
49
49
49
49
49
49
49
49
49
49
49
49
49
49
49
49
49
8
49
49
40
49
49
49
49
49

∗

∗

PRN 27 was assigned to SV 49 (block IIR–M) on 2012-10-18; the estimate here isfor the Block IIA SV 27 assigned to this PRN until this date.

83

Herring and King: Massachusetts Institute of Technology
Site G24

Site G16

RMS G24 1.29 mm # 25080 data from 372 files
WRMSMEAN G24 0.52 mm, NRMS 11.51

RMS G16 1.93 mm # 25849 data from 390 files
WRMSMEAN G16 0.75 mm, NRMS 18.51

5

Mean Phase Residual (mm)Mean Phase Residual (mm)

5

0

−5

0

0

−5

1

2

3

4

5

6

7

8

9

10

11

12

13

14

0

1

2

3

4

5

Nadir Angle (degrees)

6

7

8

9

10

11

12

13

14

Nadir Angle (degrees)

Figure 2: Average phase residuals to PRN 16 (left) and PRN 24 (right) as function of nadir angle.
Each line is from one day of data and the color of line progresses from blues to reds asa function of time. The green dots show the average values. The phase center location
is fixed to the IGS08 value, with average estimate of the adjustment to those values
given in Tab. 2. (Values in Tab. 2 not applied to the phase residuals).

during these intervals and the effect on the phase residuals. All three of these sites havesystematic phase residual dependence on elevation angle. FAIR is the worst, followed by
YAR2 (shown in Fig. 3) and then GODE. Removing the radomes had no clear effect on
the phase residuals. The position changes in general were several millimeters and not
clearly above the levels of correlated noise. Results for YAR2 are shown in Fig. 4 wherechanges of 2 mm and −5 mm (averages of before and after values) in east and height seemsignificant. Short baseline processing the YAR2−YARR baseline for 8 days before andSite YAR2
10

RMS YAR2 2.27 mm # 3177 data from 40 files
WRMSMEAN YAR2 1.68 mm, NRMS 10.64

Mean Phase Residual (mm)

5

0

−5

−10
0

10

20

30

40

50

60

70

80

90

Elevation Angle (degrees)

Figure 3: Average phase residuals as a function of elevation angle at YAR2 during the interval
when the radome was not on the antenna. Visually, the averages residuals look thesame when the radome is present.

84

4 Ancillary analyses

Position (mm)

5

WRMS:

YAR2.mit.dfixd_frame−YARR.mit.dfixd_frame North
1.09 +− 0.51Data
mm/yr

0

−5
2012
5

Position (mm)0.90 mm NRMS: 0.40 #: 332 data Rate:

WRMS:

2012.2

2012.41.24 mm NRMS: 0.47 #: 332 data Rate:

2012.62012.82013

YAR2.mit.dfixd_frame−YARR.mit.dfixd_frame East
−1.45 +− 0.71Data
mm/yr

0

−5
2012
15

WRMS:

2012.2

2012.4

3.56 mm NRMS: 0.45 #: 332 data Rate:

2012.62012.82013

YAR2.mit.dfixd_frame−YARR.mit.dfixd_frame Up
3.56 +− 2.04 Data
mm/yr

Position (mm)

10
5
0
−5
−10
−15
2012

2012.2

2012.42012.62012.82013

Figure 4: Time series in North, East and Up of difference in position between YAR2 and thenearby YARR sites (≈ 4 m separation) during the periods with (start and end) andwith a radome over the antenna. Most of the times these two sites are not processed
together. The offsets when the radome is removed and replaced are N 0.7,−0.9 mm, E
3.3,−1.0 mm and U −6.7,4.0 mm and are symmetric.

10 days after the radome change show offsets of 0.6, 1.5 and −2.0 mm in North, East and
Up. The uncertainties of these estimates are 0.2 mm NE and 0.4 mm U. There is also small
offset in the atmospheric delay that will be correlated with the height estimates. These
values are likely to be more robust than the global processing where normally YAR2 andYARR are in different networks in the processing. We are still looking that the other sites.
Their offsets are of similar size but they do not have nearby sites that can be used forshort baseline processing.

85

United States Naval Observatory Analysis Center
Report 2012
C. Hackman, S. Byram, V. Slabinski, and J. Tracey
United States Naval Observatory
3450 Massachusetts Avenue Northwest
Washington DC 20392 USA
e–mail: christine.hackman@usno.navy.mil
phone: 202 762 1428

1 Introduction
The United States Naval Observatory (USNO), located in Washington, DC, USA has
served as an IGS Analysis Center (AC) since 1997, contributing to the IGS Rapid andUltra–rapid Combinations since 1997 and 2000, respectively. USNO contributes a fullsuite of rapid products (orbit and clock estimates for the GPS satellites, earth rotation
parameters (ERPs), and receiver clock estimates) once/day to the IGS by the 1600 UTC
deadline, and contributes the full suite of ultra–rapid products (post–processed and predicted orbit/clock estimates for the GPS satellites; ERPs) four times/day by the pertinent
IGS deadlines.
USNO has also coordinated IGS troposphere activities since 2011, producing the IGS Final
Troposphere Estimates and chairing the IGS Troposphere Working Group (IGSTWG).
The USNO AC is hosted in the GPS Analysis Division (GPSAD) of the USNO Earth
Orientation Department (EOD). Dr. Christine Hackman, GPSAD chief, directs AC activities, chairs the IGSTWG, and serves on the IGS Governing Board. Dr. Sharyl Byram
oversees production of the IGS Final Troposphere Estimates. All GPSAD members, including Dr. Victor Slabinski and Mr. Jeffrey Tracey, participate in AC work. Mr. Jim
Rohde joined GPSAD in 2012 as a contractor.
USNO AC products are computed using Astronomical Institute of the University of Bern
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).
1

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

86

2 Developments in 2012
Ultra–rapid products are generated using network solutions. IGS Final Troposphere estimates are generated using PPP.
GPSAD also generates a UT1−UTC–like quantity, UTGPS, five times/day. UTGPS isa GPS–based extrapolator of VLBI–based UT1−UTC measurements. The IERS2 Rapid
Combination/Prediction Service uses UTGPS to improve post–processed and predicted
estimates of UT1−UTC. Mr. Tracey oversees UTGPS. For more information, pleasecontact the AC.
USNO rapid, ultra–rapid and UTGPS products can be downloaded immediately after computation from http://www.usno.navy.mil/USNO/earth-orientation/gps-products . IGS
Final Troposphere estimates can be downloaded at ftp://cddis.gsfc.nasa.gov/gps/
products/troposphere/zpd .

2 Developments in 2012
The USNO AC began incorporating measurements from the Russian GLONASS GNSS
into processing in 2011 (Byram and Hackman, 2012b,c). Dr. Sharyl Byram completed development of USNO combined GPS/GLONASS ultra–rapid and rapid products in 2012.
The USNO ultra–rapid products are now under study at the IGS for possible inclusion in
the IGS “IGV” GPS/GLONASS ultra–rapid combination. The USNO rapid GPS/GLONASS
products are thus far distributed only internally, as the IGS does not compute analogous
estimates.
GPSAD ultra–rapid predictions could provide high–precision real–time PNT to users.
GPSAD began testing position/timing accuracy achievable using its ultra–rapid predictedvalues in 2012 (Hackman and Matsakis, 2012; Hackman, 2012b,c,d). 7−9 mm position precision and ns–level timing accuracy were achieved in initial PPP tests (Hackman, 2012b).
Significant improvements in satellite clock prediction accuracy should enable significant
improvements in position accuracy (Hackman, 2012c,d).
Division personnel (C. Hackman, S. Byram, V. Slabinski, J. Tracey) wrote/delivered over adozen publications/presentations in 2012, representing USNO at scientific– and defense–oriented symposia such as the IEEE International Frequency Control Symposium, IGS
2012 Workshop, American Geophysical Union 2012 Fall Meeting, Office of Naval Research
Science and Technology Partnership Conference, Precise Time and Time Interval Systems
and Applications Meeting, Institute of Navigation (ION) Position, Location and Navigation Symposium, ION Joint Navigation Conference, and AAS Division on Dynamical
Astronomy.
2

International Earth Rotation and Reference Systems Service

87Hackman et al.: United States Naval Observatory

3
3

Publications/Presentations in 2012
Pertaining to USNO IGS Work

Byram, S. and C. Hackman. Computation of the IGS Final Troposphere Product by the
USNO. IGS Workshop 2012, 23–27 July 2012, Olsztyn, Poland, 2012a.
Byram, S. and C. Hackman. GNSS-Based Processing at the USNO: Incorporation of
GLONASS Observations. IGS Workshop 2012, 23–27 July 2012, Olsztyn, Poland, 2012b.
Byram, S. and C. Hackman. High-Precision GNSS Orbit, Clock and EOP Estimation
at the United States Naval Observatory. Proc. 2012 IEEE/ION Position Location andNavigation Symposium, 659-63, 2012c.
Church, W. (V. Slabinski, mentor). GPS Satellite Orbits: Solar Radiation Force Evaluation Software. USNO Professional Seminar, 16 August 2012.
Hackman, C. GPS Code/Carrier-Phase Time Frequency Transfer. IEEE International
Frequency Control Symposium Tutorials, 149 pp, 2012a.
Hackman, C. Near-Real-Time and Other High-Precision GNSS-Based Orbit/Clock/EarthOrientation/Troposphere Parameters Available from USNO. Proc. 2012 ION Joint Navigation Conference (JNC), 1274-1288, 2012b.
Hackman, C. Impact of Orbit, Clock, and EOP Errors in GNSS Precise Point Positioning.
2012 Fall Meeting, AGU, San Francisco, CA, USA, 03–07 December, 2012c.
Hackman, C. Accuracy/Precision of USNO Predicted Clock Estimates for GPS Satellites.
Proc. 44th Ann. Precise Time and Time Interval (PTTI) Systems and Applications
Meeting, pp. 94–99, 2012d.
Hackman, C. and S. Byram. IGS Troposphere Working Group 2011. IGS Technical Report
2011, 211-8, 2012.
Hackman, C., S. Byram, V. Slabinski, and J. Tracey. United States Naval Observatory
Analysis Center Report 2011. IGS Technical Report 2011, 99-106, 2012a.
Hackman, C. and D. Matsakis. Precision and Accuracy of USNO GPS Carrier Phase Time
Transfer: 2012 Update. Proc. 2012 IEEE International Frequency Control Symposium,
94–99, 2012.
Hackman, C., V. J. Slabinski, J. C. Tracey, and S. M. Byram. USNO Analysis Center
Progress 2010-2. IGS Workshop 2012, 23–27 July 2012, Olsztyn, Poland, 2012b.
Slabinski, V. LAGEOS Satellite Drag: the Eclipse Season Mystery Remains. 43rd Meetingof the American Astronomical Society Division on Dynamical Astronomy, oral presentation #4.04, 2012.

88

4 Product Performance 2012

4 Product Performance 2012
Figures 1-4 show the 2012 performance of USNO rapid and ultra–rapid products, withsummary 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 22 mm (24–h post-processed segment) and 49 mm (6–hpredict) wrt the IGS rapid combined orbits.
USNO CLOCKS WRT IGS RAPIDS, 1 JAN - 31 DEC 2012USNO ORBITS WRT IGS RAPIDS 1 JAN - 31 DEC 2012
10000

200

150

ult, pred100

rap stdev

PS

WRMS, MM1000

rap rms

ult, past
rapid

ult pred

100

50

56000

56100
MJD

56200

10
55900

56300

Figure 1: Weighted RMS of USNO GPS orbit
estimates with respect to IGS Rapid
Combination, 2012. “Ult, past”
refers to 24–hour post–processed
section of USNO ultra–rapid orbits.
“Ult, pred” refers to first six hoursof ultra–rapid orbit prediction.

56000

56100
MJD

56200

56300

Figure 2: RMS/standard deviation of USNO
rapid GPS clock estimates and
RMS of USNO ultra–rapid GPS
clock predictions with respect to
IGS Rapid Combination, 2012.

USNO RAPID POLAR MOTION WRT IGS RAPIDS, 1 JAN - 31 DEC 2012
600

400

200
MICRO ARC SEC

0
55900

0

rap x
rap y

-200

-400

-600
55900

56000

56100
MJD

56200

56300

Figure 3: Difference between USNO rapid polar motion estimates and IGS Rapid
Combination, 2012.

89

Hackman et al.: United States Naval Observatory
USNO ULTRA-RAPID PM PREDICTS WRT IGS RAPIDS, 1 JAN - 31 DEC 2012

1500

1000

1000

500

500

MICRO ARC SEC

MICRO ARC SECUSNO ULTRA-RAPID POST-PROCESSED PM WRT IGS RAPIDS, 1 JAN - 31 DEC 2012

1500

0

0

-500

-500

-1000

-1000

-1500
55900

56000

56100
MJD
ult past x

56200

56300

-1500
55900

ult past y

56000

56100
MJD
ult pred x

56200

56300

ult pred y

Figure 4: Difference between USNO ultra-rapid polar motion estimates and IGS Rapid Combination, 2012.
Table 1: Accuracy/Precision of USNO Rapid and Ultra–Rapid Products: 1 Jan – 31 Dec 2012.
All statistics computed with respect to IGS Combined Rapid Products.
USNO GPS satellite orbits

USNO GPS–based polar
motion estimates

USNO GPS–based clock
estimates

Statistic: median weighted
RMS difference
units: mm

Statistic: RMS difference

Statistic: median standard
dev. and RMS of difference
units: ps

rapid

17

A

B

ultra–rapid
past 24 h 6–h predict
22

49

units: 10−6 arc sec
rapid

ultra–rapid
past 24 h 24–h predict

x:166
y:195

x:402
x:175A
y:226

x:510
x:355A
y:319

rapid
past 24 hultra–rapid
6–h predict

STDEV: 67B
RMS: 164

RMS: 2929

Omitting data from MJD 56211–58 during which time USNO ultra–rapid PM–x values took a large
excursion from IGS rapid values. USNO ultra–rapid PM–x values have since returned to normal.
Computed for 1 Jan – 28 Oct 2012; IGS ceased publishing this statistic thereafter.

USNO rapid clocks had a 67 ps standard deviation (STDEV) and 164 ps RMS wrt IGS
combined rapid clocks. USNO ultra–rapid clock predictions (first six h) had a 2929 ps
RMS wrt IGS combined rapid clocks.
USNO rapid polar motion (PM) estimates had RMS differences wrt IGS rapid combined
values of (x, y) 166 and 195 micro arc sec. USNO ultra–rapid PM estimates differed from
IGS rapid combined values (x, y) by 402 and 226 micro arc sec for the 24–h post–processedsegment and 510 and 319 micro arc sec for the 24–h predict. The ultra-rapid PM–x values
took large excursions from the IGS rapid values during MJDs 56211−58 as Fig. 4 shows.
When values from these dates are omitted the ultra-rapid RMS PM-x residuals reduceto 175 and 355 micro arc sec for the post–processed and predicted segments, respectively,

90

Referencescomparable to the PM–y residuals.
USNO ultra–rapid PM residuals improved sufficiently toward the end of 2012 to becomecomparable in size to those of other ACs and are thus under consideration for re–inclusionin the IGS ultra-rapid combination, having been given zero weight during 2012.

References
Dach, R., U. Hugentobler, P. Fridez, M. Meindl (eds). Bernese GPS Software Version 5.0(user manual). Astronomical Institute of University of Bern, Bern, Switzerland, 2007.
Webb, F. H. and J. F. Zumberge (eds.). An Introduction to GIPSY/OASIS–II: Precision
Software for the Analysis of Data from the Global Positioning System. JPL internal
publication D–11088, Jet Propulsion Laboratory, Pasadena, California, 1997.
Zumberge, J. F., M. B. Heflin, D. C. Jefferson, M. M. Watkins, and F. H. Webb. Precise
Point Positioning for the Efficient and Robust Analysis of GPS Data from Large Networks. J. Geophys. Res., 102(B3):5005–17, 1997.

91

Hackman et al.: United States Naval Observatory

92

WHU IGS Analysis Center Technical Report 2012
C. Shi, M. Li, Q. Zhao, X. Lei, J. Liu
GNSS Research Center of Wuhan University, China

1 Introduction
Wuhan University Analysis Center (WHU) was officially authorized by IGS organization
on 8th August 2012 after an intensive evaluation of more than half a year. As a consequence, this is our first contribution to the IGS technical reports. The main motivations
to become an IGS Analysis Center were to evaluate the performance of the PANDA (Positioning And Navigation Data Analyst) software package developed by Wuhan University
and to contribute to the discussions on GNSS processing strategy, model refinement, etc.
This report introduces the WHU Analysis Center and gives an overview of the WHU
activities during 2012.

2 WHU IGS Analysis Center
WHU is located at the GNSS Research Center of Wuhan University, China. All the solutions and results are produced by the latest development version of the PANDA software.
Up to now, WHU mainly contributes to the IGS ultra–rapid and rapid products, including GPS/GLONASS satellite orbits and clock errors as well as ERPs (Earth Rotation
Parameters).

93

Shi et al.: Wuhan University

2.1 Developments
The development of WHUIGS Analysis Center is summarized in Tab. 1.
Table 1: Developments of WHUIGS Analysis Center
2011–122012–022012–08
2012–09
2012–10

WHU IGS AC application submitted to IGS
GPS ultra–rapid solutions submitted to ACC, including satellite orbits,
clock errors and ERP parameters
WHU AC officially authorized by IGS, ultra–rapid solutions weighted
in the ACC combination
GPS/GLONASS ultra–rapid products weighted in the ACC combination
GPS/GLONASS rapid solutions submitted to ACC, including satellite orbits,
clock errors and ERPs

2.2 PANDA software
PANDA software package is capable of simultaneously processing various types of measurements 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 determinationof LEO satellite orbits are developed in this software package.
PANDA software package includes two core modules, the orbit integrator and the state
estimator. In the orbit integrator module, Runge–Kutta approach is used to estimate
initials and Adams–Moulton multi–step approach to estimate corrections. Perturbationsof non–spheric earth gravity, earth tide and ocean tide, solar and planet point mass aswell as relativity are modeled by IERS Conventions 2010 (Petit and Luzum, 2010). The
yaw attitude modeling for GLONASS was implemented according the model provided by
ESOC (Dilssner et al., 2011).
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).
In order to speed up the data processing, an efficient approach of removal and recovery ofstation coordinate and ambiguity parameters is employed in the least–squares estimator(Shi et al., 2010). Besides, the ambiguity–fixing can also be performed in network modeor single point mode which would improve the positioning accuracy significantly for WHU
final solutions.

94

3 WHU Analysis Products

3 WHU Analysis Products
3.1 Products
The list of products provided by WHU is summarized in Tab. 2.
Table 2: 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

The WHU rapid GNSS products are provided daily for the previous day which produced
available within 2 hours after the end of the observation day. Both GPS and GLONASS
data are processed simultaneously to produce rapid satellite orbits. About 55 satellites
are included in daily processing. The accuracy of GPS rapid orbits are shown in Fig. 1
and the weighted RMS is about 15 mm.
The WHU ultra–rapid products are based on the combination of the 6–hour normal equation using global hourly IGS data, including satellite orbits, clock errors and ERPs. The
ultra–rapid products consist of a 48–hr orbit file (24 h estimated and 24 h predicted) alongwith a 2–day ERP file (the first day is estimated and the second day is predicted).
The quality of the WHU ultra–rapid products are shown in Fig. 2. The accuracy of theultra–rapid products are 3 cm for the prediction orbit, measured as a WRMS comparedto the IGS ultra–rapid orbits (IGU).

3.2 Processing strategy
The routine processing of WHU is based on a least–squares estimation solution of IGS
station data in RINEX format. And the selection of ground stations depends on theavailability and the past performance of raw data as well as the required time delay
according to the type of products. For the rapid and ultra–rapid solutions, about 120 and
110 stations are used, respectively, which are shown in Fig. 3.

95

Shi et al.: Wuhan University

COD
EMR
ESA

Rapid Orbits (AC solutions compared to IGS Rapid)
50

GFZ(smoothed)

JPL
NGS
SIO
USN

40

Weighted RMS [mm]

WHU
30

20

10

0
1660

1670

1680

1690
1700
Time [GPS weeks]

1710

1720

1730

NOAA NGS, 27.02.2013 17:47 (GMT)

Figure 1: Weighted RMS of WHU rapid orbits.
COU
EMU

Ultra Rapid Orbits (AC solutions compared to IGS Ultra)
200

ESU
GFU

(smoothed)

GOU
JPU
NGU
SIU

Weighted RMS [mm]

150

USU
WHU

100

50

0
1660

1670

1680

1690
1700
Time [GPS weeks]

1710

1720

1730

NOAA NGS, 27.02.2013 18:19 (GMT)

Figure 2: Weighted RMS of WHU ultra–rapid orbits.

