TECHNICAL REPORT2016

EDITORS
ARTURO VILLIGERROLF DACHASTRONOMICAL INSTITUTE
UNIVERSITY OF BERN

International GNSS Service

International Association of Geodesy
International Union of Geodesy and Geophysics

Astronomical Institute, University of Bern
Bern, Switzerland
Compiled in April 2017, by Arturo Villiger, Rolf Dach (Eds.)

Technical Report 2016
IGS Central Bureau
http://www.igs.org

Editors: A. Villiger, R. Dach
Astronomical Institute, University of Bern
Published in May 2017

IGS Central Bureau
Jet Propulsion Laboratory, M/S 238–540
4800 Oak Grove Drive
Pasadena, CA 91109–8099, USA
E–mail: cb@igs.org
Website: http://www.igs.org

IGS Technical Report 2016
ISSN: 2297-8526
ISBN: 978-3-906813-40-0 ;University of Bern, Bern Open Publishing.
DOI:
10.7892/boris.99278
Cite as:Villiger, A., Dach, R. (eds.) (2017). International GNSS Service Technical Report 2016
(IGS Annual Report). IGS Central Bureau and University of Bern; Bern Open Publishing
DOI: 10.7892/boris.99278
Copyright c IGS Central Bureau and Astronomical Institute, University of Bern
This is an open access book licensed under a Creative Commons Attribution 4.0 International license (CC BY 4.0). This license allows anyone to download, share, reuse, reprint, adapt, distribute,
and/or copy the work providing the original authors and source are credited. No permission isrequired from the authors or the publisher. Further details about CC BY licenses are available athttps://creativecommons.org/licenses/by/4.0/

Abstract
Applications of the Global Navigation Satellite Systems (GNSS) to Earth Sciences are
numerous. The International GNSS Service (IGS), a voluntary federation of government
agencies, universities and research institutions, combines GNSS resources and expertiseto provide the highest–quality GNSS data, products, and services in order to support
high–precision applications for GNSS–related research and engineering activities.
This IGS Technical Report 2016 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 and were achieved during 2016.
This report is available in electronic version at
ftp://igs.org/pub/resource/pubs/2016_techreport.pdf.
The IGS wants to thank all contributing institutions operating network
stations, Data Centers, or Analysis Centers for supporting the IGS. All
contributions are welcome. They guarantee the success of the IGS also infuture.

Contents
I

Executive Reports

1

Governing Board

3

G. Johnston

Central Bureau

11

R. Neilan, S. Fisher, G. Walia, D. Maggert, A. Craddock

II

Analysis Centers

19

Analysis Center Coordinator

21

M. Moore, T. Herring, G. Hu

Center for Orbit Determination In Europe

27

R. Dach, S. Schaer, D. Arnold, E. Orliac, L. Prange, S. Sidorov, A. Sušnik,A. Villiger, L. Mervart, A. Jäggi, G. Beutler, E. Brockmann,
D. Ineichen, S. Lutz, A. Wiget, A. Rülke, D. Thaller, W. Söhne,J. Ihde, J. Bouman, I. Selmke, U. Hugentobler

Natural Resources Canada

41

B. Donahue, R. Ghoddousi–Fard, M.A. Goudarzi, Y. Mireault, F. Lahaye

European Space Operations Centre

47

T.A. Springer, I. Romero, W. Enderle, E. Schoenemann, R. Zandbergenv

GeoForschungsZentrum

54

B. Männel, Z. Deng, M. Ge, T. Nischan, A. Brandt, M. Bradke,
M. Ramatschi
Geodetic Observatory Pecný
No report submitted

Centre National d’Etudes Spatiales/Collecte Localisation Satellites

59

F. Perosanz, S. Loyer, F. Mercier, A. Mezerette, H. Capdeville, J.C. Marty

Jet Propulsion Laboratory

65

D. Murphy, N. Amiri, W. Bertiger, S. Desai, B. Haines, D. Kuang, P. Ries,
C. Sakumura, C. Selle, A. Sibois, A. Sibthorpe

Massachusetts Institute of Technology

71

T. Herring

National Geodetic Survey

79

S. Yoon, J. Saleh, G. Sella, S. Hilla, M. Schenewerk, J. Heck, K. Choi
Scripps Institution of Oceanography
No report submitted

United States Naval Observatory

83

S. Byram, V. Slabinski, J. Tracey, J. Rohde

Wuhan University

90

C. Shi, M. Li, Q. Zhao, X. Dai, C. Wang, H. Zhang

EUREF Permanent Network
C. Bruyninx, A. Araszkiewicz, E. Brockmann, A. Kenyeres, T. Liwosz
R. Pacione, W. Söhne, G. Stangl, K. Szafranek, C. Völksen

95

SIRGAS

105

L. Sánchez

III

Data Centers

115

Infrastructure Committee

117

I. Romero

Crustal Dynamics Data Information System

121

C. Noll
Scripps Institution of Oceanography
No report submitted
Institut National de l’Information Géographique et Forestière
No report submitted
Korean Astronomy and Space Science InstituteNo report submitted

IV

Working Groups, Pilot Projects

137

Antenna Working Group139

R. Schmid

Bias and Calibration Working Group
S. Schaer
Clock Products Working GroupNo report submitted

145

Data Center Working Group150

C. Noll

Ionosphere Working Group155

A. Krankowski, M. Hernandez-Pajares, I. Cherniak, D. Roma–Dollase,
I. Zakharenkova, R. Ghoddousi–Fard, Y. Yuan, Z. Li, H. Zhang,
C. Shi, J. Feltens, A. Komjathy, P. Vergados, S. C. Schaer,
A. Garcia–Rigo, J. M. Gómez–Cama

Multi–GNSS Working Group163

P. Steigenberger, O. Montenbruck
Space Vehicle Orbit Dynamics Working GroupNo report submitted

Reference Frame Working Group

171

P. Rebischung, B. Garayt, Z. Altamimi

Real–Time Service

179

A. Rülke, L. Agrotis
RINEX Working GroupNo report submitted

Tide Gauge Benchmark Monitoring Working Group

185

T. Schöne, R. Bingley, Z. Deng, M. Gravelle, J. Griffiths, M. Guichard,
H. Habrich, D. Hansen, T. Herring, A. Hunegnaw, M. Jia, M. King,
M. Merrifield, G. Mitchum, M. Moore, R. Neilan, C. Noll, E. Prouteau,
L. Sánchez, A. Santamaría–Gómez, N. Teferle, D. Thaller, P. Tregoning,
S. Williams, G. Wöppelmann

Troposphere Working GroupS. Byram

188

Part I
Executive Reports

1

IGS Governing Board
Technical Report 2016
IGS in 2016:
The IGS Governing Board Chair Report
G. Johnston
Geoscience Australia

1 Introduction
In 2016, the IGS has continued with a very exciting work program and list of achievementsfrom the IGS participants. This year we have for the first time had an Analysis Centre
Coordinator (ACC) distributed across two centers, Geoscience Australia and MIT, in two
continents hemispheres apart, using combination software operating on Cloud computing
services (Amazon Web Services).
Delivery of core reference frame, orbit, clock and atmospheric products continues strongly.
2016 has also seen further refinement of the Real Time Service with considerable efforts
being targeted towards development of Standards. The transition to multi GNSS also
continues apace within the IGS, with additional Galileo and Beidou satellite launches
bringing those constellations closer to operational status.
In 2016, the IGS had its first workshop to be held outside of North America or Europe,with the Sydney Workshop being held in February 2016 at the University of New South
Wales. This workshop, the first in South East Asia, signaled the stronger involvement ofBeidou and QZSS into the IGS’s GNSS futures.
The review of the Strategic plan which commenced in 2015 continued throughout 2016,
with a revised version ready for publication in early 2017. The revised plan aims torecognize the extensive contribution of the IGS participants, and to encourage strong engagement with a broader stakeholder set that now rely implicitly on IGS products andservices. The Call for Proposals for participation in the IGS / ICG joint Monitoring andAssessment project is a pragmatic example of the IGS being flexible enough to respondto stakeholder requirements. That project aims to utilize existing skills within the IGS

3

IGS Gorverning Board
family to service a new user community as an extension to our current role of providing
world class GNSS expertise. The Call for participation had a strong response including
a proposal from ESA to undertake the Monitoring and Assessment ACC function. Importantly this new joint project ensures the IGS continues to have strong influence with
GNSS system providers. This strong relationship has been developed over many years by
IGS participation in the International Committee on GNSS.
Of course the IGS functions as a service of the International Association of Geodesy(IAG), and a contributor to the Global Geodetic Observing System (GGOS). Accordingly a number of the Governing Board members continue to participate in IAG and
GGOS governance, bureaus, commissions and working groups. Importantly, GB members
also participate in the United Nations Global Geospatial Information Management (UNGGIM) efforts on Geodesy, which aims to enhance the sustainability of the global geodetic
reference frame through intergovernmental advocacy for geodesy. GB members (Neilan,
Ziebart, Enderle, and former GB member Gerhard Beutler) also gave presentations at the
US PNT Advisory Board, influencing at the highest levels in the US government.
By working within the science community through (IAG/IUGG/ICSU) and the Intergovernmental community through ICG / UN GGIM / US PNT AB and others, the IGS
GB is ensuring the IGS retains its strong level of relevance and impact, and therefore
sustainability.

2 The IGS at a Glance
A glance of the IGS is given in Figure 1.

3 IGS Highlights in 2016
3.1 IGS 2016 Workshop – Sydney, Australia
The 2016 IGS workshop was hosted at the University of New South Wales in Sydney,
Australia by Geoscience Australia, Land Information New Zealand, and the University of New South Wales. The workshop had the theme of GNSS Futures, and featured keynote presentations from Todd Humphreys (University of Texas at Austin), Jan
Weiss (UCAR), and John Church (CSIRO), as well as over 50 plenary presentations and
57 posters. Keynotes, presentations, and posters may be viewed on the IGS website:
http://www.igs.org/presents/workshop2016. The 2016 workshop was the first to beheld outside of North America and Europe. It aimed to recognize Australia’s long contribution to the IGS, but also encourage stronger participation by other South East Asian
contributors.

4

3 IGS Highlights in 2016

Figure 1: The IGS at a Glance.

3.2 Planning for Future IGS Workshops
At the Sydney workshop, it was decided to move the workshops to an 18-month cycle,
due to the wealth of topics and quickening pace of technological development in GNSS. It
was agreed that the next workshop would be hosted by IGN in Paris, France in July 2017.
Planning for this workshop is actively underway, and a full summary will be included in
the 2017 report.
At the December 2016 Governing Board meeting, representatives from Wuhan University
presented a well-received proposal to host the 2018 workshop in China. The board agreed
that this would be an excellent location for this workshop, and accepted the proposal. Asa means to inform future workshop organizers, it was also decided that a representativefrom the next hosting organization will have a seat on the previous workshop’s Scientific
Organizing Committee. By doing this, each SOC will have a representative from theprevious and future workshop, as well as representatives from the current workshop. Earlyplanning is also underway for the 2019 workshop which is likely to be held in Boulder,
USA, pending a proposal from UNAVCO.

5

IGS Gorverning Board

4 Membership Growth and Internal Engagement
In 2016, IGS membership reached 337 Associate Members, representing 118 countries.
The 32-member IGS Governing Board guides the coordination of over 200 contributingorganizations participating within IGS, including 106 operators of GNSS network tracking
stations, 4 global data centers, 13 analysis centers, and 4 product coordinators, 28 associate
analysis centers, 23 regional/project data centers, 12 technical working groups, two active
pilot projects (i.e., Multi-GNSS and Real-time), and the Central Bureau.
In order to better engage with its membership and the greater community, the IGS developed and conducted extensive stakeholder surveys throughout the year. This contributed
to the development of the next IGS Strategic Plan, as well as the first Associate Member
meeting, held immediately before the 47th Governing Board meeting in San Francisco,California, USA this past December.

5 ICG Monitoring and Assessment
Participation in the United Nations International Committee on GNSS (UN ICG) was a
key external engagement of the IGS in 2016. Governing Board member Zuheir Altamimi(IGN, France), as co-chair of ICG Working Group on Reference Frames, Timing andApplications led the discussions and collated resulting recommendations at the November
2016 meeting in Sochi, Russia.
Governing Board members also played a central role in developing the GNSS Performance
Monitoring Joint Trial Project with the UN-ICG International GNSS Monitoring andAssessment Task Force, which will be implemented to develop a credible, cooperative
approach to monitoring the performance of the different GNSS.

6 IGS Operational Activities
6.1 Network Growth
The IGS network added 15 stations in 2016, bringing the total number of stations to505. Development of the 166-station Multi-GNSS subnetwork, within the IGS network,
has been driven by the MGEX Project, which develops the IGS capacity to operate withmultiple GNSSs. Similarly, 187 IGS stations are now capable of real-time data streamingin support of the IGS Real-time Project.

6

7 IGS Governing Board Meetings in 2016

6.2 Product Generation and Performance
ACC transition is now managed jointly by Michael Moore of Geoscience Australia and Tom
Herring of the Massachusetts Institute of Technology. Operations are based at Geoscience
Australia in Canberra, Australia. Responsibility for producing the IGS combined products
officially transitioned from NOAA/NGS to Geoscience Australia on 1st January 2016. The
combination software has been moved from a dedicated server to redundant cloud based
servers located in Australia and Europe, and coordination of the IGS product generation
is now done by personnel distributed between GA and MIT.
As an important measure of overall performance, the IGS keeps track of its productavailability, expressed as the percentage of time that the IGS delivers products at thetargeted level. The IGS has had a perfect 100% availability of its core products for eachof the last four years since IGS began tracking this metric.

6.3 Data Management
The IGS data centers manage an approximately 10 Terabyte collection (over 100 million
files) of GNSS and related data for IGS, which is growing at almost 2 Terabytes per year.
These are maintained online for open access by all users.
Each of the four IGS global data centers is typically accessed by around 10,000 regularusers who consume 70-80 Terabytes (about 120 million files) of IGS data and products
per year. There are approximately 20,000 monthly users of the IGS website and relatedresources.

6.4 Standards Development Support
The IGS continues to contribute to the development of international standards related to
GNSS, principally through participation within the RTCM (Radio Technical Commission
for Maritime Service), where IGS leads the RINEX working group, as well as participating
within the standards activities related to real time systems.

7 IGS Governing Board Meetings in 2016
The Governing Board discusses the activities and plans of various IGS components, sets
policies, and monitors the progress with respect to the agreed strategic plan and annual
implementation plan. It is customary to hold two GB meetings during any IGS Workshop –the second of which typically focusing on workshop recommendations and other debriefingfrom the week’s activity.

7

IGS Gorverning Board

7 February 2016
12 February 201617 April 201611 December 2016

46th Governing Board Meeting (1 of 2 sessions),
held prior to the 2016 IGS Workshop
46th Governing Board Meeting (2 of 2 sessions),
held immediately after the 2016 IGS Workshop
Governing Board Business Meeting, held prior to
the 2016 European Geosciences Union meeting
47th Governing Board Meeting, held prior to the2016 American Geophysical Union meeting

Sydney, Australia
Sydney, Australia
Vienna, Austria
San Francisco,California,
United States

8 IGS Advocacy, and External Engagement
8.1 United Nations GGIM Sub-Committee on Geodesy
IGS remains active in engaging with diverse organizations that have an interest in geodetic
applications of GNSS. Notably, the IGS has supported the development of the Global
Geodetic Reference Frame (GGRF) resolution, roadmap, and upcoming implementation
plan within the United Nations (UN) Global Geospatial Information Management (GGIM)
Committee of Experts (http://ggim.un.org). In 2016, the UN further recognized theimportance of a globally-coordinated approach to geodesy by forming a permanent SubCommittee on Geodesy.

8.2 United States PNT Advisory Board
IGS actively engages and participates in the United States National Space-Based Positioning, Navigation, and Timing (PNT) Advisory Board (http://www.gps.gov/governance/
advisory/). Both Central Bureau Director Ruth Neilan (NASA JPL, United States) andformer Governing Board member Gerhard Beutler (AIUB, Switzerland) are members of
this board, which provides advice to the US Government Executive Committee, chaired by
the United States Deputy Secretary of Defense and Deputy Secretary of Transportation.
Beutler gave presentations focusing on Multi-GNSS at both May and December 2016
PNT meetings. IGS Governing Board members are often invited guests of the PNT,
presenting on key contemporary issues as well as reflecting on decades of work. Marek
Ziebart (University College London, United Kingdom) addressed the May PNT meetingon the topic of orbit dynamics, modeling, and timing; and GB member Werner Enderle(European Space Agency/ESOC, Germany) presented on ESA activities related to GNSS
space service volume. IGS collaborators Gerald Bawden (NASA Headquarters, UnitedStates) and John LaBrecque (University of Texas at Austin, United States) also presented
on real-time GNSS for earthquake and tsunami early warning at the December meeting.

89 Outlook 2017

8.3 International Association of Geodesy Executive Participation
The IGS is represented in a variety of roles throughout the geodetic community. Board
member and Central Bureau Director Ruth Neilan and GB member Richard Gross serveas members of the International Association of Geodesy (IAG) Executive Committee, andparticipated in the April 2016 IAG Strategic Planning Retreat at GeoForschungsZentrum(GFZ) in Potsdam, Germany.
IGS Governing Board Members served on the Coordinating Board, Executive Committee,
Consortium, and Science Panel of the IAG Global Geodetic Observing System (GGOS).
Several of these members participated in the annual GGOS Days series of meetings, heldat the Harvard Smithsonian Center for Astrophysics in Cambridge, Massachusetts, UnitedStates.

8.4 Communications Development and GuidanceCommunications, advocacy, and public information activities were developed in 2016,
including a communications interest and development session held 17 April prior to the
EGU in Vienna, and a pilot associate member and working group open meeting held 11
December prior to the AGU in San Francisco.
Governing Board members, supported by the Central Bureau, played an active role in thedevelopment and distribution of two extensive strategic planning surveys. Responses fromthese surveys, provided by IGS members as well as external stakeholders, helped shape
the upcoming Strategic Plan and provided insight as to pathways for better member
engagement.
Web and printed content continue to be developed and refreshed. A new “IGS Spotlight”
campaign was developed by the Central Bureau in collaboration with Governing Board
members. This “Spotlight” news campaign features news pieces and articles of varying
length and topic, and are meant to illustrate how an organization uniquely benefits fromparticipating in, and contributing to, the IGS. It is also an opportunity for IGS contributing organizations to celebrate accomplishments made possible by their work with
the IGS.

9 Outlook 2017
In 2017 the momentum will continue to build for the IGS towards the Paris Workshop
whose theme will be “Pathways towards Improved Precision”. The workshop will be agreat opportunity to bring the IGS community together in beautiful Paris, and to workthrough the many achievements and emerging challenges of the IGS working groups. With
the Workshop being in Europe a focus on Galileo development will feature as well. The

9

IGS Gorverning Board
IGS will continue to be challenged by the growing stakeholder expectations for improved
product timeliness, fidelity and diversity. Continued efforts by the GB to enhance advocacy
for the IGS are needed. Accordingly presentations at a variety of forums including EGU,
China Satellite Navigation Conference (CSMC), IAG–IASPI Joint Scientific Assembly,
and AGU just to mention few will be delivered by GB members. Strong participation in
the ICG and UN GGIM will also ensure recognition of the important role the IGS plays
in modern society is achieved.
Lastly, 2017 will see several working groups change their chairs as terms end or people
move on. The GB thanks all participants within the IGS for the efforts, with particular
thanks going to those chairs ending their current terms. Without the contributions of all
the IGS could not have achieved the significant outcomes detailed in this report.

10Central Bureau
Technical Report 2016
R. Neilan1 (Director),
S. Fisher1 , G. Walia1 , D. Maggert2 , A. Craddock3
1
2
3

NASA Jet Propulsion Laboratory, California Institute of Technology
UNAVCO
Columbus Technologies

1 Introduction
The mission of the IGS Central Bureau (CB) is to provide continuous management andtechnology in order to sustain the multifaceted efforts of the IGS in perpetuity. It functions
as the executive office of the service and responds to the directives and decisions of the
IGS Governing Board. The CB coordinates the IGS tracking network and operates theCentral Bureau Information System (CBIS), the principal information portal where the
IGS web, ftp and mail services are hosted.
The CB also represents the outward face of IGS to a diverse global user community, as
well as the general public. The CB office is hosted at the California Institute of Technology/Jet Propulsion Laboratory, Pasadena, California, USA. It is funded principally by
the United States National Aeronautics and Space Administration (NASA), which generously contributes significant staff, resources, and coordination to advance the IGS and its
mission. The following report highlights progress made by the Central Bureau in 2016.

2 Executive Management and Governing Board Participation
Governing Board (GB) meetings were held in February (Sydney), April (Vienna), andDecember (San Francisco) 2016. The Executive Committee (EC) met additionally byteleconference approximately every other month. Staff of the Central Bureau, as part ofits work program to carry out the business needs of the IGS, implemented actions definedby the Governing Board throughout the year. In 2016, this included a thorough analysis
and refresh of the IGS Terms of Reference, which may be viewed with other guiding

11

IGS Central Bureau
documents on the knowledge base section of the IGS website: http://kb.igs.org/hc/
en-us/sections/200369273-Guiding-Documents.
The CB supported the ongoing collection of Associate Member applications and nominations, ultimately resulting in the GB decision to form a standing associate member committee, to be chaired by S. Fisher. The IGS Associate Members form the body of voters who
elect the Governing Board, and play a vital role in the ongoing success and sustainabilityof the service. Associate Member and Governing Board Member lists are maintained by
the CB and viewable on the IGS website: http://igs.org/about/organization.
The CB also continues to play an active role in supporting the organization of regular
IGS Workshops, participating in and guiding preliminary meetings of both local and scientific organizing committee members for the 2017 Paris workshop. These meetings took
place in person in April (Vienna) and December (San Francisco) as well as via email andteleconference throughout the year.

3 Network Coordination

Figure 1: IGS Network, 505 Stations (igs.org/network).

There are 505 stations tracking stations participating in the IGS network. The development of a multi-GNSS sub-network with the greater IGS network is led by the MGEX

12

5 Web Development and Information Technology Support
project, which develops the IGS’s capability to operate with multiple GNSS constellations, and has 177 multi-GNSS capable (GPS+GLONASS+one other) stations. Within
the network, 189 IGS stations are now capable of real-time data streaming in support of
the IGS Real-Time Service.
In 2016, 24 stations were added and 12 were decommissioned. During the course of theyear 59 equipment models were added to the rcvr_ant.tab file. The Site Log manager iscurrently supporting over 90 users. In 2016 the network coordinator supported 447 site
metadata updates.

4 Strategic Planning and ProgressThroughout mid-2016, the Central Bureau led the development and distribution of strategic planning-themed surveys to both the IGS community as well as the broader IGS
stakeholder community. Feedback was collected and analyzed by the CB and GB during
the Strategic Plan development process, and used to shape the goals and objectives of the
2017-2020 Strategic Plan.
The 2017-2020 strategic plan development built upon the momentum of the 2015 December Governing Board Meeting, where a preliminary work plan and timeline for writing
the new strategic plan was developed. Meetings dedicated to strategic planning took
place in February (Sydney), April (Vienna), August (New York) and again after the 2016
Governing Board meeting in December (San Francisco). Feedback from GB members
was requested and received throughout the year – to the great benefit of the planning
process.
A preliminary draft of the new strategic plan was distributed prior to the December
meetings, and is in final development phase. It is anticipated that the plan will be officiallypublished in time for the 2017 IGS Workshop in Paris.
Formal benchmarking of progress made in advancing the IGS mission has continued since2012. Metrics indicating performance on defined objectives are tracked annually by the CB
and published on the IGS website: http://kb.igs.org/hc/en-us/sections/200623533.
The IGS has continued through 2016 to exceed targeted product availability (the IGS’s
most important measure of success), including through the transition of Analysis Coordination responsibilities from NOAA/NGS to Geoscience Australia (GA) where availability
was unaffected.

5 Web Development and Information Technology Support
In addition to administration and general support of CBIS operation, the Central Bureau
has continued moving IT services to external cloud hosted servers, in order to facilitate

13

IGS Central Bureau
global access. This year, web, mail, and ftp, as well as an archived copy of the IGSCB
website, were all moved to cloud servers. ACC combination software was also moved froma dedicated server to redundant cloud-based servers located in Australia and Europe,with coordination of the IGS products generation carried out by personnel at Geoscience
Australia (GA) and the Massachusetts Institute of Technology (MIT).
The IGS website, http://IGS.org, has been enhanced to include working group subdomains, which enable working group membership to manage their own content in addition
to working with CB development and communications staff. IGS Contributing Organizations will also be provided with editable pages in IGS.org so that they may take an activerole in best communicating their individual contributions to, and benefit from, the service.
All other references to the old IGSCB website have been redirected to or reestablished on
IGS.org or the IGS Knowledge Base.
Content and resources in the IGS Knowledge Base, http://kb.igs.org, continue to beenhanced and expanded. The Knowledge Base also serves as a task tracking and ticketing platform for Central Bureau projects and work, as well as user feedback and requests.
Comments, suggestions, and other feedback are now welcomed through standardized “contact us” and “feedback” forms, whose links are available at the food of each page on IGS.org.
The Real-Time Service account application has also been updated to a similar form, andautomated to expedite user access.
IGS social media has also been integrated throughout the website, to facilitate sharable
content and optimize engagement with IGS stakeholders. IGS audio-visual resources, madeavailable through IGS Presents, were upgraded to include media plug integration. Workshop resources, including images, posters, presentation slides, and videos, also continue tobe made available on IGS Presents.

6 Communications, Advocacy, and Public Information
The Central Bureau continued to develop communications, advocacy, and public information initiatives on behalf of the Governing Board. Pilot sessions for a number of member
engagement activities were held in 2016, including communications interest and development sessions as well as enhanced associate member outreach and a dedicated associate
member meeting.
An open communications interest session was held prior to the April Governing Board
business meeting in Vienna, and was attended by GB members, the Global Geodetic
Observing System (GGOS) Coordinating Office, and associate members. The next session
is scheduled to be held as a formal splinter session at the 2017 IGS Workshop.
In response to feedback from the strategic planning survey, an inaugural IGS Associate
Member and Working Group Meeting was held the morning prior to the December Governing Board meeting in San Francisco. The meeting was open to all associate members

14

7 Project Support, Committee and Working Group Participationand observers, and featured presentations by working group chairs and other IGS components. Future such sessions, targeted at engaging the associate membership, will beplanned in conjunction with major conferences, such as AGU, EGU, and IAG symposia,
among others.
The Central Bureau actively works with other IAG components to promote communications and outreach, including the IAG Communications and Outreach Branch and GGOS
Coordinating Office. As representatives of the IAG, IGS CB members also participate
actively in the United Nations Initiative on Global Geospatial Information Management(GGIM) Sub-Committee on Geodesy, Focus Group on Outreach and Communications.
Social media has been actively maintained by CB staff and grew significantly in 2016,
due in part by establishing links to IGS Contributing Organization communications representatives and increased frequency of posting, as well as enhanced content. Increased
cross-linking with IGS website and knowledge base content, as well as promoting video
resources available at IGS/presents, will continue in 2017.

7 Project Support, Committee and Working Group
Participation
The Central Bureau participated within the IGS Working Groups and Projects through2016 by:• helping to fold in the MGEX stations within IGS the IGS network which now has
177 stations with GPS, GLONASS and at least one other GNSS
• preparing site metadata systems for RINEX 3 adoption, and supported MultiGNSS
station operators with transition to RINEX3• maintaiing a Real-time caster and supporting the Real-time Service transition to fullcapability, coordinated with UCAR/COSMIC to host a new caster• handling specific information technology needs during the ACC transfer to Geoscience Australia,• developing the IGMA activity within ICG and IGS• and supporting related working group web content.

In addition, the CB and Infrastructure Committee Chair met by teleconference roughly
once per month on a range of station and infrastructure management issues.

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IGS Central Bureau

8 IGS User Support
The Central Bureau continues to devote considerable effort to the IGS community andusers of its products. As measure of this, the CB tracks email traffic through the CB maillist. This traffic has increased by 54% in 2016 to about 6100 messages, though much of
the increase is from notification emails from various CBIS processes that do not require
response.
User support and other community inquiries have been received through a support trouble
ticketing system, which also now receives and automatically creates support tickets fromemails sent to cb@igs.org. Because of this, the number of tickets increased to approximately 1800, though this includes notifications and updates that are sent to the CB email
address. The IGS Knowledge Base has also been continually developed and enhanced
for user support, based on user feedback as well as the regular addition of content andresources.

9 External Participation
The Central Bureau participates in, and interacts with, many IGS stakeholder organizations. A continuing highlight is the CB staff activity within the United Nations GGIM
Sub-Committee on Geodesy (formerly Global Geodetic Reference Frame Working Group).
At the most recent session of the GGIM in New York (August 2016), the working group wasestablished as a permanent sub-committee on geodesy, to provide stability and long-termplanning for the Global Geodetic Reference Frame (GGRF). The Committee of Experts
also endorsed the GGRF Roadmap, which addresses each of the key areas of action described in the operational paragraphs of the 2015 UN General Assembly resolution, at
this session. These efforts are anticipated to open additional avenues for international
cooperation for the IGS and geodesy in general. For more information, please visit the
UN-GGIM website: http://ggim.un.org/UN_GGIM_wg1.html.
Significant progress was also made in supporting the development of a cooperative planwith the United Nations Office for Outer Space Affairs (UNOOSA), International Committee on Global Navigation Satellite Systems (ICG) to monitor performance and interoperability metrics between the different GNSSs, which is now embodied by a joint IGS-ICG
working group on monitoring and assessment.
The CB Director and staff members have continued to represent the IGS the within IAG
service committees and boards, including R. Neilan, the Vice-Chair of the Global Geodetic
Observing System, who serves on the GGOS Executive Committee, as well as on the GGOS
Coordinating Board as IAG Service Representative.
The CB Director also ensured ongoing IGS engagement and participation in the US Federal Advisory Board for Space-based Position, Navigation and Timing, where she serves16

10 Publications
as the appointed NASA representative. Other IGS representatives presenting at thePNT Advisory Board meetings in 2016 include Professsors Gerhard Beutler (Universityof Bern, Switzerland) and Marek Ziebart (University College London, UK), Werner Enderle (ESA/ESOC, Germany), as well as Gerald Bawden and John LaBrecque (NASA,USA). To view presentations made at PNT Advisory Board meetings, please visit: http://www.gps.gov/governance/advisory/. Table 1 provides a listing of the principal external meetings attended by CB staff during 2016.

10 Publications
IGS 2015 Technical Report section, IGS website
NASA SGP/ICPO annual progress report, NASA internal publication
GGOS Bureau of Networks and Operations Report
GGOS Days IGS Update Report

17

IGS Central Bureau

Table 1: Principal meetings attended by CB staff and role/outcomes
MeetingMonth

Location

PurposeNASA HQ ProgrammaticInteractions

Jan.

Washington, DC

Programmatic meetings at NASA HQ

IGS Workshop

Feb.

Sydney, NSW,AUS

Coordinate and support the regular assembly of the
global IGS community

UCAR/UNAVCO meetings

Mar.

Boulder, CO

Programmatic meetings at UNAVCO and UCAR insupport of partner efforts at each organization

IGS Governing Board andApr.

Vienna, AUT

Support of ongoing essential IGS other meetingsbusiness items, strategic planning, andand organizational management

UNOOSA committee meetings Apr.

Vienna, AUT

Participate in working group meetings for GGRF

PNT Advisory Board

Washington, DC

Participate as the NASA respresentative to theadvisory board

ICG Working Group S meeting Jun.

Vienna, AUS

Represent IGS on working group and IGMA
activities

UCAR/UNAVCO meetings

Jul.

Boulder, CO

Programmatic meetings at UNAVCO and UCAR
in support of partner efforts at each organization

United Nations GGIM
Committee of ExpertsAug.

New York, NY

Participate as US and IAG delegate to the UN
GGIM CoE, participate in GGRF WG meetings

University College London

Aug.

London, UK

Meet with representatives of UCL regarding
agreements and future support of the IGS

Bundesamt für Eich- undVermessungswesen (AustrianFederal Agency for
Metrology and Surveying)

Aug.

Vienna, AUT

Meet with the new GGOS Coordinating Office staff
to facilitate progress in their new role, lead web
redevelopment efforts, and guide other communications and organizational development work.
Coordinate with representatives from the German
Federal Agency for Cartography and Geodesy.

GGOS Days Meetings

Oct.

Boston, MA

Participate in GGOS Consortium, Coordinating Board,and Focus Area meetings on behalf of the IGS

PNT Advisory Board

Dec.

Redondo Beach,
CA

Participate as the NASA respresentative to theadvisory board, support local organization of themeeting and additional activities.

IERS DB Meeting

Dec.

San Francisco

In lieu of participating, coordinated with AC and RF
coordinators to participate in meeting for IGS

IGS Governing Board,
Associate Member, andsplinter meetings

Dec.

San Francisco

Coordinate and support meetings of the IGS
Governing Board, Associate Members, Workshop
Planning Committees, and Strategic Planning

GGOS Bureau of Networks
and Observations

Dec.

San Francisco

Represent IGS, support IGS Chair in participation
throughout the meeting.

18

May

Part II
Analysis Centers

19

Analysis Center Coordinator
Technical Report 2016
M. Moore1 , T. Herring2 , G. Hu1
1
2

Geoscience Australia
acc@igs.org
MIT

1 Introduction
Since January 2016 Geoscience Australia and MIT have taken over the role of the Analysis Centre Coordinator (ACC). The ACC provides an oversight on the products that
contribute to the IGS combined solution, by controlling which centres are weighted in the
combination.

2 ACC activities in 2016
For the first time the service of combining the IGS products was placed into the Amazon Web Service cloud environment. The system is designed to run in two potential
regions Frankfurt and Sydney. Moving the system to the cloud reduces the potential for
disruptions of service due IT infrastructure issues commonly experienced at institutionalorganisations.
An effort was made to begin converting the combination code from one which was reliant
on the Lahey fortran compiler to a code base that could be compiled by a generic compiler
such as gfortran. Upon successful completion, this will allow access to more advanced cloudfeatures currently not utilized, and hopefully an easier development path. This project
has not been completed, the results obtained using a different compiler did not agree closeenough to the results obtained from the Lahey compilation. The main issue that needs tobe resolved is within the code used to compute the clock combination. This is of concern
to us and will need to be revisited. We need to determine if there is an underlying issue,or if there is an error made in the the adaptation of the code to be compilable by gfortran.
The operational code used to compute the clock combination is still based on the originalcode base compiled with Lahey, with minor adaptations for IGS14. On Tuesday December21

3 Product Quality and Reliability
13 th an IGS Analysis meeting was held in parallel to the AGU conference. During thismeeting Jake Griffiths presented the results from the combination of the products fromsecond reprocessing effort. The repro2 orbit and clock combinations was completed by
Jake Griffiths. These products are available from CDDIS under:
ftp://cddis.gsfc.nasa.gov/gps/products/WWWW/repro2
The recommendation is to not use the combined IGS clock solution for long term PPP
analysis, as the quality of the product appears to have degraded compared to repro1. For
more details see Jake Griffith’s poster presented at AGU ( http://acc.igs.org/repro2/
griffiths_ig2.pdf ).
Earlier in the week the IERS had meet, and endorsed a transition to IGS14. Following
this endorsement, the IGS analysis centres agreed upon a transition date to ITRF2014 to
be in line with products generated for GPS week 1934 and onwards.

3 Product Quality and Reliability
For 2016, with the exception of a few unusual delays, delivery of all IGS products was
generally uninterrupted.

