TECHNICAL REPORT2015

EDITORSYOOMIN JEAN
ROLF 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 and May 2015, by Yoomin Jean, Rolf Dach (Eds.)

Technical Report 2015
IGS Central Bureau
http://www.igs.org

Editors: Y. Jean, R. Dach
Astronomical Institute, University of Bern
Published in June 2016

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 2015
ISSN: 2297-8526
ISBN: 978-3-906813-18-9 ;University of Bern, Bern Open Publishing.
DOI:
10.7892/boris.80307
Cite as:Jean, Y., Dach, R. (eds.) (2016). International GNSS Service Technical Report 2015
(IGS Annual Report). IGS Central Bureau and University of Bern; Bern Open Publishing
DOI: 10.7892/boris.80307
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 2015 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 2015.
This report is available in electronic version at
ftp://igs.org/pub/resource/pubs/2015_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

9

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

II

Analysis Centers

17

Analysis Center Coordinator

19

K. Choi

Center for Orbit Determination In Europe

25

R. Dach, S. Schaer, D. Arnold, E. Orliac, L. Prange, A. Sušknik, 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,
U. Hugentobler

Natural Resources Canada

45

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

European Space Operations Centre

51

T.A. Springer, W. Enderle, C. Garcia-Serrano, J. Feltens, I. Romero,E. Schoenemann, R. Zandbergenv

GeoForschungsZentrum

61

M. Fritsche, Z. Deng, M. Ge, T. Nischan, M. Uhlemann, G. Beeskow,
A. Brandt, M. Bradke, M. Ramatschi
Geodetic Observatory Pecný
No report submitted

Centre National d’Etudes Spatiales/Collecte Localisation Satellites

68

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

Jet Propulsion Laboratory

77

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
No report submitted

National Geodetic Survey

83

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

United States Naval Observatory

87

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

Wuhan University

95

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

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

101

SIRGAS

111

L. Sánchez

III

Data Centers

123

Infrastructure Committee

125

I. N. Romero

Crustal Dynamics Data Information System

127

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

139

Antenna Working Group141

R. Schmid

Bias and Calibration Working Group146

S. Schaer

Clock Products Working GroupM. J. Coleman

151

Data Center Working Group160

C. Noll

Ionosphere Working Group165

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 Group173

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

Reference Frame Working Group183

P. Rebischung, B. Garayt, Z. Altamimi

Real–Time Service

187

L. Agrotis, M. Caissy, A. Rülke

RINEX Working Group

191

K. MacLeod and L. Agrotis

Tide Gauge Benchmark Monitoring Project

195

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

Troposphere Working Group
C. Hackman and S. Byram

197

Part I
Executive Reports

1

IGS Governing Board
Technical Report
IGS in 2015:

The IGS Governing Board Chair Report
Gary Johnston
Geoscience Australia, Australia

1 Introduction
In June 2014, the IGS celebrated its 20th anniversary. This momentous milestone wasan opportunity to recognize the significant efforts of the IGS participants, both past andpresent, and to marvel at the outstanding improvements in products that the service hasachieved over that time. It also signaled that it was time to look forward towards our next
20 years.
In 2015, the IGS Governing Board started the process of looking forward by reviewing
its strategic plan. Issues under consideration include the scope of products and services,
appropriate acknowledgement of participants and contributors, interface with IAG and
GGOS, data and product licensing, continued GPS to GNSS transition, and new activities
around GNSS system monitoring and assessment. The new strategic plan is due forcompletion in late 2016.

2 IGS Operational Activities
Daily routine operations are the heart of the IGS. Various components of the service ensurethat tracking data and products are made publicly available every day. Approximately 500
tracking stations are maintained and operated globally, making tracking data available attime latencies spanning from daily RINEX files to real–time streams.

3

IGS Gorverning Board
The amount of IGS tracking data and products hosted by each of the four global Data
Centers on permanently accessible servers increased from 2 TB to 11 TB (135 million
files) over the last year, supported by significant additional storage capabilities provided
by Regional Data Centers.
Twelve Analysis Centers and a number of Associate Analysis Centers utilize tracking datafrom between 70 to more than 350 stations to generate precision products up to four times
per day. Product Coordinators combine these products on a continuous basis and assure
the quality of the products made available to the users.
The collective effort of the IGS produces 700 IGS final, rapid, ultra–rapid and GLONASS–
only product files, as well as 126 ionosphere files weekly. Furthermore, troposphere files
for more than 300 stations are produced on a daily basis. A total of 640 million tracking
data files (60 TB) and 110 million product files (15 TB) were downloaded in 2015 fromthe NASA Crustal Dynamics Data Information System (CDDIS), one of four IGS global
Data Centers, by more than 10,000 unique hosts – demonstrating the intense interest ofusers in IGS data and products.
The Central Bureau is operationally responsible for day–to–day management, interaction
with station operators, and answering typically some 150–200 questions and requests fromusers per month. All these activities are performed year round, on a daily basis, with highredundancy and reliability – an impressive effort that is only made possible by the strong
engagement of many individuals and the support of more than 240 institutions worldwide,in over 100 countries.

3 IGS Highlights in 2015
The following is a brief summary of key highlights in 2015:• AC coordinator:

The Governing Board has endeavored for some time to identify a new Analyses Centre Coordinator (ACC). This role has until recently been undertaken by Kevin Choi
from the US National Geodetic Survey (NGS). NGS flagged some time ago that
their support for the function needed to finish by the end of 2015. In the absence of
any other nominations Geoscience Australia, jointly with MIT, put forward a proposal for a joint ACC. This proposal identified Dr Tom Herring (MIT) as the lead
ACC, with operational support from Dr Michael Moore (GA). This proposal utilizes
Amazon Web Services (AWS) for the computing platform, and a collaborative operational model where the monitoring of combination systems is undertaken by MIT
during their working day and GA at other times. This reduces the need for 24hour/day monitoring by one individual. This proposal was subsequently accepted andendorsed by the GB.

43 IGS Highlights in 2015
The ACC software suite was subsequently installed on AWS jointly by Kevin Choiand Michael Moore. Operational transfer of the ACC functions occurred progressively through December 2015 culminating in February 2016. The Governing Board
thanks NGS for their support over an extended period in fulfilling the requirementsof the ACC role.
• MGEX experiment:

The success of the MGEX experiment has demonstrated the inevitability of a transition of the IGS to a full multi–GNSS Service. Accordingly, the Governing Board
decided to acknowledge this by terminating the “experiment” status and move MGEX
to a pilot project. Continued efforts are required to negotiate access to satellite specific information for new satellites from system providers, allowing for more realistic
models of satellite behavior to be developed and utilized by the IGS AC’s.

• Wuhan Data Center:In 2015 the Governing Board endorsed the proposal by Wuhan University to become an IGS Global Data Center. The Wuhan data center offers access to the fullcollection of IGS data and products to any user globally, especially those within the
Asia Pacific Region. Importantly the data center gives direct access to the IGS data
holdings to the very large research sector within China.

• ICG Monitoring and Assessment Joint Pilot Project:

In 2015 discussions occurred between the IGS GB and representatives from the International Committee on GNSS (ICG) concerning the establishment of joint pilot
to undertake monitoring and assessment of the GNSS constellations. This requirement has emerged from the ICG in which the IGS is an active participant. Planning
continues on how this pilot project can be constructed and managed. A call forparticipation will occur in 2016.

• Planning for the Sydney workshop:

Following the success of the Pasadena workshop, and the many that had occurred
before that, 2015 saw the planning for the Sydney workshop take shape. A fullsummary of the Sydney workshop will be included in the 2016 report.

5

IGS Gorverning Board

4 IGS Governing Board Meetings in 2015
The GB discusses the activities of the various IGS components, sets policies and monitors
the progress with respect to the agreed strategic plan and annual implementation plan.
Table 1: IGS events in 2015
Date

Event

April 12June 23
December 13

GB Business Meeting in Vienna (Sunday prior to EGU)
GB Business Meeting, during 26th IUGG/IAG General Assembly, Prague
45th GB Meeting in San Francisco (prior to AGU)

5 Communications, Advocacy, and Outreach
The IGS is represented in a variety of roles throughout the geodetic community. IGS
Governing Board and Associate Members served on the Coordinating Board, Executive
Committee, Consortium, and Science Panel of the IAG Global Geodetic Observing System(GGOS).
Members of the IGS Governing Board actively participated in the United Nations Committee of Experts on Global Geospatial Information Management (UN–GGIM), participatingin the fifth session of the UN–GGIM at UN Headquarters in New York. IGS Governing Board members involved in the UN GGIM Global Geodetic Reference Frame (GGRF)
Working Group played an active role in drafting a resolution for “A Global Geodetic Reference Frame for Sustainable Development” – the first resolution recognizing the importanceof a globally–coordinated approach to geodesy. This resolution was adopted in February
2015 by the UN General Assembly.
IGS Governing Board members also served in leadership roles in the United Nations International Committee on GNSS (ICG), including the Working Group D on Reference
Frames, Timing, and Applications, as well as Working Group A subgroup on International GNSS Monitoring and Assessment (IGMA). In this capacity, the IGS participatedin the ICG–10 meeting in November 2015 in Boulder, Colorado, USA. The IGS is also well–
represented in the International Earth Rotation and Reference Systems Service (IERS),in IAG Sub–Commission 1.2 on reference frames, in the RTCM SC104, and others.
Governing Board members continue to be actively involved in communications, advocacy,and outreach through presentations at international meetings and articles in geospatial
magazines.

66 Outlook 2016

6 Outlook 2016
The year 2016 will continue to be challenging for the IGS as the reliance on IGS products
grows, and our products are being integrated into a wide variety of scientific and societal
applications, often with very little understanding or acknowledgement of where the products come from. The collaborative nature of participation in the IGS poses resourcing
issues for many of the participants, and raises serious questions around the scope of IGS
activities. To help the GB better understand these issues and develop an appropriate
strategic plan to help manage the issues, a stakeholder questionnaire will be undertaken,
seeking input from existing members, and a broader user community on how they perceive
the IGS currently, and how that differs from the ideal. This process should be completed
by the December 2016 GB meeting.
Implementation of RINEX 3.n continues in 2016. Network operators, Data Centers andAnalysis Centers are working actively to transition data products and workflows to accommodate the new RINEX standard, a key milestone in the transition to Multi–GNSS.
Under the leadership of the Infrastructure Committee, and with significant input fromthe Network coordination team, the IGS network is being upgraded to unify the existing
GPS network with the multi–GNSS requirements. Specific efforts are also underway to
encourage participation by site operators in locations where the existing IGS network is
not optimum. In these cases, sites meeting the requirements of the IGS Site guidelines areincorporated into the network.

7

IGS Gorverning Board
Table 2: Governing Board Membership 2015
MemberAffiliation

Country

Function

Gary Johnston*
Loukis Agrotis
Zuheir Altamimi

Australia
Germany
FranceBoard Chair
Real–Time Analysis Coordinator
IAG Representative

FranceUSA
FranceBIPM/CCTF Representative
Data Center Representative
IERS Representative

Belgium

IGS Network Representative

CanadaUSA

Real–Time WG, Chair
Analysis Center Coordinator

Ruth Neilan

Geoscience Australia
ESA/ESOC
Institut Nationalde l’Information
Géographique et Forestière
BIPM
UNAVCO
Institut Nationalde l’Information
Royal Observatoryof Belgium
Natural Resources Canada
National Geodetic Survey(NOAA)
Naval Research Laboratory
Astronomical Institute,
University of Bern
Chinese Acedamey ofSurveying and Mapping
Jet Propulsion Laboratory
IGS Central Bureau, JPL
Institut Nationalde l’Information
Géographique et Forestière
United States Naval
Observatory
Technische Universität
München
JAXA
University of Warmia andMazury in Olsztyn
Natural Resources Canada
UNAVCODLR/German Space
Operations Center
IGS Central Bureau, JPL

Carey Noll
Chris Rizos*

NASA/GSFC
Univ. of New South Wales

Ignacio Romero
Laura Sanchez
Stefan Schaer

ESA/ESOC
TU Munich, DGFIFederal Office of Topography,
Swisstopo
DGFI
Deutsches GeoForschungsZentrum
ESA/ESOC
University College London

Felicitas Arias
Fran Boler
Claude Boucher
Carine Bruyninx
Mark Caissy
Kevin Choi
Michael Coleman
Rolf Dach
Yamin Dang
Shailen Desai
Steve Fisher
Bruno Garayt
Christine Hackman
Urs Hugentobler*
Satoshi Kogure
Andrzej Krankowski
Ken MacLeod
Chuck Meertens*
Oliver Montenbruck

Ralf Schmid
Tilo Schöne
Tim Springer*
Marek Ziebart* Member of IGS GB Executive Committee

8

USA
IGS Clock Product Coordinator
Switzerland Analysis Center Representative
China

Appointed

USA
USA
FranceAnalysis Center Representative
IGS Central Bureau, Secretariat
IGS Reference Frame
Coordinator

USA

Troposphere WG, Chair

GermanyJapan
PolandImmediate past chair of the GB
B
Appointed (IGS)
Ionosphere WG Chair

CanadaUSA
Germany

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

USA

Director of IGS Central Bureau
Secretary
USA
Data Center WG Chair
Australia
Appointed (IAG)
former IAG President
Germany
Infrastructure Committee Chair
Germany
IGS Network Representative
Switzerland Bias and Calibration WG Chair
Germany
Germany

Antenna WG Chair
TIGA WG Chair

Germany
UK

Analysis Center Representative
Space Vehicle Orbit Dynamics
WG ChairIGS Central Bureau
Technical Report 2015
R. Neilan1∗, S. Fisher1 , G. Walia1 ,D. Maggert2 , A. Craddock1
1
2

Caltech/JPL
UNAVCO

1 Introduction
The Central Bureau’s (CB) mission is to provide a continuity of management and technology to sustain the IGS in perpetuity. It functions as the executive office of the service andis responsive to the IGS Governing Board in carrying out its directives and decisions. The
CB coordinates the IGS tracking network and operates CB 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 its diverse global user community. The
CB office is hosted at the California Institute of Technology/Jet Propulsion Laboratory,
Pasadena, California, USA. It is funded principally by the US National Aeronautics andSpace Administration (NASA), which generously contributes significant staff, resources
and coordination to advance the IGS. The following report highlights progress made by
the Central Bureau in 2015.

2 Executive Management and Governing Board Participation
Governing Board meetings were held in April (Vienna), June (Prague) and December (SanFrancisco) 2015. The Executive Committee met additionally by teleconference approximately every other month. CB staff followed–up throughout the year by implementing
actions defined by the GB to carry out the business of the service.
∗

Director

9

IGS Central Bureau
A biennial review of the IGS Associates (defined as those individuals who contribute asignificant effort to the IGS) was conducted by the Associate Member Committee with
CB support in 2015. The number of IGS Associates grew by 63 members to 337 since
the last review in 2013. Those members represent 118 countries vs. 90 in 2013. The IGS
Associates form the body of voters who elect the Governing Board.
The CB supported the Elections Committee in conducting the December Governing Board
election where two Analysis Representatives were elected to replace members whose terms
expired at the end of the year. Of 4 candidates who stood for the election, M. Fritscheand S. Desai received most of the Associate Member votes. Their 4–year terms started on
January 1 2016. The Associate Member and Governing Board Member lists are maintainedon the IGS website (http://igs.org/about/organization).

3 Strategic Plan/Progress
Formal benchmarking of progress made in advancing the IGS mission has continued forthree years in a row. 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 this period to exceed the targeted
product availability, which is our most important measure of success. In addition, metrics
related to the growth of IGS participants, users, competencies and external influence alltrended favorably, though devoting more effort to sustain the IGS funding has consistently
been identified as an area for future improvement.
The 2017–2021 strategic plan development cycle was kicked–off just before the December
Governing Board Meeting where a meeting was held to establish a work plan and timeline
for writing the new strategic plan. A review of the current plan found it still to be
relevant and that the new plan would rely on it as a basis for incremental improvement.
The planning group suggested after considerable discussion and analysis that broader user
input would be desirable in identifying future opportunities for IGS. This input is to besolicited through a survey questionnaire form to be broadly circulated in the first part of2016.

4 Network Coordination
The 49 MGEX stations that that fully meet IGS requirements were elevated to full status
in 2015. An additional 30 other proposed stations were also reviewed and accepted following a strict vetting process involving the CB/Network Coordinator and Infrastructure
Committee Chairman. 38 stations that were either replaced with new stations, failed toprovide data to IGS standards, or ceased operation were decommissioned during the year.
In net, the number of IGS stations has increased by 53 to 491 total stations through 2015.

10

5 Web Development and IT Support

Figure 1: Network map from www.igs.org/network.

Of these, 127 are capable of multi-GNSS tracking and 118 stream observation data to
support real–time applications.

5 Web Development and IT Support
In addition to administering and generally supporting the CBIS operation, we have carriedforward the move of all of the CB processes external cloud hosted servers to allow global
access. Disaster recovery procedures were reviewed and we’re now in process of implementing new backup and restore procedures in conjunction with UNAVCO. The Website
has been more actively updated with events, news and current information than in previous years. Our web access metrics show that the newer content is attracting users to
the IGS website, as is our presence on social media platforms. Development of the Site
Log Manager (SLM) database application was substantially completed by April, though
incremental improvements have continued to be made based on user feedback. The SLM
was introduced to IGS station operators in May with 77 new users adopting it for IGS site
metadata management during the year. Some assistance has been provided to the ACC
transition with requirements definition and minor IT tasks to aid in the transition of the
IGS combination software to cloud based servers. A summary of progress on a number of
IT tasks can be seen in Tab. 1.

11

IGS Central Bureau
Table 1: Progress on web and IT activities
Task or component

Progress

IGS.org/mgex

added - content reference 1.5
added - Product Comparisons Section
added - SLM powered network page
resolved - support numerous requests
Network 1.5 update
added - link access to all networks
resolved - support numerous requests
added - Workflow - Impact on Strategic Objectives
added - Workflow - IGS Component Summary Report
added - Workflow - Requests - http://connect.igs.org/request
added - https over entire Site
resolved - JPL disallow access to the site server
support and administration
added - no effort upload and generation of website for meetings
dreamhost host migration of dependent services igscb administration
resolve downtime (4–10 times)
server move / re–movesecurity ticket resolution
mailman administration Support
server documentation
support and administration
development management with UNAVCO
metadata workshop contribution
user support – introduce SLM to 77 new users
server support and administration
support ticket resolution 400 tickets
renewal of http://kb.igs.org service
server support and administration
ACC server requirements discovery
website coordination
mailing list and support for DNS
web content updates
caster operation and administration
user registration and support
server support and administration
added - version .5 of Content Management System
Migrating operational cron jobs from JPL to cloud server(Migrating remaining web content from old server)
eliminating old server dependencies
Planning mail list transition to cloudspecified backup and restore requirements across all servers
working cooperatively with UNAVCO

IGS.org/network

connect.igs.org

upload.igs.org
IGSCB.jpl.nasa.gov

slm.igs.org

kb.igs.org

igs.org/analysis

rts.igs.org

CMS
CBIS cloud migration

Disaster recovery

128 External Participation

6 Project Support, Committee and Working Group
Participation
The CB’s participation within the IGS Working Groups and Projects was limited in 2015.
Principally, high priority and essential maintenance activities were addressed, such as:• preparing site metadata systems for RINEX 3 adoption,• integrating MGEX stations within the IGS network,• maintaining a Real–time caster and minimally supporting the Real–time Service
IOC operation,• helping the Antenna Working Group with maintaining the IGS equipment files,• handling specific needs during the ACC transfer to Geoscience Australia,• participating in the site metadata Workshop and subsequent discussions,• and supporting related working group web content.

In addition, the CB and IC Chairman met by teleconference roughly once per month ona range of station and infrastructure management issues.

7 IGS User Support
The CB expend considerable effort on IGS community and user technical support. As
measure of this, the CB tracks email traffic through the CB mail list. This traffic has
increased by 10% in 2015 to about 3300 messages, though much of the increase is fromnotification emails from various CBIS processes that do not require response. Increasingly
over the last year we have steered many of the user support inquiries received throughthe web into a support trouble ticketing system. With 2015 being its first full year ofoperation, the system tracked over 400 support issues that were resolved through theyear. This coupled with the IGS knowledge base is relieving some of the email–based
support that the CB has historically provided.

8 External Participation
The CB has continued to extensively interact with many IGS stakeholders. In 2015, these
efforts were highlighted by UN–GGIM working group activities, particularly adoption of
the resolution for the GGRF, which is anticipated to open additional avenues for international cooperation for IGS and geodesy in general (http://ggim.un.org/UN_GGIM_wg1.
html). Significant progress was also made in developing a cooperative plan with the ICG

13

IGS Central Bureau
to monitor performance and interoperability metrics between the different GNSSs, whichis expected to take the form of a joint working group between ICG and IGS beginningin 2016. The CB Director and staff members have continued representing the IGS within
the IAG services committees and boards, including R. Neilan on the GGOS Coordinating Board and Executive Committee, and S. Fisher as the IGS Network Representative
to the IERS Directing Board. R. Neilan has also maintained her appointment as NASA
representative to the US PNT Coordination office (pnt.gov). Tab. 2 provides a listing of
the principal external meetings attended by CB staff during 2015.

Table 2: Principal meetings attended by CB staff and role/outcomes
Meeting

Month

Venue

Role/OutcomesNASA HQ Programmatic Interactions

Jan.

Washington DC

Programmatic meetings at
NASA HQ with ESIP Partners
and WDS representatives

ICG strategic directions meeting

Mar.

MunichRepresent IGS on WG–Dand IGMA activities

ICSU World Data System

Mar.

San Diego

Represent IGS on WDS
scientific committee meetings

Governing Board Business Meeting

Apr.

ViennaDiscussion on “IGS 2.0”
a new paradigm to support
IGS’s ever–increasing growthNASA HQ Programmatic Interactions

May

Washington DC

NASA/SGP strategy meeting

United Nations Global Geographic
Information WG

Sep.

New York

Adoption of Resolution for
Global Geodetic Reference Systemfor economic development

Programmatic Interactions with INPE, Sep.
Brazil

Sao Paulo

Meetings on NASA/INPE cooperationin developing space geodetic capabilities

GGOS Meta Data Workshop

Oct.

Boulder

Initiated development of geodetic
metadata standard

GGOS Days

Oct.

Frankfurt

Board and committee representation

International Committee on GNSS
10th Meeting

Nov.

Boulder

Supported local meeting planning
IGMA proposal to IGS was developed

PNT Advisory Board

Nov.

Boulder

Ongoing Board participation

IERS DB Meeting

Dec.

San Francisco

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

Governing Board Meeting

Dec.

San Francisco

Two AC representatives elected to GB
New ACC transition plan accepted
2017–2021 Strategic planning cycle initiatedVideo–conference

Ongoing IGS business

Monthly GB Exec. Committee

14

Monthly9 Publications

9 Publications• 2015 IGS Performance Dashboard, IGS website• IGS 2014 Technical Report section, IGS website• NASA SGP/ICPO annual progress report, NASA internal publication

15

IGS Central Bureau

16Part II
Analysis Centers

17

Analysis Center Coordinator
Technical Report 2015
K. Choi
NOAA National Geodetic Survey
1315 East–West Highway
Silver Spring, Maryland, USA
E–mail: igs.acc@noaa.gov/acc@igs.org

1 Introduction
In 2015, IGS core products were combined and distributed in a timely manner over 99%
of the time. To ensure continued production of high–quality IGS products, the Analysis
Center Coordinator (ACC) performed high–level oversight and quality control of Analysis
Center (AC) products, combination performance, and maintenance of the ACC website
with updated plots. Also coordinated among ACs to assimilate changes made by themand to ensure that the best analysis models and procedures are used, along with coordination among the other relevant IGS components, preparation of component reports, andcoordination of the IGS 2nd reprocessing campaign. IGS has contributed to the ITRF2014
by providing station coordinates and EOP values.

2 Product Quality and Reliability
With the exception of a few unusual delays, delivery of all IGS products was generally
uninterrupted. IGV (IGS Ultra–rapid GNSS products) still remains as experiment status
due to lack of contributing ACs as a stable production. Currently, only four ACs are
submitting the orbit solutions regularly but only three of them provide the GNSS clocks.
More GNSS clock centers are desirable.
Sporadic errors in the GLONASS broadcast files have caused delays in the Final GLONASS
products. IGS data centers rely on the quality of the broadcast files from each station.

19

IGS Analysis Center Coordinator
Table 1: IGS core product series with latency, issue times and data spans
SeriesID

Latency

Issue times(UTC)

Data spans(UTC)

Remarks

Ultra–Rapid(observed half)

IGA

3–9 hr@ 03:00, 09:00,
15:00, 21:00–24 hr@ 00:00, 06:00,
12:00, 18:00• for near real–time apps
• GPS & GLONASS• issued with following IGU

Ultra–Rapid(predicted half)IGU

real–time@ 03:00, 09:00,
15:00, 21:00+24 hr@ 00:00, 06:00,
12:00, 18:00• for real–time apps
• GPS & GLONASS• issued with prior IGA

Rapid

IGR

17 – 41 hr@ 17:00 daily±12 hr@ 12:00• for near–definitive, rapid apps
• GPS only

Final

IGS

12 – 19 d

weekly each
Thursday/Friday±12 hr@ 12:00 for 7 d• for definitive apps
• GPS & GLONASS

2.1 Combined orbit quality
Inter–AC agreement of the Final orbit products is ∼5 mm with precision ranges 3–4
mm (1D error). Due to Repro2 ACs switched their operation to match with the Repro2
strategies around the week 1820, inter–AC agreement has been improved to ∼5 mm with
precision ranges 3–4 mm (1D error).
WRMS differences between the full–weight ACs and the zero–weight ACs became more
distinctive in the Rapid solutions.

2.2 Events Impacting Product Quality and Reliability• In Jan–Feb, GFZ had fixed the issues with the SV DCBs

• In early March, MIT Final clocks are set to be comparison only.
• Network outage at the NRL facility:– [IGSMAIL–7060] Ultra–rapid product was delayed 5.5 h– [IGSMAIL–7064] IGU1835_6–12 and 18, IGR wk1834_5 delayed until 21:35[UTC]• GOU temporarily stopped Ultra–rapid contribution since wk1854–4 06h. – after
break down trying to update the software but having lack of resources.
• Minor issues:

2015–03–10
2015–07–21
2015–08–03

20

Beginning 1835_1, NGS and GFZ Rapid Polar motion and LOD is back in the combination.
IGV reference clock is switched from GFZ to EMR due to missing GFZ submission since igv18541_18.
wk1856–0 COD starts GPS/GLO clock for Rapid

2 Product Quality and Reliability

Figure 1: Weighted RMS for the Final orbit combinations for recent weeks.