96

4 WHU contributions to BeiDou
−120˚

−60˚

0˚

60˚

30˚

BAKE

FLIN
PRDS
HOLB
NANO
DRAO
AMC2
GOLD
HARV
MDO1

KUUJSCH2
VALD
STJO
ALGO
NRC1
BARH
GODZ
BRMU
SCUB

GUAT
MANA

180˚

YAKT

ONSA
ARTU
MORP
WSRT LAMA MOBJ
KOSG
IRKM
BRST WTZR
ULAB
GRAS
ZECK
CHUMURUM
FLRS
CAGZ
NICO
RABT
FUNC
LHAZ
LPAL
HYDE

NKLG
BRFT

TSKB
GMSD

30˚
KOKB
KOKV
MKEA

CUSV

GUUG

NURK

XMIS
COCO

AREQ

0˚
DARW
ALIC

HARB
SUTV

CONZ LPGS

YAR2
NNOR

FALK

−60˚

YSSK

NTUS
DGAV

ISPA

−30˚

60˚
PETS

CHAN

ADIS
KOUR

GLPS

TIXI

NRIL

KIR0

ABMF
BDOS

BOGT

0˚

SCOR
REYK

KELY

IQAL

120˚

NYA1

THU2
YELL

60˚

ASPA
TOW2 KOUC
NRMD

−30˚

SYDN
MOBS
HOB2

AUCK
MQZG
CHTI

MAC1

−60˚

OHI2
PALM
SYOG

MAW1 DAV1

CAS1
MCM4

−120˚

−60˚

0˚

60˚

120˚

180˚

2013 Feb 27 16:18:19

Figure 3: Ground stations used for WHU rapid and ultra–rapid products.

For the IGS submissions the estimated parameters are:• the station coordinates,• the satellite state vectors,• station and satellite clock errors, estimated as time-dependent parameters (one value
for every observation epoch),• the Earth rotation parameters: x and y pole position and rates and length of Day,• the solar radiation pressure parameters with BERN model,• the zero-differenced carrier phase ambiguities for the ionospheric-free linear combination,• the GPS–GLONASS receiver biases (for the GPS/GLONASS combined processing),• the tropospheric zenith delay for every station every 2 hours with north and east
horizontal gradients.

4 WHU contributions to BeiDou
The BeiDou satellite system was initiated on April 13, 2007 with the launch of the first
MEO satellite. At the beginning of October 2012, the first phase had been almost completed. A total of 15 BeiDou navigation satellites have been successfully launched. The
WHU has been processing BeiDou data since 2011 and providing precise BeiDou orbits

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Shi et al.: Wuhan University

Orbit Difference Radial /cm
0

1

2

3

4

5

6

7

8

9

10

11

12

24.4

C01=10.0

GEO

C02=22.1

Radial/cm

18.3

C03=8.8
C04=11.3
C05= 10.0

12.2

6.1

0.0
19.2

IGSO

C06=8.7
C07=7.6

Radial/cm

14.4

C08=7.9
C09=7.4
C10=7.3

9.6

4.8

0.0

MEO

C11=5.7

Radial/cm

6.6

C12=5.5

4.4

2.2

0.0
0

1

2

3

4

5

6

7

8

9

10

11

12

Month

Figure 4: BeiDou orbit overlap statistics of the radial component in 2012 (unit: cm).
Orbit Difference Cross /cm
0

1

2

3

4

5

6

7

8

9

10

11

C02=14.1

27.3

Cross/cm

12

C01=17.1

GEO

C03=15.2
C04=16.3
C05= 21.9

18.2

9.1

0.0
44

IGSO

C06=24.0
C07=22.4

Cross/cm

33

C08=22.9
C09=22.8
C10=19.8

22

11

20
0

MEO

C11=12.7
C12=12.8

Cross/cm

15

10

5

0
0

1

2

3

4

5

6

7

8

9

10

11

12

Month

Figure 5: BeiDou orbit overlap statistics of the cross–track component in 2012 (unit: cm).

98

References
Orbit Difference Along /cm
0

1

2

3

4

5

6

7

8

9

10

11

12

960

C01=318.7

GEO

C02= 83.1

Along/cm

720

C03=194.0
C04=404.4
C05= 86.1

480

240

0

IGSO

60

C06=37.2

Along/cm

C07=32.6
C08=30.6
45

C09=34.8
C10=28.0

30

15

34.3

MEO

C11=22.6

Along/cm

C12=23.0
29.4

24.5

19.6

0

1

2

3

4

5

6

7

8

9

10

11

12

Month

Figure 6: BeiDou orbit overlap statistics of the along–track component in 2012 (unit: cm).

based on the BeiDou Experimental Tracking Network (CETN) which is built by WHU
since this time (Shi et al., 2012).
As no BeiDou precise satellite orbits are available up to date, overlapping arcs comparison is used to analyze the accuracy of satellite orbits estimated by WHU. The monthly
RMS values of the differences in the radial, cross–track and along–track component for
GEO/IGSO/MEO satellites are shown in Fig. 4 ∼ Fig. 6, respectively. Results show that
the RMS of radial component is better than 10 cm and the cross–track is better than
20 cm.

References
Dilssner, F., T. Springer, G. Gienger, and J. Dow. The GLONASS-M satellite yaw-attitude
model. Advances in Space Research, 47(1):160–171, 2011.
Liu, J. and M. Ge. PANDA software and its preliminary result of positioning and orbit
determination. Journal of Natural Sciences, 8(2):603–609, 2003.
Petit, G. and B. Luzum. IERS Conventions (2010). IERS Technical Note (36). Verlag desBundesamtes für Kartographie und Geodäsie, Frankfurt am Main, 2010.
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.

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Shi et al.: Wuhan University
Shi, C., Q.L. Zhao, M. Li, W.M. Tang, Z.G. Hu, Y.D. Lou, H.P. Zhang, X.J. Niu, andJ.N. Liu. Precise orbit determination of Beidou Satellites with precise positioning.
Sci.China-Earth Sci., 55(7):1079–1086, 2012.

100

EUREF Permanent Network
C. Bruyninx1 , H. Habrich2 , A. Kenyeres3 ,W. Söhne2 , G. Stangl4 , C. Völksen5
1
2
3
4
5

Royal Observatory of Belgium (ROB), Brussels, Belgium
E–mail: C.Bruyninx@oma.be
Bundesamt für Kartographie und Geodäsie (BKG), Frankfurt am Main, Germany
FOMI Satellite Geodetic Observatory, Budapest, Hungary
Institute for Space Research, Graz, Austria
Bavarian Academy of Science and Humanities, Munich, Germany

1 Introduction
The IAG (International Association of Geodesy) Regional Reference Frame sub–commission for Europe, EUREF, is responsible for defining, providing access and maintaining
the European Terrestrial Reference System (ETRS89 Bruyninx et al., 2009). The EUREF
key infrastructures are the EUREF Permanent GNSS Network (EPN) and the United
European Levelling Network (UELN). The EPN is a network of continuously operating
GNSS reference stations maintained on a voluntary basis by EUREF members. Its primary purpose is to provide access to the ETRS89 by making publicly available the GNSS
tracking data as well as the precise coordinates of all EPN stations. The EPN cooperates
closely with the International GNSS Service (IGS, Dow et al., 2009); EUREF members
are participating to the IGS Real–Time Pilot Project, the IGS GNSS Working Group,
the IGS Antenna Calibration Working Group, the Troposphere Working Group, the IGS
Multi GNSS Experiment (MGEX), and the IGS Infrastructure Committee.
The EUREF Technical Working Group (TWG) defines the general policy of the EPN
following proposals by the EPN Coordination Group. This Coordination Group consistsof the Network Coordinator (managing the EPN Central Bureau), Data Flow Coordinator,
Analysis Coordinator, Reference Frame Coordinator, Troposphere Coordinator, Chair of
the Real–time Analysis project, and Chair of the reprocessing project. The EPN Reference
Frame coordinator is a new position created by the EUREF TWG at its 2012 spring
meeting. He is responsible for generating regularly an updated long–term EPN positionand velocity product, the classification/categorization of EPN stations according to their
quality and the densification of the EPN using solutions from national permanent GNSS
networks (see Kenyeres, 2012a; Kenyeres et al., 2012).

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2 Tracking Network
2.1 New Stations
By the end of 2012, the EPN network consisted of 244 continuously operating GNSS
reference stations (Figure 1) from which 34% also belong to the IGS. Before inclusion in the
EPN, the Central Bureau checks the data quality, meta–data, data availability and latency,
and the availability of absolute antenna calibrations for the proposed station. As soon asa station fulfils all requirements, the station is included in the EPN. Data communication
problems, influencing the reliable upload to the EPN data centres (regional and local ones)
is one of the main reasons delaying the integration of a new station in the EPN. However,almost all proposed stations are accepted in the EPN within six months after their initial
proposal. Interested station managers can check EPN guidelines for a proposed station to
become an EPN site at http://www.epncb.oma.be/_networkdata/proposed.php.
Five new stations were integrated in the EPN network in 2012: BRUX, MELI, RIO1,
SUR4, and TOR2. They are indicated with triangles in Figure 1. More details areprovided in Table 1. Four of them are replacements of decommissioned EPN stations(mostly due to construction work near the antenna).

2013 Jan 16 11:22:16

Figure 1: EPN tracking stations, status Dec. 2012.
network in 2012.

102

K indicate new stations included in the2 Tracking Network
Table 1: New stations included in the EPN in 2012.

4Char–ID

Location

BRUX
MELI
RIO1
SUR4
TOR2

Brussels, Belgium
Melilla, Spain
Logrono, Spain
Tallinn, EstoniaTõravere, Estonia

Replacement
or New
BRUS
new
RIOJ
SUUR
TORA

Sat. Tracking

Antenna Calibration usedin EPN analysis

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

Individual from Univ. Bonn
Individual from GEO++
Individual from GEO++
Type mean from IGS
Type mean from IGS

2.2 Multi–GNSS Tracking
All new stations added to the EPN in 2012 are equipped with GPS/GLONASS tracking equipment, bringing the percentage of the EPN stations providing GPS+GLONASS
data to 68%. In addition, 67 EPN stations (Figure 2) operate equipment that is certified“Galileo–ready”, but presently only 25 of them upload RINEX v3 data including Galileo
observations to data centre maintained by the BKG. In addition, 27 of the 29 new antennas/radomes (new stations or replacements at existing stations) introduced in the EPN
during 2012 are already capable to track new signals from multiple GNSS and will not
require any additional hardware upgrade in the near future.
Already today 75 EPN stations have the capability of tracking GPS L5, but only 32of them are actually providing RINEX v2.11 data including L5 (see Figure 3). Station
managers have been reluctant to activate L5 tracking because of possible conflicts with
the national RTK services they provide.

http://www.epncb.oma.be/2013 Jan 16 13:15:34

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

K

http://www.epncb.oma.be/2013 Jan 16 13:36:47

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

K

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Bruyninx et al.: EUREF Permanent Network

2.3 Antenna Calibration Models
In addition to the type mean antenna calibrations, the EPN uses since November 2006
the original individual antenna calibrations which are linked to a specific antenna/radome
type and antenna serial number. They can be considered as the best possible calibration
for a specific antenna/radome combination. Historically, 81 individual calibrations areavailable within the EPN. The majority of new antennas introduced in the EPN (newstations or antenna replacements) have now individual antenna calibrations. The antenna
calibration file used within the EPN (ftp://epncb.oma.be/pub/station/general/epn_
08.atx) contains the individual antenna calibrations complemented with the type meancalibrations from the IGS. Moreover, the original calibration files, as provided by thecalibration agencies (including for some stations calibrations on the Galileo frequencies)
are also available from the EPN CB, e.g. http://www.epncb.oma.be/_networkdata/siteinfo4onestation.php?station=BRUX) .
In the end of 2012, individual calibrations were used at 60 EPN stations amongst which
18 (ANKR, BRUX, BUCU, BZRG, GANP, HOFN, METS, NICO, ORID, PENC, POTS,
REYK, SASS, SOFI, WARN, WROC, WTZR, and ZIM2) are also belonging to the IGS.
Consequently, due to the usage of resp. individual and type mean calibrations for thesestations in the EPN and IGS, the EPN and IGS analysis is not consistent. Inconsistencies
are generally below the 2 mm level. However, for the up–component, SOFI, SASS andWTZR have differences of resp. −1 cm, 6 mm, and 4 mm.

3 Data Analysis
3.1 Routine Processing
A total of 17 EPN Local Analysis Centres (LACs) submit weekly free–network solutions(SINEX format) for an EPN subnetwork to the EPN Analysis Coordinator. The majorityof the EPN analysis centres use the Bernese V5.0 software. The EPN Analysis Coordinator
combines the EPN subnetwork solutions into the weekly combined EPN solution. This
weekly solution is tied to the most recent IGS realisation of the ITRS and is used as input
for the EPN Reference Frame Coordinator who computes a multi–year EPN solution,
updated each 15 weeks, and providing up–to–date EPN positions and velocities allowing
to categorize EPN stations as:• Class A stations with positions at 1 cm accuracy at all epochs of the time span of
the used observations;• Class B stations with positions at 1 cm accuracy at the epoch of minimal varianceof each station.
Following the EUREF “Guidelines for EUREF Densifications” (Bruyninx, 2010), only ClassA EPN stations can be used for densifications of the ETRS89. In 2012, one EUREF
densification campaign, EUREF BE/2011, has been validated by the TWG.
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3 Data Analysis
In addition, a smaller group of the LACs is also providing a rapid solution that is provided
less than 24 hours after the last observations to the EPN Combination Centre. Here, thedifferent solutions are combined into an EPN rapid solution.

3.2 EPN Reprocessing
In addition to the routine EPN analysis described above, the EPN also finalized it first
reprocessing in 2012 (EPN–REPRO1, Völksen, 2011) including the EPN data from GPS
week 834 till 1408 using the software packages Bernese v5.0 (Dach et al., 2007), GAMIT(Herring et al., 2007) and GIPSY/OASIS II (Blewitt, 2008). This reprocessing used the
epn_05.atx antenna calibration model (EPN individual calibrations complemented with
igs05.atx type mean calibrations) and IGS orbits from the first IGS reprocessing effort
or directly from one of analysis centers contributing to the IGS reprocessing. The EPN
reprocessing was based on the data available from the historical data EPN center at
EPN CB/ROB (ftp://ftp.epncb.oma.be/pub/obs/). This data center has been setup
specifically in support of EPN reprocessing activities. The RINEX header info of all files
in the historical data center is corrected following the station log and for that reason
the data are delayed with a few months compared to the operational data centers. The
historical data center does not only contain data from an EPN station for the period it is(has been) included in the EPN, but also contains pre–EPN data for some stations. These
data were picked up by the EPN Local Analysis Centers for their reprocessing. Based on
their results, some of the pre–EPN data were identified as useful. This information willbe the basis for contacting station managers with a proposal to advance the official startof the station within the EPN and consequently extend the quality checks and metadata
checks at the EPN CB for that station.
The EPN–REPRO1 weekly combined SINEX product has been included into the official
ITRF2008 and IGS08 densifications.
Beside position time series, zenith total delay (ZTD) parameters are available from EPN–
REPRO1. Thanks to EUREF’s Memorandum of Understanding with EUMETNET —the organization of the European National Meteorological Services — ZTD time series
derived from radiosonde data of several stations in the vicinity of EPN stations is alsoavailable back to 1996. Moreover, VLBI combined ZTD solutions provided by EGVA, theEuropean VLBI Group for Geodesy and Astrometry, for nine co–located stations could be
used for comparison and are available on the EPN station–related webpage.
The EPN LACs are prepared to start another reprocessing campaign (EPN–REPRO2).
So far this activity has been delayed due to unavailability of reprocessed orbits and ERPs
in the IGS08. But the situation is currently changing since reprocessed orbits and ERPs
are slowly becoming available like products from the Center for Orbit Determination in
Europe (CODE) and the Jet Propulsion Laboratory (JPL).

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Bruyninx et al.: EUREF Permanent Network

4 Densification of the ITRF/IGS08
An intermediate EPN densification solution of the ITRF2008 was generated based on theweekly EPN–REPRO1 results (GPS week 834–1408) and the routine EPN weekly solutions(GPS week 1409–1631) both computed using the epn_05.atx antenna model (Kenyeres,2012a,b). This solution was however never provided to the EUREF user community
because it was not consistent with the recent epn_08.atx/igs08.atx calibration model.
To generate a solution consistent with epn_08.atx, weekly EPN solutions before GPS
week 1632 had to be corrected to take into account the position offset caused by theswitch from epn_05.atx to epn_08.atx model. Similar to what was done by (Rebischunget al., 2012) for the IGS, a PPP (Precise Point Positioning) analysis was used within
the EPN to compute the position offsets for the full hisotrical EPN data set (Baire etal., 2011). Of course, no correction is necessary for stations with individual calibrations.
The corrected SINEX files, together with the routinely generated weekly EPN SINEX
solutions (from GPS week 1632 on) were used as input for the EPN densification solution
IGS08_C1680 which was expressed in both IGS08 and ETRF2000. Although the IGS andEPN dataset and processing strategies are slightly different the global ITRF/IGS and theirregional densification solutions have shown perfect agreement. The densification solution
is updated every 15 weeks.
The related files can be downloaded from the ftp://epncb.oma.be/pub/station/
coordinates/EPN/ and include a discontinuity table and associated residual position timeseries. More details can be found in http://www.epncb.oma.be/_productsservices/
coordinates/.

5 Densification of the EPN
To take advantage of the many national agencies that routinely analyze the data fromnational GNSS networks consisting of stations not all included in the EPN, EUREF decided in 2010 to initiate a densification of the EPN. The main target of this work beyond
the homogenization of the national networks is to realize a dense continental–scale velocity field. This product will support the better realization of the ETRS89 and it will
be an important input for the IAG WG on “Integration of Dense Velocity Fields in the
ITRF”. In the meantime several countries (Poland, Estonia, Latvia, Slovakia, Hungary,
Austria, Bulgaria, Czech Republic, France and Italy) provide weekly SINEX solutions to
the EPN Reference Frame Coordinator. These solutions are combined with the weekly
EPN solution and then stacked to obtain consistent cumulative position/velocity solutions
for a densified EPN network. The expected number of stations will definitely exceed 1000.
Thanks to EUREF’s Memorandum of Understanding with CEGRN (Central European
GPS Geodynamic Reference Network), also weekly permanent and bi–annual campaign
CEGRN SINEX solutions were submitted and included. This work is still in progress (seeKenyeres et al., 2012).
106

7 Conclusions

6 EPN Real–time Analysis Project
The EPN Project on “Real–time Analysis” focuses on the processing of the EPN real–time data to derive and disseminate real–time GNSS products (http://www.epncb.oma.
be/_organisation/projects/RT_analysis/). The EPN regional broadcaster at BKG(http://www.euref-ip.net) is broadcasting satellite orbits in the ETRS89 (realization
ETRF2000). Based on these orbits users can directly derive real–time coordinates referred
to ETRS89 at the level of a few decimetres (more details are given in Söhne and Weber,2011).
One aim of the project is to increase the reliability of the EPN real–time data flow andto minimize the possibility of regional broadcaster’s outage. For this purpose, two additional regional broadcasters have been put in operation, one at ASI (Italian Space
Agency, http://euref-ip.asi.it/ and one at ROB (Royal Observatory of Belgium,
http://www.euref-ip.be/). Based on the existence of three regional broadcasters, several stations started uploading their data in parallel to all of the broadcasters.

7 Conclusions
The EPN tracking network is becoming a real multi–GNSS tracking network with a totalof 68% of the stations tracking GPS and GLONASS signals. In addition, also the large
majority of the new antenna/radome pairs introduced in the EPN over the last year iscapable of tracking multiple GNSS.
The technical implementation of EPN real–time data flow has been realized in the past
years. Still, with respect to their analysis, the achieved level of accuracy is yet not competitive to the classical post analysis. But improved software, models and algorithms mightclose the gap between the classical post analysis and the real–time analysis in the years
to come.
With the inclusion of pre–EPN data in the EPN–REPRO1 activity, the stations withvaluable pre–EPN data can now be identified and included in the EPN. In addition, acomplete reprocessing of all historical EPN data has allowed computing improved station
positions and velocities that can be used for national densifications of the ETRS89.
More information on the EPN can be found at http://www.epncb.oma.be/.