3.1 Combined orbit quality
Inter–AC agreement of the Final orbit products remains within 5 mm with precision ranges
3-4 mm (1D error). At the individual analysis centre level, ESA agreement improved after
their box wing modelling was removed from the block IIF satellites (as well as the solar
radiation pressure and earth albedo for the box) at week 1892 (see pink line of Figure 1).
Since the implementation of IGS14 (see pink line of Figure 2), ESA now has markedly
improved it agreement with the IGS final combination scale. Since the implementation of
IGS14 JPL has requested their solution to be used for comparison only. Subsequently thesolutions from JPL and EMR are not agreeing as closely to the final IGS combination.
Once JPL have completed a reprocessed time series consistent with IGS14, then we will
look at re-weighting their solutions into the combination. As EMR are basing their final
solution on Gipsy, we will likely see a closer agreement of JPL and EMR to the final
combined solutions.
Wuhan’s rapid solution, since week 1928, now closely agrees with the IGS combined solutions (see grey line of Figure 3). If this performance is maintained we will look at weight
Wuhan’s contribution for the rapid products.
There have been a few issues with the clock alignment with UTC, on two occasions thishas exceeded 20 ps (see Figure 4). There is an increase in the standard deviation with thealignment, and a tendency to drift since 2016. We are currently investigation on how thiscan be improved with Michael Coleman.
22

3 Product Quality and Reliability
COD
EMR
ESA
GFZ
GRG
JPL
MIT
NGS
SIO
IGR

Final Orbits (AC solutions compared to IGS Final)
50(smoothed)Weighted RMS [mm]

40

30

20

10

0
1880

1890

1900

1910

1920

1930

Time [GPS weeks]

1940

Geoscience Australia/MIT, 15.03.2017 02:11 (GMT)

Figure 1: Smoothed WRMS of Final orbits
COD
EMR
ESA
GFZ
GRG
JPL
MIT
NGS
SIO
IGR

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

Orbit scale [ppb]

0.5

0.0

-0.5

-1.0
1880

1890

1900

1910
Time [GPS weeks]

1920

1930

1940

Geoscience Australia/MIT, 15.03.2017 02:11 (GMT)

Figure 2: Scale of AC solutions wrt to Final combination23

3 Product Quality and Reliability
COD
EMR
ESA
GFZ
IGA
JPL
NGS
SIO
USN
WHU
IGC**
IGU**

Rapid Orbits (AC solutions compared to IGS Rapid)
50(smoothed)Weighted RMS [mm]

40

30

20

10

0
1880

1890

1900

1910

1920

1930

Time [GPS weeks]

1940

Geoscience Australia/MIT, 15.03.2017 05:37 (GMT)

Figure 3: Smoothed WRMS of Rapid orbits

3.2 Events Impacting Product Quality and Reliability• Number of core IGS stations exceeded 200 causing rapid product failure, and the
combination software had to be re-dimensioned to accommodate a larger network.
• Clock alignment issues exceeding 20 ps.

• Ultra rapid failure associated with a problem parsing a priori ERP values• Corrupt orbit weight file delayed the submission of an IGS final product• Sporadic errors in the GPS and GLONASS broadcast files have caused delays in the
Final GLONASS products, and delayed rapid products.
Starting from the implementation of IGS14, the procedure in Bernese used to compute thelong arcs to generate the orbit statistics has been changed. The procedure now estimates
twice and four times per revolution in D, with stochastic impulses at 2 hour intervals
for all satellites. This has allowed the modelling a greater degree of freedom to fit thesubmitted ACs orbit models. The statistics have changed from an rms at the 3 cm level,to an rms fit of below 1 cm.

24

3 Product Quality and Reliability

40

30

20

IGR Alignment (ns)

10

0

−10

−20

−30

−40

200

7

200

8

200

9

201

0

201

1

2
201
Date

201

3

201

4

201

5

201

6

201

7

Figure 4: Rapid clock alignment with UTC

25

4 Activities planned for 2017

4 Activities planned for 2017
• Investigate the current modelling applied by ACs.

• Determine if a common attitude model should be applied, or a method to report theattitude estimates from each AC should be used.
• Encourage further investigation into orbit modelling issues, particularly for Block
IIF satellites.
• Review the IGV products to see if these can be moved closer to production status.
• Review the clock combination procedure currently implemented.

• Confirm/adapt the combination software to handle SP3-D format.
• Increase statistical plots available from ACC website:– Plot statistics for each satellite– Plot weight of AC contributions through time
– Plot clock statistics from clock combination and alignment

26

Center for Orbit Determination in Europe (CODE)
Technical Report 2016
R. Dach1 , S. Schaer2 ,D. Arnold1 , E. Orliac1 , L. Prange1 , S. Sidorov1 , A. Sušnik1 , A. Villiger1 ,L. Mervarta , A. Jäggi1 , G. Beutler1 ,E. Brockmann2 , D. Ineichen2 , S. Lutz2 , A. Wiget2 ,A. Rülke3 , D. Thaller3 , W. Söhne3 , J. Ihde3 , J. Bouman3 ,I. Selmke4 , U. Hugentobler4
12
34

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

1 The CODE consortium
CODE, the Center for Orbit Determination in Europe, is a joint venture of the following
four institutions:• Astronomical Institute, University of Bern (AIUB), Bern, Switzerland• Federal Office of Topography swisstopo, Wabern, Switzerland• Federal Agency of Cartography and Geodesy (BKG), Frankfurt a. M., Germany• Institut für Astronomische und Physikalische Geodäsie, Technische Universität
München (IAPG, TUM), Munich, Germany
The operational computations are performed at AIUB, whereas IGS–related reprocessing
activities are usually carried out at IAPG, TUM. All solutions and products are generated
with the latest development version of the Bernese GNSS Software (Dach et al. 2015).
aInstitute of Geodesy, Czech Technical University in Prague, Czech Republic

27

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

2 CODE products available to the public
A wide range of GNSS solutions based on a rigorously combined GPS/GLONASS dataprocessing scheme is computed at CODE. The products are made available through anonymous ftp at:
ftp://ftp.unibe.ch/aiub/CODE/ or http://www.aiub.unibe.ch/download/CODE/
An overview of the files is given in Table 1.
Within the table the following abbreviations are used:yyyy Year (four digits)
ddd
Day of Year (DOY) (three digits)yyYear (two digits)
wwww
GPS Week
yymm Year, Monthwwwwd GPS Week and Day of week
With GPS week 1706,
CODE started to generate a pure one–day solution (label “COF”) in addition to the traditional
three–day long–arc solution (label “COD”). The
result files from both series are submitted to the
IGS data centers hosting
the products. The related files are listed inTable 2.

GNSS
GPS only

Figure 1: Network used for the GNSS final processing at CODE by

The network used by
the end of 2016.
CODE for the final processing is shown in Figure 1. Almost 80% of the stations support GLONASS (red stars).

Referencing of the products
The products from CODE have been registered and should be referenced as:• Dach, Rolf; Schaer, Stefan; Arnold, Daniel; Prange, Lars; Sidorov, Dmitry; Sušnik,Andreja; Villiger, Arturo; Jäggi, Adrian (2016). CODE ultra-rapid product series
for the IGS. Published by Astronomical Institut, University of Bern. URL: http://www.aiub.unibe.ch/download/CODE; DOI: 10.7892/boris.75676.1 .
• Dach, Rolf; Schaer, Stefan; Arnold, Daniel; Prange, Lars; Sidorov, Dmitry; Sušnik,Andreja; Villiger, Arturo; Jäggi, Adrian (2016). CODE rapid product series for the
IGS. Published by Astronomical Institut, University of Bern. URL: http://www.
aiub.unibe.ch/download/CODE; DOI: 10.7892/boris.75854.1 .
28• Dach, Rolf; Schaer, Stefan; Arnold, Daniel; Prange, Lars; Sidorov, Dmitry; Sušnik,2 CODE products available to the public
Andreja; Villiger, Arturo; Jäggi, Adrian (2016). CODE final product series for the
IGS. Published by Astronomical Institut, University of Bern. URL: http://www.
aiub.unibe.ch/download/CODE; DOI: 10.7892/boris.75876.2 .
• Prange, Lars; Orliac, Etienne; Dach, Rolf; Schaer, Stefan; Arnold, Daniel; Jäggi,Adrian (2016). CODE product series for the IGS MGEX project. Published by Astronomical Institut, University of Bern. URL: http://www.aiub.unibe.ch/download/
CODE_MGEX; DOI: 10.7892/boris.75882 .
• Steigenberger, Peter; Lutz, Simon; Dach, Rolf; Schaer, Stefan; Jäggi, Adrian (2014).
CODE repro2 product series for the IGS. Piblished by Astronomical Institut, Uni-

Table 1: CODE products available through anonymous ftp.
CODE final products available at ftp://ftp.unibe.ch/aiub/CODE/yyyy/
yyyy/CODwwwwd.EPH.Z
yyyy/CODwwwwd.ERP.Z
yyyy/CODwwwwd.CLK.Z
yyyy/CODwwwwd.CLK_05S.Z
yyyy/CODwwwwd.SNX.Z
yyyy/CODwwwwd.TRO.Z
yyyy/CODGddd0.yyI.Z
yyyy/CODwwwwd.ION.Z
yyyy/CODwwww7.SNX.Z
yyyy/CODwwww7.SUM.Z
yyyy/CODwwww7.ERP.Z
yyyy/COXwwwwd.EPH.Z
yyyy/COXwwww7.SUM.Z
yyyy/CGIMddd0.yyN.Z
yyyy/P1C1yymm.DCB.Z
yyyy/P1P2yymm.DCB.Z
yyyy/P1P2yymm_ALL.DCB.Z
yyyy/P1C1yymm_RINEX.DCB
yyyy/P2C2yymm_RINEX.DCB

CODE final GNSS orbits
CODE final ERPs belonging to the final orbits
CODE final clock product, clock RINEX format, with a sampling of
30 sec for the satellite and reference (station) clock corrections and5 minutes for all other station clock corrections
CODE final clock product, clock RINEX format, with a sampling of
5 sec for the satellite and reference (station) clock corrections and5 minutes for all other station clock corrections
CODE daily final solution, SINEX format
CODE final troposphere product, troposphere SINEX format
CODE final ionosphere product, IONEX format
CODE final ionosphere product, Bernese format
CODE weekly final solution, SINEX format
CODE weekly summary file
Collection of the 7 daily CODE-ERP solutions of the week
CODE final GLONASS orbits (for GPS weeks 0990 to 1066;
27-Dec-1998 to 17-Jun-2000)
CODE weekly summary files of GLONASS analysis
Improved Klobuchar–style ionosphere coefficients, navigation RINEX
formatCODE monthly P1−C1 DCB solution, Bernese format,
containing only the GPS satellites
CODE monthly P1−P2 DCB solution, Bernese format,
containing all GPS and GLONASS satellites
CODE monthly P1−P2 DCB solution, Bernese format,
containing all GPS and GLONASS satellites and all stations used
CODE monthly P1−C1 DCB values directly extracted from RINEX
observation files, Bernese format, containing the GPS and GLONASS
satellites and all stations used
CODE monthly P2−C2 DCB values directly extracted from RINEX
observation files, Bernese format, containing the GPS and GLONASS
satellites and all stations used29

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

Table 1: CODE products available through anonymous ftp (continued).
CODE rapid products available at ftp://ftp.unibe.ch/aiub/CODE
CODwwwwd.EPH_M
CODwwwwd.EPH_R
CODwwwwd.EPH_P
CODwwwwd.EPH_P2
CODwwwwd.EPH_5D
CODwwwwd.ERP_M
CODwwwwd.ERP_R
CODwwwwd.ERP_P
CODwwwwd.ERP_P2
CODwwwwd.ERP_5D
CODwwwwd.CLK_M
CODwwwwd.CLK_R
CODwwwwd.TRO_R
CODwwwwd.SNX_R.Z
CORGddd0.yyI
COPGddd0.yyI
CODwwwwd.ION_R
CODwwwwd.ION_P
CODwwwwd.ION_P2
CODwwwwd.ION_P5
CGIMddd0.yyN_R
CGIMddd0.yyN_P
CGIMddd0.yyN_P2
CGIMddd0.yyN_P5
P1C1.DCB
P1P2.DCB
P1P2_ALL.DCB
P1P2_GPS.DCB
P1C1_RINEX.DCB
P2C2_RINEX.DCB
CODE.DCB
CODE_FULL.DCB

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

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

30

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

CODwwwwd.ERP_U

CODE ultra–rapid GNSS orbits
CODE ultra–rapid ERPs belonging to the ultra–rapid orbit product
CODE ultra–rapid troposphere product, troposphere SINEX format
SINEX file from the CODE ultra-rapid solution
Summary of stations used for the latest ultra–rapid orbit
Last update of CODE rapid ionosphere product (1 day) complemented with
ionosphere predictions (2 days)
Last update of CODE 5–day orbit predictions, from rapid analysis, including all
active GPS and GLONASS satellites
CODE ultra-rapid GNSS orbits from the 24UT solution available until thecorresponding early rapid orbit is available (to ensure a complete coverage oforbits even if the early rapid solution is delayed after the first ultra-rapid solutionsof the day)
CODE ultra-rapid ERPs belonging to the ultra-rapid orbits

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

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

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

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

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

31

Dach, Schaer et al.: Center for Orbit Determination in Europe
Table 2: CODE final products available in the product areas of the IGS data centers (continued).
Other product files (not available at all data centers):
CODGddd0.yyI.Z
CKMGddd0.yyI.Z
GPSGddd0.yyI.Z

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

versity of Bern. URL: http://www.aiub.unibe.ch/download/REPRO_2013; DOI:
10.7892/boris.75680 .

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. (2016).
In Sect. 3.1 we give an overview of important development steps in the year 2016. Section 3.2 describes the introduction of the advanced handling of GNSS biases in the processing scheme of CODE .

3.1 Overview of changes in the processing scheme in 2016
Table 3 gives an overview of the major changes implemented during year 2016. 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 Table 3 were implemented, too. Those mainly
concern data download and management, sophistication of CODE’s analysis strategy,
software changes (improvements), and many more. As these changes are virtually not
relevant for users of CODE products, they will not be detailed on any further.

3.2 Introducing the Advanced Bias Handling
Since May 2016, CODE changed its code bias handling completely, from a differential to a
pseudo–absolute bias setup. The code bias estimation is crucial for GNSS data processing
when not only phase data, but also code measurements are used, such as for clock analysis
or ambiguity resolution strategies relying on code measurements. The differential code
biases (DCB) (and the corresponding inter–system biases (ISB) for multi–GNSS clock32

3 Changes in the daily processing for the IGS
Table 3: Selected modifications of the CODE processing over 2016.
Date

DoY/Year

Description

28-Jan-2016

028/2016

28-Feb-2016
17-Mar-2016
27-Mar-2016

059/2016
077/2016
087/2016

10-May-2016

131/2016

17-May-2016

138/2016

25-Jun-2016

177/2016

26-Jun-2016

178/2016

26-Jun-2016

178/2016

03-Jul-2016

185/2016

03-Jul-2016

185/2016

24-Jul-2016

206/2016

21-Aug-2016

234/2016

22-Sep-2016

235/2016

16-Oct-2016

290/2016

30-Oct-2016

304/2016

Ensure consistency between the clock RINEX and Bernese formatted
satellite clock files regarding the used reference clock in the final
processing scheme (both files are publicly available at AIUB’s FTP
server)Precise orbit files include also 24 UT epoch (for internal purposes only!)
SVN 49 is excluded from clock processing.
Renaming of two GLONASS-M satellites (SVN 754→854 and SVN
755→855).
See: IGSMAIL #7252 and BSWMAIL #0351.
Adjust the settings for supporting weakly observed satellites (at thistime G04 and R26) by additional redundant baselines.
Start with enabeling the new bias handling scheme into the operation
processing. This software change should have no effect on the products.
Solve potential issues if the wavelength factor is not given in the input
RINEX file
Based on the new bias handling principle new types of biases aremonitored:• GLONASS-like bias monitoring for all non-GLONASS systems• Bias Multiplier estimation.
• BIACAL/IONGEN/MULGEN processes are not station-specific.
Also stations from CODE-MGEX solution are added to the internal
PPP processing
For monitoring purposes currently inter-GNSS translation andtroposphere biases are setup (see Dach et al. (2012)). These set of biases
are now extended to troposphere gradient bias parameters.
Use satellite as reference clock for the clock estimation in order toguarantee a complete clock product with the smalles possible numbers of
missing epochs. The reference clock is changed after the processing andbefore the submission to a station clock.
Satellite attitude modelling according to Kouba (2009) for GPS- andDilssner et al. (2011) for GLONASS-satellites
When introducing the new bias handling scheme in May 2016
unintentionally the receiver and satellite biases are stacked over threedays in the final ionosphere product generation whereas they are treaded
as daily independent parameters in the rapid ionosphere procedure.
The setup was adjusted that receiver biases are estimated independently
day by day whereas the satellite biases are stacked over three days inboth, the final and rapid ionosphere product generation procedures.
Preparation the processing for PSD-handling (post-seismic deformations)as requested for the ITRF2014/IGS14 reference frame. Establishing theparallel processing scheme including the usage of RINEX 3 data (as far
as available) and updating the station list for the final processing.
Introducing priority list when processing RINEX 3.0x data (at this point
only in the internal PPP process):
1. RINEX 3 files with long names generated in the receiver
2. RINEX 3 files with short names
3. RINEX 2 files
4. RINEX 3 files with long names generated from a stream
5. RINEX 3 files from unknown sources
Additional verification step to check the observation quality by astation-by-station and baseline-by-baseline processing.

33

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

GNSS Observation Files

Clock Analysis:
Setup of observation equations(ionosphere-free linear combination)

Ionosphere Analysis:
Setup of observation equations(geometry-free linear combination)

Normal Equations (NEQ)(Clock Analysis)

Normal Equations (NEQ)(Ionosphere Analysis)

Parameter adjustments
and inversion of
normal equations

Parameter adjustments
and inversion of
normal equations

Code biases and otherunknown parameters(Clock Analysis) Code bias parametersspecific to eachobservable Without code bias
datum definition.

 Selection of reference
observables for thecurrent IGS clock
convention.
 Bias datum definition
imposed on (combined)
NEQ-system.

Parameter adjustments
and inversion of
normal equations

Code biases and otherunknown parameters(Ionosphere Analysis)

Code biases and otherunknown parameters(Clock-Ionosphere Combined Solution)

Figure 2: New workflow for code bias estimation at CODE.
C1C

C1W

C2C

C2W

C1C

C1P

C2C

C2P

20

Code bias [ns]

0

10

0

R855

R854

R853

R851

R802

R747

R745

R744

R743

R742

R736

R735

R734

R733

R732

R731

R730

R721

R720

R719

R717

G041
G043
G044
G045
G046
G047
G048
G049
G050
G051
G052
G053
G054
G055
G056
G057
G058
G059
G060
G061
G062
G063
G064
G065
G066
G067
G068
G069
G070
G071
G072
G073

R716

−10

−20

R715

Code bias [ns]20

Figure 3: GPS (left) and GLONASS (right) observable specific code biases from 30-day average(February 2017).

analysis) have been replaced by observable–specific code biases (OSB) which assigns eachobservable type its own bias. The new implementation has major advantages for multi–
GNSS processing and allows to distinguish between different observable types according
to their description in the RINEX V3 format. The OSB parameters are introduced into
the observation equations and can be later combined on the normal equation (NEQ) level.
This can be done either to produce a multi–day solution or to combine bias parametersfrom different sources, e.g. to combine biases from clock and ionosphere analysis to retrieve
one common set of OSBs, which can be later used for all purposes.

34

3 Changes in the daily processing for the IGS
With the changed bias handling, the processing scheme for the bias determination has beenrevised using the advantage of combining bias NEQs from different sources. Figure 2 shows
the updated workflow of CODE’s processing scheme for the determination of the code
biases. Our main bias products are extracted from the combination of normal equations(NEQ) of bias estimations of clock and ionosphere analysis. The estimated OSBs can beused for any application by simply correcting each observation according to the estimatedbiases value.
The OSB implementations lead to a revised processing strategy for the 30-day code bias
products CODE.DCB and CODE_FULL.DCB (ftp://ftp.unibe.ch/aiub/CODE/CODE.
DCB and ftp://ftp.unibe.ch/aiub/CODE/CODE_FULL.DCB). The combination of the 30day average DCBs are generated combining OSBs of the last 30 days on the normal
equation level based on the clock-ionosphere combined solution. The resulting OSB values
are converted into DCBs and P1–C1 bias tables for cctononcc (ftp://ftp.unibe.ch/aiub/bcwg/cc2noncc/p1c1bias.hist) and published on our ftp server. The OSBs for
GPS and GLONASS satellites are shown in Figure 3. The new OSB estimations will bemade publicly available in 2017 using the upcoming BIAS-SINEX V1.00.

3.3 Changing the Satellite Attitude Handling
Starting from GPS week 1907 GNSS yaw attitude models for the GPS and GLONASS-M
satellites were introduced for the routine GNSS analysis at CODE. The models are applied
during eclipse seasons when the satellites do not follow the nominal yaw attitude behavior,in particular, during noon and midnight orbit manoeuvres. Description of the attitude
behaviour during these periods is discussed in Kouba (2009) for the GPS Block IIA andBlock IIR satellites, in Dilssner (2010) for the GPS Block IIF and in Dilssner et al. (2011)
for the GLONASS-M satellites.
GPS week 1907
4%

Satellites

25
3%

20
15

2%

10
1%
5
0%

0
200

250

300

350

050

100

150

2015

2016

200

250

300

Deleted observations

IGSRAPID solution (GLONASS)

Epoch [year, DOY]
Figure 4: Overview of deleted observations after residual screening during Rapid orbits estimation of GLONASS satellites.

35

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

Kouba/Dilssner attitude models

25 %

25 %

20 %

20 %

15 %

15 %

10 %

10 %

5%

5%

0%
−200

−100
0
100
Residual [mm]

200

0%
−200

−100
0
100
Residual [mm]200

Figure 5: SLR residuals of eclipsed GLONASS satellites computed with nominal (left) andKouba/Dilssner (right) attitude models over 02-29 October 2015.

As the GPS Block IIA, IIF and GLONASS-M satellites have non-zero horizontal phasecenter eccentricity with respect to the z-axis in the body-fixed reference frame, deviations
from the nominal yaw attitude directly affect the satellite-station geometry. For othersatellite types the incorrect yaw attitude modelling is primarily absorbed in satellite clocks
and, thus, results in their biased estimates. The introduction of the attitude models had
an impact on the number of rejected observations in the routine IGS analyses at CODE.
Thus, prior to GPS week 1907 the use of only nominal attitude for GLONASS satellites
resulted in repeating reductions of accepted observations during eclipse seasons in, e.g., ourRapid solutions, Figure 4. With the introduction of the aforementioned attitude models
the number of observations during eclipse seasons is no longer reduced.
The impact of the yaw attitude modelling can also be observed in the accuracy of thecomputed orbits. In particular, Figure 5 shows SLR residuals of GLONASS satellites
during 02-29 October 2015 when one plane of the constellation was in eclipse. With theuse of the yaw attitude models the bias between the microwave and SLR orbits is reduced
from −15 ± 61 mm to −2 ± 44 mm.

4 CODE contribution to the IGS–MGEX campaign
Since 2012 CODE contributes to the IGS Multi-GNSS EXperiment (MGEX) aiming on
the integration of new GNSS into existing processing chains (Prange et al. 2016a). The
product is generated using the latest development version of the Bernese GNSS Software
package and is derived from a rigorously combined five system solution considering GPS,36

4 CODE contribution to the IGS–MGEX campaign
Table 4: CODE MGEX products available through anonymous ftp
CODE final products available at ftp://ftp.unibe.ch/aiub/CODE_MGEX/CODE/yyyy/
yyyy/COMwwwwd.EPH.Z
yyyy/COMwwwwd.ERP.Z
yyyy/COMwwwwd.CLK.Z
yyyy/COMwwwwd.BIA.Z
yyyy/COMwwwwd.DCB.Z

CODE GNSS orbits for GPS, GLONASS, Galileo, BeiDou, and QZSS
satellites, SP3 format
Earth rotation parameters related to the MGEX orbits, IERS format
Satellite and Receiver clock corrections consistent to the MGEX orbits witha sampling of 5 minutes, clock RINEX format
GNSS code biases related to the MGEX clock correction product, bias
SINEX format v0.01
GNSS code biases related to the MGEX clock correction product, Bernese
formatGLONASS, Galileo, BeiDou (MEO and IGSO), and QZSS satellites. Even if the focus
is on the satellite orbits and satellite clock corrections, also other parameters need to be
estimated: diverse biases for the receivers, ERPs, station coordinates, and troposphereparameters. Since the beginning of 2016 the CODE MGEX (COM) products are not only
submitted to the CDDIS, but also provided via the anonymous ftp server of the AIUB
(ftp://ftp.unibe.ch/aiub/CODE_MGEX/CODE). The list of products is given in Table 4.
Based on the MGEX solution, CODE has contributed to the comparison and validation of
estimated satellite antenna phase center offsets for Galileo satellites (Steigenberger et al.
2016). Some effort has been put to the adaptation to the long RINEX3 file name convention and data management. The main focus of CODE’s MGEX activity in 2016 was,however, on the critical review of the results achieved so far and on the definition of themost important topics for research and technical improvements in the next time. The
results of this analysis are discussed in Prange et al. 2017b. If the new GNSS shall contribute to future IGS solutions in the same extent as GPS and GLONASS, improvements
are necessary in the following fields:• Receiver and transmitter antenna PCO and PCV• Handling of observation types and biases• Earth radiation pressure model• Transmitter antenna thrust model• Orbit normal attitude and related SRP models (for BDS, QZSS)• Integer ambiguity resolution

37

RMS of linear clock fit [ns]Dach, Schaer et al.: Center for Orbit Determination in Europe
YA ECOM2NA ECOM-N v1
NA ECOM-N v2

6
5
4
3
2
1
0
230

235

240

245

250

Figure 6: RMS of daily linear fit through epoch-wise satellite clocks of QZS-1 between DOY 228
and 250/2015. Gray background: Satellite is in orbit normal mode. YA: Yaw attitude
law applied. NA: Normal attitude law applied. ECOMx: SRP model version.

References
Arnold D., M. Meindl, G. Beutler, R. Dach, S. Schaer, S. Lutz, L. Prange, K. Sośnica,
L. Mervart, and A. Jäggi. CODE’s new solar radiation pressure model for GNSS
orbit determination. Journal of Geodesy, 89(8):775–791, August 2015. doi: 10.1007/
s00190-015-0814-4.
Beutler G., E. Brockmann, W. Gurtner, U. Hugentobler, L. Mervart, M. Rothacher, and
A. Verdun. Extended orbit modeling techniques at the CODE processing center of
the International GPS Service for Geodynamics (IGS): Theory and initial results.
Manuscripta Geodaetica, 19(6):367–386, April 1994.
Dach R., 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. Center for Orbit Determination In Europe: IGS Technical Report 2011. In M. Meindl, R. Dach, and Y. Jean,
editors, International GNSS Service: Technical Report 2011, pages 29–40. IGS Central
Bureau, July 2012.
Dach R., S. Lutz, P. Walser, and P. Fridez, editors. Bernese GNSS Software, Version
5.2. Astronomical Institute, University of Bern, Bern, Switzerland, November 2015.
ISBN 978-3-906813-05-9. doi: 10.7892/boris.72297. URL ftp://ftp.unibe.ch/aiub/
BERN52/DOCU/DOCU52.pdf. User manual.
Dach R., S. Schaer, D. Arnold, E. Orliac, L. Prange, A. Sušnik, A. Villiger, A. Maier,
L. Mervart, A. Jäggi, G. Beutler, E. Brockmann, D. Ineichen, S. Lutz, A. Wiget,
A. Rülke, D. Thaller, H. Habrich, W. Söhne, J. Ihde, and U. Hugentobler. CODE
Analysis center: IGS Technical Report 2015. In Y. Jean and R. Dach, editors, International GNSS Service: Technical Report 2015, pages 21–34. IGS Central Bureau,
May 2016.

38

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. ISSN 0273-1177. doi:
http://dx.doi.org/10.1016/j.asr.2010.09.007.
Dilssner, F., 2010. GPS IIF-1 Satellite. Antenna Phase Center and Attitude Modeling.
InsideGNSS 5:59–64.
Kouba J. A simplified yaw-attitude model for eclipsing GPS satellites. GPS Solutions, 13(1):1–12, 2009. ISSN 1521-1886. doi: 10.1007/s10291-008-0092-1.
Prange L., R. Dach, S. Lutz, S. Schaer, and A. Jäggi. The CODE MGEX orbit and clock
solution. In C. Rizos and P. Willis, editor, IAG 150 years, International Associationof Geodesy Symposia. Springer, 2016a. doi: 10.1007/1345_2015_161.
Prange L., E. Orliac, R. Dach, D. Arnold, G. Beutler, S. Schaer, and A. Jäggi. CODE’s
five-system orbit and clock solution – the challenges of multi-GNSS data analysis.
Journal of Geodesy, 91(4):345–360, 2017. doi: 10.1007/s00190-016-0968-8.
Steigenberger P., M. Fritsche, R. Dach, R. Schmid, O. Montenbruck, M. Uhlemann, andL. Prange. Estimation of satellite antenna phase center offsets for Galileo. Journal of
Geodesy, 2016. doi: 10.1007/s00190-016-0909-6.
All publications, posters, and presentations of the Satellite Geodesy research group at
AIUB are available at http://www.bernese.unibe.ch/publist .

39

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

40

NRCan Analysis Center
Technical Report 2016
B. Donahue, R. Ghoddousi–Fard,
M.A. Goudarzi, Y. Mireault, F. Lahaye
Natural Resources Canada 588, Booth Street,
Ottawa ON, Canada K1A 0Y7
E–mail: francois.lahaye@canada.ca

1 Introduction
This report covers the major activities conducted at the NRCan Analysis Center (NRCan–AC) and product changes during the year 2016 (products labelled ’em*’). Additionally,changes to the stations operated by NRCan are briefly described. Readers are referredto the Analysis Coordinator web site at http://acc.igs.org for historical combination
statistics of the NRCan–AC products.

2 NRCan Core Products
The Rapid and Ultra–Rapid products continued to be generated using the Bernese GNSS
Software version 5.2 (Dach et al. 2015).
Since summer 2016, 15–min GNSS data files, normally available within a few minutes
at CDDIS (USA), BKG (Federal Agency for Cartography and Geodesy, Germany) andGeoscience Australia, are downloaded for use in our Ultra–Rapid Products generation.
Hourly files are downloaded whenever 15–min files are missing.
A revision of available GNSS hourly/daily stations was performed at the end of summer
2016. Improved spatial distribution and density of GLONASS tracking network resulted
in minimal (ps) improvement to GLONASS clock RMS and improved GLONASS orbits
RMS by an order of 5–10 mm, when compared to IGS Final (IGL).
The Final GPS products continued to be estimated with JPL’s GIPSY–OASIS software
in 2016. Starting February 1, 2016 the software was upgraded to version 6.4.

41

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

3 Ionosphere and DCB monitoring
Daily and near–real–time ionosphere products and DCB estimates continued to be generated internally. The impact of ionospheric products from NRCan and selected IGS AC’s
on single frequency PPP was reported in Ghoddousi-Fard and Lahaye (2016). Starting
November 28, 2016, NRCan’s global daily total electron content maps (emrg[ddd]0.[yy]i)
use GLONASS observations from about 220 of the 350 contributing stations. EstimatedGPS and GLONASS satellite and station DCBs are reported in the header of daily IONEX
files.
Ionospheric irregularities as sensed by GPS phase rate derived indices from real–time
IGS network continued to be monitored in near–real–time and archived for long–term
analysis. These, together with high rate GPS and GLONASS observations from otherregional networks, are processed for targeted periods with complementary sensors to study
space weather storms and characterize ionospheric irregularities at high latitudes (see e.g.
Ghoddousi-Fard et al. (2016a, b); Prikryl et al. (2016)).

4 Operational NRCan stations
In addition to routinely generating all core IGS products, NRCan is also providing publicaccess to GPS/GNSS data for more than 80 Canadian stations. This includes 40 stations currently contributing to the IGS network through the Canadian Geodetic Survey’s
Canadian Active Control System (CGS–CACS), the CGS Regional Active Control System(CGS–RACS), and the Geological Survey of Canada’s Western Canada Deformation Array(GSC–WCDA). The NRCan contribution to the IGS network includes 25 GNSS plus 15
GPS only stations. Since December 7, 2016, NRCan has been contributing RINEX v3.03
data for 30 GNSS stations from the CGS–CACS network. Several upgrades/changes to
the CGS–CACS were completed in 2016 and these are listed in Table 2. Figure 1 showsa map of the NRCan GPS/GNSS network as of January 2017. Further details about
NRCan stations and access to NRCan public GPS/GNSS data and site logs can be foundat https://webapp.geod.nrcan.gc.ca/geod/data-donnees/cacs-scca.php or from thefollowing anonymous ftp site: ftp://rtopsdata1.geod.nrcan.gc.ca/gps/.

42Reference

5 Acknowledgement
ESS Contribution number / Numéro de contribution du SST: 20160354(c) Her Majesty the Queen in right of Canada 2017

Reference
Dach, R., S. Lutz, P. Walser, P. Fridez. Bernese GNSS Software Version 5.2. AIUB,
Astronomical Institute, University of Bern. 2015.
Ghoddousi-Fard, R. and F. Lahaye. Evaluation of single frequency GPS precise point
positioning assisted with external ionosphere sources. Advances in Space Research, 57(10):2154–2166, 2016 doi: 10.1016/j.asr.2016.02.017
Ghoddousi-Fard, R., P. Prikryl, and F. Lahaye. Geomagnetic storm of March 17, 2015:
global RT–IGS GPS phase irregularities and effects in the Canadian auroral region.
Oral presentation given at International Beacon Satellite Symposium BSS–2016, Trieste, Italy, June 27 – July 1, 2016. Extended abstract published in conference proceedings.
Ghoddousi-Fard, R., P. Prikryl, K. Jacobsen, and F. Lahaye. GPS and GLONASS 1
Hz phase rate observations to study high latitudes ionospheric irregularities. Oralpresentation given at American Geophysical Union fall meeting 2016, San Francisco,
United Sates, December 12–17, 2016.
Prikryl, P., R. Ghoddousi-Fard, J.M. Weygand, A. Viljanen, M. Connors, D.W. Danskin,
P.T. Jayachandran, K.S. Jacobsen, Y.L. Andalsvik, E.G. Thomas, J.M. Ruohoniemi,
T. Durgonics, K. Oksavik, Y. Zhang, E. Spanswick, and M. Aquino. GPS phase
scintillation at high latitudes during the geomagnetic storm of March 17–18, 2015
Journal of Geophysical Research: Space Physics, doi: 10.1002/2016JA023171

43

NRCan AC
Table 1: NRCan-AC products
Product

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

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

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

Description
GPS only• Time Span 1994–Nov–02 to 2014–Mar–29• Use of JPL’s GIPSY–OASIS IIv6.3• Daily orbits, ERP and SINEX• 5–min clocks• Submission for IGS repro2 combination
GPS only• Since 1994 and ongoing• Use of JPL’s GIPSY–OASIS II v6.4 from 2016–Feb–01• Daily orbits, ERP and SINEX• 30–sec clocks• Weekly submission for IGS Final combination

GPS+GLONASS• Since 2011–Sep–11 and ongoing• Use of Bernese 5.0 until 2015–Jan–31• Use of Bernese 5.2 since 2015–Feb–01• Daily orbits and ERP• 30–sec clocks• Weekly submission for IGLOS Final combination• Station XYZ are constrained, similar to our Rapid solutions

GPS only• From July 1996 to 2011–05–21• Use of JPL’s GIPSY–OASIS (various versions)• Orbits, 5–min clocks and ERP (30–sec clocks
from 2006–Aug–27)• Daily submission for IGR combination
GPS+GLONASS• Since 2011–Sep–06 and ongoing• Use of Bernese 5.0 until 2015–Feb–11• Use of Bernese 5.2 from 2015–Feb–12• Daily orbits and ERP• 30–sec GNSS clocks

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

Real–TimeGPS only• From early 2000 to 2013–09–13, hour 06• Use of Bernese 5.0• Orbits, 30–sec clocks and ERP (hourly)• Submission for IGU combination (4 times daily)
GPS+GLONASS• Since 2013–09–13, hour 12• Use of Bernese 5.0 until 2015–Feb–12• Use of Bernese 5.2 since 2015–Feb–13• Orbits and ERP (hourly)• 30–sec GNSS clocks (every 3 hours)• 30–sec GPS–only clocks (every other hours)• Submission for IGU/IGV combination (4 times daily)
GPS only• Since 2011–11–10• In–house software (HPGPS.C)• RTCM messages:– orbits and clocks:1060 (at Antenna Reference Point)– pseudorange biases: 1059
– Interval: 5 sec

Table 2: NRCan Station Upgrades in 2016
Station

Date

Remarks

albh
albh
algo
baie
baie
chur
drao
drao
frdn
kuuj
prds
sask

2016–06–09
2016–06–09
2016–06–29
2016–07–11
2016–07–11
2016–07–21
2016–06–08
2016–06–08
2016–08–11
2016–02–02
2016–06–10
2016–08–18

Station receiver switched to TPS NET–G3A
External H–MASER installed
Station receiver switched to JAVAD TRE_G3TH DELTA
Station receiver upgraded to GNSS TPS NET–G3A
Antenna switched to TPSCR.G3 NONENOVS dome installed
New antenna cable
External H–MASER installed
Damaged antenna replaced with same model TPSCR.G3 NONE
Damaged receiver replaced with same model TPS NET–G3A
Station receiver switched to JAVAD TRE_G3TH DELTA
Station receiver switched to JAVAD TRE_G3TH DELTA

45

NRCan AC

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

46

The ESA/ESOC IGS Analysis Centre
Technical Report 2016
T.A. Springer, I. Romero,
W. Enderle, E. Schoenemann, 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 wegive a summary of the IGS related activities at ESOC in 2016.