Figure 2: Weighted RMS for the Rapid orbit combinations for recent weeks.

21

IGS Analysis Center Coordinator

2.3 New Analysis Center Coordinator
Since July 2015, NOAA/NGS has been working with Geoscience Australia (GA) and
Massachusetts Institute of Technology (MIT) for the Analysis Center Coordinator (ACC)
duty transition at the end of 2015. We plan to implement two new changes: Placing
combination server on the Cloud (Amazon EC2 service), and splitting duties into twotime zones (US Eastern time and Australian standard time). We’ve remotely worked to
set up the server environment and preliminary testing for 3 months and had intensive
on–the–job training in Geoscience Australia for 3 weeks in November 2015. In order toreduce the internet connection latency, we’ve decided to use the Cloud service based on
Frankfurt, Germany as a primary server and use Sydney–based service as an emergency
back–up. Parallel combination has been started in week 1868 and generating results thatare fully consistent with the current operational combination server.
Actual transition of duty will happen in January 2016 although the current NGS combination server will still be running in the background for another month to ensure thecontinuity of operation.
For users and analysis centers, there should be no apparent changes after the transition.
The ACC Email is switched to acc@igs.org and igs.acc@noaa.gov will be decommissioned in the near future. All the products are available from and deposited to the same
locations as currently. While it is expected that the transition should happen transparently, there could be some delays as the new team works through any problems that doarise.

2.4 Recommendations
For the stable UTCk clock processing, Mike Coleman (NRL) recommended for the ACs
to include important sites for their clock processing. Below lists are available in http://acc.igs.org.
• UTCk Reference Clock Stations: Preferred to have at all times both in IGS and IGR(in the order of importance) – http://acc.igs.org/utck_ref_clk.list– PTBB, USN7, OPMT, IENG, BJNM, SPT0, SFER, WAB2, NIST, TWTF,
NRC1, NRL1
• Non UTCk stations but very stable clocks: – http://acc.igs.org/non_utck_clk.
list– YELL, PIE1, WSRT, HERS, PRDS, HRAO, WTZR, KOUR, GODE, STJO,
KOKB, KOKV, MKEA

22

4 ACC Activities Planned for 2016

3 Publications and Meeting Presentations
This section highlights a selection of papers and presentations in 2015 that are relevantto the quality of the IGS products. Download is available at http://acc.igs.org.
• Preliminary Analysis of IGS 2nd Reprocessed Orbits (2015)

K. Choi, a poster presentation at the 2015 European Geosciences Union• Combination of the IGS repro2 Terrestrial Frames (2015)

P. Rebischung et al., a poster presentation at the 2015 European Geosciences
Union• Impacts of GNSS Position Offsets on Global Frame Stability (2015)

J. Griffiths and J. Ray, a presentation at the 2015 European Geosciences Union
Meeting• The IGS Contribution to ITRF2014 (2015)

P. Rebischung, B. Garayt, Z. Altamimi, X. Collilieux, a presentation at the 26th
IUGG General Assembly, Prague, 28 June 2015

4 ACC Activities Planned for 2016
• Maintain existing products, as usual.

• ACC server/duty transfer will be completed in January.
• Smooth ACC duty transition• Completing Repro2 Orbit and Clock combination• Implementation of ITRF2014 (IGS14)

23

IGS Analysis Center Coordinator

24

CODE Analysis Center
Technical Report 2015
R. Dach1 , S. Schaer2 ,D. Arnold1 , E. Orliac1 , L. Prange1 , A. Sušknik1 , A. Villiger1 ,A. Maier1 , L. Mervarta , A. Jäggi1 , G. Beutler1 ,E. Brockmann2 , D. Ineichen2 , S. Lutz2 , A. Wiget2 ,A. Rülke3 , D. Thaller3 , H. Habrich3 , W. Söhne3 , J. Ihde3 ,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 for 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 for 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 typically carried out at IAPG, TUM. All solutions and products are generated
with the latest development version of the Bernese GNSS Software (Dach et al. 2015a).
aInstitute of Geodesy, Czech Technical University in Prague, Czech Republic

25

CODE Analysis Center

2 CODE products available to the public
A wide range of GNSS solutions based on a rigorously combined GPS/GLONASS dataprocessing scheme is computed at CODE. The products are made available through anonymous ftp at:
ftp://ftp.unibe.ch/aiub/CODE/ or http://www.aiub.unibe.ch/download/CODE/
An overview of the files is given in Tab. 1.
Within the table the following abbreviations are used: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 in Tab. 2.
The network used by CODE for the final processing is shown in Fig. 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:

GNSS
GPS only
Figure 1: Network used for the GNSS final processing at CODE by the end of 2015.

26

2 CODE products available to the public• Dach, Rolf; Schaer, Stefan; Arnold, Daniel; Orliac, Etienne; Prange, Lars; Sušnik,Andreja; Villiger, Arturo; Jäggi, Adrian (2016). CODE final product series for
the IGS. Published by Astronomical Institute, University of Bern. URL: http://www.aiub.unibe.ch/download/CODE; DOI: 10.7892/boris.75876 .
• Dach, Rolf; Schaer, Stefan; Arnold, Daniel; Orliac, Etienne; Prange, Lars; Sušnik,Andreja; Villiger, Arturo; Jäggi, Adrian (2016). CODE rapid product series for
the IGS. Published by Astronomical Institute, University of Bern. URL: http://www.aiub.unibe.ch/download/CODE; DOI: 10.7892/boris.75854 .
• Dach, Rolf; Schaer, Stefan; Arnold, Daniel; Orliac, Etienne; Prange, Lars; Sušnik,Andreja; Villiger, Arturo; Jäggi, Adrian (2016). CODE ultra-rapid product series

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 used

27

CODE Analysis Center

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.

28

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 Tab. 1.

29

CODE Analysis Center
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

for the IGS. Published by Astronomical Institute, University of Bern. URL: http://www.aiub.unibe.ch/download/CODE; DOI: 10.7892/boris.75676 .
• Prange, Lars; Orliac, Etienne; Dach, Rolf; Schaer, Stefan; Arnold, Daniel; Jäggi,Adrian (2016). CODE product series for the IGS MGEX project. Published byAstronomical Institute, 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. Published by Astronomical Institute, University 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. 2015b.
In Sect. 3.1 we give an overview of important development steps in the year 2015. Section 3.2 describes the introduction of the extended Empirical CODE orbit model (ECOM)
and Section 3.3 provides details on the extension of the clock rapid product at CODE .

3.1 Overview of changes in the processing scheme in 2015
Table 3 gives an overview of the major changes implemented during the year 2015. Details
on the analysis strategy can be found in the IGS analysis questionnaire at the IGS Central
Bureau (ftp://igscb.jpl.nasa.gov/igscb/center/analysis/code.acn).
Several other improvements not listed in Tab. 3 were implemented, too. Those mainly
concern data download and management, sophistication of CODE’s analysis strategy,
software changes (improvements), and many more. As these changes are virtually not
relevant for users of CODE products, they will not be detailed on any further.

30

3 Changes in the daily processing for the IGS
Table 3: Selected modifications of the CODE processing over 2015
Date

DoY/Year

Description

04-Jan-2015

004/2015

09-Feb-2015

040/2015

15-Feb-2015

046/2015

15-Feb-2015

046/2015

19-Feb-2015

050/2015

27-Febr-2015
24-Apr-2015

058/2015
115/2015

28-Jun-2015

179/2015

01-Jul-2015
20-Jul-2015

182/2015
201/2015

21-Jul-2015

202/2015

Extended ECOM as described in Arnold et al. 2015 has been
activated in the final, rapid and ultra-rapid processing scheme byadding the twice- and four times-per revolution terms in
D-component
Include a completeness check for RINEX observation files that areused for the rapid or ultra-rapid processing
Switch from IGRF11 to IGRF12 Tébault et al. 2015 for computing
the higher-order ionosphere (HOI) corrections
Correct a software bug that may extract VMF1 coefficients andatmosphere pressure loading corrections from an extrapolation tooutside a cell in the grid file instead of interpolating within grid cells.
Whether the problem occurred or not depends on the baseline andnetwork configuration. An effect is more likely if dense regional
networks instead of global networks are processed; but a limited
number of examples have also been found in the operational andrepro2 series for the IGS.
Update the Bernese GNSS Software to allow for filenames longer
than 32 characters
Relax some screening criteria in the data preprocessing
Earth rotation parameters are set up per orbital plane and geocenterparameters per satellite for internal purposes when generating thenormal equations in the final processing chain. These parameters arestacked to one global set of parameters over all satellites when
computing the solutions submitted to the IGS
Disable the four times per revolution terms in the new ECOM
because they degrade some of the GLONASS orbits
Add the leap second
Request at least 8 hours between a stochastic pulse for GNSS
satellite orbit modelling and a repositioning event, otherwise thepulse is removed
A new version of download script was activated in order to support
RINEX3 files with long filenames. This includes a priority selection
for several RINEX files from the same station:
1. RINEX3 file created by the receiver
2. RINEX3 file created from streamed data
3. RINEX3 file with unknown source or short filenames
4. RINEX2 files

03-Aug-2015

214/2015

27-Aug-2015

112–239/2015

14-Sep-2015

214–255/2015

A new multi-GNSS procedure to generate the clock corrections in the
rapid chain was activated considering GPS and GLONASS at the
moment.
The RMS for the linear fit of the estimated clock corrections forstation BRAZ was significantly higher for the 5 s clock solution(based on streamed data) than in the 30 s solution (based on legacy
RINEX data). The effect on the ultra-high-rate satellite clock
corrections is unclear.
In the new clock generation procedure for the rapid, observations
that have not passed the residual screening procedure may have beenused for the final parameter estimation. The Problem was fixed.

31

CODE Analysis Center

3.2 Introducing the extended ECOMThe Empirical CODE Orbit Model (ECOM, Beutler et al. 1994) was developed in theearly 1990s, motivated by the lack of reliable satellite information. It is widely used in the
IGS and allows for a successful modeling of non-gravitational accelerations — especiallyinduced by solar radiation pressure — acting on GPS satellites.
The ECOM decomposes the perturbing accelerations into three orthogonal directions of aSun-oriented coordinate system in the center of mass of the satellite, namely a D component oriented from the satellite to the Sun, a Y component pointing along the satellite’ssolar panel axes, and a B component to complete the orthogonal system. In the original
ECOM the functions D(u), Y (u) and B(u) are represented as Fourier series truncated after
the once-per-revolution (1pr) terms, whereas Springer et al. 1999 proposed the so-called
reduced ECOM,
D(u) = D0
Y (u) = Y0

(1)

B(u) = B0 + Bc cos u + Bs sin u ,where u is the argument of latitude for the satellite. It was used for the IGS contributionsof CODE for a long time. Arnold et al. 2015 proposed an extension of the ECOM accordingto:D(u) = D0 +nD
X

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

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

i=1

(2)

.
where ∆u = u − us and us is the argument of latitude of the Sun. The extended ECOM
thus contains even-order periodic terms in ~eD -direction and odd-order periodic terms in~eB -direction.
Starting with GPS week 1826 (January 04, 2015), CODE started to use the extended
model with nB = 1 and nD = 2 (resulting in 2pr and 4pr terms according to Equation 2) .
Although Arnold et al. 2015 have demonstrated the advantages of the new with respect
to the old ECOM, the introduction of the new model has led to a reduction of consistency
with the other IGS ACs (see Fig. 2).
Unfortunately, some of the (older) GLONASS satellites did show a degradation due tothe additional terms. The relations between the cosine and sine terms and between thetwice and four-times per revolution terms did not agree with the expected magnitudes
in Arnold et al. 2015. Obviously, the higher-order terms do amplify other not modelled
effects on the satellites. For that reason the 4pr D-terms of the extended ECOM were32

↓
3 Changes in the daily processing for the IGS

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
1820

1830

1840

1850

1860

1870

Time [GPS weeks]

1880

Geoscience Australia/MIT, 30.01.2016 20:16 (GMT)

Figure 2: Consistency of the GPS final orbits among the IGS analysis centers during the recent
weeks (from http://acc.igs.org/media/Gmt_sum_final_all_orb_smooth.ps.

B1+D2, 2012-2014, SVN=746, R17
300

200

200

100

100

Residual [mm]Residual [mm]B1+D2+D4, 2012-2014, SVN=746, R17
300

0

0

-100

-100

-200

-200

-300
-90

-45

0

solar beta angle

45

90

-300
-90

-45

0

45

90

solar beta angle

Figure 3: SLR residuals to GLONASS satellite R17 (SVN 746).

33

CODE Analysis Center
deactivated starting from GPS week 1851 (June 28th, 2015). The benefit can be seen in
the SLR residuals displayed in Fig. 3 for one of the affected GLONASS satellites.

3.3 Extending the CODE rapid clock productFor the CODE clock product, GNSS satellite orbits, Earth rotation parameters (ERPs)
and station coordinates are introduced as known from the double-difference solution. Figure 4 illustrates the processing flow to generate the GPS/GLONASS rapid clock corrections. The procedure is executed two times per day: once for the early and a second time
for the final rapid solution (see Dach et al. 2015b).
After some general preparatory steps described in the violet boxes in Fig. 4 (steps
1.1 and 1.2), the independent preprocessing of the code and phase measurements
is initiated. In the green chain (steps 2.1
to 2.4), the pseudorange data are preprocessed. This includes apart from a residual
screening also the computation of stationspecific weights because of the different
noise level of the individual stations due tothe different environmental conditions andreceiver/firmware behavior. Furthermore,
the inter-system and inter-frequency biases
are computed for all stations.
In parallel the preprocessing of the phasemeasurements takes place following thesteps described in the brown boxes (steps
3.1 and 3.2) including the cycle slip andoutlier detection as well as the update of
the list of ambiguities. For this step satellite clock corrections are needed that arecomputed from a limited subset of the stations that offer a global coverage.

1.1

1.2

2.1

2.2

Import of observations from RINEX
Receiver clock synchronization
to GPS system time
Code smoothing
using the corresp.
phase mea.
Compute weightsof the code
measurements

2.3

Screening of
post-fit residuals,
code sol. in 6 clust.

2.4

Compute intersystem, inter-freq.
biases (ISB/IFB)

3.1

Compute satellite
clock corrections
from epoch-diff.
of the phasemeasurements fromabout 35 stations

3.2

Station-wise preprocessing of phasemeasurements:
cycle slip detection,
outlier rejection andambiguity update

4.1

Screening of post-fit residuals from a
combined code and phase solution with asampling of 300 seconds in 12 sub-networks(ISB/IFB from 2.4 are introduced)

4.2

Computation of the clock corrections
from combined code and phase solution with asampling of 300 seconds in 3 global clusters(ISB/IFB from 2.4 are introduced)

4.3

Combining the clock corr. from 4.2(including reference clock selection)

After cleaning the pseudorange and phase
Densification from 300 to 30 seconds byinterpolation using the phase measurements
measurements in the two separate chains,
they need to be processed first together
in a further preprocessing step to make Figure 4: Flow chart of the GPS/GLONASS
rapid clock product generation.
sure that the full consistency is given (anoverview on potential receiver events isgiven, e.g., in Dach et al. 2006).
4.4

34

4 CODE contribution to the IGS–MGEX campaign
Now the observations are prepared to compute the clock corrections. The stations are
divided into three clusters that are analysed in parallel with a sampling of 5 minutes
where also the biases from processing step 2.4 are introduced as known. In a subsequent
step the clock corrections of the three clusters are combined and the reference clock forthe solution submitted to the IGS is selected. The densification from 300 to 30 seconds
is done according to the phase-based interpolation procedure as described in Bock et al.
2009.

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,GLONASS, 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 like diverse biases for the receivers, ERPs, station coordinates, and troposphereparameters. A more detailed description is given in Prange et al. 2016b.
During the year 2015 the following updates have been introduced in the processing scheme:• Since January 2015 the MGEX solution is regularly computed and posted to the
product file area at CDDIS:
ftp://cddis.gsfc.nasa.gov/gnss/products/mgex
as well as since beginning of 2016 also to the anonymous ftp server of AIUB:
ftp://ftp.unibe.ch/aiub/CODE_MGEX/CODE
The list of products is given in Table 4.
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
format35

CODE Analysis Center• Since January 2015 the extended ECOM (Arnold et al. 2015) is used for Solarradiation pressure modelling in the MGEX product generation including the 2prand 4pr terms in the D direction (nD = 2 in Equation 2).
As in the operational processing, the 4pr terms in the D direction are skipped sinceday 251 of year 2015 (08-Sep-2015).
Figure 5 confirms the positive impact of the new orbit model (green dots, label
ECOM 2) over the traditional one (black dots with label ECOM 1). For the Galileo
and the QZSS satellites the RMS of a linear fit of the epoch-wise independently
estimated satellite clock corrections are shown. As long as the satellites are flying
in the yaw-steering mode there is a clear reduction of the dependency of the orbit
quality parameter from the elevation of the Sun above the orbital plane (beta angle).
In the gray shaded areas, the QZSS satellite is switched to the so-called orbit normal
mode where the ECOM decomposition as introduced by Beutler et al. 1994 is notdesigned for. An adaptation is currently under development.
• Since August 2015 the observations from QZSS and BeiDou satellites, that comeclose to the beta angle where the attitude mode of the satellite is changed, areintroduced with a very low weight. In this way, the mis-modelling of the Solarradiation pressure cannot degrade the solution and the orbits of other satellites.
Based on the MGEX solution, CODE has also contributed to a comparison and validationof estimated satellite antenna phase center offsets for Galileo satellites (Steigenberger et al.
2015).

Galileo IOVECOM 1ECOM 2

RMS of linear clock fit [ns]RMS of linear clock fit [ns]

3.0

0.50

0.25

0.00
−90

−45

0
Beta [deg]4590(a) Galileo IOV satellites, except of E20(SVN 104)

QZS-1 J001

ECOM 1ECOM 2

90
2.0
60
1.0
30

0.0

Absolute value of Beta [deg]

0.75

0
100

200
DOY 2014

300(b) QZSS satellite J001 (QZS–1)

Figure 5: RMS of daily linear fit through estimated epoch-wise satellite clocks as a function of
the beta angle.

36

6 CODE contribution to the EGSIEM reprocessing

5 Influence of the length of the orbit arc on GNSS results
Based on the reprocessing series computed in the year 2013 (see Dach et al. 2014) – thecontribution of CODE to the IGS repro2 effort – detailed investigations on the influenceof the orbit arc length on several products have been carried out. In this context theclean one day and three day long arc solutions (that are also regularly computed by the
CODE AC in the operational final processing chain) were evaluated. Because the IGS isrequesting daily coordinate solutions (for correcting the loading effect on solution level)and daily independent polar motion parameters, an additional special long arc solution has
been generated where only continuity conditions were applied to the orbit parameters.
The detailed analysis can be found in Lutz et al. 2016. The improvement of the estimatedpolar motion rates when increasing the arc length from one day (red) to three days (blue) isa highlight of the article (see Fig. 6). On the one hand, the reduced number of independent
sets of polar motion parameters in the three day long arc solution due to the continuity
conditions results in the best agreement to the C04 series. On the other hand, the clean
one day solutions show a significant deviation with periods of one and half a year. With
the increasing influence of GLONASS (from top to bottom) also a third of a year period
becomes relevant for the clean one day solutions.
The special long arc solution with only applying continuity conditions on the orbit parameters reduces the amplitudes of the annual and biannual periods in the differences
to the C04 series by a factor of two with respect to the clean one day solutions. It isremarkable that particularly the periods at a third of a year that are introduced by theincreasing number of GLONASS satellites in the clean one day solution are nearly completely removed. Lutz et al. 2016 also studied the properties of non-overlapping 3-day
solutions. The polar motion rates of such solutions are close in quality to those of theclassic overlapping 3-day solutions. This corresponds to the observation that longer arcs
improve the robustness of the orbit estimates more for GLONASS than for GPS satellites(e.g., in terms of discontinuities at the day boundaries in the celestial frame by a factorof 2 for GPS but 3.5 for GLONASS).

6 CODE contribution to the EGSIEM reprocessing
In the framework of the European Gravity Service for Improved Emergency Management(EGSIEM) project, monthly gravity field solutions derived from the Gravity Recovery
and Climate Experiment (GRACE) mission will be combined. Since a consistent reference frame is a prerequisite for precise orbit and related gravity field determination, a
reprocessing campaign was initiated at AIUB (subsequently labelled as repro15). To get a
consistent series of GNSS satellite clock corrections, GNSS orbits, Earth rotation parameters, and station coordinates, more than 250 globally distributed tracking stations of the
IGS network are homogeneously reprocessed for the interval between 2003 to the end of2014 following the processing standards from the CODE analysis center by March 2015.
37

CODE Analysis Center

140
Years: 2000–2008
Amplitude (µas/d)

120

dominated by GPS,even if GLONASS wasincluded since 2002

100
80
60
40
20
0
2

3

5 7 1020 30

50

100 182.6 365.25

Period (days)
140
Years: 2009–2011
Amplitude (µas/d)

120

rapidly growing impactof GLONASS

100
80
60
40
20
0
2

3

5 7 1020 30

50

100 182.6 365.25

Period (days)
140
Years: 2012–2013
Amplitude (µas/d)120

strong impact of GLONASS:
full satellite constellation

100
80
60
40
20
0
2

3

5 7 1020 30

50

100 182.6 365.25

Period (days)

Figure 6: Amplitude spectra of polar motion rate ẋ differences between the C04 series and the
combined GPS/GLONASS solutions: clean one day solution (red), three day long arc
solution (blue), and special long arc solution (green).

38

6 CODE contribution to the EGSIEM reprocessing
Even if the POD for GRACE will only base on GPS satellites, the reprocessing activity
considered GPS and GLONASS measurements.
In order to provide within the EGSIEM project reference frame products using latest
GNSS orbit modelling effort, reprocessing of the GNSS data was performed using theextended Empirical CODE orbit model (Arnold et al. 2015), which significantly improves
the accuracy of the GNSS orbits (in particular for the GLONASS satellites) and reduces the
deficiencies in the geodynamical parameters. Since the reference frame for the most recent
reprocessing is still IGb08 the same station selection as in IGS-repro2 from CODE wasreused for the repro15 effort. The processing starts from the original GNSS observationsin the RINEX files. As a priori orbit information the results from the repro2 campaign for
the IGS was used and completed by alternative sources (e.g., broadcast orbits) in order toinclude as many satellites into the processing as possible. This effort resulted in a bigger
number of satellites for the repro15 series when comparing with the number of satellites
in the result files of the 1-day solutions of repro2 (see Fig. 7).
Since all GLONASS and two GPS satellites are equipped with retro-reflector arrays, SLR
provides an independent tool to validate microwave-based GNSS orbits. Because themaximum angle of incidence of a laser pulse to a GNSS satellite does not exceed 14◦ , SLR
residuals indicate mainly the radial accuracy of microwave-based GNSS orbits (Sośnica
et al. 2014; Fritsche et al. 2014; Maier et al. 2015). Figure 8 shows SLR residuals w.r.t. the1-day GLONASS-M orbits – once using the old ECOM (repro2, left side) and once using
the extended ECOM (repro15, right side). When the old ECOM model is used (left plot ofFig. 8), there is a clear dependency of the SLR residuals on the elongation angle: whereas
the residuals to the satellite positions near solar beta angle 90◦ are scattered around zero,
those to satellite positions of smaller absolute solar beta angle show a significant offset tozero. The dependency of the SLR residuals on the elongation angle is significantly reduced

Figure 7: Number of GNSS satellites available in 1-day orbits for the period between 2000 and2013. Red color represents repro15 and green repro2.

39

CODE Analysis Center

Figure 8: SLR residuals w.r.t. GLONASS-M orbits using the original ECOM (left) and theextended ECOM (right). Mean value (ν) and standard deviation (σ) are based on all
residuals whose absolute value is smaller than 150 mm. Observations to four GLONASS
satellites (SVN 723, 725, 736, 737) have been excluded due to anomalous patterns.
Furthermore, all residuals having an absolute beta angle smaller than 15◦ have been
not taken into account due to unmodeled attitude during eclipses.

in the case of the new ECOM (right plot of Fig. 8).
For the POD of the GRACE satellites the Precise Point Positioning (PPP, Jäggi 2007)is well established. It requires the knowledge of precise and consistent GNSS orbits andsatellite clock corrections. Assuming 1 Hz sampling of GNSS data of LEOs, the GNSS
satellite clock corrections are required with a sampling of at least 5 seconds (Bock et al.
2009). For the generation of 5 second clock products, GNSS observation files with a higher
sampling than the common 30 seconds are needed. They are available from the IGS realtime service with a sampling of 1 Hz (Caissy et al. 2012). At least in the early years, the
IGS real-time network was to a large extent independent from the legacy network. In thiscontext, in particular for generation of GLONASS satellite clock products, we have been
confronted with the limitation of available GLONASS tracking data in early years of the
IGS real-time network. The number of available stations providing 5 s data is shown on
the left side of Fig. 9, where grey color represents GPS only, green GPS/GLONASS andwhite no data available. As can be seen from Fig. 9 before the end of 2010 no 5 s RINEX2
files with GLONASS data are available. On the right side of the Fig. 9 the percentage
of completeness of the GLONASS satellite clock products is shown for the 30 s sampling
rate.
Figure 10 shows the percentage of completeness of the satellite clock products with 30 s
(left side) and 5 s sampling (right side) over the period 2006–2007. It can be noticed thatfor the period shown, the overall completeness is 100% for both sampling rates, however
there are some GPS satellites (namely G12, G15, G29, G31 and G32) for which both, 30 s
and 5 s clock corrections are not complete. These data gaps are mainly due to reduced
tracking of (unhealthy) satellites.