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Bruyninx et al.: EUREF Permanent Network

References
Baire, Q., E. Pottiaux, C. Bruyninx, P. Defraigne, J. Legrand, and N. Bergeot. Comparisonof receiver antenna calibration models used in the EPN. Presented at EUREF 2011
symposium, 23–27. May 2011, Chisinau, Moldova, 2011.
Blewitt, G. Fixed point theorems of GPS carrier phase ambiguity resolution and their application to massive network processing: Ambizap. J. Geophys. Res., Vol. 113, B12410,
2008. doi: 10.1029/2008JB005736 .
Bruyninx, C., Z. Altamimi, C. Boucher, E. Brockmann, A. Caporali, W. Gurtner,
H. Habrich, H. Hornik, J. Ihde, A. Kenyeres, J. Mäkinen, G. Stangl, H. van der Marel,
J. Simek, W. Söhne, J. A. Torres, and G. Weber. The European Reference Frame: Maintenance and Products. Geodetic Reference Frames, IAG Symposia Series, Springer, Vol.
134:131–136, doi: 10.1007/978-3-642-00860-3_20 .
Bruyninx, C., Q. Baire, J. Legrand, and F. Roosbeek. The EUREF Permanent Network(EPN): Recent Developments and Key Issues. Presented at EUREF 2011 symposium,
23–27. May 2011, Chisinau, Moldova, 2011.
Bruyninx, C., Z. Altamimi, A. Caporali, A. Kenyeres, M. Lidberg, G. Stangl, and J. A. Torres. Guidelines for EUREF Densifications, 2010. ftp://epncb.oma.be/pub/general/
Guidelines_for_EUREF_Densifications.pdf .
Dach, R., G. Beutler, H. Bock, P. Fridez, A. Gäde, U. Hugentobler, A. Jäggi, M. Meindl,
L. Mervart, L. Prange, S. Schaer, T. Springer, C. Urschl, and P. Walser. Bernese GPS
Software Version 5.0. Astronomical Institute, University of Bern, Bern, Switzerland,jan 2007. URL http://www.bernese.unibe.ch/docs50/DOCU50.pdf. User manual.
Dow, J. M., R. Neilan, and C. Rizos. The International GNSS Service in a changing
landscape of Global Navigation Satellite Systems. Journal of Geodesy, 83(3–4):3191–
198, 2009. doi: 10.1007/s00190-008-0300-3 .
Herring, T. A., R. W. King, and S. C. McClusky. Introduction to GAMIT/GLOBK, Release 10.3, Mass. Instit. of Tech., Cambridge, 2007
Kenyeres, A. The implementation of IGS08 in the EPN — ETRS89 maintenance products. ftp://epncb.oma.be/pub/station/coord/EPN/IGS08_densification_V4.pdf,
2012a.
Kenyeres, A. EPN densification of the ITRF2008/IGS08. Presented at EUREF 2012
symposium, 06–06. June 2012, Saint–Mandé, France, 2012b.
Kenyeres, A., T. Jambor, A. Caporali, B. Drosčak, B. Garayt, I. Georgiev, I. Jumare,J. Nagl, P. Pihlak, M. Ryczywolski, and G. Stangl. Integration of the EPN and thedense national weekly SINEX solutions. Presented at EUREF 2012 symposium, 06–06.
June 2012, Saint–Mandé, France, 2012b.

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References
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 .
Söhne, W. and G. Weber. Real–time Positioning using EUREF and IGS resources. Presented at EUREF 2011 symposium, 23–27. May 2011, Chisinau, Moldova, 2011.
Völksen, C. An Update on the EPN Reprocessing Project: Current Achievement andStatus. Presented at EUREF 2011 symposium, 23–27. May 2011, Chisinau, Moldova,
2011.

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110

IGS Regional Network Associate Analysis Centre
for SIRGAS (IGS RNAAC SIR)
L. Sánchez
Deutsches Geodätisches Forschungsinstitut (DGFI)
Alfons–Goppel–Str. 11, D–80539 Munich, Germanye–mail: sanchez@dgfi.badw.de

SIRGAS was initially realized by two GPS campaigns, one in 1995 (SIRGAS95) with58 stations, and one in 2000 (SIRGAS2000) with 184 stations. SIRGAS95 included only
10 continuously operating GPS stations, while SIRGAS2000 comprised 29 . During thelast decade, most of the Latin American countries decided to qualify their national reference frames by installing more and more permanent GPS (now GNSS) stations, withthe main requirement of integrating them into the continental reference frame consistently.
According to this, the present realisation of SIRGAS is a network with more than 300 continuously operating GNSS stations, 59 of which formally belong to the IGS global networkand other 40 are included in the IGS reprocessing campaign 2 to improve the IGS station
coverage in the Latin American and Caribbean regions. The weekly processing of the continuously observing GNSS SIRGAS stations started in June 1996 under the responsibilityof the IGS Regional Network Associate Analysis Centre for SIRGAS (IGS RNAAC SIR)
operated by the Deutsches Geodätisches Forschungsinstitut (DGFI). Due to the increasing
number of stations, it was necessary to involve more processing centres to guarantee a sustainable, reliable and redundant computation of the entire SIRGAS network. In this way,
the weekly processing of the SIRGAS Reference Frame is now a shared activity between
10 SIRGAS Analysis Centres, 9 of them under the responsibility of Latin American organisations. This report describes strategy and quality of the SIRGAS products generated
during the year 2012.

1 Introduction
The SIRGAS Reference Frame at present comprises 300 continuously operating GNSS
stations (Fig. 1). It is continuously processed on a weekly basis to generate (Sánchez etal., 2012b):

111

Sanches: RNAAC SIRGAS

Figure 1: SIRGAS Reference Frame (status 2013–01–14).

112

2 Routine analysis of the SIRGAS Reference Frame
1. 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 delivered weekly to the IGS in SINEX format to be combined
together with those generated by the other IGS Global and Regional Analysis Centres. They are named sirwwww7.snx (wwww stands for the GPS week);
2. 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).
3. Multi–year solutions providing station positions and 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 number of the cumulative solutions computed in one year).
Due to the large number of stations, the analysis strategy of the SIRGAS Reference Frameis based on the combination of individual solutions including different networks (Brunini
et al., 2012): One core network with 120 stations distributed over the whole continent,and different densification sub-networks distributed regionally on the northern, middle,
and southern part of the continent (Fig. 1). These sub-networks (i.e. clusters) are individually processed by 10 SIRGAS Analysis Centres: the core network is computed by DGFI
(responsible for the IGS RNAAC SIR), the other sub–networks by the SIRGAS Local
Processing Centres: CEPGE (Ecuador), CIMA (Argentina), CPAGS-LUZ (Venezuela),
IBGE (Brazil), IGAC (Colombia), IGM (Chile), IGN (Argentina), INEGI (Mexico) andSGM (Uruguay). The weekly combination of the individual solutions is carried out by
the SIRGAS Combination Centres: DGFI and IBGE. The distribution of the SIRGAS
stations within the individual clusters guarantees that each station is included in threesolutions.

2 Routine analysis of the SIRGAS Reference Frame
The different SIRGAS Analysis Centres follow the same standards for the computationof loosely constrained weekly solutions. INEGI (Mexico) and IGN (Argentina) work withthe software GAMIT/GLOBK (Herring et al., 2010), all the other 8 Processing centres
use the Bernese GPS Software V. 5.0 (Dach et al., 2007). The main characteristics of theanalysis strategy are (e.g. Costa et al., 2012a; Sánchez et al., 2012a):• Elevation mask and data sampling rate are set to 3◦ and 30 s, respectively.
• Absolute calibration values for the antenna phase centre corrections published by the
IGS are applied (http://www.igs.org/igscb/station/general/pcv_archive/).

113

Sanches: RNAAC SIRGAS• Satellite orbits, satellite clock offsets, and Earth orientation parameters are fixed tothe combined IGS weekly solutions (Dow et al., 2009, http://www.igs.org/igscb/
product/).
• Solution of phase ambiguities for L1 and L2.
• Reduction of periodic site movements due to ocean tide loading according to the
FES2004 ocean tide model (Letellier, 2004). The corresponding values are provided
by M. S. Bos and H.-G. Scherneck at http://holt.oso.chalmers.se/loading/ .
• The Niell (1996) dry mapping function is applied to map the a priori zenith delay(dry part), which is modelled using the model from Saastamoinen (1973). The
wet part of the zenith delay is estimated at a 2 hour intervals within the network
adjustment and it is mapped using the Niell wet mapping function.
• Daily free normal equations are computed by applying the double differences strategy. They are afterwards combined for generating a loosely constrained weekly solution for station positions (all station coordinates are loosely constrained to ±1 m).
Stations with large residuals in the weekly combination (more than ±20 mm in theN–E component, and more than ±30 mm in the height component) are reduced fromthe normal equations.
• The individual loosely constrained solutions are made available for their combination in SINEX format. They are identified following the IGS nomenclature, i.e.
cccwwww7.snx: ccc stands for the abbreviation of the processing centre and wwww
for the GPS week. These solutions are available at ftp://ftp.sirgas.org/pub/
gps/SIRGAS/ .
At the moment, SIRGAS is aligning its computation procedures to the new standards
released by the IGS for the reprocessing campaign 2 . The different SIRGAS Analysis
Centres are updating the corresponding analysis software and it is expected to start the
reprocessing of the SIRGAS Reference Frame by May 2013. In the same way, the computation (updating) of multi-year solutions is stopped until the entire network is totally
reprocessed with respect to the IGS08 (IGb08) Reference Frame (Sánchez, 2012).

3 Weekly solutions of the SIRGAS Reference Frame
The loosely constrained weekly solutions delivered by the individual SIRGAS Analysis
Centres are integrated in a unified solution by the SIRGAS Combination Centres: DGFIand IBGE. The DGFI (i.e. IGS RNAAC SIR) combination strategy corresponds to (Fig. 2,
Sánchez, 2012):
1. Individual solutions are reviewed/corrected for possible format problems, station
inconsistencies, utilization of erroneous equipment, etc.

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3 Weekly solutions of the SIRGAS Reference Frame

Figure 2: Combination of the weekly solutions delivered by the SIRGAS Analysis Centres.

2. Constraints included in the delivered normal equations are removed. In this way,
unconstrained (condition free, non–deformed) normal equations with correct station
information are available for combination.
3. Individual normal equations are separately solved with respect to IGS Reference
Stations included in the SIRGAS Frame (Fig. 1). In this case, the IGS Reference
Station positions are constrained to the IGS weekly coordinates (igsyyPwwww.snx).
4. Station positions obtained in 3 for each cluster are compared with the IGS weekly
values and with each other to identify possible outliers.
5. Stations with large residuals (more than ±10 mm in the north or east components,and more than ±20 mm in the height component) are reduced from the normal
equations. Steps 3, 4, and 5 are iterative.
6. Variances obtained in the final computation of step 3 are analysed to estimate scaling
factors for relative weighting of the individual solutions.
7. Once inconsistencies and outliers are reduced from the individual free normal equations, a combination for a loosely constrained weekly solution for station positions

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Sanches: RNAAC SIRGAS(all station coordinates constrained to ±1 m) is computed. This solution is submitted to IGS for the global polyhedron and stored to be included in the next multi-year
solution of the SIRGAS Reference Frame.
8. Finally, a weekly solution aligned to the ITRF is computed. As in step 3, thegeodetic datum is defined by constraining the coordinates of the reference stations
to the positions calculated within the IGS weekly combinations (igsyyPwwww.snx).
The applied constraints guarantee that the coordinates of the reference stations do
not change by more than ±1.5 mm within the SIRGAS adjustment.
9. The accumulation and solution of the normal equations are carried out with theBernese GPS Software V.5.0 (Dach et al., 2007).
10. Resulting files of this procedure are:
SIRwwww7.SNX: SINEX file of the loosely constrained weekly combination.
SIRwwww7.SUM: Report of weekly combination.
siryyPwwww.snx: SINEX file for the weekly combination aligned to the IGS Frame.
siryyPwwww.crd: Final SIRGAS-CON station positions for week wwww.
The loosely constrained combinations as well as the weekly SIRGAS–CON coordinates areavailable at ftp://ftp.sirgas.org/pub/gps/SIRGAS/ or at http://www.sirgas.org .

4 Quality control of the SIRGAS Reference Frame weekly
solutions
The generation of the weekly SIRGAS products (i.e. loosely constrained combinations andstation positions aligned to the IGS reference frame) at DGFI includes a quality control at
two levels (Sánchez et al., 2012a): Firstly, the individual solutions delivered by the SIRGAS
Processing Centres are analysed to establish their quality and consistency. This includes
a survey about date of delivery, processed stations, log file observance, etc. Once theindividual solutions are reviewed and free of inconsistencies, their combination is carriedout by applying the procedure summarized in Sect. 3 . Then, the second quality control
concentrates on the results of this combination. Here, the main objective is to ascertain
the accuracy and reliability of the weekly solutions for the entire SIRGAS network.

4.1 Quality control of the individual solutions
The consistency between the different individual solutions is evaluated by means of:• Mean standard deviations of station positions after solving the individual solutions
with respect to the IGS Reference Frame (Fig. 3). These values represent the formal
errors of the individual solutions.

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4 Quality control of the SIRGAS Reference Frame weekly solutions

Figure 3: Mean standard deviations [mm] of station positions after solving the individual solutions and their combination with respect to the IGS Reference Frame (Time span:
GPS weeks 1641–1705).

Figure 4: Mean RMS values for the weekly repeatability of station positions in the solutionsdelivered by the SIRGAS Analysis Centres (Time span: GPS weeks 1641–1705).

Figure 5: Mean RMS values after comparing the station positions between the individual solutions delivered by the SIRGAS Analysis Centres and the IGS weekly solutions (Timespan: GPS weeks 1641–1705).

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Sanches: RNAAC SIRGAS• Weekly repeatability of station positions for each Processing Centre to assess theindividual precision of the weekly solutions (Fig. 4).
• Comparison with the IGS weekly coordinates for common stations to estimate thereliability of the individual solutions (Fig. 5).
In general, the RMS values derived from the station position time series and with respect tothe IGS weekly coordinates indicate that the accuracy of the individual solutions is about±2 mm in the North and the East, and ±5 mm in the height (Figs. 4, 5). Regarding thestandard deviations (Fig. 3) obtained after solving the individual normal equations withrespect to the IGS Reference Frame, one can observe that Processing Centres applying
the Bernese GPS Software present values of ≈ ±1.6 mm, while Processing Centres using
GAMIT/GLOBK have values of about 2.0 mm.

4.2 Evaluation of combined (final) SIRGAS solutions
The quality evaluation of the weekly station positions computed for the SIRGAS Reference
Frame is performed according to the following criteria:• Mean standard deviation for station positions after aligning the network to the IGS
Reference Frame indicates the formal error of the final combination (Fig. 3);• The weekly coordinate repeatability after combining the individual solutions provides information about the internal consistency of the combined network (Fig. 6);• Time series analysis for station coordinates allows to determine the compatibility of
the combined solutions from week to week (Fig. 6);• Comparison with the IGS weekly coordinates (igsyyPwwww.snx) indicates the consistency with the IGS global network (Fig. 6);• Comparison with the IBGE weekly combination (ibgyyPwwww.snx) fulfils the required redundancy to generate the final SIRGAS products (Fig. 6).

Figure 6: Quality control of the weekly station positions computed for the SIRGAS Reference
Frame (mean RMS values for the period covered by the GPS weeks 1641 to 1705).

118

References
The mean standard deviation of the combined solutions agrees quite well with those computed for the individual contributions (Fig. 3), i.e. the quality of the individual solutions
is maintained and their combination does not deform or damage the internal accuracyof the entire SIRGAS network. The coordinate repeatability in the weekly combinations
provides an estimate of the accuracy (internal consistency) of the weekly combinationsof about ±1.4 mm in the horizontal component and about ±3.6 mm in the vertical one.
The RMS values derived from the time series for station positions and with respect to the
IGS weekly coordinates indicate that the reliability of the network (external precision) is
about ±2.0 mm in the horizontal position and ±4.0 mm in the height. The differences withrespect to the IBGE weekly combinations are within the expected level (less than 0.5 mm).
Costa et al. (2012b) present a description about the IBGE combination strategy.

Acknowledgments
The operational infrastructure and results described in this report are possible thanks tothe active participation of many Latin American and Caribbean colleagues, who not only
make the measurements of the stations available, but also operate SIRGAS Analysis Centres 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 http://www.sirgas.org .

References
Brunini, C., L. Sánchez, H. Drewes, S. Costa, V. Mackern, W. Martínez, W. Seemüller,
and A. da Silva. Improved Analysis Strategy and Accessibility of the SIRGAS Reference
Frame. In: Kenyon S., M. C. Pacino, U. Marti (Eds.), Geodesy for Planet Earth, IAG
Symposia, 136: 3–10, 2012. doi: 10.1007/978-3-642-20338-1_1.
Costa, S. M. A., A. L. Silva, and J. A. Vaz. Processing Evaluation of SIRGAS-CON
Network by IBGE Analysis Center. In: Kenyon S., M. C. Pacino, U. Marti (Eds.),
Geodesy for Planet Earth, IAG Symposia, 136: 859–867, 2012a. doi: 10.1007/
978-3-642-20338-1_108.
Costa, S. M. A., A. L. Silva, and J. A. Vaz. Report on the SIRGAS–CON Combined
Solution by IBGE Analysis Center. In: Kenyon S., M. C. Pacino, U. Marti (Eds.),
Geodesy for Planet Earth, IAG Symposia, 136: 853–858, 2012b. doi: 10.1007/
978-3-642-20338-1_107.

119Sanches: RNAAC SIRGAS
Dach, R., G. Beutler, H. Bock, P. Fridez, A. Gäde, U. Hugentobler, A. Jäggi, M. Meindl,
L. Mervart, L. Prange, S. Schaer, T. Springer, C. Urschl, and P. Walser. Bernese GPS
Software Version 5.0. Astronomical Institute, University of Bern, Bern, Switzerland,jan 2007. URL http://www.bernese.unibe.ch/docs50/DOCU50.pdf. User manual.
Dow, J. M., R. Neilan, and C. Rizos. The International GNSS Service in a changing
landscape of Global Navigation Satellite Systems. Journal of Geodesy, 83(3–4):3191–
198, 2009. doi: 10.1007/s00190-008-0300-3 .
Herring, T. A., R. W. King, and S. C. McClusky. Introduction to GAMIT/GLOBK. Department of Earth, Atmospheric and Planetary Sciences. Massachusetts Institute ofTechnology, 48 p., 2010.
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, 237 p., 2004.
Niell, A. E. Global Mapping Functions for the Atmosphere Delay at Radio Wavelengths.
J. Geophys. Res., 101(B2):3227–3246, 1996.
Saastamoinen, J. Contribution to the theory of atmospheric refraction. Part II: Refraction
corrections in satellite geodesy. Bull. Géod. (107):13–34, 1973.
Sánchez, L., W. Seemüller, and M. Seitz. Combination of the Weekly Solutions Delivered by the SIRGAS Processing Centres for the SIRGAS–CON Reference Frame. In:
Kenyon S., M. C. Pacino, U. Marti (Eds.), Geodesy for Planet Earth, IAG Symposia,
136: 845–852, 2012a. doi: 10.1007/978-3-642-20338-1_106.
Sánchez, L., W. Seemüller, H. Drewes, L. Mateo, G. González, A. da Silva, J. Pampillón,
W. Martínez, V. Cioce, D. Cisneros, and S. Cimbaro. Long–term stability of the SIRGAS
Reference Frame and episodic station movements caused by the seismic activity in the
SIRGAS region. Proceedings of the IAG Symposium REFAG2010, Springer (in press),
2012b.
Sánchez L. IGS Regional Network Associate Analysis Centre for SIRGAS (IGS RNAAC
SIR). Report of activities 2011. In M. Meindl, R. Dach, and Y. Jean, editors, IGS 2011
Technical Reports, IGS Central Bureau, pages 107–115, 2012.

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Part III

Data Centers

121

Infrastructure Committee Report 2012
I. Romero
ESA/ESOC, Navigation Support Office, HSO–GN, Darmstadt, Germany

1 Introduction
The Infrastructure Committee (IC) was established in March 2009 and it is set with thetask of studying and advising on infrastructure issues to the IGS Governing Board and the
IGS Network Coordinator (NC). The latest status and recent progress of the Committee
is detailed below for 2012.
Chair:
Ignacio (Nacho) Romero, ESA/ESOC, Ignacio.Romero@esa.int
Membership:
Current Members appointed 3 April, 2011 for terms up to Dec 2013:• Carine Bruyninx (ROB)• Lou Estey (UNAVCO)• Gary Johnston (GA)
• Ignacio (Nacho) Romero — Chairman — (ESA/ESOC)• Mike Schmidt (NRCan)• Georg Weber (BKG)
Ex–officio Members:• Steve Fisher — Central Bureau• Jake Griffiths — Analysis Center Coordinator• Mark Caissy — Real time Working Group Chair• Bruno Garayt — Reference Frame Coordinator• Carey Noll — Data Center Working Group Chair• Ken Senior — Clock Products Coordinator123Romero: Infrastructure Committee

2 Activities in 2012
During 2012 the Infrastructure Committee has been involved in many different activities
as detailed in the sections below.

2.1 IGS Site Guidelines
The IC has continued the IGS Site Guidelines refinement with the IGS Central Bureau.
The guidelines have been presented at the Governing Board meeting in July 2012, andthey are waiting for publication by the IGS Central Bureau after further review by the
Real–Time Pilot Project (RTPP), to adapt the real–time station guidelines to the latest
know–how.

2.2 IGS 2012 Workshop Participation
Helped and supported the IGS Workshop in July 2012 with two presentations (“IGS Network Challenges” and “RINEX Working Group report”, the latter on behalf of the RTPP),
plus presented an IC poster on the un–calibrated Dome test campaign, and run a RINEX
technical meeting and an IC forum.