2 Overview
2.1 Routine Products
The ESA/ESOC IGS Analysis centre contributes to all the core IGS analysis centre products, being:• Final GNSS (GPS+GLONASS) products– Provided weekly, normally on Friday after the end of the observation week
– Based on 24hour solutions using 150 stations– True GNSS solutions obtained by simultaneously and fully consistently processing of GPS and GLONASS measurements, using a total of around 55 GNSS
satellites– Consisting of Orbits, Clocks (30s), daily SINEX coordinates and EOPs, andIonosphere• Rapid GNSS (GPS+GLONASS) products47

2 Overview– 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 obtained by simultaneously and fully consistently processing of GPS and GLONASS measurements, using a total of around 55 GNSS
satellites– Consisting of Orbits, Clocks, Ionosphere, and EOPs
– Rapid SINEX coordinates and EOPs available as well
• Ultra-Rapid GNSS (GPS+GLONASS) products– Provided 4 times per day covering a 48 hour interval; 24 hours of estimatedplus 24 hours of predicted products– Available within 3 hours after the end of the observation interval which startat 0, 6, 12, and 18 hours UTC– Based on 24 hours of observations using 110 stations– True GNSS solutions obtained by simultaneously and fully consistently processing of GPS and GLONASS measurements, using a total of around 55 GNSS
satellites– Consisting out of Orbits, Clocks, and EOPs
– Separate Ionosphere estimates and predictions• Real-Time GNSS services– Generation of two independent real-time solution streams– Analysis 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, e.g., the RealTime Service where besides being one of the analysis centres we are also responsible for the
analysis centre coordination, infrastructure committee (committee chairmanship), MGEX,
antenna calibarations, and satellite orbit modeling working groups.
An up to date description of the ESA IGS Analysis strategy may always be found at:
http://navigation-office.esa.int/products/gnss-products/esa.acn

48

2 Overview

2.2 Product Changes
The main changes in our processing in 2016 were the following:• Switch to new NAPEOS version 4.0• Turned off box-wing model for GPS Block IIF satellites as it was having a negative
effect on the products• Preparation of ITRF2014 and other changes including:– Switch to ITRF2014 including PSD functions (done on GPSweek 1934)– Include Power Thrust for GPS and GLONASS– Correct Infrared (IR) properties in our box-wing models (GPSweek 1935)– Investigate and tune GPS Block IIF box-wing model properties (on-going)

2.3 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. Furthermore, the
ESA products are one of the most complete GNSS products. In fact ESA/ESOC was thefirst 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 products is 30 seconds. Another special feature of the ESA
products is that they are based on completely independent 24 hour solutions. Although
this does not necessarily lead to the best products, as in the real world the orbits and EOPs
are continuous, it does provide a very interesting set of products for scientific investigations
as there is no aliasing and no smoothing between subsequent solutions. An other uniquefeature is that our rapid products are, besides being one of the best, also one of the mosttimely available products. Normally our GNSS rapid products are available within 2 hours
after the end of the observation day whereas the official GPS-only IGS products become
available only 17 hours after the end of the observation day, a very significant difference.
Another important feature of the ESA products is that we use a box-wing model for
the GNSS satellites to a priori model the Solar- and Earth Albedo radiation pressure.
The GNSS block type specific models were tested thoroughly in the scope of our IGS
reprocessing and the results were presented at the IGS workshop in 2014,Springer et. al.
(2014). Significant improvements were observed for most, if not all, estimated parameters.
Last but not least it is wortwhile to mention that besides being an analysis center in the
IGS ESA/ESOC is also an analysis center in the IDS and the ILRS. This represents a rather
unique achievement in that one single software version, NAPEOS Springer et. al. (2009),
contributes to the products and solutions of three different space geodetic techniques.
Work is in progress to also add VLBI to our processing capabilities.
49

3 GNSS Sensor Station Upgrade

3 GNSS Sensor Station Upgrade
ESA/ESOC continues to provide worldwide data for all GNSS constellations to the IGS
via its 10 public stations, and to expand its proprietary station network. This expansion
is accomplished by focusing on the establishment of collaborations with third parties toinstall new stations at various locations around the world such as in South Africa, Brasil,
Russia, Canada, etc. The ESOC GNSS Reference Station network is also present at all
ESA Deep Space sites and other locations where ESA have satellite tracking assets aroundthe world (see map below).
The entire ESA GNSS network now operates Septentrio PolarRx4 receivers with SEPCHOKE antennas, with the exception of MGUE, MAL2, MAS1 and FAA1 where theLeica AR25.R4 antennas are installed. The station network has been expanded in recent
times with installations in Awarua (New Zealand), Dubai (U.A.E), Malaysia, Tsukuba(Japan), Bishkek (Kyrgyzstan), Darmstadt (Germany), and plans are on-going for up to
9 more stations in the next 18 months. No data is publicly available for the time being
for any of the newly installed stations.

Figure 1: ESA/ESOC GNSS Station Network

The Septentrio PolaRX4 receivers have proven to be very capable at our stations and they
provide all phase and pseudo-range measurements for the GNSS constellations as available:
GPS, GLONASS, Galileo, QZSS, Compass, SBAS, EGNOS, etc, last year ESA/ESOC has
started contributing with long name daily, hourly and high-rate multi-GNSS RINEX 3 data
to the IGS for the 10 ESA/ESOC public stations. ESA/ESOC continues to provide theNBS (NavBits) data from GPS L1 in support of LEO Precise Orbit Determination for
EUMETSAT.

50

4 Ionosphere Modeling Activities
For 2017/2018 worldwide coverage is planned to be enhanced considerably with the ongoing negotiations with third parties in Brasil, South Africa, Russia and Canada ongoing.
The station map shows a projection of the impact on the global coverage for the inclusion of
the 9 planned future ESA/ESOC stations, enhancing worldwide GNSS satellite coverage,
aiming to provide full triple station coverage for al GNSS satellites at all times.

4 Ionosphere Modeling Activities
ESA/ESOC contributes with IONEX products to the IGS Ionosphere Working Groupsince its inception in 1998. Up to now, ionosphere products for the IGS are still based ona single-layer approach, where the vertical TEC is represented by spherical harmonics, in
combination with an estimation of daily receiver and satellite DCBs. ESA IONEX files
are delivered in final (2h time resolution) and in rapid (2h and 1h time resolution) modeto the IGS, and they are based on processing both GPS and GLONASS observations.
In addition, predicted products are delivered. ESOC employs the Ionosphere Monitoring
Facility (IONMON) for its ionosphere processing, which in 2013 became and integral partof ESOC’s NAPEOS software.

51

5 Multi-GNSS (MGEX)

5 Multi-GNSS (MGEX)
We frequently process and reprocess the data from the IGS Multi-GNSS Experiment(MGEX) as at the current stage we prefer a detailed analysis of the MGEX data overroutine analysis. In the scope of these activities we have derived a consistent set ofGalileo, BeiDou and QZSS PCO/PCVs based on processing the data of 2014 to 2016. We
have extended our box-wing modeling activities now also to the satellites of the “new”
constellations, i.e., Galileo, BeiDou and QZSS. We believe that for BeiDou and QZSS an
accurate model of the satellites will be of great benefit, if not even mandatory. This isdue to the fact that for small beta angles these satellites switch their attitude mode fromyaw-steering (the nominal attitude mode used by GPS, GLONASS and Galileo) to orbit
normal mode. In the orbit normal mode the satellite are no longer oriented towards the
Sun and thus the solar radiation pressure becomes very hard to model. In the orbit normal
mode phase the widely used ECOM model, and also the enhanced ECOM2 model, fail toproperly model the radiations forces. The main interesting features and challenges we havefound so far in our multi-GNSS analysis activities were presented at the IGS workshop in2014 and 2016, and may be summarized as:• Strong azimuthal dependent pattern in the GALILEO carrier phase residuals, clearlyan azimuthal ANTEX pattern needed• Severe inconsistency between the three GPS phase signals (L1, L2, and L5); a periodic effect with an amplitude of 50 mm clearly visible• Severe challenges to model the QZSS satellite during the orbit normal mode phase(|β| < 200 )• Strong elevation dependent pattern in the BEIDOU pseudo range residuals for the
MEO satellites• Severe challenges to model the BeiDou GEO satellite due to orbit normal mode
attitude• Significant challenges to model the BeiDou MEO and IGSO satellites during theorbit normal mode phase (|β| < 40 )In 2016 our prime focus has been to improve our understanding and modelling of theGalileo satellites to such a level that they can be included in our core IGS products (final,
rapid, ultra-rapid, and ionosphere) as soon as possible. We are confinced that we have
now achieved this goal and that the quality of our Galileo orbit estimates is significantly
better then that of our GLONASS orbit estimates and is getting close to the quality of
the GPS orbit estimates.

52

References

6 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. 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 isimportant because besides being an IGS Analysis Centre, ESA/ESOC is also an Analysis
Centre of the IDS and the ILRS.
In the coming year our main focus will be on improving the orbit modelling for the different
GNSS constellations. We need to improve our (a priori) box-wing models for the QZSSand BeiDou satellites and handle the new Glonass-K and Beidou 3rd genaration satellites.
Also integer ambiguity resolution of all constellations will be in the focus in including
across constellation ambiguity resolution were feasible.

References
Springer T., R. Zandbergen, A. Águeda Maté.
NAPEOS Mathematical Models
and Algorithms, DOPS-SYS-TN-0100-OPS-GN, Issue 1.0, Nov 2009, http://
navigation-office.esa.int/napeos/
Springer T., M. Otten, C. Flohrer, F. Pereira, F. Gini, W. Enderle. GNSS Satellite Orbit
Modeling at ESOC, IGS Workshop 2014, June 23–27, 2014, Pasadena, USA

53

GFZ Analysis Center
Technical Report 2016
B. Männel, Z. Deng, M. Ge, T. Nischan,
A. Brandt, M. Bradke, M. Ramatschi
Deutsches GeoForschungsZentrum (GFZ)
Department 1: Geodesy, Section 1.1: Space Geodetic Techniques
Telegrafenberg A 17, 14473 Potsdam, Germany
E-mail: benjamin.maennel@gfz-potsdam.de

1 SummaryDuring 2016, the standard IGS product generation was continued with minor changes
in the processing software EPOS-8. The GNSS observation modeling still conforms to
the GFZ repro-2 (2nd IGS Reprocessing campaign) settings for the IGS Final productgeneration. The multi-GNSS processing was continued routinely during 2016 including
GPS, GLONASS, BeiDou, Galileo, and QZSS with only few exceptions from a regularsubmission.
At the end of October 2016, Dr. Mathias Fritsche left GFZ and, therefore, also resigned
as head of the IGS analysis center. We would like to take the opportunity to express
our sincere appreciation and gratitude to him for his great commitment but also for hiscollegial spirit over the past three years.

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

3 Operational Data Processing and Latest Changes
Our EPOS-8 processing software is following the IERS Conventions 2010 (Petit and Luzum2010). For the IGS Final, Rapid and Ultra-rapid chains approximately 200, 130, and 95

54

4 Multi-GNSS data processing
Table 1: List of products provided by GFZ AC to IGS and MGEXIGS Final(GLONASS since week 1579)

gfzWWWWD.sp3
gfzWWWWD.sp3
gfzWWWWD.clk

gfzWWWWD.tro

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

IGS Rapid(GLONASS since week 1579)

gfzWWWWD.sp3
gfzWWWWD.clk
gfzWWWWD.erp

Daily orbits for GPS/GLONASS satellites
5-min clocks for stations and GPS/GLONASS satellites
Daily Earth rotation parameters

IGS Ultra-Rapid(every 3 hours; provided to IGS every 6 hours; GLONASS since week
1603)

gfuWWWWD_HH.sp3
gfzWWWWD_HH.erp

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

gfzWWWWD.snx
gfzWWWW7.erp
gfzWWWW7.sum

MGEX Rapid
gbmWWWWD.sp3
gbmWWWWD.clk
gbmWWWWD.erp

Daily satellite orbits for GPS/GLONASS/Galileo/BeiDou/QZSS
30 sec (since GPS-week 1843) receiver and satellite clocks
Daily Earth rotation parameters

MGEX Ultra-Rapid(since week 1869)

gbuWWWWD_HH.sp3

Adjusted and predicted orbits for
GPS/GLONASS/Galileo/BeiDou/QZSS
Earth rotation parameters

gbuWWWWD_HH.erp

sites are used, respectively. Recent changes in the processing strategy are listed in Table
2. Only minor changes have been applied for the observation modeling in order to keep
the consistency with respect to the repro-2 processing strategy. In preparation for thereference frame switch from IGS2008 to IGS2014 an additional processing chain, without
product submission, was running between GPS week 1924 (November 20th, 2016) and1933 (January 28, 2017).

4 Multi-GNSS data processing
The IGR-like and the ultra-rapid like style multi-GNSS processing was continued in 2016
(Deng 2016). The GFZ multi-GNSS solution covers 5 different systems, namely GPS,55

GFZ AC
Table 2: Recent processing changes
Date

IGS

IGR/IGU

Change2016-02-02

w1881

-

2016-03-01
2016-05-25

w1886
w1896

w1886.4
w1898.4

Switch from meteo model NOM to GPT2 and from GMF
to VMF in the processing of 30 s clock corrections
in order to be consistent with 300 s clock processing
Skip bad satellites from constellation mean calculation
Inclusion of RINEX 3 data

Table 3: Used observation types and number of satellites (averaged) in the multi-GNSS dataprocessing
Satellite System# Satellites

Observation TypesGPS
GLONASS
Galileo
BeiDou
QZSS

31
23
11
13
1

L1/L2
L1/L2
E1/E5a
B1/B2
L1/L2

GLONASS, Galileo, BeiDou and QZSS. Figure 1 shows the total number of satellites per
GNSS included in the gbm MGEX solution. Table 3 shows the corresponding observation
type selection made for the individual GNSS. The ultra-rapid like products are identified
with the gbu acronym (cf. Table 1).
Since November 1st, 2016 both product types, gbm and gbu, are available at ftp://ftp.
gfz-potsdam.de/GNSS/products/mgnss/ with an artificial latency of 3 days. Registeredusers (registration is possible by sending an e-mail to mgnss@gfz-potsdam.de) have accessto the products via dedicated download pathes without any latency.

5 Reprocessing activities
The GFZ Analysis Center is contributing to the TIGA Reprocessing Campaign as a TIGA
Analysis Center. In order to continue our activities described in Deng et al. (2016), we
reprocessed the GPS data of the global TIGA tracking network for the time span frombegin of 2013 until end of 2015 (GPS weeks 1721 to 1877). The number of processed GPS
stations is provided as time series in Figure 2.
Since the number of daily processed TIGA stations exceeds the number of 600 stations(Figure 2) and our EPOS-8 software can process up to 250 stations in a single job, the
TIGA stations are splitted into several sub-networks. One of the sub-networks consistsof the IGS tracking stations, whereas the TIGA-only stations are divided into 2 sub-56

Number of Satellites

5 Reprocessing activities

100
90
80
70
60
50
40
30
20
10
0

QZSS: 1

GAL median: 11
BDS median: 13
GLO median: 23

GPS median: 31
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

2016
Figure 1: Total number of satellite per GNSS included in the daily MGEX processing

Figure 2: Number of GPS stations in GFZ’s TIGA re-processing

networks. The final TIGA solution is the result of a normal equation stacking of all
sub-networks. In order to connect the sub-networks 30 globally distributed IGS repro-2
stations are selected and processed together with the TIGA-only sub-networks. The groupof connecting stations is different for each sub-network and variates slightly from day to
day as they are selected automatically regarding station distribution and a posteriori fits.
The derived daily normal equations were submitted to the TIGA Combination Center by
mid of December 2016.

57

GFZ AC
90˚
NYA2

60˚
ZWE2
POTS
OBE4

ULAB
TASH
KIT3

TMS3

BIK0

URUM
MIZU

DESERVE

30˚

WUH2

SCUB

SGOC

0˚

NURK
JOGJ

PBO
UNSA

WIND

−30˚

VOIM

SUTM

LPGS

GFZ Station Map
−60˚

−90˚
−180˚

OUS2

IGS:
23
GGSP:
4
TERENO:
6
PBO:
10
GASP:
10
DESERVE: 6
−150˚

RIO2

NMSH

−120˚

−90˚

−60˚

−30˚

0˚

30˚

60˚

90˚

120˚

150˚

180˚

Figure 3: GNSS stations operated by GFZ

6 Operational GFZ Stations
The GFZ operated global GNSS station network comprises currently 23 GNSS stations
participating in the IGS tracking network. Figure 3 shows the globally distribution ofthese stations. Within the 2016, the station La Plata (LPGS) was complete renewed after
a long series of unexplained height variations. The station is now equipped with a Javad
TRE_3 DELTA receiver and a Javad RINGANT_G5T antenna. In addition, the station
Santiago de Cuba (SCUB) was updated to a tracking rate of 1 Hz.

References
Deng Z. Multi-GNSS Ultra Rapid Orbit-, Clock- & EOP-Product Series, 2016.
Deng Z., G Gendt, and T Schöne. Status of the IGS-TIGA Tide Gauge Data Reprocessing
at GFZ. In C Rizos and P Willis, editors, IAG 150 Years: Proceedings of the IAG
Scientific Assembly in Postdam, Germany, 2013, pages 33–40. Springer International
Publishing, 2016. ISBN 978-3-319-30895-1. doi: 10.1007/1345_2015_156.
Petit G. and B Luzum, editors. IERS Conventions (2010). Number 36. Verlag des Bundesamtes für Kartographie und Geodäsie, Frankfurt am Main, Germany, 2010. ISBN3-89888-989-6. IERS Technical Note No. 36.

58

CNES–CLS Analysis Center
Technical Report 2016
F. Perosanz1 , S. Loyer2 , F. Mercier1 , A. Mezerette2 ,H. Capdeville2 , J.C. Marty1
1
2

Centre National d’Etudes Spatiales,
18 av. Edouard Belin, 31400 Toulouse, France
E–mail: igs-ac@cls.fr
Collecte Localisation Satellite
8–10 rue Hermès, 31520 Ramonville, France

1 Introduction
In 2016, the CNES-CLS Analysis Center continued its contribution through the weekly
delivery of final GPS-GLONASS-Galileo products using the GINS software package. The
major evolutions in terms of models and parametrization are the following:• Implementation of a new SRP model• Software bug correction related to station PCV corrections• Multi-GNSS satellite clock product alignment strategy

2 Implementation of a new SRP model
As described in the previous reports, our dynamic parameters estimation strategy was
based on the idea of not estimating once per revolution terms in the sun D direction for
GPS block II-A satellites in order to reduce the correlations with the LOD parameter(and because the estimation of these parameters was not needed for those satellites). Thisapproach was necessarily temporary as the number of block II-A satellites was diminishing.
The last one stopped transmitting signals during week 1881 which started impacting thequality of our LOD solutions (Figure 1). An alternative parametrization based on the
ECOM2 approach has been implemented since week 1896 for all constellations. If the
impact on the orbits was limited (centimeter biases and slight degradation during eclipses)

59

CNES–CLS Analysis Center

Figure 1: Impact of the new SRP parameterization (starting week 1896) on GRG LOD products.

the LOD solution was drastically improved (Figure 1) mainly because once per revolution
terms in the sun direction are no longer estimated.
Table 1: Empirical dynamic parameters estimation strategy
Axis
D
Y
X

60

Old Stategy• Scale factor• 1/rev cos+sin except Block II-A
• 1 bias per arc

New Strategy• Scale factor• 2/rev cos+sin• 1 bias per arc• 1/rev cos+sin• 1 bias per arc• 1/rev cos+sin

4 4. Multi-GNSS satellite clock product alignment strategy

Courtesy P. Rebischung IGS ACC

Figure 2: Improvement of GRG station coordinate products since week 1915 after applying correct station antenna PCV maps.

3 Software bug correction related to station PCV corrections
A software bug has been detected and corrected since week 1915. In cases where GLONASS
PCV information are available in addition to GPS in the ANTEX files only the last block
read en was used (i.e. GLONASS instead of GPS) in the processing. If the impact of using the correct GPS station PCV data on the orbit products was not obviousvery limited,a clear improvement could be detected during the network combination by the ACC asshown in Figure 2.

4 4. Multi-GNSS satellite clock product alignment strategy
First, we modified our strategy in estimating inter-system bias when producing the orbit/clock solutions from simultaneous GPS+GLONASS+Galileo data processing. We

61

CNES–CLS Analysis Center

3-c

3-b

3-a

days
Figure 3: GRG clock solution comparison with BRDM products (GPS in black, GLONASS in
red and Galileo in green). Initial products (3-a), products after alignment of GPS
clocks to BRDC ephemerides (3-b) and products after alignment of GLONASS and
Galileo clocks to BRDM ephemerides (3-c). All clocks expressed in meters.

moved from one inter system bias per satellite-station couple to one per station for Galileo
and one per frequency for GLONASS. The level of the correlations was drastically reduced
and the impact on the clock solution can be seen on Figure 3-b. Second, we included inour clock "alignment" procedure an additional step consisting in applying 1 constant bias
(per daily solution) for GLONASS and Galileo solutions using BRDM MGEX broadcast
information. These additional constraints make possible the use of these GRG products
for timing as it was already the case for GPS clocks. The corresponding solutions are
represented in Figure 3-c.
For more results concerning GRG Multi-GNSS products please refer to the MGEX sectionof this document.

62

5 Perspectives

5 Perspectives
The originality of the CNES-CLS AC processing strategy is to be based on a zero-difference
approach including the so-called “Integer Recovery Clock Model” for GPS products. Using
GRG orbits and clocks with the associated and provided satellite biases enables ambiguity
fixing for single receiver PPP. Our plan is to extend this property to Galileo products. In
addition investigations on the spurious signals affecting GR2 REPRO2 products have to
be finalized in order to be prepared for REPRO3.

63

CNES–CLS Analysis Center

64

JPL IGS Analysis Center
Technical Report 2016
D. Murphy, N. Amiri, W. Bertiger, S. Desai, B. Haines,
D. Kuang, P. Reis, C. Sakumura, A. Sibois, A. Sibthorpe
Jet Propulsion Laboratory
California Institute of Technology
4800 Oak Grove Drive, M/S 238-600
Pasadena, CA 91001, U.S.A.
(dwm@jpl.nasa.gov, +1-818-354-0845)

1 Introduction
In 2016, the Jet Propulsion Laboratory (JPL) continued to serve as an Analysis Center(AC) for the International GNSS Service (IGS). We contributed operational orbit andclock 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 ofEarth rotation parameters (length-of-day, polar motion, and polar motion rates). This
report summarizes the activities at the JPL IGS AC in 2016.
Table 1: JPL AC Contributions to IGS Rapid and Final Products.

Product

Description

Rapid/Final

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

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

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

65

2 Processing Software and Standards
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. Eachof our daily solutions is determined independently from neighboring solutions, namely
without applying any constraints between solutions. High-rate (30-second) Final GPS
clock products are available from 2001 onwards.
The JPL IGS AC also generates Ultra-Rapid orbit and clock products for the GPS constellation. These products are generated with a latency of less than 2.5 hours and are
updated hourly (Weiss et al. 2010). 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/readme.txt.

2 Processing Software and Standards
During 2016, the JPL AC used version 6.4 of the GIPSY/OASIS software package togenerate our contributions to the IGS. This is the latest GIPSY version and supersedesversion 6.3 which was used for our IGS repro2 contribution. In our operations, we haveadopted the data processing approach used for our repro2 reprocessing which had thefollowing improvements from our previous data processing strategy:
1. Application of second order ionospheric corrections (Garcia-Fernandez et al. 2013).
2. Revised empirical solar radiation pressure model named GSPM13 (Sibois et al. 2014).
3. Antenna thrust models per IGS recommendations.
4. Modern ocean tide loading, using GOT4.8 (Ray 2013) (appendix) instead of FES2004(Lyard et al. 2006).
5. GPT2 troposphere models and mapping functions (Lagler et al. 2013).
6. Elevation-dependent data weighting.
A complete description of our current operational processing approach, also used for repro2, can be found at:

ftp://sideshow.jpl.nasa.gov/pub/JPL_GPS_Products/readme.txt
We continue to use empirical GPS solar radiation pressure models developed at JPL
instead of the DYB-based strategies that are commonly used by other IGS analysis centers.
This choice is based upon an extensive evaluation of various internal and external metrics
after testing both approaches with the GIPSY/OASIS software (Sibthorpe et al. 2011).

66

3 GipsyX Overview
GIPSY 6.4 is a relatively minor upgrade over GIPSY 6.3 and provides the following enhancements:
1. Improved geophysical models:a) Second-order ionosphere correction: tweaks to use of IGRF, IRI, IONEX models.
b) GPT model: finer 1◦ resolution and GPT2w a-priori wet delay calculation.
c) Time-varying gravity (including ICGEM format to GIPSY format converter).
2. Improved attitude modeling of GPS block IIF at noon and midnight turns (Kuang
et al. (2013)).
3. Improved reference frame handling with support for large ITRF2014 covariance files.
4. Software upgrades to ninja editor and gd2p PPP tool, several new utilities, bug fixes.
Note that no further release or development in GIPSY is anticipated.

3 GipsyX Overview
For several years we have been developing a replacement to GIPSY called GipsyX which
has the following features:
1. GipsyX is the C++/Python3 replacement for both GIPSY and Real-Time GIPSY(RTG).
2. Driven by need to support both post-processing and real-time processing of multiple
GNSS constellations.
3. Can already process data from GPS, GLONASS, Beidou, and Galileo.
4. Can be easily extended to support DORIS and SLR data processing.
5. Multi-processor and multi-threaded capability.
6. Single executable replaces multiple GIPSY executables: model/oi, filter. smoother,ambiguity resolution.
7. Versatile PPP tool (gd2e) to replace GIPSY’s gd2p.
8. Similar but not identical file formats to current GIPSY.
9. Runs under Linux and Mac OS.
10. GipsyX beta-version released to the GIPSY user community in December 2016.

67

6 Acknowledgments
In parallel with the GipsyX development we have also been developing new Python3
operational software to generate both the rapid and final products that we deliver to the
IGS using GipsyX instead of GIPSY as well as generating our ultra-rapid products thatare available on our ftp site.

4 Testing of GipsyX Operations
We have run extensive tests of our new ‘modern’ operational software that uses GipsyX
shadowing our current legacy rapid and final operational processes for over 10 months andthen comparing our results with both IGS and our legacy GIPSY products. As shown in
Figure 1 and Figure 2 we also ask undertook a longer 2.5 year comparison of the IGS final
products with both our current legacy system (that uses GIPSY) and our new replacement‘modern’ system (that uses GipsyX). The median of daily 3D RMS median differences over
24 hours is 25.5 mm for legacy vs IGS and 25.4 mm for modern vs IGS while the median ofdaily RMS differences across the constellation over 24 hours is 38.6 mm for legacy vs. IGS
and 38.7 mm for modern vs IGS. Thus, we expect our switch to using GipsyX to create our
IGS products to be fully transparent to IGS users and furthermore that GipsyX-generated
products are at least as good as GIPSY-generated products.

5 Future WorkAt the start of GPS week 1934 (29-Jan-17) we will switch to creating all the products
we deliver to the IGS using our new GipsyX-based operational system1 . Also, we aredeveloping an improved solar radiation model for the block IIF GPS satellites as well as
making other enhancements to our data processing, some of which are described in moredetail in our presentations at the IGS 2016 workshop in Sydney. Our longer term goal isto generate other GNSS constellation orbit and clock products using this new software aswell as adding the capability to process other non-GNSS geodetic data.

6 Acknowledgments
The work described in this report was performed at the Jet Propulsion Laboratory, California Institute of Technology under a contract with the National Aeronautics and Space
Administration.
c 2017 California Institute of Technology. Government sponsorship acknowledged.

1

Note: This switch has be made.

68

6 Acknowledgments

Figure 1: Median daily 3D RMS orbit differences. Blue line is JPL GIPSY-based legacy systemversus IGS and green line is JPL GipsyX-based modern system versus IGS.

Figure 2: Daily RMS of clock differences. Blue line is JPL GIPSY-based legacy system versus
IGS and green line is JPL GipsyX-based modern system versus IGS.

69

References

References
Garcia Fernandez, M., S. D. Desai, M. D. Butala, and A. Komjathy (2013), Evaluation ofdifferent approaches to modeling the second-order ionosphere delay on GPS measurements, J. Geophys. Res., 118 (12), 7864-7873, doi:10.1002/2013JA019356.
Kuang, D., S. Desai, A. Sibois (2016), Observed features of GPS Block IIF satellite yaw maneuvers and corresponding modeling, GPS Solu., 21(2), 739-745,
doi:10.1007/s10291-016-0562-9.
Lagler, K. M. Schindelegger, J. Bohm, H. Krasna, and T. Nilsson (2013), GPT2: Empiricalslant delay model for radio space geodetic techniques, Geophys. Res. Lett., 40 (6),1069-1073, doi:10.1002/grl.50288.
Lyard, F., F. Lefevre, T. Letellier, and O. Francis, Modeling the global ocean tides:
Insights from FES2004 (2006), Ocean Dyn., (56), 394-415, doi:10.1007/s10236-0060086-x.
Ray, R. D., Precise comparisons of bottom-pressure and altimetric ocean tides (2013), J.
Geophys. Res., 118, 4570-4584, doi:10.1002/jgrc.20336.
Sibois, A., C. Selle, S. Desai, A. Sibthorpe, and J. Weiss (2014), An update empiricalmodel for solar radiation pressure forces acting on GPS satellites, IGS Workshop,
Pasadena, CA, June 23-27.
Sibthorpe, A., W. Bertiger, S. D. Desai, B. Haines, N. Harvey, and J. P. Weiss (2011), An
evaluation of solar radiation pressure strategies for the GPS constellations, J. Geodesy,
85 (8), 505-517, doi:10.1007/s00190-011-0450-6.
Weiss, J. P., W. Bertiger, S. D. Desai, B. J. Haines, and C. M. Lane (2010), Near real time
GPS orbit determination: Strategies, performance, and applications to OSTM/Jason2, Adv. Astronaut. Sci., 137, 439-452.

70

MIT Analysis Center
Technical Report 2016
T. Herring
Massachusetts Institute of Technology, Cambridge, MA, USA
E–mail: tah@mit.edu
Phone: +1 617 253 5941

1 Introduction
In this report, we discuss results generated by the MIT analysis center (AC) both forsubmissions of weekly final IGS solutions and our weekly combination of SINEX files fromMIT and the other eight IGS analysis centers that submit final SINEX files. We present
here analysis of the networks we process, comparison between our position estimates andthose from other IGS analysis centers, and estimates of GPS satellite phase center offsets(PCO) from our repro2 results.

2 Overview of MIT processing
The MIT analysis for IGS final orbits, clocks and terrestrial reference frame uses the
GAMIT/GLOBK software versions 10.60.003 and 5.29 (Herring et al. 2015). The GAMIT
software uses a double–difference estimator. In order to efficiently process a large global
network sub–networks are used. Each day, 350 stations are included in the combined
network which is composed of seven individual networks each with 50 stations and pairsof stations that couple each sub–network to every other sub–network. These networks are
generated independently each day and depend of the data that is available in the IGS
and other data archives. We search CDDIS, UNAVCO, SOPAC, Geosciences Australia
and BKG for RINEX data. Each network is seeded with four distant sites (not all sites
need to be available) and the seven networks are sequentially filled, first from a list of 378
IGS sites and then from other sites around the world that will fill in regions not coveredby the IGS sites. Sites are added one–at–time to each network rather than making one
complete network before moving the next. The sequential approach makes each network
as globally distributed as possible. Pairs of overlap stations are selected from the stations

71

MIT AC
Table 1: MIT products submitted for weekly finals analysis
File

Description

mitWWWW7.sum.Z
mitWWWW7.erp.Z
mitWWWWn.sp3.Z
mitWWWWn.clk.Z
mitWWWW.snx.Z

Summary file.WWWW is GPS week number.
Earth rotation parameters for 9–days, IGS format
Daily GPS satellite orbits (n=0–6)
Daily GPS satellite clocks (n=0–6)
Daily GPS coordinate and EOP SINEX file.

Table 2: MIT products submitted for daily combinations of IGS final AC SINEX files
File

Description

migWWWWn.snx

Combined sinex file from all available analysis centers (n=0–6,
WWWW GPS week number)
Name of this summary file (n=0–6)
File of the individual AC position estimates residuals to the
combined solution for the week. (n=0–6)

migWWWWn.sum
migWWWWn.res

in each network to join the networks together. No station is used more than twice inthis approach. The network solutions and parameterized orbit models are combined with
the GLOBK software. The GAMIT solutions estimate parameters for the full Bernese
Empirical Code Orbit model (ECOM) (Beutler et al. 1994): 6 initial conditions, 3 constantradiation parameters and 3 pairs of once–per–revolution (OPR) radiation parameters. In
the GLOBK combination stage, we often force the OPR terms for all but the B–axis tozero. The treatment of the OPR terms is based on overlaps between trial solutions withdifferent parameterizations and the estimates and standard deviations of the OPR terms.
Random walk process noise is also assigned to the OPR terms based on the daily solution
variability of the estimated OPR terms. The GAMIT clock solutions, which have not beenused in the IGS clock estimates since mid–2015, are based on un–differenced data analysis
using the MIT orbit, station positions, and Earth orientation parameter estimates. The
clock estimates are generated in a post–processing step using the GAMIT phase cleaning
program.
In addition to weekly final processing, we also generate combined SINEX processing fromthe combination of all eight IGS ACs contributing to the IGS finals. We do this in our roleas an associate analysis center (AAC). All stations submitted by the ACs are included in
MIG combined SINEX file. Covariance matrices or inverted normal equations are scaled
based the root–mean–square (RMS) differences of IGb08 reference frame stations between
each AC solution and the combination all other AC solutions. In Tabular 1 and 2 we list
the products submitted by MIT in our AC and AAC roles.
The network of stations processed by MIT in 2016 is shown in Figure 1. The figure shows72

4 Satellite antenna offset estimates from MIT repro2 processing
the weighted root–mean–square (WRMS) scatter of the horizontal coordinates of nearly
all of the stations included in the MIT finals processing. Stations that were used just a
few times (15 stations in all) are not included in the plot. Only linear trends were removed
from the time series. Figure 2 shows histograms of the WRMS in all three topocentric
coordinates after the removal of linear trends from the time series. The median WRMS
scatters of the 450 sites included in the statistics are 1.5 mm in North and East and 5.9 mm
in height. No annual signals were removed.

3 Position repeatability and comparison to other ACs
We can also compare the MIT daily position estimates with those of other analysis centers
based on the AAC combinations performed at MIT. The MIG combined solution is used forcomparison with the official IGS combination preformed at IGN and generally matches the
IGN solution at the level of 0.1−0.2 mm in north and east (NE) and 0.7−1.0 mm in height(U). The two analyses use different methods to determine AC weighting and different
selection of sites. In Figure 3, we show the WRMS scatter of the daily fits to 60–70 IGb08
reference frame sites from each of the IGS ACs and the combined SINEX solution withthe weights assigned to each AC consistent with the fit of the AC to combination of theother ACs. There is good consistency between the ACs with the exception of the earlypart of the GRC solution which deviates from the other ACs. For the final third of 2016,
the match of the GRC solution improved considerably. While the AC results look similar,
there are differences in the mean of the RMS differences. Table 3 gives the mean RMS
differences for each AC with respect IGb08 and respect to the combination. This tableshows that on average the MIT solution provides a very good match to the combined
solution with sub–millimeter horizontal WRMS and 3.3 mm WRMS in height. We also
compute the chi–squared per degree of the fits and all AC’s have similar chi–squared values
indicaring that no one center dominates the combination.
.