40

6 CODE contribution to the EGSIEM reprocessing

ABPO
ADIS
ALGO
ALIC
AMC2
AREQ
ARTU
AUCK
BOGI
BOGT
BOR1
BRAZ
BREW
BRST
BRUS
BZRG
CAGZ
CAS1
CEDU
CHPI
CHUR
CONZ
CRO1
DARW
DAV1
DGAR
DHLG
FAA1
FAIR
FFMJ
GLPS
GOLD
GOPE
GRAZ
GUAM
GUAO
HERT
HNPT
HOB2
HOFN
HRAO
IENG
IISC
IRKM
ISPA
JOZ2
KARR
KELY
KIR0
KIRU
KIT3
KOKB
KOUR
LEIJ
LHAZ
MAC1
MAD2
MADR
MAL2
MAR6
MAS1
MATE
MAW1
MBAR
MCM4
METS
MIZU
MKEA
MOBN
MOBS
NICO
NNOR
NRIL
NRL1
NRMD
NSSP
NTUS
NYA2
OHI3
ONSA
PADO
PDEL
PERT
PETS
PIE1
PIMO
POL2
POTM
QUIN
RABT
RCMN
REDU
REYK
RIO2
SANT
SASS
SEY1
SHAO
SOFI
SPT0
STHL
STR2
SUTH
SUTM
SUWN
TASH
TID1
TIDB
TITZ
TOW2
UCLU
ULAB
UNB3
USN3
USUD
VILL
VIS0
WARN
WROC
WSRT
WTZJ
WTZR
XMIS
YAKT
YAR3
YELL
YKRO
ZIM2

100

R01
R02
R03
R04
R05
R06
R07
R08
R09
R10
R11
R12
R13
R14
R15
R16
R17
R18
R19
R20
R21
R22
R23
R24

Jan-10 Mar-10 May-10
001
060
121

Jul-10182

Sep-10 Nov-10 Jan-11 Mar-11 May-11
244
305
001
060
121

Jul-11
182

Sep-11 Nov-11 Jan-12
244
305
001

95
90
85
80
75
70
65
% of completness

60
55
50
45
40
35
30
25
20
15
10
5
0

2008
001

2008
183

2009
001

2009
182

2010
001

2010
182

2011
001

2011
182

Figure 9: (Left): number of stations delivering 5 s RINEX2 files, where grey color presents GPS
only, green GPS/GLONASS and white no data available. (Right): completeness of
30 s GLONASS clock corrections for the 2008-2011 period.

2006
001

95
90
85
80
75
70
65
% of completness

60
55
50
45
40
35
30
25
20
15
10
5
0
2006
060

2006
121

2006
182

2006
244

2006
305

2007
001

2007
060

2007
121

2007
182

2007
244

2007
305

2008
001

100

G01
G02
G03
G04
G05
G06
G07
G08
G09
G10
G11
G12
G13
G14
G15
G16
G17
G18
G19
G20
G21
G22
G23
G24
G25
G26
G27
G28
G29
G30
G31
G32
2006
001

95
90
85
80
75
70
65
60

% of completness

100

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

55
50
45
40
35
30
25
20
15
10
5
0
2006
060

2006
121

2006
182

2006
244

2006
305

2007
001

2007
060

2007
121

2007
182

2007
244

2007
305

2008
001

Figure 10: Completeness of 30 s (left) and 5 s (right) GPS clock corrections for the time period
between 2006 and 2007.

41

CODE Analysis Center

References
D. Arnold, 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.
G. Beutler, 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.
H. Bock, R. Dach, A. Jäggi, and G. Beutler. High-rate GPS clock corrections from
CODE: support of 1 Hz applications. Journal of Geodesy, 83(11):1083–1094, 2009.
doi: 10.1007/s00190-009-0326-1.
M. Caissy, L. Agrotis, G. Weber, M. Hernandez-Pajares, and U. Hugentobler. The International GNSS real–time Service. GPS World, pages 52–58, June 2012.
R. Dach, T. Schildknecht, U. Hugentobler, L.-G. Bernier, and G. Dudle. Continuous
geodetic time transfer analysis method. Ultrasonics, Ferroelectrics, and Frequency
Control, IEEE Transactions on, 53(7):1250–1259, 2006. doi: 10.1109/TUFFC.2006.
1665073.
R. Dach, S. Schaer, S. Lutz, C. Baumann, H. Bock, E. Orliac, L. Prange, D. Thaller,
L. Mervart, A. Jäggi, G. Beutler, E. Brockmann, D. Ineichen, A. Wiget, G. Weber,
H. Habrich, W. Söhne, J. Ihde, P. Steigenberger, and U. Hugentobler. Center for
Orbit Determination in Europe: IGS Technical Report 2013. In R. Dach and Y. Jean,
editors, International GNSS Service: Technical Report 2013, pages 21–34. IGS Central
Bureau, May 2014.
R. Dach, S. Lutz, P. Walser, and P. Fridez, editors. Bernese GNSS Software, Version
5.2. Astronomical Institute, University of Bern, Bern, Switzerland, November 2015a.
ISBN 978-3-906813-05-9. doi: 10.7892/boris.72297. URL ftp://ftp.unibe.ch/aiub/
BERN52/DOCU/DOCU52.pdf. User manual.
R. Dach, S. Schaer, S. Lutz, D. Arnold, H. Bock, E. Orliac, L. Prange, A. Villiger, L. Mervart, A. Jäggi, G. Beutler, E. Brockmann, D. Ineichen, A. Wiget, A. Rülke, D. Thaller,
H. Habrich, W. Söhne, J. Ihde, P. Steigenberger, and U. Hugentobler. Center for Orbit
Determination in Europe: IGS Technical Report 2014. In R. Dach and Y. Jean, editors, International GNSS Service: Technical Report 2014, pages 21–34. IGS Central
Bureau, May 2015b.
M. Fritsche, K. Sośnica, C. Rodriguez-Solano, P. Steigenberger, K. Wang, R. Dietrich,
R. Dach, U. Hugentobler, and M. Rothacher. Homogeneous reprocessing of GPS,42

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GLONASS and SLR observations. Journal of Geodesy, 88(7):625–642, 2014. doi:
10.1007/s00190-014-0710-3.
A. Jäggi. Pseudo-stochastic orbit modeling of low Earth satellites using the Global Positioning System. In Geodätisch-geophysikalische Arbeiten in der Schweiz, volume 73.
Schweizerische Geodätische Kommission, Institut für Geodäsie und Photogrammetrie,
Eidg. Technische Hochschule Zürich, Zürich, 2007.
S. Lutz, M. Meindl, P. Steigenberger, G. Beutler, K. Sośnica, S. Schaer, R. Dach,
D. Arnold, D. Thaller, and A. Jäggi. Impact of the arc length on GNSS analysis
results. Journal of Geodesy, 90(4): 365-378, 2016. doi: 10.1007/s00190-015-0878-1.
A. Maier, A. Sušnik, D. Arnold, K. Sośnica, R. Dach, and A. Jäggi. Validation of GNSS
orbits using Satellite Laser Ranging data. In XXVI General Assembly of the IUGG,
Prague, Czech Republic, June 22 - July 2, 2015, 2015. Poster.
L. Prange, R. Dach, S. Lutz, S. Schaer, and A. Jäggi. The CODE MGEX orbit andclock solution. In P. Willis, editor, IAG Potsdam 2013, International Association of
Geodesy Symposia. Springer, 2016a. doi: 10.1007/1345_2015_161.
L. Prange, E. Orliac, R. Dach, D. Arnold, G. Beutler, S. Schaer, and A. Jäggi. CODE’s
five-system orbit and clock solution for the IGS Multi-GNSS Experiment with updated
orbit model. Journal of Geodesy, 2016b. submitted.
K. Sośnica, R. Dach, A. Jäggi, P. Steigenberger, and D. Thaller. GNSS orbit validation
using SLR at CODE. In International GNSS Service: Analysis Center Workshop,
June 23-27, Pasadena, California, USA., 2014. Poster.
T. A. Springer, G. Beutler, and M. Rothacher. A new solar radiation pressure model for
the GPS satellites. GPS Solutions, 2(3):50–62, 1999. doi: 10.1007/PL00012757.
P. Steigenberger, R. Dach, L. Prange, and O. Montenbruck. Galileo satellite antennamodeling. In EGU General Assembly, Vienna, Austria, April 2015. Presentation.
E. Tébault, C. C. Finlay, C. D. Beggan, P. Alken, J. Aubert, O. Barrois, F. Bertrand,
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F. J. Lowes, S. Macmillan, M. Mandea, C. Manoj, S. Maus, N. Olsen, V. Petrov, V. Ridley, M. Rother, T. J. Sabaka, D. Saturnino, R. Schachtschneider, O. Sirol, A. Tangborn, A. Thomson, L. Tøffner-Clausen, P. Vigneron, I. Wardinski, and T. Zvereva.
International Geomagnetic Reference Field: the 12th generation. Earth, Planets andSpace, 67(1):79–98, May 2015. doi: 10.1186/s40623-015-0228-9.
All publications, posters, and presentations of the Satellite Geodesy research group at
AIUB are available at http://www.bernese.unibe.ch/publist .

43

CODE Analysis Center

44

NRCan Analysis Center
Technical Report 2015
B. Donahue, R. Ghoddousi–Fard, 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 2015 (products labelled “em*”). Additionally,changes to the stations operated by NRCan are briefly described. Readers are referredto the Analysis Coordinator web site (http://acc.igs.org) for historical combination
statistics of the NRCan–AC products.

2 NRCan Core Products
There was one major change for NRCan–AC Ultra–Rapid, Rapid and Final (GLONASS)
core products in 2015. The Bernese production software supporting these was updated
from version 5.0 to version 5.2 (Dach et al. 2015). The exact dates were: Ultra–Rapid[2015–02–13], Rapid [2015–02–12] and Final [2015–02–01]. The analysis summary (ACN)
for both the Ultra–Rapid and Rapid strategies is available from the following anonymous
ftp site: ftp://ftp.igs.org/pub/center/analysis/emr_Ultra_And_Rapid_V52.acn
No changes were made to the Final GPS products based on GIPSY–OASIS. Table 1
summarizes the products available from the NRCan–AC. The Final and Rapid products
are available from the following anonymous ftp site: ftp://rtopsdata1.geod.nrcan.gc.
ca/gps/products

45

NRCan Analysis Center
Table 1: NRCan–AC Products
Product

11.1

Description

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

GPS only• Time Span 1994–11–02 to 2014–03–29• Use of JPL’s GIPSY-OASIS II v6.3
• Daily orbits, ERP and SINEX• 5-min clocks• Submission for IGS repro2 combination

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

GPS only• Since 1994 and ongoing• Use of JPL’s GIPSY–OASIS II v6.3
• Daily orbits, ERP and SINEX• 30–sec clocks• Weekly submission for IGS Final combination

GPS+GLONASS• Since 2011–Sep–11 and ongoing• Use of Bernese 5.0 until 2015–Jan–31• Use of Bernese 5.2 from 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
Rapid(daily)
emrwwwwd.sp3
emrwwwwd.clk
emrwwww7.erp

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

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

46

GPS 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)

4 Operational NRCan stations
GPS+GLONASS• Since 2013–09–13, hour 12• Use of Bernese 5.0 [until 2015–Feb–12]• Use of Bernese 5.2 [from 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)
Real–TimeGPS only• Since 2011–11–10• In-house software (HPGPS.C)• RTCM messages:– orbits & clocks: 1060 (at Antenna Reference Point)– pseudorange biases: 1059
• Interval : 5 sec

3 Ionosphere and DCB monitoring
Daily and near–real–time ionosphere products and DCB estimates continue to be generated internally. NRCan’s global daily total electron content maps (emrg[ddd]0.[yy]i),
generated from about 350 stations in hourly intervals, have resumed their submission to
IGS data center (CDDIS) since April 2015.
Ionospheric irregularities as sensed by GPS phase rate derived indices from real–time
IGS network continue to be monitored in near–real–time. These have been used in a
number of research studies to complement other sensors to study space weather storms
and characterization of ionospheric irregularities over high latitudes (see e.g. GhoddousiFard et al. 2015a, 2015b; Ghoddousi-Fard and Lahaye 2015; Prikryl et al. 2015a, 2015b,
2015c).

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
+ 15 GPS only stations. Several upgrades/changes to the CGS–CACS were completed
in 2015 and these are listed in Tab. 2. Fig. 1 shows a map of the NRCan GPS/GNSS
network as of January 2016. Further details about the NRCan stations and access to the47

NRCan Analysis Center
NRCan public GPS/GNSS data and site logs can be found at http://www.nrcan.gc.ca/
earth-sciences/geomatics/geodetic-reference-systems/10781 or from the following
anonymous ftp site: ftp://rtopsdata1.geod.nrcan.gc.ca/gps
Table 2: NRCan Station Upgrades in 2015
Station

Date

Remarks

albh
albh
alg2

2015–09–15
2015–09–15
2015–12–10

dra3
dubo
flin
hlfx
sch2

2015–07–11
2015–10–23
2015–07–06
2015–07–23
2015–08–06

Station upgraded from GPS–only to GNSS
Antenna AOAD/M_T SCIS switched to TRM59800.00 SCIS
Station repaired and brought back on–line with
JAVAD TRE_G3TH DELTA receiver after extended outage
Antenna NOV750.R4 NONE switched to TPSCR.G3 NONE
New antenna cable
NOVS dome installed
New antenna cable
New antenna cable

alrt
eur2
reso
tukt

holm

qiki

invk
bcrk

iqal

kglk
whit

bake
yel3

atli

repl

yell

nain

rnkn
chur

sch2
kuuj

chu2
flin

will
drao

prds

stj2
stjo

baie
escu
pper
vald lpoc she2
hlfx
frdn
algo cags

lg1g

sask

picl
dubo
winn

hrst

ross
mchn

pary

nrc1
lcur
god2 cbrg kngs
pwel
kngv

2016 Jan 29 14:36:42
Figure 1: NRCan
Public GPS/GNSS Stations (CGS–CACS in blue, CGS–RACS in red and
GSC–WCDA in green).

48

References

5 Acknowledgment
ESS Contribution number / Numéro de contribution du SST: 20150427
c Her Majesty the Queen in right of Canada 2016

References
Dach, R., S. Lutz, and P. Walser. Bernese GNSS Software Version 5.2 User Manual.
Astronomical Institute, University of Bern (AIUB), 2015.
Ghoddousi–Fard, R., L. Nikitina, D. Danskin, P. Prikryl, and F. Lahaye. Analysis of
GPS phase rate variations in response to geomagnetic field perturbations over the
Canadian auroral region. Advances in Space Research, 55:1372–1381, 2015a. doi:
10.1016/j.asr.2014.12.021.
Ghoddousi–Fard, R., P. Prikryl, and F. Lahaye. Characterization of ionospheric GPS
phase irregularities over the Canadian auroral region. Proceedings of the ION 2015
Pacific PNT Meeting, Honolulu, Hawaii, USA, April 20–23, 2015, pp. 71–77, 2015b.
Ghoddousi-Fard, R. and F. Lahaye. High latitude ionospheric disturbances: characterization and effects on GNSS precise point positioning. 2015 International Associationof Institutes of Navigation World Congress, Prague, CZ, October 20–23, IEEE, 2015.
doi: 10.1109/IAIN.2015.7352231.
Prikryl, P., R. Ghoddousi–Fard, J.M. Ruohoniemi, and E.G. Thomas. GPS phase scintillation at high latitudes during two geomagnetic storms. In: Zhang, Y. and Paxton,
L. J. (eds.). Auroral dynamics and space weather, AGU, Wiley Publ., 2015a. ISBN:
978–1–118–97870–2
Prikryl, P., R. Ghoddousi–Fard, E.G. Thomas, J.M. Ruohoniemi, S.G. Shepherd, P.T. Jayachandran, D.W. Danskin, E. Spanswick, Y. Zhang, Y. Jiao, and Y.T. Morton. GPSphase scintillation at high latitudes during geomagnetic storms of 7–17 March 2012
– Part 1: The North American sector. Annales Geophysicae, 33:637–656, 2015b. doi:
10.5194/angeo–33–637–2015.
Prikryl, P., R. Ghoddousi–Fard, L. Spogli, C.N. Mitchell, G. Li, B. Ning, P.J. Cilliers,
M. Aquino, M. Terkildsen, P.T. Jayachandran, Y. Jiao, Y.T. Morton, J.M. Ruohoniemi, E.G. Thomas, Y. Zhang, A.T. Weatherwax, L. Alfonsi, and G. DeFranceschi.
GPS phase scintillation at high latitudes during geomagnetic storms of 7–17 March
2012. Part 2: Interhemispheric comparison. Annales Geophysicae, 33, 657–670, 2015c.
doi: 10.5194/angeo–33–657–2015.

49

NRCan Analysis Center50

ESA/ESOC Analysis Center
Technical Report 2015
T.A. Springer, W. Enderle, C. Garcia-Serrano, J. Feltens,
I. Romero, 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 2015.

2 Overview 2015
2.1 Routine Products
The ESA/ESOC IGS Analysis centre contributes to all the core IGS analysis centre products, being:• Reprocessed Final GPS products (repro2)– Provided from 1995 to 2015 day 180, from there on our normal Final products.
– Based on 24hour solutions using 150 stations GPS-only, until 2008
– Based on 24hour solutions using 110 stations GPS+GLONASS, from 2009
– Consisting of Orbits, Clocks (300s), daily SINEX coordinates, and EOPs
– Clocks with 30s sampling are also generated but not made publicly available• Final GNSS (GPS+GLONASS) products
51

ESA/ESOC Analysis Center– 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) products– Provided daily for the previous day– Available within 3 hours after the end of the observation day– Based on 24hour solutions using 110 stations– True GNSS solutions 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 stream52

2 Overview 2015
• GNSS Sensor Stations– A set of 10 globally distributed GNSS sensor stations– Station data available in real-time with 1 second data sampling

Besides these core products ESA is very active in different working groups. Most notably are our efforts in the Real-Time Service where besides being one of the analysis
centres we are also responsible for the analysis centre coordination. Also our efforts in thescope of MGEX, the antenna calibarations and satellite orbit modeling working groups
are significant.
An up to date description of the ESA IGS Analysis strategy may always be found at:
ftp://dgn6.esoc.esa.int/products/esa.acn

2.2 Product Changes
The main changes in our processing in 2015 were the following:• Upgrade of the ESA/ESOC GNSS Sensor Station network• Continue using box-wing models for the GNSS satellites to a priori model the Solarand Earth Albedo radiation pressure. Besides GPS and GLONASS also developed
box-wing models for Galileo, BeiDou and QZSS

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 fortrue GNSS precise point positioning. In particular for this purpose, the sampling rateof 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 scientificinvestigations as there is no aliasing and no smoothing between subsequent solutions. An
other unique feature is that our rapid products are, besides being one of the best, also oneof the most timely 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 verysignificant difference. Another important feature of the ESA products is that we use abox-wing model for the GNSS satellites to a priori model the Solar- and Earth Albedo

53

ESA/ESOC Analysis Centerradiation pressure. The GNSS block type specific models were tested thoroughly in thescope of our IGS reprocessing and the results were presented at the IGS workshop in 2014
(Springer 2014). Significant improvements were observed for most, if not all, estimatedparameters.

2.4 Reprocessing Activities
ESA/ESOC has participated in the IGS reprocessing efforts (repro1 and repro2) for the
IGS contribution to the realisation of the International Terrestrial Reference Frame 2008
and 2014 (ITRF2008, and ITRF2014). For this reprocessing effort ESA has processed
all historic GNSS data of the IGS from 1994 to 2015 day 180. In this reprocessing theyears 1994 to 2008 are reprocessed using only GPS observations, and from 2009 onwards
the reprocessing fully includes the GLONASS observations and thus provides true GNSS
solutions. The products from the ESA official reprocessing efforts are available from theofficial IGS data centres (label "es1" and "es2"). The most recent ESA reprocessing
products, based on the ITRF2008, are also available from our ftp server: ftp://dgn6.
esoc.esa.int/igs/repro2 (label "es2").
An interesting difference between our es1 and es2 reprocessing is that, as mentioned before,
from 2009 onwards our es2 products are GNSS products. Also for our es2 products we did
generate 30 second clock estimates. We produce these high-rate clock products because weare also very active in processing GNSS data from Low Earth Orbiting (LEO) receivers.
For LEO processing high-rate clocks are very much needed to get accurate orbits based
when using the well-known PPP approach for precise orbit determination.

3 GNSS Sensor Station Upgrade
ESA/ESOC is committed to provide worldwide data for all GNSS constellations during
this year as a result of having completed the upgrade of the equipment at all the current
installations over the last year as well as focusing on the establishment of collaborations
with third parties in order to install new stations at various new locations if agreements
can be reached with the corresponding organizations. Following the acquisition of a large
number of Septentrio PolarRx4 receivers and Septentrio Chokering MC antennas plus 4
Leica AR25 rev.4 antennas in 2011-2012, the entire ESA GNSS network, see Figure 1, now
operates these Septentrio receiver/antenna combinations, with the exception of MGUE,
MAL2, MAS1 and FAA1 where the Leica antennas are used. The network was expandedwith the new station AWAR (New Zealand) in the 2nd half of 2014, followed by DUBA
(U.A.E), BANT (Malaysia) and TSBA (Japan) in the 1st half of 2015. Finally, in November 2015 the current status of the network was completed with the new station ESOC.
No data is publicly available for any of these newly installed stations. The Septentrio
receivers provide all the expected measurements for the GNSS constellations as available:54

4 Ionosphere Modeling Activities

Figure 1: ESA/ESOC GNSS Station Network

GPS, GLONASS, Galileo, QZSS, Compass, SBAS, EGNOS, etc. and as of mid-2013,
ESA/ESOC has been contributing with daily, hourly and high rate multi-GNSS Rinex 3
data to the MGEX campaign for 10 of its 16 stations. Also, since the beginning of 2013,
ESA/ESOC has been providing NBS (NavBits) data from this same set of stations toEumetsat to support LEO satellite occultation processing. For 2016 worldwide coverageis planned to be enhanced considerably with negotiations with third parties in Russia andCanada ongoing. The maps below show a projection of the impact on the global coveragefor the inclusion of the 6 new sites that are envisaged througout both countries.

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. In addition, predicted products are delivered. ESOC employs the Ionosphere
Monitoring Facility (IONMON) for its ionosphere processing, which became in 2013 andintegral part of ESOC’s NAPEOS software. While operational ESOC TEC maps processing is still single-layer-based, current development activities are clearly focused on 3Dmodelling, which shall, once available, replace the old single-layer representations. In addition to TEC observables originating from different GNSS systems (GPS, GLONASS,

55

ESA/ESOC Analysis Center
Galileo, Beidou, QZSS, and in addition to GNSS: altimetry, DORIS), observed electron
density data from different sources (radio occultation, ionosonde, others) shall then enter
into these 3D ionosphere maps production. In the new 3D approach, all the above listed
observation data types shall be assimilated into a grid of background electron densities.
This background will be created with an empirical median model of the ionosphere andplasmasphere. The mathematical models for the new 3D approach were worked out so far(and documented ESOC-internally), comprising:• Background electron density model algorithms• Dedicated 3D grid combining spherical shells with L-shells to reflect the spatial
structures of the ionosphere and plasmasphere as function of SM latitude, longitudeand L-value• Transformations between solar-magnetic (SM), geomagnetic and geographic coordinates• Dedicated assimilation methods of TEC and electron density observables into the
3D background grid
• Dedicated electron density interpolators for product generation, e.g. for IONEX files• Dedicated TEC integrators for product generation, e.g. for IONEX files• Creation of planar electron density and TEC cuts into any direction through the 3D
electron density grid as new product type• The new assimilation approach shall allow for a significant enhancement of time
resolution; 10–15 minutes are currently targeted• Fast and robust algorithms

At the actual stage of development (January 2016), the mathematical algorithms for thisnew 3D assimilation approach and their coding as new component of NAPEOS are completed. Currently, last source code upgrades and adaptions are conducted concerning theprocessing of the very different types of observation data, originating from very distinct
sources. Then a test case and test data need to be set up. Initially the new software will
be tested with GPS and GLONASS TEC data; in a next step COSMIC electron densities
will be included. After that, in further steps, additional observation data types will follow. Once the new 3D assimilation approach in NAPEOS will be operational, ESOCâĂŹs
ionosphere processing will be switched over from the current single layer processing to thisnew 3D modelling technique. This will then also concern ESOCâĂŹs ionosphere products
delivered to the IGS, including new aspects such as 3D IONEX.
Additional activities at ESOC in the area of the ionosphere in 2015 will be:• Preparation of a follow-up study to the Iono Study of 2009-10• Establishment of a new model for the plasmasphere in cooperation with the German56

5 Multi-GNSS (MGEX)
Aerospace Center (DLR) in Neustrelitz, Germany. This plasmasphere model shallthen complement the new 3D assimilation approach• Establishment of an operational ionospheric and tropospheric media calibration
service for ESOC Flight Dynamics (troposphere part running already in a preoperational mode)• Routine contributions to ESA’s Space Situational Awareness (SSA) service in space
weather part
• Important future aspects concerning the ionosphere:– Implementation of a more sophisticated Iono prediction scheme at ESOC
– Implementation of a physics-based 3D Iono model, inspired from the outcomeof the anticipated follow-up Iono study

5 Multi-GNSS (MGEX)
We periodically analyze the data from the IGS Multi-GNSS Experiment (MGEX) as at
the current stage we prefer a detailed analysis of the MGEX data over routine analysis.
In the scope of these activities we have derived a consistent set of Galileo, BeiDou and
QZSS PCO/PCVs based on processing the data of 2014 and 2015. We have extended our
box-wing modeling activities now also to the satellites of the âĂĲnewâĂİ constellations,
i.e., Galileo, BeiDou and QZSS. We believe that for BeiDou and QZSS an accurate modelof the satellites will be of great benefit, if not even mandatory. This is due to the fact thatfor small beta angles these satellites switch their attitude mode from yaw-steering (thenominal 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 thesolar radiation pressure becomes very hard to model. In the orbit normal mode phase thewidely used ECOM model, and also the enhanced ECOM2 model, fail to properly model
the radiations forces. The main interesting features and challenges we have found so far
in our multi-GNSS analysis activities were presented at the IGS workshop in 2014 and2016, Garcia-Serrano 2014 and Garcia-Serrano 2016, and may be summarized as:• Strong elevation dependent pattern in the BEIDOU pseudo range residuals for the
MEO satellites• Strong azimuthal dependent pattern in the GALILEO carrier phase residuals, clearlyan azimuthal ANTEX pattern needed• Severe inconsistency between the three GPS phase signals (L1, L2, and L5); a periodic effect with an amplitude of 50 mm clearly visible• Severe challenges to model the QZSS satellite during the orbit normal mode phase(|β| < 200 )57

ESA/ESOC Analysis Center

Figure 2: Expected solar radiation pressure variations for the different GNSS satellite types• 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 )Clearly the "orbit normal" attitude mode is posing a significant challenge to achieve
orbit with centimeter level precission. Furthermore, thanks to our work on constructing
reasonable accurate box-wing models for the different GNSS types we have realised thatthe variability of the solar radiation pressure acting on the satelllites differs significantly
between the different satellite types. In a, very, rough approximation we may consider
that this variability is determined by surface ratio’s of the satellite X- and Z-sides. The
maximum area as seen by the Sun, when the satellit is flying in the standard yaw-attitudemode, is basically the sum of the X- and Z-areas. The minimal area is the area of thesmaller of the two sides. The variability of the solar radiation pressure acting on thesatellite is then given by this mass ratio devided by the mass of the satellite. The heavier
the satellite the less sensitive it will be to the variation in the surface areas that are facing
the sun. We have used this "crude" approximation to generate a "sensitivy" table forthe different GNSS satellites, shown in Figure 2. In this table we have normalized thevalues with respect to the GPS-IIA satellites. The sensitivity ranking now tells us whichsatellites will experience larger solar radiation pressure variations, i.e., the QZSS satellites
is ranked in place 1 of our senstivity table and thus is the satellite for which we expect
the largest solar radiation pressure variations. This is no surprise as this is also by far thelargest satellite. Surprising is that the Galileo satellites are on place 2. This is mainly
caused by the fact that the Galileo satellites are very light compared to all other GNSS
satellites.