2.3 Radome–Off Test Campaign
The IC has continued to support the test campaign to assess the impact of un–calibrated
domes at co–located sites (together with IGS Central Bureau, Analysis Center Coordinator, Reference Frame Working Group and Antenna Working Group).
Table 1: Participating Radome–off Test Campaign (2011–2013)
Station
CRO1
TSKB
TSK2
AREQ
FAIR
YAR2
GODE
MDO1

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RemovalRe–installation

01–Apr–2011 24–Jun–2011
01– Jul –2011 30–Aug–2011
01– Jul –2011 30–Aug–2011
19–Aug–2011 03– Feb –2012
28–Apr–2012 04–Aug–2012
28–Apr–2012 28– Sep –2012
06– Jul –2012 30– Jan –2013
On–going

2 Activities in 2012

Figure 1: Co–located stations with uncalibrated radomes

Figure 2: Initial processing of uncalibrated radome effect at TSKB and TSK2 (courtesy of Reference Frame WG Chair).

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Romero: Infrastructure Committee
This test campaign aims to find the effect on the marker positions of the uncalibrated
radomes installed over the GNSS antennas at co–located sites (sites which have morethan one geodetic technique). The effect will be studied by removing the uncalibrated
radomes for a number of weeks and then reinstalling them. It was hoped that most of thestations shown in Fig. 1 would participate, and that careful post–processing and analysis
will show an effect due to the radomes that can later be added to correct the co–locationtie vectors at each location to aid in the ITRF generation. So far the stations in Tab. 1
have participated in the experiment.
We hope that additional stations will join during 2013, which will be the last year of thisexperiment in advance of the upcoming ITRF2013 version. The preliminary analysis of
the data has found some significant effect that can be calibrated as shown in Fig. 2 .

2.4 Station Issues
Over 2012 the IC has supported the IGS Central Bureau (R. Khachikyan, D. Maggert) on
station issues; handling un–calibrated Antenna+Dome pairs, helping to find ways forward
on the NGA station issues, recovering long–term dormant stations, etc.
In particular for the NGA stations the IC together with the IGS NC have been able toclarify that there is a half–cycle issue with the phase data, which the NGA will correct
before publishing the data in the official IGS repositories. Additionally the previously
unknown ITT antenna used at most of the NGS sites has now been calibrated by the
NGS, and the calibration has been accepted by the IGS Antenna Working Group forinclusion into the official ANTEX calibration file during 2013 ahead of the 2nd IGS data
reprocessing campaign.
Participated in the Real–Time Pilot Project telecons and discussions on the RTCM–“Multi
Signal Message” definition to ensure full compatibility of the streaming standard and of
the RINEX 3.02 format and file naming.

3 Continued activities for 2013
During the upcoming year the IC will finalize the un–calibrated radome experiment for
co–located stations and promote in–depth analysis with the Reference Frame Working
Group with the aim of publishing a set of corrections for the “tie” vectors between the
GNSS monument and the other co–located technique.
Additionally the IC together with the Real Time Pilot Project will promote continued
progress on the streaming and RINEX data formats to accommodate the new Navigation
systems (QZSS, etc), and help the IGS in the second reprocessing campaign to take place
during 2013 by ensuring all infrastructure issues are addressed in a timely manner.

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4 Conclusions
Move forward with the implementation of the IC Workshop recommendations:
1. MGEX shall remove the RINEX 2 data requirement and work only with RINEX 3
data, and that the MGEX requests to the DCs that other past RINEX 3 data appeals
be stored together with the MGEX data moving forward.
2. That the IC fully supports and encourages the new fulltime Network Coordinator at
the IGS Central Bureau.
3. The IC and Network Coordinator will work to strengthen ties with regional networks
to promote the “Network of Networks” from the IGS.
4. The IC together with the RINEX WG shall investigate together with others the issue
of unique GNSS station identification (4 char ID codes, etc) and propose a possible
way forward for the IGS.
5. That the RINEX WG shall continue to iterate in the proposed direction for new
RINEX 3 data filenames, incorporating any new GNSS station identifier.
6. The IC will promote that the RINEX WG shall keep the RINEX 3 format open at
all times as a “working draft” and to publish “formats” as needed.

4 Conclusions
The IC continues to be a relevant part of the IGS in providing advice and support to the
Network Coordinator and the ACC. It is also the place where other parts of the IGS turnfor coordination and ways forward on infrastructure issues. The IC tries to bring long–term issues to satisfactory conclusions and provides a forum of ideas and infrastructuresuggestions for the IGS Governing Board.

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Romero: Infrastructure Committee

128

CDDIS Global Data Center Technical Report 2012
C. NollNASA Goddard Space Flight Center, Code 690.1
Greenbelt, MD 20771 USA
Carey.Noll@nasa.gov

1 Introduction
The CDDIS is NASA’s data archive and information service supporting the international
space geodesy community. For over 30 years, the CDDIS has provided continuous, longterm, 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 fromthese data required for a variety of science observations, including the determination ofa global terrestrial reference frame and 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 sets and user requirements. The CDDIS is one of NASA’s
Earth Observing System Data and Information System (EOSDIS) distributed data archive
centers; EOSDIS data centers serve a diverse user community and are tasked to provide
facilities to search and access science data and products.
The CDDIS serves as one of the primary data centers and core components for the geometric services established under the International Association of Geodesy (IAG), an organization that promotes scientific cooperation and research in geodesy on a global scale.
The system has supported the International GNSS Service (IGS) as a global data center
since 1992. The CDDIS activities within the IGS during 2012 are summarized below; thisreport also includes any recent changes or enhancements made to the CDDIS.

2 System Description
The CDDIS archive of IGS data and products are accessible worldwide through anonymous
ftp. The CDDIS is located at NASA’s Goddard Space Flight Center (GSFC) and isavailable to users 24 hours per day, seven days per week. The CDDIS computer system

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Noll: Crustal Dynamics Data Information System
consists mainly of incoming, outgoing, and processing servers. All ftp and web access isperformed 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 isperformed in a separate environment that also includes a database server for managing
metadata extracted from incoming data.
In 2011, the CDDIS staff procured new server hardware to further enhance the capabilitiesof the system and ensure a robust archive environment. The new system is fully redundantwith the primary and secondary/failover system located in different buildings on the GSFC
campus. 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 a
32 Tbyte RAID storage system and is scaled to accommodate future growth. The newserver configuration became operational in May 2012.

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. Approximately 7 Tbytes of the CDDIS archive are devoted to GNSS data
(6.5 Tbytes), products (250 Gbytes), and ancillary information. All data and products areaccessible through subdirectories of ftp://cddis.gsfc.nasa.gov/gnss (a symbolic linkto ftp://cddis.gsfc.nasa.gov/gps).

3.1 GNSS Tracking Data
The user community has access to the on–line archive of GNSS data available through theglobal data center archives of the IGS. Over 50 operational and regional IGS data centersand 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. Tables 1 and 2 on page 131 summarizes the types of GNSS
data archived at the CDDIS.
Data, in RINEX V2.10 or V2.11 format, from GPS and GPS+GLONASS receivers arearchived within the GNSS directory structure /gnss/data.

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

Sample Rate

Daily GNSS
Hourly GNSS
High–rate GNSS
Satellite GPS

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

Data Format

Available On–line

RINEX and compact RINEX
Compact RINEX
Compact RINEX
Compact RINEX

Since 1992
2+ years
Since May 2001
Since 2002

Table 2: GNSS Data Archive Summary for 2012.

Data Type

Daily GNSS
Hourly GNSS
High–rate GNSSLEO GPS

Avg. No.
Sites/Day

Avg.
Vol./Day

Total
Vol./Year

475
290
155
1

985 Mb
310 Mb1800 Mb
0.5 Mb340 Gb
105 Gb565 Gb200 MbDirectory Location

Latency of
Majority ofData/gnss/data/daily/gnss/data/hourly/gnss/data/highrate/gnss/data/satellite

1 hour10 minutes
10 minutes
10 days

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 170 K daily station days
from 525 distinct GNSS receivers were archived at the CDDIS during 2012. A complete
list of daily, hourly, and high–rate sites archived in the CDDIS can be found in the yearlysummary reports at URL ftp://cddis.gsfc.nasa.gov/reports/gnss/.
Within minutes of receipt, the hourly GNSS files are archived to subdirectories by year,
day, and hour. These data are retained on–line indefinitely; the daily files delivered at
the end of the UTC day contain all data from these hourly files and thus can be used inlieu of the individual hourly files. A total of 320 hourly sites (2.5 M files) were archived
during 2012.
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 170 high–rate sites (5 M files)
were also archived in the CDDIS in 2012.
The CDDIS generates a global broadcast ephemeris file on an hourly basis. This fileis derived from the site–specific ephemeris data files for each day/hour. These files areappended to a single file that contains the orbit information for all GNSS satellites forthe day up through that hour. This merged ephemeris data file is then copied to theday’s subdirectory within the hourly data file system. Within 1–2 hours after the end of
the UTC day, after sufficient station–specific navigation files have been submitted, this131

Noll: Crustal Dynamics Data Information System
Table 3: GNSS MGEX Data Archive Summary for 2012.

Data Type

Avg. No.
Sites/Day
RINEX 3/2

Avg.
Vol./Day

45/5
23/6
17/5

200 Mb50 Mb
370 MbDaily GNSS
Hourly GNSS
High–rate GNSS

Directory LocationData/gnss/campaign/mgex/data/daily/gnss/campaign/mgex/data/hourly/gnss/campaign/mgex/data/highrateconcatenation procedure is repeated to create the daily broadcast ephemeris file, using
daily site–specific navigation files as input. The daily file is copied to the corresponding
subdirectory under the daily file system. Users can thus download this single, daily (orhourly) file to obtain the unique navigation messages rather than downloading multiple
broadcast ephemeris files from the individual stations.
The CDDIS successfully submitted a proposal to the IGS Multi–GNSS Experiment (MGEX)
call for proposals for archive and distribution of data and products. During 2012 the CDDIS expanded its data archive and distribution service to include data from participating
multi–GNSS receivers, products derived from the analysis of these data, and required
metadata for the experiment. These data include newly available signals (e.g., Galileo,
QZSS, SBAS, and BeiDou). The CDDIS data ingest procedures were modified to accommodate these new data sets, the majority of which are archived in RINEX V3; some sites
have delivered data in RINEX V2 in support of MGEX. The CDDIS developed new software to extract metadata from incoming data files since the software package currently
used for summarization and metadata extraction on RINEX V2 data, teqc, will not process data in RINEX V3 format. The summary of the MGEX data holdings at the CDDIS
are shown in Tab. 3.
The CDDIS archived data from space–borne GPS receiver data from selected missions(e.g., SAC–C, CHAMP, Jason–1, ICESat). In 2012 additional ICESat GPS receiver data
and attitude files were archived.

3.2 IGS Products
The CDDIS routinely archives IGS operational products (daily, rapid, and ultra–rapid
orbits and clocks, and weekly ERP and station positions) as well as products generated by
IGS working groups and pilot projects (ionosphere, troposphere, real–time clocks). The
CDDIS currently provides on–line access through anonymous ftp or the web to all IGS
products generated since the start of the IGS Test Campaign in June 1992 in the filesystem /gnss/products; products from GPS+GLONASS products are available throughthis filesystem. Products derived from GLONASS data only continued to be archived at
the CDDIS in a directory structure within the file system /glonass/products.
132

3 Archive Content
Table 4: GNSS Product Summary.
Product Type

Number of
ACs/AACs

VolumeDirectory

Orbits, clocks,
ERP, positions

13+Combinations

830 Mb/week/gnss/products/WWWW(GPS, GPS+GLONASS)/glonass/products/WWWW(GLONASS only)

Troposphere

Combination

2.5 Mb/day,
860 Mb/year/gnss/products/troposphere/YYYY

Ionosphere

4+Combination

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

Real–time clocks

Combination

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

The CDDIS also continues to archive combined troposphere estimates in directories by
GPS week. Global ionosphere maps of total electron content (TEC) from the IONEX
AACs are archived in subdirectories by year and day of year. Real–time clock comparison
products have been archived at the CDDIS in support of the IGS Real–Time Pilot Projectsince 2009. Table 4 above summarizes the GNSS products available through the CDDIS.

3.3 Supporting Information
Daily status files of GNSS data holdings, reflecting timeliness of the data delivered as well
as statistics on number of data points, cycle slips, and multipath, continue to be generated
by the CDDIS. By accessing these files, the user community can receive a quick look ata day’s data availability and quality by viewing a single file. The daily status files areavailable through the web at URL ftp://cddis.gsfc.nasa.gov/reports/gps/status .
The daily status files are also archived in the daily GNSS data directories. In preparation
for the analysis center’s second reprocessing campaign, the CDDIS has developed site–
specific reports detailing missing data. Station operators and operational data centers
can consult these lists (ftp://cddis.gsfc.nasa.gov/gnss/data/daily/reports) and
if available, supply missing files to the CDDIS for inclusion in the global data centerarchives.
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/gps. The
CDDIS also maintains an archive of and indices to IGS Mail, Report, Station, and other
IGS–related messages.

133

25	
  

250	
  

20	
  

200	
  

15	
  

150	
  

10	
  

100	
  

5	
  

50	
  

0	
  

Australia/Oceania
1%

0	
  
Daily	
  Hourly	  High-­‐Rate	  Products	
  

Type	
  of	
  GNSS	  File	  Tbytes	  S. America
Africa
0%
0%

Other
16%
Number	  of	
  Files	  Downloaded	
  (M)	
  Volume	  Downloaded	
  (Tbytes)	
  Noll: Crustal Dynamics Data Information System

Europe
35%

Asia
23%

North America
25%

Number	  of	
  Files	  Figure 1: Number and volume of GNSS files
transferred from the CDDIS in
2012.

Figure 2: Geographic distribution of IGS
users of the CDDIS in 2012.

4 System Usage
Figure 1 summarizes the usage of the CDDIS for the retrieval of GNSS data and products
in 2012. This figure illustrates the number and volume of GNSS files retrieved by the user
community during 2012, categorized by type (daily, hourly, high–rate, products). Over420 million files (40 Tbytes), excluding robot downloads, were transferred in 2012, withan average of over 35 million files per month. Figure 2 illustrates the profile of users
accessing the CDDIS IGS archive during 2012. The majority of CDDIS users are fromhosts in Europe and North America.

5 Recent Developments
The CDDIS is cooperating in the development of Geodetic Seamless Archive Centers(GSAC) with colleagues at UNAVCO, SIO, and the University of Nevada at Reno. The
activity provides web services to facilitate data discovery within and across participatingarchives. A prototype implementation of these GSAC web services at the CDDIS has beendeveloped and should be operational in early 2013. In addition, the CDDIS is currently
implementing modifications to the metadata extracted from incoming data and productfiles pushed to its archive. These enhancements have facilitated cross discipline data
discovery by providing information about CDDIS archive holdings to other data portals
such as Earth Observing System (EOS) Clearinghouse (ECHO) and future integration
into the Global Geodetic Observing System (GGOS) portal.

134

7 Future Plans

6 Publications
The CDDIS staff attended several conferences during 2012 and presented papers on or
conducted demos of their activities within the IGS, including:Noll, C., P. Michael, M. Dube, N. Pollack. An Update on the CDDIS. 2012 IGS
Analysis Workshop, Olsztyn, Poland, July 2012.
Noll, C., M. Dube, P. Michael, N. Pollack, L. Tyahla. Improvements to the Crustal
Dynamics Data Information System. Abstract IN43B–1515 presented at 2012 Fall
Meeting, AGU, San Francisco, Calif., 03–07 Dec., 2012.
Electronic versions of this poster and other publications can be accessed through the
CDDIS on–line documentation page on the web at URL http://cddis.gsfc.nasa.gov/
reports.html .

7 Future Plans
The CDDIS will continue to support the IGS MGEX. The experiment is an excellent
opportunity to prepare the data centers for archive of data in RINEX V3.
The CDDIS is supporting the IGS Real–Time Pilot Project as a data center. During 2012,
the CDDIS purchased hardware to implement an NTRIP Castor for the transmission of
real–time data streams from stations to users. CDDIS has set up a dedicated server
for this task. This service will be tested during early 2013. Possible future activities
include capturing the streams for generation of 15–minute high–rate files for archive at
the CDDIS.
In 2013, the IGS analysis centers will begin work on 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).
The CDDIS generates and updates status files, (/gnss/data/daily/YYYY/DDD/YYDD.status)that summarize the holdings of daily GNSS data. These files include a list of stations.
The archive status files of CDDIS GNSS data holdings reflect timeliness of the data delivered as well as statistics on number of data points, cycle slips, and multipath. The user
community can receive a snapshot of data availability and quality by viewing the contentsof such a summary file. The CDDIS will enhance this information by providing additional
files that list stations not providing data for the particular day.

135

Noll: Crustal Dynamics Data Information System

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

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

9 Acknowledgments
The author would like to thank the CDDIS contractor staff, Maurice Dube and Nathan Pollack (Science Systems and Applications, Inc./SSAI), Patrick Michael (Catholic University of America), Lori Tyahla and Lisa Lee (Stinger Ghaffarian Technologies/SGT), andJames 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, ISSN
0273–1177, 2010. doi: 10.1016/j.asr.2010.01.018 .
Noll, C., Y. Bock, H. Habrich and A. Moore. Development of data infrastructure to
support scientific analysis for the International GNSS Service. Journal of Geodesy, 83(3–4):309–325, 2009 doi: 10.1007/s00190-008-0245-6 .

136

IGN data center report 2012
A. Duret, and B. Garayt
Institut National de l’Information Géographique et Forestière
IGN SGN, 73 avenue de Paris, 94165 Saint-Mand’e cedex, France
E-Mail: anne.duret@ign.fr, bruno.garayt@ign.fr

The IGN Global Data Centre (GDC) has been designed and implemented in answer toboth the Analysis Centers and the surveying user community requirements, for post–processing and real-time applications. The GNSS observations from all the IGS network
stations and from the low earth orbit satellites, as well as the IGS products are archived
and available at IGN GDC. The IGN data center is handled by the geodetic and levelingdepartment (SGN) which is the operational service of geodesy of the National Institute ofGeographic and Forest Information (IGN).
So as to have a more reliable data flow and a better availability of the service, two identicalconfigurations with the same data structure have been setup in two different locations in
IGN. Each configuration has:
• FTP deposit server for data and analysis centers uploads,– Special authentication is necessary to access.
– Please contact the IGN team at– igsadm@ign.fr if you are not registered in.
• FTP anonymous access to the GNSS observations and products,• Fully independent Internet links.
The two configurations are in mirroring using VPN connections.
As soon as they are available, GNSS observations and IGS products uploaded at IGN
deposit servers by the data and analysis centers are pushed to the public FTP servers.
A mirroring is performed with the other GDCs and between the two IGN sites to complete
the archive (see Fig. 1).
The anonymous ftp servers can be access through:• ftp://igs.ensg.eu for the Marne–la–Vall’ee site
• ftp://igs.ign.fr for the Saint–Mand’e site137

Duret and Garayt: Institut National de l’Information Géographique et Forestière

Figure 1: Principle of mirrowing between the two IGN sites.

Since the beginning of the year, the IGN DC is contributing to the IGS MGEX project.
Data and products are publicly available using anonymous connections at both sites within
the following data structure:• M–GEX site logs: /pub/igs/data/campaign/mgex/log• Daily 30–second files:– /pub/igs/data/campaign/mgex/daily/rinex3/YYYY/DDD– /pub/igs/data/campaign/mgex/daily/rinex2/YYYY/DDD– /pub/igs/data/campaign/mgex/daily/raw/YYYY/DDD• Hourly 30–second files:– /pub/igs/data/campaign/mgex/hourly/rinex3/YYYY/DDD– /pub/igs/data/campaign/mgex/hourly/rinex2/YYYY/DDD– /pub/igs/data/campaign/mgex/hourly/raw/YYYY/DDD• 15–minute 1–second files:– /pub/igs/data/campaign/mgex/highrate/rinex3/YYYY/DDD– /pub/igs/data/campaign/mgex/highrate/rinex2/YYYY/DDD– /pub/igs/data/campaign/mgex/highrate/raw/YYYY/DDD• Products: /pub/igs/products/mgex/WWWW/

Where YYYY, YY are the year, DDD is the day of year, and WWWW the GPS week.
A deposit ftp area is available under request at ftp://igsdepot.ign.fr for data uploads.

138

Part IV

Working Groups, Pilot Projects

139

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

1 Preparations for the second IGS reprocessing campaign
In 2013, the IGS will perform its second comprehensive reprocessing campaign (repro2).
In order to have the best possible antenna phase center information available for repro2,
the IGS model igs08.atx was updated with satellite–specific z–offsets for all satellites
launched since the release of the original model (Sect. 1.1). Besides, subtype calibrations
for JPSREGANT antennas were introduced that show significant differences (Sect. 1.2).