4 Satellite antenna offset estimates from MIT repro2
processing
For the rrepo2 reanalysis, MIT estimated the phase center offsets (PCO) values for all
satellites processed. We have analyzed a new method for estimating the average of valueof the PCOs for different satellite vehicle numbers. The current IGS14 estimates of satellite PCOs are based on time series analysis of daily estimates of the PCO values with theterrestrial frame fixed at the coordinates given in ITRF2014 after accounting for changes
in coordinates of specific stations where new antenna calibrations are used in IGS14. In
our approach, we directly estimate the mean PCO values by combining the MIT loosely

73

MIT AC

60˚

30˚

0˚

−30˚

−60˚
180˚ 270˚

0

1

2

0˚

90˚ 180˚

3

4

5

Horz RMS (mm)Figure 1: RMS scatter of the horizontal position estimates from the network of 435 stations
processed by MIT in 2016. Each daily network has 350 station and the networks
evolve with time depending on data availability and geometry.

constrained SINEX files (actually the GLOBK binary equivalent of these files) in GLOBK.
(We use the original MIT analysis files before the satellite PCO values are constrained to±1mm for submission of the repro2 SINEX files to avoid any additional computational
noise from removing the PCO constraints). Most importantly, in the SINEX combination
we do not constrain the ground station site coordinates or any of the satellite initial conditions or the radiation parameters of the ECOM orbit model. The correlations between
the PCO estimates, satellite clocks and ground station coordinates are high, they are notunity and provided the nadir dependence of satellite phase center variations are held fixed(possibly a big assumption) and the ground antenna calibrations are also held fixed, thistype of solution is possible. However, the high correlations make this solution prone tosystematic errors and time series of the daily estimates do show large, non–white noise
variations. These types of systematics are present even when the terrestrial reference
frame is held fixed.
The results from our estimates are shown in Figure 4 and Table 4. The data analyzed
spanned 1994/01/01 to 2015/08/23 and in all the PCO values for 63 satellites were estimated. In some cases, multiple PRNs have been assigned to the same vehicle and, in thesecases, we have multiple estimates for the same vehicle. Figure 4 shows the differences between our estimates and the IGb08 and IGS14 values adopted by the IGS. Table 4 shows
the values averaged over each block type. The overall average difference from the IGb08
values is −37 mm with an RMS scatter of 33 mm while for IGS14 the average difference
74

220
210
200
190
180
170
160
150
140
130
120
110
100
90
80
70
60
50
40
30
20
10

Number of Stations

Number of Stations

4 Satellite antenna offset estimates from MIT repro2 processing

0

1
2
3
4
NORTH vel_wrms (mm)5Number of Stations

Mean (mm) : 4.75 Sigma (mm) : 17.09 Stations: 450
50% < 1.52 (mm) 70% < 1.84 (mm) 95% < 3.73 (mm)

220
210
200
190
180
170
160
150
140
130
120
110
100
90
80
70
60
50
40
30
20
10
0

1
2
3
4
EAST vel_wrms (mm)5Mean (mm) : 4.82 Sigma (mm) : 17.12 Stations: 450
50% < 1.55 (mm) 70% < 1.81 (mm) 95% < 3.79 (mm)

220
210
200
190
180
170
160
150
140
130
120
110
100
90
80
70
60
50
40
30
20
10
0

2

4
6
8 10 12
UP vel_wrms (mm)14Mean (mm) : 9.03 Sigma (mm) : 16.88 Stations: 450
50% < 5.29 (mm) 70% < 6.24 (mm) 95% < 15.33 (mm)Velocity−Wrms Histogram : FILE: ACREP_2016.sum
Ignore ALLcomponents of : −Ignore UP components
of : −
Figure 2: Histogramof the weighted
root–mean–square (WRMS) scatter of daily position estiIgnore NORTH components of : −Ignore for
EAST2016
components
of : −
mates
after
removal linear trends and elimination of gross outliers (5 times
WRMS scatter.

75

MIT AC
Table 3: Comparison of the fits to the IGb08 reference frame (RF) and daily combined solutions
for RF sites in the MIT and other AC daily final SINEX files. Typically, 65–70 sites areused in the comparison
Center
MIT
COF
EMR
ESA
GFZ
GRG
JPL
NGS
SIO

N (mm)

IGb08
E (mm)U (mm)N (mm)

Combined
E (mm)U (mm)

3.78
3.85
4.47
4.56
4.24
6.47
4.56
3.99
3.87

4.41
4.47
4.29
4.96
5.03
5.81
4.38
4.12
4.18

11.15
10.14
10.45
9.42
10.98
13.05
11.40
10.97
10.93

0.92
1.21
1.06
1.06
1.01
2.52
0.95
1.27
1.39

0.95
1.05
0.80
0.94
1.05
1.55
0.83
1.43
1.53

3.25
3.66
2.86
3.81
3.14
6.12
3.40
3.76
4.13

Fits to Combined

5

COF
EMR
ESA
GFZ
GRG
JPL
NGS
SIO
MIT

N RMS (mm)

4
3
2
1
0
5

COF
EMR
ESA
GFZ
GRG
JPL
NGS
SIO
MIT

E RMS (mm)

4
3
2
1
10
0

COF
EMR
ESA
GFZ
GRG
JPL
NGS
SIO
MIT

U RMS (mm)

8
6
4
2
0

1880

1890

1900

1910

1920

1930

GPS Week

Figure 3: RMS scatters of the fits of the different IGS ACs to the MIG combined solution for2016.

is 20 mm with a smaller RMS of 20 mm.
The implications of our results are we expect a 0.29 ppb scale change from IGb08 (based on
the Zhu et al. (2003)empirical relation of –0.94 ppb for average 121 mm change in satellite
PCO Z–values) and –0.15 ppb scale change from IGS14. This scale change from IGS14

76

References
Table 4: Block mean estimates of the satellite antenna Z–offset estimates. All units are mm.
The values of individual satellites are shown in Figure 4. The mean over all blocks (71satellites) is –36.9 mm, RMS 33 mm for IGb08 and 19.7 mm RMS 20 mm for IGS14.
The standard deviations of the estimates (± column) are white noise estimates fromcombining the SINEX files
Type

#

IGb08

IGS14

BLOCK IBLOCK IIBLOCK IIABLOCK IIR–ABLOCK IIR–B
BLOCK IIR–M
BLOCK IIF

3
9
29
8
4
10
9

–152.50–52.40–54.407.90–17.50–21.80–87.60–62.90
12.10
4.80
46.10
29.80
32.20
8.20

±

6.40
0.40
0.20
0.30
0.50
0.40
0.50

WRMS IGb08

WRMS IGS14

8.20
15.70
14.50
11.10
12.60
15.80
42.20

19.00
13.70
9.70
7.70
12.10
12.30
16.90

would bring the scale inferred from our estimates close to the ITRF2008 scale. One caveat
is that all our results are (as are the IGS14 PCO estimates) generated from processingthat used the IGb08 ground antenna calibration values which have been modified in IGS14
for a number of, but not all, antennas.

References
Herring, T.A., R.W. King, and M.A. Floyd.
GAMIT/GLOBK version 10.60.
Massachusetts Institute of Technology, June, 2015. http://www-gpsg.mit.
edu/∼simon/gtgk/Intro_ GG.pdf
Beutler, G., E. Brockmann, W. Gurtner, U. Hugentobler, L. Mervart, and M. Rothacher.
Extended orbit modeling techniques at the CODE Processing Center of the International GPS Service for Geodynamics (IGS): theory and initial results. Man. Geodaetica, 19, 367–386, 1994
Zhu, S.Y., Massmann, F.–H., Yu, Y., and Reigber, C. Satellite antenna phase center offsets and scale errors in GPS solutions. J Geod 76(11–12):668–672, 2003.
doi:10.1007/s00190–002–0294–1

77MIT AC

100"Z IGb08"Z IGS14

50"Z (mm)

0

-50

-100

-150

-200

0

10

20

30

40

50

60

70

SV number

Figure 4: Estimates of the average satellite antenna Z–offset from the MIT repro2 analysis basedon the combined solution discussed in the text. Multiple estimates from the same satellite vehicle number arise from re–assigned PRN numbers. Only values with standard
deviations less than 50 mm are shown.

78

NGS Analysis Center
Technical Report 2016
S. Yoon, J. Saleh, G. Sella, S. Hilla,
M. Schenewerk, J. Heck, and K. Choi
National Geodetic Survey
1315 East–West Highway, SSMC3
Silver Spring, MD 20910 U.S.A.
E–mail: sungpil.yoon@noaa.gov

1 Introduction
In 2016, NGS continued to serve as an IGS analysis center and a regional data center.
This report summarizes the routine analysis and data center activities conducted at the
National Geodetic Survey (NGS), and all significant changes that occurred during the year2016.

2 Core Analysis Center Products
There were no changes in the NGS analysis center products (see Tabular 1) for 2016.
Please refer to the Analysis Coordinator website (http://acc.igs.org) for combination
statistics of the NGS analysis center products.

3 Analysis Center Processing Software and Strategies
There were no changes to the processing models or strategies for 2016. For details about
the models and strategies used, please refer to the NOAA/NGS Analysis Strategy Summary (ftp://igs.org/pub/center/analysis/noaa.acn).

79

NGS AC
Table 1: NGS Analysis Center Products
Product

Description

Final (weekly)
ngswwwwd.sp3
ngswwwwd.snx
ngswwww7.erp

GPS only
PAGES software suite (5.97 – 5.101)
Orbits, ERP and SINEX

Rapid (daily)
ngrwwwwd.sp3
ngrwwwwd.erp

GPS only
PAGES software suite (5.97 – 5.101)
Orbits, ERP and SINEX
Daily submission for IGR combination

Ultra–Rapid (hourly)
nguwwwwd.sp3
nguwwwwd.erp

GPS only
PAGES software suite (5.97 – 5.101)
Orbits and ERP4 times a day submission for IGU combination

Changes to the processing software and strategies include:• Week 1886 (2016–02–28).

Minor changes for software use under both Sun and Linux OS. No effect upon products.

• Week 1913 (2016–09–04).

Minor changes for software use under both Sun and Linux OS. No effect upon products.Week 1919 (2016–10–16)
Changes making ITRF2014 and IGS14 acceptable options for orbit product production. No effect upon products.

Changes in staff include:• Jacob Heck came on–board.

• Giovanni Sella, who had served as the CORS program manager at NGS, moved on
to other role within NGS in January of 2017 and no longer serves as the CORS
program manager.
Trial production of IGS14 orbit products began with the final products for week 1915.

80

5 Acknowledgments

4 Regional Data Center Core Products
During 2016, NGS contributed data from the following sites to the IGS Network:
Table 2: Site list of NGS contribution to the IGS Network
Site

Location

Lat.

Long.

Receiver Type

System

ASPA
BARH
BRFT
BRMU
CNMR
GUUG
HNPT
USNO
WES2

Pago Pago, ASM
Bar Harbor, ME, USA
Eusebio, BRA
Bermuda, UK
Saipan, CNMI, USA
Mangilao, Guam, USA
Cambridge, MD, USA
Washington, DC, USA
Westford, MA,USA–14.33
44.39
–3.88
32.37
15.23
13.43
38.59
38.92
42.61

–170.72–68.22–38.43–64.70145.74144.80–76.13–77.07–71.49TRIMBLE NETR5
LEICA GRX1200GGPROLEICA GRX1200PRO
LEICA GRX1200GGPROTRIMBLE NETR5
TRIMBLE NETR5
LEICA GRX1200GGPROASHTECH Z–XII3T
SEPT POLARX4TR

G, R
G, R
G
G, R
G, R
G, R
G, R
G
G, R

As a Regional Data Center, NGS also facilitated data flow for the following sites:
Table 3: Site list of NGS contribution as a regional data center
Site

Location

Lat.

Long.

Receiver Type

System

BJCO
GUAT
ISBA
MANA
WUHN

Cotonou, BEN
Guatemala City, GTM
Baghdad, IRQ
Managua, NIC
Wuhan, CHN

6.38
14.59
33.34
12.15
30.53

2.45
–90.5244.44–86.25114.36

TRIMBLE NETR5
LEICA GRX1200GGPROTRIMBLE NETR5
TRIMBLE NETR9
TRIMBLE NETR9

G, R
G, R
G, R
G
G, R

Please refer to the IGS Network website (http://igs.org/network) for site logs, photos,
and data statistics for the sites serviced by the NGS regional data center.

5 Acknowledgments
The analysis and data center teams wish to express our gratitude to NGS management:
Director Juliana Blackwell, Deputy Director Brad Kearse, Division Chief Steve Hilla,
Division Chief Srinivas Reddy and Division Chief Dr. Dan Roman, for their support ofthis work as fundamental activities of NGS. For information about how these activities
fit into NGS plans, see the National Geodetic Survey Ten–Year Strategic Plan 2013–2023(http://geodesy.noaa.gov/web/news/Ten_Year_Plan_2013-2023.pdf)

81

NGS AC82

USNO Analysis Center
Technical Report 2016
S. Byram, V. Slabinski, J. Tracey, J. Rohde
United States Naval Observatory
3450 Massachusetts Avenue Northwest
Washington DC 20392 USA
sharyl.byram@usno.navy.mil

1 Introduction
The United States Naval Observatory (USNO), located in Washington, DC, USA has
served as an IGS Analysis Center (AC) since 1997, contributing to the IGS Rapid andUltra-rapid Combinations since 1997 and 2000, respectively. USNO contributes a fullsuite of rapid products (orbit and clock estimates for the GPS satellites, earth rotation
parameters (ERPs), and receiver clock estimates) once per day to the IGS by the 1600
UTC deadline, and contributes the full suite of ultra-rapid products (post-processed andpredicted orbit/clock estimates for the GPS satellites; ERPs) four times per day by thepertinent IGS deadlines.
USNO has also coordinated IGS troposphere activities since 2011, producing the IGS Final
Troposphere Estimates and chairing the IGS Troposphere Working Group (IGS TWG).
The USNO AC is hosted in the GPS Analysis Division (GPSAD) of the USNO Earth Orientation Department. USNO AC activities, chairing the IGS TWG, and serving on the
IGS Governing Board are overseen by Dr. Sharyl Byram who also oversees production of
the IGS Final Troposphere Estimates. All GPSAD members, including Dr. Victor Slabinski, Mr. Jeffrey Tracey, and contractor Mr. James Rohde, participate in AC efforts.
USNO AC products are computed using Bernese GNSS Software (Dach et al. 2015)1 .
Rapid products are generated using a combination of network solutions and precise point
positioning (PPP; Zumberge et al. (1997)). Ultra-rapid products are generated using
network solutions. IGS Final Troposphere Estimates are generated using PPP.
1

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

83

USNO AC
GPSAD also generates a UT1-UTC-like value, UTGPS, five times per day. UTGPS isa GPS-based extrapolation of VLBI-based UT1-UTC measurements. The IERS2 Rapid
Combination/Prediction Service uses UTGPS to improve post-processed and predicted
estimates of UT1-UTC. Mr. Tracey oversees UTGPS.
USNO rapid, ultra-rapid and UTGPS products can be downloaded immediately after computation from http://www.usno.navy.mil/USNO/earth-orientation/gps-products. IGS
Final Troposphere Estimates can be downloaded at ftp://cddis.gsfc.nasa.gov/gps/
products/troposphere/zpd.

2 Product Performance, 2016
Figures 1-4 show the 2016 performance of USNO rapid and ultra-rapid GPS products,
with summary statistics given in Table 1. USNO rapid orbits had a median weighted
RMS (WRMS) of 18 mm with respect to (wrt) the IGS rapid combined orbits. The
USNO ultra-rapid orbits had median WRMSs of 26 mm (24-h post-processed segment)
and 41 mm (6-h predict) wrt the IGS rapid combined orbits. These values are slightly
degraded compared to the 2015 values (17, 20 and 38 mm).
USNO rapid (post-processed) and ultra-rapid 6-h predicted clocks had median 152 ps and1216 ps RMSs wrt IGS combined rapid clocks, compared to 172 ps and 1201 ps in 2015.
Note the slight improvement in the rapid clock predictions.
USNO rapid polar motion estimates had (x, y) 111 and 74 microarcsec RMS differences
wrt IGS rapid combined values. USNO ultra-rapid polar motion estimates differed (RMS;x, y) from IGS rapid combined values by 156 and 151 microarcsec for the 24-h postprocessed segment. The USNO ultra-rapid 24-h predict-segment values differed (RMS;x, y) from the IGS rapid combined values by 381 and 322 microarcsec. The rapid polar
motion values show significant improvement towards the end of 2016.
The USNO AC began incorporating measurements from the Russian GLONASS GNSS
into processing in 2011 (Byram and Hackman 2012a, b) and has been computing a fullset of test rapid and ultra-rapid combined GPS+GLONASS products since 2012.
In 2016, seven-parameter Helmert transformations computed between USNO and IGS
ultra-rapid GPS+GLONASS orbits had median RMSs of 30 and 60 mm for the 24-h postprocessed and 6-h predict portions, respectively. Meanwhile, the USNO GPS+GLONASS
ultra-rapid 24-h post-processed polar motion x and y values differed from the IGR values,
RMS, by 267 and 129 microarcsec, respectively. USNO GPS+GLONASS ultra-rapid 24-h
predicted polar motion x and y values differed from the IGR values, RMS, by 406 and 307
microarcsec, respectively. These data are shown in Table 2/Figures 5-6.
The USNO AC acquired Bernese 5.2 GNSS Software in 2013 and released the official rapid
2

International Earth Rotation and Reference Systems Service

84References
products generated using it in 2016. The GPS+GLONASS rapid and ultra-rapid solutions
referenced above have been generated using Bernese 5.2 GNSS Software since December
2014.

3 USNO AC Conference Presentations/Publications
USNO AC members presentations/publications are as follows for 2016:
S. Byram and C. Hackman, “IGS Final Troposphere Product Update”. 2016 IGS Workshop, Sydney, Australia, 2016.
V. Slabinski, “LAGEOS Solar Radiation Force: Contribution from Cube-Corner Retroreflection”. 2016 Division on Dynamical Astronomy/AAS Meeting, Nashville, TN, 2016.

References
Byram S., and C. Hackman GNSS-Based Processing at the USNO: Incorporation of
GLONASS Observations. 2012 IGS Workshop, Olstzyn, Poland, 2012a.
Byram S., and C. Hackman High-Precision GNSS Orbit, Clock and EOP Estimation at
the United States Naval Observatory. Proc. 2012 IEEE/ION Position Location andNavigation Symposium, 659-63, 2012b.
Dach, R., S. Lutz, P. Walser, P. Fridez. (eds. ) Bernese GNSS Software Version 5.2. (usermanual) Astronomical Institute of University of Bern, Bern, Switzerland, 2015.
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.

85

USNO AC

Table 1: Precision of USNO Rapid and Ultra-Rapid Products, 2016. All statistics computed withrespect to IGS Combined Rapid Products.
USNO GPSsatellite orbits

USNO GPS–basedpolar motion estimates

USNO GPS–based
clock estimates

Statistic: median weighted
RMS difference
units: mm

Statistic: RMS difference

Statistic: medianRMS difference
units: ps

dates

rapid

1/1/2016–
12/31/2016

18

units: 10–6 arc sec

ultra–rapid
past
6-h
24 h predict

x

26

111

41

rapid
x

ultra–rapid
past 24 4 24-h predict
x
y
x
y

rapid
past
24 h

ultra–rapid
6-h
predict

74

156

152

1216

151

381

322

Table 2: Precision of USNO Ultra-Rapid GPS+GLONASS Test Products, 2016. Orbit statistics computed with respect to IGV Combined Ultra-Rapid GPS+GLONASS Products.
Polar motion statistics computed with respect to IGS Rapid combined values.
USNO GLONASS satellite orbits

USNO GPS+GLONASS polar motion estimatesMedian RMS of 7-parameter Helmert
transformation
units: mm

RMS difference

dates
1/1/2016–
12/31/2016

86

past 24 h

6-h predict

30

60

units: 10–6 arc sec
past 24 hpred 6 hx: 129x: 406

y: 12

y: 307References

WRMS, USNO GPS Orbits wrt IGS Rapid Combination
150

mm

100

50

0
0

50

100

150
200
day of year, 2016

ultra-predultra-past

250

300

350

rapid

Figure 1: Weighted RMS of USNO GPS orbit estimates with respect to IGS Rapid Combination,2016. “Ultra-past” refers to 24-hour post-processed section of USNO ultra-rapid orbits.
“Ultra-pred” refers to first six hours of ultra-rapid orbit prediction.
RMS, USNO GPS Clock Estimates wrt IGS Rapid Combination Clocks
6000

mm

4000

2000

0
0

50

100

150
200
day of year, 2016

ultra-pred

250

300

350

rapid

Figure 2: RMS of USNO GPS rapid clock estimates and ultra-rapid clock predictions with respect
to IGS Rapid Combination, 2016.

87

USNO AC

USNO Rapid Polar Motion wrt IGS Rapid Combination
500
400
300

micro arc sec

200
100
0
-100
-200
-300

-400
-500
0

50

100

150
200
day of year, 2016
dx, rapid

250

300

350

dy, rapid

Figure 3: USNO rapid polar motion estimates minus IGS Rapid Combination values, 2016.
USNO Ultra- Rapid Polar Motion wrt IGS Rapid Combination
1000

micro arc sec

500

0

-500

-1000
0

50

100
dy, pred150
200
day of year, 2016
dx, preddy, past

250

300

350

dx, past

Figure 4: USNO ultra-rapid polar motion estimates minus IGS Rapid Combination values, 2016.

88

References

RMS, USNO GPS+GLO Orbits wrt IGS Ultra-Rapid GPS+GLO
Combination

300

250

mm

200

150

100

50

0
0

50

100

150
200
day of year, 2016

ultra, pred

250

300

350

ultra, past

Figure 5: RMS of USNO ultra-rapid GLONASS orbit estimates with respect to IGS Combined
Ultra-rapid GLONASS orbits, 2016. “Ultra, past” refers to 24-hour post-processed
section of USNO ultra-rapid orbits. “Ultra, pred” refers to first six hours of ultra-rapid
orbit prediction. Helmert transformations computed using Bernese 5.0 Software.
USNO GPS+GLO Ultra- Rapid Polar Motion wrt IGS Rapid
Combination

1000

micro arc sec

500

0

-500

-1000
0

50

100

dy, pred150
200
day of year, 2016
dx, preddy, past

250

300

350

dx, past

Figure 6: Difference between 24-h post-processed polar motion estimates in USNO test ultrarapid GPS+GLONASS solution and IGS “IGU” GPS-only ultra-rapid solution, 2016.

89

WHU Analysis Center
Technical Report 2016
C. Shi, M. Li, Q. Zhao, C. Wang, H. Zhang
GNSS Research Center, Wuhan University, Wuhan, China
E–mail: shi@whu.edu.cn

1 Introduction
The IGS Analysis Center of Wuhan University (WHU) has contributed to the International GNSS Service (IGS) since 2012 with a regular determination of the precise
GPS+GLONASS ultra–rapid and rapid products. All the products are generated withthe latest developed version of the Positioning And Navigation Data Analyst (PANDA)
Software (Liu and Ge 2003; Shi et al. 2008).
During 2016, the standard RAPID product generation was continued with minor changes
in the software PANDA, and we established a Ionosphere Analysis Center and a IGS Data
Center at the GNSS Research Center, Wuhan University. In this report we give a summaryof the IGS related activities at WHU during the year 2016.

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.
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)
of PANDA. In order to speed up the data processing, an efficient approach of removal andrecovery of station coordinate and ambiguity parameters is employed in the least-squares
estimator (Shi et al., 2010). Besides, the ambiguity-fixing can also be performed in either

90

4 IGS Data center from WHU
network mode or precise point positioning mode, significantly improving the positioning
accuracy of WHU products.

3 WHU Analysis Products
The list of products provided by WHU is summarized in Table 1.
Table 1: List of products provided by WHU.

WHU rapid GNSS products
whuWWWD.sp3
whuWWWD.clk
whuWWWD.erp

Orbits for GPS/GLONASS satellites
5-min clocks for stations and GPS/GLONASS satellites
ERPs
WHU ultra-rapid GNSS products

whuWWWD_HH.sp3
whuWWWD_HH.erp

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

4 IGS Data center from WHU
The IGS Data Center from WHU has been designed and implemented in answer to global
and especially Chinese users, for both post-processing and real-time applications. The
GNSS observations both IGS and MGEX from all the IGS network stations, as well as the
IGS products are archived and available at WHU IGS Global Data Center. So as to have amore reliable data flow and a better availability of the service, two identical configurations
with the same data structure have been setup in Alibaba cloud and Data Server of WHU
University. Each configuration has:
• FTP access to the GNSS observations and products ( ftp://igs.gnsswhu.cn/ ).
• access to the GNSS observations and products ( http://igs.gnsswhu.cn/ ).

In order to ensure the integrity of the observation data and the product, we compare
the daily data, hourly data and products with CDDIS. If a data file is missing, we will
download it from CDDIS again. Figure 1 shows status of daily observation.

91

WHU AC

Figure 1: Status of daily observations.

5 Ionosphere Activities
WHU are making efforts to boost the ability of processing GNSS data for generating
global ionosphere maps over these years. WHU joined IGS Ionosphere Working Group as
an Ionosphere Associate Analysis Center in 2016, and has been providing various kindsof ionosphere products since 2016, such as rapid products, hourly products and final
products. New algorithms are proposed to improve the quality of ionosphere maps. For
instance, inequality-constrained least squares method is proposed to eliminate negative
VTEC values in global ionosphere maps (Zhang et al. 2013). Meanwhile, WHU use IRI
model to generate VTEC values where GNSS signals are not available (Wang et al. 2016).
VTEC maps (from 1998 to 2016) are assessed through comparisons between IAACs’ products and IGS final GIMs, as shown in Figure 1. The VTEC maps in IONEX format canbe downloaded from the FTP of WHU ionosphere products: ftp://pub.ionosphere.cn.
A software platform is built for data processing and ionosphere analysis. This platform
is comprised of function modules, including downloading global GNSS data, preprocessing and processing data, graphical visualization of TEC maps, releasing the ionosphere
products, real-time delivering operating status of data processing as well as updating website. The website (http://ionosphere.cn) is established and maintained for the displayof VTEC maps, DCB values and the other information. English version of the website
will be updated soon. Besides, the efficiency of global ionospheric modeling is improvedby using distributed computers with both desktops and servers in different two network92

5 Ionosphere Activities

Figure 2: The RMS differences between IAACs’ VTEC and GIMs from 1998 to 2016.

Figure 3: Test of global ionospheric modeling by using distributed computers.

segments. The time consumption of ionosphere modeling with different combination of
distributed computers is presented in Figure 2. The efficiency of modeling is promoted
apparently by using more computers. It’s very helpful for algorithm testing of modeling,
fast releasing of ionosphere products, post-time verification and prediction. However, it
is better that the computers are installed in the same network segment so as to decrease
the time consumption of data communication.

93

WHU AC
Recently, WHU develops software for editing the ionosphere products in IONEX format (called INX Editor). It supports Windows, Linux and Mac OS. INX Editor could
edit and generate ionosphere products with customized interval, latitudes and longitudes.
Moreover, it could convert the ionosphere products from IONEX format to binary format
or from binary format to IONEX format. Figure 3 shows the operation instructions of
INX Editor. Please consult the detailed introduction to this software by this webpage(http://ionosphere.cn/inx.html).

References
Liu J., and M. Ge PANDA software and its preliminary result of positioning and orbit
determination. Wuhan University Journal of Natural Sciences, 8(2):603-609, 2003.
Shi C.,Q. Zhao,J. Geng,Y. Lou,M. Ge, and J. Liu Recent development of PANDA softwarein GNSS data processing. In: Proceeding of the Society of Photographic Instrumentation Engineers, 7285, 72851S. 2008 doi: 10.1117/12.816261
Zhang H., P. Xu, W. Han, M. Ge, and C. Shi Eliminating negative VTEC in global ionosphere maps using inequality-constrained least squares Advances in Space ResearchVol. 51( 6):988-1000, 2013.
Wang C., C. Shi, H. Zhang, and L. Fan Improvement of global ionospheric VTEC maps
using the IRI 2012 ionospheric empirical model Journal of Atmospheric and SolarTerrestrial Physics Vol. 146:186-193, 2016.

94

EUREF Permanent Network
Technical Report 2016
C. Bruyninx1 , A. Araszkiewicz2 , E. Brockmann3 , A. Kenyeres4 ,T. Liwosz5 , R. Pacione6 , W. Söhne7 , G. Stangl8 ,K. Szafranek2 , C. Völksen9
1
2
3
4
5
6
7
8
9

Royal Observatory of Belgium (ROB), Av. Circulaire, B–1180 Brussels, Belgium
E–mail: C.Bruyninx@oma.be
Military University of Technology, Warsaw, Poland
Federal Office of Topography swisstopo, Wabern, Switzerland
FOMI Satellite Geodetic Observatory, Budapest, Hungary
Warsaw University of Technology, Warsaw, Poland
E-GEOS Centro di Geodesia Spaziale (ASI/CGS), Matera, Italy
Federal Agency for Cartography and Geodesy (BKG), Frankfurt am Main, Germany
Institute for Space Research, Graz, Austria
Bavarian Academy of Sciences and Humanities, München, Germany

1 Introduction
The International Association of Geodesy Regional Reference Frame sub–commission for
Europe, EUREF, defines, provides access and maintains the European Terrestrial Reference System (ETRS89). This is done through the EUREF Permanent GNSS Network(EPN). EPN observation data as well as the precise coordinates and the zenith total delay(ZTD) parameters of all EPN stations are publicly available. The EPN cooperates closelywith the International GNSS Service (IGS); EUREF members are e.g. involved in the IGS
Governing Board, the IGS Real–Time Working Group, the IGS Antenna Working Group,
the IGS Troposphere Working Group, the IGS Infrastructure Committee, and the IGS
Multi–GNSS Working Group and Experiment (MGEX). This paper gives an overview ofthe main changes in the EPN during the year 2016.

95

EPN RNAAC

2 New EPN CB web site and monitoring
End of November 2016, the brand new EPN Central Bureau web site (http://epncb.eu/)
was opened to the public. The improved web site has an extended station list with morestation metrics, extended GNSS data quality checks (multi–GNSS) on both RINEX 2 and
RINEX 3, improved station position time series, extended GNSS data availability andlatency checks on both RINEX 2 and RINEX 3, full implementation of long RINEX3
station names, and extended monitoring of real–time data streams. In addition, theweb site has a new responsive design to allow an improved visualization on tablets andsmartphones.
Together with the metadata of the EPN densification network (see http://epncb.eu/_densification), the EPN CB now maintains and distributes centrally the metadata of
1479 European GNSS stations.

3 Tracking Network
Nineteen new stations were integrated in the EPN network in 2016 (see Table 1), bringing
the total number of EPN stations to 294 (Figure 1 and Table 1) from which 32% belong
to the IGS. The majority of the new EPN stations has individual antenna calibrations.
End of 2016, 84% of the EPN stations provide GPS+GLONASS data and 35% provide
Galileo data.

4 EUREF Working Group on “Multi–GNSS”
The EUREF Working Group on “Multi–GNSS” stimulates EUREF members to be actively
involved in multi–GNSS activities. Figure 2 shows the improvement in data submissions
using RINEX 3 data. Among the 332 EPN stations that delivered RINEX 2 data in
December 2016, 147 also delivered RINEX 3 data. Unfortunately, the majority of RINEX
meteo files are submitted using the old short file names. An example for the long file nameconvention of meteo RINEX 3 files was finally added to the RINEX 3 format description
in November 2016.
Working Group members are also developing the GNSS software packages enabling multi–
GNSS data quality checks: G–Nut/Anubis [1.2.1] (Václavovic and Dousa 2016) and BNC[2.12] (Weber et al. 2016). The results of their application can be seen on e.g. http://
www.pecny.cz/GOP/index.php/gnss/data-center/eur-rnx3, http://pnac.swisstopo.
admin.ch/pages/en/anubis_monitor_r3.html, and at the EPN Central Bureau http://epncb.eu/_networkdata/data_quality/.
End of July 2016, the first EPN Analysis Center (swisstopo; LPT; EUREF Mail 8644)

96

4 EUREF Working Group on “Multi–GNSS”

0˚

20˚

˚
40

50
˚

˚

˚

−20

60

−4
0˚

50
˚

40

˚

40˚

30˚

30˚

−20˚

20˚

0˚

Figure 1: EPN tracking stations, status December 2016. * indicates new stations included in the
network in 2016.

160
RINEX 3100

RINEX 3.02 or 3.03
long RINEX filenames

70
40

2017

2015

10
2016

Number stations

130

Year
Highcharts.com

Figure 2: Number of stations providing RINEX 3 files in the EPN.

97

EPN RNAAC
Table 1: New stations included in the EPN in 2016 (stations indicated with * also contribute to
the IGS)
4–char ID

Location

Tracked Satellite Systems

Real–
time

AUBG
CAG1
CASE
DIEP
DILL
GELL
GOR2
HEL2
HOFJ
IJMU
IRBE
KIR8*
KOS1
LEIJ*
MAR7*
ONS1*
SAS2
VLIS
WRLG

Augsburg, DEU
Calgiary, ITA
Cassa de la Selva, ESP
Diepholz, DEU
Dillingen, DEU
Gellin, DEU
Gorleben, DEU
Helgoland Island, DEU
Hof, DEU
Ijmuiden, NLD
Irbene, LVA
Kiruna, SWE
Kootwijk, NLD
Leipzig, DEU
Gavle, SWE
Onsala, SWE
Sassnitz Island, DEU
Vlissingen, NLD
Bad Koetzting, DEU

GPS GLO GALGPS GLO GAL BDSGPS GLO GAL BDSGPS GLO GALGPS GLO GALGPS GLO GALGPS GLO GALGPS GLO GALGPS GLO GALGPS GLOGPS GLO GALGPS GLO GAL BDSGPS GLO GAL BDS QZSSGPS GLO GAL BDSGPS GLO GAL BDSGPS GLO GAL BDSGPS GLO GAL BDSGPS GLOGPS GLO GAL

X

X
X
X
X
X

Antenna Calibration
Individual (robot)
Type mean
Individual (robot)
Individual (robot)
Individual (robot)
Individual (robot)
Individual (robot)
Individual (robot)
Individual (robot)
Individual (robot)
Type mean
Individual (robot)
Individual (robot)
Individual (robot)
Individual (robot)
Individual (robot)
Individual (robot)
Individual (robot)
Individual (chamber)

Tropo [mm]Up [mm]East [mm]North [mm]ZIM2: Intersystem Translation Parameters
20
15
10
5
0
-5
-10
-15
-20
200
20
15
10
5
0
-5
-10
-15
-20
200
40
30
20
10
0
-10
-20
-30
-40
200
20
15
10
5
0
-5
-10
-15
-20
200

C: -0.58 +- 1.86 mm

220

E: -0.51 +- 1.03 mm

240

C: -1.29 +- 2.42 mm

220

240

260

240

260

280

260

320

340

300

320

340

320

340

320

340

R: -0.83 +- 2.73 mm

280

E: -0.42 +- 1.75 mm

240

300
R: -0.09 +- 0.53 mm

E: -5.62 +- 4.34 mm

C: -2.26 +- 1.80 mm

220

280

E: -0.82 +- 0.76 mm

C: 2.13 +- 5.24 mm

220

260

R: -1.45 +- 0.55 mm

300
R: -0.08 +- 0.93 mm

280

300

Figure 3: Daily Intersystem parameters for station ZIM2 for 125 days between August 1 andDecember 3 (differences of the coordinate and troposphere results of GLONASS (R),
Galileo (E) and BeiDou (C) with respect to GPS (G)985 Data Analysis
started to submit solutions including Galileo and BeiDou data in addition to GPS andGLONASS using the development version Bernese GNSS Software (BSW), version 5.3.
“Only” 15% additional observations are used compared to a GPS/GLO processing. The
coordinate differences derived from a seven weeks parallel processing are small: Helmert
standard deviation of about 0.3 mm in the horizontal and 0.7 mm in the vertical component. Figure 3 shows an example of the daily intersystem parameters for the station
ZIM2. In extreme cases, usually with special antenna constructions, differences can reachseveral centimetres: -−35 mm vertical differences GPS–GLO for TRF2, horizontal differences GPS–GAL of more than 5 mm for OBE4, or the same magnitude for LINZ in caseof horizontal coordinates GPS–BDS. Depending on the number of observations involved,
a coordinate adjustment forcing estimation of a unique GPS/GLO/GAL/BDS value cantherefore lead to different estimates between analysis centres using different satellite systems.