58

6 Summary

Figure 3: Along-track (left) and Cross-track (right) overlap statistics with and without applying
the satellite type specific box-wing models.

Despite that it is hard to find information regarding the surface areas and properties ofmost GNSS satellites we have attempted to make box-wing models for all the different
satellites types. Significant time was spend on validating and tuning the different box-wingparameters and this is a process that is still ongoing. However, Figure 3 does clearly show
the positive effect of our box-wing models in both the along- and cross-track directions
for all GNSS constellations. Notice that the improvements are most significant for QZSSand Galileo as expected based on our sensitivity index. The BeiDou satellites also profit
significantly but this is maily due to the orbit normal mode phase!

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 in 2015.
All products are generated using the Navigation Package for Earth Orbiting Satellites(NAPEOS) software. NAPEOS is a state of the art software that is highly accurate, very
efficient, robust and reliable. It enables ESA/ESOC to deliver the high quality products
as required for the IGS but also for the other space geodetic techniques DORIS and SLR.
This is important because besides being an IGS Analysis Centre, ESA/ESOC is also an
Analysis Centre of the IDS and the ILRS.
For 2016 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 QZSS and
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 2016 including
across constellation ambiguity resolution.

59

ESA/ESOC Analysis Center

References
Springer, T., R. Zandbergen, A. Águeda Maté. NAPEOS Mathematical Models and Algorithms. DOPS-SYS-TN-0100-OPS-GN, Issue 1.0, Nov 2009, ftp://dgn6.esoc.esa.
int/napeos, 2009.
Feltens, J., M. Angling, N. Jakowsk, C. Mayer, M. Hoque, M. Hernández-Pajares,
A. García-Rigo, R. Orús-Perez, A. Aragón-Ange. Analysis of the State of the Art
Ionosphere Modelling and Observation Techniques. DOPS-SYS-TN-0017-OPS-GN,
Iss. 1/0, 26/06/2009, 2009.
Feltens, J., M. Angling, N. Jackson-Booth, N. Jakowsk, M. Hoque, C. Mayer,
M. Hernández-Pajares, A. García-Rigo, R. Orús-Perez, A. Aragón-Ange,J. M. J. Zornoza. Recommendations for a New European Ionosphere Monitoring
System, DOPS-SYS-RP-5001-OPS-GN Iss. 1/0, 20/01/2010, 2010.
Dilssner, F., T. Springer, E. Schönemann, W. Enderle. Estimation of Satellite Antenna
Phase Center Corrections for BEIDOU. IGS Workshop 2014, June 23-27, Pasadena,USA, 2014.
Garcia–Serrano, C., L. Agrotis, F. Dilssner, J. Feltens, M. van Kints, I. Romero,
T. Springer, W. Enderle. The ESA/ESOC Analysis Center Progress and Improvements. IGS Workshop 2014, June 23-27, Pasadena, USA, 2014.
Garcia–Serrano, C., T. Springer, F. Dilssner, E. SchÃűnemannr, W. Enderle. ESOC’s
Multi-GNSS Processing. Presentation at IGS Workshop 2016, Sydney, Australia,
2016.
Springer, T., M. Otten, C. Flohrer, F. Pereira, F. Gini, W. Enderle. GNSS Satellite Orbit
Modeling at ESOC. IGS Workshop 2014, June 23-27, Pasadena, USA, 2014.

60

GFZ Analysis Center
Technical Report 2015
M. Fritsche, Z. Deng, M. Ge,
T. Nischan, M. Uhlemann, G. Beeskow,
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: mathias.fritsche@gfz-potsdam.de

1 SummaryDuring 2015, 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.
Minor changes in the processing setup became necessary once a degradation of the GFZclock solution had become evident. In particular, a large number of GPS satellite were
excluded from the final clock combination. The reason was identified to be an issue related
to the introduction of P1-C1 differential code bias parameters. In addition, an update
related to the selection of the reference clock became necessary at the end of 2015.
The multi-GNSS processing was continued routinely during 2015 including GPS, GLONASS,
BeiDou and Galileo with only few exception from a regular submission. Since May 2015,
also QZSS has been included in the processing.

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

61

GFZ Analysis Center

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

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

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

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

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 1869.1 (02-11-2015)

gbuWWWWD_HH.sp3
gbuWWWWD_HH.erp

Adjusted and predicted orbits for GPS/GLONASS/Galileo/BeiDou/QZSS
Earth rotation parameters62

4 Multi-GNSS data processing(a) Clock standard deviation of AC individual com- (b) Smoothed weighted RMS of GPS orbit differpared to IGS Final solution.
ences between AC individual and IGS Final solution.

Figure 1: Degradation of GFZ Final orbit and clock submissions during GPS weeks 1864 to 1871
caused by an improper epoch-wise reference clock selection.

3 Operational GPS/GLONASS data processing and latest
changes
EPOS-8 processing software is following the IERS Conventions 2010 (Petit and Luzum2010). For the IGS Final, Rapid and Ultra-rapid chains approximately 200, 110, and 95
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 theconsistency with respect to the repro-2 processing strategy.
A high satellite clock exclusion rate was noticed from the IGS Final clock combination.
At the same time, the corresponding orbit solution was not affected. Investigations on
GFZ AC side revealed that the regularly updated P1-C1 differential code biases (DCBs)
did not enter into the processing. Instead, outdated monthly DCB values valid for August
2013 had been in use causing a continuous decrease in the clock solutions’ consistency
with the constant renewal of the GPS constellation.
GFZ product submissions for GPS weeks 1864 through 1871 are affected by an improper
epoch-wise reference clock selection. Both, the satellite clock performance (Figure 1(a))
as well as the orbits (Figure 1(b)) are affected.

4 Multi-GNSS data processing
The IGR-like multi-GNSS processing was continued in 2015. Since May 2015, QZSS is
included in the daily analysis. Hence, GFZ’s multi-GNSS solution now covers 5 different

63

GFZ Analysis Center

Number of Satellites

80
70
60

GAL median: 5

QZSS: 1

BDS median: 13

50
40

GLO median: 23

30
20
10

GPS median: 31

0
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

2015
Figure 2: Total number of satellite per GNSS included in the daily MGEX processing.

systems, namely GPS, GLONASS, Galileo, BeiDou and QZSS. Figure 2 shows the total
number of satellites per GNSS included in the gbm MGEX solution which can be accessed
at ftp://ftp.gfz-potsdam.de/pub/GNSS/products/mgex or ftp://cddis.gsfc.nasa.
gov/gps/products/mgex. Table 3 shows the corresponding observation type selection
made for the individual GNSS.
As an orbit quality measure, the RMS of differences from overlapping orbit positions(4 hours interval) are evaluated. Figure 3 shows the daily median RMS of the orbit
overlaps for each satellite. Corresponding RMS values are below 10 cm for most of the
GPS satellites, while they can reach up to 30 cm for GLONASS. A similar range canbe found for the Galileo satellites with the worst performance for those two FOC-typesatellites in the eccentric orbit. For BeiDou, the three different types of orbits GEO,
IGSO, and MEO can clearly be separated. Here, the GEO satellites reveal the largest
RMS value of up to 3 meter. The IGSO and MEO satellites show RMS values of 30 cm
and 10 cm, respectively. The QZSS satellite reveals an orbit overlap RMS of 90 cm. Since
GPS-week 1843, the gbm clock product is given at a 30 sec sampling rate.
A new MGEX-processing chain was established in order to provide multi-GNSS orbit andclocks in an ultra-rapid like style. Accordingly, the analysis of 24 h observations is combined with a 24 h prediction for satellite orbits. The corresponding routine processing wasstarted at 2nd November, 2015. Associated products identified with the gbu acronym (cf.
Table 1) can be acquired at ftp://ftp.gfz-potsdam.de/pub/GNSS/products/mgex.
An independent validation of the microwave-based gbm satellite orbits was performed using
SLR measurements. Figure 4 shows the resulting mean bias and standard deviation fordifferent satellite types which indicate the achieved orbit accuracies for that satellites
currently observed by the International Laser Ranging Service.

64

4 Multi-GNSS data processing

Table 2: Recent Processing changes
Date

IGS

IGR/IGU

Change2015-02-13
2015-02-26

w1831
w1864

w1832.5
w1864

2015-03-16

w1864

w1864

2015-10-05
2015-12-02

w1864
w1872

w1873.4

Use updated GPS P1-C1 differential code biases
Switch to 12th generation of the International Geomagnetic
Reference Field (IGRF)
Allow inter system bias reference receiver be different fromclock reference receiver
Switch from CODE TEC maps to IGS combined TEC maps
Fix clock reference selection procedure

300
280
260
240
220
200
180
160
140
120
100
80
60
40
20
0

Satellite System# Satellites

Observation TypesGPS
GLONASS
Galileo
BeiDou
QZSS

31
24
9
13
1

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

GEO

GPS

GLONASSIGSO MEOGAL BDS
QZSS

G01
G02
G03
G04
G05
G06
G07
G08
G09
G10
G11
G12
G13
G14
G15
G16
G17
G18
G19
G20
G21
G22
G23
G24
G25
G26
G27
G28
G29
G30
G31
G32
R01
R02
R03
R04
R05
R06
R07
R08
R09
R10
R11
R12
R13
R14
R15
R16
R17
R18
R19
R20
R21
R22
R23
R24
E11
E12
E19
E14
E18
E22
E26
C01
C02
C03
C04
C05
C06
C07
C08
C09
C10
C11
C12
C14
J01

Orbit Overlap: RMS [cm]Table 3: Used observation types and number of satellites in the multi-GNSS data processing.

Figure 3: Daily median RMS [cm] of the differences from overlapping orbit positions (4 hours
interval).

65

GFZ Analysis Center
0.5

GEO

SLR residuals [m]

0.4

IGSO

MEO

0.3
0.2
0.1
0.0
−0.1
−0.2
−0.3
−0.4
−0.5

G06 E11 E12 E14 E18 E19 E20 E22 E26 C01 C08 C09 C11
Figure 4: SLR residual statistics. The bias (colored) and STDV (grey) are given for individual
GPS, Galileo and BeiDou satellites.

5 RINEX tool box gfzrnx

The development of a toolbox named gfzrnx was started in 2015. The primary goal of thiscommand-line oriented toolbox is the support of RINEX file conversion and manipulation
operations. The program allows to handle Observation, Navigation, and Meteorological
RINEX data types. In the following, an overview of the implemented functions is given:– Check format consistency and possibly repair– Conversion between versions 2 and 3– File splice/split operations– Generation of statistics based on file content– File header editing– Version-dependent file naming– File content manipulations (e. g. data sampling, observation type selection, etc.)
Currently, the following operating systems are supported: Linux, Windows, MAC OS X,
and SunOS. gfzrnx can be downloaded at http://semisys.gfz-potsdam.de/semisys/
scripts/download and can be used free of charge. Upon interest, users may also subscribe
to the mailing-list gfzrnx@gfz-potsdam.de.

66

References

References
G Petit 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.

67

CNES–CLS Analysis Center
Technical Report 2015
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 2015, the CNES–CLS Analysis Center continued its contribution through the weekly
delivery of final products (Loyer et al. 2015a, Loyer et al. 2015b) using the GINS software
package (Marty et al. 2011). The models, standards and estimated parameters remained
almost the same as those implemented for the REPRO2 campaign. The only but major
evolution was that our hybrid GPS–GLONASS–Galileo solution dedicated to MGEX activities became our official IGS contribution starting week 1840 (April 12, 2015). Moredetails on this change and its impact on the products are given in section 2. In 2015, we
also started producing experimental 5 second sampling clock products and section 3 summarizes a comparison analysis with 30 second products. In section 4, the GPS Wide–Lane
Satellites bias product dependency in the receiver manufacturer is discussed.

2 Multi–GNSS products
We started contributing to the Multi–GNSS Experiment in 2012 with a regular processingof hybrid GPS–GLONASS–Galileo products. To avoid the maintenance of two separated
processing chains we decided to only operate the MGEX one starting week 1840 (12 Apr.
2015). The corresponding GPS and GLONASS orbits and clocks solutions then became
our official contribution to IGS (Tab. 1 and Fig. 1).

682 Multi–GNSS products

Table 1: CNES–CLS IGS final products
Products

Files

Daily GPS, GLONASS (GRG) & Galileo (GRM)
Ephemeris/clock 15–min sampling[grg/grm]wwwwn[0–6].sp3

Daily GNSS clock 30–sec sampling(Compatible for GPS PPP with ambiguity resolution)[grg/grm]wwwwn[0–6].clk

Daily Normal Equations
for EOP and Stations coordinates[grg/grm]wwww[0–6].snx

Summary report for week wwww

grgwwww7.sum

ERP weekly solution

grgwwww7.erp

Week 1840

Figure 1: Main statistics of the CNES/CLS Analysis Center products during 2015. Since week
1840 Galileo satellites are included in the processing.

69

CNES–CLS Analysis Center

GPS

Galileo

GLONASS

IGb08

Figure 2: Network and sub–networks used in our current products. The number of data useddiffers for each constellation.

This change was also associated with a revision of the tracking network. The total numberof stations was reduced from ∼200 to ∼120 in order to compensate the expansion of thenumber of measurements and estimated parameter. During the 30 seconds sampling clock
densification step, the total number of observations reaches now around 8 billion for a
one day arc. The station location selection was optimized in order to include the more as
possible MGEX receivers as well as IGb08 core network sites (Fig. 2). Another motivation
was to be prepared to the transition of IGS products to a true multi–GNSS solution in
the future.
Switching to MGEX products had no significant impact on the orbit and EOP comparison
to other ACs. However we made a mistake in the procedure managing the new stations(their a priori coordinates) and the alignment of the network to the Igb08 frame. This
impacted during several months the global phase measurements residuals (Fig. 1) andintroduced a global translation at the level of one centimeter of the orbit solution in the Z
direction. This problem has been corrected week 1874. It has impacted the GRG clocks
standard deviations at the level of 20 picoseconds compared to IGS combined solution asshown in Fig. 3. It was also visible on the global network PPP solution translations asestimated by the IGS ACC as showed in Fig. 4.

70

2 Multi–GNSS products

Figure 3: Final clocks (AC solutions compared to IGS final).

Figure 4: PPP with IGS final orbit and clocks.

71

CNES–CLS Analysis Center

3 Five–second clock products
PPP of receivers having a rapid and/or erratic displacement (buoys, boats, LEO...) may
need high rate constellation clock products. At least a 5 seconds sampling is needed insuch case. We included the capability to produce such clocks in our operations. But 1Hz
RINEX raw data are needed. However the network of high rate stations is not as dense as
the 30 seconds one. Consequently high rate clocks may not have the same quality as 30
seconds ones (Fig. 5) as they can suffer from a poor distribution, especially for GLONASS(Fig. 6). Nevertheless, it is expected that the 1Hz network will grow in the near future to
overcome these difficulties.

4 Receiver type dependent satellite biases
We wanted to quantify the receiver dependent part of the GPS Wide–Lane Satellites Biases(WSB). The production of these biases is part of our routine processing as we need themto fix zero–difference GPS phase ambiguities to integers. They are also widely used for
PPP with ambiguity fixing using GRG orbit and clock products. WSB are derived from
the Melboune–Wübbena combination of the code and phase observables averaged over a
global network of receivers. For this study we also computed individual WSB solutions
from each receivers of the MGEX network and we got noticeable receiver type dependent

Figure 5: Allan standard deviation of the 30s sampling clock solutions: From the operational
POD network (in black) and from the high rate network (in red).

72

4 Receiver type dependent satellite biases

Figure 6: Example of GLONASS 30s clock solution per satellite (expressed in meters) for DOY
150, 2015. Zero values correspond to a loss of observability.

Figure 7: Two examples of single–receiver WSB sets. The TPS NET–G3A receiver agrees
very well with the average solution. The Trimble NET–R9 exhibits much more
discrepancies.

73

CNES–CLS Analysis Center
biases. Constant offsets are visible between individual series in Fig. 7.
Receiver “families” can be easily identified in Fig. 8 which compares each individual WSB
solution to the averaged official one. Moreover two families can be identified for Trimble
receivers and this is still not understood today.
The maximum discrepancy reaches 0.13 RMS in WL cycles. However we couldn’t noticea significant impact on the Wide–Lane ambiguity fixing success rate when using receiver
type WSB instead of averaged values. Nevertheless, this step is highly sensitive to therobustness of the algorithms and to the process parameterization. In addition, receiver
manufacturer options to process new GNSS signals could lead to a more critical situation
when future WL combinations (e.g. using L1L5) will be used.

Figure 8: GPS WSB RMS differences between individual receivers of the MGEX network (sorted
by receiver types).

74

Reference

Reference
Loyer, S., H. Capdeville, S. Mulet, L. Soudarin, and P. Schaeffer. Applications Cinématique Terrestre et Thermosphère – Exploitations et Applications. CLS–DOS–GEO–
NT–15–001, June 8, 2015.
Loyer, S., H. Capdeville, S. Mulet, and L. Soudarin. Applications Cinématique Terrestreet Thermosphère - Exploitations et Applications. CLS–DOS–GEO–NT–15–003, December 1, 2015.
Marty, JC., S. Loyer, F. Perosanz, F. Mercier, G. Bracher, B. Legresy, L. Portier,
H. Capdeville, F. Fund, J.M. Lemoine, R. Biancale. GINS: the CNES/GRGS GNSS
scientific software. 3rd International Colloquium Scientific and Fundamental Aspectsof the Galileo Programme, ESA Proceedings WPP326, 31 August – 2 September 2011,
Copenhagen, Denmark, 2011.

75

CNES–CLS Analysis Center76

JPL Analysis Center
Technical Report 2015
D. Murphy, N. Amiri, W. Bertiger, S. Desai,
B. Haines, D. Kuang, P. Ries, C. Sakumura,
C. Selle, 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.
E–mail: dwm@jpl.nasa.gov Tel: +1–818–354–0845

1 Introduction
In 2015, 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 2015.
Table 1 summarizes our contributions to the IGS Rapid and Final products. All of ourTable 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

77

JPL Analysis Center
contributions 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 constraint between solutions. We started delivering High-rate (30second) Final GPS clock products starting October 26, 2014 and in our repro2 contribution
we generated these products from May 07, 2000, 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/Ultra-Rapid

2 Processing Software and Standards
The JPL AC continues to utilize the GIPSY/OASIS software package to generate ourcontributions to the IGS which we will refer to in the rest of this report simply as GIPSY.
Starting on November 29, 2015, the products we deliver to the IGS have been generated
with GIPSY version 6.4 which supersedes GIPSY version 6.3 that was used to produce our
IGS repro2 contribution. In our operations, we have adopted our repro2 data processing
approach, which has the following improvements compared to our previous data processing
strategy:• Application of second order ionospheric corrections (Garcia-Fernandez et al. 2013).

• Revised empirical solar radiation pressure model named GSPM13 (Sibois et al. 2014).
• Antenna thrust models per IGS recommendations.

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

A complete description of our current operational processing approach, also used for
repro2, can be found at: https://igscb.jpl.nasa.gov/igscb/center/analysis/jpl.
acn
We continue to use empirical GPS solar radiation pressure models developed at JPL
instead of the DYB-based strategies that are commonly used by other IGS analysis centers.
This choice is based upon an extensive evaluation of various internal and external metrics
after testing both approaches with the GIPSY/OASIS software (Sibthorpe et al. 2011).
GIPSY 6.4 is a relatively minor upgrade over GIPSY 6.3 and provides the following enhancements:78

4 Transition of Operations to Using GIPSYx• Improved reference frame handling with support for large ITRF2014 covariance files• Improved attitude modeling of GPS block IIF at noon and midnight turns• Software upgrades to data editor and PPP tool, several new utilities, bug fixes• Improved geophysical models:– Second-order ionosphere correction: small improvements in the use of IGRF,
IRI, IONEX models– GPT2 model: finer 1◦ resolution and GPT2w a-priori wet delay calculation– Time-varying gravity (including ICGEM format to GIPSY format converter)

3 Overlap Statistics
Figures 1 and 2 show orbit and clock overlap boxplot statistics for 1996-2015 and 2015
respectively. In our processing we use 30-hour arcs centered on noon and determine daily
orbit and clock overlaps using the central 5-hour portion of the 6-hour arc-to-arc overlap
region as one indicator of our precision. The daily orbit overlap is defined to be the medianof the RMS of the 1D orbit differences per transmitter in the central 5-hour region while
the daily clock overlap is the RMS of the RMS clock differences per transmitter in thesame 5-hour central overlap region. Figure 1 shows a slight degradation in orbit overlaps
during the last few years the cause of which is currently being investigated. Figure 2 showsthat the major difference between our Final and Rapid products is fewer days with large
orbit and clock overlaps in the Final products.

4 Transition of Operations to Using GIPSYx
For several years, a C++/python replacement for both GIPSY and Real-Time GIPSY
called GIPSYx/RTGx has been under development which has the following features:• Supports both post-processing and real-time processing of multiple GNSS constellations• Processes data from GPS, GLONASS, and Beidou. Galileo is under development.
However, more work is needed to to be able to create orbit and clock products fromconstellations other than GPS.
• Readily extends to support DORIS and SLR data processing• Multi-processor and multi-threaded capability• Multi-GNSS PPP tool is under development

79

4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5

Final Clock Overlaps [cm]Final Orbit Overlaps [cm]

JPL Analysis Center

9
8
7
6
5
4
3
2
1

1996-2015 Boxplot Statistics for Final Overlaps

96 97 98 99 00 01 02 03 04 05 06 07 08 09 10 11 12 13 14 1596 97 98 99 00 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15
Year

Figure 1: 1996-2015 boxplot statistics for Final orbit and clock overlaps with whiskers at the 5th
and 95th percentiles. Note: overlap definitions can be found in section 3.

3.5

2015 Boxplot Statistics for Final and Rapid Overlaps

Overlaps [cm]

3.0

2.5

2.0

1.5

1.0

Final Orbit Overlaps

Rapid Orbit Overlaps

Final Clock Overlaps

Rapid Clock Overlaps

Figure 2: 2015 boxplot statistics for Final/Rapid orbit and clock overlaps with whiskers at the
5th and 95th percentiles. Note: overlap definitions can be found in section 3.

80

References• Uses similar but not identical file formats to GIPSY
In parallel with the GIPSYx development we have also been developing new operational
software in python to generate both the rapid and final products that we deliver to the
IGS orbit using GIPSYx instead of GIPSY. We are currently testing this new operational
software by comparing rapid and final products generated by both GIPSYx and GIPSY
and expect to start generating our IGS GPS orbit and clock products using this new
operational software in the second half of 2016.

5 Future WorkIn 2016, JPL will continue to submit operational Rapid and Final GPS products to the
IGS using our repro2 processing configuration and our current operational software, whichuses GIPSY 6.4, until we make the transition to using our new operational software whichuses GIPSYx. Our longer term goal is to generate other GNSS constellation orbit andclock products using this new software.

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 2016 California Institute of Technology. Government sponsorship acknowledged.

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.
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.

81

JPL Analysis Center
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.

82

NGS Analysis Center
Technical Report 2015
S. Yoon, J. Saleh, G. Sella, S. Hilla,
M. Schenewerk, K. Choi
National Geodetic Survey
1315 East–West Highway, SSMC3
Silver Spring, MD 20910 U.S.A.
Email: sungpil.yoon@noaa.gov

1 Introduction
In 2015, NGS continued to serve as an IGS analysis center, a regional data center and one of
our team member, Kevin Choi, continued as the analysis center coordinator. This reportsummarizes the routine analysis and data center activities conducted at the National
Geodetic Survey (NGS), and all significant changes that occurred during the year 2015.

2 Core Analysis Center Products
There were no changes in the NGS analysis center products (see Tab. 1) for 2015. Pleaserefer 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 2015. 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).
Changes to the processing software and strategies include:

83

NGS Analysis Center
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 ERP
4 times a day submission for IGU combination• Week 1836 (2015–03–15)

Format change to (internal use only) processing summary file. No effect upon products.

• Week 1848 (2015–06–07)

An SV indexing error reading continuation lines from the RINEX 2.XX format wascorrected. Negligible effect upon products.

• Week 1856 (2015–08–02)

The scripts used to produce the NGS final and rapid products were consolidated
simplifying maintenance. No effect upon products.

• Week 1861 (2015–09–06)

Format change to (internal use only) processing summary file. Corrected phase
continuity detection. Small effect upon products.

• Week 1870 (2015–11–08)

MGEX ANTEX file supersedes GPS and GLONASS only variant. No effect upon
products.

Changes in staff include:• Sungpil Yoon came on–board in February.

• Gerald Mader retired in July after 35 years of U.S. Federal service.
84

5 Acknowledgments

4 Regional Data Center Core Products
During 2015, NGS contributed data from the following sites to the IGS Network in Tab. 2
Table 2: The sites from which NGS contributed data to the IGS Network
Site

Location

ASPA
BARH
BRFT
BRMU
CNMR
GUUG
HNPT
USNO
WES2

Pago Pago, American Samoa
Bar Harbor, ME, USA
Eusebio, Brazil
Bermuda, United Kingdom
Saipan, CNMI, USA
Mangilao, Guam, USA
Cambridge, MD, USA
Washington, DC, USA
Westford, MA,USA

Lat.

Long.