1.1 Update of satellite–specific z–offsets
Since the adoption of igs08.atx in April 2011, one GPS (G063) and five GLONASS
satellites (R742–R746) had been launched. For all those satellites, block mean values wereapplied until September 2012. In GPS week 1706 (16 September 2012), those were updatedwith satellite–specific z–offset estimates (see IGSMAIL #6650 and Tab. 1) provided by
Paul Rebischung (IGN). As R743 was not put into operation until 17 September 2012, it
could not be considered for the reanalysis. In contrast, the z–offsets of G062 and R801
were additionally reanalyzed, as the available estimates had been based on limited data.
All other active satellites were fixed to igs08.atx values.
The updated values were estimated from operational SINEX files of six ACs (CODE,
ESOC, GFZ, MIT, NGS and NRCan), CODE and ESOC being the only to provide offset
estimates for the GLONASS satellites. Figure 1 shows the weekly z–offset estimates forG063. Usually, the quality is worse in the beginning, as the number of tracking stations
is limited as long as the newly launched satellite is not set healthy.
From the weekly estimates weighted mean values per AC were derived (see Tab. 1). The
maximum differences between ACs are below 5 cm for all satellites, also for those withthe shortest lifetime. Due to this very good agreement and due to the fact that not all
ACs analyzed the same amount of data, unweighted mean values per satellite were derived

141Schmid: Antenna Working Group
G063

1.65

CODE
NRCan
ESOC
GFZ
MIT
NGS

z-PCO [m]

1.60

1.55

1.50

1650

1660

1670

GPS week

1680

1690

1700

Figure 1: Weekly z–offset estimates [m] from operational SINEX files of six ACs for G063 (courtesy of P. Rebischung).

for igs08.atx. In some cases those final values differ considerably from the block meanvalues used before (correction of about 30 cm for R746 and R801), and in all cases thecorrections are significant.

1.2 Consideration of JPSREGANT antenna subtypes
Sometime in 2000, Javad changed the setup of two of its JPSREGANT antenna types(JPSREGANT_DD_E, JPSREGANT_SD_E). However, the introduction of these new subtypes
did not produce a new name definition and proper recognition within the IGS. Since theadoption of igs05.atx in November 2006, mean phase center corrections over the two
subtypes were in use for both antenna types. Therefore, all stations equipped with oneof the JPSREGANT antenna types were affected by a vertical bias of up to 2 cm since thattime.
In order to solve that problem, several things had to happen at the same time:• provision of subtype calibrations in igs08.atx• correction of the antenna type in the affected site logs

• correction of the station coordinates in the course of an update of the IGS reference
frame realization
After the correct subtypes actually installed at the affected IGS stations had been identified
in most cases, the correction of the site logs could be carried out in conjunction with theswitch from IGS08 to IGb08 in GPS week 1709 (7 October 2012):• JPSREGANT_DD_E1: CONZ (RA0178), DLFT (RA0077), DWH1 (RA0083), MDVJ (RA0195),
MTBG (RA0085), STR2 (???005), UNB1 (RA0193), UNBJ (RA0193)• JPSREGANT_DD_E2: CAGZ (RRA052), KOU1 (RRA31)
142

1 Preparations for the second IGS reprocessing campaign
Table 1: Satellite–specific z–offset estimates for the seven latest GPS/GLONASS satellites (compare IGSMAIL #6650). Besides the number of weekly estimates, the weighted mean
per AC is given together with its RMS. The column igs08.atx shows the (block mean)values used before the update and ∆igs08 is the difference between the new and the oldvalue. All values in [m].
sat.

launchACG062

28.05.10

CODE
ESOC
GFZ
MIT
NGS
NRCan

G063

16.07.11

R742

no. of weeks

weighted weighted
mean
RMS

AC
mean

igs08.
atx∆igs08

102
102
99
98
93
81

1.58081.59011.5986
1.58751.60781.61900.02210.02400.03030.02770.02410.02581.5973

1.6632−0.0659

CODE
ESOC
GFZ
MIT
NGS
NRCan

54
54
44
51
38
43

1.55961.55201.54771.54511.59461.56890.03440.02250.02210.02510.01770.02081.56131.6500−0.088702.10.11

CODE
ESOC

43
42

2.38052.38160.02880.03692.38112.4500−0.0690R744

04.11.11

CODE
ESOC

36
36

2.56092.56530.03220.04372.56312.4500+0.1131R745

04.11.11

CODE
ESOC

35
35

2.64132.63300.02940.03222.63722.4500+0.1872R746

28.11.11

CODE
ESOC

34
33

2.76552.72170.03220.03272.74362.4500+0.2936R801

26.02.11

CODE
ESOC

20
17

2.09082.04270.02460.04482.06681.7500+0.3168• JPSREGANT_SD_E1: DLFT (RA0043), KHAJ (RA0032), MOBJ (RA0033), MOBK (RA0033),
NOVJ (RA0038), NOVM (RA0038), SUNM (RA0024), ZIMJ (RA0059)• JPSREGANT_SD_E2: DREJ (RA0290, RA0292, RA0293), FFMJ (RA0294), HUEG (RA0291,
RA0310), TITZ (RA0291, RA0311), WTZJ (RA0295)• JPSREGANT_SD_E: IRKJ (RA0225(?); not corrected due to contradictory information)
More details are given in IGSMAIL #6662.

143

Schmid: Antenna Working Group

2 Updates and content of the antenna phase center model
In case the satellite constellation changes or new receiver antenna calibrations become
available, the absolute antenna phase center model of the IGS has to be updated. The
GPS week of the release date is coded in the model name (igs08_wwww.atx). Table 2 lists
12 updates in 2012. Further details can be found in the corresponding IGSMAILs whose
numbers are also given.
Table 3 gives an overview of the data sets contained in the IGS phase center model. The
numbers refer to igs08_1719.atx that was released in December 2012. For GPS andGLONASS, there are 71 and 84 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.
For Galileo, BeiDou and QZSS, the IGS model does still not provide any information.
During the IGS Workshop in Olsztyn it was recommended to adopt conventional phasecenter offset (PCO) values for these new satellite antenna types. However, this will also
require an update of the ANTEX format to consider manufacturer–defined spacecraft body
frames and attitude modes. For the time being, conventional PCO values for new GNSS
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 also contains phase center calibration
values for 242 different receiver antennas. 152 of them are certain combinations of anantenna and a radome, whereas the remaining 90 antenna types are not covered by aradome. As Tab. 3 shows, igs08_1719.atx contains, among others, 106 absolute robot
calibrations and 90 converted field calibrations.
As the IGS Site Guidelines ask for elevation– and azimuth–dependent calibration values
down to 0◦ elevation, 141 different antenna types (106 ROBOT + 32 COPIED + 3 CONVERTED)
are currently approved for the installation at new or upgraded IGS stations. The remaining
101 types are no longer allowed, but their calibration values are still necessary for existing
installations (see Sect. 3) as well as for reprocessing purposes.

144

2 Updates and content of the antenna phase center model

Table 2: Updates of the phase center model igs08.atx in 2012.
week

date

IGSMAIL

1673

30-JAN-12

6533

1682

02-APR-12

6564

1685

26-APR-12

6576

1699

02-AUG-12

6634

1700

06-AUG-12

6640

1706

05-SEP-12

6650

1707

24-SEP-12

6662

1708

05-OCT-12

6670

1710

18-OCT-12

6676

1711

23-OCT-12

6679

1717

03-DEC-12—

1719

19-DEC-12—

changeAdded G049 (G24)
Decommission date: G024
Added G032 (G24)
Decommission date: G049 (G24)
Added NOV533+CR
NOVC
Added G037 (G24)
Decommission date: G032 (G24)
Added R801 (R26)
Added RNG80971.00
NONE
Added G049 (G24)
Decommission date: G037 (G24)z-offset updated: G062, G063, R742,
R744, R745, R746, R801 (see Sect. 1.1)
Added R743
Decommission date: R729
Added ASH701023.A
NONE
JPSREGANT_ DD_ E1 NONE
JPSREGANT_ DD_ E2 NONE
JPSREGANT_ SD_ E1 NONE
JPSREGANT_ SD_ E2 NONELEIGS08PLUS
NONE(compare Sect. 1.2)
Added G065
Decommission date: G049 (G24)
Added G049 (G27)
Decommission date: G027
Added R712 (R08)
Decommission date: R743
Added LEIAR20NONE
LEIAR20LEIMTIAPENG3100R1
NONE
Added LEIGS14
NONE

145

Schmid: Antenna Working Group
Table 3: Number of data sets in igs08_1719.atx (released in December 2012).
satellite antennas

numberGPS
GLONASS
Galileo
BeiDou
QZSS

71
84
0
0
0

receiver antennas

number

ROBOT
FIELD
COPIEDCONVERTED

106
90
32
14

3 Calibration status of the IGS network
Table 4 shows the percentage of IGS tracking stations with respect to certain calibration
types. For this analysis, 440 IGS stations as contained in the file logsum.txt (available at
ftp://igs.org/igscb/station/general/) on 11 January 2013 were considered. At thattime, 100 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_1722.atx that was released in January 2013.
In the meantime, absolute robot calibrations comprising elevation– and azimuth–dependent
PCVs down to the horizon are available for a bit more than three quarters of all IGS stations. About 8% of the stations are still equipped with antenna types for which purely
elevation–dependent PCVs derived from relative field calibrations have to be applied. Besides, about 15% of the antennas in the IGS network are either covered by an uncalibrated
radome or represent an unmodeled antenna subtype.
The latter category of stations is particularly disadvantageous in case the antenna is
co–located with other space geodetic instruments. Therefore, several IGS entities cooperatively organized a campaign to quantify the impact of the uncalibrated radome byremoving it for about two months at important co–location sites (Romero et al., 2012).
Table 4: Calibration status of 440 stations in the IGS network (logsum.txt of 11 January 2013,
igs08_1722.atx) compared to former years.
absolute calibration(azimuthal corrections
down to 0◦ elevation)

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

uncalibrated radome(or unmodeled
antenna subtype)DEC 2009
MAY 2012

61.4%
74.6%

18.3%
8.2%

20.2%
17.2%

JAN 2013

76.8%

7.7%

15.5%

date

146

References
The improvement between 2009 and 2012 (compare Tab. 4) is mainly related to the transition from igs05.atx to igs08.atx in 2011, as several additional robot calibrations could
be considered at that time. Since then, the problem associated with the JPSREGANT antennas (Sect. 1.2) could be nearly solved, and some inadequate antenna installations were
upgraded or decommissioned.

References
Romero I., P. Rebischung, J. Ray, R. Schmid, S. Fisher, and J. Griffiths. The IGS campaign
to measure position corrections for uncalibrated IGS radome stations. IGS Workshop
2012, 23–27 July 2012, Olsztyn, Poland, 2012.

147

Schmid: Antenna Working Group

148

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

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

2 Activities in 2012
• Regular generation of P1–C1 bias values for the GPS constellation and maintenanceof receiver class tables was continued at CODE/AIUB.
• The organization and realization of a first IGS Workshop on GNSS Biases wasa key challenge and achievement in 2012 (see also Section 3).
• The tool developed for direct estimation of GNSS P1–C1 and P2–C2 DCB values
could be completed. This tool was considerably further developed to be able to copewith all possible RINEX data scenarios, specifically with historical data, where wegot confronted with numerous problems and anomalies.

149

Schaer: Bias and Calibration Working Group• 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–C2 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 (or long–term) goal.
• The outdated (reliably working) GNSS DCB combination/estimation processing environment at CODE was completely redesigned in 2011/2012.
• Direct P1–C1 and P2–C2 bias results for GPS and GLONASS are now generated ona regular basis and made available at:
ftp://ftp.unibe.ch/aiub/CODE/• The ambiguity resolution scheme at CODE was extended to GLONASS for three
resolution strategies. It is essential that self–calibrating ambiguity resolution procedures are used. Resulting GLONASS DCPB results are collected and archived.
• 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.
• GPS quarter-cycle biases are still a serious issue (see, e.g., IGSMAIL #6583).

• Finally, the RINEX observation data monitoring was completely revised at CODE
in order to cope with the increasing number of possible GNSS observables (Schaer
et al., 2012). Examples of new result files are:ftp://ftp.unibe.ch/aiub/igsdata/odata2_day.txt
ftp://ftp.unibe.ch/aiub/igsdata/odata2_receiver.txt
ftp://ftp.unibe.ch/aiub/igsdata/y2012/odata2_d335.txt
ftp://ftp.unibe.ch/aiub/igsdata/y2012/odata2_d335_sat.txt
ftp://ftp.unibe.ch/aiub/igsdata/ndata2_day.txt
ftp://ftp.unibe.ch/aiub/igsdata/ndata2_receiver.txt
ftp://ftp.unibe.ch/aiub/igsdata/gdata2_day.txt
ftp://ftp.unibe.ch/aiub/igsdata/gdata2_receiver.txt

150

3 IGS Workshop on GNSS Biases 2012

3 IGS Workshop on GNSS Biases 2012
This workshop was held at the University of Bern on 18–19 January 2012. All related
information, including all presentations, may be found at:
http://www.biasws2012.unibe.ch
One main focus of this workshop was on biases specific to GLONASS:• IGS AC GLONASS inter–frequency code bias results were compared for the firsttime. It could be shown that the generation of an IGS–combined GLONASS clock
product should be possible (even with current IGS AC GLONASS clock products).
• The “GLONASS interoperability issue” was another key subject. There was finallya clear consensus that the causing bias must be addressed as differential code–phasebias (DCPB).

Workshop on GNSS Biases
18–19 January 2012
University of Bern, Switzerland (Hauptgebäude Universität Bern, Hörsaal HS 115)www.biasws2012.unibe.ch/programme.pdf

Programme and oral presentations
Wednesday 18 January
08:30–09:00 Workshop check-in
09:00–09:30 Welcome and Introduction – A. Jäggi, R. Dach
09:30–10:30 Participants’ short introductions (part 1) – R. Dach
3 slides presented by each participant (in alphabetical order)
10:30 Break
11:00–12:00 Participants’ short introductions (part 2) – R. Dach
3 slides presented by each participant (in alphabetical order)
12:00–12:30 Overview of GNSS biases (part 1) – S. Schaer
GPS/GLONASS differential code biases – S. Schaer
12:35–12:40 Photo session
12:45 Lunch
14:00–15:00 Overview of GNSS biases (part 2) – S. Schaer(30’) CODE’s DCB specialties, GLONASS ambiguity resolution,intersystem phase biases, GLONASS-GPS station-specificintersystem translations, IGS ANTEX model – S. Schaer(10’) DCB estimation at NRCan – R. Ghoddousi-Fard(10’) PRN22/SVN47 DCB anomaly – A. Hauschild
15:00–15:30 GLONASS biases and clock corrections (part 1) – R. Dach
Introduction and current status (CODE) – R. Dach
15:30 Break
16:00–17:00 GLONASS biases and clock corrections (part 2) – R. Dach
Presentations by IGS AC representatives:(10’) GFZ: Current status and plans – M. Uhlemann(10’) CNES/CLS: Experience from CNES-CLS IGS AC – S. Loyer(10’) Comparison of IGS AC GLONASS clock correction results –R. Dach(10’) GLONASS inter-channel biases in high-end receivers – J.-M.
Sleewaegen & A. Simsky
17:00–17:30 GNSS phase biases (part 1) – N. Teferle / S. Loyer(20’) Integer clocks and integer PPP issues – S. Loyer(10’) GLONASS Carrier Phase biases for RTK operation – G.
Zyryanov
19:00 DinnerThursday 19 January
09:00–09:30 GLONASS biases and clock corrections (part 3) – R. Dach(15’) Comparison of AC GLONASS biases – S. Schaer, M. Meindl
Discussions concerning definition of “GLONASS reference biases”
and proceeding towards an IGS-combined GLONASS clock product
09:30–10:30 GNSS phase biases (part 2) – N. Teferle / S. Loyer(15’) Uncalibrated Phase Biases for Precise Point Positioning Integer
Ambiguity Resolution – N. Teferle & X. Meng(15’) Estimation of uncalibrated hardware delays for singledifference ambiguity resolution – J. Tegedor(15’) GLONASS carrier-phase inter-frequency biases – L. Wanninger(15’) Biases in GLONASS carrier phase observables – A. Zinoviev
10:30 Break
11:00–12:30 New GNSS signals and related issues – J.-M. Sleewaegen / O.
MontenbruckPresentations by representatives of receiver manufacturers:(25’) New GNSS signals: how to deal with the plethora ofobservables? – J.-M. Sleewaegen(25’) Line bias variations in GPS L1/L2/L5 signals – O.
Montenbruck(10’) GLONASS RTK interoperability issues with 3rd party receivers– F. Takac & P. Alves(10’) Compass/Beidou: system status and initial service – J. Chen(presented by X. Meng)(10’) Status of IGS M-GEX – R. Weber
Discussion
12:45 Lunch
14:00–15:30 Bias calibration, combination, harmonization, exchange andformats – H. van der Marel / G. Petit(10’) Bias-SINEX – L. Agrotis(10’) RTCM / Special Committee 104, RINEX Status – J. Sass(10’) RTCM-SSR strategy of bias treatment – G. Wübbena(10’) Real-time calibration of GLONASS FDMA biases – A.
Cartmell(10’) Biases between BIPM's PPP clock solutions and IGS clock
solution for NIST – G. Petit(10’) Absolute calibration of P1-P2 biases and comparison with DCB
determination – G. Petit(10’) From differential to absolute code bias values – S. Schaer
Discussion
15:30 Break
16:00–16:30 Closing session – S. Schaer
Key issues, recommendations, action items
Keeping of the workshop minutes by Y. Jean (AIUB)

Last updated 2 February 2012/ss

Figure 1: Programme of the first IGS Workshop on GNSS Biases, Wednesday 18th (left) andThursday 19th January 2012 (right).

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Schaer: Bias and Calibration Working Group

Figure 2: 37 participants of the IGS Workshop on GNSS Biases on 18th January 2012 in frontof the main building of the University of Bern, Switzerland.

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.
S. Schaer and M. Meindl. IGSMAIL #6583: GPS quarter-cycle biases. http://igscb.
jpl.nasa.gov/pipermail/igsmail/2012/006575.html, 8 May 2012.
Schaer, S. Results from Bernese IGS Workshop “GNSS Biases” 18–19 January 2012. PPPRTK & Open Standards Symposium, March 12–13, 2012, Frankfurt am Main, Germany.
Schaer, S. Overview of Relevant GNSS Biases. Colloquium Satellite Navigation, TU
Munich, Germany, 21 May 2012.
Schaer, S. Results from IGS Workshop on GNSS Biases, 18–19 January 2012 in Bern.
IGS Workshop 2012, Olsztyn, Poland, July 23–27, 2012.
Schaer, S. S. Lutz, M. Meindl, and R. Dach. Completeness of IGS Tracking Data. IGS
Workshop 2012, Olsztyn, Poland, July 23–27, 2012.
152

IGS Data Center Working Group 2012
C. NollNASA Goddard Space Flight Center, Code 690.1
Greenbelt, MD 20771 USA
Carey.Noll@nasa.gov

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

2 Recent Activities
A Data Center Working Group meeting was held during IGS 2012 Workshop in Olsztyn,
Poland. Recommendations where made resulting from presentations during the workshop
and from splinter meeting discussions. Major topics discussed were the proposed changes
to the RINEX filenaming convention, handling multiple releases of files at the data centers,
and archiving RINEX V2 and V3 at the data centers. The IGS DCs recognize that a change
in the filenaming convention will enable improved organization of RINEX files, when theunique identification of the station name, file creation approach, and file content becomesvisible within the filename. Filename changes directly affect DC operations and therefore
an update will be a significant workload for the data centers. A new filename structure willremove some difficulties for DCs in handling RINEX files, but also induce new problems,
especially in resubmitted files. To help in the transition to a new filename structure, it
was recommended that data centers continue to archive RINEX V2 and RINEX V3 data
in separate structures. DCs should also separate high–rate data files created from streams
from those created from receivers. IGS users reported to DCs that decompression tools for“.Z” compressed file may no longer run on the newest generation of computers. Therefore,

153

Noll: Data Center Working Group
it is recommended once again that the DCs change the standard compression format usedwithin the IGS infrastructure as early as possible.
The DCWG also coordinated product archival, which involved working with the IGS ACC
in the final archiving of IGS repro1 products at the IGS Global Data Centers. The WG
began coordination on data center infrastructure support for the IGS M–GEX activity.
This activity included establishing a directory structure for both data (in RINEX V3
and V2) and products.

3 Future Plans
In 2013–2014, the DCWG will continue to work on addressing recommendations from the
IGS 2010 and 2012 workshops. Topics the WG hopes to address follow.
Support of the IGS Infrastructure Committee: A major focus of the DCWG will be tosupport the IC in its various activities to coordinate the resolution of issues related
to the IGS components. These activities will address recommendations from recent
IGS Workshops including assessment and monitoring of station performance anddata quality, generating metrics on these data.
RINEX filenaming convention: The DCWG will work with the IC and the RINEX WG
on the new IGS RINEX filenaming convention.
Data center harmonization: The working group will consider methodologies for ensuring
key data sets are available at all GDCs. Following recommendations from the IGS
2010 Workshop, the WG will coordinate with GDCs to ensure all GDCs archive datafrom all IGS stations as identified on the IGS network website; ODCs push data, andany subsequent resubmissions, from their stations to ALL GDCs and ODCs issues
advisory for ALL resubmissions.
Compression: As per a recommendation from the IGS 2010 and 2012 workshops, the
DCWG will develop a plan for the introduction of a new compression scheme into
the IGS infrastructure by evaluating tests of available tools, surveying the IGS infrastructure, making a recommendation on a new IGS compression scheme, andcoordinating recommendations with the IC to develop implementation schedule.
Real–time data streams/high–rate GNSS data handling: IGS data centers must ensurethat files generated from these streams are sufficiently reliable. The DCs mustalso coordinate to ensure consistent copies of high–rate files are archived. This
recommendation from 2010 IGS Workshop includes definition and development of1) tool for comparison of RINEX files from various construction approaches, 2)
minimum requirements for acceptance of an accumulated data stream of observations
as a RINEX file in IGS data archives, 3) mandatory/optional observation types
to be included, 4) procedures to fill the gaps in the case data streams have been154

4 Membershipinterrupted. This activity should be coordinated with the RTPP, ACs, DCs, and
IC. A related recommendation resulted from the 2012 IGS Analysis Workshop statingthat until the RINEX V3 filenaming convention is finalized, separate directories for
distinguishing between files created from streams and by receivers will be establishedby all DCs.
M–GEX: As the IGS Multi–GNSS Experiment begins, the DCWG will advise and coordinate archival of the experiment’s data from other GNSS and products derived fromthese data sets.