5 Data Analysis
5.1 Positions
The EPN Analysis Centres (AC) routinely process GNSS observations collected at EPN
stations. In 2016, all 16 ACs (Table 2) were providing final weekly and daily coordinate
solutions of their subnetworks, 10 ACs were providing also rapid daily solutions, and 3
ACs were providing ultra–rapid solutions. In 2016, LPT AC switched from a two system(GPS, GLONASS) to a four system (GPS, GLONASS, Galileo and BeiDou) processing
scheme for its final products (see Section 4 for more details), and SUT AC switched theprocessing software from BSW version 5.0 to version 5.2. Also, IGN AC started providing
final daily coordinate solutions of its subnetwork.
The Analysis Combination Centre (ACC) continued to combine the AC’s subnetwork
solutions (provided in SINEX format) into official EPN solutions. In 2016, the ACC
prepared new reports on final weekly and daily combinations and created new scripts forchecking the correctness of receiver/antenna information given in AC SINEX files (stations
with inconsistencies are excluded from the combination). Since January 2016, the reports
from the weekly combinations are available on the EPN ACC website www.epnacc.wat.
edu.pl), see (EPN LAC mail 2014).
At the end of 2016, the method for creating weekly combined EPN solutions was changed.
Up to and including week 1924, the weekly combined solutions were created directly fromthe AC weekly solutions. Since week 1925 (November 27–December 4, 2016), the daily
AC solutions are used for that purpose; at first the daily AC solutions are combinedfor each day of the week, and then the seven daily combined solutions are stacked into aweekly solution. The new approach consistently handles position outliers (for both AC andcombined solutions) at the daily level, and mitigates inconsistencies between AC solutions,99

EPN RNAAC
Table 2: EPN Analysis Centres characteristics: provided solutions (W – final weekly, D – final
daily, R – rapid daily, U – ultra–rapid), the number of analyzed GNSS stations (in brackets: stations added in 2016), used software (GOA – GIPSY–OASIS, BSW – Bernese
GNSS Software), used GNSS observations (G – GPS, R – GLONASS, E – Galileo, C –BeiDou)AC

Analysis Centre Description

Solutions# sites

Software GNSS

ASI
Centro di Geodesia Spaziale G. Colombo, ITAW, D, R, U 50 (0)GOA 6.2 G
BEK Kommission für Erdmessung und Glaziologie, DEU W, D, R
95 (11) BSW 5.2 G, R
BKG Bundesamt für Kartographie und Geodäsie, DEU W, D, R, U 109 (15) BSW 5.2 G, R
COE Center for Orbit Determination in Europe, CHE
W, D
43 (0)
BSW 5.3 G, R
IGE Instituto Geografico Nacional, ESP
W, D, R78 (1)
BSW 5.2 G, R
IGN Institut Geographique National, FRAW, D, R64 (0)
BSW 5.2 G
LPT Federal Office of Topography swisstopo, CHE
W, D, R, U 59 (4)BSW 5.3 G,R, E, C
MUT Military University of Technology, POL
W, D
137 (3) BSW 5.2 G, R
NKG Nordic Geodetic Commission, Lantmateriet, SWE W, D
76 (7)
BSW 5.2 G, R
OLG Austrian Academy of Science, AUTW, D
103 (2) BSW 5.2 G
RGA Republic Geodetic Authority, SRB
W, D
56 (0)
BSW 5.2 G, R
ROB Royal Observatory of Belgium, BEL
W, D, R84 (12) BSW 5.2 G, R
SGO FOMI Satellite Geodetic Observatory, HUNW, D, R42 (0)
BSW 5.2 G, R
SUT Slovak University of Technology, SVK
W, D
56 (8)
BSW 5.2 G, R
UPA University of Padova, ITAW, D, R
49 (2)
BSW 5.2 G, R
WUT Warsaw University of Technology, POL
W, D, R
106 (5) BSW 5.2 G, R

which are observed when combining on a weekly level. The comparison for 70 weeks (1831–
1900) showed that differences in weekly station positions between both approaches canreach in extreme cases up to 14 mm for horizontal components and up to 20 mm for verticalcomponent. Apart from these cases, both approaches for creating weekly solutions werehighly consistent: about 93% of station position residuals for horizontal components were
smaller than 0.1 mm, and about 90% of vertical residuals were smaller than 0.25 mm.
The weekly and daily analysis reports were updated accordingly to reflect this change incombination strategy.
The long–term combination, performed every 15 weeks, is compared to the national realizations of ETRS89 used in the different the countries. The difference plots, available under
http://epncb.oma.be/_productsservices/coordinates/img/ETRF_EPN_HOR.JPG
and http://epncb.oma.be/_productsservices/coordinates/img/ETRF_EPN_UP.JPG
show clearly the homogeneous implementation of the various ETRS89 realizations in Europe.

5.2 Troposphere
Beside station coordinates, the 16 ACs also submit ZTD parameters on a routine basis in
SINEX_TRO format. Fourteen ACs are also submitting horizontal gradients. The ZTDs
and horizontal gradients are delivered with a sampling rate of 1 hour, on a weekly basis

100

5 Data Analysis
but in daily files. As regard to the troposphere mapping function, eight of the 16 ACs use
the Vienna Mapping Function, and the remaining eight the Global Mapping Function.
In 2016, the ZTD estimates are provided for 280 stations by three or more ACs (compared
to 260 in 2015)), for 10 stations by two, and for 6 stations just by one AC.
http://epncb.eu/_productsservices/sitezenithpathdelays/ shows the weekly mean
bias (top) and the related standard deviation (bottom). They give insight into the agreement of the individual solutions with respect to the combined solution. The time series are
based on EPN–Repro2 solutions (GPS week 834 until 1824) and on operational solutions
afterwards.

5.3 Reprocessing
Within the Working Group “EPN Reprocessing” several strategies have been tested during
the past years and finally the EPN–Repro2 reprocessing was finalized in 2016 using ananalysis strategy based on agreed parameters, which were largely consistent with thestrategies of the IGS. The entire EPN network was processed with BSW 5.2, GAMIT
10.5 and GIPSY 6.2 and two large subnetworks of the EPN were analyzed with BSW 5.2.
Each AC provided daily coordinates and troposphere parameters for their network as wellas weekly solutions for the period 1996 until spring 2013. The combination of the daily
and weekly solutions, done by the ACC, has proven that the individual solutions are very
homogeneous. The main difference between some of the strategies was the application ofindividual antenna calibration correction models or type mean corrections only. While
the IGS applies only type mean corrections, the EPN considers also individual corrections
when available. The impact of these different antenna models was analyzed and it has beenshown that the impact on the reference frame is negligibly small for the EPN (Araszkiewicz
and Völksen 2016). The SINEX files of the individual ACs and the combined productsof the ACC are available from the data server at the BKG.
In parallel, a tropospheric combined solution for the period 1996–2014 has been computed(Pacione et al. 2016). For each EPN station, plots on ZTD time series, ZTD monthly
mean, comparison versus Radiosonde data (if collocated), are available at the EPN Central
Bureau (http://epncb.eu/_productsservices/troposphere/).
The EPN–Repro2 tropospheric products (Pacione 2016) have been evaluated against
radiosonde data and European Centre for Medium–Range Weather Forecasts (ECMWF)
reanalysis (ERA–Interim) data. Assessment of the EPN–Repro1 and Repro2 with respect
to radiosonde data shows an improvement of approximately 3–4% in the overall standard
deviation. Evaluation of the EPN–Repro1 and Repro2 with respect to the ERA–Interim
re–analysis showed the 8–9% improvement of the latter over the former in both, overall
standard deviation and systematic error. EPN–Repro2 will be used as a reference data
set for climate monitoring over Europe in cooperation with the COST Action ES1206’GNSS4SWEC’.

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EPN RNAAC

6 Densification of the IGS and EPN
Based on the EPN combined weekly SINEX solutions (back to mid–1996), a multi–year
EPN position and velocity solution is maintained as the densification of the IGS realizationof the ITRS in Europe. This solution is computed with the CATREF software, tied to
IGb08, and is updated each 15 weeks. Following the publication of ITRF2014, a new
multi–year EPN solution including EPN–Repro2 has been computed for test purposes
and prepared for implementation (Kenyeres et al. 2016a)). The final computation andpublication will be done, when the IGS realization of ITRF2014 will be published. The
EPN multi–year product files (including a discontinuity table and associated residual
position time series) are available at ftp://epncb.eu/pub/station/coord/EPN. Moredetails can be found in http://epncb.eu/_productsservices/coordinates/.
EUREF also combines the weekly SINEX solutions provided by European countries fortheir dense national active GNSS networks with the weekly EPN SINEX solution. Allavailable weekly combined solutions are stacked to obtain a consistent cumulative position/velocity solution. Both combinations (the weekly and the multi–year) are also
performed using the CATREF software applying exactly the same approach and parameters as for the generation of the EPN IGb08 densification ensuring full consistency fromthe global to the local level. The total number of stations included in the EPN densification exceeds 3000 as of December 2016. Two contributions (IGN, France and BIGF, UK)
are global solutions and therefore the EPN densification shall be considered as a global
solution.
The densification products will be an essential contribution to several groups and projects
as the European Plate Observing System (EPOS) and the European Positioning System(EUPOS). This work is still in progress (see Kenyeres et al. (2016b)).

7 Stream and Product Dissemination
While the number of EPN stations grew also in 2016, the number of EPN stations providing
real–time data could not keep the pace. Beside possible technical restrictions, the main
reason seems to be related to financial or commercial restrictions.
The number of stations providing real–time observation streams in the RTCM 3.2 Multiple
Signal Messages (MSM) format grew significantly. However, almost all of the streams were
provided as raw data streams, so that a conversion tool has to be applied to derive RTCM
messages. As of end of November 2016, 17 EPN stations were providing RTCM 3.2 data
streams, the majority available from the MGEX caster of BKG, http://mgex.igs-ip.
net. In addition to GPS and GLONASS, most of the streams contain Galileo, BeiDou,
QZSS and SBAS.
The monitoring of the three EUREF broadcasters at the EPN Central Bureau was ex-102References
tended. In addition to the RTCM 2 and 3.1 format, also the RTCM 3.2 data stream content is now verified against the proposed content of the sourcetable, see http://epncb.
eu/_networkdata/data_access/real_time/.

References
Araszkiewicz A., and C. Völksen The impact of the antenna phase center models on
the coordinates in the EUREF Permanent Network. GPS Solutions, 1–11, 2016
doi:10.1007/s10291–016–0564–7
Kenyeres A., T. Horvath, C. Völksen, R. Pacione, K. Szafranek, A. Araszkiewicz, J. Dousa,
D. Ineichen, E. Brockmann, and M. Valdes Densification with EPN REPRO–2: First
Experiences Presented at the EUREF2016 Symposium, San Sebastian, Spain, 25–27
May, 2016a
Kenyeres A., A. Araszkiewicz, A. Baron, C. Bruyninx, A. Caporali, N. D’Agostino, A. Deprez, F. De Doncker, B. Droscak, A. Duret, S. Ergintav, P. Franke, I. Georgiev,
D. Hansen, L. Huisman, O. Khoda, D. Mesmaker, K. Morozova, J. Nagl, X. Papanikolaou, P. Pihlak, A. Socquet, G. Stangl, and M. Valdes Integration of the European
CORS Network SINEX Products to Serve Geodetic and Geophysical Needs Presented
at the WEGENER 2016 Symposium, Ponta Delgada, Azores, Portugal, 12–15 September, 2016b September, 2016b
Pacione R., A. Araszkiewicz, E. Brockmann, and J. Dousa EPN Repro2: A reference
GNSS tropospheric dataset over Europe Atmos. Meas. Tech. Discuss., in review,
2016 doi:10.5194/amt–2016–369
Pacione R. EPN Repro2 time series dataset 2016 doi: 10.13140/RG.2.2.25297.33122
Václavovic P., and J.X Dousa G–Nut/Anubis – open–source tool for multi–GNSS
data monitoring, In: IAG 150 Years, Rizos Ch. and Willis P. (eds), International Association of Geodesy Symposia, Springer, Vol. 143, pp. 775–782, 2016,
doi:10.1007/1345_2015_97
Weber G., L. Mervart, A. Stürze, A. Rülke, D. Stöcker BKG Ntrip Client (BNC) Version
2.12 Mitteilungen des Bundesamtes für Kartographie und Geodäsie, Band 49, 2016
ISBN 978–3–86482–083–0

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EPN RNAAC

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SIRGAS Regional Network Associate
Analysis Centre
Technical Report 2016
L. Sánchez
Deutsches Geodätisches Forschungsinstitut
der Technischen Universität München (DGFI-TUM)
Arcisstr. 21, 80333 München, Germany
E-Mail: lm.sanchez@tum.de

1 Introduction
The SIRGAS Reference Frame is currently composed of 411 continuously operating GNSS
stations (Figure 1). It comprises two hierarchy levels (Brunini et al. 2012): a core network (SIRGAS-C, Sánchez et al. (2015a)) providing the primary link to the global ITRF;
and national reference networks (SIRGAS-N) improving the geographical density of thereference stations to ensure the accessibility to the reference frame at national and local
levels. The SIRGAS reference stations are processed by 10 SIRGAS processing centres(Cioce et al. 2016a):• Deutsches Geodätisches Forschungsinstitut der Technischen Universität München(Germany), Sánchez (2016)• CEPGE: Centro de Procesamiento de Datos GNSS del Ecuador, Instituto Geográfico
Militar (Ecuador)• CNPDG-UNA: Centro Nacional de Procesamiento de Datos GNSS, Universidad Nacional (Costa Rica), Moya et al. (2016)• CPAGS-LUZ: Centro de Procesamiento y Análisis GNSS SIRGAS de la Universidad
del Zulia (Venezuela), Cioce et al. (2016b)• IBGE: Instituto Brasileiro de Geografia e Estatistica (Brazil)• IGAC: Instituto Geográfico Agustń Codazzi (Colombia)• IGM-Cl: Instituto Geográfico Militar (Chile), Parra (2016)
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SIRGAS Associate Analysis Center• IGN-Ar: Instituto Geográfico Nacional (Argentina)• INEGI: Instituto Nacional de Estadística y Geografía (Mexico)• SGM: Servicio Geográfico Militar (Uruguay), Suárez (2016)

2 Routine processing of the SIRGAS reference frame
The SIRGAS processing centres follow unified standards for the computation of loosely
constrained weekly solutions for the station positions. These standards are generally basedon the conventions outlined by the IERS and the GNSS-specific guidelines defined by the
IGS; with the exception that in the individual SIRGAS solutions the satellite orbits andclocks as well as the Earth orientation parameters (EOP) are fixed to the final weekly IGS,
and positions for all stations are constrained to ±1 m (to generate the loosely constrained
solutions in the SINEX format). INEGI (Mexico) and IGN-Ar (Argentina) employ thesoftware GAMIT/GLOBK (Herring et al. 2010); the other local processing centres use
the Bernese GPS Software V. 5.2 (Dach et al. 2015). The processing standards appliedat present are described in (Sánchez and Drewes 2016). The individual solutions are
combined by the SIRGAS combination centres operated by the DGFI-TUM (Sánchez
et al. 2012; Sánchez 2016) and the IBGE (Costa et al. 2012). In charge of the IGS
Regional Network Associate Analysis Centre for SIRGAS (IGS RNAAC SIRGAS), DGFITUM processed the entire SIRGAS reference network from June 1996 until August 2008
(Brunini et al. 2012; Sánchez et al. 2012). Now, it is responsible for• processing the SIRGAS-C core network (Figure 1), Sánchez (2016)• combining the core network with the national reference networks (Figure 2 and 3),
Sánchez (2016);• ensuring that the SIRGAS processing strategy meets the IERS standards and IGS
guidelines;• developing strategies to guarantee the reliability of the reference frame over time, thisincludes the estimation of the reference frame kinematics (Figure 4) and modelling
crustal deformation in the SIRGAS region (Figure 5), Sánchez and Drewes (2016);• making available the SIRGAS products via www.sirgas.org and ftp.sirgas.org.

At present, the SIRGAS efforts are concentrated on the second reprocessing of the reference
network backwards until January 1997 using the IGS14 as the reference frame.

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2 Routine processing of the SIRGAS reference frame

240˚

270˚

330˚

300˚

SIRGASREFERENCE
NETWORK30˚

30˚

2017-01-18

0˚

-30˚

0˚

-30˚

SIRGAS-C core network
SIRGAS - N national networks

-60˚

-60˚
IGS RNAAC SIRGAS

Deutsches Geodaetisches Forschungsinstitut (DGFI-TUM)

240˚

270˚

300˚

330˚

Figure 1: Core and national networks within the SIRGAS Reference Frame (January 2017)107

SIRGAS Associate Analysis Center

Loosely
constrained
SINEX files

Removing
constraints
Free Normal
Equations (NEQ)

Solution of individual NEQ
wrt IGS Reference Frame

Residual analysis- Detection of outliers- Thresholds: ±10 mm in N or E,± 20 mm in Up
Accumulation of NEQ- outliers removed- variance factors included

Weekly solution aligned to IGS Frame- IGS weekly positions for IGS ref. stations- Constraints to reference positions
for datum realisation

Validation of the individual
stochastic models for relative
weighting (variance factors)

Loosely constrained solution(all coordinates constrained to ±1 m)
for the IGS global polyhedron andfor multi-year solutions

Quality control of the weekly coordinates- formal errors- time series analysis- comparison with IGS weekly coordinates
and with IBGE weekly combinations

Figure 2: DGFI-TUM strategy for the combination of the weekly solutions delivered by the
SIRGAS processing centres

3 Crustal deformation and surface kinematics after the 2010
earthquakes in Latin America
The Maule 2010 earthquake in Chile generated the largest displacements of geodetic observation stations ever observed in terrestrial reference frames (Sánchez et al. 2013). Coordinates changed by up to 4 m, and deformations were measurable in distances of up
to more than 1000 km from the epicentre. The station velocities in the regions adjacentto the epicentre changed dramatically after the seism; while they were oriented eastward
with approximately 2 cm/y before the event, they are now directed westward with about
1 cm/y (Sánchez et al. 2015a). The 2010 Baja California earthquake in Mexico caused
displacements on the dm level also followed by anomalous velocity changes. To ensure
the long-term stability of the SIRGAS reference frame, the transformation of station positions between different epochs requires the computation of reliable continuous surface
deformation (or velocity) models. To achieve this objective, DGFI-TUM, acting as the
IGS RNAAC SIRGAS, computed a new continental continuous crustal deformation modelfor Latin America and the Caribbean inferred from GNSS (GPS+GLONASS) measurements gained after the strong earthquakes occurred in 2010. It is based on a multi-year
velocity solution for a network of 456 continuously operating GNSS stations and covering
a five years period. This new deformation model, called VEMOS2015 (Velocity Modelfor SIRGAS 2015), is computed using the least square collocation (LSC) approach with
empirically determined covariance functions as shown in Sánchez and Drewes (2016). The
result is summarised as follows: While the effects of the Baja California earthquake can108

3 Crustal deformation and surface kinematics after the 2010 earthquakes in Latin
America

7.5

N [mm]

E[mm]

Up[mm]

6.5
5.5
4.5
3.5
2.5
1.5
0.5
DGFI-DE

IGM-CLIGM-ECIGN-AR

7.5

IBGE-BR IGAC-CO INEGI-MX LUZ-VE

N [mm]UNA-CR SGM-UY

E[mm]

Up[mm]

6.5
5.5
4.5
3.5
2.5
1.5
0.5
DGFI-DE

IGM-CLIGM-ECIGN-AR

IBGE-BR IGAC-CO INEGI-MX LUZ-VE

UNA-CR SGM-UY

DGFI-DE IGM-CL

IGM-ECIGN-AR IBGE-BR IGAC-CO INEGI-MX LUZ-VE UNA-CR SGM-UY

[mm]
2.0

1.8

1.6

1.4

[mm]
2.0

1.8

1.6

1.4
DGFI-DE IGM-CL

IGM-ECIGN-AR IBGE-BR IGAC-CO INEGI-MX LUZ-VE UNA-CR SGM-UYa) Mean RMS values for the weekly repeatabilityof the station positions within the SIRGAS processing centre solutions: about ± 1.8 mm in the
North and the East, and ± 3.5 mm in the height.
Large values in the IGAC solutions are unclear.
b) Mean RMS values of the station position residuals for each analysis centre with respect to the
IGS weekly final solutions. This comparison allows to assess the accuracy of the individual solutions: about ± 1.3 mm in the North and theEast, and ± 4 mm in the vertical component.
Large values in the vertical component presented
by the INEGI-MX, LUZ-VE and UNA-CR solutions are caused by Mexican stations processedby the IGS with a wrong antenna model. Large
residuals in the IGM-CL solutions are caused bya lack of IGS reference stations in the southernpart of the SIRGAS region.
c) Standard deviation of station positions after
solving the individual solutions with respect tothe IGS reference frame. These values represent the formal errors of the individual solutions.
Individual standard deviations agree quite well:± 1.51 mm (IGM-CL, IGAC-CO), ± 1.58 mm(DGFI-DE, IGM-EC, IBGE-BR, LUZ-VE, UNACR, SGM-UY), ± 2.0 mm (IGN-AR, INEGIMX).
d) Quality evaluation of the combined SIRGAS
solutions: The coordinate repeatability of theweekly combinations provides an estimate forthe accuracy (internal consistency) of the weekly
combinations of about ± 1.2 mm in the horizontal
component and about ± 3.2 mm in the verticalone. 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 ±1.5 mm in the horizontal position and ± 4.2 mm
in the height. The differences with respect to the
IBGE weekly combinations are at the expectedlevel (less than 0.5 mm).

Figure 3: Quality control of the individual solutions delivered by the SIRGAS processing centres
as well as of the combined solutions computed by the IGS RNAAC SIRGAS (meanvalues from 01-09-2015 to 10-10-2016, 58 weeks).

109

SIRGAS Associate Analysis Center
be considered as local, the effects of the Maule earthquake changed the surface kinematics
of a large area (between the latitudes 30◦ S - 45◦ S from the Pacific to the Atlantic coasts).
Before the Maule earthquake, the strain rate field in this area showed a strong west-east
compression with maximum rates of about 0.40 µstrain/a between latitudes 38◦ S and 44◦ S(Figure 6). In accordance, the deformation vectors were roughly parallel to the plate subduction direction and their magnitudes decreased with the distance from the subduction
front. After the earthquake, the largest compression (0.25 µstrain/a) occurs between thelatitudes 37◦ S and 40◦ S with a N30◦ E direction. The maximum extensional strain rate
(0.20 to 0.35 µstrain/a) is observed in the Sub-Andean zone in the Patagonia south oflatitude 40◦ S. The extensional axes rotate from a N30◦ E direction in the central Araucania
zone to a westerly direction of N72◦ W in the western part of Patagonia. In the northern
region of parallel 35◦ S, the extension is also directed to the Maule zone (S45◦ W) but withquite smaller rates (< 0.06 µstrain/a). This complex kinematics causes a large counterclockwise deformation pattern rotating around a point south of the epicentre (35.9◦ S,
72.7◦ W). The magnitude of the deformation vectors varies from 1 mm/a close to the rotation point up to 22 mm/a near the 2010 earthquake epicentre. The direction of thelargest deformation vectors points to the epicentre. VEMOS2015 covers the region from55◦ S, 110◦ W to 32◦ N, 35◦ W with a spatial resolution of 1◦ x 1◦ . The average prediction
uncertainty is ±0.6 mm/a in the north-south direction and ±1.2 mm/a in the east-west
direction. The maximum is ±9 mm/a in the Maule deformation zone while the minimum
values of about ±0.1 mm/a occur in the stable eastern part of the South American plate.

Station coordinates, station position time series as well as velocity and deformation fields
computed by the IGS RNAAC SIRGAS within the model VEMOS 2015 are available
through the PANGAEA (Data Publisher for Earth and Environmental Science) platform
at: https://doi.pangaea.de/10.1594/PANGAEA.835100 and https://doi.pangaea.de/
10.1594/PANGAEA.863131.

4 Acknowledgements
The operational infrastructure and results described in this report are only possible thanks
to the active support 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. We are also grateful to the IGS,UNAVCO, and the NGS for making available some of the invaluable GNSS data sets usedby the IGS RNAAC SIRGAS. More details about the activities and new challenges of
SIRGAS, as well as institutions and colleagues working on can be found at www.sirgas.
org.

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4 Acknowledgements

Figure 4: Kinematics of the SIRGAS reference frame. Station coordinates refer to the IGb08
frame, epoch 2013.0. Averaged RMS precision for the considered 456 stations is ±1.8mm for the station positions, and ±1.0 mm/a for the velocities (taken from (Sánchez
and Drewes 2016)).

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SIRGAS Associate Analysis Center

Figure 5: Velocity field VEMOS2015 (taken from (Sánchez and Drewes 2016)). AF: Africa,
AN: Antarctica, AP: Altiplano, CA: Caribbean, CO: Cocos, EA: Easter Island, GP:
Galapagos, JZ: Juan Fernandez, NA: North America, ND: North Andes, NZ: Nazca,
PA: Pacific, PM: Panama, RI: Rivera, SA: South America, SC: Scotia, GOV: Gonave,
HSP: Hispaniola, PRV: Puerto Rico and Virgin Islands, MAY: Maya, CHT: Chortis,
CGA: Chorotega, PRU: Peru, PSP: Puna-Sierras Pampeanas, MAU: El Maule, ARU:
Araucania, PTG: Patagonia.

112

References

Figure 6: Strain field after (2010 to 2015, left) and before (2000 to 2008, right) the Maule 2010
earthquake (taken from (Sánchez and Drewes 2016)). NZ: Nazca, SA: South America,
PSP: Puna-Sierras Pampeanas, MAU: El Maule, ARU: Araucania, PTG: Patagonia.

References
Brunini C., L. Sánchez., H. Drewes., S.M.A. Costa., V Mackern., W. Martínez.,
W. Seemüller., and A.L. DaSilva. Improved analysis strategy and accessibility of
the SIRGAS Reference Frame. IAG SYMPOSIA, 136:3–10, 2012. doi: 10.1007/9783-642-20338-1_1
Cioce V., S. Alves, M. Gende. Estado actual de la red SIRGAS-CON: Reporte del Grupode Trabajo I. Presented at the Symposium SIRGAS 2016, Quito, Ecuador, November
16-18, 2016a.
Cioce V., M.F. Rinc’on, E. Wildermann, G. Royero, R. Ceballos, and L. Sánchez. Actividades del Centro de Procesamiento y AnÃąlisis GNSS SIRGAS de la Universidad
del Zulia, Venezuela, periodo 2015-2016. Presented at the Symposium SIRGAS 2016,
Quito, Ecuador, November 16-18, 2016b.
Costa S.M.A., A.L. Silva, and J.A. Vaz. Processing evaluation of SIRGAS-CON network
by IBGE Analysis Center. Geodesy for Planet Earth, IAG Symposia, 136:859-868,
Springer Berlin Heidelberg, DOI: 10.1007/978-3-642-20338-1_108, 2012.
Dach R., S. Lutz, P. Walser, and P. Fridez (eds.). Bernese GNSS Software Version 5.2.
Astronomical Institute, University of Bern, 2015.
Herring T.A., R.W. King, and S.C. McClusky. Introduction to GAMIT/GLOBK, Release
10.4, Massachusetts Institue of Technology. Available at http://www-gpsg.mit.edu/~simon/gtgk/Intro_GG.pdf, 2010.
Moya J., D. Ovares, S. Bastos, and J.F. Valverde. Resultados del Centro Oficial deProcesamiento SIRGAS de Costa Rica, periodo 2016. Presented at the Symposium
SIRGAS 2016, Quito, Ecuador, November 16-18, 2016.

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SIRGAS Associate Analysis Center
Parra H.. Centro Oficial de Procesamiento SIRGAS IGM-Chile (IGM-CL). Presented at
the Symposium SIRGAS 2016, Quito, Ecuador, November 16-18, 2016.
Sánchez L. Recent activities of the IGS Regional Network Associate Analysis Centre for
SIRGAS (IGS RNAAC SIRGAS). Presented at the Symposium SIRGAS 2016, Quito,
Ecuador, November 16-18, 2016.
Sánchez L., W. Seemüller, and M. Seitz. Combination of the Weekly Solutions Deliveredby the SIRGAS Processing Centres for the SIRGAS–CON Reference Frame. IAG
Symposia, 136:845–851, 2012. doi: 10.1007/978-3-642-20338-1_106.
Sánchez L., W. Seemüller, H. Drewes, L. Mateo, G. González G., A. Silva, J. PampillónJ., 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. IAG Symposia 138: 153-161, DOI:10.1007/978-3642-32998-2_24, 2013
Sánchez, L., H. Drewes, C. Brunini, M.V. Mackern, and W. Martínez-Díaz. SIRGAS core
network stability. IAG Symposia 143, 2015a. doi: 10.1007/1345_2015_143.
Sánchez L., H. Drewes. Crustal deformation and surface kinematics after the 2010 earthquakes in Latin America. Journal of Geodynamics, 10.1016/j.jog.2016.06.005, 2016.
Suárez N. Centro Local de Procesamiento SIRGAS de Uruguay (SGM-UY) - Red
Geodésica Nacional Activa de Uruguay (REGNA-ROU) - Reporte de Actividades
2016. Presented at the Symposium SIRGAS 2016, Quito, Ecuador, November 16-18,
2016.

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Part III
Data Centers

115

Infrastructure Committee
Technical Report 2016
I. Romero
ESA/ESOC/Navigation Support Office, Darmstadt, Germany
E–mail: Ignacio.Romero@esa.int

1 Introduction
The IGS Infrastructure Committee (IC) is a permanent body established to ensure thatthe data requirements for the highest quality GNSS products are fully satisfied while also
anticipating future needs and evolving circumstances. Its principal objective is to assurethat the IGS infrastructure components that collect and distribute the IGS tracking dataand information are sustained to meet the needs of principal users, in particular the IGS
analysis centers, fundamental product coordinators, pilot projects, and working groups.
The IC fulfills this objective by coordinating and overseeing facets of the IGS organization
involved in the collection and distribution of GNSS observational data and information,
including network stations and their configurations (instrumentation, monumentation,communications, etc), and data flow.
The IC establishes policies and guidelines, where appropriate, working in close collaboration with all IGS components, as well as with the various agencies that operate GNSS
tracking networks. The IC interacts with International Association of Geodesy (IAG)
sister services and projects – including the International Earth Rotation and Reference
Systems Service (IERS) and the Global Geodetic Observing System (GGOS) – and withother external groups (such as the RTCM) to synchronize with the global, multi–techniquegeodetic infrastructure.
Current Members: appointed Dec, 2015 for terms up to Dec 2017;• Carine Bruyninx (ROB)• Lou Estey (UNAVCO)• Nicholas Brown (GA)• Nacho Romero – Chairman – (ESOC)
117

Infrastructure Committee• Brian Donahue (NRCan)• Wolfgang Soehne (BKG)
Ex–officio Members:• Steve Fisher – Central Bureau• David Maggert – Network Coordinator• Michael Moore – Analysis Coordinator• Tom Herring – Analysis Coordinator• Axel Ruelke – Real time Working Group Chair• Bruno Garayt – Reference Frame Coordinator• Carey Noll – Data Center Working Group Chair• Michael Coleman – Clock Products Coordinator

2 Summary of Activities in 2016
Over 2016 the IC has supported the Network Coordinator on answering questions from
IGS product and data users, plus helping with contacts and new station additions in
Taiwan, China, Malaysia, Thailand, etc. This has also included making sure the regionalreference frame organizations such as APREF, etc are including as many of their own
region’s stations in their station position solutions as possible. The IC has participated in
the improvements to the IGS website network pages in terms of map selectors, dormant
station indicators, etc.
In terms of the very important RINEX 3 data file integration into the IGS the switch
to long name data files has been completed over 2016 with 96.7% of RINEX3 files now
submitting data files using the correct long names. The IC created a new utility to generate
the data file longnames ’RX3name’ to assist all station operators from all major networks
to generate the correct longnames based on the existing short names they may be using;
http://acc.igs.org/software/RINEX3_longname.pdf
The usage of new station long names has been discussed with all product generating
working groups for inclusion in the IGS products; clock files, SINEX station position files
and Tropo SINEX format. The adoption of the new formats should take place during 2017
after a long consultation period with analysis centers and product users.

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3 Activities in 2017

3 Activities in 2017
During 2017 the IC will be concentrating on the following issues;• RINEX 3 station name product inclusion• Including the TIGA related infrastructure needs as part of the IGS network considerations.
• Improve the usage of the IGS network stations and the reporting back to station
operators of how their stations are doing• Continued contacts and investigation on the establishments of an IGS–wide NBS
repository

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Infrastructure Committee

120

CDDIS Global Data Center
Technical Report 2016
C. NollNASA Goddard Space Flight Center, Code 61A
Greenbelt, MD 20771 USA
Carey.Noll@nasa.gov

1 Introduction
The Crustal Dynamics Data Information System (CDDIS) is NASA’s data archive andinformation service supporting the international space geodesy community. For over 35
years, the CDDIS has provided continuous, long term, public access to the data (mainly
GNSS-Global Navigation Satellite System, SLR-Satellite Laser Ranging, VLBI-Very Long
Baseline Interferometry, and DORIS-Doppler Orbitography and Radiopositioning Integrated by Satellite) and products derived from these data required for a variety of science observations, including the determination of a global terrestrial reference frame andgeodetic studies in plate tectonics, earthquake displacements, volcano monitoring, Earthorientation, 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 Active Archive Centers (DAACs); EOSDIS data centersserve a diverse user community and are tasked to provide facilities to search and accessscience data and products. The CDDIS is also a regular member of the International
Council for Science (ICSU) World Data System (WDS).
The CDDIS serves as one of the primary data centers and core components for the geometric services established under the International Association of Geodesy (IAG), an organization that promotes scientific cooperation and research in geodesy on a global scale.
The system has supported the International GNSS Service (IGS) as a global data center
since 1992. The CDDIS activities within the IGS during 2016 are summarized below; thisreport also includes any recent changes or enhancements made to the CDDIS.

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2 System Description
2.1 Computer Infrastructure
The CDDIS archive of IGS data and products are accessible worldwide through anonymous ftp (ftp://cddis.nasa.gov). The CDDIS has also implemented web-based accessto the archive (https://cddis.nasa.gov/archive). The CDDIS is located at NASA’s
Goddard Space Flight Center (GSFC) and is available to users 24 hours per day, sevendays per week. The CDDIS computer facility is fully redundant with primary and secondary/failover systems. Until December 2016, the CDDIS server configuration consistedof multiple incoming and outgoing servers dedicated to specific functions and was equippedwith 32 Tbytes of online storage. Throughout early 2016, a new virtual machine (VM)
based system configured with 100 Tbytes of unified storage was tested within the EOSDIS
computer facility and network infrastructure. The new CDDIS computer system, shownin Figure 2.1, became operational on December 01, 2016. This new system configuration
provides a more reliable/redundant environment (power, HVAC, 24-hour on-site emergency personnel, etc.) and network connectivity; a disaster recovery system is installed
in a different location on the GSFC campus for rapid failover when required. The new
system location addresses a key operational issue CDDIS has experienced over the past
several years: the lack of consistent and redundant power and cooling in its computer
facility. Furthermore, multiple, redundant 40G network switches are available to takefull advantage of a high-performance network infrastructure by utilizing fully redundantnetwork paths for all outgoing and incoming files along with dedicated 10G network connections between its primary operations and its backup operations. The use of the virtual
machine technology provides multiple instance services for a load balancing configuration
and allows for VM instances to be increased or decreased due to demand. Furthermore,
the VM technology allows for system maintenance (patching, upgrades, etc.) to proceedwithout any downtime or interruption to user access. The large, unified storage system
will easily accommodate future growth of the archive and facilitate near real-time replication between its production and disaster recovery sites. The entire archive is also mirrored
to traditional storage arrays for additional complete copies of the archive.

2.2 Web Applications
The CDDIS maintains two applications for querying site information or archive contents. The Site Log Viewer (https://cddis.nasa.gov/Data_and_Derived_Products/\discretionary{-}{}{}SiteLogViewer/index.html) is an application for the enhanced
display and comparison of the contents IAG service site logs; currently the IGS, ILRS,
and IDS site logs are viewable through this application. Through the Site Log Viewer
application, users can display a complete site log, section by section, display contentsof one section for all site logs, and search the contents of one section of a site log fora specified parameter value. Thus, users can survey the entire collection of site logs for122

3 Archive Contents

Figure 1: System architecture overview diagram for the new CDDIS facility installation within
the EOSDIS infrastructure.

systems having particular equipment or characteristics. Access to IVS/VLBI site logs will
be provided in a future release of the application.
A second application, the CDDIS Archive Explorer accessible at https://cddis.nasa.
gov/Data_and_Derived_Products/CddisArchiveExplorer.html allows users to discoverwhat data are available through the CDDIS. The application provides users, particularly
those new to the CDDIS, the ability to specify search criteria based on temporal, spatial, target, site designation, and/or observation parameter in order to identify data andproducts of interest for download. Results of these queries include a listing of sites andadditional metadata satisfying the user input specifications. Such a user interface also aids
CDDIS staff in managing the contents of the archive. Future plans for the application
include adding a list of data holdings/URLs satisfying the search criteria.