–14.33
44.39
–3.88
32.37
15.23
13.43
38.59
38.92
42.61

–170.72–68.22–38.43–64.70145.74144.80–76.13–77.07–71.49Receiver Type

SystemTRIMBLE NETR5
LEICA GRX1200GGPROLEICA GRX1200PRO
LEICA GRX1200GGPROTRIMBLE NETR5
TRIMBLE NETR5
LEICA GRX1200GGPROASHTECH Z–XII3T
SEPT POLARX4TR

GPS+GLO
GPS+GLO
GPS
GPS+GLO
GPS+GLO
GPS+GLO
GPS+GLO
GPS
GPS+GLOAs a Regional Data Center, NGS also facilitated data flow for the following sites in Tab. 3
Table 3: The sites where NGS facilitated data flow
Site

Location

Lat.

Long.

Receiver Type

System

BJCO
GUAT
ISBA
MANA
WUHN

Cotonou, Benin
Guatemala City, Guatemala
Baghdad, Iraq
Managua, Nicaragua
Wuhan, China

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

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

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, Acting Deputy Director Brett Howe, Acting Division Chief
Steve Hilla, Division Chief Srinivas Reddy and Division Chief Dr. Dan Roman, for theirsupport of this 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).

85

NGS Analysis Center

86

USNO Analysis Center
Technical Report 2015
S. Byram, V. Slabinski, J. Tracey, J. Rohde, C. Hackman
United States Naval Observatory
3450 Massachusetts Avenue Northwest
Washington DC 20392 USA
E–mail: sharyl.byram@usno.navy.mil
Tel: +1–202–762–0185

1 Introduction
The United States Naval Observatory (USNO), located in Washington, DC, USA has
served as an IGS Analysis Center (AC) since 1997, contributing to the IGS Rapid andUltra–rapid Combinations since 1997 and 2000, respectively. USNO contributes a fullsuite of rapid products (orbit and clock estimates for the GPS satellites, earth rotation
parameters (ERPs), and receiver clock estimates) once per day to the IGS by the 1600
UTC deadline, and contributes the full suite of ultra–rapid products (post–processed andpredicted orbit/clock estimates for the GPS satellites; ERPs) four times per day by thepertinent IGS deadlines.
USNO has also coordinated IGS troposphere activities since 2011, producing the IGS Final
Troposphere Estimates and chairing the IGS Troposphere Working Group (IGS TWG).
The USNO AC is hosted in the GPS Analysis Division (GPSAD) of the USNO Earth
Orientation Department (EOD). USNO AC activities, chairing the IGS TWG, and servingon the IGS Governing Board duties were transitioned from Dr. Christine Hackman to
Dr. Sharyl Byram in 2015. Dr. Byram oversees production of the IGS Final Troposphere
Estimates. All GPSAD members, including Dr. Victor Slabinski, Mr. Jeffrey Tracey andcontractor Mr. James Rohde, participate in AC efforts.
USNO AC products are computed using Bernese GPS Software (Dach et al. 2007)1 . Rapid
products are generated using a combination of network solutions and precise point posi1

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

87

USNO Analysis Centertioning (PPP; Zumberge et al. 1997). Ultra–rapid products are generated using network
solutions. IGS Final Troposphere Estimates are generated using PPP.
GPSAD also generates a UT1–UTC–like value, UTGPS, five times per day. UTGPS isa GPS–based extrapolator of VLBI–based UT1–UTC measurements. The IERS (International Earth Rotation and Reference Systems Service) 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, 2015
Figures 1–4 show the 2015 performance of USNO rapid and ultra–rapid GPS products,
with summary statistics given in Tab. 1. USNO rapid orbits had a median weighted RMS(WRMS) of 17 mm with respect to (wrt) the IGS rapid combined orbits. The USNO ultra–
rapid orbits had median WRMSs of 20 mm (24–h post–processed segment) and 38 mm (6–hpredict) wrt the IGS rapid combined orbits. These values are nearly identical to the 2014
values (17, 19 and 38 mm).
USNO rapid (post–processed) and ultra–rapid 6–h predicted clocks had median 172 ps
and 1201 ps RMSs wrt IGS combined rapid clocks, compared to 162 ps and 1603 ps in2014. Note the significant improvement in the ultra–rapid clock predictions.
Table 1: Precision of USNO Rapid and Ultra–Rapid Products in 2014 (All statistics computedwith respect to IGS Combined Rapid Products.)
USNO GPSsatellite orbits

USNO GPS–basedpolar motion estimates

USNO GPS–based
clock estimates

Statistic: median weighted
RMS difference
units: mm

Statistic: RMS difference

Statistic: medianRMS difference
units: ps

dates

1/1/2015 –12/31/2015

88

rapid

17

units: 10–6 arc sec

ultra–rapid
past 24h

6h predict

20

38

rapid

x: 178y: 131

ultra–rapid

rapid

ultra–rapid

past 24h

24h predict

past 24h

6h predict

x: 176y: 159x: 390y: 316172

1201

2 Product Performance, 2015

WRMS, USNO GPS Orbits wrt IGS Rapid Combination
150

mm

100

50

0
0

50

100
ultra-pred

150
200
250
day of year, 2015
ultra-past
rapid

300

350

Figure 1: Weighted RMS of USNO GPS orbit estimates with respect to IGS Rapid Combination, 2015. “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, 2015

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, 2015.

89

USNO Analysis Center

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, 2015

dx, rapid

250

300

350

dy, rapid

Figure 3: USNO rapid polar motion estimates minus IGS Rapid Combination values, 2015.

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, 2015

dx, preddy, past

250

300

350

dx, past

Figure 4: USNO ultra–rapid polar motion estimates minus IGS Rapid Combination values, 2015.

90

2 Product Performance, 2015
Table 2: Precision of USNO Ultra–Rapid GPS+GLONASS Test Products in 2014 (Orbit statistics computed with respect to IGV Combined Ultra–Rapid GPS+GLONASS Products.
Polar motion statistics computed with respect to past–24–hr segment of IGU GPS–only
values.)USNO GLONASS
satellite orbits

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

RMS difference
units: 10–6 arc sec

dates

past 24h

24h predict

past 24hpred 24h

1/1/2015 – 12/31/2015

31

68

x: 270y: 166

x: 471
y: 309USNO rapid polar motion estimates had (x, y) 178 and 131 micro arc sec RMS differences
wrt IGS rapid combined values. USNO ultra–rapid polar motion estimates differed (RMS;x, y) from IGS rapid combined values (aka IGR) by 176 and 159 micro arc sec for the 24–
h post–processed segment. The USNO ultra–rapid 24–h predict–segment values differed(RMS; x, y) from the IGS rapid combined values by 390 and 316 micro arc sec. The
ultra–rapid polar motion values are skewed due to a ∼6 week bias that was a result of aprocessing issue.
The USNO AC began incorporating measurements from the Russian GLONASS GNSS
into processing in 2011 (Byram and Hackman 2012a – 2012b) and has been computing afull set of test rapid and ultra–rapid combined GPS+GLONASS products since 2012.
In 2015, seven–parameter Helmert transformations computed between USNO and IGS
ultra–rapid GPS+GLONASS orbits had median RMSs of 31 and 68 mmfor the 24–h post–processed 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 270 and 166 micro arc sec, respectively. USNO GPS+GLONASS ultra–rapid
24–h predicted polar motion x and y values differed the IGR values, RMS, by 471 and 309
micro arc sec, respectively. The ultra–rapid polar motion values are skewed due to a ∼6
week bias that was a result of a processing issue. These data are shown in Tab. 2/Figs. 5–
6.
The USNO AC acquired Bernese 5.2 GNSS Software in 2013 and plans to release official
AC 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.

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USNO Analysis Center

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, 2015

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, 2015. “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, 2015

dx, pred250

dy, past

300

350

dx, past

Figure 6: Difference between 24–h post–processed polar motion estimates in USNO test ultra–
rapid GPS+GLONASS solution and IGS “IGU” GPS–only ultra–rapid solution, 2015.

92

References

3 USNO AC Conference Presentations/Publications
USNO AC members presentaitons/publications are as follows for 2015:– S. Byram and C. Hackman, “Multi–GNSS Ultra–Rapid Orbit and Clock Products”. 2015
ION Pacific PNT, Honolulu, HI, 2015.
– V. Slabinski, “Lense–Thirring Effect Measurement from LAGEOS Node: Limitationfrom Radiation Forces”. 2015 Meeting of the Division on Dynamical Astronomy, American
Astronomical Society, Pasadena, CA. 2015.

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., U. Hugentobler, P. Fridez, and M. Meindl (eds.). Bernese GPS Software Version
5.0 (User Manual). Astronomical Institute, University of Bern, Bern, Switzerland,
2007.
Webb, F.H. and J.F. Zumberge (eds.). An Introduction to GIPSY/OASIS–II: Precision
Software for the Analysis of Data from the Global Positioning System. JPL internal
publication D–11088, Jet Propulsion Laboratory, Pasadena, California, 1997.
Zumberge, J.F., M.B. Heflin, D.C. Jefferson, M.M. Watkins, and F.H. Webb. Precise Point
Positioning for the Efficient and Robust Analysis of GPS Data from Large Networks.
J. Geophys. Res., 102(B3):5005–17, 199793

USNO Analysis Center

94

WHU Analysis Center
Technical Report 2015
C. Shi, M. Li, Q. Zhao,
X. Dai, C.Wang, Y. Lou, 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 produced withthe latest developed version of the Positioning And Navigation Data Analyst (PANDA)
Software (Liu and Ge 2003; Shi et al. 2008).
In this report we give a summary of the IGS related activities at WHU during the year
2015.

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

95

WHU Analysis Center
network mode or precise point positioning mode, significantly improving the positioning
accuracy of WHU final solutions.

3 WHU Analysis Products
The list of products provided by WHU is summarized in Tab. 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 Ionosphere Activities
Ionosphere TEC is an important parameter for both satellite navigation and scientificstudies of the ionosphere and space weather. TEC determines the first order ionosphere–
induced range error, which is a dominant error source in GNSS navigation solutions.
Measurement–based TEC estimation has gained much attention to meet the needs ofpractical applications. This is especially true since the proliferation of GNSS receivers has
led to the establishment of various global and regional GNSS networks.
WHU are making efforts to boost the ability of processing GNSS data for generating global
ionosphere maps over these years. Recently, WHU have implemented some algorithm forionosphere modeling, such as spherical harmonics model, polynomial functions, Kriging
interpolation and so on. Moreover, some algorithms are proposed to solve the problems
in generating ionosphere maps. For instance, inequality–constrained least squares method
was proposed to eliminate negative VTEC values in global ionosphere maps (Zhang et al.
2013). Meanwhile, the group of WHU use IRI model for providing VTEC values at where
can’t receive GNSS signals in ionosphere modeling to improve VTEC maps. Also, VTEC
maps (from 2010 to 2014) are assessed through comparisons among our products and thoseof IAACs, as shown in Fig. 1. The VTEC maps in IONEX format can be downloaded on
the IGS data center of WHU: ftp://igs.gnsswhu.cn/pub/whu/ionosphere.

96

5 BeiDou Activities

Figure 1: Comparison of GIMs from 2010 to 2014.

A software platform is built for data processing and analysis of ionosphere. This platform
has kinds 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 display of
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 improved by using multithreaded
parallel computing with OpenMP. The time consumption of ionosphere modeling withdifferent number of threads are presented in Fig. 2. It takes approximately 7 and 20
minutes to compute 1–day and 3–day solution, respectively. The efficiency of modelingis promoted nearly 8 times (which is approximately equal to the number of CPU cores).
It’s very helpful for algorithm testing of modeling, fast releasing of ionosphere products,
post–time verification and prediction.

5 BeiDou Activities
According to recent publications, the BeiDou GEO satellites use the orbit–normal mode,
whereas IGSO and MEO satellites employ yaw–steering and orbit–normal yaw attitude
modes (Wang et al. 2013; Guo et al. 2013). As the exact attitude switch mechanism of
IGSO and MEO satellites is not yet released, the reverse kinematic Precise Point Positioning (PPP) method was applied in this study. However, since the recent Precise Orbit
Determination (POD) processing for GPS satellites could not provide suitable products

97

WHU Analysis Center

2 5 0

2 5 0

2 0 0

2 0 0

2 0 0

2 0 0

3 D

3 D

5 0
0

1 0 0
5 0
0

2 8 0

2 8 4

2 8 8

2 9 2

2 9 6

D O Y (2 0 1 3 )

3 0 0

1 5 0
1 0 0
5 0
0

3 D

1 0 0

1 5 0

3 D

1 5 0

o v e r la p (c m )2 5 0o v e r la p (c m )2 5 0o v e r la p (c m )o v e r la p (c m )Figure 2: Time consumption of ionosphere modeling with different numbers of threads.

2 8 0

2 8 4

2 8 8

2 9 2

2 9 6

D O Y (2 0 1 3 )

3 0 0

3 5 5

3 5 9

3 6 3

D O Y (2 0 1 4 )

0 0 2

0 0 6

0 1 0

D O Y (2 0 1 5 )

1 5 0
1 0 0
5 0
0

3 5 5

3 5 9

3 6 3

D O Y (2 0 1 4 )

0 0 2

0 0 6

0 1 0

D O Y (2 0 1 5 )Figure 3: Daily RMS values of day–boundaries (3D) for IGSO (C09 and C06) and MEO (C11and C12) satellites. The yaw–steering attitude mode solution is shown in blue, while
the switch model–based solution in red. The shaded areas illustrate the duration of
the orbit–normal regime.

98

5 BeiDou Activities
for estimating BDS attitude using the reverse PPP because of the special attitude control
switching between the nominal and the orbit–normal mode, a modified processing schema
was proposed by WHU for studying the attitude behavior of the BDS satellites (Dai et al.
2015). In the modified processing, only data before the attitude switch is employed in
the POD processing. This avoids the effect of the inaccurate attitude model on thoseparameters of the satellite orbit and ambiguities which are fixed in the phase center offset
estimation later on. After this modification, yaw–angles of BeiDou satellites are estimatedwith the reverse PPP and a preliminary attitude switch model is established and validated.
In general, the attitude–mode–switch occurs when the Sun elevation is about 4◦ and theactual orientation is very close to its target one (the threshold is empirically set to 5◦ basedon lots of computation and analysis). In a special case that the Sun elevation is about
4◦ , while the yaw angle is empirically larger than 5 but smaller than 20◦ and the absolute value of yaw angle is increasing, the attitude–switch is executed too. Applying thispreliminary attitude switch model to the BeiDou satellite orbit determination observables
gives an improved performance compared with the yaw–steering model (Fig. 3)
Recently, WHU has been providing the BeiDou satellite attitude switch table and a FORTRAN function for the public to process BeiDou data. The table file and FORTRAN
code are placed at the IGS data center of WHU: ftp://igs.gnsswhu.cn/pub/BDS. The
files are described as follows:(1) The table file bds_yaw lists the attitude mode employed by BeiDou IGSO and MEO
satellites from DOY 001 2015, which is updated every day and predicted for two days.
(2) The FORTRAN code bds_yaw.f90 can read the table file bds_yaw to determine the
BeiDou satellite attitude mode, and compute the attitude mode in real time when thetable file is not available.

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WHU Analysis Center

Reference
Liu, J. and M. Ge. A software and its preliminary result of positioning and orbit determination. Wuhan University Journal of Natural Sciences, 8(2):603–609, 2003.
Shi, C., Q. Zhao, J. Geng, Y. Lou, M. Ge, and J. Liu. Recent development of PANDA
software in GNSS data Processing. In: Proceeding of the Society of Photographic
Instrumentation Engineers, 7285, 72851S, 2008. doi:10.1117/12.816261.
Shi, C., Y. Lou, H. Zhang, Q. Zhao, J. Geng, R. Wang, R. Fang, and J. Liu. Seismic
deformation of the M–w 8.0 Wenchuan earthquake from high–rate GPS observations.
Advances in Space Research, 46(2):228–235, 2010.
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 Research,
51(6):988–1000, 2013.
Wang, W., G. Chen, S. Guo, X. Song, and Q. Zhao. A study on the Beidou IGSO/MEO
satellite orbit determination and prediction of the different yaw control mode. Lecture
Notes in Electrical Eng., 245:31–40, 2013. doi:10.1007/978-3-642-37407-4_3.
Guo, J., Q. Zhao, T. Geng, X. Su, and J. Liu. Precise orbit determination for COMPASSIGSO satellites during yaw maneuvers. Lecture Notes in Electrical Eng., 245:41–53,
2013. doi:10.1007/978-3-642-37407-4_4.
Dai, X., M. Ge, and Y. Lou. Estimating the yaw-attitude of BDS IGSO and MEO satellites.
Journal of Geodesy, 89(10):1–14, 2015. doi: 10.1007/s00190–015–0829–x

100

EPN Regional Network
Associate Analysis Center
Technical Report 2015
C. Bruyninx1 , A. Araszkiewicz6 , E. Brockmann2 ,A. Kenyeres4 , R. Pacione8 , W. Söhne3 ,G. Stangl5 , K. Szafranek6 , C. Völksen7
1
2
3
4
5
6
7
8

Royal Observatory of Belgium (ROB), Av. Circulaire 3,1180 Brussels, Belgium, E–mail: C.Bruyninx@oma.be
Bundesamt für Landestopografie swisstopo, Seftigenstrasse 264,
3084 Wabern, Switzerland
Bundesamt für Kartographie und Geodäsie (BKG),
Richard–Strauss–Allee 11, 60598 Frankfurt am Main, Germany
FOMI Satellite Geodetic Observatory, 1592 Budapest,
P.O. Box 585, Hungary
Institute for Space Research, Schmiedlstr. 6, 8042 Graz, Austria
Military University of Technology, Gen. Sylwestra Kaliskiego 2,
00–908 Warsaw, Poland
Bavarian Academy of Sciences and Humanities, Alfons–Goppel–Str. 11,80539 München, Germany
E–GEOS Centro di Geodesia Spaziale (ASI/CGS), Contrada Terlecchia,
75100 Matera, Italy

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

101

EPN Associate Analysis Center
available. The EPN cooperates closely with 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). The EUREF Technical Working Group (TWG) defines the general policy of the
EPN following proposals by the EPN Coordination Group. This Coordination Group consists of the Network Coordinator (managing the EPN Central Bureau (EPN CB)), Data
Flow Coordinator, Analysis Coordinator, Reference Frame Coordinator, Troposphere Coordinator, and Chairs of the Real–time Analysis, Reprocessing, and multi–GNSS Working
Groups. This report gives an overview of the main changes in the EPN during the year2015.

2 Tracking Network and Network Coordination
At the end of 2015, the EPN network consisted of 278 continuously operating GNSS
reference stations (Fig. 1) from which 32% also belong to the IGS. Individual calibrations
were used at 16% of the EPN stations. Sixteen new stations were integrated in the EPN
network in 2015 (see Tab. 1). They are indicated with stars in Fig. 1. The number ofstations providing GPS+GLONASS data increased from 79% to 84% since last year andalready 33% (91) of the EPN stations provide Galileo data.
Table 1: New stations included in the EPN in 2015
ID

Location

Real–Time

Tracked Satellite Systems

Antenna Calibration

BCLN Sant VicencdelsHorts, ESP
BRMF§ Bron, FRA(replaces BRON)CARG Cartagena, ESP
DLF1* Delft, NLD
GOP6* Ondrejov, CZE
GRAC* Caussols, FRA
KNJA Knjazevac, SRB
MATG* Matera, ITA
NPAZ Novi Pazar, SRB
OBE4*§ Oberpfaffenhofen, DEU(replaces OBE2)
PASA Pasaia, ESP
RANT Rantum / Island Sylt, DEU
SABA Sabac, SRB
SUN6 Sundsvall, SWE
TARI Tarifa, ESP
UCAG Cagliari, ITA

Real–Time
Real–TimeGPS GLO GALGPS GLO GAL BDS SBAS

Individual (GEO++)
Type mean

Real–Time
Real–TimeGPS GLO GALGPS GLO GAL BDS QZSS SBASGPS GLO GAL SBASGPS GLO GAL BDS SBASGPSGPS GLO GAL SBASGPS GLOGPS GLO GALIndividual (GEO++)
Individual (GEO++)
Individual (GEO++)
Type mean
Type mean
Type mean
Type mean
Individual (BONN)

102

Real–Time
Real–Time
Real–Time
Real–Time
Real–Time
Real–Time
Real–Time
Real–TimeGPS GLO GAL BDS
Individual (GEO++)GPS GLO SBAS
Individual (GEO++)GPS GLO
Type mean
GPS GLO
Individual (GEO++)GPS GLO GALIndividual (GEO++)GPS GLO GAL
Type mean*: also an IGS station, §: replaced station

2 Tracking Network and Network Coordination
0˚

20˚

˚
40

50

˚

˚

˚

−20

60

−4
0˚

50

˚

˚

40

40˚

30˚

30˚

−20˚

0˚

20˚

Figure 1: EPN tracking stations, status December 2015. (* indicates new stations included in
the network in 2015.)

The EPN CB (http://epncb.oma.be) continued to perform daily data quality checks ofthe daily RINEX v2 data observations, checks of the meta–data of the daily RINEX (v2and v3) data, 2–hourly checks of the meta–data and latency of the real–time EPN data
streams; daily checks of the latency and availability of the hourly and daily RINEX data;
daily updates of the residual position time series of the EPN stations, and regular updatesof several EPN meta–data files such as station site logs files, antenna calibrations files,
ocean loading parameters files, and site coordinates files in support of EPN data analysis.
In 2015, the EPN CB was upgraded to perform additional monitoring tasks:• Check the adherence of the EPN regional broadcasters to the newly released EPN
broadcaster guidelines (see Section 6). This includes new verifications of the meta–data in the broadcasters’ source–tables and cross–checking them with the observation
streams and the site logs. A summary of the results is provided on the EPN ftp site
(ftp://epncb.oma.be/pub/center/broadcasters/COMPARE_BRDC.txt).
• Verify the availability of the new RINEX 3 data in the EPN Data Centers, provide
the information on the EPN CB web site, and inform station managers if data are
missing.
• Verify the compliance between the satellite systems (e.g. GPS, GLONASS, andGalileo) included in the station observations files against the information in the site

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logs. After contacting station managers, the number of disagreements were reduced
from 58 to 10.
EUREF also continued to actively stimulate station managers to provide multi–GNSS
data to submit RINEX v3.02 (or later) data. This activity was supported by the release(Oct. 2015) of new “Guidelines for EPN stations and Operational Centers” (http://epncb.
oma.be/_documentation/guidelines/guidelines_station_operationalcentre.pdf).
At the same time, the EPN CB started evaluating if existing multi–GNSS RINEX (v2and v3) data quality check software is able to detect known historical problems in EPN
stations. Presently, the ideal match has not been found yet. Once it is found, the complete
RINEX data quality web pages of the EPN CB will be modernized. The internal software
and web pages of the EPN CB were already upgraded to switch to the new RINEX v3
standard 9–char station identification codes. Internal software and provided meta–datawere also upgraded to allow the identification of the EPN antennas using their full serial
number (instead of the last 5 digits) from May 2015 on. Finally, in support of the EPN
densification Working Group (see Section 5), a complete new section of the EPN CB
web site (http://epncb.oma.be/_densification) and associated software was created.
Agencies from all over Europe were contacted to gather meta–data from their densification
stations. Presently, more than 550 GNSS stations have already submitted meta–data.

3 RINEX v3
The EUREF Working Group on “Multi-GNSS” stimulates EUREF members to be actively involved in multi–GNSS activities, ranging from the introduction of the RINEX 3
format, the adaptation of the EPN data flow, the development of data quality checks tomulti-GNSS data analysis. End of 2015, about 90 EPN stations are delivering RINEX v3
data (compared to 58 end of 2014). The majority of stations deliver data in format 3.02
(16 stations deliver data still in format 3.01). Additionally, about 15 stations in Europe
contribute data to the IGS MGEX. The EPN Regional Data Centers (RDCs) at BKG and
OLG follow the IGS strategy concerning acceptance of RINEX v3 observations. Station
managers have been encouraged to submit RINEX v3 files additionally to RINEX v2 files.
Both EPN RDCs are accepting RINEX v3 data with long as well as short files names. The
files with the long names are stored in the “regular” download directories together withRINEX v2 files. RINEX v3 files with short names are kept separately until the IGS andEPN DC decide to rename to the long names and move them to the RINEX 2 directories.
An important requirement for the routine utilization of the RINEX v3 observation files isthe availability of quality check software. Working Group members are actively contributing to this effort by developing and using two software packages: G-Nut/Anubis [1.2.1](Vaclavovic and Dousa 2015) and BNC [2.12] (Weber and Mervart 2009). Both allow
RINEX header manipulation and the generation of data quality statistics. Several groups
are running these programs and make the results available in form of plots available on their104

4 Data Analysis
web pages, e.g. http://www.pecny.cz/GOP/index.php/gnss/data-center/euref-rnx3,
http://www.swisstopo.admin.ch/swisstopo/geodesy/pnac/html/en/anubis_monitor_
r3.html. At the 9th Workshop of the EUREF Analysis Centers (ACs), held in October
2015 in Bern, several presentations underlined the increasing complexity when analyzing multi-GNSS data. A technical introduction was given to the ACs on how to process
multi–GNSS data using BSW 5.2 (Dach et al. 2015).

4 Data Analysis
4.1 Positions
In 2015 the number of ACs submitting routine solutions did not change: 16 (from 18
existing) ACs deliver SINEX solutions contributing to the weekly EPN combination. The
GOP AC focuses on the EPN reprocessing activities. The DEO AC does not submit its
solutions anymore since 2009, but is planning to restart routine analysis in 2016. Fourteen ACs analyze both GPS and GLONASS data with Bernese GNSS Software 5.2 (Dachet al. 2015), the two remaining ACs use Bernese GNSS Software 5.0 and GIPSY–OASIS
6.2 software. The routine solutions are combined by the Analysis Combination Center(ACC) run by a consortium of the Military University of Technology and the Warsaw
University of Technology. All combinations are performed with Bernese 5.2. The weekly
and daily final positions are delivered on the basis of 16 ACs solutions, while the rapid
daily and ultra–rapid solutions use input from respectively ten and three ACs. Other ACs
are encouraged to submit rapid and ultra–rapid solutions to strengthen the reliability ofthese products. Only stations processed by at least three ACs are used in the final daily
and weekly solutions, which enables the detection of outliers and increases the reliabilityof the solutions. Exceptions are made for a few new stations: in the beginning of their
lifetime it is accepted that they are processed by less than three ACs. Prior to the combination process, the SINEX files provided by the different ACs are automatically checkedagainst possible metadata inconsistencies (e.g. antenna types and calibration models, receiver types) and problematic stations are excluded from the combination. The shortreports from the final combinations are distributed using EUREF and LAC mail system (see http://epncb.oma.be/_newseventslinks/mails.php), while the full versionof these reports is available at ftp://epncb.oma.be/pub/product/combin/WWWW. The
EPN ACC webpage (http://www.epnacc.wat.edu.pl) shows results of the final, rapid
and ultra–rapid combinations. For the final combination, it shows for all EPN stations
the agreement between the AC solutions in the horizontal and vertical components, theHelmert transformation parameters (Fig. 2) of all input solutions wrt the combined solution, and time series of all station input residuals w.r.t. to the positions resulted from the
combination.
The long–term combination, performed every 15 weeks, is compared to the national realizations of ETRF in the countries. The difference plots, available under http://epncb.