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

155

Noll: Data Center Working Group156

IGS Ionosphere Working Group
Technical Report 2012
A. Krankowski and R. Sieradzki
Geodynamics Research Laboratory of University
University of Warmia and Mazury in Olsztyn, Poland (GRL/UWM)

1 General goals
The Ionosphere Working group started the routine generation of the combine Ionosphere
Vertical Total Electron Content (TEC) maps in June 1998. This has been the main activity
so far performed by the four IGS Ionosphere Associate Analysis Centers (IAACs):• CODE Center for Orbit Determination in Europe,
Astronomical Institute, University of Bern, 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 and final VTEC maps is used by the each analysis
centers: Each IAACs compute the rapid and final TEC maps independently and withdifferent approaches including the additional usage of GLONASS data in the case of CODE
(Hernandez–Pajares et al., 2009).

157

Krankowski and Sieradzki: Ionosphere Working Group

2 Membership
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
17.
18.
19.
20.
21.
22.
23.
24.
25.
26.
27.
28.
29.
30.
31.

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

GSFC/NASA
RAL
SEC
MIT
BC
ESA/ESOC
ESA/ESOC
MUT
UPC
UPC
NRCAN
DLR
JPL
UWM
UNB
TU Graz
ESA/ESOCJPL
UPC
ESA/ESOC
UMB
ESA/ESOC
ESA/ESOC
CODE
ESA/ESOCROB
TU Wien
UWM
JPL
DGFI
TU Vienna

3 Products
1. Final GIM(please note that GIMs also include GPS and GLONASS stations’ and satellites’
DCBs)• combination of CODE, ESA, JPL and UPC iono products conducted by UWM• temporal and spatial resolution — at 2 hours × 5◦ × 2.5◦ (UT×Lon.×Lat.),• availability with a latency of 11 days
158

5 Recommendations after IGS Workshop 2012, Olsztyn, Poland
2. Rapid GIM• combination of CODE, ESA, JPL and UPC iono products conducted by UWM• temporal and spatial resolution — at 2 hours × 5◦ × 2.5◦ (UT×Lon.×Lat.),• availability with a latency of less than 24 hours
3. Predicted GIM for 1 and 2 days ahead (pilot product)• combination of ESA and UPC iono products conducted by ESA• temporal and spatial resolution — at 2 hours × 5◦ × 2.5◦ (UT×Lon.×Lat.),

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

5 Recommendations after IGS Workshop 2012, Olsztyn,
Poland• Higher temporal and spatial resolution of IGS combined GIMs - the IAACs (UPC
and JPL) agreed on providing their maps in IONEX format, with a resolution of
15 min, 1 degree and 1 degree in time, longitude and latitude respectively.
• 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 (end of 2012).
• The new the IAAC from GNSS Research Center (GRC), Wuhan University, China(Hongping Zhang, end of 2012).
• Cooperation with IRI COSPAR group159

Krankowski and Sieradzki: Ionosphere Working Group

6 The pilot phase of the new IGS ionospheric product —TEC fluctuations maps
According to the resolution of the IGS Ionosphere Working Group, which has been passed
during the IGS Workshop 2012 in Olsztyn, the new ionospheric product — fluctuations
TEC map — was made available. The routine generation of the test IGS product forregion around the North Geomagnetic Pole has started in March 2013 at Geodynamics
Research Laboratory of University of Warmia and Mazury in Olsztyn (GRL/UWM).
The new ionospheric product show the variability of TEC in the ionosphere for range
from 55 degrees of the north geomagnetic latitude to the North Geomagnetic Pole. Because of the relationship between the state of the ionosphere, geomagnetic field and local
time the TEC fluctuations maps are determined as a function of spherical geomagnetic
latitude and magnetic local time. The land mass configuration and the relatively small
number of stations make impossible the creating similar product for southern hemisphereat present. For the purpose of the generation of the product the 30 second dual–frequency
phase observations from about 180 stations are used. This number contain practically all
permanently working observatories at high north geomagnetic latitudes, which belong to
IGS/EPN Network, Polenet Network (Greenland) or participate in Plate Boundary Observatory mission (Alaska). It is worth to remember that the distribution of the stations
is very irregular (Fig. 1). The very small number of the stations on Russian Federation
territory make particularly adverse conditions for the ionospheric studies. Currently the

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

160

Figure 2: The example 6-hour of the averaged
ionospheric variability.

References
TEC fluctuations maps are generated using phase observations from GPS and GLONASS
satellites.
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 differenceof two geometry–free observations (L4) for consecutive epochs. The ROTI represents the
ROT deviation over 5 minute periods. Both these parameters determine the conditions in
the ionosphere for specified time. For the purpose of the new product the two new indices:
MROTI and DROTI are applied. First of them is the mean of all ROTI values for specified
time window and the second is its deviation. The new parameters are used to estimate
the variability in the ionosphere within the presupposed time. The MROTI and DROTI
are calculated for the grid with dimensions: 5 degrees (magnetic local time) and 2 degrees(geomagnetic latitude) with shift 2.5 and 1 degree respectively. At present the two typesof TEC fluctuations maps are generated: the daily map and 6–hour map. The further
shortening of the time resolution cause the occurrence of the areas practically without
any observations. Taking into account the dynamics of the high–latitudinal ionosphere, it
makes impossible to obtain the reliable information about the conditions for these areas.
The final TEC fluctuations maps are written in the modified IONEX format (Sieradzki
and Cherniak, 2012). During the pilot phase of the product its graphical form can befound: http://igsiono.uwm.edu.pl .

References
Hernandez–Pajares M., J. M. Juan, J. Sanz, R. Orus, A. Garcia–Rigo, J. Feltens, A. Komjathy, S. C. Schaer, A. Krankowski. The IGS VTEC maps: A reliable source of ionospheric information since 1998. Journal of Geodesy, 83(3–4): 263–275, 2009. doi:
10.1007/s00190-008-0266-1.
Sieradzki, R., I. Cherniak. The Occurence of the TEC Fluctuations at High Latitudes
During Very Low Solar Activity. IGS Workshop 2012, 23–27 July 2012, Olsztyn, Poland,
2012.

161

Krankowski and Sieradzki: Ionosphere Working Group162

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

1 Introduction
In recognition of a rapidly evolving GNSS landscape, the Multi–GNSS Working Group(formerly the GNSS Working Group) has been established to explore and promote theuse of new navigation signals and constellations within the IGS. It shall enable an earlyfamiliarization with new GNSSs, identify and master relevant challenges, and prepare useof emerging navigation systems in routine IGS products. As set forth in its latest charterof Jan. 2012, the core activity of the MGWG is 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 newconcepts and data processing tools, and, finally, the generation of early data products for
Galileo, QZSS, BeiDou. To achieve these goals, the Multi–GNSS Working Group interacts
closely with other IGS entities, such as the RINEX WG, the Antenna WG, the Data Center
WG and the Infrastructure Committee. It helps to develop and implement new standards
for multi–GNSS–related work within the IGS.

2 Network
Following a call for participation released in the summer of 2011, the build–up of a new
network of multi–GNSS sensor stations has been initiated and made substantial progressin short time. By the end of 2012 the MGEX network comprises roughly 50 stations
supporting at least one of the new navigation systems (Galileo, BeiDou, and QZSS) on
top of the legacy GPS, GLONASS and SBAS systems. The bulk of stations is provided
by former IGS partners such as BKG, CNES, GFZ, GSI, IGN, and LMV (in alphabeticalorder) that have upgraded/supplemented existing sites with new, multi–GNSS–capable
receivers and antennas or started to deploy new multi–GNSS networks (such as CNES

163

Montenbruck: Multi–GNSS Working GroupMGEX(Dec 2012)

Figure 1: Distribution of MGEX stations supporting tracking of QZSS (blue), Galileo (red), andBeiDou (yellow) as of Dec. 2012.

REGINA network). As shown in Fig. 1, the present set of MGEX stations exhibits analmost global coverage, even though a concentration in Europe and a reduced coveragein the Americas and the West Pacific are obvious. However, this situation is expected to
improve soon with announced contributions from DLR (CONGO network), ESA, JAXA
(MGM–net), and GA. While most MGEX sites support tracking of the Galileo satellites,
only a subset of stations is presently providing data for QZSS and BeiDou. In particular,
the regional BeiDou constellation (i.e. the GEO and IGSO) satellites are not well coveredby the current network.
Further MGEX sites are encouraged and sites can still be submitted through the MGEX
submission form (http://igs.geolinks.org/mgex) under the provision of relevant improvements to the capabilities, coverage and homogeneity of the overall network.
In terms of equipment, six basic receiver types and five basic antenna types are presently
employed at the MGEX stations (see Tab. 1 and 2). Observation types provided by
the individual receivers have been compiled from summary reports generated by AIUB
as part of their routine monitoring of RINEX 3 observation files from MGEX stations(see ftp://ftp.unibe.ch/aiub/mgex/odata2_receiver.txt). It may be noted that nocommon standard has yet evolved in terms of supported signals and observation types.
This causes certain restrictions for data analysis and product generation. As an example,
Galileo orbit and clock products will (at least initially) be based on E1/E5a observations
due to a limited coverage with E5b and E5ab tracking.
Selected sites (such as UNB and USNO) offer multiple receivers in short– or zero–baseline
configuration to facilitate equipment characterization. Further such installations will be
added to the MGEX network as part of proposed extensions.

164

2 Network

Table 1: Receiver types in use within the MGEX network (status Dec. 2012). Observation
types for Galileo (E), BeiDou (C), and QZSS (J) are based on RINEX 3 observation
codes as reported in the submitted data files. They do not necessarily indicate the fulltracking capabilities supported by the receivers but rather the observations presently
made available to MGEX users from the respective stations.
Receiver Type

Stations

Observations

IFEN SX_NSR_RT_800

1

E: 1X,5X,7X,8X,6X
C: 2I, 7I

JAVAD TRE_G3TH DELTA

12

E: 1X,5X

LEICA GR10, LEICA GR25 and LEICA GRX1200+GNSS

8

E: 1X,5X,7X,8Q

NOV OEM6

1

E: 1C,5Q

SEPT POLARX4TR and SEPT POLARXS

3

E: 1C,5Q,7Q,8Q
C: 2I,7I

TRIMBLE NETR926

E: 1X,5X,7X,8X
C: 2I,7I,6I
J: 1C,1X,2X,5X,6X

Table 2: Antenna types currently employed within the MGEX network (status Dec. 2012).
Antenna Type
AOAD/M_T
NONE
JAV_RINGANT_G3T NONEJAVRINGANT_DM SCI?
LEIAR25
NONE
TRM55971.00
NONE
TRM59800.00
NONE

Stations

and
and
and

LEIAR25.R3
TRM57971.00
TRM59800.00

LEIT
NONE
SCIS

and
and

LEIAR25.R4
TRM57971.00

LEIT
TZGD

2
10
1
15
8
15

165

IF(L1X,L5X)-(L1X,L7X) [m]Montenbruck: Multi–GNSS Working Group
0.10
CUT0
GMSD
0.08
0.06
0.04
0.02
0.00
-0.02
-0.04
-0.06
-0.08 2012/12/02
-0.10
21h

KZN2

SIN1

3.

3h

6h

9h

Figure 2: Triple–frequency combination of Galileo IOV–3 observations from various MGEX stations demonstrating a high coherency of E1, E5a, and E5b carrier–phase measurements
for the new European navigation satellites (from Montenbruck and Langley, 2013).

While all stations contribute data to offline archives hosted by CDDIS, IGN, and BKG for
the MGEX project, a selected subset is also supporting real–time analyses. All real–timestreams utilize NTRIP (Networked Transport of RTCM via Internet Protocol) that has
emerged as a standard for real–time GNSS data exchange. A dedicated MGEX caster ishosted by BKG in Frankfurt, where native raw data streams received from the individualsites are converted and encoded in a prototype of the RTCM3 Multiple–Signal–Message(MSM) format. While still in a draft status, RTCM3–MSM will enable a harmonizedframework for multi–GNSS real–time operations and ensure a seamless conversion to the
RINEX 3 offline data format. The new MGEX NTRIP caster provides a basis to gain earlyexperience with the new MSM format and facilitates a timely adaptation of user software.
This is further supported through freeware software modules for data conversion provided
by BKG as part of its BNC client.
While a systematic quality control and signal analysis has not yet started, first performanceassessments of both the ground and space segment have already been reported in Raziq
et al. (2012) and Montenbruck and Langley (2013) based on MGEX data.

3 Products
While the newly established MGEX network forms a mandatory prerequisite for multi–
GNSS work within the IGS, the MGEX experiment comprises a wider range of activities
that are presently established. Foremost, the generation of orbit and clock products forthe new constellations is promoted in coordination with new and established IGS analysis
centers. Initial Galileo IOV products are already provided by CNES/CLS (Loyer et al.,2012), CODE (Prange et al., 2012), and GFZ (Uhlemann et al., 2012) since mid–2012 anda combined Galileo+QZSS product has recently been added by TUM (Hackel et al., 2012;
Steigenberger et al., 2013). Aside from the MGEX network, some of these solutions makecomplementary use of proprietary multi–GNSS networks to compensate existing coverage
limitations and achieve an improved product quality. Based on inter–agency comparisons,166

Radial [m]

2.0
1.5
1.0
0.5
0.0
-0.5
-1.0
-1.5
2012
-2.0

Along-track [m]

2.0
1.5
1.0
0.5
0.0
-0.5
-1.0
-1.5
2012
-2.0

Cross-track [m]3 Products

2.0
1.5
1.0
0.5
0.0
-0.5
-1.0
-1.5
2012
-2.0

9.Dec

9.Dec

9.Dec

-0.10+/-0.12m

10.

11.

12.

13.

14.

15.

-0.31+/-0.40m

10.

11.

12.

13.

14.

15.

-0.03+/-0.26m

10.

11.

12.

13.

14.

15.

GPS Time

Figure 3: Comparison of TUM orbit products of QZS–1 with final product of JAXA for a one
week data arc in Dec. 2012 .

a user equivalent range error (UERE) of a few decimeters is presently achieved by MGEX
orbit products of both the Galileo and QZSS satellites (see Fig. 3).
Concerning the Chinese BeiDou system, which has now reached its initial operational
capability for a regional service, early orbit and clock determination results have beenreported by various Chinese (Zhou et al., 2012) and European (Steigenberger et al., 2012)
researchers using data from dedicated regional sensor station networks. An effort will
be made to promote the extension of the BeiDou tracking capabilities within the MGEX
network and to make MGEX–only or mixed–network–based orbit and clock products for
BeiDou accessible to a wider user community through the MGEX data centers.
In the absence of publicly available broadcast navigation data for either Galileo or BeiDou,
the MGEX orbit and clock products constitute a significant promotion for the early use of
all available navigation systems. Aside from initial positioning experiments they provide abasis for the in–depth characterization of both the space and user segment, and — hopefully — help facilitate an improved interaction with system providers. Early applicationsof MGEX multi–GNSS products and observations have, for example, been reported in
Langley et al. (2012), Nadarajah et al. (2012), and Montenbruck et al. (2012).

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Montenbruck: Multi–GNSS Working Group

4 Standardization
In support of MGEX, the Multi–GNSS WG interacts closely with other IGS working
groups to coordinate data formats, processing standards and applicable models for use inmulti–GNSS work. Examples include necessary RINEX 3 and RTCM3 extensions for a
full support of new GNSS signals and tracking modes as well as the rapidly growing setof diverse broadcast navigation data. Another focus of current work addresses the proper
modeling of antenna offsets and phase patterns for receiver and satellite antennas, alongwith a documentation of constellation–specific coordinate systems and attitude modes.
This work is performed in close coordination with the IGS Antenna Working Group.

5 Public OutreachAs a central point for exchange of MGEX–related information with the user community,
a dedicated website has been established at http://igs.org/mgex. The new web site
provides an overview of available MGEX data and products with direct links to the respective archives at IGS data and product centers. Furthermore, users are provided with
up–to–date information on the status of emerging navigation satellite systems as well asrecommended parameters (e.g. antenna offsets) for a harmonized and consistent processingof MGEX observations.
Through individual members, the Multi–GNSS Working Group is furthermore represented
in other boards and bodies such as the International Committee on GNSS (ICG), the IAG
and the Multi–GNSS Asia (MGA) project.
Dedicated presentations of the MGEX project have been initiated for the EGU General
Assembly (April 2013), ION Pacific PNT meeting (April 2013) and the 4th China Satellite
Navigation Conference (May 2013).

168

References

Acronyms and Abbreviations
AIUB
BKG
CLS
CNES
CODE
CONGO
DLR
GA
GEO
GFZ
GSI
IGN
IGSO
ION
JAXA
LMV
PNT
REGINA
MGM–net
RTCM
WG

Astronomisches Institut der Unversität Bern
Bundesamt für Kartographie und Geodäsie
Collecte Localisation Satellites
Centre National d’Etudes Spatiales
Center for Orbit Determination in Europe
Cooperative Network for GNSS Observation
Deutsches Zentrum für Luft– und Raumfahrt
Geoscience Australia
Geostationary Orbit
Deutsches GeoForschungsZentrum
Geospatial Information Authority of Japan
Institut National de l’Information Géographique et Forestière
Inclined Geosynchronous Orbit
Institute of Navigation
Japan Aerospace Exploration Agency
Swedish National Land Survey (Lantmaeteriverket)
Position, Navigation and Timing
REseau GNSS pour l’IGS et la Navigation
Multi–GNSS Monitoring Network
Radio Technical Commission for Maritime Services
Working Group

References
Hackel, S., P. Steigenberger, O. Montenbruck, A. Hauschild, and U. Hugentobler. Galileo
IOV Orbit Determination and Validation. IGS Workshop 2012, 23–27 July 2012, Olsztyn, Poland, 2012.
Langley, R. B., S. Banville, and P. Steigenberger. First Results: Precise Positioning with
Galileo Prototype Satellites. GPS World, 23(9):45–49, 2012.
Loyer, S., F. Perosanz, F. Mercier, and H. Capdeville. MGEX activities at CNES–CLS
Analysis Center. IGS Workshop 2012, 23–27 July 2012, Olsztyn, Poland, 2012.
Montenbruck, O., A. Hauschild, P. Steigenberger, U. Hugentobler, and S. Riley. A COMPASS for Asia: First Experience with the BeiDou–2 Regional Navigation System. IGS
Workshop 2012, 23–27 July 2012, Olsztyn, Poland, 2012.
Montenbruck, O. and R. Langley. Galileo IOV–3 Broadcasts E1, E5, E6 Signals. GPS
World, 24(1):18–27, 2013.

169

Montenbruck: Multi–GNSS Working Group
Nadarajah, N., P. J. G. Teunissen, P. J. Buist, and P. Steigenberger. First Results of Instantaneous GPS/Galileo/COMPASS Attitude Determination. 6th ESA Workshop on
Satellite Navigation Technologies, NAVITEC 2012, 5–7 Dec. 2012, Noordwijk, Netherlands, 2012.
Prange, L., R. Dach, S. Lutz, S. Schaer, M. Meindl, and A. Jäggi. MGEX data analysis
at CODE — first experiences. IGS Workshop 2012, 23–27 July 2012, Olsztyn, Poland,2012.
Raziq, N., A. El–Mowafy, P. J. G. Teunissen, A. Nardo, and H. van der Marel. Curtin and
Delft Multi–GNSS M–GEX Stations: Infrastructure and Analysis Tools. IGS Workshop
2012, 23–27 July 2012, Olsztyn, Poland, 2012.
Steigenberger, P., A. Hauschild, O. Montenbruck, and U. Hugentobler. Performance Analysis of Compass Orbit and Clock Determination and Compass–only PPP. IGS Workshop
2012, 23–27 July 2012, Olsztyn, Poland, 2012.
Steigenberger, P., A. Hauschild, O. Montenbruck, C. Rodriguez–Solano, and U. Hugentobler. Orbit and Clock Determination of QZS–1 Based on the CONGO Network.
Navigation — Journal of the ION, in print, 2012.
Uhlemann, M., M. Ramatschi, and G. Gendt. GFZ’s Global Multi–GNSS Network And
First Data Processing Results. IGS Workshop 2012, 23–27 July 2012, Olsztyn, Poland,
2012.
Zhu, S. S., Y. L. Cao, and J. H. Zhou. Positioning Accuracy Assessment for the
4GEO/5IGSO/2MEO Constellation of COMPASS. Science China — Physics, Mechanics and Astronomy, 55(12):2290–2299, 2012. doi: 10.1007/s11433-012-4942-z .