3 Archive Contents
As a global data center for the IGS, the CDDIS is responsible for archiving and providing
access to GNSS data from the global IGS network as well as the products derived fromthe analyses of these data in support of both operational and working group/pilot project
activities. The CDDIS archive is approximately 17.5 Tbytes in size (over 190 million files)of which 16.5 Tbytes (95%) is devoted to GNSS data (15.4 Tbytes), products (1.1 Tbytes),
and ancillary information. All data and products are accessible through subdirectories of
ftp://cddis.nasa.gov/gnss.
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CDDIS Data Center
Table 1: GNSS Data Type Summary.
Data Type

SampleRate

Data Format

Available

Daily GNSS
Daily GNSS
Hourly GNSS
Hourly GNSS
High-rate GNSS
High-rate GNSS
Satellite GPS

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

RINEX V2RINEX V3
RINEX V2RINEX V3
RINEX V2RINEX V3
RINEX V2

Since 1992
Since 2016
12+ years
Since 2016
Since 2001
Since 2016
2002-2012

Table 2: GNSS Data Archive Summary for 2016.
Data Type

Avg. No.
Sites/Day

No. Unique
Sites

Avg.
Volume/Day

Total
Volume/Year

No.
Files

Directory Location

Daily GNSS (V2 filename)Daily GNSS (V3 filename)
Hourly GNSS (V2 filename)
Hourly GNSS (V3 filename)High-rate GNSS (V2 filename)High-rate GNSS (V3 filename)High-rate GNSS (V3 filename)

495
210
385
119
335
36
36

545
111
344
55
204
22
22

1,570 MB215 MB
680 MB
160 MB
4,110 MB935 MB
935 MB

580 GB
80 GB
250 GB
60 GB
1,500 GB
345 GB
345 GB

828K
121K
7,455K
1,627K
12,518K
891K
891K/gnss/data/daily/gnss/data/daily/gnss/data/hourly/gnss/data/hourly/gnss/data/highrate/gnss/data/highrate/gnss/data/highrate

3.1 GNSS Data
3.1.1 Main Data Archive
The user community has access to GNSS data available through the on-line global data
center archives of the IGS. Over 70 operational and regional IGS data centers and station
operators make data (observation, navigation, and meteorological) available in RINEX
format to the CDDIS from receivers on a daily, hourly, and sub-hourly basis. The CDDIS
also accesses the archives of other 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.
Table 3.1.1 and 3.1.1 below summarizes the types of IGS GNSS data sets available in the
CDDIS in the operational, non-campaign directories of the GNSS archive.
Data, in RINEX V2.10 or V2.11 format, from GPS and GPS+GLONASS receivers arearchived within the main GNSS directory structure /gnss/data. Since January 2016,
RINEX V3 data, using the V3 filename specification, are archived with the RINEX V2
data (see Section 3.1.2 for more information).
The CDDIS archives three major types/formats of GNSS data, daily, hourly, and high-rate
sub-hourly, all in RINEX format, as described in Table 1a; the network distribution ofsubmitted files is shown in Figure 2. Daily RINEX data are quality-checked, summarized(using UNAVCO’s teqc software), and archived to public disk areas in subdirectories byyear, day, and file type; the summary and inventory information are also loaded into an
on-line database. Over 177K daily station days from 545 distinct GNSS receivers were124

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Figure 2: CDDIS GNSS archive includes data in daily (red), hourly (yellow), sub-hourly (blue),
and/or real-time (orange) increments. Hourly, sub-hourly, and real-time data allow
analysts to generate products for applications needing more frequent updates.

archived at the CDDIS during 2016; 209 RINEX V3 sites (including 46 RINEX V3-only)
supplied RINEX V3 data. A complete list of daily, hourly, and high-rate sites archived
in the CDDIS can be found in the yearly summary reports at URL ftp://cddis.nasa.
gov/reports/gnss/.
Within minutes of receipt, the hourly GNSS files are archived to subdirectories by year,
day, and hour. Although these data are retained on-line, the daily files delivered at theend of the UTC day contain all data from these hourly files and thus can be used in lieu of
the individual hourly files. A total of 385 unique hourly sites (over 7.4 million files) werearchived during 2016; 119 hourly sites provided data in RINEX V3 format (12 RINEX
V3-only).
High-rate (one-second sampling rate) GNSS data are made available in files containing
fifteen minutes of data and in subdirectories by year, day, file type, and hour. Many ofthese data files are created from real-time streams. Data from 335 unique high-rate sites(over 12 million files) were archived in the CDDIS in 2016; 36 high-rate sites provided
data in RINEX V3 format (20 RINEX V3-only).
The CDDIS generates global broadcast ephemeris files (for both GPS and GLONASS) ona daily and hourly basis. The hourly concatenated broadcast ephemeris files are derived
from the site-specific ephemeris data files for each hour and are appended to a single
file that contains the orbit information for all GPS and GLONASS satellites for the day
up through that hour. The merged ephemeris data files, named hourDDD0.YYn.Z, are125CDDIS Data Center
Table 3: GNSS MGEX Data Archive Summary for 2016.
Data Type

Avg. No.
Sites/Day

No. Unique
Sites

Avg.
Volume/Day

Total
Volume/Year

No.
Files

Directory Location

Daily GNSS
Hourly GNSS
High-rate GNSS

111
55
22

210
120
36

121K
1,630K
890K

375 MB80 MB
2,300 MB136 GB
29 GB
740 GB/gnss/data/campaign/mgex/daily/gnss/campaign/mgex/data/hourly/gnss/campaign/mgex/data/highratethen copied to the day’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 havebeen submitted, this concatenation procedure is repeated to create the daily broadcast
ephemeris files (both GPS and GLONASS), using daily site-specific navigation files as
input. These daily broadcast files, named brdcDDD0.YYn.Z and brdcDDD0.YYg.Z, arethen copied to the corresponding subdirectory under the daily file system. Users can thus
download this single, daily (or hourly) file to obtain the unique navigation messages rather
than downloading multiple broadcast ephemeris files from the individual stations.
The CDDIS generates and updates ”status” files, (/gnss/data/daily/YYYY/DDD/
YYDDD.status for RINEX V2 data and YYDDD.V3status for RINEX V3 data) thatsummarize the holdings of daily GNSS data. The archive status files of CDDIS GNSS
data holdings reflect timeliness of the data delivered as well as statistics on number ofdata points, cycle slips, and multipath (for RINEX V2 data). The user community canthus view a snapshot of data availability and quality by checking the contents of such asummary file.
Colleagues at TUM and DLR are also providing GPS and QZSS CNAV (civilian navigation) data on an operational basis within MGEX. These messages are collected from a
sub-network of MGEX stations and are provided in a merged daily file in a format similar to
RINEX. These files are named brdxDDD0.YYx.Z and stored in a daily subdirectory within
the MGEX archive at CDDIS (/gnss/data/campaign/mgex/daily/rinex3/YYYY/cnav ).
3.1.2 IGS Products
The CDDIS worked with the IGS Infrastructure Committee (IC) to integrate data in
RINEX V3 format into the operational, main archives at the IGS Global Data Centers.
The resulting ”RINEX V3 Transition Plan” addressed a key recommendation from the
IGS 2014 Workshop: ”one network one archive” and provided for the better integrationof multi-GNSS data into the entire IGS infrastructure. Starting in 2015, stations began
submitting RINEX V3 data using the format’s ”long” filename specification. The transition
plan specified that RINEX V3 data from IGS network sites using the V3 filename structure
should be archived in the same directory structure as the operational RINEX V2 data.
Therefore, starting on January 01, 2016, all daily, hourly, and high-rate data submitted to
the CDDIS in RINEX V3 format and using the long, V3 filename specification have beenarchived in the same directories as the RINEX V2 data (which use the 8.3.Z filename for126

3 Archive Contents

Figure 3: The main, operational archive at CDDIS now includes data in RINEX V2 format using
the 8.3.Z filename specification (red) and RINEX V3 format using the V3 filename
specification (yellow).

daily and hourly files and the 10.3.Z filename format for high-rate files). In addition, these
RINEX V3 files are compressed in gzip (.gz) format; files in RINEX V2 format continue
to use UNIX compression (.Z). Figure 3 shows the network of IGS sites providing daily
data in RINEX V2 and/or V3 formats.
3.1.3 RINEX V3 (MGEX) Archive
During 2016, the CDDIS continued the archiving of data in RINEX V3 format from multiGNSS receivers participating in the Multi-GNSS Experiment (MGEX) as well as products
derived from the analysis of these data. The data include all available multi-GNSS signals(e.g., Galileo, QZSS, SBAS, BeiDou, and IRNSS) in addition to GPS and GLONASS.
These data, in RINEX V3 format but using the 8.3.Z filename specification, continue tobe archived in a campaign directory structure at CDDIS (/gnss/campaign/mgex/data).
The summary of the MGEX data holdings at the CDDIS is shown in Table 3.1.1 below.
Daily status files are also provided that summarize the MGEX data holdings; however,data quality information, generated for data holdings in RINEX V2 format, is not available
through the software used by CDDIS to summarize data in RINEX V3 format. CDDIS
continues to investigate and evaluate software capable of providing data summary/QC
information for RINEX V3 data. As station operators converted RINEX V3 data to thelong, RINEX V3 filename specification (see Section 3.1.2), the amount of data archived
in the campaign directories has decreased.

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CDDIS Data Center
Table 4: GNSS Product Summary for 2016.
Product Type

Number of ACs/AACs

VolumeDirectory

Orbits, clocks, ERP,
positionsTroposphere
Ionosphere
Real-time
Repro214+Combinations

1.4 GB/week

Combination
6+Combination
Combinations
10+Combinations

3 MB/day, 1.1 GB/year
4 MB/day, 1.5 GB/year
28 MB/week
850 MB/week/gnss/products/WWWW (GPS, GPS+GLONASS)/glonass/products/WWWW (GLONASS only)/gnss/products/troposphere/YYYY/gnss/products/ionosphere/YYYY/gnss/products/rtpp/YYYY/gnss/products/WWWW/repro2

Note: WWWW=4-digit GPS week number; YYYY=4-digit year

The CDDIS also added a merged, multi-GNSS broadcast ephemeris file containing GPS,GLONASS, Galileo, BeiDou, QZSS, and SBAS ephemerides from MGEX stations. Thisfile, generate by colleagues at the Technical University in Munich (TUM) and Deutsches
Zentrum fÂĺur Luft- und Raumfahrt (DLR), is similar to the daily and hourly concatenatedbroadcast message files in RINEX V2 format provided by the CDDIS for the operational
GPS+GLONASS data sets; it contains all the unique broadcast navigation messages forthe day. The file, named brdmDDD0.YYp.Z, is stored in daily subdirectories within the
MGEX campaign archive at CDDIS (/gnss/data/campaign/mgex/daily/rinex3/YYYY/
DDD/YYp) and in a yearly top level subdirectory (/gnss/data/campaign/mgex/daily/
rinex3/YYYY/brdm).

3.2 IGS Products
The CDDIS routinely archives IGS operational products (daily, rapid, and ultra-rapid orbits and clocks, ERP, and station positions) as well as products generated by IGS working
groups and pilot projects (ionosphere, troposphere, real-time). Table 3.2 below summarizes the GNSS products available through the CDDIS. The CDDIS currently provides
on-line access through anonymous ftp to all IGS products generated since the start of
the IGS Test Campaign in June 1992 in the file system /gnss/products; products from
GPS+GLONASS products are available through this filesystem. Products derived fromGLONASS data only continue to be archived at the CDDIS in a directory structure within
the file system /glonass/products.
The CDDIS also continues to archive combined troposphere estimates in directories by
year and day of year. Global ionosphere maps of total electron content (TEC) from the
IONEX AACs are also archived in subdirectories by year and day of year. Real-time clock
comparison products have been archived at the CDDIS in support of the IGS Real-Time
Pilot Project, and current IGS Real-Time Service, since 2009.
In 2015, the IGS analysis centers completed the upload of products for the second IGS
reprocessing campaign (repro2). The CDDIS provided support through upload of files
from the ACs and online archive of these products (/gnss/products/WWWW/repro2 );additional files were submitted in 2016. Six AACs (CODE, GFZ, GRGS, JAXA, TUM,
and Wuhan) generated weekly products (orbits, ERP, clocks, and others) in support of128

3 Archive Contents
MGEX. These files are archived at the CDDIS in the MGEX campaign subdirectory by
GPS week (/gnss/products/mgex/WWWW ).
Colleagues at DLR and the Chinese Academy of Sciences (CAS) provide a differential
code biase (DCB) products for the MGEX campaign. This product is derived from GPS,GLONASS, Galileo, and BeiDou ionosphere-corrected pseudorange differences and is available in the bias SINEX format. DLR has provided two files per year, daily satellite anddaily satellite and station biases since 2013 in CDDIS directory /gnss/products/mgex/dcb;
CAS provides daily files. Additional details on the DCB product are available in IGSMailmessage 6868 sent in February 2015 and message 7173 sent in October 2015. Both products
use the new RINEX V3 file naming convention.

3.3 Real-Time Activities
In 2013, the CDDIS staff configured a server and began testing a caster to provide a realtime streaming capability at GSFC and support the IGS Real-Time Service (IGS RTS).
The CDDIS successfully tested obtaining product streams from the BKG and IGS casters
and providing access to these streams to authorized users; additional streams from Natural
Resources Canada (NRCan) and Geoscience Australia (GA) were later added to the caster.
Work was completed in spring 2015 and the CDDIS caster became fully operational,
broadcasting nearly 40 product and 165+ data streams in real-time. The caster runs the
NTRIP (Network Transport of RTCM via internet Protocol) format. Figure 4 shows the
distribution of stations providing real-time streams to the CDDIS caster.
As stated previously, the CDDIS is one of NASA’s EOSDIS DAACs and through EOSDIS, has access to a world-class user registration process, the EOSDIS Earthdata Login(EDL, formerly User Registration System, URS), with over 255K users in its system.
Since the NTRIP-native registration/access software was not compatible with NASA policies, the CDDIS developed software to interface the caster and the EDL within a genericLightweight Directory Access Protocol (LDAP) framework. The module was specificallydeveloped to easily interface with multiple user verification systems and was given backto the NTRIP community for possible inclusion in future releases. New users complete a
registration form available on the CDDIS website; once completed, the data are passed to
the EDL, which generates an email to the user with a validation link. The user accesses
the link and the EDL validates the form’s data; this process is accomplished within aminute or less. The user’s validated access request is submitted to CDDIS staff for accessauthorization to the CDDIS caster. This second step is not yet automated and can takeseveral hours to configure depending on the time of day. In addition, users registeringin this system have access to the entire suite of EOSDIS products across all 12 EOSDISDAACs.
Initially, the CDDIS caster provided access to data and product streams from several
regional real-time casters. Data streams have also been provided through JPL for receivers

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CDDIS Data Center

Figure 4: CDDIS is operationally supporting the dissemination of data from over 225 real-time
GNSS sites as well as near real-time products derived from these data.

in NASA’s Global GPS Network. In 2016, an additional set of stations from JPL’s Global
Differential GPS (GDGPS) network were added to the CDDIS caster. This networkof globally distributed, geodetic quality, dual frequency receivers, provides additional 1
Hz data streams to those current available from the IGS RTS. The CDDIS caster wasaugmented with new real-time streams as they became available from IGS network sites.
The CDDIS caster serves as the third primary caster for the IGS RTS, thus providing
a more robust topology with redundancy and increased reliability for the service. User
registration, however, for all three casters is unique; therefore, current users of the casters
located at the IGS and BKG are required to register through the CDDIS registration
process in order to use the CDDIS caster. By the end of 2016, over 100 users from 28
countries have registered to use the CDDIS caster. More information about the CDDIS
caster is available at https://cddis-casterreg.gsfc.nasa.gov/index.html.
The CDDIS has also developed software to capture real-time data streams into fifteenminute high-rate files. This capability requires further testing and coordination with the
IGS Central Bureau and Infrastructure Committee before it is put into operational use.

3.4 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 for RINEX V2 data; status files, with limited information, summarizing130

5 Recent Developments
RINEX V3 data holdings are also available. By accessing these files, the user community
can receive a quick look at a day’s data availability and quality by viewing a single file.
The daily status files are available through the web at URL ftp://cddis.nasa.gov/
reports/gnss/status. The daily status files are also archived in the daily GNSS data
directories.
In preparation for the analysis center’s reprocessing campaigns, the CDDIS developed sitespecific reports detailing missing data. Station operators and operational data centers canconsult these lists (ftp://cddis.nasa.gov/gnss/data/daily/reports/missing) and if
available, supply missing files to the CDDIS for inclusion in the global data center archives.
Ancillary information to aid in the use of GNSS data and products are also accessible
through the CDDIS. Daily, weekly, and yearly summaries of IGS tracking data (daily,
hourly, and high-rate) archived at the CDDIS are generated on a routine basis. Thesesummaries are accessible through the web at URL ftp://cddis.nasa.gov/reports/gnss.
The CDDIS also maintains an archive of and indices to IGS Mail, Report, Station, andother IGS-related messages.

4 System Usage
Figure 5 summarizes the usage of the CDDIS for the retrieval of GNSS data and products
in 2016. This figure illustrates the number and volume of GNSS files retrieved by the user
community during 2016, categorized by type (daily, hourly, high-rate, products). Nearly
930 million files (nearly 140 Tbytes) were transferred in 2016, with an average of nearly 80
million files per month. Figure 6 illustrates the profile of users accessing the CDDIS IGS
archive during 2016. The majority of CDDIS users were once again from hosts in North
America, Asia, and Europe.

5 Recent Developments
5.1 Next Generation Hardware
As detailed in the system hardware section above, the CDDIS transferred operations to the
new virtual-machine based architecture on December 01, 2016. The transition to the new
system was accomplished with less than 30 hours of downtime to the user community.

5.2 Archive Operations
The CDDIS has been operating for over 30 years. During that time procedures and processes have grown to meet both existing data archive needs and new requirements, which

131

CDDIS Data Center

Figure 5: Number and volume of GNSS files transferred from the CDDIS in 2016.

Figure 6: Geographic distribution of IGS
users of the CDDIS in 2016.

over time had become unwieldy and hard to support. Therefore, CDDIS conducted acomplete review of the entire data ingest operations system in early 2016 to identify andcorrect process inefficiencies in and improve the QC of incoming files. Software development included the addition of more automation capabilities, better redundancy, easiersupportability, and common code sharing. The staff developed and integrated new software to perform routine checksums of and anti-virus scanning on all incoming files. The
new operations software was implemented for GNSS data processing prior to the transition
to the new hardware system and is now fully operational on this new system. Testing onother data types (e.g., SLR and DORIS) will start in early 2017.

5.3 Archive Operations
CDDIS has traditionally used ftp (with a username/password) for delivery of files fromthe data and product suppliers. The underlying user accounts to receive these contributions had limited privileges, allowing data and product providers to deposit files but not
retrieve files from these disk areas. However, with the installation of the CDDIS servers
within the new computer facility, the CDDIS needed to move to a better-supported protocol and at the same time use a single sign-on system to perform authentication. The
CDDIS staff developed an https-based protocol method for delivery of files from suppliersof data and products. The authentication is performed through the EOSDIS Earthdata
Login (EDL) system, the same system used for access to the CDDIS real-time caster. The
file uploads can be performed through a webpage interface or a command line applicationthat can perform an http ”post” operation, which is more commonly used for scripting.
This process allows data suppliers to authenticate through the EDL system and provide
their files through https to CDDIS for ingest into the archive. For several months, sup-132

6 Publications
pliers performed significant testing on the new upload system. By late summer, all dataand product suppliers were contacted and full testing began. This new delivery method
was fully implemented for all suppliers as the CDDIS transitioned operations to the newservers. Unfortunately, some data providers have had difficulty adapting their software to
use the new CDDIS upload system which has affected CDDIS data holdings. The CDDIS
staff continues to work with these providers to help answer any questions during their transition to the new system. More information on the CDDIS file upload system is available
at: https://cddis.nasa.gov/About/CDDIS_File_Upload_Documentation.html.

5.4 Metadata Developments
The CDDIS continues to make modifications to the metadata extracted from incoming
data and product files pushed to its archive and implemented these changes in the new
operations software system. These enhancements have facilitated cross discipline data
discovery by providing information about CDDIS archive holdings to other data portals
such as Earth Observing System search client and future integration into the GGOS
portal. The staff continues work on a metadata evolution effort, re-designing the metadata
extracted from incoming data and adding information that will better support EOSDIS
applications such as its search client and the metrics collection effort. The CDDIS is also
participating in GGOS metadata efforts within the Bureau of Networks and Observations.
The CDDIS continues to implement Digital Object Identifiers (DOIs) to select IGS data
sets (GNSS data and products). DOIs can provide easier access to CDDIS data holdings
and allow researchers to cite these data holdings in publications. Landing pages areavailable for each of the DOIs created for CDDIS data products and linked to description
pages on the CDDIS website; an example of a typical DOI description (or landing) page,for daily Hatanaka-compressed GNSS data files, can be viewed at: https:/cddis.nasa.
gov/Data_and_Derived_Products/GNSS/daily_gnss_d.html. DOIs will be assigned toadditional GNSS data and product sets in the near future.

6 Publications
The CDDIS staff attended several conferences during 2016 and presented papers on or
conducted demos of their activities within the IGS, including:Noll C. , and P. Michael. ”Developments at CDDIS to Support Real-Time and RINEX
V3” (poster), presented at IGS Workshop ”GNSS Futures”, Sydney, NSW, Australia,
February 08–12, 2016
Michael P. , and C. Noll. ”Important Upcoming Architecture and User Changes at the
CDDIS” (poster),

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CDDIS Data Center
Michael P. , and C. Noll. ”Important Upcoming Architecture and User Changes at the
CDDIS” (poster), IGS Workshop ”GNSS Futures”, Sydney, NSW, Australia, February 08–12, 2016
Pearlman M. , E. Pavlis, C. Ma, C. Noll, D. Thaller, B. Richter, R. Gross, R. Neilan,
M. Mueller, R. Barzaghi, S. Bergstrand, J. Saunie, and M. Tamisiea ”Update on the
Activities of the GGOS Bureau of Networks and Observations” (poster), presented
at European Geosciences Union General Assembly, April, 2016, Abstract No. 10095
Noll C. ”GGOS: Global Geodetic Observing System”, presented at 2016 WDS Members’
Forum, Denver, Colorado, September 11, 2016
Stangl G. , and C. Noll. ”GGOS: The Global Geodetic Observing System” (poster), presented at 2016 WDS Members’ Forum, Denver, Colorado, September 11, 2016
Noll C. , and P. Michael. ”CDDIS: NASA’s Archive of Space Geodesy Data and Products
Supporting GGOS” (poster), presented at the Fall American Geophysical Union
meeting, San Francisco, CA, USA, December 06-12, 2016
Michael P. , C. Noll, and J. Woo, and R. Limbacher. ”Next Generation Global Navigation
Satellite System (GNSS) Processing at NASA CDDIS” (poster), presented at the Fall
American Geophysical Union meeting, San Francisco, CA, USA, December 06-12,
2016
Electronic versions of these and other publications can be accessed through the CDDIS
on-line documentation page on the web at URL https:/cddis.nasa.gov/Publications/
Presentations.html.

7 Future Plans
7.1 RINEX V3 Data
The CDDIS will continue to coordinate with the Infrastructure Committee, the Data Center Working Group, and other IGS data centers to implement steps outlined in the RINEX
V3 transition plan to complete the incorporation of RINEX V3 data into the operational
GNSS data directory structure. The CDDIS began this process with multi-GNSS, RINEX
V3 data from January 2016 onwards; the CDDIS will continue these efforts by integrating
RINEX V3 multi-GNSS data from years prior to 2016 into the IGS operational archives.
MGEX campaign directories will continue to be maintained during this transition to theoperational directory archive. Furthermore, the CDDIS staff will continue to test software to copy RINEX V3 data (using the older filename format) into files with RINEX
V3 filenames as well as QC RINEX V3 data and files and incorporate the software into
operational procedures.

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7 Future Plans

7.2 Real-Time Activities
The CDDIS will continue to add real-time data and product streams to its operational
caster in support of the IGS Real-Time Service. Future activities in the real-time area
include capturing the streams for generation of 15-minute high-rate files for archive. This
capability requires further testing and coordination with the IC. The staff is also developing
software to provide metrics on usage of the CDDIS caster. The staff will also investigate
automating the process of adding users to the CDDIS caster configuration files.

7.3 Web-Based User AccessWith EOSDIS requesting that EDL should be used for all data delivery to users, CDDIS isinvestigating possible methods of providing a web-based capability. Over 95% of CDDIS
users retrieve files using automated scripts; these scripts will not work with a web-based
approach as http does not support globbing. The EOSDIS EDL group has recently developed an Apache-based module to emulate ftp globbing functionality. This module iscurrently in testing with both CDDIS and EOSDIS. This new module will make the transition between ftp and http easier and CDDIS is investigating implementing EDL within
an https download option. CDDIS staff will continue to study possible solutions and best
methods for allowing users to retrieve data through https while still maintaining the ability
to use scripts. During this development, CDDIS staff will incorporate the lessons learned
from their data upload system into the https access capability.

7.4 Contact Information
To obtain more information about the CDDIS IGS archive of data and products, contact:
Ms. Carey E. Noll
Phone: (301) 614-6542
Manager, CDDISFax:(301) 614-6015
Code 61A
E-mail: Carey.Noll@nasa.gov
NASA GSFC
WWW: http://cddis.nasa.gov
Greenbelt, MD 20771

7.5 Acknowledgments
Funding for the CDDIS, and its support of the IAG, IGS and other services, is provided byNASA through the Earth Science Data and Information System (ESDIS) project, which
manages the EOSDIS science systems and DAACs.
The author would like to thank the CDDIS deputy manager, Patrick Michael, the CDDIS contractor staff, Maurice Dube, Nathan Pollack, Rebecca Limbacher, and Sandra
Blevins (Science Systems and Applications, Inc./SSAI), Lori Tyahla (Stinger Ghaffarian135

CDDIS Data Center
Technologies/SGT), Justine Woo (Sigma Space Inc.) and James Roark and Jennifer Ash(ADNET Systems). The success of the CDDIS and its recognition in the many international programs supported by the system 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, Volume 45, Issue 12, 15June 2010, Pages 1421-1440, ISSN 0273-1177, DOI: 10.1016/j.asr.2010.01.018.
Noll, C., and Bock, Y., Habrich, H., and Moore, A. Development of data infrastructure
to support scientific analysis for the International GNSS Service Journal of Geodesy,
Feb 2009, pages 309-325, DOI 10.1007/s00190-008-0245-6.
”IGS RINEX 3 Transition Plan v3.0” IGS website, http://kb.igs.org/hc/en-us/
article_attachments/202584007/Rinex_3_transition_plan_v3.0.pdf.
”The Receiver Independent Exchange Format. Version 3.03”, IGS website, ftp://igs.
org/pub/data/format/rinex303.pdf.

136

Part IV
Working Groups, Pilot Projects

137Antenna Working Group
Technical Report 2016
R. Schmid
Deutsches Geodätisches Forschungsinstitut
der Technischen Universität München (DGFI-TUM)
Arcisstr. 21, 80333 München, Germany
E-mail: schmid@tum.de

1 Generation of the absolute phase center model igs14.atx
On 29 January 2017 (GPS week 1934), the IGS switched to an IGS-specific realization of
the ITRF2014, called IGS14, that is consistent with an updated set of satellite and receiverantenna phase center corrections called igs14.atx. Details can be found in Rebischunget al. (2016). An update of the GPS and GLONASS satellite antenna z-offsets became
necessary due to recent orbit modeling changes affecting the scale of the IGS products(Earth radiation pressure, antenna thrust). Besides, existing receiver antenna calibrations
had not been updated since the release of igs08.atx in 2011.
Major changes of igs14.atx with respect to igs08.atx:• satellite antenna z-offsets from igs14.atx are consistent with IGS14, whereas thosefrom igs08.atx were consistent with IGb08• slightly improved redundancy of satellite antenna z-offsets: GPS values contained in
igs14.atx are based on repro2/operational results of 7 ACs (igs08.atx: 5), GLONASS
values still on those of only 2• as GLONASS satellite antenna z-offsets were contained in the SINEX files of twoACs, GLONASS and GPS values could, for the first time, be derived from the same
set of solutions• preliminary block-specific z-offsets for satellites launched since the latest z-offset
update in September 2012 were replaced by satellite-specific estimates• z-offsets trend-corrected to epoch 2010.0 due to a difference of about 0.03 ppb/yr
between the “intrinsic GNSS scale rate” (determined by the use of constant satellite
antenna z-offsets) and the ITRF2014 scale rate (Rebischung and Schmid 2016)139

Antenna Working Group• satellite-specific x- and y-offsets from pre-flight calibrations for the Block IIR satellites (Dilssner et al. 2016)• additional and updated robot-based receiver antenna calibrations• conversion of relative receiver antenna corrections with updated AOAD/M_ T values

2 Updates and content of the antenna phase center model
Table 1 lists 21 updates of the absolute IGS antenna phase center model igs08_wwww.atx(Schmid et al. 2016) that were released in 2016. 16 of them are related to changes ofthe satellite constellation, and five times an update of the model was released, when newreceiver antenna calibrations became available. Further details on all model changes canbe found in the corresponding IGSMAILs whose numbers are also given in Table 1.
Table 2 gives an overview of the data sets contained in the IGS phase center model. The
numbers refer to igs08_ 1928.atx/igs14_ 1928.atx released in December 2016. For GPS
and GLONASS, there are 94 and 101 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. In February 2016 (week 1885), two GLONASS
satellites (R854, R855) were renamed according to a recommendation made at the IGS
Workshop in Sydney.
Due to several successful satellite launches and due to the first switch of a PRN code in the
BeiDou constellation, the number of data sets for Galileo, BeiDou-2 and IRNSS/NavIC
increased to 20, 17, and 7, respectively. Due to the lack of phase center offset (PCO)
information, the new generation of BeiDou-3 satellites launched in 2015/16 could not be
considered for the IGS model so far.
In September 2016 (week 1915), the conventional MGEX PCO values for the Galileo
satellites were replaced by PCO estimates derived from terrestrial data after a coordinatedeffort of three ACs (Steigenberger et al. 2016). Because of the switch from igs08.atx toigs14.atx, these values will probably have to be adapted again. The suitability of IOV
pre-launch calibrations (European GNSS Service Centre 2016) for IGS purposes will haveto be evaluated by the Multi-GNSS Working Group.
Apart from the satellite antennas, the IGS model igs08.atx contained phase center calibration values for 304 different receiver antenna types at the end of 2016. With theswitch to igs14.atx and the consideration of 17 additional absolute robot calibrations, thetotal number could be increased to 310, whereas the number of copied and converted
field calibrations could be reduced at the same time. Among the 310 different types are
101 combinations of an antenna with a certain radome, whereas the remaining 209 antenna
types are not covered by a radome.
As Table 2 shows, igs14_ 1928.atx contained, among others, 181 absolute robot cali-140

2 Updates and content of the antenna phase center model

Table 1: Updates of the phase center model igs08_ wwww.atx in 2016 (wwww: GPS week of therelease date; model updates restricted to additional receiver antenna types are only
announced via the IGS Equipment Files mailing list)
Week

Date

IGSMAIL

1879

12-JAN-16

7227

1880

20-JAN-16—

1881

28-JAN-16

7239

1882

02-FEB-16

7242

1884
1885

16-FEB-16
22-FEB-16

7249
7252

1886

26-FEB-16

7258

1887

10-MAR-16

7268

1888

18-MAR-16

7272

1899

31-MAY-16

7308

1900

09-JUN-16

7314

1903

28-JUN-16

7323

1904

08-JUL-16—

1911

26-AUG-16—

1914

14-SEP-16

7353

1915

23-SEP-16

7356

1918

14-OCT-16

7361

ChangeAdded E208, E209
Decommission date: G034
Added TWIVP6000
NONE
Added TPSCR.G5
NONE
TPSCR.G5C
NONE
TPSCR.G5C
TPSH
Added G049 (G04)
Decommission date: G023 (G32)
Added R802 (R17), R802 (R27)
Decommission date: R714 (R17), R802 (R27)
Added G070
Added R802 (R09), R714 (R17)
Decommission date: R736 (R09), R802 (R17)Satellites RENAMED: R754 → R854, R755 → R855
Added R851
Decommission date: R714 (R17)
Added R736 (R16)
Decommission date: R738 (R16)
Added TRMR2
NONE
Added I005, I006
Added CHCI80
NONE
Added C017, I007
E201/E202: nadir angle extended to 16 degrees
Added E210, E211
Added SOKSA500
NONE
Added R853
Decommission date: R723
Added LEIGS15.R2
NONE
LEIGS16
NONE
Added CHAPS9017
NONE
LEICGA60NONE
MVEGA152GNSSA
NONE
Added G032 (G04)
Decommission date: G049 (G04)
Offset UPDATED: E101, E102, E103, E104,
E201, E202, E203, E204, E205, E206, E208,
E209, E210, E211
Added C017 (C13)
Decommission date: C014 (C13), C017 (C15)141

Antenna Working Group
Table 1: continued
Week

Date

IGSMAIL

1924

25-NOV-16—

1926

07-DEC-16

7386

1927

15-DEC-16

7392

1928

22-DEC-16—

ChangeAdded JAVTRIUMPH_ 2A+G JVGRTPSHIPER_ HRNONETPSHIPER_ HR+PS NONE
Added G034 (G04), E207, E212, E213, E214
Decommission date: G032 (G04)
Added GMXZENITH15
NONE
Added R723 (R12)
Decommission date: R737
Added TRM105000.10
NONE
TRM115000.00
NONE
TRM115000.00
TZGD
TRM115000.10
NONE

Table 2: Number of data sets in igs08_ 1928.atx and igs14_ 1928.atx (released in December
2016)
Satellite antennas
GPS
GLONASS
Galileo
BeiDouQZSSIRNSS/NavIC

Number
94
101
20
17
1
7

Receiver antennas
ROBOT
FIELD
COPIEDCONVERTED

Numberigs08.atx

igs14.atx

164
90
36
14

181
81
34
14

brations and 81 converted field calibrations. As elevation- and azimuth-dependent calibration values down to 0◦ elevation are mandatory for new or upgraded IGS stations,altogether 218 different antenna types (181 ROBOT + 34 COPIED + 3 CONVERTED) wereapproved for installation after the switch to igs14.atx. The remaining 92 types (81 FIELD+ 11 CONVERTED) are no longer allowed, but their calibration values are still necessary forexisting installations (see Sect. 3) as well as for reprocessing purposes.

3 Calibration status of the IGS network
Table 3 shows the percentage of IGS tracking stations with respect to certain calibration
types. For this analysis, 504 IGS stations as contained in the file logsum.txt (available
at ftp://igs.org/pub/station/general/) on 5 January 2017 were considered. At thattime, 97 different antenna/radome combinations were in use within the IGS network. The

142

References
Table 3: Calibration status of 504 stations in the IGS network (logsum.txt of 5 January 2017,
igs08_ 1928.atx vs. igs14_ 1928.atx) compared to former years

Date
DEC 2009
MAY 2012
JAN 2013
JAN 2014
JAN 2015
JAN 2016
JAN 2017

Absolute calibration(azimuthal corrections
down to 0◦ elevation)

Converted field calibration(purely elevation-dependent
PCVs above 10◦ elevation)

Uncalibrated radome(or unmodeled
antenna subtype)

61.4%
74.6%
76.8%
78.7%
80.1%
83.0%
84.9%
90.7%

18.3%
8.2%
7.7%
7.8%
7.5%
6.5%
6.2%
2.2%

20.2%
17.2%
15.5%
13.5%
12.4%
10.5%
8.9%
7.1%

igs08.atx:
igs14.atx:

calibration status of these antenna types was assessed with respect to the phase centermodels igs08_ 1928.atx and igs14_ 1928.atx that were released in December 2016.
Over the last years, the percentage of stations with state-of-the-art robot-based calibrations has improved by about 2% per year. This moderate increase mainly resulted fromthe upgrade of the equipment at operational stations and from the decommissioning ofstations with outdated equipment. The switch to igs14.atx yielded another improvementof about 6% due to the availability of additional robot-based calibrations. In the caseof nine antenna types, the latter could replace converted field calibrations (cf. Table 2).
Besides, new calibrations for certain antenna/radome combinations became available.
Ten years after the adoption of absolute robot calibrations by the IGS in November 2006,
the percentage exceeds 90% for the first time. For most of the remaining 47 stations withinappropriate phase center corrections a calibration with a robot is not possible, as theradome (AUST, DOME, ENCL, JPLA, OSOD, SCPL) is not directly connected to the antenna.
Only 15 of the 47 stations are equipped with antenna types for which a calibration would
be possible (see Table 4) and still desirable for future model updates.

References
Dilssner F., T. Springer, E. Schönemann, and W. Enderle. Evaluating the pre-flight GPS
Block IIR/IIR-M antenna phase pattern measurements. IGS Workshop, Sydney, 2016.
European GNSS Service Centre. Galileo IOV satellite metadata. https://www.gsceuropa.eu/support-to-developers/galileo-iov-satellite-metadata, 2016.
Rebischung P. and R. Schmid. IGS14/igs14.atx: a new framework for the IGS products.
AGU Fall Meeting, San Francisco, CA, 2016.

143

Antenna Working Group
Table 4: Calibratable antenna/radome combinations for which robot-based values are missing inJanuary 2017
Antenna

Radome3S-02-TSADM
AOAD/M_ T
ASH701933B_ M
ASH701945B_ M
ASH701945C_ M
ASH701945E_ M
ASH701945G_ M
TPSCR.G3
Sum

NONE
SCIS
SCIS
SCIT
SCIT
SCIT
SCIT
SCIT

IGS stations
1
1
2
4
3
2
1
1
15

Rebischung P., R. Schmid, and T. Herring. Upcoming switch to IGS14/igs14.atx.
IGSMAIL-7399, IGS Central Bureau, 2016.
Schmid R., R. Dach, X. Collilieux, A. Jäggi, M. Schmitz, and F. Dilssner. Absolute IGS
antenna phase center model igs08.atx: status and potential improvements. Journal of
Geodesy, 90(4):343–364, doi 10.1007/s00190-015-0876-3, 2016.
Steigenberger P., M. Fritsche, R. Dach, R. Schmid, O. Montenbruck, M. Uhlemann, andL. Prange. Estimation of satellite antenna phase center offsets for Galileo. Journal of
Geodesy, 90(8):773–785, doi 10.1007/s00190-016-0909-6, 2016.