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EPN Associate Analysis Center

5

ZTD bias [mm]

2.5

0

-2.5

Stdev of ZTD bias [mm]

-5
10

7.5

5

2.5

0
1000

1200

1400

1600

1800

GPS Week

Analysis Centres (Click to hide)
ASI

BEK

BKG

COE

DEO

GOP

IGE

IGN

LPT

MUT

NKG

OLG

RGA

ROB

SGO

SUT

UPA

WUT

Figure 2: Agreement (RMS of Helmert transformation) between each weekly LACs solution andthe weekly EPN combined solution.

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4 Data Analysis
oma.be/_productsservices/coordinates/img/ETRF_EPN_HOR.JPG and http://epncb.
oma.be/_productsservices/coordinates/img/ETRF_EPN_UP.JPG show nicely the homogeneous implementation of the various ETRF realizations in Europe.

4.2 Troposphere
Beside station coordinates, the 16 ACs also submit ZTD parameters on a routine basis in
SINEX–Tro format. Thirteen ACs are also submitting horizontal gradients. The ZTDs
and horizontal gradients are delivered with a sampling rate of 1 hour, on a weekly basis but
in daily files. As regard as the troposphere mapping function, five of the 16 ACs use theVienna Mapping Function, ten the Global Mapping Function and one the Niell Mapping
Function. The tropospheric combination is based on a generalized least square method,
following Pacione et al. 2011. A report of the weekly combination is distributed using
the EUREF LAC mail system. Thanks to the growing computation power, the individualACs enlarged their networks in 2015. Even though all EPN stations are processed by atleast three ACs (with exception described above), thus improving the outlier detection,in 2015 ZTD estimates are provided by more than three ACs for about 260 stations,by two ACs for about 11 stations and by one ACs for about 6 stations. The weekly
mean bias (Fig. 3–top) and the related standard deviation (Fig. 3–bottom) (available
at http://www.epncb.oma.be/_productsservices/sitezenithpathdelays) give insight
into the agreement of the individual solutions with respect to the combined solution. The
time series in Fig. 3 are based on EPN Repro1 solutions from GPS week 0834 to 1407
and on operational solutions afterwards. The jump in the standard deviation time series(Fig. 3) occurred at GPS week 1800 is related to the use of a different combination software
starting from that GPS week, when the combination moved from BKG to ASI/CGS.
Alongside the ZTD combination, inter–technique comparisons have been added to the website of the EPN CB. The time series of EPN ZTD differences with respect to radiosonde–
derived ZTDs are computed for more than 180 stations. For the stations considered, thehorizontal distance between radiosonde and GNSS location is varying from less than 1 km
up to 75 km. The standard deviation of the differences is between 4 and 20 millimeters
ZTD, with worse agreement if the distance is long. Moreover, for each EPN site plots
showing monthly mean of ZTD values from 1996 to present are available.

4.3 Reprocessing
The Working Group “EPN Reprocessing” continued its effort in providing a new solution
for the entire EPN based on reprocessed orbits (IGb08), clock products and ERP. The
reprocessing activity covered all available data of the EPN spanning the years 1996 until
2013. The analysis was carried out either with the software BERNESE 5.2, GAMIT 10.5
or GIPSY 6.2. First daily solutions have already been provided in spring 2015 by the fivedifferent ACs involved in this activity, either analyzing the complete network (three ACs)

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EPN Associate Analysis Center
Scale of Helmert Transformation
Final results after station exclusion

0.004 ppm

0.002 ppm

0 ppm

-0.002 ppm-0.004 ppm
1500

1600

1700

1800

1900

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

GPS week
EPN ACC WEBPAGE

Figure 3: Top: Weekly mean biases of ACs individual ZTD contributions w.r.t. the combined
ZTD solution (mm ZTD). Bottom: Standard deviation of weekly mean biases of ACs
individual ZTD contributions w.r.t. the combined ZTD solution (mm ZTD).

or subnetworks (two ACs). Some ACs provided even different solutions that were basedon different strategies. These different solutions were tested by the ACC and feedback
was given to the working group. In order to homogenize the different solutions, it wasnecessary for some ACs to reprocess the solution again securing to a large extend that thesame standards and conventions have been used in the solutions. In contrast to the IGS
network, the EPN uses not only type mean but also individual antenna calibration models.
Finally, in the end of 2015, the computations of the daily solutions have been finished. The
next step requires now the combination of the five different solutions and this process will
be conducted by the ACC at the Military University of Warsaw. Combined products of thefive networks are expected in February 2016, while the multi–year–solution will hopefully
be ready by the next EUREF symposium in June 2016. In parallel a first troposphericcombined solution for the period 1996–2013 has been carried out. This combined solution
is based on all the available homogenously reprocessed contributions delivered by the fiveACs. It offers the possibility to assess each contribution and in order to provide a GNSS
climate data record with the high potential for climate monitoring over Europe.

5 Densification of the IGS and EPN
Based on the EPN combined weekly SINEX solutions (back to mid–1996), a multi–year
EPN position and velocity solution is maintained as the densification of the IGS realization of the ITRS in Europe. This solution is computed with the CATREF software108

6 Stream and Product Dissemination
Altamimi et al. 2007 and updated each 15 weeks, in accordance with the long–term combination (Section 4.1). Up to GPS week 1709, the multi–year solution was tied to IGS08,
since that date the IGb08 was used. This reference frame alignment is based on the minimum constraint approach and the consistency of the frame realization is checked. WhenITRF2014 and the EPN–Repro2 products will become available, the multi–year EPN solution will be updated to be compliant with the latest standards. The EPN multi–year
product files (including a discontinuity table and associated residual position time series)
are available at ftp://epncb.oma.be/pub/station/coord/EPN/. More details can befound in http://epncb.oma.be/_productsservices/coordinates. The densification of
the EPN aims at providing a dense continental–scale homogeneous station position andvelocity field to support the better realization of the ETRS89 over the non–stable regionsof Europe (e.g. the Mediterranean). This activity is done in close co–operation with thegeophysical community which will provide input for the tectonic interpretation and modelling. The densification activity is done in the frame of a Working Group lead by the
EPN Reference Frame Coordinator. In that frame, EUREF combines the weekly SINEX
solutions provided by European countries for their dense national active GNSS networks
with the weekly EPN SINEX solution. Then, all available weekly combined solutions arestacked to obtain a consistent cumulative position/velocity solution. Both combinations(the weekly and the multi–year) are done using the CATREF software using exactly thesame approach and parameters as for the generation of the EPN IGb08 densification ensuring full consistency from the global to local level. The total number of stations includedin the EPN densification exceeded 2900 as of December 2015. Two contributions (IGN,
France and BIGF, UK) are global solutions and therefore the EPN densification shallbe considered as a global solution. Beyond the active networks a long term (1996–2015)
Repro–2 campaign product of CEGRN (Central European GPS Geodynamic Network) has
also been integrated. We devoted significant efforts to collect, harmonize and maintainstation meta–data based on log files. Relying on the experiences, tools and web services wedeveloped for EPN, dedicated web pages had been installed to handle EPN densification
meta–data and products (http://www.epncb.oma.be/_densification). 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. 2015).

6 Stream and Product Dissemination
As announced in last year’s report, guidelines for the EPN broadcasters were prepared andreleased in 2015. For this, the guidelines for EPN Data Centers were extended (see http://epncb.oma.be/_documentation/guidelines/guidelines_data_centres.pdf). A new
section 4 explains in detail the role and content of the broadcaster sourcetable withthe three record types CAS, NET and STR. In particular, the mountpoint data fields
should be as consistent as possible between the regional as well as the local broadcasters.

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The process of homogenization of the three EUREF regional broadcasters (RBs) locatedat ASI (http://euref-ip.asi.it:2101/), BKG (http://www.euref-ip.net) and ROB(http://www.euref-ip.be/) continued in 2015. Besides the real–time monitoring of thestatus of each mountpoint at the three RBs (green–red differentiation), another tool, developed by the EPN CB, is testing the currently available observation types used in thestreams against the –static– sourcetable entries. This way, the providers can see, e.g., if
any of the message types have been lost or if update rates have been changed. Moreover,meta–data included in the sourcetables is checked against the most recent site logs. Finally, a script checking antenna height and antenna type contained in the data stream
against the entries in the most recent skeleton file is running in a test mode at BKG.

References
Altamimi, Z., P. Sillard, and C. Boucher. CATREF software: Combination and analysisof terrestrial reference frames. LAREG, Technical, Institut Géographique National,
Paris, France, 2007.
Dach, R., S. Lutz, P. Walser, and P. Fridez. (Eds.) Bernese GNSS Software 5.2. http://www.bernese.unibe.ch/docs/DOCU52.pdf, 2015.
Kenyeres, A., T. Horvath, A. Caporali, A. Baron, F. De Doncker, B. Drosčak, P. Franke,
B. Garayt, I. Georgiev, M. Gianniou, D. Hansen, L. Huisman, I. Jumare, J. Nagl,
P. Pihlak, G. tangl, M. Valdes, K. Szafranek, M. Figurski, M. Ryczywolski. Regional
Densification of the ITRF through the Integration of the National Active GNSS Network Products. Presented at EGU 2015, 13–17 April, 2015, Vienna, Austria, 2015.
Pacione, R., B. Pace, S. de Haan, H. Vedel, R. Lanotte, and F. Vespe. Combination
Methods of Tropospheric Time Series. Adv. Space Res., 47 (2):323–335, 2011. DOI:
10.1016/j.asr.2010.07.021, 2011.
Vaclavovic, P. and J. Dousa. G–Nut/Anubis – open–source tool for multi–GNSS data
monitoring. In: IAG Symposia Series, Springer, Vol. 143, 2015. (accepted.) Springer,
Vol. 143, 2015, accepted.
Völksen, C., A. Araszkiewicz, R. Pacione, B. Pace, and K. Szafranek. The Benchmark Testof the EPN–Repro2 campaign. Presented at EUREF Symposium, Vilnius, Lithuania,
June 3–7, 2014.
Weber, G. and L. Mervart. The BKG Ntrip Client (BNC) Report on EUREF Symposium2007 in London. Mitteilungen des Bundesamtes fuer Kartographie und Geodaesie,
Band 42, Frankfurt, 2009.

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SIRGAS Regional Network
Associate Analysis Center
Technical Report 2015
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 396 continuously operating GNSS
stations (Fig. 1). It comprises two hierarchy levels (Brunini et al. 2012): a core network(SIRGAS–C) providing the primary link to the global ITRF; and national reference networks (SIRGAS–N) improving the geographical density of the reference stations to ensure
the accessibility to the reference frame at national and local levels. The SIRGAS reference
stations are processed by 10 SIRGAS Processing Centers (Mackern and Brunini 2015):• Deutsches Geodätisches Forschungsinstitut der Technischen Universität München(Germany), Sánchez et al. 2015a• 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. 2015
• CPAGS–LUZ: Centro de Procesamiento y Análisis GNSS SIRGAS de la Universidad
del Zulia (Venezuela), Cioce et al. 2015
• IBGE: Instituto Brasileiro de Geografia e Estatistica (Brazil), Da Silva et al. 2015
• IGAC: Instituto Geográfico Agustín Codazzi (Colombia)• IGM–Cl: Instituto Geográfico Militar (Chile), Parra 2015111

SIRGAS Associate Analysis Center• IGN–Ar: Instituto Geográfico Nacional (Argentina)• INEGI: Instituto Nacional de Estadística y Geografía (Mexico)• SGM: Servicio Geográfico Militar (Uruguay)

The SIRGAS processing centers 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
values (SIRGAS does not estimate these parameters), and positions for all stations areconstrained to ±1 m (to generate the loosely constrained solutions in the SINEX format).
INEGI (Mexico) and IGN–Ar (Argentina) employ the software GAMIT/GLOBK (Herring
et al. 2010); the other local processing centers use the Bernese GPS Software V. 5.2(Dach et al. 2015). The processing standards applied at present are described in Sánchez
et al. 2015a. The individual solutions are combined by the SIRGAS Combination Centers
operated by DGFI–TUM (Sánchez 2015a) and IBGE (Mantovani et al. 2015). In charge of
the IGS Regional Network Associate Analysis Center for SIRGAS (IGS RNAAC SIRGAS),DGFI–TUM 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, Sánchez et al. 2015a;• combining the core network with the national reference networks (Fig. 2), Sánchez
2015a;• ensuring that the SIRGAS processing strategy meets the IERS standards and IGS
guidelines (Fig. 3), Sánchez 2015b;• developing strategies to guarantee the reliability of the reference frame over time,
this includes• estimation of the reference frame kinematics (Fig. 4), Sánchez 2015c;• evaluation of the seismic impacts on the reference frame (Fig. 5), Sánchez et al.
2015b;• modelling crustal deformation in the SIRGAS region (Fig. 6), Drewes and Sánchez
2015, Sánchez and Drewes 2015;• 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.

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1 Introduction

Figure 1: Core and national networks within the SIRGAS Reference Frame.

113

SIRGAS Associate Analysis Center(a) Time series of the RMS of the station position residuals for each analysis centerwith respect to the SIRGAS weekly combined solutions. Outliers in the LUZ–VE series
for the East component have to be further studied.

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1 Introduction(b) Time series of the RMS of the station position residuals for each analysis centerwith respect to the IGS weekly final solutions. This comparison allows to assess theaccuracy of the individual solutions: about ±2 mm in North and East, and ±5 mm
in the vertical component. Outliers in the IGM–CL and LUZ–VE series have to befurther studied.

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SIRGAS Associate Analysis Center(c) Standard deviation of station positions after solving the individual solutions withrespect to the IGS reference frame. These values represent the formal errors of theindividual solutions. Analysis Centers applying the Bernese GNSS Software achieve
values of about ±1.6 mm, while Analysis Centers using GAMIT/GLOBK have valuesof ±2.0 mm.

(d) Quality evaluation of combined SIRGAS solutions: The coordinate repeatability of
the weekly combinations provides an estimate for the accuracy (internal consistency)of the weekly combinations of about ±1.2 mm in the horizontal component and about±3.5 mm in the vertical one. The RMS values derived from the time series for station
positions and with respect to the IGS weekly coordinates indicate that the reliabilityof the network (external precision) is about ±1.5 mm in the horizontal position and±4.0 mm in the height. The differences with respect to the IBGE weekly combinations
are at the expected level (less than 0.5 mm).

Figure 2: Quality control of the individual solutions delivered by the SIRGAS Analysis Centers
as well as of the combined solutions computed by the IGS RNAAC SIRGAS (GPSweeks 1810 – 1865)

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1 Introduction

Figure 3: Inventory for the second SIRGAS reprocessing. It is necessary to compute all daily
and weekly normal equations of the reference frame applying the new IERS and IGS
guidelines. This inventory was performed from 1997 until 2014; as an example, the
RINEX availability for the year 2014 is shown.

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SIRGAS Associate Analysis Center

Figure 4: Multi-year solution SIR15P01. It covers the time span from 2010.2 to 2015.2, includes
303 stations and refers to the IGb08, epoch 2013.0. Its accuracy is estimated to be±1.8 mm in the horizontal position, ±3.5 mm in the vertical position, ±1.0 mm/a inthe horizontal velocities and ±1.2 mm/a in the vertical velocities.

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Figure 5: Station discontinuities (left) and post–seismic relaxation movements (right) identified
in the SIRGAS region from March 2010 to April 2015.

Figure 6: Post–seismic deformation model VEMOS2015 and comparison with the pre–seismic
model VEMOS2009.

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SIRGAS Associate Analysis Center2 Acknowledgements
The operational infrastructure and results described in this report are only possible thanks
to the active participation of many Latin American and Caribbean colleagues, who not
only make the measurements of the stations available, but also operate SIRGAS Analysis
Centers processing the observational data on a routine basis. This support and that provided by the International Association of Geodesy (IAG) and the Pan–American Institutefor Geography and History (PAIGH) is highly appreciated. More details about the activities and new challenges of SIRGAS, as well as institutions and colleagues working on canbe found at www.sirgas.org.

References
Brunini, C., H. Drewes, S.M.A. Costa, and V. Mackern. Improved analysis strategy andaccessibility of the SIRGAS Reference Frame. IAG SYMPOSIA, 136:3–10, 2012. doi:
10.1007/978-3-642-20338-1_1
Cioce, V., E. Wildermann, G. Royero, R. Ceballos, D. Espinoza, and R. Morales. Actividades del Centro de Procesamiento y Análisis GNSS SIRGAS de la Universidad
del Zulia, periodo 2014–2015. Presented at the Symposium SIRGAS 2015, Santo
Domingo, Dominican Republic, November 18–20, 2015.
Da Silva, A.L., M.A. De Almeida Lima, S.M.A. Costa, G.L. Mantovani. Centro de Procesamiento SIRGAS – IBGE: actividades realizadas en el periodo 2014–2015. Presented
at the Symposium SIRGAS 2015, Santo Domingo, Dominican Republic, November
18–20, 2015.
Dach, R., S. Lutz, P. Walser, and P. Fridez (eds.). Bernese GNSS Software Version 5.2.
Astronomical Institute, University of Bern, 2015.
Drewes, H. and L. Sánchez. Post–seismic crustal deformations after the 2010 earthquakes
in the SIRGAS region. Presented at the Symposium SIRGAS 2015, Santo Domingo,
Dominican Republic, November 18–20, 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.
Mackern, M.V. and C. Brunini. Evolución de la red SIRGAS–CON y acciones dentro delGrupo de Trabajo I Presented at the Symposium SIRGAS 2015, Santo Domingo,
Dominican Republic, November 18–20, 2015.
Mantovani, G.L., W.C. Machado, A.L. Da Silva, S.M.A. Costa, M.A. De Almeida Lima,
and Junior N.J. De Moura. Resultados del Centro de Combinación SIRGAS del IBGE

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References
para el periodo de 2014 a 2015. Presented at the Symposium SIRGAS 2015, Santo
Domingo, Dominican Republic, November 18–20, 2015.
Moya, J., S. Bastos, A.L. Garita, and J.F. Valverde. Resultados del centro oficial deprocesamiento SIRGAS de Costa Rica. Presented at the Symposium SIRGAS 2015,
Santo Domingo, Dominican Republic, November 18–20, 2015.
Parra, H. Centro oficial de procesamiento SIRGAS IGM–Chile (IGM–CL) Presented
at the Symposium SIRGAS 2015, Santo Domingo, Dominican Republic, November
18–20, 2015.
Sánchez, L. Recent activities of the IGS Regional Network Associate Analysis Centre for
SIRGAS (IGS RNAAC SIRGAS). Presented at the Symposium SIRGAS 2015, Santo
Domingo, Dominican Republic, November 18–20, 2015a.
Sánchez, L. SIRGAS regional stations available for the second reprocessing of the SIRGAS reference frame. Presented at the Symposium SIRGAS 2015, Santo Domingo,
Dominican Republic, November 18–20, 2015b.
Sánchez, L. Kinematics of the SIRGAS Reference Frame. Presented at the Symposium
SIRGAS 2015, Santo Domingo, Dominican Republic, November 18–20, 2015c.
Sánchez, L. and H. Drewes. Post–seismic crustal deformations after the 2010 earthquakes
in Latin America. Presented at International Union of Geodesy and Geophysics General Assembly 2015, Prague, Czech Republic, June 22 – July 2, 2015.
Sánchez, L., H. Drewes, C. Brunini, and M.V. Mackern. Martínez–Díaz W.: SIRGAS core
network stability. IAG Symposia 143, 2015a. doi: 10.1007/1345_2015_143.
Sánchez, L., H. Drewes, C. Brunini, V. Cioce, D. Cisneros, L. Gasca, H. Guagni, V. Mackern, J. Moya, I. Parada, P. Sandoval, and O. Suárez. SIRGAS: the core geodetic
infrastructure in Latin America and the Caribbean. Presented at International Unionof Geodesy and Geophysics General Assembly 2015, Prague, Czech Republic, June
22–July 2, 2015b.
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.

121

SIRGAS Associate Analysis Center

122

Part III
Data Centers

123

Infrastructure Committee
Technical Report 2015
I. N. Romero
ESA/ESOC, Germany
E–mail: Ignacio.Romero@esa.int

1 Summary of Activities in 2015
The Infrastructure Committee consists of the members listed in Tab. 1. The Infrastructure
Committee worked on the implementation of the RINEX 3 transition plan drafts andrevised it as needed after more revisions:• Collaborated with the Network Coordinator (NC) to create all the IGS station long
names and adapt the SLM.
• Collaborated with the Data Centers (DC) to accept long name RINEX 3 files into
the regular data file repository and to rename files.
The Infrastructure Committee also helped to bring into the IGS network two new stationsin Hong Kong (HKSL, HKWS) and helped the NC to introduce new stations from Taiwan,
Macau and Malaysia. We collaborated with the Data Centers on the XML Metadata
exchange project.
Table 1: Current Members: re–appointed in December 2013 for terms up to December 2015
Name

Affiliation

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

ROB
UNAVCO
GA
ESOC
NRCan
BKG

125

Infrastructure Committee
Table 2: Ex–officio Members
Name

Affiliation

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

Central Bureau
Analysis Coordinator
Real time Working Group Chair
Reference Frame Coordinator
Data Center Working Group Chair
Clock Products Coordinator

2 Activity plan in 2016
• Continue supporting the implementation of the RINEX 3 transition plan

• Continue supporting the DC WG on the XML Metadata exchange project• Participate in the IGS Workshop• To support the Network Coordinator by having telecons between the IC Chair andthe NC, so as to coordinate the inclusion of all used stations into the IGS network
to return to "one network" and to more effectively monitor the Data Center file
holdings.

126

CDDIS Global Data Center
Technical Report 2015
C. NollNASA Goddard Space Flight Center
Code 690.1, Greenbelt, MD 20771, USA
E–mail: Carey.Noll@nasa.gov

1 Introduction
The Crustal Dynamics Data Information System (CDDIS) is NASA’s data archive andinformation service supporting the international space geodesy community. For over 35
years, the CDDIS has provided continuous, long term, public access to the data (mainly
GNSS1 , SLR2 , VLBI3 , and DORIS4 ) and products derived from these data required fora variety of science observations, including the determination of a global terrestrial reference frame and geodetic studies in plate tectonics, earthquake displacements, volcano
monitoring, Earth orientation, and atmospheric angular momentum, among others. The
specialized nature of the CDDIS lends itself well to enhancement to accommodate diverse
data sets and user requirements. The CDDIS is one of NASA’s Earth Observing System
Data and Information System (EOSDIS) Distributed Active Archive Centers (DAACs);
EOSDIS data centers serve a diverse user community and are tasked to provide facilities
to search and access science 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 2015 are summarized inthis report; this report also includes any recent changes or enhancements made to the
CDDIS.
1

Global Navigation Satellite System
Satellite Laser Ranging
3
Very Long Baseline Interferometry
4
Doppler Orbitography and Radiopositioning Integrated by Satellite
2127CDDIS Data Center

2 System Description
The CDDIS archive of IGS data and products are accessible worldwide through anonymous
ftp (ftp:/cddis.gsfc.nasa.gov). The CDDIS has also implemented web–based access tothe archive (http:/cddis.gsfc.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 system is fully redundant with primary and secondary/failoversystems. Each system utilizes a distributed functionality (incoming, outgoing, processing,database, and map servers) and is configured with a local backup system as well as afull backup system located in a third building at GSFC. The archive is equipped with amulti–Tbyte RAID storage system and is scaled to accommodate future growth. All ftp
and web access is performed on the outgoing servers. Data centers, stations, and analysis
centers push files to the CDDIS incoming servers. Processing of incoming files for theon–line archive is performed in a separate environment that also includes database servers
for managing metadata extracted from incoming data.

3 Archive Content
As a global data center for the IGS, the CDDIS is responsible for archiving and providing access to GNSS data from the global IGS network as well as the products derived
from the analyses of these data in support of both operational and working group/pilot
project activities. The CDDIS archive is approximately 15.1 Tbytes in size of which
14.5 Tbytes (95%) is devoted to GNSS data (13.5 Tbytes), products (1 Tbytes), andancillary information. All data and products are accessible through subdirectories of
ftp:/cddis.gsfc.nasa.gov/gnss.

3.1 GNSS Tracking Data
3.1.1 Operational Data Archive
The user community has access to GNSS data available through the on–line global data
center archives of the IGS. Over 70 operational and regional IGS data centers and station
operators make data (observation, navigation, and meteorological) available in RINEX format to the CDDIS from selected receivers on a daily, hourly, and sub–hourly basis. The
CDDIS also accesses the archives of the other three IGS global data centers, Scripps Institution of Oceanography (SIO) in California, the Institut Géographique National (IGN) in
France, and the Korea Astronomy and Space Science Institute (KASI) to retrieve (or receive) data holdings not routinely transmitted to the CDDIS by an operational or regional128

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

Sample Rate

Data Format

Available On–line

Daily GNSS
Hourly GNSS
High–rate GNSS
Satellite GPS

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

RINEX and compact RINEX
Compact RINEX
Compact RINEX
Compact RINEX

Since 1992
10+ years
Since May 2001
Since 2002

Table 2: GNSS Data Archive Summary for 2015
Data Type
GNSS

Average #Sites/Day# Unique
Sites

AverageVol./Day

Total
Vol./Year#
Files

Directory
Location

Daily
HourlyHigh–rate

485
325
185

566
384
224

1,300 Mb
485 Mb3,100 Mb

400 Gb140 Gb765 Gb

735K
6,705K
9,750K/gnss/data/daily/gnss/data/hourly/gnss/data/highrate#: Numberdata center. Tab. 1 summarizes the types of IGS operational GNSS data sets archived at
the CDDIS.
Data, in RINEX V2.10 or V2.11 format, from GPS and GPS+GLONASS receivers arearchived within the main GNSS directory structure /gnss/data.
The CDDIS archives four major types/formats of GNSS data, all in RINEX format, as
described in Tab. 1. Daily RINEX data are quality–checked, summarized, and archived to
public disk areas in subdirectories by year, day, and file type; the summary and inventory
information are also loaded into an on–line database. Over 177K daily station days from566 distinct GNSS receivers were archived at the CDDIS during 2015. A complete listof daily, hourly, and high–rate sites archived in the CDDIS can be found in the yearlysummary reports at URL ftp:/cddis.gsfc.nasa.gov/reports/gnss.
Within minutes of receipt, the hourly GNSS files are archived to subdirectories by year,
day, and hour. Although these data are retained on–line, the daily files delivered at theend of the UTC day contain all data from these hourly files and thus can be used in lieu
of the individual hourly files. A total of 384 unique hourly sites (over 6.7 million files)
were archived during 2015.
High–rate (typically 1–second sampling) GNSS data are archived in files containing fifteen
minutes of data and in subdirectories by year, day, file type, and hour. Many of these data
files are created from real–time streams. Data from 224 unique high–rate sites (nearly 10
million files) were also archived in the CDDIS in 2015.