170

IGS Reference Frame Working Group Coordinator
Report 2012
P. Rebischung1 , B. Garayt2 , X. Collilieux1 , Z. Altamimi1
1

2

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

1 Introduction
The Reference Frame Working Group activities were marked by two main events in 2012.
Firstly, on GPS week 1702 (August 19, 2012), the longstanding weekly IGS SINEX combinations were stopped in favor of henceforth daily SINEX combinations. Secondly, an
update to the IGS08 Reference Frame, called IGb08, was prepared and adopted on GPS
week 1709 (October 7, 2012). The present report reviews these two changes and theirconsequences on the IGS terrestrial frame products.

2 From weekly to daily terrestrial frames
From 1999 to August 18, 2012, the generation of the IGS final products has been basedon the methodology defined by Kouba et al. (1998). During this period, the IGS final
Analysis Centers (ACs) were producing terrestrial frame SINEX solutions based on weekly
data batches, which were combined by the Reference Frame Working Group Coordinatorto form the IGS weekly SINEX solutions (igsyyPwwww.snx). The AC orbit products,
while provided on a daily basis, were supposedly referred to the respective AC weekly
terrestrial frame solutions, as were the IGS combined orbits to the IGS weekly combined
SINEX solutions.
On GPS week 1702 (August 19, 2012), a major change was introduced into this scheme:
the IGS final ACs now produce fully independent daily solutions and deliver in particulardaily terrestrial frame SINEX solutions. The IGS SINEX combinations are thus now also
made on a daily basis. In this section, we review the motives that led to introduce thischange, present the new daily SINEX combination products and show results from thelatest combinations.
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Rebischung et al.: Reference Frame Working Group

2.1 Motivation
The switch from products based on weekly terrestrial frame integrations to products
based on daily terrestrial frame integrations was mainly intended to improve the studyof station position displacements and the correction of position discontinuities. Non–
tidal atmospheric loading (NT–ATML) effects show for instance sub–weekly variability(http://acc.igs.org/reprocess2.html), which was shown to be observable in daily
GPS solutions by Tregoning and Watson (2009). The switch to daily terrestrial framesshould thus allow meaningful interpretation of the IGS station position time series at sub–weekly frequencies. Daily integrations will also allow a better identification of temporary
data outages at GNSS stations, which may partly explain why weekly GNSS station positions do not fit mean NT–ATML modeled displacements as well as an a priori handlingof the NT–ATML effect could do (Dach et al., 2011). It is finally worth noting that theincreased temporal resolution of the IGS station position time series will probably benefit other applications like, for instance, the study of co– and post–seismic displacements(Lercier et al., 2012).

2.2 Daily SINEX combination products
With the switch from weekly to daily SINEX combinations, a number of changes were madeto the nature and naming of the SINEX combination products. Daily combined SINEX
solutions are now provided, as well as daily residual files. The combination summaries
and the ERP files however continue to be provided on a weekly basis. Note that weekly
combined SINEX solutions are still formed, but they now result from a stacking of theseven daily combined solutions. The IGS cumulative solution is still updated weekly bystacking all previous weekly combined solutions. A list of the “official” SINEX combination
products since the switch to daily integrations is given in Tab. 1. Also note that mostof the time series maintained at ftp://igs-rf.ign.fr and ftp://igs-rf.ensg.eu (inparticular station position time series) are now regularly updated with a daily resolution.

2.3 Recent SINEX combination results
As they reflect the level of agreement of AC solutions with each other, the SINEX combination residuals are traditionally used as precision indicators for the combined products.
Figure 1 thus shows the weekly, then daily RMS of the AC station position residuals overyear 2012. The main overall feature in Fig. 1 is a general increase of the residual scatterswith the switch to daily combinations. Such an increase was of course expected from thereduction of the integrationinterval, and the residual scatters could have in fact been√
amplified by a factor 7 ≈ 2.6 if the AC station position time series were consisting ofzero–mean white noise.

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2 From weekly to daily terrestrial frames
Table 1: List of the SINEX combination products since the switch to daily terrestrial frame
integrations (yy=2–digit year; wwww=GPS week; d=day of the week; ww=week of the
year)
File

Description

igsyyPwwwwd.snx
igsyyPwwwwd.ssc
igsyyPwwwwd.res
igsyyPwwwwd_IGS.res
igsyyPwwwwd_ITR.res
igsyyPwwww.snx
igsyyPwwww.ssc
igsyyPwwww.erp
igsyyPwwww.sum
IGSyyPww.snx
IGSyyPww.ssc
igs00p03.erp

Daily combined SINEX solution
Daily combined SINEX solution without covariance matrix
Residuals between daily AC solutions and daily combined solutions
Residuals between daily AC solutions and IGS cumulative solution
Residuals between daily AC solutions and IGS Reference Frame
Weekly combined SINEX solution
Weekly combined SINEX solution without covariance matrix
EOPs extracted from the daily combined SINEX solutions
SINEX combination summary
IGS cumulative solution
IGS cumulative solution without covariance matrix
Accumulated series of combined EOPs<------------------- weekly -------------------><--------- daily --------->
4 mm

East

2 mm

<------------------- weekly -------------------><--------- daily --------->
4 mm

North

2 mm

0 mm

0 mm
1670

1680

1690

1700

1710

1720

1670

1680

1690

1700

1710

1720

<------------------- weekly -------------------><--------- daily --------->
8 mm

Up

4 mm

cod

gfz

mit

emr

grg

ngs

esa

jpl

sio

0 mm
1670

1680

1690

1700

1710

1720

GPS week

Figure 1: RMS of AC station position residuals over year 2012. The switch from weekly to daily
combinations on week 1702 is indicated by the thick vertical black lines. The weekly
part and the daily part of each time series were separately low–pass filtered with a
10 cpy cut–off frequency.

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Rebischung et al.: Reference Frame Working Group
Table 2: RMS of AC station position residuals computed over weeks 1683–1701 and over weeks
1702–1720. Bracketed values are the respective ratios. Ratios larger than 1.5 are indicated in bold.

AC

East

North

Up

cod
emr
esa
gfz
grg
jpl
mit
ngs
sio

0.9 mm → 1.1 mm (1.33)
0.9 mm → 1.1 mm (1.13)
0.9 mm → 1.2 mm (1.31)
0.8 mm → 0.9 mm (1.21)
1.2 mm → 1.8 mm (1.50)
1.0 mm → 1.2 mm (1.14)
0.8 mm → 1.1 mm (1.51)
1.6 mm → 2.6 mm (1.66)
0.9 mm → 1.6 mm (1.78)

1.0 mm → 1.2 mm (1.18)
1.4 mm → 1.4 mm (0.96)
0.9 mm → 1.1 mm (1.23)
0.7 mm → 0.8 mm (1.16)
1.3 mm → 2.3 mm (1.83)
1.1 mm → 1.3 mm (1.18)
0.8 mm → 1.0 mm (1.31)
1.2 mm → 1.9 mm (1.60)
1.3 mm → 1.6 mm (1.23)

3.0 mm → 3.5 mm (1.19)
3.6 mm → 3.1 mm (0.87)
3.0 mm → 3.5 mm (1.18)
2.2 mm → 2.5 mm (1.15)
3.9 mm → 5.9 mm (1.52)
3.8 mm → 4.3 mm (1.13)
2.0 mm → 2.9 mm (1.50)
2.9 mm → 4.5 mm (1.53)
2.7 mm → 3.5 mm (1.31)

To get some insight into the impact of the switch to daily integrations on the precision of
the combined frames, we quantified the factors by which the combination residual scattershave actually increased. For each AC and each East, North and Up component, a global
RMS of residuals was thus computed over GPS weeks 1702–1720 (daily combinations)and compared to another RMS computed over weeks 1683–1701 (weekly combinations).
Results are compiled in Tab. 2. The individual residual√ scatter increase factors are quite
disparate, but mostly under 1.5 and all far below 7 ≈ 2.6 . This means that the gainin temporal resolution is offset by relatively small additional noise on the IGS combined
station positions. But this also points to the presence of biases and/or time–correlated
errors in the AC station position residual time series.
Figures 2 and 3 show the AC EOP residuals over year 2012. The behaviors of the AC pole
coordinate residual time series do not present remarkable changes with the switch fromweekly to daily SINEX combinations. The precision of the IGS combined pole coordinates
thus seems marginally affected by the switch. The overall picture is similar for the ACpole rate residuals. The LOD residuals of most ACs however show an increased high–frequency scatter after the switch to daily combinations and some also seem to show more
pronounced periodic signals. But longer series will be needed to analyze these changes indetail.

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2 From weekly to daily terrestrial frames

xp residuals (mas)
0.1

0.1

0.0
-0.1

0.0

cod

-0.1

0.1

0.0

emr

-0.1

0.1

0.0

esa

-0.1

0.1

0.0

gfz

-0.1

0.1

0.0

grg

-0.1

0.1

0.0

jpl

-0.1

0.1

0.0

mit

-0.1

0.1

0.0

ngs

-0.1

0.1

ngs

0.1

0.0
-0.1

mit

0.1

0.0
-0.1

jpl

0.1

0.0
-0.1

grg

0.1

0.0
-0.1

gfz

0.1

0.0
-0.1

esa

0.1

0.0
-0.1

emr

0.1

0.0
-0.1

cod

0.1

0.0
-0.1

yp residuals (mas)

0.0

sio

-0.1

sio

1670 1680 1690 1700 1710 1720

1670 1680 1690 1700 1710 1720

GPS week

GPS week

Figure 2: AC pole coordinate residuals over year 2012. The switch from weekly to daily combinations on week 1702 is indicated by the thick vertical black lines.

175

Rebischung et al.: Reference Frame Working Groupxp rate residuals (mas/d)

yp rate residuals (mas/d)

0.5

0.5

0.0

0.0

cod

-0.5

-0.5

0.5

0.5

0.0

0.0

emr

-0.5

-0.5

0.5

0.5

0.0

0.0

esa

-0.5

-0.5

0.5

0.5

0.0

0.0

gfz

-0.5

-0.5

0.5

LOD residuals (ms)
0.05
0.00

cod

-0.05

cod

0.05
0.00

emr

-0.05

emr

0.05
0.00

esa

-0.05

esa

0.05
0.00

gfz

-0.05

gfz

0.5

0.0

0.0

grg

-0.5

-0.5

0.5

0.5

0.0

0.0

jpl

-0.5

-0.5

0.5

0.5

0.0

0.0

mit

-0.5

-0.5

0.5

0.5

0.0

0.0

ngs

-0.5

-0.5

0.5

0.5

0.0

0.0

sio

-0.5

-0.5

grg
0.05
0.00

jpl

-0.05

jpl

0.05
0.00

mit

-0.05

mit

0.05
0.00

ngs

-0.05

ngs

0.05
0.00

sio

-0.05

sio

1670 1680 1690 1700 1710 1720

1670 1680 1690 1700 1710 1720

1670 1680 1690 1700 1710 1720

GPS week

GPS week

GPS week

Figure 3: AC pole rate and LOD residuals over year 2012. The switch from weekly to daily
combinations on week 1702 is indicated by the thick vertical black lines.

176

3 IGb08: an update to IGS08

3 IGb08: an update to IGS08
Since the adoption of IGS08 on GPS week 1632 (April 17, 2011; Rebischung at al.,2012), many of the designated reference frame stations have been affected by position
discontinuities which made them become unusable as reference frame stations. The IGS08
core network (a well–distributed sub–network of IGS08 stations used in particular for thealignment of the IGS combined SINEX solutions) has thus progressively become sparser.
A critical situation was reached in late summer 2012, with only about 50 IGS08 corestations remaining usable out of 91. This situation led the Reference Frame Working
Group to prepare an update of IGS08, called IGb08. IGb08 mainly includes new sets ofcoordinates for 33 IGS08 stations having been affected by position discontinuities since2009.5, and 3 new stations co–located with decommissioned IGS08 stations. The various
changes from IGS08 to IGb08 are described in detail in IGSMAIL #6663.
IGb08 was adopted starting with GPS week 1709 (October 7, 2012). Since then, thenumber of core stations used to align the IGS daily combined solutions has ranged between
64 and 70. As an illustration, the core networks used to align the IGS combined solutionsof October 6 and 7 are compared in Figure 4. One can notice a clear improvement of thecore network geometry in Asia, Africa and Oceania. A large area in and around SouthAmerica however remains uncovered. Hopefully, no other update of IGS08 will be needed
before the adoption of a new IGS reference frame based on the next release of ITRF
expected in 2014.

TIXI
TRO1

POL2

BJFS

SCUB
IISC
BRFT

NKLG MAL2
COCO
TOW2
ALIC KOUC

WIND

AUCK
CHTI
DAV1

Figure 4: Core networks used to align the IGS combined solutions of October 6 and 7. Greendots are the 50 IGS08 core stations used to align the combined solution of October
6. Yellow dots are the additional 17 IGb08 core stations used to align the combined
solution of October 7.

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Rebischung et al.: Reference Frame Working Group

References
Dach, R., J. Böhm, S. Lutz, P. Steigenberger, and G. Beutler. Evaluation of the impactof atmospheric pressure loading modeling on GNSS data analysis. Journal of Geodesy,
85:75–91, 2011. doi: 10.1007/s00190-010-0417-z .
Kouba, J., J. Ray, and M. M. Watkins. IGS Reference Frame Realization. IGS Analysis
Center Workshop Proceedings, Darmstadt, Germany, 139–172, 1998.
Lercier, D., Z. Altamimi, X. Collilieux, and C. Vigny. A focus on estimated coseismic
displacements using IGS weekly station positions. IGS Workshop 2012, 23–27 July
2012, Olsztyn, Poland, 2012.
Rebischung, P., J. Griffiths, J. Ray, R. Schmid, X. Collilieux, and B. Garayt. IGS08:
the IGS realization of ITRF2008. GPS Solutions, 16:483–494, 2012. doi: 10.1007/
s10291-011-0248-2 .
Tregoning, P. and C. Watson. Atmospheric effects and spurious signals in GPS analyses.
Journal of Geophysical Research, 114:B009403, 2009. doi: 10.1029/2009JB006344 .

178

Real–Time Working Group and Real–Time Pilot
Project
M. Caissy1 and L. Agrotis2
12Natural Resources Canada, Geodetic Survey Division
615 Booth Street, Ottawa, Canada K1A 0E9
Mark.Caissy@nrcan.gc.ca
European Space Operations Centre

1 Introduction
This Technical Report covers the period beginning January 1, 2012 and ending December
31, 2012. The main focus of the working group and within the pilot project was thecompletion of steps necessary for the pilot project to transition into an official IGS Real–Time Service (RTS). Considerable progress has been made to date towards achieving theend goal of launching the Service,. This report will focus on the main activities of 2012.
The report also illustrates the quality of the Pilot Project products during 2012 — GPS
weeks 1669–1721. The report wraps up with a look at plans for 2013.

2 Main Activities of 2012
Much of the work centered on three key activities:a) Obtaining commitments from Real-Time Pilot Project participants to continue supporting a future RTS and an indication of what level of support could be expected. A
form letter and questionnaire was sent to all participating agencies.
b) Writing an article in a prominent GNSS magazine as part of a communication strategy.
An article entitled “The International GNSS Real-Time Service” appeared in GPS
World’s June Innovation column. (see Further Reading) This article provided both ahistorical perspective of the IGS real-time initiative and described in some detail thearchitecture of the RTS, as well as what users can expect.

179

Caissy and Agrotis: Real–Time Pilot Projectc) Developing a plan of action with tasks to be completed before a service could belaunched. This was the key real-time activity at the IGS Workshop. The plan included
both a list of critical path tasks essential to complete before launch of RTS and an
ASAP list of tasks considered important but not critical for launch. The critical pathconsisted of four items:i) The development of an RTS website. The Central Bureau was chosen to host thesite and the minimum content was identified to be the following:• Description of products (along with intended use)
• Where and how to access products (registration)• Suggested tools (BNC tutorial)• How to use products (RTCM documents)• Product monitoring (availability and quality)ii) Provide real-time analysis centres with access to a redundant broadcast ephemeris
stream.
iii) 5-second clocks from all ACsiv) A Central Bureau NTRIP Caster with a minimum requirement of having:• A registration procedure• Sufficient testing in order to assess the quality of service
Items on the ASAP list included:e) Additional confirmation of support for RTS.
f) Further development and execution of a communication strategy aimed in partat manufacturers who will integrate RTCM State Space Representation (SSR)
support into their firmware.
g) Identify a core set of stations used by RTAC’s in the generation of real-time clocks
so that their stability can be monitored on a daily basis. This has been identified
as an issue that if left unchecked, could lead to problems in the future.

3 The Products
Figures 1 and 2 illustrate the accuracy of the RTS orbit and IGS01 clock products respectively. Figures 3 and 4 illustrate representative positioning results using either IGS01 or
IGS02 RTS correction products.

180

3 The Products

Average 31 (mm) since week 1667

Figure 1: RTS Orbit Comparied to IGS Rapid.

Average rms: 0.25 (ns)Figure 2: IGS01 Clock compared to IGS Rapid.

181

Caissy and Agrotis: Real–Time Pilot Project

2drms = .15 m

Figure 3: Positioning results using IGS01 clock product.

2drms = .15 m

Figure 4: Positioning results using IGS02 clock product.

182

Further Reading

4 Plans for 2013
The goal is to reach full operating capability by the end of the year. Key to reaching
this goal will be the introduction of GLONASS clock and orbit corrections as an official
product. The focus will be on monitoring, improving and expanding the service including
the introduction of additional product distribution centres as needed.

Further Reading
Caissy, M., L. Agrotis, G. Weber, M. Hernandez–Pajares, and U. Hugentobler. The International GNSS Real–Time Service. GPS World, pp. 52–58, 1 June 2012.
Caissy, M. and L. Agrotis. Real–Time Working Group and Real–Time Pilot Project. In
M. Meindl, R. Dach, and Y. Jean, editors, IGS 2011 Technical Reports, IGS Central
Bureau, 2012.

183

Caissy and Agrotis: Real–Time Pilot Project184

RINEX Working Group 2012 Report
K. MacLeod1 , L. Agrotis2 , and R. Dach3
1
2
3

Natural Resources Canada
E–mail: ken.macleod@nrcan.gc.ca
European Space Operations Centre
E–mail: loukis.agrotis@esa.int
Astronomical Institute, university of Bern
E–mail: rolf.dach@aiub.unibe.ch

The RINEX Working Group (RWG) was formed as a partnership between the IGS andthe Radio Technical Commission for Maritime Services, Special Committee 104 (RTCM–
SC 104). Currently the working group consists of about 50 members with the numbers
equally split between the two groups. Within the IGS the RWG performs two roles: oneis the development and documentation of the RINEX data format and the other is torepresent the IGS at the RTCM–SC 104 working group.
During 2012 the RINEX 3.02 draft format was updated to support the Quasi Zenith Satellite System (QZSS) and BeiDou (thanks to valuable contributions from both JAXA andthe BeiDou office). During the past year the working group received requests from RINEX
users for a more general and modern file naming convention. The working group discussed
and developed a draft generic file naming convention and it was presented at both the IGS
Workshop (July 2012) and at RTCM meetings and received general support. The December release of the RINEX 3.02 draft was updated with the new file naming convention.
Over the past couple of years the RTCM–SC 104 has been developing a binary data format
called RTCM–Multiple Signal Format (RTCM–MSM). RTCM–MSM was designed as abinary equivalent to the RINEX 3.01 and 3.0x formats. The design was made as genericas possible so that it could be easily extended to support new signals and constellations.
All RTCM–MSM phase observations are phase aligned as they are in RINEX 3.01 and 3.0x.
The current documentation supports the GPS, GLONASS and Galileo constellations. All
RTCM-MSM observations types (code, phase, Doppler, Signal to Noise Ratio (SNR) andloss of lock) provide measurement resolution suitable for geodetic applications and meet
RINEX 3.0x file standards. After many years of work, in February of 2013, the RTCM
voted on and passed the RTCM–MSM format and associated documentation.

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MacLeod at al.: RINEX Working Group
Summary of the RINEX working group’s tasks completed in 2012:
1. RINEX 3.02 Draft released that supports : GPS, GLONASS, GALILEO, QZSS,
BeiDou and SBAS
2. RINEX 3.02 Draft released, that describes a new generic file naming convention
3. Contributed to the development of the RTCM–MSM format
4. IGS and RTCM–SC 104 presentations

During the 2013 calendar year the RINEX Working Group will focus its efforts on thefollowing tasks:
1. Finalizing the RINEX 3.02 documentation• Submit the RINEX 3.02 documentation to the IGS and RTCM for approval
and adoption• After the RINEX 3.02 documentation has been approved the RWG will work
to gain the support of the RINEX user community• Continue to update and improve the RINEX 3.02 documentation.
• Support and encourage the development of RINEX 3.02 software tools
2. Start the process of defining new RINEX GNSS ephemeris messages to support
CNAV etc.
3. Within the RTCM–SC 104 the RWG will contribute to the development of the following binary messages that would enable the creation of a complete RINEX filefrom either a GNSS receiver stream or an RTCM–MSM file:• Station description (RINEX Header)• Receiver description and state information such as: serial, model and firmware
number and also state information such as temperature, CPU load, number ofsatellite vehicles tracked and station change control mechanism called: Issue ofData Station (IODS).
• Antenna Description: serial and model number and IODS.
• Meteorological Sensor Description and IODS.
• Meteorological observations and IODS.
• The IODS is designed to notify both real-time and file based users that astation’s equipment or software/firmware has changed and that the change
may affect the usability of the observation data.
4. Extension of the RTCM–MSM format to support QZSS and BeiDou.
5. Extension of RTCM–State Space Representation (RTCM–SSR) (GNSS correction
orbit and clock corrections) messages to support Galileo, QZSS and BeiDou.