144

Bias and Calibration Working Group
Technical Report 2016
S. Schaer
Swiss Federal Office of Topography (swisstopo)
Seftigenstrasse 264, CH–3084 Wabern, Switzerland
E–mail: stefan.schaer@aiub.unibe.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, careful treatment of measurement biases in legacy and new signals
becomes more and more crucial for combined analysis of multiple GNSS.
The IGS BCWG was established in 2008. More helpful information and related internet links may be found at http://igs.org/projects-working-groups/bcwg. For an
overview of relevant GNSS biases, the interested reader is referred to (Schaer 2012).

2 Activities in 2016
• Regular generation of P1–C1 bias values for the GPS constellation (based on indirect
estimation) and maintenance of receiver class tables was continued at CODE/AIUB.
• The finalization of the new Bias-SINEX Format Version 1.00 was a key challenge
and achievement in 2016 (see also Section 4).
• At CODE, a refined GNSS bias handling to cope with all available GNSS systems
and signals has been implemented and activated (in May 2016) in all IGS analysis

145

Bias and Calibration Working Group
C1C

C1W

C2C

C2L

C2S

C2W

C5Q

C5X

Code bias [ns]

20

0

G032
G041
G043
G044
G045
G046
G047
G048
G050
G051
G052
G053
G054
G055
G056
G057
G058
G059
G060
G061
G062
G063
G064
G065
G066
G067
G068
G069
G070
G071
G072
G073

−20

Figure 1: Observable-specific code bias estimates for all available GPS code observable types(using the RINEX3 nomenclature) and GPS SV numbers, computed at CODE. Notethat G032–G061 correspond to Block IIA, IIR, IIR-M; G062–G073 correspond to Block
IIF satellite generations.

lines. As part of this major revision, processing steps relevant to bias handling andretrieval were reviewed and completely redesigned.
• It should be mentioned that the current GPS C1W-C1C DSB (P1-C1 DCB) productprovided by CODE corresponds to a converted extract from our new OSB final/rapid
product line.
• Our new bias implementation allows to combine bias results at normal-equation(NEQ) level. We are thus able to combine bias results obtained from clock analysis and from ionosphere analysis, and, moreover, to compute coherent long-term
OSB solutions. This could be already achieved for the period starting with epoch
2016:136:00000 up to now. Corresponding long-term OSB solutions are updated
daily (see GPS/GLONASS bias results shown in Figures 1 and 2).
• The tool developed for direct estimation of GNSS P1–C1 and P2–C2 DCB values is(still) used to generate corresponding GPS and GLONASS bias results on a daily
basis.
• The ambiguity resolution scheme at CODE was extended (in 2011) to GLONASS
for three resolution strategies. It is essential that self-calibrating ambiguity resolution procedures are used. Resulting GLONASS DCPB(differential code-phase bias)
results are collected and archived daily.
• More experience could be gained concerning station-specific GLONASS-GPS intersystem translation parameters, which are estimated and accumulated as part of
CODE’s IGS analysis (but completely ignored for all submissions to IGS).

146

3 Last Reprocessing Activities
C1C

C1P

C2C

C2P

Code bias [ns]

20

10

0

R855

R854

R853

R851

R802

R801

R747

R745

R744

R743

R742

R737

R736

R735

R734

R733

R732

R731

R730

R721

R720

R719

R717

R716

R715

−10

Figure 2: Observable-specific code bias estimates for all available GLONASS code observabletypes (using the RINEX3 nomenclature) and GLONASS SV numbers, computed at
CODE.

• CODE’s enhanced RINEX observation data monitoring was continued. Examples
may be found at:
ftp://ftp.unibe.ch/aiub/igsdata/odata2_day.txt
ftp://ftp.unibe.ch/aiub/igsdata/odata2_receiver.txt
ftp://ftp.unibe.ch/aiub/igsdata/y2016/odata2_d335.txt
ftp://ftp.unibe.ch/aiub/igsdata/y2016/odata2_d335_sat.txt
Internally, the corresponding information is extracted and produced using metadata
stored in an xml database (established in December 2014).
• This RINEX monitoring service is provided in addition for MGEX observation data(available in RINEX3 format). See: ftp://ftp.unibe.ch/aiub/mgex/y2016/

3 Last Reprocessing Activities
In 2012: A complete GPS/GLONASS DCB reprocessing was carried out at CODE on thebasis of 1990–2011 RINEX data. The outcome of this P1–C1 and P2–C2 DCB reprocessing
effort is: daily sets, a multitude of daily subsets, and in addition monthly sets.
In 2016/2017: A GNSS bias reprocessing (for GPS/GLONASS) using the recently implemented observable-specific code bias (OCB) parameterization was initiated at CODE for
1994-2016 RINEX data. The outcome of this reprocessing effort are daily NEQs for GPS
and GLONASS OCB parameters from both global ionosphere and clock estimation. A

147

Bias and Calibration Working Groupconsistent time series of global ionosphere maps (GIMs) with a time resolution of 1 hour
is an essential by-product of this bias reprocessing effort. Analysis and combination ofthese daily code bias (NEQ) results is planned for 2017.

4 Bias-SINEX Format Version 1.00
A finalized draft version for the new Bias-SINEX Format (Version 1.00) was announcedin (Schaer 2016b):
http://www.aiub.unibe.ch/download/bcwg/format/draft/sinex_bias_100_dec07.pdf
This format version has been developed on the basis of• a first draft proposed and discussed at the IGS Bias Workshop 2015 in Bern, Switzerland,• an updated draft prepared for the IGS Workshop 2016 in Sydney,• substantial inputs from the IGS MGEX community (in particular from Oliver Montenbruck, DLR, Germany), and• our experiences gained as part of the GNSS bias implementation performed at
CODE.
The latest essential updates since the IGS Workshop 2016 included:• Bias-SINEX was completely decoupled from the SINEX format and corresponding
format descriptions.
• The previously used 2-digit year tag (YY) was generally replaced by a 4-digit year
tag (YYYY) for all time tags (YYYY:DDD:SSSSS).
• Numerous bias (.BIA) example files could be prepared based on the new GNSS bias
products generated at CODE.
The latest format document (and the entire format document history) may be found at:
http://www.biasws2015.unibe.ch/documents.html

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.

148

References
Schaer, S. Bias and Calibration Working Group Technical Report 2015. In: Y. Jeanand R. Dach (Eds): IGS Technical Report 2015, Astronomical Institute, University ofBern, June 2016, pp. 146–151.
Schaer, S. SINEX_BIAS—Solution (Software/technique) INdependent EXchange Format
for GNSS Biases Version 1.00, December 7, 2016a. ftp://ftp.unibe.ch/aiub/bcwg/
format/draft/sinex_bias_100_dec07.pdf.
Schaer, S. IGSMAIL-7387: Bias-SINEX V1.00 (and updated bias products from CODE),
2016b https://igscb.jpl.nasa.gov/pipermail/igsmail/2016/008577.html.

149

IGS Data Center Working Group
Technical Report 2016
C. NollNASA Goddard Space Flight Center, Code 61A
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
2.1 Meetings
A meeting of the IGS DCWG was held in conjunction with the IGS Infrastructure Committee (IC) and RINEX Working Group during the 2016 IGS Workshop in Sydney Australia
in February 2016. The DCWG portion of the splinter meeting reviewed recommendations
from the 2014 workshop, of which all three were completed. The main issues discussed at
the splinter meeting revolved around supporting the integration of RINEX V3 data into
the operational IGS archive, mainly by accepting data using the new RINEX V3 filename
format.
The following recommendations from the IGS DCWG were put forward at the workshop:• Encourage providers of RINEX V3 data to submit files (daily/hourly/high-rate)using V3 filename conventions to IGS data centers by the end of 2016. Until this150

2 Recent Activities
task is implemented by the stations, GDCs should create the files using the V3
naming conventions.
Progress: Starting with data from January 01, 2016, the IGS GDCs at CDDIS and
IGN integrated RINEX V3 data following the V3 naming conventions into theirmain, operational directories. See Section 2.2 for more information.
• ACs and users in general should begin utilizing RINEX V3 data in the V3 filename
format.
• Encourage DCWG to strive for implementation of XML Site Log Metadata System.
In addition, encourage stakeholders to submit use cases (examples of the required
interactions with the system) for XML Site Log Metadata System. Progress: See
Section 2.3 on Site Log Metadata developments.

2.2 RINEX V3 Integration
The current parallel structure found at the IGS global data centers (GDCs) supporting
the Multi-GNSS Experiment (MGEX) limits the motivation of the ACs to switch to the
RINEX V3 format. Integration of the two data archives promotes use of multi-GNSS data
and the new format. The IGS IC developed the âĂĲRINEX V3 Transition PlanâĂİ toaccomplish the integration and two IGS GDCs (CDDIS and IGN) began storing RINEX
V3 data submitted using the V3 filenaming convention into the operational archives inearly 2016.
Questions still to be addressed include how to handle RINEX V3 data not supplied in the
new filename convention. DCs could use tools such as gfzrnx to create these files withlong filenames at the DCs but getting the files from the station operators is preferred.
The DCWG will continue to work with the IC on using tools such as Anubis to QC RINEX
V3 data and supply the QC information through the data centers in summary/status files
as has been done for data in RINEX V2 format.

2.3 Site Metadata Activities
Another area of interest for the IGS IC and DCWG involves metadata, particularly inthe area of site logs. The IGS Central Bureau (CB) uses the Site Log Manager System
for handling IGS site logs, which provides a basis for promoting the transmission of theselogs in XML format. An XML/database management approach to site logs provides
several advantages, such as rapid update of site log contents, utilization of consistent
information across data centers, and availability of more accurate station metadata. The
DCWG held email discussions and teleconferences to continue the collaboration begun
in 2015. The 2015 discussions included adoption of GeodesyML to include the Site Log
XML schema (GeodesyML is an application schema of the Open Geospatial Consortium151

3 Future Plans
GML standard). Based on teleconference discussions and following further discussions at
the 2016 IGS Workshop, the team at Geoscience Australia completed the agreed-upon
modifications to the Site Log XML schema and released GeodesyML 0.3. Once several
participants began working with this version, some refinements were identified for the Site
Log XML schema. Several institutions in addition to GA, including ROB, BKG, GFZ,UNAVCO and GNS, have begun to experiment with implementing GeodesyML/Site Log
XML in test environments. Software tools that can be used for conversion between text
and XML formatted site logs are in development and can be shared among all groups.

3 Future Plans
The DCWG will continue to coordinate with the IC, RINEX Working Group, and MGEX
activity to fully realize the integration of data in RINEX V3 format into the main, operational archives at the IGS GDCs. The integration of these files with âĂĲlongâĂİ/RINEX
V3 filenames into the operational archives is progressing for data in 2016. Data centerswill continue to test software for creating files using this V3 filename format to support
the integration task. Once these procedures are reviewed by the IC and tested, DCs will
provide files following the V3 naming convention in the operational archives for MGEX
data prior to 2016. Work on the site metadata activity will also continue. Additional
topics the WG hopes to address follow.
• Support of the IGS Infrastructure Committee: A major focus of the DCWG will be
to continue its support the IC in its various activities to coordinate the resolution ofissues related to the IGS components. These activities will address recommendations
from the 2016 IGS Workshop as well as past workshops, including assessment andmonitoring of station performance and data quality, generating metrics on thesedata.
• Compression: As per a recommendation from past IGS workshops, the DCWG
will develop a plan for the introduction of a new compression scheme into the IGS
infrastructure by evaluating tests of available tools, surveying the IGS infrastructure,making a recommendation on a new IGS compression scheme, and coordinating
recommendations with the IC to develop implementation schedule. All data in
RINEX V3 format using the V3 naming convention are supplied and archived ingzip format.
• Next meeting: A meeting of the DCWG is planned for the next IGS workshop in
2017.

152

4 Membership

4 Membership• Carey Noll (NASA GSFC/USA), Chair• Yehuda Bock (SIO/USA)• Fran Boler (UNAVCO)• Ludwig Combrinck (HRAO/South Africa)• Bruno Garayt (IGN/France)• Kevin Choi (NOAA/USA), ex-officio• Heinz Habrich (BKG/Germany)• Michael Moore (GA/Australia)• Ruth Neilan (JPL/USA), ex-officio• Markus Ramatschi (GFZ/Germany)• Nacho.Romero (ESA/Germany)• Mike Schmidt (NRCan/Canada)• Giovanni Sella (NOAA/USA)• Grigory Steblov (RDAAC/Russia)• Dave Stowers (JPL/USA)153

4 Membership154

Ionosphere Working Group
Technical Report 2016
A. Krankowski1∗, M. Hernandez-Pajares2 , I. Cherniak1 ,D. Roma-Dollase2,10 , I. Zakharenkova1 , R. Ghoddousi-Fard3 ,Y. Yuan4 , Z. Li5 , H. Zhang6 , C. Shi6 , J. Feltens7 ,A. Komjathy8 , P. Vergados8 , S. C. Schaer9 ,A. Garcia-Rigo2 , J. M. Gómez-Cama10
1
2
3
4
5
6
7
8
9
10

Space Radio–Diagnostics Research Centre
University of Warmia and Mazury in Olsztyn, Poland (SRRC/UWM)
UPC–IonSAT, Barcelona, Spain
Canadian Geodetic Survey, Natural Resources Canada, Ottawa, Canada
Institute of Geodesy and Geophysics (IGG)
Chinese Academy of Sciences (CAS), Wuhan, China
Academy of Opto–Electronics (AOE), Chinese Academy of Sciences (CAS)Beijing, China
GNSS Research Center (GRC) of Wuhan University, Wuhan, China
ESOC/ESA, Darmstadt, Germany
JPL/NASA, Pasadena, CA, USA
CODE/swisstopo, Bern/Wabern, Switzerland
UB–D.Electronics, Spain

1 General goals
The Ionosphere Working group started the routine generation of the combine Ionosphere
Vertical Total Electron Content (TEC) maps in June 1998. This has been the main activity so far performed by the four IGS Ionosphere Associate Analysis Centers (IAACs):
CODE (Center for Orbit Determination in Europe, Astronomical Institute, University ofBerne, Switzerland), ESOC (European Space Operations Center of ESA, Darmstadt, Germany), JPL (Jet Propulsion Laboratory, Pasadena, California, U.S.A), and UPC (Technical University of Catalonia, Barcelona, Spain). Independent computation of rapid and∗Chair of Ionosphere Working Group

155

Ionosphere Working Group
final VTEC maps is used by the each analysis centers: Each IAACs compute the rapid
and final TEC maps independently and with different approaches including the additional
usage of GLONASS data in the case of CODE.

2 Membership• Dieter Bilitza (GSFC/NASA)• Ljiljana R. Cander (RAL)• M. Codrescu (SEC)• Anthea Coster (MIT)• Patricia H. Doherty (BC)• John Dow (ESA/ESOC)• Joachim Feltens (ESA/ESOC)• Mariusz Figurski (MUT)• Alberto Garcia-Rigo (UPC)• Manuel Hernandez-Pajares (UPC)• Pierre Heroux (NRCAN)• Norbert Jakowski (DLR)• Attila Komjathy (JPL)• Andrzej Krankowski (UWM)• Richard B. Langley (UNB)• Reinhard Leitinger (TU Graz)• Maria Lorenzo (ESA/ESOC)• A. Moore (JPL)• Raul Orus (UPC)• Michiel Otten (ESA/ESOC)• Ola Ovstedal (UMB)• Ignacio Romero (ESA/ESOC)• Jaime Fernandez Sanchez (ESA/ESOC)• Schaer Stefan (CODE)• Javier Tegedor (ESA/ESOC)• Rene Warnant (ROB)• Robert Weber (TU Wien)• Pawel Wielgosz (UWM)• Brian Wilson (JPL)• Michael Schmidt (DGFI)• Mahdi Alizadeh (TU Vienna)• Reza Ghoddousi-Fard (NRCan)

Prof. Yunbin Yuan and Dr. Ningbo Wang from the Institute of Geodesy and Geophysics(IGG) of the Chinese Academy of Sciences (CAS) have solicited to be member of the IGS
Ionosphere WG. Taking into account that all of opinions about Prof. Yunbin Yuan and156

4 Key accomplishments
Dr. Ningbo Wang’s membership applications have been positive we are glad to welcome
Drs. Yuan and Wang to the WG.

3 Productsa 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 x 5 deg. x 2.5 deg (UTxLon.xLat.),• availability with a latency of 11 daysb rapid GIM• combination of CODE, ESA, JPL and UPC iono products conducted by UWM• temporal and spatial resolution - at 2 hours x 5 deg. x 2.5 deg (UTxLon.xLat.),• availability with a latency of less than 24 hours

c 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 x 5 deg. x 2.5 deg (UTxLon.xLat.),

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

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Ionosphere Working Group

5 Recommendations after IGS Workshop 2016, Sydney,
Australia
a To accept CAS-IGG, NRCan and WHU as new Ionospheric Analysis Centers, contributing to the IGS combined VTEC GIMs,.
b The IONEX format shall be updated in order to accommodate contributions from multiple constellation and adequately describe the associated differential code biases.
c Cooperation with IRI COSPAR group for potential improvement of both IRI and IGS
TEC.
d Cooperation with International LOFAR Telescope (ILT) for potential synergies

6 The pilot phase of the new IGS ionospheric product– TEC fluctuations maps; Space Radio–Diagnostics Research Centre,
University of Warmia and Mazury in Olsztyn, Poland (SRRC/UWM)
According to the resolution of the IGS Ionosphere Working Group, which has been passed
during the IGS Workshop 2014 in Pasadena, the new product – the ionospheric fluctuations
maps – was established as a pilot project of the IGS service. Taking into account that the
Earth ionosphere is formed by superimposing of Earth magnetic field and Solar irradiancelevel for the geomagnetic field the TEC fluctuations are calculated as a function of aspherical geomagnetic latitude and magnetic local time.

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

158

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

7 Comparing performances of seven different global VTEC ionospheric models in the
IGS context

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

In the updated version, more than 700 permanent stations (available both from UNAVCO
and EUREF databases) have been involved into analysis of the ionosphere fluctuation
service. In order to describe the TEC variability in the ionosphere, the Rate of TEC(ROT) and its deviation – Rate of TEC Index (ROTI) are used. The ROT is calculated
as the difference of two geometry-free observations for consecutive epochs. The ROTI
represents the ROT deviation over 5 minute periods with one minute resolution. This
ionospheric fluctuations service allows to estimate the levels of TEC fluctuations for spatial
range from 50 degree of the north geomagnetic latitude to the North Geomagnetic Pole.
The results have visualization as daily ROTI maps in polar coordinates with grid 2 degree(magnetic local time) and 2 degree (geomagnetic latitude). The every grid cell represents
the average weighted value of ROTI values included in this cell.
The final TEC fluctuations maps are written in the modified IONEX format. For ROTI
data storing it is proposed simple ASCII format based on grid 2 x 2 degree - geomagnetic
latitude from 89o to 51o with step 2 and corresponded to magnetic local time (00-24 MLT)
polar coordinates from 0 to 360.

7 Comparing performances of seven different global VTEC
ionospheric models in the IGS context
In this section two independent techniques to assess global Vertical Total Electron Content(VTEC) ionospheric models computed from GNSS data (GIMs) are applied in the context

159

Ionosphere Working Group

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

of the International GNSS Service (IGS): to the GIMs of CODE, ESA, JPL and UPC(analysis centers contributing since 1998.5), NRCAN (resuming its contribution), and,
Chinese Academy of Sciences (CAS) and Wuhan University (WHU) as new contributors.
Two important and complementing aspects of the ionospheric models are assessed: On
one hand the VTEC accuracy, by comparing with direct measurements of VTEC up
to the orbital height of dual-frequency altimeters (around 1200-1300 km, containing themost part of electro content affecting GNSS signals), providing them over the seas (i.e.
typically far from existing receivers, assessing mostly interpolation), and with almost nointerruption since the beginning of the IGS ionospheric service (missions TOPEX, JASON1 and JASON-2). And, on the other hand, the Slant Total Electron Content (STEC)
provided by the GIMs, typically not far from the receivers used in their computation, isassessed versus very precise direct STEC observations taken by GNSS receivers in different
regions of the world, not used in the GIMs computation.
The first VTEC assessment results obtained during the recent period of days 117 to 317,
2015, show a very good behaviour of the new GIMs (EMR, CAS & WHU) in termsof VTEC bias regarding to JASON2 direct measurements, compared with the existing
GIMs, contributing since 1998.5 (CODE, ESA, JPL & UPC). From the point of viewof the corresponding Standard Deviations, the new GIMs present, in general, similar, or
either better precision than the existing IGS GIMs and their combinations. The extended
VTEC assessment will be completed with the STEC one.
Finally the convenience of maintaining the good practice of a right asessment of ionosphericmodels, by using external measurements, absolutely independent from any of the comparedmodels, will be emphasized.
It is remarkable as well the general agreement of the bias, at 1 to few TECUs level, regarding the altimeter VTEC for the most part of analysis centers. This happens among dif-160

7 Comparing performances of seven different global VTEC ionospheric models in the
IGS context

Figure 5: VTEC GIMS Bias regarding JASON* VTEC (daily values, since days 2001.6 to2016.0).

ferent mapping functions used (related with the general leveling) and the topside electron
content climatology between the altimeter and GPS orbit (seen as variations interpreted as“inverse climatology”, <VTEC_alt – VTEC_GPS>, in the time series, appearing clearly
the Solar Cycle and seasonal cycles, among others.

161

Ionosphere Working Group162

Multi–GNSS Working Group
Technical Report 2016
P. Steigenberger1 , O. Montenbruck1
1

Deutsches Zentrum für Luft- und Raumfahrt (DLR)
German Space Operations Center (GSOC)
Münchener Straße 20
82234 Wessling, Germany
E-mail: peter.steigenberger@dlr.de

1 Introduction
In the beginning of 2016, the status of the Multi-GNSS Experiment (MGEX) of theInternational GNSS Service (IGS) was changed to a Pilot Project by the IGS Governing
Board. Nevertheless, the name “MGEX” will be retained due to the high recognition
received so far. A comprehensive overview of the status of MGEX as of October 2016 isgiven in the review paper of Montenbruck et al. (2017).
A few changes of membership of the Multi-GNSS Working Group (MGWG) occurred
during the reporting period:• Andrea Stürze succeeded Axel Rülke as representative of Bundesamt für Kartographie und Geodäsie (BKG)• Zhiguo Deng succeeded Mathias Fritsche as representative of Deutsches GeoForschungsZentrum (GFZ)• Satoshi Kogure moved from the Japan Aerospace Exploration Agency (JAXA) to
the Cabinet Office but is still member of the MGWG
• Inga Selmke joined the MGWG representing Technische Universität München (TUM)

2 GNSS Evolution
This section is limited to the evolving systems Galileo, BeiDou, and IRNSS. The satellite
launches of these systems in 2016 are listed in Table 1. The year 2016 marks several
important milestones, in particular for Galileo. In November, an Ariane-V launched four163

Multi–GNSS Working Group
Table 1: GNSS satellite launches in 2016.
Date

Satellite

Type

20 Jan 2016
01 Feb 2016
10 Mar 2016
29 Mar 201628 Apr 2016
24 Mai 201612 Jun 201617 Nov 2016

IRNSS-1E
BeiDou M3-S
IRNSS-1F
BeiDou IGSO 6IRNSS-1G
Galileo FOC FM-10/11
BeiDou GEO 7
Galileo FOC FM-07/12/13/14

IGSO
MEO
GEO
IGSO
GEO
MEO
GEO
MEO

Galileo satellites at the same time (GPS World Team 2016) increasing the number ofGalileo satellites in orbit from 14 to 18. Galileo Initial Services were officially declaredby the European Commission on 15 December 2016 (GSA 2016) based on a constellationof 11 satellites for the Open and the Public Regulated Service and 12 satellites for the
Search and Rescue service. An update of the Galileo Open Service Signal In Space Interface
Control Document was also published in December 2016 (European Union 2016). The two
Galileo satellites in eccentric orbit (GSAT-201/2) started an experimental transmission ofbroadcast messages in August 2016. The satellites are not included in the almanac and theinitial update rate was limited to three hours. Starting with November 2016, the update
rate was in general increased to 10 min.
Galileo IOV metadata were published by the European Global Navigation Satellite Systems Agency (GSA) on 16 December 2016 (European GNSS Service Center 2016). These
data include amongst others information about attitude, transmit antenna phase center
corrections, geometry and optical properties, as well as group delays. An important taskof the MGWG for 2017 will be the consolidation and exploitation of these data for thegeneration of the MGEX products.
BeiDou moved forward in completing its constellation with the launch of two second
generation (BDS-2) and one third generation (BDS-3) BeiDou satellites (Tan et al. 2016).
Version 2.1 of the BeiDou Interface Control Document (China Satellite Navigation Office2016) was published in November including several clarifications, e.g., for the ionosphericdelay model parameters, but not yet covering the BDS-3 signals.
With the launch of the 3rd GEO satellite, the 7-satellite constellation of the Indian Regional Navigation Satellite System (IRNSS) was completed in April 2016. Along with this,the system was renamed to “Navigation with Indian Constellation” (NAVIC).

164

4 Products

GAL
BDS
QZSS
IRNSS

Figure 1: Distribution of IGS multi-GNSS stations supporting tracking of Galileo (red), BeiDou(yellow), QZSS (blue), and IRNSS (black crosses) as of January 2017.

3 Network
In 2016, the number of IGS multi-GNSS stations increased from almost 130 to about
180, see Figure 1. About half of the stations also provide real-time streams, mainly via
the dedicated MGEX caster (http://mgex.igs-ip.net/) but also via the IGS-IP caster(http://igs-ip.net). Both casters are operated by BKG and provide the real-timestreams in different versions of the RTCM-3 MSM format. First Galileo E6- and IRNSS
L5-capable receivers were installed at several locations by Geoscience Australia. The
signals of the BDS-3 satellites (Xiao et al. 2016) can only be tracked on the B1 frequency
by selected receivers of the IGS network.

4 Products
Six analysis centers (ACs) contribute orbit and clock products to MGEX as listed inTable 2. A detailed review of the MGEX product quality is given in Montenbruck et al.
(2017). Recent results of individual ACs are given in Prange et al. (2017) for the Center for
Orbit Determination in Europe (CODE) and in Guo et al. (2016b) for Wuhan University.
Guo et al. (2017a) evaluated the MGEX Galileo, BeiDou, and QZSS orbit and clock
products and found an orbit consistency of 10 – 25 cm for Galileo, 10 – 20 cm for BeiDou
MEOs, 20 – 30 cm for BeiDou IGSOs, and 20 – 30 cm for QZSS.

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Multi–GNSS Working Group
Table 2: Analysis centers contributing to IGS MGEX.
Institution

Abbr.

GNSS

Centre National d’Etudes Spatiales/
Collecte Localisation Satellites (CNES/CLS)
Center for Orbit Determination in Europe (CODE)
Deutsches GeoForschungsZentrum (GFZ)
Japan Aerospace Exploration Agency (JAXA)Technische Universität München (TUM)
Wuhan University

grm

GPS+GLO+GAL

com
gbm
qzf
tum
wum

GPS+GLO+GAL+BDS+QZS
GPS+GLO+GAL+BDS+QZSGPS+QZSGAL+QZSGPS+GLO+GAL+BDS+QZSSteigenberger et al. (2016) estimated satellite antenna phase center offsets (PCOs) for
the Galileo satellites. They proposed rounded PCO values for three different groups ofGalileo satellites: In-Orbit Validation (IOV) satellites, Full Operational Capability (FOC)
satellites in nominal orbit, and FOC satellites in eccentric orbit (FOCe, i.e., GSAT-201
and -202). These PCO values are given in Table 3 and included in the IGS antenna model
starting with the release igs08_1915.atx (Schmid 2016). They are used by the MGEX
ACs since September 2016.
Table 3: Galileo satellite antenna PCOs as used within the IGS since September 2016. IOV:In-Orbit Validation; FOCe: Full Operational Capability in eccentric orbit; FOC: Full
Operational Capability in nominal orbit.

Satellite group
IOV
FOCe
FOC

x [cm]y [cm]z [cm]

−17
+16
+12

+3
−1
−1

+95
+105
+110

Version d of the SP3 format (Hilla 2016) was released in February 2016 but none of the
MGEX ACs currently uses this format. Major advantage of this format is the increased
number of 999 satellites compared to 85 in SP3-c.
The TUM AC switched to a more recent version of the Bernese GNSS Software andimplemented the a priori solar radiation pressure (SRP) model of Montenbruck et al.
(2015) as well as the “dynamic yaw steering attitude” model of Ebert and Oesterlin (2005)
for the Galileo satellites in November 2016 (Selmke 2016). Whereas the original modelof Montenbruck et al. (2015) is limited to Galileo IOV, Steigenberger and Montenbruck(2016) provide updated coefficients for the Galileo FOC satellites. Guo et al. (2017b)
developed an adjustable box-wing model for BeiDou MEO and IGSO satellites that inparticular improves the orbit quality during orbit-normal (ON) mode.
Fritsche (2016) adopted the IGS orbit and clock combination software to include Galileo,
BeiDou, and QZSS. They report weighted root-mean square differences with respect to166

4 Products
40

Radial [cm]

20

C11
C12
C14

0
−20
−40

Jan

Mar

May

Jul

Sep

Nov

Figure 2: Radial differences for CODE and GFZ BeiDou MEO satellite orbits.

the combined orbit of 5 cm for Galileo, 3 – 5 cm for BeiDou MEOs, 10 – 20 cm for BeiDou
IGSOs and QZSS in yaw-steering (YS) mode. During ON mode, these values can beexceeded by far, see Figure 2.
In April 2016, an Analysis section was established on the MGEX webpage (http://mgex.
igs.org/analysis/index.php). It is updated on a weekly basis and includes informationon- MGEX product availability;- GNSS satellite signal transmission for GPS, GLONASS, BeiDou, Galileo, IRNSS,
and SBAS;- Clock time series of individual BeiDou and Galileo satellites;- SLR residuals for GLONASS, BeiDou, Galileo, and QZSS;- Orbit comparisons between the various ACs for GPS, GLONASS, BeiDou (separately for MEO, IGSO, GEO), Galileo, and QZSS.
An example for the comparison of BeiDou MEO satellite orbits of CODE and GFZ isgiven in Figure 2. Large differences can be seen during ON mode as this attitude mode is
not yet considered by CODE.
Two ACs contribute Differential Code Bias (DCB) products to MGEX. Whereas the
Chinese Academy of Sciences (CAS) DCB product (Wang et al. 2016) is updated on a daily
basis, the Deutsches Zentrum für Luft- und Raumfahrt (DLR) product has a quarterly
update rate. Since the second quarter of 2016, the DLR DCB product is provided inversion 1.00 of the Bias SINEX format (Schaer 2016a). Please note that the December
2016 version of the Bias SINEX format (Schaer 2016b) uses a 4-digit year whereas theversion of February 2016 (Schaer 2016a) which is implemented by DLR uses a 2-digit year
for specifying validity intervals.

167

Multi–GNSS Working GroupAcronyms
BKG Bundesamt für Kartographie und Geodäsie
CAS Chinese Academy of Sciences
CLS Collecte Localisation Satellites
CNES Centre National d’Etudes Spatiales
CODE Center for Orbit Determination in Europe
DLR Deutsches Zentrum für Luft- und Raumfahrt
GFZ Deutsches GeoForschungsZentrum
JAXA Japan Aerospace Exploration Agency
TUM Technische Universität München

References
China Satellite Navigation Office. BeiDou Navigation Satellite System Signal In SpaceInterface Control Document, Open Service Signal (Version 2.1), 2016.
Ebert K. and W. Oesterlin. Dynamic yaw steering method for spacecraft, 2005.
European GNSS Service Center. Galileo IOV satellite metadata, 2016. URL https://www.gsc-europa.eu/support-to-developers/galileo-iov-satellite-metadata.
European Union. European GNSS (Galileo) Open Service Signal In Space Interface Control Document. OS SIS ICD Issue 1.3, Decenber 2016.
Fritsche M. Multi-GNSS orbit and clock combination: Preliminary results. In GeohpysicalResearch Abstracts, volume 18, 2016. EGU2016-7823.
GPS World Team. Galileo deals four of a kind. GPS World, 27(12):12, 2016.
GSA. European GNSS (Galileo) Initial Services: Open Service Definition Document.
Technical report, European Global Navigation Satellite Systems Agency, December
2016. URL https://www.gsc-europa.eu/sites/default/files/Galileo_OS_SDD_
V1.0_final.pdf.
Guo F., X. Li, X. Zhang, and J. Wang. Assessment of precise orbit and clock products
for Galileo, BeiDou, and QZSS from IGS Multi-GNSS Experiment (MGEX). GPS
Solutions, 21(1):279–290, 2017a. DOI 10.1007/s10291-016-0523-3.

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Guo J., G. Chen, Q. Zhao, J. Liu, and X. Liu. Comparison of solar radiation pressure
models for BDS IGSO and MEO satellites with emphasis on improving orbit quality.
GPS Solutions, 21(2):511-522, 2017b. DOI 10.1007/s10291-016-0540-2.
Guo J., X. Xu, Q. Zhao, and J. Liu. Precise orbit determination for quad-constellation
satellites at Wuhan University: strategy, result validation, and comparison. Journalof Geodesy, 90(2):143–159, 2016b. DOI 10.1007/s00190-015-0862-9.
Hilla S. The extended Standard Product 3 orbit format (SP3-d), 21 Feb. 2016, 2016. URL
ftp://igscb.jpl.nasa.gov/igscb/data/format/sp3d.pdf.
Montenbruck O., P. Steigenberger, and U. Hugentobler. Enhanced solar radiation pressure modeling for Galileo satellites. Journal of Geodesy, 89(3):283–297, 2015. DOI
10.1007/s00190-014-0774-0.
Montenbruck O., P. Steigenberger, L. Prange, Z. Deng, Q. Zhao, F. Perosanz, I. Romero,
C. Noll, A. Stürze, G. Weber, R. Schmid, K. MacLeod, and S. Schaer. The MultiGNSS Experiment (MGEX) of the International GNSS Service (IGS) – achievements,
prospects and challenges. Advances in Space Research, 59(7):1671-1697, 2017. DOI
10.1016/j.asr.2017.01.011.
Prange L., E. Orliac, R. Dach, D. Arnold, G. Beutler, S. Schaer, and A. Jäggi. CODE’s
five-system orbit and clock solution – the challenges of multi-GNSS data analyis.
Journal of Geodesy, 1(4):345-360, 2017. DOI 10.1007/s00190-016-0968-8.
Schaer S. SINEX_BIAS - Solution (Software/technique) INdependent EXchange Format
for GNSS Biases, Version 1.00, February 2016, 2016a. URL http://www.aiub.unibe.
ch/download/bcwg/format/draft/sinex_bias_100_feb07.pdf.
Schaer S. SINEX_BIAS - Solution (Software/technique) INdependent EXchange Format
for GNSS Biases, Version 1.00, December 2016, 2016b. URL http://www.aiub.
unibe.ch/download/bcwg/format/draft/sinex_bias_100_dec07.pdf.
Schmid R. [IGSMAIL-7356] igs08_1915.atx: Updated phase center offsets for Galileo
satellites, 2016. URL https://igscb.jpl.nasa.gov/pipermail/igsmail/2016/008546.html.
Selmke I. [IGSMAIL-7377] TUM MGEX, 2016. URL https://igscb.jpl.nasa.gov/
pipermail/igsmail/2016/008567.html.
Steigenberger P. and O. Montenbruck. Galileo status: orbits, clocks, and positioning. GPS
Solutions, 2016. DOI 10.1007/s10291-016-0566-5.
Steigenberger P., M. Fritsche, R. Dach, R. Schmid, O. Montenbruck, M. Uhlemann, andL. Prange. Estimation of satellite antenna phase center offsets for Galileo. Journal of
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169

Multi–GNSS Working GroupTan B., Y. Yuan, M. Wen, Y. Ning, and X. Liu. Initial results of the precise orbit determination for the new-generation BeiDou satellites (BeiDou-3) based on the iGMAS
network. ISPRS International Journal of Geo-Information, 5(11):196, 2016. DOI
10.3390/ijgi5110196.
Wang, N. Y. Yuan, Z. Li, O. Montenbruck, and B. Tan. Determination of differential code
biases with multi-GNSS observations. Journal of Geodesy, 90(3):209–228, 2016. DOI
10.1007/s00190-015-0867-4.
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170

IGS Reference Frame Working Group
Technical Report 2016
P. Rebischung1 , B. Garayt2 , Z. Altamimi1
1

2

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

1 Introduction
Besides the generation of the operational IGS SINEX combination products (Section 2),
the main activity of the Reference Frame Working Group in 2016 was the preparationof the IGS realization of ITRF2014, IGS14, and of the associated set of satellite andground antenna calibrations, igs14.atx, in cooperation with the Antenna Working Group(Section 3).