129

CDDIS Data Center
The CDDIS generates global broadcast ephemeris files (for both GPS and GLONASS) on
an hourly basis. These files are derived from the site–specific ephemeris data files for eachday/hour. These files are appended to a single file that contains the orbit information
for all GPS and GLONASS satellites for the day up through that hour. The merged
ephemeris data files are then copied to the day’s subdirectory within the hourly data filesystem. Within 1–2 hours after the end of the UTC day, after sufficient station–specificnavigation files have been submitted, this concatenation procedure is repeated to create
the daily broadcast ephemeris files (both GPS and GLONASS), using daily site–specificnavigation files as input. These daily broadcast files are then copied to the corresponding
subdirectory under the daily file system. Users can thus download this single, daily (orhourly) file to obtain the unique navigation messages rather than downloading multiple
broadcast ephemeris files from the individual stations.
The CDDIS generates and updates “status” files, (/gnss/data/daily/YYYY/DDD/YYDD.status)that summarize the holdings of daily GNSS data. These files include a list of stations.
The archive status files of CDDIS GNSS data holdings reflect timeliness of the data delivered as well as statistics on number of data points, cycle slips, and multipath. The
user community can thus view a snapshot of data availability and quality by checking thecontents of such a summary file.
3.1.2 RINEX V3 (MGEX) Archive
During 2015 the CDDIS continued the archiving of data in RINEX V3 format frommulti–GNSS receivers participating in the Multi–GNSS Experiment (MGEX) as wellas products derived from the analysis of these data. The data include all available
multi–GNSS signals (e.g., Galileo, QZS, SBAS, and BeiDou) in addition to GPS andGLONASS. The data are currently archived in a campaign directory structure at CDDIS(/gnss/campaign/mgex/data). The summary of the MGEX data holdings at the CDDIS isshown in Tab. 3. Daily status files are also provided that summarize the MGEX data holdings; however, data quality information, generated for operational GNSS data holdings,
is not available through the software used by CDDIS to summarize data in RINEX V3
format. CDDIS continues to investigate and evaluate software capable of providing datasummary/QC information for RINEX V3 data. Products derived in support of MGEX by
three to six ACs are also available through the CDDIS (/gnss/products/mgex/WWWW).
Table 3: GNSS MGEX Data Archive Summary for 2015
Data Type
GNSS

Average #Sites/Day# Unique
Sites

AverageVol./Day

Total
Vol./Year

#
Files

Daily
HourlyHigh–rate

110
50
45

137
58
52

35.1K
17.1K
13.6K

710 Mb190 Mb2,300 Mb

/gnss/data/campaign/mgex/daily/gnss/campaign/mgex /data/hourly
740 Gb /gnss/campaign/mgex /data/highrate#: Number

130

Directory
Location3 Archive Content
The CDDIS also added a merged, multi–GNSS broadcast ephemeris file containing GPS,GLONASS, Galileo, BeiDou, QZSS, and SBAS ephemerides from MGEX stations. Thisfile, generate by colleagues at the Technical University in Munich (TUM) and Deutsches
Zentrum für Luft– und Raumfahrt (DLR), is similar to the daily and hourly 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 is named brdmDDD0.YYp.Z and found 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).
In order to promote usage of RINEX V3 and allow users (and data centers) to become
familiar with the format and file naming conventions, several data providers are now
delivering data from MGEX stations using both RINEX V2 and V3 filename formats. The
CDDIS established a daily subdirectory for the files containing observation or navigation
data files using the RINEX V3 filename format within the daily MGEX directory structure(/gnss/data/campaign/mgex/daily/rinex3/YYYY/DDD/crx).
Colleagues at TUM and DLR are also providing GPS and QZSS CNAV (civilian navigation) data on an operational basis within MGEX. These messages are collected from a sub–network (ten stations) of MGEX stations and are provided in a merged daily file 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).
Colleagues at DLR and the Chinese Academy of Sciences (CAS) provide differential
code biases (DCBs) products for the MGEX campaign. This product was derived from
GPS, GLONASS, Galileo, and BeiDou ionosphere–corrected pseudorange differences andis available in the bias SINEX format. DLR has provided two files per year, daily satellite
and daily satellite and station biases, for the 2013–2016 time period in CDDIS directory/gnss/products/mgex/dcb; CAS provides daily files. Additional details on the DCB product are available in IGSMail message 6868 sent in February 2015 and message 7173 sentin October 2015. Both products use the new RINEX V3 file naming convention.

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). Tab. 4 summarizes
the GNSS products available through the CDDIS. The CDDIS currently provides on–line
access through anonymous ftp to all IGS products generated since the start of the IGS Test
Campaign in June 1992 in the file system /gnss/products; products from GPS+GLONASS
products are available through this filesystem. Products derived from GLONASS data
only continued to be archived at the CDDIS in a directory structure within the file system/glonass/products.

131

CDDIS Data Center
Table 4: GNSS Product Summary
Product Type

Number of ACs/AACs

VolumeDirectory

Orbits, Clocks,
ERP, Positions

14+Combinations

1.2 Gb/week/gnss/products/WWWW (GPS, GPS+GLONASS)/glonass/products/WWWW (GLONASS only)

Troposphere

Combination

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

Ionosphere

5+Combination

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

Real–time clocks

Combination

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

Repro2 products

9+Combination

500 Mb/week/gnss/products/WWWW/repro2

WWWW: 4–digit GPS week number; YYYY: 4–digit year

The CDDIS also continues to archive combined troposphere estimates in directories by
GPS week. Global ionosphere maps of total electron content (TEC) from the IONEX
AACs are archived in subdirectories by year and day of year. Real–time clock comparison
products have been archived at the CDDIS in support of the IGS Real–Time Pilot Project,and current IGS Real–Time Service, since 2009.
In 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).

3.3 Real–Time Activities
In 2013, the CDDIS staff configured a server and began testing a real–time caster to provide
a real–time streaming capability at GSFC and support the IGS Real–Time Service (IGS
RTS). The CDDIS successfully tested obtaining product streams from the BKG and IGS
casters and providing access to these streams to authorized users; additional streams from
NRCan and GA were later added to the caster. Work was completed in spring 2015 andthe 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. Fig. 1 shows the distribution of stations providing real–timestreams 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 User Registration System(URS), with over 140K users in its system. Since the NTRIP–native registration/accesssoftware was not compatible with NASA policies, the CDDIS developed software to interface the caster and the URS within a generic Lightweight Directory Access Protocol(LDAP) framework. The module was specifically developed to easily interface with multiple user verification systems and was given back to the NTRIP community for possible132

3 Archive Content

Figure 1: CDDIS is operationally supporting the dissemination of data from over 160 real–time
GNSS sites as well as near real–time products derived from these data.

inclusion in future releases. The user registration form is available on the CDDIS website;
once completed, the data are passed to the URS, which generates an email to the user
with a validation link. The user accesses the link and the URS validates the form’s data;
this process is accomplished within a minute or less. The user’s validated access request is
submitted to CDDIS staff for access authorization to the CDDIS caster. This second step
is not yet automated and can take several hours to configure depending on the time ofday. In addition, users registering in this system have access to the entire suite of EOSDIS
products across all 12 EOSDIS DAACs.
Initially, the CDDIS caster is providing access to product streams from several regional
real–time casters. Data streams have also been tested, provided through JPL for receivers
in NASA’s Global GPS Network. In the near future, an additional set of stations from
JPL’s Global Differential GPS (GDGPS) network will be added to the CDDIS caster. This
network of globally distributed, geodetic quality, dual frequency receivers, will provide
additional 1 Hz data streams to those current available from the IGS RTS.
Now that the CDDIS caster is operational, the system serves as the third primary casterfor the IGS RTS, thus providing a more robust topology with redundancy and increased
reliability for the service. User registration, however, for all three casters is unique; therefore current users of the casters located at the IGS and BKG will be required to register
through the CDDIS registration process in order to use the CDDIS caster. By the end of
2015, over 50 users from 16 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 fifteen–
minute high–rate files. This capability requires further testing and coordination with the
IGS Central Bureau and Infrastructure Committee.
133

CDDIS Data Center

3.4 Supporting Information
Daily status files of GNSS data holdings, reflecting timeliness of the data delivered aswell as statistics on number of data points, cycle slips, and multipath, continue to begenerated by the CDDIS for RINEX V2 data. By accessing these files, the user community
can receive a quick look at a day’s data availability and quality by viewing a single file.
The daily status files are available through the web at URL ftp:/cddis.gsfc.nasa.gov/
reports/gnss/status. The daily status files are also archived in the daily GNSS data
directories.
In preparation for the analysis center’s second reprocessing campaign, the CDDIS developed site–specific reports detailing missing data. Station operators and operational data
centers can consult these lists (ftp:/cddis.gsfc.nasa.gov/gnss/data/daily/reports/
missing) and if available, supply missing files to the CDDIS for inclusion in the global
data center archives.
Ancillary information to aid in the use of GNSS data and products are also accessible
through the CDDIS. 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.gsfc.nasa.gov/reports/
gnss. The CDDIS also maintains an archive of and indices to IGS Mail, Report, Station,and other IGS–related messages.

4 System Usage
Figure 2 summarizes the usage of the CDDIS for the retrieval of GNSS data and products
in 2015. This figure illustrates the number and volume of GNSS files retrieved by theuser community during 2015, categorized by type (daily, hourly, high–rate, MGEX data,
products). Nearly 930 million files (nearly 100 Tbytes), excluding robot downloads, weretransferred in 2015, with an average of nearly 80 million files per month. Figure 3 illustrates the profile of users accessing the CDDIS IGS archive during 2015. The majority of
CDDIS users were once again from hosts in North America, Asia, and Europe.

5 Recent Developments
5.1 CDDIS Website
The CDDIS developed two applications for querying site information or archive contents.
The Site Log Viewer (http://cddis.gsfc.nasa.gov/SLV2/network/QuerySiteLogs.action)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.

134

1000

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N
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Number of Filess (M)

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35

3500

30

3000

25

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20

2000

15

1500

10

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5

50

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having particular equipment or characteristics.
29%

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%

Development of a second application, the CDDIS Archive Explorer, was completed in 2015;
this application allows users to discover what data are available through the CDDIS. The
application (accessible at http://cddis.gsfc.nasa.gov/Data_and_Derived_Products/
CddisArchiveExplorer.html)
allows users, particularly those new to the CDDIS, the
Asia
30
%
ability to specify search criteria based on temporal, spatial, target, site designation, and/or
observation parameter in order to identify data and products of interest for download.
Results of these queries include a listing of sites and additional metadata satisfying the.
Figure3 Geographi
3:
ic distributioon Suchof IGS auseersof theCD
DDIS in2015aids
user input
specifications.
userinterface
also
CDDIS staff in managing thecontents of the archive. Future plans for the application include adding a list of data
holdings/URLs satisfying the search criteria.
5.3

M
Metadata
D
Developmen
nts

5.2 Next Generation Hardware
The current CDDIS server configuration consists of multiple incoming and outgoing servers
dedicated to specific functions; the system is equipped with 32 Tbytes of online RAID
storage. A new virtual–machine based system was installed within the EOSDIS computer
facility and network infrastructure and is currently under testing with expected operationsin spring 2016. This new system configuration will provide a more reliable/redundantenvironment (power, HVAC, 24–hour on–site emergency personnel, etc.) and network
connectivity; a disaster recovery system will be installed in a different location on the
GSFC campus. The new system location will address the number one operational issue135

CDDIS Data Center
CDDIS has experienced over the past several years, namely, the lack of consistent andredundant power and cooling in its existing computer facility. Multiple redundant 40G
network switches will also be utilized to take full advantage of a high–performance network
infrastructure by utilizing fully redundant network paths for all outgoing and incoming
streams along with dedicated 10G network connections between its primary operations
and its backup operations. The CDDIS will also transition approximately 85% of its
operation services over to virtual machine (VM) technology for both multiple instanceservices in a load balancing configuration which will allow additional instances to be
increased or decreased due to demand and will allow maintenance (patching, upgrades,etc.) to proceed without interruption to the user or any downtime. CDDIS will be utilizing
a unified storage system (100 Tbytes in size) to easily accommodate future growth of
the archive and facilitate near real–time replication between its production and disasterrecovery sites.

5.3 Metadata Developments
The CDDIS continues to make modifications to the metadata extracted from incoming
data and product files pushed to its archive. These enhancements have facilitated crossdiscipline data discovery by providing information about CDDIS archive holdings to otherdata portals such as Earth Observing System search client and future integration into
the Global Geodetic Observing System (GGOS) portal. The staff has begun a metadata
evolution effort, re–designing the metadata extracted from incoming data and adding
information that will better support EOSDIS applications such as its search client andthe metrics collection effort. The CDDIS is also participating in GGOS metadata efforts
within the Bureau of Networks and Communications.
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, fordaily Hatanaka–compressed GNSS data files, can be viewed at: http:/cddis.gsfc.nasa.
gov/Data_and_Derived_Products/GNSS/daily_gnss_d.html. DOIs will be assigned toadditional GNSS data and product sets in the near future.

6 Publications
The CDDIS staff attended several conferences during 2015 and presented papers on or
conducted demos of their activities within the IGS, including:• P. Michael, C. Noll, J. Roark. "CDDIS Near Real–Time Data for Geodesy Based136

7 Future Plans
Applications", Abstract IN43C–3709 presented at 2014 Fall Meeting, AGU, San
Francisco, Calif., 15–19 Dec.
• M. Pearlman, C. Ma, C. Noll, E. Pavlis, H. Schuh, T. Schoene, R. Barzaghi,
S. Kenyon, "The GGOS Bureau of Networks and Observations and an Update on
the Space Geodesy Networks", Abstract EGU2015–7420 presented at EGU 2015,
April 13–17, 2015, Vienna, Austria, April 12-17, 2015.
• C. Noll, P. Michael, L. Tyahla, "Distributing Real-Time GNSS Data and Derived
Products at the CDDIS", NASA Earthdata Webinar Series, July 22, 2015.
• C. Noll, P. Michael, N. Pollack, "Recent Developments at the CDDIS in Supportof GGOS", Abstract No. G43A–1023 presented at 2015 Fall AGU meeting, San
Francisco, CA USA, December 14–18, 2015.
Electronic versions of these and other publications can be accessed through the CDDIS on–line documentation page on the web at URL http:/cddis.gsfc.nasa.gov/Publications/
Presentations.html.

7 Future Plans
The CDDIS will continue to 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 theoperational GNSS data directory structure. The CDDIS has begun this process withmulti–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 the operational directory archive. Furthermore, the CDDIS staff willcontinue to test software to copy RINEX V3 data into files with RINEX V3 filenames
as well as QC RINEX V3 data and files and incorporate the software into operational
procedures.
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 as the CDDIS caster becomes operational and data
streams from real–time stations are added and coordination with the IC. The staff will also
investigation automating the process of adding users to the CDDIS caster configuration
files.
CDDIS has traditionally used ftp for delivery of data for the archive from both data
centers and analysis centers. While this has worked well over the years, transition to the
new system provides an opportune time to look at updating this method to a web–based

137

CDDIS Data Center
approach that can utilize the EOSDIS URS infrastructure. CDDIS will further pursue
incorporating a web–based approach that will continue to allow suppliers to use existing
scripts without significant modification but also tie authentication into the URS.

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

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

9 Acknowledgments
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 senior staff, Patrick Michael, and the contractor staff, Maurice Dube, Nathan Pollack, Rebecca Limbacher and Carlysle McNaught(Science Systems and Applications, Inc./SSAI), Lori Tyahla (Stinger Ghaffarian 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, 45(12):1421–1440, 2010.
ISSN: 0273–1177, DOI: 10.1016/j.asr.2010.01.018.
Noll, C., Y. Bock, H. Habrich, and A. Moore. Development of data infrastructure to
support scientific analysis for the International GNSS Service. Journal of Geodesy, 83(3–4):309–325, 2009. DOI: 10.1007/s00190–008–0245–6.

138

Part IV
Working Groups, Pilot Projects

139Antenna Working Group
Technical Report 2015
R. Schmid
Deutsches Geodätisches Forschungsinstitut
der Technischen Universität München (DGFI-TUM)
Arcisstr. 21, 80333 München, Germany
E–mail: schmid@tum.de

1 IGS-specific spacecraft axis convention
At the IGS Workshop 2014 in Pasadena, the following recommendation was made: “Adopt
GPS-style spacecraft axes conventions for Galileo/BeiDou/QZSS to achieve a consistenthandling of the yaw-steering mode across all constellations and satellites.” This IGSspecific axis convention is described in detail by Montenbruck et al. 2015:• The +z-axis is the principal body axis closest to the antenna boresight direction(i.e., the direction of the maximum beam intensity).
• The y-axis is parallel to the rotation axis of the solar panels. The positive y-direction
is defined through the corresponding x-axis orientation.
• The +x-direction is chosen such that the +x-panel is permanently sunlit duringnominal yaw-steering, while the −x-panel remains dark at all times.

As this coordinate system is strictly body-fixed, the directions of the three axes are notdirectly referred to the positions of the Earth and the Sun. Montenbruck et al. 2015 also
provide drawings and verbal descriptions of both the manufacturer- and the IGS-specificaxis conventions for all types of GNSS satellites.

2 Updates and content of the antenna phase center model
Table 1 lists 15 updates of the absolute IGS antenna phase center model igs08_wwww.atx(Schmid et al. 2016) that were released in 2015. Eleven of them are related to changes of141Antenna Working Group
Table 1: Updates of the phase center model igs08_ wwww.atx in 2015 (wwww: GPS week of therelease date; model updates restricted to additional receiver antenna types are only
announced via the IGS Equipment Files mailing list)

142

Week

Date

IGSMAIL

1830

02-FEB-15

7044

1832
1835

18-FEB-15
13-MAR-15

—
7067

1837

26-MAR-15

7071

1840

15-APR-15

7082

1842

30-APR-15

7089

1844
1848

15-MAY-15
12-JUN-15

—
—

1850

26-JUN-15

—

1852
1853

10-JUL-15
16-JUL-15

7121
7124

1854

21-JUL-15

7126

1861

10-SEP-15

7154

1864

29-SEP-15

7164

1869

03-NOV-15

7181

ChangeAdded G032 (G26)
Decommission date: G026
Added TIAPENG3100R2
NONE
Added STXS8PX003A
NONE
Added G027 (G26)
Decommission date: G032 (G26)
Added G071
Decommission date: G027 (G26)
Added JNSCR_ C146-22-1 NONE
Added R714 (R17)
Decommission date: G038, R746
Added JAV_ RINGANT_ G3T JAVC
Added G049 (G08)
Added GMXZENITH10NONE
GMXZENITH20NONE
GMXZENITH25NONE
GMXZENITH25PRO NONE
Added STXS10SX017A
NONE
Added JAVRINGANT_ DM
SCISJAVRINGANT_ G5T NONEJAVRINGANT_ G5T JAVC
TRM57971.00
SCIT
Added SEPCHOKE_ B3E6NONE
SEPCHOKE_ B3E6
SPKE
TRMR8S
NONE
Decommission date: G049 (G08)
Added G072
Added CHCC220GR
CHCD
CHCC220GR2
CHCD
Added C001, C003, C004, C005, C006, C007,
C008, C009, C010, C011, C012, C013,
C014, C015, C016, E001, E002, E101,
E102, E103, E104, E201, E202, E203,
E204, I001, I002, I003, I004, J001
x-offset UPDATED: G001, G002, G003, G004, G005
Added G036 (G10)
Decommission date: G040
Added E205, E206
Added GMXZENITH35NONE
TPSG5_ A1
NONE
Added G073
Decommission date: G036 (G10)2 Updates and content of the antenna phase center model
Table 2: Number of data sets in igs08_ 1869.atx (released in November 2015)
Satellite antennas
GPS
GLONASS
Galileo
BeiDouQZSSIRNSS

Number
90
93
12
15
1
4

Receiver antennas
ROBOT
FIELD
COPIEDCONVERTED

Number
146
90
34
14

the satellite constellation, and four 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_ 1869.atx that was released in November 2015. For GPS andGLONASS, there are 90 and 93 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.
Making use of the IGS-specific axis convention described in Sect. 1, conventional phasecenter offset (PCO) values for Galileo, BeiDou-2, QZSS, and IRNSS satellites could be
added to the model in July 2015 (Montenbruck and Schmid 2015). The initial values canbe found in Table 3 of Montenbruck et al. 2015. In all cases, the phase center variations(PCVs) were set to dummy (zero) values over the required range of nadir angles.
As the four new systems are still under construction, the number of satellites is limited.
As regards BeiDou, the new generation of BeiDou-3 satellites launched in 2015 could not
be considered for the IGS model, as no PCO information is available so far. Galileo and
BeiDou-2 PCO estimates derived from terrestrial data will have to be evaluated by theMulti-GNSS Working Group, before they can replace the conventional values.
Apart from the satellite antennas, the IGS model meanwhile contains phase center calibration values for 284 different receiver antenna types. 92 of them are certain combinationsof an antenna and a radome, whereas the remaining 192 antenna types are not coveredby a radome. As Table 2 shows, igs08_ 1869.atx contains, among others, 146 absoluterobot calibrations and 90 converted field calibrations.
As elevation- and azimuth-dependent calibration values down to 0◦ elevation are mandatory for new or upgraded IGS stations, altogether 183 different antenna types (146 ROBOT+ 34 COPIED + 3 CONVERTED) are currently approved for installation. The remaining
101 types (90 FIELD + 11 CONVERTED) are no longer allowed, but their calibration values are still necessary for existing installations (see Sect. 3) as well as for reprocessing
purposes.

143

Antenna Working Group
Table 3: Calibration status of 493 stations in the IGS network (logsum.txt of 12 January 2016,
igs08_ 1869.atx) compared to former years

Date

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%

18.3%
8.2%
7.7%
7.8%
7.5%
6.5%

20.2%
17.2%
15.5%
13.5%
12.4%
10.5%

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

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, 493 IGS stations as contained in the file logsum.txt (available
at ftp://igs.org/pub/station/general/) on 12 January 2016 were considered. At thattime, 97 different antenna/radome combinations were in use within the IGS network. The
calibration status of these antenna types was assessed with respect to the phase centermodel igs08_ 1869.atx that was released in November 2015.
Nine years after the adoption of absolute robot calibrations by the IGS in November 2006,
state-of-the-art calibrations comprising elevation- and azimuth-dependent PCVs down to
the horizon are available for about 83% of all IGS stations. The increase of about 3%
compared to the previous year mainly results from the integration of a big number of
MGEX stations equipped with properly calibrated antennas into the IGS network. In
2016, a further increase can be expected, as the upcoming igs14.atx model will allow to
replace about 10 converted field calibrations for antenna types that are in use within the
IGS network.

References
O. Montenbruck, R. Schmid, F. Mercier, P. Steigenberger, C. Noll, R. Fatkulin, S. Kogure,and A.S. Ganeshan. GNSS satellite geometry and attitude models. Advances in Space
Research, 56(6):1015–1029, doi 10.1016/j.asr.2015.06.019, 2015.

144

References
O. Montenbruck and R. Schmid. igs08_1854.atx: Update including Galileo, BeiDou,
QZSS and IRNSS satellites. IGSMAIL-7126, IGS Central Bureau, 2015.
R. Schmid, 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.

145

Bias & Calibration Working Group
Technical Report 2015
S. Schaer
Swiss Federal Office of Topography (swisstopo)
Seftigenstrasse 264, CH–3084 Wabern, Switzerland
E–mail: stefan.schaer@aiub.unibe.ch /stefan.schaer@swisstopo.ch

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

2 Activities in 2015
• 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 organization and realization of the second IGS Workshop on GNSS Biases
was a key challenge and achievement in 2015 (see also Sect. 4).
• P1–P2 bias values for GPS and GLONASS are generated as a by-product of theionosphere analysis.

146

3 Last Reprocessing Activities• The tool developed for direct estimation of GNSS P1–C1 and P2–C2 DCB values isused to generate corresponding GPS and GLONASS bias results on a regular basis.
• The ambiguity resolution scheme at CODE was extended (in 2011) to GLONASS
for three resolution strategies. It is essential that self-calibrating ambiguity resolution procedures are used. Resulting GLONASS DCPB(differential code-phase bias)
results are collected and archived regularly.
• More experience could be gained concerning station-specific GLONASS-GPS intersystem translation parameters, which are estimated and accumulated as part of
CODE’s IGS analysis (but completely ignored for all submissions to IGS).
• CODE’s enhanced RINEX observation data monitoring was continued. Examples
may be found at:
ftp://ftp.unibe.ch/aiub/igsdata/odata2_day.txt
ftp://ftp.unibe.ch/aiub/igsdata/odata2_receiver.txt
ftp://ftp.unibe.ch/aiub/igsdata/y2015/odata2_d335.txt
ftp://ftp.unibe.ch/aiub/igsdata/y2015/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/y2015/.

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. Analysis
and combination of these remarkably long time series must be seen as a medium-term (orlong-term) goal.

147

Bias & Calibration Working Group

4 IGS Workshop on GNSS Biases 2015
This workshop was held at the University of Bern on 5–6 November 2015. All related
information, including all presentations, may be found at:
http://www.biasws2015.unibe.ch
The main focus of this workshop was on:• Characteristics and handling of GNSS biases: Most of the presentations addressed related topics and provided corresponding updates.
• Bias-SINEX Format Version 1.00: A first draft format document was preparedand presented at the workshop. Essential format aspects and issues were discussed
in the plenum. An accordingly updated format document will be prepared for theupcoming IGS Workshop in Sydney.