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6. Additional RTCM–SSR messages to support atmospheric and ionospheric correction
messages: both station and grid types.
7. Development of ephemeris messages to support Galileo, QZSS and BeiDou. Updates
to GPS ephemeris to support CNAV.
8. Development of a position report messages that contains accuracy (variance covariance) information.

187

MacLeod at al.: RINEX Working Group188

The Tide Gauge Benchmark Monitoring Project
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, P. Woodworth, G. Wöppelmann

The Tide Gauge Benchmark Monitoring Project (TIGA) is concerned with the estimationof vertical geocentric positions, vertical motion and displacements of GNSS stations at ornear tide gauges. Geocentric coordinates of tide gauge sensors are necessary for a variety
of applications, ranging from sea level change studies, radar altimetry calibrations, sealevel hazard monitoring, or the establishment of a World Height System (WHS). Morespecifics can be found in (Merrifield et al., 2012). Typical Tide Gauge stations are shownat page 190.
The aims of the TIGA Working Group are:
1. Maintain a global virtual continuous GNSS@TG network• Select a set of tide gauges equipped with GNSS, with a long and reliable history,
useful for both sea level change studies, and e.g. satellite altimeter calibrations.
IGS network operation standards should be applied.
• Promote the establishment of more continuous operating GNSS stations, inparticular in the southern hemisphere.
• Promote the establishment of local ties (leveling) between GNSS and TGBMs.
• Provide meta information, e.g. on leveling between benchmarks or data access.
• Provide training to tide gauge operators through workshops, encourage station
operators to provide necessary metadata. Through Global Sea Level Observing
System (GLOSS) advice station operators about the operation of continuous
GNSS@TG stations.
2. 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.
3. Study the impacts of corrections and new models on the GNSS processing of thevertical. Encourage other groups to establish, e.g. nearby absolute gravity sites.
4. Provide advice to new applications.
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Schöne et al.: Tide Gauge Benchmark Monitoring Project

Figure 1: GNSS-controlled Tide Gauge (Tanahbala, Indonesia)

In this example, the GNSS antenna is mounted on the same construction as the tide gauge.
The leveled difference between the GNSS antenna reference and the tide gauge benchmark
is stable over time. The station coordinates are difficult to use in e.g., reference frame
definitions, since the pier may subside and the environment might cause some multipath.

Figure 2: GNSS–controlled Tide Gauge (Telukdalam, Indonesia)

Here, the GNSS station (red building to the right) is placed on stable ground at a land
station, while the tide gauge is off-shore. The tie is established using classical spirit
leveling.

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GNSS and the other space geodetic techniques are only one tool for the determinationof vertical rates. Establishing ties to absolute gravity sites near tide gauges is strongly
promoted and results will be evaluated as part of the Working Group activities.
Over the past year, the TIGA-WG has prepared the reprocessing of the TIGA network,
which will be parallel to the repro2 campaign of the IGS. The software suites used in TIGA
for reprocessing (Bernese, EPOS Potsdam, GAMIT/GLOBK) have the latest standards,
as agreed during meetings in Olzstyn (June 2012) and San Francisco (December 2012)
implemented. Test data have been circulated between groups to ensure consistency inexchange formats.
Significant progress has been made by the SONEL data center (http://www.sonel.org),
hosted by University of La Rochelle. SONEL acts as a one-stop-shop for GNSS and tidegauge information related to TIGA and to GNSS@TG stations. The portal allows users
to access meta data information and data. Frequent updates and information exchangewith TIGA Data Center hosted by NASA at CDDIS ensures up-to-date information.

Figure 3: The SONEL TIGA data center (University of La Rochelle, France) provides an excellent
access point for meta information. The GNSS date base is synchronized with the TIGA
Data center at CDDIS (NASA, USA).

In cooperation with SONEL, potential TIGA stations and stations with significant data
gaps have been identified. Actions to involve new groups (stations) and to fill data gaps
have been done. Norway provided some missing data (formerly ESEAS stations) and
the German BfG (http://www.bafg.de) agreed to and provided a significant data setof collocated GPS stations from the (German) North Sea offshore area. Also other data
providers have filled gaps in the GNSS data base.
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Schöne et al.: Tide Gauge Benchmark Monitoring Project

Recent TIGA related publications
Fenoglio–Marc, L., T. Schöne, J. Illigner, M. Becker, P. Manurung, C. Khafid. Sea Level
Change and Vertical Motion From Satellite Altimetry, Tide Gauges and GPS in theIndonesian Region. Marine Geodesy, Vol. 35(14), pp. 137–150, 2012.
King, M. A., M. Keshin, P. L. Whitehouse, I. D. Thomas, G. A. Milne and R. E. M. Riva.
Regional biases in absolute sea level estimates from tide gauge data due to residual
unmodeled vertical land movement. Geophysical Research Letters, Vol. 39, L14604,
2012. doi: 10.1029/2012GL052348 .
Merrifield, M., S. Holgate, G. Mitchum, B. Pérez, L. Rickards, T. Schöne, P. Woodworth,G. Wöppelmann, and T. Aarup. Global Sea Level Observing System (GLOSS). Implementation Plan — 2012, UNESCO/IOC, 41pp. (IOC Technical Series No. 100) (English), 2012. http://www.unesco.org/ulis/cgi-bin/ulis.pl?catno=217832&set=
50929BE4_3_465 .
Rudenko, S., N. Schön, M. Uhlemann, and G. Gendt. Reprocessed height time series for
GPS stations. Solid Earth, 4:23–41, http://www.solid-earth.net/4/23/2013/, 2013.
doi: 10.5194/se-4-23-2013 .
Santamaría–Gómez A., M. Gravelle, X. Collilieux, M. Guichard, B. Martín, B. Míguez,
P. Tiphaneau, and G. Wöppelmann. Mitigating the effects of vertical land motion inlong tide gauge records using a state-of-the-art GPS velocity field. Global and Planetary
Change, 98–99:6–17, 2012a.
Santamaría–Gómez A., M.–N. Bouin, and G. Wöppelmann. Improved GPS data analysis
strategy for tide gauge benchmark monitoring. In: S. Kenyon et al. (Eds.), Geodesy
for Planet Earth, International Association of Geodesy Symposia, Vol. 136, 2012b. doi:
10.1007/978-3-642-20338-1_2 .
Wöppelmann, G. and M. Marcos. Coastal sea level rise in southern Europe and the nonclimate contribution of vertical land motion. Journal of Geophysical Research, Vol. 117,
C01007, 2012. doi: 10.1029/2011JC007469 .

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Recent TIGA related publications

TIGA Working Group Members in 2012
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 Griffiths
Carey Noll
Tilo Schöne
Philip Woodworth
Gary Mitchum
Mark Merrifield
Matt King

TAC, TNC, TDC
TAC
TAC

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

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

TAC
TAC
Combination
TAC/CombinationTAC
IGS Central Bureau
IGS AC coordinator
TDC
Chair TIGA-WGPSMSLGLOSS GE (new).
GLOSS GE (past)

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Schöne et al.: Tide Gauge Benchmark Monitoring Project194

IGS Troposphere Working Group 2012
C. Hackman and S. Byram
United States Naval Observatory
3450 Massachusetts Avenue Northwest
Washington DC 20392 USA
e–mail: christine.hackman@usno.navy.mil
phone: 202 762 1428

1 Introduction
The IGS Troposphere Working Group (IGSTWG) 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 (IGSFTE) in 2011.
Dr. Christine Hackman chairs the IGSTWG. Dr. Sharyl Byram oversees production of the
IGSFTEs. Both are part of the GPS Analysis Division (GPSAD) in the Earth Orientation
Department at USNO. GPSAD also hosts the USNO IGS Analysis Center.
The IGSTWG comprises approximately 45 members (cf. Appendix A). A revised charter
approved by the IGS Governing Board (GB) at the close of 2011 is shown in Appendix B.

2 Product Generation/Improvements/Usage 2012USNO produces IGS Final Troposphere Estimates for the 350+ stations of the IGS network. Users downloaded 17.3 million of these files in 2012 (Noll, 2013). Each
24–hr site result file provides five–minute–spaced estimates of total troposphere zenith
path delay (ZPD), north, and east gradient components, with the gradient components
used to compensate tropospheric asymmetry.
IGS Final Troposphere estimates are generated in Bernese GPS Software (developed at
Astronomical Institute, University of Bern, Dach et al., 2007) using precise point positioning (PPP; Zumberge et al., 1997) and the GMF mapping function (Böhm et al., 2006) withIGS Final satellite orbits/clocks and earth orientation parameters (EOPs) as input. Eachsite–day’s results are completed approximately three weeks after measurement collection,that being when IGS Final orbit/clock/EOP estimates become available.

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Hackman and Byram: Troposphere working group
NUMBER OF QUALITY-CHECKED TROPOSPHERE FILES SUBMITTED TO IGSNUMBER OF RECEIVERS FOR WHICH FILES SUBMITTED

350

325

300

275

250

225
0

60

120
180
240
300
DAY OF YEAR OF MEASUREMENTS, 2012

360

Figure 1: Number of quality–checked IGS Final Troposphere Estimate files submitted to the IGS
per measurement day. The number decreased around DOY 60 due to implementation of
more–stringent latency requirements, increased near DOY 110 due to an update of thestation–processing list, and increased further around DOY 260 due to modernizationof the RINEX data import routines.

IGS final troposphere values are viewed as a truth standard by scientists/meteorology
laboratories around the world. Inquiries about the estimates were received in 2012 from,for example, the Russian Hydrometeorological University, the Royal Melbourne Instituteof Technology (AUS), and the Belgian Institute for Space Aeronomy. Processing improvements were made throughout 2012, therefore, towards improving the number of sites forwhich estimates were available, and the quality of those estimates.
Result–screening algorithms were made more stringent toward the end of February. The
list of stations for which processing is attempted was modernized in April. RINEX importroutines were modernized in October. The impact of these improvements on the numberof stations for which troposphere values could be successfully computed is shown in Fig. 1.
110458 station result files were submitted by USNO in 2012, or an average of 301 stations
per measurement day.
The IGS Final Troposphere files can be downloaded from ftp://cddis.gsfc.nasa.gov/
gps/products/troposphere/zpd . Dr. Byram presented a poster detailing computations
and improvements at the IGS 2012 Workshop (Byram and Hackman, 2012).

3 Troposphere Working Group Activities 2012
The working group (WG) had been reorganized in 2011. The chair therefore in early 2012
designed, distributed and analyzed the results of a survey designed to elicit members’ interests, concerns and ability to contribute resources, meanwhile also organizing troposphereplenary (oral), poster and working–group sessions for the July 2012 IGS Workshop.

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3 Troposphere Working Group Activities 2012
The IGS Workshop troposphere plenary and poster sessions showcased a wide variety of
the latest results in GNSS–based atmospheric estimation, featuring oral presentations on
numerical weather modeling, single–frequency–receiver troposphere estimation, and troposphere estimation utilizing both GLONASS and GPS measurements, as well as 17 poster
presentations.
The IGS WG meeting was attended by approximately 40 people. Activities of the past
12 months plus survey results were presented. The surveys had revealed significant member
curiosity about the true accuracy of IGS Final Troposphere Estimates. A proposal was
made therefore to automate comparisons of IGS Final Troposphere Estimates to thoseobtained from other techniques (e.g., VLBI) or analysis centers (ACs).
After discussion, the WG submitted the following recommendation to the IGS Governing
Board:“By the next IGS Workshop, establish automated, on–going comparison of IGS
final troposphere estimates (FTEs) with results from other techniques/ACs
with the goal of establishing the accuracy of IGS FTEs.”
The board accepted the recommendation.
Work began toward this in Fall 2012 and continued through another splinter WG meeting
held in conjunction with the Fall 2012 AGU Meeting (San Francisco, CA). Current projectstatus:1. The WG will model initial efforts (e.g., stations chosen, corrections applied for
non–colocated receivers) after Teke et al. (2011), who performed inter– and intra–
technique troposphere comparisons for the CONT08 VLBI campaign similar to what
we wish to do.
2. The International VLBI Service (IVS; http://ivscc.gsfc.nasa.gov) has agreed
to contribute VLBI–based troposphere estimates.
3. The International DORIS Service (IDS; http://ids-doris.org) has agreed to contribute DORIS–based troposphere estimates.
4. University of New Brunswick and Technical University of Vienna will contributenumerical weather model–based values.
5. Additional GNSS–based regional–network ZTD values may be available if needed(e.g., NICT Japan–Taiwan–Korea network; EUREF network).
6. Inter–technique comparisons will be generated by Dr. Jan Dousa at Geodetic Observatory Pecný (GOP) with operations to be transferred elsewhere when they exceed
GOP capacity.
7. Result files/plots will be hosted at the IGS server.

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Hackman and Byram: Troposphere working group
The WG has set a two–pronged intermediate goal for completion by the European Geosciences Union General Assembly (April 2013). The ideal is to have prototype automatedcomparisons running by then for a few sites. However, achievement of this goal relies
heavily on the efforts of GOP’s Dr. Dousa, who is already quite busy. The backup goal isthus to automate transfer of the input ZTD values (IGS, IVS, numerical weather models,etc.) to a central server from which GOP could download them for processing.

4 Publications
Byram, S. and C. Hackman. Computation of the IGS Final Troposphere Product by the
USNO. IGS Workshop 2012, 23–27 July 2012, Olsztyn, Poland, 2012.
Hackman, C. and S. Byram. IGS Troposphere Working Group 2011. In M. Meindl,
R. Dach, and Y. Jean, editors, IGS 2011 Technical Reports, IGS Central Bureau, pages
211–218, 2012.

5 Working Group Presentations
Hackman, C. IGS 2012 TWG Splinter Meeting. IGS Workshop 2012, 23–27 July 2012,
Olsztyn, Poland, 2012.
Hackman, C. IGS 2012 TWG Splinter Meeting. 2012 Fall Meeting, AGU, San Francisco,
CA, USA, 03–07 December, 2012.
The presentations can be obtained by contacting the author.

References
Böhm, J., A. Niell, P. Tregoning, and H. Schuh. Global Mapping Function (GMF): A New
Empirical Mapping Function Based on Numerical Weather Model Data. Geophys. Res.
Lett., 33(7), L07304, 2006. doi: 10.1029/2005GL025546 .
Dach, R., U. Hugentobler, P. Fridez, M. Meindl (eds). Bernese GPS Software Version 5.0(user manual). Astronomical Institute of University of Bern, Bern, Switzerland, 2007.
Noll, C. Personal communication. 2013.
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, 2011. doi: 10.1007/s00190-010-0434-y .

198

References
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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Appendix A — IGS Troposphere Working Group Members
Name
Ahmed, Furqan
Amirkhani, Mohammad
Bar–Sever, Yoaz
Bevis, Mike
Bosser, Pierre
Braun, John
Byram, Sharyl
Byun, Sung
Calori, Andrea
Chen, Junping
Colosimo, Gabriele
Crespi, Mattia
Dick, Galina
Dousa, Jan
Drummond, Paul
Ghoddousi–Fard, Reza
Guerova, Guergana
Gutman, Seth
Hackman, Christine
Heinkelmann, Robert
Herring, Tom
Hilla, Steve
Hobiger, Thomas
Langley, Richard
Leighton, Jon
Liu, George
Moeller, Gregor
Moore, Angelyn
Negusini, Monia
Nordman, Maaria
Pacione, Rosa
Penna, Nigel
Perosanz, Felix
Pottiaux, Eric
Prikryl, Paul
Rocken, Chris
Santos, Marcelo
Schaer, Stefan
Schön, Steffen
Sguerso, Domenico
Soudarin, Laurent
Teferle, Norman
Tracey, Jeffrey
van der Marel, Hans
Wang, Junhong
Willis, Pascal
Xu, Zong–qiu
Zhang, Shoujian

200

Institution
Univ. du Luxembourg
Islamic Azad Univ. Tehran
JPL
OSU
ENSG/DPTS
UCAR
USNO
JPL
Univ. Roma “La Sapienza”
Shanghai Astronomical
Observatory
Univ. Roma “La Sapienza”
Univ. Roma “La Sapienza”
GFZ
GOP
TrimbleNatural Resources Canada
Univ. Sofia
NOAA
USNO
GFZ
MIT
NGS/NOAA
Natl. Inst. of Info. & Comm.
Tech. (NICT)
Univ. New Brunswick
3vGeomatics
Hong Kong Polytech. Univ.
TU Wien
JPL
Inst. Radioastronomy (IRA);
National Inst. Astrophysics(INAF)
Finnish Geodetic Inst.
ASI/CGS
Univ. Newcastle
CNES
Royal Observ. of Belgium
Communications ResearchCentre, Canada
GPS Solutions
Univ. New Brunswick
swisstopo
Inst. Erdmessung, Leibniz Uni
HannoverLab. Geodesy, Geomatics, GIS;
Univ. Genoa
Collecte Localisation Satellites
Univ. du Luxembourg
USNO
TU Delft
UCAR/NCAR
Inst. Physique du Globe Paris
Liaoning Tech. Univ.
Wuhan Univ.

Country
Luxembourg
Iran
USA
USA
France
USA
USA
USA
Italy
China

email
furqan.ahmed@uni.lu
m.amirkhani2008@gmail.com
yoaz.bar-sever@jpl.nasa.gov
mbevis@osu.edu
pierre.bosser@ensg.eu
braunj@ucar.edu
sharyl.byram@usno.navy.mil
sung.h.byun@jpl.nasa.gov
calori@mendoza-conicet.gob.arjunping.chen@shao.ac.cn

Italy
Italy
GermanyCzech
New Zealand
CanadaBulgaria
USA
USA
Germany
USA
USA
Japan

gabriele.colosimo@uniroma1.it
mattia.crespi@uniroma1.it
dick@gfz-potsdam.dejan.dousa@pecny.cz
paul_drummond@trimble.com
rghoddou@nrcan.gc.ca
guerova@phys.uni-sofia.bg
seth.i.gutman@noaa.gov
christine.hackman@usno.navy.mil
heinkelmann@gfz-potsdam.detah@mit.edu
steve.hilla@noaa.gov
hobiger@nict.go.jp

CanadaCanada/UK
Hong Kong
AustriaUSA
Italy

lang@unb.ca
jonny2vests@gmail.com
lszzliu@polyu.edu.hk
gregor.moeller@tuwien.ac.atangelyn.w.moore@jpl.nasa.gov
negusini@ira.inaf.it

Finland
Italy
UK
FranceBelgium
Canadamaaria.nordman@fgi.fi
rosa.pacione@e-geos.it
nigel.penna@newcastle.ac.uk
felix.perosanz@cnes.fr
eric.pottiaux@observatoire.bepaul.prikryl@crc.gc.ca

USA
CanadaSwitzerland
Germany

rocken@gps-solutions.com
msantos@unb.ca
stefan.schaer@aiub.unibe.chschoen@mbox.ife.uni-hannover.deItaly

domenico.sguerso@unige.it

FranceLuxembourg
USA
Netherlands
USAFranceChina
Chinalsoudarin@cls.fr
norman.teferle@uni.lu
jeffrey.tracey@usno.navy.mil
H.vanderMarel@tudelft.nl
junhong@ucar.edu
willis@ipgp.fr
zongqiuxu@gmail.com
shjzhangwhu@gmail.com

Appendix B — IGS Troposphere Working Group Charter

Appendix B — IGS Troposphere Working Group Charter
IGS TROPOSPHERE WORKING GROUP CHARTERGNSS can make important contributions to meteorology, climatology and other environmental disciplines through its ability to estimate troposphere parameters. Along withthe continued contributions made by the collection and analysis of ground–based receivermeasurements, the past decade has also seen new contributions made by space–based
GNSS receivers, e.g., those on the COSMIC/FORMOSAT mission [1]. The IGS therefore
continues to sanction the existence of a Troposphere Working Group (TWG).
The primary goals of the IGS TWG are to:• Assess/improve the accuracy/precision of IGS GNSS–based troposphere estimates.
• Improve the usability of IGS troposphere estimates.
– Confer with outside agencies interested in the use of IGS products.
– Assess which new estimates should be added as “official” IGS products, andwhich, if any, official troposphere product sets should be discontinued.
• Provide and maintain expertise in troposphere–estimate techniques, issues and applications.

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

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

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

References:[1] Schreiner, W., C. Rocken, S. Sokolovskiy, S. Syndergaard and D. Hunt, Estimates 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.

202