2 Operational SINEX combinations
Figure 1 shows the RMS of the AC station position residuals from the daily IGS SINEX
combinations of year 2016, i.e. the global level of agreement between the AC and IGS
combined station positions once reference frame differences have been removed. The RMSof the AC station position residuals have globally remained at the same levels as in 2015,
with two notable exceptions:• The RMS of GRG’s residuals have substantially decreased starting with GPS week
1915, after an error in the handling of ground antenna calibrations was corrected.
• The RMS of JPL’s residuals show several excursions actually due to numerical issues
which distorted a few daily JPL solutions during their pre-processing. The origin of
the problem has now been identified and solved.
The AC Earth Orientation Parameter (EOP) residuals from the IGS SINEX combinations of year 2016 (Figure 2 and 3) show similar features as in the previous years. The
main notable difference is the appearance of spikes in JPL’s pole coordinate residual time171

Reference Frame Working Group
4 mm

East

4 mm

3 mm

3 mm

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1880

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grg

ngs

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sio

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1890

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1930

GPS week

Figure 1: RMS of AC station position residuals from the 2016 daily IGS SINEX combinations.
All time series were low–pass filtered with a 10 cycles per year cut–off frequency.

series, corresponding to the same daily solutions with abnormally large station position
residuals.

3 Preparation of the IGS14/igs14.atx framework
After the latest release of the International Terrestrial Reference Frame (ITRF2014; Altamimi et al. (2016)) was published in January 2016, the Reference Frame Working Groupand the Antenna Working Group started preparing the IGS realization of ITRF2014,
IGS14, and the associated set of satellite and ground antenna calibrations, igs14.atx. Thispreparation included:• selection of the most suitable reference frame (RF) stations from the complete setof GNSS stations in ITRF2014, and design of a well–distributed core network of RF
stations for the purpose of aligning global GNSS solutions (Section 3.1),• updates of the ground antenna calibrations of various antenna types and assessmentof the impact of these updates on station coordinates (Section 3.2),• re—evaluation of the radial components of all GPS and GLONASS satellite antennaphase center offsets (Section 3.3),• actual implementation and validation of the new IGS14/igs14.atx framework (Section 3.4).
172

3 Preparation of the IGS14/igs14.atx framework

xp residuals (mas)yp residuals (mas)

0.0

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cod

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esa

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−1.6

sio

1880

1890

1900

1910

1920

1930

1880

1890

GPS week

1900

1910

1920

1930

GPS week

Figure 2: AC pole coordinate residuals from the 2016 daily IGS SINEX combinations. The
individual AC time series have been shifted by multiples of 0.2 mas for clarity.
xp rate residuals (mas/d)

yp rate residuals (mas/d)

LOD residuals (ms)

0

0

0.0

cod

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emr

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−8

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1880

1890

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1920

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−0.8
1880

1890

1900

1910

GPS week

1920

1930

sio
1880

1890

1900

1910

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1930

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Figure 3: AC pole rate and LOD residuals from the 2016 daily IGS SINEX combinations. The
individual AC time series have been shifted by multiples of 1 mas/d and 0.1 ms forclarity.

173

Reference Frame Working Group

Figure 4: Distribution of the IGS14 and of the former IGS08 RF stations.

3.1 IGS14 and IGS14 core network design
A first selection of the potential IGS14 RF stations from the full set of IGS stations in
ITRF2014 was made according to the following criteria:• ITRF2014 time series longer than 5 years; at least 1000 (daily) data points,• WRMS of ITRF2014 residual time series (including seasonal signals) smaller than
2.5 mmin horizontal and 7.5 mmin vertical,• maximum formal error of ITRF2014 coordinates over expected IGS14 lifetime smaller
than 1.5 mmin horizontal and 3 mm in vertical.
In ”dense” areas, multi–GNSS and real–time, but also previous IGb08 RF stations were favored, while in ”sparse” areas, a few stations had to be retained that do not strictly meet all
criteria. A notification was then sent to the operators of the pre–selected stations (thanks
to D. Maggert and N. Romero), resulting in slight adjustments of the station selection
according to the answers received. The final list of selected IGS14 RF stations comprises
252 stations (compared to 235 in IGb08) whose distribution is shown in Figure 4.
A well–distributed IGS14 core network was additionally designed for the purpose of aligning global GNSS solutions. It is composed of 51 clusters of stations (i.e., 51 primarystations, each with possible substitutes) selected to ensure a homogeneous global distri-174

3 Preparation of the IGS14/igs14.atx framework

Figure 5: Distribution of the 51 primary stations of the IGS14 core network.

bution (Figure 5) and the best possible temporal stability of the core network.

3.2 Ground antenna calibration updates and their impact on station
positionsCompared to igs08.atx, igs14.atx includes robot calibrations for 17 additional groundantenna types. 19 type–mean robot calibrations could also be updated thanks to theavailability of calibration results for additional antenna samples. The impact of theseground antenna calibration updates on IGS station positions was assessed by means ofdifferential PPP solutions. In general, the estimated position offsets are not negligible andcan reach up to 6 mm in horizontal and 19 mm in vertical (see ftp://igs-rf.ign.fr/
pub/IGS14/igs08_to_igs14_offsets.txt).
While ITRF2014 coordinates are consistent with the igs08.atx set of antenna calibrations,
IGS14 needs to be consistent with the updated igs14.atx set. After the coordinates ofthe 252 selected IGS14 stations were extracted from ITRF2014, they thus had to becorrected in order to account for ground antenna calibration updates from igs08.atx toigs14.atx. For that purpose, the position offsets estimated from our PPP analyses wereapplied to the ITRF2014 coordinates of the affected IGS14 stations whenever exceeding
1 mm in either direction. The coordinate corrections actually applied are listed in ftp:

175

Reference Frame Working Group//igs-rf.ign.fr/pub/IGS14/ITRF2014_to_IGS14.txt.
Finally, so that users can assess the impact of the ground antenna calibration updates fromigs08.atx to igs14.atx on the positions of specific (non–IGS) stations, a set of latitude–
dependent coordinate change models was developed and made available at ftp://igs-rf.
ign.fr/pub/IGS14/lat_models.txt.

3.3 Satellite antenna calibration updates
Despite the negligible scale difference between ITRF2008 and ITRF2014 (0.02 ppb), theradial components of all GPS and GLONASS satellite antenna phase center offsets (z–PCOs) had to be updated in igs14.atx, because of recent modeling changes affecting thescale of the IGS products (Earth radiation pressure, antenna thrust). This was achieved byderiving time series of satellite antenna z–PCO estimates, consistent with the ITRF2014
scale, from the daily repro2 and latest operational SINEX solutions of seven ACs. The AC
z–PCO time series were then trend–corrected to epoch 2010.0 before computing weighted
averages. The igs14.atx satellite antenna z–PCO values are therefore expected to giveaccess to the ITRF2014 scale at epoch 2010.0. From igs08.atx to igs14.atx, satellite
antenna z–PCOs change by –6 cm on average, which induces a net scale change of the
IGS terrestrial frame solutions by approximately +0.5 ppb (+3 mm).
Time series of satellite antenna x– and y–PCOs were also derived from the daily AC repro2
and operational SINEX solutions (Rebischung and Schmid 2016a)). They were however
found to be contaminated by large Sun–elevation– and eclipse–related signals, and theagreement between the mean values obtained from the different ACs was judged too poor
to use them to update the satellite antenna x– and y–PCOs in igs14.atx. Finally, only
the x– and y–PCOs of the GPS Block IIR satellites were updated in igs14.atx, based on
pre–flight calibration values (Dilssner et al. 2016).

3.4 Validation and implementation
Preliminary versions of IGS14 and igs14.atx were made available to the IGS ACs in July
2016. Parallel IGS14–based solutions were requested from the ACs providing final products
for validation purposes and combinations of the parallel AC SINEX solutions were carriedout for GPS weeks 1925–1929. The residuals of these test combinations were at the samelevel as in the operational combinations and the differences to the operational products
did not show any unexpected features.
In order to gain more insight into the impact of the switch from IGb08/igs08.atx toIGS14/igs14.atx on GNSS–derived geodetic parameters, the daily repro2 AC solutions
were additionally re–combined with two changes compared to the official daily repro2
SINEX combinations (Rebischung et al. 2016):

176

References• Satellite PCOs were fixed to their igs14.atx values in the input AC solutions.
• The combined solutions were aligned to the IGS14 core network.

The results of these test combinations are presented in (Rebischung and Schmid 2016b).
Only marginal impacts were obtained for both Earth Orientation Parameters and apparent
geocenter coordinates.
In coordination with the IERS, GPS week 1934 (29 January 2017) was finally chosen as thedate for the switch of the IGS products from the IGb08/igs08.atx to the IGS14/igs14.atx
framework. T he switch was announced to the community in [IGSMAIL–7399], together
with details about the elaboration of IGS14 and igs14.atx and their impact on user results.

References
Altamimi, Z., Rebischung P., Métivier, L., and Collilieux, X. ITRF2014: a new releaseof the International Terrestrial Reference Frame modeling nonlinear station motions.
Journal of Geophysical Research, 121(8):6109–6131, 2016. doi: 10.1002/2016JB013098
Dilssner, F., Springer., T, Schönemann, E.m and Enderle, W. Evaluating the pre–flight
GPS Block IIR/IIR–M antenna phase pattern measurements. Presented at IGS Workshop 2016, Sydney, Australia, 8–12 Feb. 2016
Rebischung, P., Altamimi, Z., Ray, J., and Garayt, B.. The IGS contribution to ITRF2014.
Journal of Geodesy, 90(7):611–630, 2016. doi: 10.1007/s00190–016–0897–6
Rebischung, P. and Schmid, R. Preparations for the IGS realization of ITRF2014. Abstract
EGU2016–7171 presented at EGU General Assembly 2016, Vienna, Austria, 17–22
Apr. 2016a
Rebischung, P. and Schmid, R. IGS14/igs14.atx: a new framework for the IGS products.
Abstract G41A-0998 presented at AGU Fall Meeting 2016, San Francisco, 12-16 Dec.
2016b

177

Reference Frame Working Group

178

IGS Realtime Service
Technical Report 2016
A. Rülke1 , L. Agrotis2
12

Federal Agency for Cartography and Geodesy
Richard-Strauss-Allee 11, 60598 Frankfurt am Main, Germany
e-mail: axel.ruelke@bkg.bund.de
European Space Operations Centre, European Space Agency
Robert-Bosch-Str. 5, 64293 Darmstadt, Germany
e-mail: loukis@symban.co.uk

1 Introduction
The Real Time Service (RTS) expands the capacity of the International GNSS Service(IGS) to support applications requiring real-time access. It utilises a global receiver network and provides infrastructure for data and product dissemination. Analysis products
include individual Analysis Centre as well as combination solutions. There is a large variety of potential applications for the service with a strong focus on scientific and educational
applications.

2 Observation network
The IGS-RTS is based on a global network of IGS stations providing data streams to the
RTS observation broadcasters. There are several observation broadcasters in operation
including the first level global casters at BKG, CDDIS and IGS Central Bureau. In orderto reduce work load for the operators second level casters are going to be installed. Thereis one caster already operating at Wuhan University/China. Another caster operated by
Geoscience Australia is almost ready to go live and will take care of users in the region ofSoutheast Asia and Australasia. Other regional data centres are proposed for North andSouth America and Europe. In order to improve redundancy in the case of failure, thestation operators are encouraged to provide their data streams to at least two independent
global data centres.

179RealTime Service

-180°
90°

-150°

-120°

-90°

-60°

-30°

0°

30°

60°

90°

120°

150°

180°
90°

60°

60°

30°

30°

0°

0°

-30°

-30°

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-180°

-150°

Status: 2017/01/31

-120°

-90°

GPS

-60°

-30°

GLONASS

0°

Galileo30°

60°

BeiDou

90°

120°

QZSS

150°

-90°
180°

SBAS

Figure 1: Global distribution of IGS real time sites from real time caster igs-ip.net.

The station network is operated by a large number of contributors on a best effort basis.
Figures 1 and 2 display the present distribution of sites across the globe for the IGS casterand the MGEX caster at BKG respectively. Since IGS supports open data standards bothcasters provide data streams following the RTCM standard. All streams on the IGS casterare receiver generated RTCM streams as supported by the receiver firmware. The streams
on the MGEX caster are converted from raw data by an external software conversion tool.
As soon as more receivers providing RTCM3 multi constellation data (MSM5 or better
MSM7) become available the number of software generated streams will be reduced.

3 State Space Respresentation correction streams
There are eight real time Analysis Centres (AC) which use different software packages tocompute epoch-wise orbit and clock products. The large number of ACs ensures a highredundancy of the service on the one hand and a strong quality control on the other hand.
The estimates are converted into RTCM SSR format and can be accessed via IGS RTS
product casters. The orbit products are available with respect to the satellite Antenna
Phase Centre (APC) and in most cases they are also available with respect to the Centreof Mass (CoM). The clock products are updated every 5 seconds. Table 1 gives a summaryof all individual product streams by the different ACs. The performance of the service isillustrated for GPS and GLONASS clocks and orbits in Figure 3.

180

3 State Space Respresentation correction streams

-180°
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Figure 2: Global distribution of IGS real time sites providing multi constellation GNSS datafrom real time caster mgex.igs-ip.net.

After processing the individual AC solutions in Real Time, RTS combination products
are made available to users of the service (Table 2). Two basic techniques, a single epoch
combination developed by ESOC and a Kalman filter based combination developed by
BKG and Prague Technical University, are used. Although a combination increases therobustness of the product it also increases the latency of the combined product significantly. Since many of the individual streams have a latency of about 10s or less, thelatency of the combined product is in the range of 20-30s. The reduction of latency is an
important goal of the real time service and requires an optimized selection of reference
stations and processing schemes.
The RTCM streams of the RTS can be used directly in order to perform Real Time Precise Point Positioning (PPP). In order to monitor the overall performance, a number ofstationary sites are processed continuously using all available correction streams. Figure 4 shows the real time results for the FFMJ reference station located in Frankfurt
am Main/Germany. The left subfigure clearly shows the typical running-in-characteristic(convergence time) of about 30 minutes after a re-initialization (cold start) of the processing. The right figure shows the present potential of the service in a long-running
experiment.

181

RealTime Service

Figure 3: Performance of orbit and clock estimates for the IGS RTS solutions. Top: IGC01
combination orbit and clock performance for GPS, bottom: Statistics for AC and
IGC03 solutions for GLONASS.

Figure 4: Performance of the coordinate estimates from FFMJ (Frankfurt am Main) from IGS
RTS correction data stream IGS03. Left: cold start with running-in-characteristic.
Right: warm start.

182

References

4 SummaryThanks to the contributions from a large number of partners, the IGS RTS operates
a dense high quality real time GNSS network. The observation data is used to derive
orbit and clock products which allow user PPP at decimetre accuracy. A limitation isthe convergence time of about 30 minutes and the latency of the combined products of
20-30s.
The IGS RTS ensures open access to its data and products and supports open standards
and data formats. Data and products are provided via TCP/IP connections. The range ofapplications is focused on scientific and educational topics, such as positioning, navigationand timing, Earth observations and research; and other applications that benefit thescientific community and society.

References
Caissy, M., L. Agrotis, G. Weber, M. Hernandez-Pajares, U. Hugentobler. The International GNSS Real-Time Service. GPS World, 52–58, 2012.
Rülke, A., L. Agrotis, W. Enderle, and K. MacLeod. IGS real time service - status, futuretasks an limitations. IGS Workshop 2016, Sydney, Australia.
Weber, G., L. Mervart, L. Agrotis, and A. Stürze. Real-time Combination of GNSS Orbit
and Clock Correctors for Precise Point Positioning. presented at IUGG/IAG General
Assembly, Melbourne, July 2011.

183

RealTime Service

Table 1: Correction streams from IGS Real Time Service by individual ACs
CenterDescription

NTRIP MP
CoM/APCBKG

GPS GPS + GLONASS RT orbits and clocks using IGU orbits
GPS + GLONASS RT orbits and clocks using IGU orbits
GPS RT orbits and clocks based on IGU orbits
GPS+GLONASS orbits and clocks
GPS RT orbits and clocks based on IGU orbits
GPS+GLONASS orbits and clocks (DLR caster)RT orbits and clocks using NRT batch orbits every 2 hours
which are based on IGS Batch hourly files
RT orbits and clocks using NRT batch orbits every 2 hours
which are based on RINEX files generated from the RT stream
RT orbits and clocks and IGU orbits
RT orbits and clocks based on NRT orbit solution
GPS orbits and clocks using NRT batch orbits every hour
GPS orbits and clocks based on IGU orbits

CLK00/10
CLK01/11
CLK92/93
CLK90/91
CLKC0/A0
CLKC1/A1

CNES
DLR
ESOC

GFZ
GMV
NRCan
WUHAN

CLK50/51
CLK52/53
CLK70/71
CLK81/80-/CLK22
CLK15/16

Table 2: Combined correction stream by IGS Real Time Service by individual Combination
Centres

184

CentreDescription

NTRIP MPESOC
BKG

GPS-only combination – epoch-wise approach
GPS-only combination – Kalman filter approach
GPS+GLONASS combination – Kalman filter approach

IGC01/IGS01-/IGS02-/IGS03

Tide Gauge Benchmark
Monitoring Working Group
Technical Report 2016
T. Schöne, R. Bingley, Z. Deng, M. Gravelle, J. Griffiths,
M. Guichard, H. Habrich, D. Hansen, T. Herring, A. Hunegnaw,
M. Jia, M. King, M. Merrifield, G. Mitchum, M. Moore,
R. Neilan, C. Noll, E. Prouteau, L. Sánchez,
A. Santamaría-Gómez, N. Teferle, D. Thaller, P. Tregoning,
S. Williams, G. Wöppelmann
May 11, 2017

1 Introduction
The Tide Gauge Benchmark Monitoring Working Group (TIGA) of the IGS continues its
support for climate and sea level related studies and organizations concerned herewith(e.g., GGOS, OSTST, UNESCO/IOC). The TIGA WG provides vertical geocentric positions, vertical motion and displacements of GNSS stations at or near a global network oftide gauges and works towards establishing local geodetic ties between the GNSS stations
and tide gauges. To a large extend the TIGA Working Group uses the infrastructure andexpertise of the IGS.
The main aims of the TIGA Working Group are:
1. Maintain a global virtual continuous GNSS @ Tide Gauge network
2. Compute precise coordinates and velocities of GNSS stations at or near tide gauges.
Provide a combined solution as the IGS-TIGA official product.
3. Study the impacts of corrections and new models on the GNSS processing of thevertical coordinate. Encourage other groups to establish complementary sensors to
improve the GNSS results, e.g., absolute gravity sites or DORIS.
4. Provide advice to new applications and installations.

185

3 Current data holding of TIGA reprocessed individual solutions

2 Main Progress in 2016
• TIGA Working Group members actively participated in the IGS Workshop in Sydney/Australia with several posters (see http://kb.igs.org/hc/en-us/sections/
200763007-2016-IGS-Workshop-Sydney-Australia)• Working group meeting during the IGS Workshop in Sydney/Australia• TIGA reprocessing period was extended by all TIGA analysis Centers to cover alldata to the end of 2015.
• GeoScience Australia is now contribution to the TIGA reprocessing• TIGA Network operator works with Tide Gauge and GNSS station operators to makeexisting stations available to TIGA, a main (ongoing) task is to update the current
database of existing local ties between GNSS and tide gauge benchmarks. By the endof 2016 about 173 local ties information are available at http://www.sonel.org/-Stability-of-the-datums-.html?lang=en. For the stations directly committed
to TIGA the number of ties raised to 76. The current number of GNSS@TG stations
is 820 stations (with 119 stations decommissioned).
• The TIGA-WG carried forward the GLOSS-Task “Priorities for installation of continuous Global Navigation Satellite System (GNSS) near to tide gauges. Report to
Global Sea Level Observing System (GLOSS)” by King, M.A. (2014) for the densification and extension of the TIGA Observing Network to GGOS. The response by
the GGOS Coordinating Board was received early 2017.

3 Current data holding of TIGA reprocessed individual
solutions
Table 1: Current data holding of TIGA reprocessed individual solutions.

TIGA Analysis Center (TAC)

Start GPS week

End GPS week

AUT (Geoscience Australia)
BLT (University of Nottingham ,BLT (University of Luxembourg)
DG2 (DGFI/TUM Germany)
GT2 (GFZ Potsdam TIGA Solution)
UL2 (University La Rochelle)

0834

1891

0782
0887
0730
0782

1722
1824
1877
1773

186

4 TIGA Working Group Members in 2016

4 TIGA Working Group Members in 2016
Working group members are listed in Table 2.
Table 2: TIGA Working Group Members in 2016
Name

EntityHost Institution, Country

Guy Wöppelmann
Laura Sánchez
Heinz Habrich
Minghai Jia
Paul Tregoning
Zhiguo Deng
Daniela Thaller
Norman Teferle
Richard Bingley
Ruth Neilan
Tom Herring
Michael Moore
Carey Noll
Tilo Schöne
Simon Williams
Gary Mitchum
Mark Merrifield
Matt King

TAC, TNC, TDC
TAC
TAC

University La Rochelle, France
DGFI TU Munich, Germany
BGK, Frankfurt, Germany
GeoScience Australia, Australia
ANU, Australia
GFZ Potsdam, Germany
BGK, Frankfurt, Switzerland
University of Luxembourg, Luxembourg
University of Nottingham, UK
ex officio, USA
ex officio, USA
ex officio, Australia
CDDIS, NASA, USA
GFZ Potsdam, Germany
PSMSL, NOC Liverpool, UK
University of South Florida, USA
UHSLC, Hawaii, USA
University of Tasmania, Australia

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

187

IGS Troposphere Working Group
Technical Report 2016
S. M. Byram
United States Naval Observatory
3450 Massachusetts Avenue Northwest
Washington DC 20392 USA
sharyl.byram@usno.navy.mil

1 Introduction
The IGS Troposphere Working Group (IGS TWG) was founded in 1998. The United States
Naval Observatory (USNO) assumed chairmanship of the WG as well as responsibility for
producing IGS Final Troposphere Estimates (IGS FTE) in 2011.
Dr. Christine Hackman chaired the IGS TWG through December 2015. Dr. Sharyl Byram
has chaired it since then and also oversees production of the IGS FTEs. IGS FTEs areproduced within the USNO Earth Orientation Department GPS Analysis Division, which
also hosts the USNO IGS Analysis Center.
The IGS TWG is comprised of approximately 50 members (cf. Appendix A). A revised
charter approved by the IGS Governing Board at the close of 2011 is shown in Appendix
B.

2 IGS Final Troposphere Product Generation/Usage 2016
USNO produces IGS Final Troposphere Estimates for nearly all of the stations of the
IGS network. Each 24-hr site result file provides five-minute-spaced estimates of total
troposphere zenith path delay (ZPD), north, and east gradient components, with thegradient components used to compensate for tropospheric asymmetry.
IGS Final Troposphere estimates are generated via Bernese GNSS Software Dach et al.
(2015) using precise point positioning (PPP, (Zumberge et al. 1997)) and the GMF map-

188

ZPD files/day

350

station list update

improved reults screening

400

station list update

2 IGS Final Troposphere Product Generation/Usage 2016

300

250
2012
Mean: 302

2011
Mean: 322

2013
Mean: 325

2014
Mean: 326

2016
Mean: 375

2015
Mean: 323

200

0

364

728

1092
days since 1 Jan 2011

1456

1820

2184

Figure 1: Number of IGS receivers for which USNO produced IGS Final Troposphere Estimates,
2011-6. (Estimates were produced by Jet Propulsion Laboratory up through mid-April
2011.)

ping function Boehm et al. (2006) with IGS Final satellite orbits/clocks and earth orientation parameters (EOPs) as input. Each site-dayâĂŹs results are completed approximately
three weeks after measurement collection as the requisite IGS Final orbit products become
available. Further processing details can be obtained from (Byram and Hackman 2012)
Figure 1 shows the number of receivers for which USNO computed IGS FTEs 2011-6.
The average number of quality-checked station result files submitted per day in 2016 was375, much higher than the 2015 average value of 323 due to an updated station list in
December 2015. The result files can be downloaded from ftp://cddis.gsfc.nasa.gov/
gps/products/troposphere/zpd. 46.3 million files were downloaded in 2016 by users
from over 1000 distinct hosts Noll (2016), a marked increase in usage over the 20.9 million
files downloaded in 2015.
USNO will use Bernese GNSS Software 5.2 (www.bernese.unibe.ch/features) to compute troposphere estimates for the IGS Reprocessing 2 effort (acc.igs.org/reprocess2.
html).

189

3 IGS Troposphere Working Group Activities 2016

3 IGS Troposphere Working Group Activities 2016
The goal of the IGS Troposphere Working Group is to improve the accuracy and usabilityof GNSS-derived troposphere estimates. It does this by coordinating (a) working groupprojects and (b) technical sessions at the IGS Analysis Workshops.
The group meets twice per year: once in the fall in conjunction with the American Geophysical Union (AGU) Fall Meeting (San Francisco, CA, USA; December), and once inthe spring/summer, either in conjunction with the European Geosciences Union (EGU)
General Assembly (Vienna, Austria; April) or at the IGS Workshop (location varies; dates
typically June/July).
Meetings are simulcast online so that members unable to attend in person can participate.
Members can also communicate using the IGS TWG email list.

3.1 2016 Working Group Meetings
The working group met once in 2016: in conjunction with the 2016 IGS Workshop in
Sydney, Australia, February 2016. The meeting planned in conjunction with the 2016
AGU in San Francisco, CA was postponed due to Dr. Byram being unable to travel.
The February 2016 meeting featured presentations by:• WG chair S Byram on (1) the quality and production of IGS Final Troposphere
Estimates, (2) the status of current working-group projects, and (3) a discussion of
future projects• Dr. Jan Douša, Geodetic Observatory Pecny (GOP; Czech Republic) on the status of
the troposphere inter-technique comparison database/website (see "Working Group
Projects" below)
Presentations from the meeting were distributed via the IGS TWG email list (message
IGS-TWG-143) and can be obtained by contacting this report’s author.

3.2 Working Group Projects
3.2.1 Automating comparisons of troposphere estimates obtained using different
measurement or analysis techniques
One way to assess the accuracy of GNSS-derived troposphere estimates is to compare themto those obtained for the same time/location using an independent measurement technique,e.g., VLBI1 , DORIS2 , radiosondes, or from a numerical weather model. Comparisons
12

Very Long Baseline Interferometry
Doppler Orbitography and Radiopositioning Integrated by Satellite190

3 IGS Troposphere Working Group Activities 2016of GNSS-derived troposphere estimates computed by different analysis centers or using
different models can also serve this purpose.
The IGS TWG has therefore since 2012 been coordinating the creation of a database/website
to automatically and continuously perform such comparisons.
Dr. Jan Douša, Geodetic Observatory Pecny (GOP; Czech Republic) has been spearheading the development of the database Douša and Gyõri (2013); Gyõri and Douša (2016),
with contributions from other scientists at GOP, GeoForschungsZentrum (GFZ; Germany)and USNO. This database is now beta-complete and open for testing. Interested users cancontact Dr. Douša at jan.dousa@pecny.cz. Development of the website by which users
can directly view/access the values is underway.
In 2014, a grant proposal, Automated Intra- and Inter-technique Troposphere Estimate
Comparisons, made to the Kontakt II Czech-US research partnership by Dr. Douša withsupporting documents authored by then WG chair C Hackman, was funded. This funding supports, in addition to other items, travel to the US for joint US-Czech work on
the database/website. Dr. Douša thus worked with USNO scientists on further website/database development during a Kontakt II funded USNO site visit in November
2016.
Completion of this project is expected in 2017 when the website will be accessible to thecommunity. This system has received interest from climatologists/meteorologists, e.g.,
those associated with the GRUAN3 and COST4 Action 1206 (GNSS4SWEC) projects, as
it will simplify quality-comparison and perhaps acquisition of data used as input to theirstudies.

3.2.2 Standardization of the tropo_sinex format
The IGS Troposphere Working group also supports a project to standardize the tropo_sinex
format in which troposphere delay values are disseminated. At issue is the fact that different geodetic communities (e.g., VLBI, GNSS) have modified the format in slightly
different ways since the format’s introduction in 1997. For example, text strings STDEVand STDDEV are used to denote standard deviation in the GNSS and VLBI communities
respectively. Such file-format inconsistencies hamper inter-technique comparisons.
This project, spearheaded by IGS Troposphere WG members Drs. Rosa Pacione and
Jan Douša, is being conducted within the COST Action 1206 (GNSS4SWEC) Working
Group 3. This COST WG consists of representatives from a variety of IAG5 organizations
and other communities; its work is further supported by the EUREF Technical Working
3

GCOS (Global Climate Observing System) Reference Upper Air Network: http://www.gruan.org
European Cooperation in Science and Technology: http://www.cost.eu
5International Association of Geodesy
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4 How to Obtain Further Information
Group6 as well as E-GVAP7 expert teams. The WG is currently defining in detail a format
able to accommodate both troposphere values and the metadata (e.g., antenna height, local
pressure values) required for further analysis/interpretation of the troposphere estimates,with progress made in 2016, and a format to be circulated for discussion/approval in
2017. For more information, please contact Dr. Pacione at rosa.pacione@e.geos.it or
Dr. Douša.
3.2.3 Automated Analysis Center Estimate Comparisons
A suggestion was made by an IGS Analysis Center representative that the next working
group project should be to re-establish the troposphere estimate comparisons for each
AC. This project would consist of first comparing the Repro2 Analysis Center results inthe comparison database developed by J Douša and then automating the comparison of
the final troposphere estimates of the ACs as they become available. A survey asking
for interest and participation in such a comparison was sent via the IGS TWG email list
(message IGS-TWG-143) and AC email list (message IGS-ACS-1088).

3.3 Activities at the 2016 IGS Workshop
WG chair Dr. Sharyl Byram organized troposphere-related activities for the 2016 IGS
Workshop, soliciting presenters for the troposphere plenary and poster sessions, and holding the working-group meeting.

4 How to Obtain Further Information
IGS Final Troposphere Estimates can be downloaded from: ftp://cddis.gsfc.nasa.
gov/gps/products/troposphere/zpd
For technical questions regarding them, please contact Dr. Sharyl Byram at sharyl.
byram@usno.navy.mil.
To learn more about the IGS Troposphere Working Group, you may:
• contact Dr. Sharyl Byram at sharyl.byram@usno.navy.mil,• visit its website (under development): http://twg.igs.org, and/or• subscribe to its email list: http://igscb.jpl.nasa.gov/mailman/listinfo/igs-twg———————————————————————6
7

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

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References

5 Acknowledgements
Development of the troposphere-comparison database/website is supported by KONTAKTII project number LH14089. The author furthermore thanks the University of New South
Wales for hosting the February 2016 working group meeting, IGS (especially A Craddock)for providing a room for the (cancelled) December 2016 meeting, and the IGS Central
Bureau for the use of its gotomeeting.com subscription.

References
Byram, S. and C. Hackman. Computation of the IGS Final Troposphere Product by the
USNO. IGS Workshop 2012, Olstzyn, Poland, 2012.
Boehm, J., A. Niell, P. Tregoning, and H. Schuh. Global Mapping Function (GMF): A New
Empirical Mapping Function Based on Numerical Weather Model Data. GeophysicalResearch Letters, 33(7):L07304, 2006. doi: 10.1029/2005GL025546, 2006.
Dach, R., S. Lutz, P. Walser, P. Fridez. (eds. ) Bernese GNSS Software Version 5.2. (usermanual) Astronomical Institute of University of Bern, Bern, Switzerland, 2015.
Douša, J. and G. Gyõri. Database for Tropospheric Product Evaluations – Implementation
Aspects. Geoinformatics, 10:39–52, 2013.
Gyori, G. and J. Douša. GOP–TropDB Developments for Tropospheric Product Evaluation and Monitoring – Design, Functionality and Initial Results. IAG Symposia
Series, 143 (in press), Springer, 2015.
Hackman, C., G. Guerova, S. Byram, J. Douša, and U. Hugentobler. International GNSS
Service (IGS) Troposphere Products and Working Group Activities. FIG Working
Week 2015, presentation/paper #7696, Sofia, Bulgaria, May, 2015.
Noll, C. Personal Communication. NASA Goddard Space Flight Center, http://cddis.
gsfc.nasa.gov,Personal communication, 2017.
Zumberge, J.F., M.B. Heflin, D.C. Jefferson, M.M. Watkins, and F.H. Webb. Precise Point
Positioning for the Efficient and Robust Analysis of GPS Data from Large Networks.
J. Geophys. Res., 102(B3):5005–17, 1997.

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References

Appendix A. IGS Troposphere Working Group Members
Last NameFirst Name

Institution

Country

Ahmed
Amirkhani
Bar–Sever
Bevis
Bock
Boehm
BosserBosy

FurqanMohammadYoaz
Mike
Olivier
Johannes
PierreJaroslaw

Luxembourg
Iran
USA
USA
FranceAustria
FrancePoland

Braun
Byram
Byun
CaloriCao
Chen
Colosimo
Crespi
Deng
Dick
Douša
Drummond
Ghoddousi–Fard
Guerova
GutmanHackmanHeinkelmann
Herring
Hilla
HobigerJohn
SharylSung
AndreaWei
Junping
Gabriele
MattiaZhiguoGalina
Jan
Paul
Reza
Guergana
Seth
Christine
RobertTom
SteveThomasJanuth

Timon

Jones
Langley
LeandroLeighton
Liu
Melachroinos
Moeller
Moore
Negusini

JonathanRichardRodrigoJon
GeorgeStavros
GregorAngelyn
Monia

Nikolaidou
Nordman
PacionePalamartchouk
Penna

Thaleia
MaariaRosa
KirillNigel

Universite du Luxembourg
Islamic Azad Univ. Tehran
JPL
OSU
IGN–LAREG
TU Wien
ENSG/DPTS
Institute of Geodesy and Geoinformatics,
Wroclaw University ofEnvironmental and Life Sciences
UCAR
USNO
JPL
Univ. Roma, La Sapienza
Trimble Terrasat
Shanghai Astronomical Observatory
Univ. Roma, La Sapienza
Univ. Roma, La Sapienza
GFZ
GFZ
GOP
TrimbleNatural Resources Canada
Univ. Sofia
NOAA
USNO
GFZ
MIT
NGS/NOAA
Onsala Space Observatory,
Chalmers Univ. of Technology
Univ. of Applied Sciences,
Western Switzerland
Met Office UK
Univ. New Brunswick
Hemisphere GNSS
3vGeomatics
Hong Kong Polytechnic University
Geoscience Australia
TU Wien
JPL
Inst. Radioastronomy (IRA),
National Inst. Astrophysics (INAF)
Univ. New Brunswick
Finnish Geodetic Inst.
ASI/CGS
Univ. Newcastle
Univ. Newcastle

194

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

References
Perosanz
Pottiaux
PrikrylRealini

Felix
Eric
Paul
EugenioRockenRoggenbuck
Rohm
RomeroSantosSchaerSchoenSelle
SguersoSoudarin
TeferleTraceyvan der Marel
Waithaka

Chris
Ole
WitoldNacho
MarceloStefanSteffenChristina
Domenico
Laurent
NormanJeffrey
Hans
Edward Hunja

Wang
WillisXu
Zhang

Junhong
PascalZong–qiu
Shoujian

CNES
Royal Obs Belgium
Communications Research Centre, Canada
GReD – Geomatics Research& Development s.r.l.
GPS Solutions
BKG
Univ. Wroclaw
Canary Advanced Solutions
Univ. New Brunswick
AIUB
Inst. Erdmessung, Leibniz Uni Hannover
JPL
Lab. Geodesy, Geomatics, GIS; Univ. Genoa
Collecte Localisation Satellites
Universite du Luxembourg
USNO
TU Delft
Jomo Kenyatta U. of
Agriculture and Technology
UCAR/NCAR
Inst. de Physique du Globe de Paris
Liaoning TU
Wuhan Univ.

FranceBelgium
CanadaItaly
USA
Germany
PolandSpain
CanadaSwitzerland
Germany
USA
Italy
FranceLuxembourg
USA
Netherlands
Kenya
USA
France
China
China

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References

Appendix B. IGS TROPOSPHERE WORKING GROUP
CHARTER
GNSS 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 the oceans(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/land coverage
are obtained; these solutions however are discontinuous in geographic location and time.

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References
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.

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EDITORaStronomIcal InStItUte
UnIverSIty of Bern

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

International Council for Science
World Data System