References
Schaer, S. Activities of IGS Bias and Calibration Working Group. In: Meindl, M., R. Dach,
Y. Jean (Eds): IGS Technical Report 2011, Astronomical Institute, University of Bern,
July 2012, pp. 139–154.
Schaer, S. Bias and Calibration Working Group Technical Report 2014. In: Y. Jeanand R. Dach (Eds): IGS Technical Report 2014, Astronomical Institute, University ofBern, May 2015, pp. 133–140.

148

References

IGS Workshop on GNSS Biases 2015
5–6 November 2015
University of Bern, Switzerland (Hauptgebäude Universität Bern, Kuppelraum)www.biasws2015.unibe.ch/programme_biasws2015.pdf

Programme and Oral Presentations
Thursday 5 November
08:30–09:00

Registration

09:00–09:30

Opening Session
Welcome by the Dean (of the Philosophical Natural Sciences Faculty of the University of Bern) – Prof. Dr. G. Colangelo
Introduction by the Director of the AIUB – Prof. Dr. A. Jäggi
Organizational Issues – Rolf Dach
Goals of the Workshop – Stefan Schaer

09:30–10:00

Introduction– Chair: Rolf Dach
Introduction, Overview, Current Status, Bias Products – Stefan Schaer

10:00–10:30

Coffee Break

10:30–11:40

Characteristics of GNSS Biases – Chair: Rolf Dach(15’) Correlator- and Front-End-Dependency of GNSS Pseudorange Biases for Geodetic Receivers – André Hauschild(15’) Nadir angle and elevation angle dependent GPS code delay variations – Lambert Wanninger(15’) Receiver type depending part of observed satellite wide lane delays – Sylvain Loyer

11:45–11:50

Photo session

12:00–13:15

Lunch at UNIESS Bistro Bar Lounge

13:30–14:00

Continuation(15’) Code Inter-Frequency Biases in GNSS Receivers – Jean-Marie Sleewaegen(15’) Determination of Phase Biases with zero-baseline common clock setups – Steffen Schön

14:00–15:00

Treatment of GNSS Biases – Chair: Peter Steigenberger(15’) RTCM-SSR Strategy of Bias Treatment – Wübbena Gerhard(30’) Generalized Bias Handling in the Bernese GNSS Software and First Examples – Arturo Villiger(10’) Outlook Concerning New Bias Products From CODE – Stefan Schaer

15:00–15:30

Coffee Break

15:30–17:00

Continuation(15’) Correction for Code-Phase Clock Bias in PPP– Pascale Defraigne(15’) Coupled satellite/receiver biases – Laurent Lestarquit(10’) Absolute DCB determination – Laurent Lestarquit(20’) Comparison of MGEX bias products – Rolf DachBias-SINEX Version 1.00:Main Issues – Stefan Schaer

19:00–22:00

Dinner at Restaurant Beaulieu

Friday 6 November
09:00–10:30

New GNSS and signals (e.g. IGS MGEX) – Chair: Oliver Montenbruck(20’) MGEX DCB products – Oliver Montenbruck(20’) Multi-GNSS Differential Code Biases (DCB) Process at IGG –Ningbo Wang (presented by Oliver Montenbruck)(20’) GFZ Analysis Centre: Multi-GNSS Processing and Products –Mathias Fritsche(10’) Handling of modernized signal DCBs – Laurent Lestarquit

10:30–11:00
11:00–12:15

Coffee BreakContinuation(20’) MGEX Clock Determination at CODE – Etienne Orliac(10’) GNSS Receiver Test Site at NRCan – Ken MacLeod (presented by Simon Banville)(20’) Impact of PCV corrections on bias determination for multi GNSS –Steffen Schön
Format Discussion Concerning Bias-SINEX 1.00 and IONEX 1.1: General Rules – Stefan Schaer

12:30–13:45

Lunch at UNIESS Bistro Bar Lounge

14:00–15:30

Standardization – Chair: Stefan Schaer
Data Format Issues: IONEX Version 1.1 – Stefan Schaer
Data Format Issues: Bias-SINEX Version 1.00 – Stefan Schaer

15:30–16:00

Coffee Break

16:00–16:30

Continuation
Data Format Issues: Bias-SINEX Version 1.00 – Stefan Schaer

16:30–17:00

Closing Session – Chair: Stefan Schaer
Summary (Key Issues) – Stefan Schaer

Figure 1: Programme of the second IGS Workshop on GNSS Biases 2015.

149

Bias & Calibration Working Group

Figure 2: The 31 participants of the IGS Workshop on GNSS Biases on 5th November 2015 infront of the main building of the University of Bern, Switzerland.

150

Clock Products Working Group
Technical Report 2015
Michael J. Coleman
U.S. Naval Research Laboratory – Code 8153
Washington, DC 20375, United States

1 Introduction
The clock products working group continues to provide a stable time scale reference for
the IGS rapid and final clock products. These time scales are based on the combinations
formed from clock solutions of the individual Analysis Centers (AC). The time scale product exchanges the reference clock for both the rapid (IGR) and final (IGS) clock productcombinations. It should be noted that clock products for the ultra rapid products (andother more frequent products, such as the real time) are not influenced or computed bythis group as of this year.
Improvements to the IGS timescale as well as publication of clock predictions and frequency states will be considered in the coming years. There have been a variety of advances in time scale analysis and computation methods over the past five years which will
likely benefit the stability of the time scale product as well as enhance its use for satellite
clock estimation.
Meetings among various members for this group are typical at a variety of venues including
EFTF, PTTI, AGU, EGU, etc. Formal declared meetings for this group (as a whole) are
rare, however. As a result, the membership list often goes unchecked for many years at atime. This year, the list of membership is being recertified and is summarized later in thisreport. Some former members have renewed their interest in participating in this working
group while others have suggested younger members of their teams to join this working
group.

151

Clock Products Working Group

2 Existing Timescale ProductAn update of the IGS timescale was presented to the Consultative Committee on Timeand Frequency at the BIPM in September 2015. The central point made was the loss of
UTC clocks in the IGS combinations. Although the IGS timescale can be formed using
any collection of clocks, absence of the best ground station reference clocks can jeopardize
the stability of the IGS time scale. When Analysis Centers change the ground network
used from one day to the next, the composition of ground clocks that pass through the
combinations is changed. From the previous day to the current, some clocks disappear– a
phenomena we call a clock “drop–out”.
These clock contribution losses are particularly detrimental when clocks that are steeringreferences or stable UTC(k) clocks are lost. Unfortunately, the existing steering algorithm
requires at least one steering target in order to process the IGS timescale and maintainreasonable alignment to UTC. When fewer clocks that are designated as steering targets
These clock
contribution
lossesparticularly
detrimental
when
are available,
UTCalignment
can aredrift(sometimes
sharply);
see clocks
Figurethat
1. are steeringreferences or stable UTC(k) clocks are lost. Unfortunately, the existing steering algorithm

requires
at is
least
steering target
in orderto process
IGS intimescaleandscalemaintain
A parallel
issue
theonesubsequent
increaseof GPSsatellitetheclocksthe time
average.
reasonable alignment to UTC. When fewer clocks that are designated as steering targets areavailable, UTC alignment can drift (sometimes sharply); see Figure 1.
2000

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

2011

2012

2013

2014

2015

0

UTC−GPST (Circular T)

−50

52000

IGST−GPST

53000

IGRT−GPST

54000

55000

56000

57000

55000

56000

57000

55000

56000

57000

*

UTC−IGS(R)T

Nanoseconds

500UTC−IGST

−50

52000

UTC−IGRT

53000

54000
IGRT − IGST

Nanoseconds

50

U.S. Naval Research Laboratory 08−Feb−2016, 13:07

Nanoseconds

50

0

−50

52000

53000

54000
MJD

* Assumes that GPS Time via Circular T is equivalent to GPST

152

Figure 1: Offset of IGS Timescales versus UTC.
Figure 1: Offset of IGS Timescales versus UTC.
A parallel issue is the subsequent increase of GPS satellite clocks in the time scale average.
Historically, the total contribution of the satellite clocks has been low as older clocks on
Block IIA and early Block IIR satellites possessed lower stability and occasional frequency
breaks. Now, with improving satellite clocks in the Block IIF satellites, these GPS clocks
often supplant ground station masers when those stations are drop–outs for the day. This haslead to a decreased weight of overall ground stations. Figure 2 shows the steadily increasingpresence of GPS clocks in the IGS timescale over the past several years.
The positive side of this issue is that satellite clocks are improving. These newer satellite
clocks are being recognized by the automated weighting algorithm as being healthy, andstable clocks. This is, of course, a desirable trend for the precision of the GPS system forground users. In terms of the time scale, the existing algorithm does not have new andcorrected models compiled for the satellite clocks that have been developed in the past two

2 Existing Timescale ProductHistorically, the total contribution of the satellite clocks has been low as older clocks on
Block IIA and early Block IIR satellites possessed lower stability and occasional frequency
breaks. Now, with improving satellite clocks in the Block IIF satellites, these GPS clocks
often supplant ground station masers when those stations are drop–outs for the day. This
has lead to a decreased weight of overall ground stations. Figure 2 shows the steadily
increasing presence of GPS clocks in the IGS timescale over the past several years.
The positive side of this issue is that satellite clocks are improving. These newer satellite
clocks are being recognized by the automated weighting algorithm as being healthy, andstable clocks. This is, of course, a desirable trend for the precision of the GPS system forground users. In terms of the time scale, the existing algorithm does not have new andcorrected models compiled for the satellite clocks that have been developed in the past
two years. As a result, the historical reliance on solid and stable ground clocks is stillnecessary to maintain stability. We seek to include the new satellite clock model in theyears. As a result, the historical reliance on solid and stable ground clocks is still necessary
future;see Section
4 for further
to maintainstability.
We seekdetails.
to include the new satellite clock model in the future; see
Section 4 for further details.

Clock Weight %

IGR
IGS

40

20

0

2010

2011

2012

2013

2014

2015

2016

2015

2016

GPS IIF Broadcast Start

GPS Clock Contribution to IGS(R)T
60

Size of IGS(R)T Clock Membership
Number of Clocks

80
60
40
20
0

2010

2011

2012

2013

2014

Figure 2: Upper plot shows total contribution of the GPS constellation (by weight) to the
Figure 2: Upper plot shows total contribution of the GPS constellation (by weight) to the
IGS(R)T ensemble. The lower plot shows the total number of clocks contributing weight to
IGS(R)T ensemble. The lower plot shows the total number of clocks contributing
the ensemble sampled weekly. There may be many more clocks in the combinations, butweight to the ensemble sampled weekly. There may be many more clocks in the comsome do
not contribute weight to the time scale.
binations, but some do not contribute weight to the time scale.
Fewer clocks are present in the rapid (IGR) timescale product than in the final (IGS) since
the collection of analysis centers contributing solutions for each differs. For example, MITcommits a solution to the final, but not rapid product. For a variety of reasons, the compo153
sition of the IGR and IGS timescales is not the same and total weight of GPS clocks likewise
also differs. Spikes can be noticed in the GPS weight contribution in the IGR timescale since
new combinations (and hence the ground network) are refreshed daily.
Clock drop–outs are of greatest concern among the set of stations listed in Table 1 since they
are stable clocks that each provide direct traceability to UTC. Figure 3 shows the clock offset(with a small quadratic removed) for station IENG. An increase in clock state uncertainty
along with reduced weight is seen on dates when the clock is dropped.

Clock Products Working Group
Table 1: Partial list of stations with IGS & UTC as well as the number of days each clock in
an ensemble member of the IGS(R)T time scales (The two weights, wp and wf are theaverage phase and frequency weight contributed by the clock over the set of days that
it is an ensemble member.)

Station

IGST

IGRT

IGS

UTC

Location

Days

wp

wf

Days

wp

wf

BJNM
IENG
NIST
OPMT
PTBB
SFER
SPT0
TWTF
USNO
WAB2

NIM
IT
NIST
OP
PTB
ROA
SP
TL
USNO
CH

Beijing CHINA
Torino ITALY
Boulder CO USA
Paris FRANCE
Braunschweig GERMANY
San Fernando SPAIN
Boras SWEDEN
Chung-Li TAIWAN
Washington DC USA
Bern SWITZERLAND

104
45
0
335
354
333
130
181
73
340

4.36
2.20
–
4.23
4.68
4.20
3.69
2.97
3.58
2.58

4.71
0.88
–
4.37
4.68
2.14
3.68
3.01
1.09
2.45

0
333
212
81
355
10
194
155
58
327

–
1.94
4.94
4.17
5.00
4.74
4.66
4.40
4.37
2.97

–
0.43
4.93
4.17
5.00
3.47
4.66
4.46
4.36
0.15

Fewer clocks are present in the rapid (IGR) timescale product than in the final (IGS)
since the collection of analysis centers contributing solutions for each differs. For example,
MIT commits a solution to the final, but not rapid product. For a variety of reasons, thecomposition of the IGR and IGS timescales is not the same and total weight of GPS clocks
likewise also differs. Spikes can be noticed in the GPS weight contribution in the IGRtimescale since new combinations (and hence the ground network) are refreshed daily.
Clock drop–outs are of greatest concern among the set of stations listed in Table 1 since
they are stable clocks that each provide direct traceability to UTC. Figure 3 shows theclock offset (with a small quadratic removed) for station IENG. An increase in clock state
uncertainty along with reduced weight is seen on dates when the clock is dropped.

3 Timing Site Designations
In an effort to improve the performance of the reference time frame for the IGS clocks inboth the rapid and final products, it has been suggested that the IGS add a new designation
to its network. This designation will tag several of the stations within the IGS network
as Timing Stations. Better publicity of these stations’ timing abilities will enhance thechances that AC solutions utilize these sites in their ground network selection.
Timing Stations will consist only of sites that contribute their master clock data to
the Bureau International des Poids et Mesures (BIPM) for computation in the monthly
CircularT– the official dissemination of UTC. Even among these 73 sites, we only designate those sites that have confirmed that their receiver clock is traceable to the clock

154

OPMT
PTBB
SFER
SPT0
TWTF
USNO
WAB2

OP
PTB
ROA
SP
TL
USNO
CH

335
354
333
130
181
73
340

Paris FRANCE
Braunschweig GERMANY
San Fernando SPAIN
Boras SWEDEN
Chung-Li TAIWAN
Washington DC USA
Bern SWITZERLAND

4.23
4.68
4.20
3.69
2.97
3.58
2.58

4.37
4.68
2.14
3.68
3.01
1.09
2.45

81
355
10
194
155
58
327

4.17
5.00
4.74
4.66
4.40
4.37
2.97

4.17
5.00
3.47
4.66
4.46
4.36
0.15

Table 1: Partial list of stations with IGS & UTC as well as the number of days each clock
is an ensemble member of the IGS(R)T time scales. The two weights, wp and wf are the
3 Timing Site Designations
average phase and frequency weight contributed by the clock over the set of days that it isan ensemble member.
Filter States & Sigmas
IENG
01−Aug−2015 through 31−Aug−2015
2015
AUG

1

2

2

3

4

5

6

7

8

9

10

11

2

phase + WHPH + periodic(− 0.0061t − 0.019t+ 19)

12

13

14

15

16

17

18

19

2

phase (− 0.0061t − 0.019t+ 19)

20

21

22

23
1

24

frequency (− 0.0051t + 0.081)

25

26

27

28

drift ( 0.058)

29

30

31

1

8

2 phase reset(s)

1.5

6

1

4

0.5

2

0

0

−0.5

−2

−1

−4

0.04

0

phase (ns)drift (ns/day2)

0.02

frequency (ns/day)

0.06

−0.02

−0.04

−0.06

−1.5

0.4

6

−6

5
2

0

0

0

1

10

1

5

0.5

0.5
0

0

0

5

10

15

20

MJD − 57235

25

30

fr. sigma (ns/day)

0.1

10

4

wf (%)

0.2

ph. sigma (ns)0.3wφ (%)

wd (%)

dr. sigma (ns/day2)

Sigmas0

U.S. Naval Research Laboratory, 01−Sep−2015 16:35:17

Figure 3: IGS clock product estimates of station clock at IENG site. Absence of this clock
dates
16, 19,22 and 24
August leada loss ofclock
this clock’s
contribution
to the IGRT
Figure 3: on
IGS
clock
product
estimatesof tostationat IENG
site. Absenceof on
this clock onthese dates.
dates 16, 19, 22 and 24 August lead to a loss of this clock’s contribution to the IGRT
on these dates.
4

signal of that UTC(k) and which are also IGS stations.
At the 45th Governing Board Meeting and associated Analysis Center Splinter Meeting,it was suggested that a list of UTC reference stations be developed. This list in Tab. 2
has been created and includes the following clocks, ranked by their order of preference forinclusion with the corresponding UTC designations.
Table 2: List of UTC reference stations (Names in IGS and UTC)
IGS
UTC

PTBB
PTB

USN7
USNO

OPMT
OP

IENG
IT

BJNM
NIM

SPT0
SP

SFER
ROA

WAB2
CH

NIST
NIST

TWTF
TL

NRC1
NRC

It was emphasized to ACs that the four sites PTBB, USN7, OPMT and IENG should beconsidered the most important selections. The loose criteria for selecting these particularsites are:• Station is a timing laboratory that participates in the computation of TAI and islisted in the BIPM’s CircularT.
• Confirmation that the clock signal supplied to the antenna utilized for IGS as wellas UTC(k) is the same (possibly with a known calibrated bias).
• Stable performance in the CircularT with a reliably low value for |UTC – UTC(k)|.
155

Clock Products Working Group• Geographic distribution. Lower density in this group of Timing Stations increases
the likelihood of their selection among ACs.
Despite this advance, it is still expected that some analysis centers will be unable to add
all or even many of these timing stations given the requirements imposed by the existing
analysis done there. Additional stations can dramatically tax the processing of any one
solution and it is often desirable to keep the number of ground stations low. Some solutions
may also require some degree of separation of the ground stations for the benefit of other
IGS products.
In the coming year, a parallel IGS timescale (unofficial) will be test an improved steering
approach that utilizes UTC(k) clocks whenever they are available. It is expected that the
UTC alignment can still be tightened as a result of such efforts.

4 Future Consideration: Satellite Models
The timescale is formed by a standard Kalman Filter approach utilizing a wide array ofauxiliary functions that handle clock anomalies in an automated fashion. Some of thedetails of this timescale have been presented in the past and are available in Senior et al.
2003 and Coleman and Senior 2011, for example.
Many of the new Block IIF clocks are approaching the performance of masers in the mid
to longer term; see Vannicola et al. 2013 and Senior and Coleman 2014. Clocks of thistype tend to perform well even with the existing IGS timescale; see Fig. 4 for an example.
Note in this figure, that clock’s phase, frequency and drift state are well determined andthat 1/rev and 2/rev periodics also superimpose as expected over the clock’s phase. For
this reason, inclusion of this clock can benefit stability. Predictions of this clock could
also be made if clock data is needed at a data rate higher than the publication latency.
The existing products do not always detect clock breaks, or accurately converge on satellite
clock harmonics. This can be seen clearly in Fig. 5, for example. There, a break infrequency is followed by a period of misalignment between the phase and its associatedtotal phase value (which incorporates periodics). Improvements in the satellite clock
models and initialization routines are expected to be implemented to the IGS timescalein the coming years and can help to improve estimate anomalies such as this one. Somedevelopments on satellite clock models can be found in Coleman and Senior 2011.
The IGS timescale also stands to benefit when the products include solutions of clocks
from other GNSS systems. A common time reference for all member satellite clocks could
make clock comparisons easier between satellite systems. The Clock Products Working
Group should endeavor to grow the timescale membership following the MGEX projectand potential inclusion of all GNSS into the IGS products.

156

The timescale is formed by a standard Kalman Filter approach utilizing a wide array ofauxiliary functions that handle clock anomalies in an automated fashion. Some of the detailsof this timescale have been presented in the past and are available in [1] and [2], for example.
Many of the new Block IIF clocks are approaching the performance of masers in the mid tolonger term; see [3] and [4]. Clocks of this type tend to perform well even with the existing
IGS timescale; see Figure 4 for an example. Note in this figure, that clock’s phase, frequency
and drift state are well determined and that 1/rev and 2/rev periodics also superimpose as
expected over the clock’s phase. For this reason, inclusionof thisclock can benefit
stability.Models
4 Future
Consideration:
Satellite
Predictions of this clock could also be made if clock data is needed at a data rate higher
than the publication latency.
Filter States & Sigmas
G3201−Nov−2015 through 30−Nov−2015
2015
NOV

0.2

1

10

2

3

4

5

6

7

8

9

10

11

12

13

14

2

15

16

17

18

19

20

21

2

phase + WHPH + periodic( 0.45t + 1e+03t+ 1.8e+04)

22

23

24

25

26

1

phase ( 0.45t + 1e+03t+ 1.8e+04)

frequency ( 0.88t + 1e+03)

27

28

29

30

1

12

drift ( 1)

10
0.15
8

5

6
4

0
phase (ns)

0.05

0

frequency (ns/day)drift (ns/day2)

0.1

2
0

−5

−2

−0.05

−4

−10

−0.1
−6
−0.15

−15

0.5

0.4

−8

0.4

2.35
fr. sigma (ns/day)

ph. sigma (ns)

0.45

0.3

2.3

0.2
0.1

2.25

2

1

1

0.5

0.5
0

0

0

5

10

15

20

0

25

MJD − 57327

wf (%)

0

1
wφ (%)

0.35

wd (%)

dr. sigma (ns/day2)

SigmasU.S. Naval Research Laboratory, 01−Dec−2015 16:34:22

Figure 4: IGS clock product for G32 satellite clock (PRN 32). All states are relatively welland productthis clock forcontributes
approximately
1% of thetime scaleweight.
Figure determined
4: IGS clock
G32 satellite
clock (PRN32).total
AllIGS
statesare relatively
welldetermined and this clock contributes approximately 1% of the total IGS time scale
Theweight.
existing products do not always detect clock breaks, or accurately converge on satellite
clock harmonics. This can be seen clearly in Figure 5, for example. There, a break in
Filter States & Sigmas

6G3001−Nov−2015 through 30−Nov−2015
2015
NOV

1

4

2

3

4

5

6
2

7

8

phase + WHPH + periodic(− 0.61t + 4.9e+02t+ 5.7e+04)

9

10

11

12

13

14

15

16

17

2

phase (− 0.61t + 4.9e+02t+ 5.7e+04)

18

19

20

21

1

22

frequency (− 1.3t + 4.9e+02)

23

24

25

26

drift (− 1.3)

27

28

29

1

4
1 freq reset(s)

2

3

0

2

−2

1

−4

0

−6

−1

0.5

0
phase (ns)drift (ns/day2)30

1 phase reset(s)frequency (ns/day)

1

−0.5

−1

−1.5

−8

0.11

0.1

−2
0.12
0.11
0.1

0.05

0.09
0.08

10

10

10

5
0

5

5
0

0

5

10

15

MJD − 57327

20

25

wf (%)

0wφ (%)

0.08

fr. sigma (ns/day)

0.09

ph. sigma (ns)0.1

wd (%)

dr. sigma (ns/day2)

Sigmas0

U.S. Naval Research Laboratory, 01−Dec−2015 16:34:20

Figure 5: IGS clock product for G30 satellite clock (PRN30). Immediately following afrequency
on Nova periodof poorestimation
for harmonics
and phasefollowing
ensues. a frequency
Figure 5: IGS
clock breakproduct
for03,
G30
satellite
clock(PRN30).
Immediately
Note that the weight drops to zero as this clock is removed from the ensemble. It returns
break
on states
Nov stabilize,
03, a period
for harmonics and phase ensues. Notewhen thebut not offor poor
several estimation
days.
that the weight drops to zero as this clock is removed from the ensemble. It returns
when
the isstatesstabilize,
not for several
frequency
followedby a periodbut
of misalignment
betweendays.
the phase and its associated total
phase value (which incorporates periodics). Improvements in the satellite clock models andinitialization routines are expected to be implemented to the IGS timescale in the coming
years and can help to improve estimate anomalies such as this one. Some developments on
satellite clock models can be found in [2].
The IGS timescale also stands to benefit when the products include solutions of clocks
from other GNSS systems. A common time reference for all member satellite clocks could
make clock comparisons easier between satellite systems. The Clock Products Working
Group should endeavor to grow the timescale membership following the MGEX project andpotential inclusion of all GNSS into the IGS products.

157

Clock Products Working Group

5 Membership
The membership list for this working group has been revisited this year and updated toreflect those interested in clock products from the IGS. Table 3 is a table of the members and their affiliations. Those in this group consist of research scientists who haveexpertise in timing and frequency and are periodically present at international meetings.
Membership to this working group may be expanded upon request of the coordinator.
Table 3: Membership of Clock Working Group
Last NameFirst Name

Affiliation

Country

Arias
Bertiger
ColemanDachDefraigne
Griffiths
Lin
Petit
RoveraRomeroSeniorSessiaE. Felicitas
WilliamMichaelRolf
PascaleJake
CalvinGérardDanieleIgnacioKen
IlariaBureau International des Poids et Mesures
Jet Propulsion Laboratory
Naval Research Laboratory
Astronomisches Institut, Universität Bern
Observatoire Royal de Belgique
Naval Research Laboratory
National Time and Frequency Standard Laboratory
Bureau International des Poids et Mesures
Observatoire de Paris
ESA / European Space Operations Center
Naval Research Laboratory
Istituto Nazionale di Ricera Metrologica

International
US
US
Switzerland
Belgium
US
TaiwanInternational
FranceGermanyUS
Italy

References
Michael J. Coleman and Ken Senior. A comparison of GPS clock models for the next
generation GPS system timescale. In Proceedings of the 43rd Annual Precise Timeand Time Interval Systems and Applications Meeting, Long Beach, California, 2011.
Ken Senior and Michael J. Coleman. Generation of ensemble timescales for clocks at thenaval research laboratory. In Proceddings of the 46th Annual Precise Time and TimeInterval Systems Applications Meeting, ION, pages 98–105, Boston, Massachusetts,
2014.
Ken Senior, Paul Koppang, and Jim Ray. Developing an IGS time scale. IEEE Trans.
Ultrason. Ferroelectr. Freq. Control, 50:585–593, 2003.
Francine Vannicola, Ronald Beard, Douglas Kock, Anthony Kubik, and David Wilson.
GPS Block IIF atomic frequency standard analysis. In Proceedings of the 45th Annual

158

References
Precise Time and Time Interval Systems and Applications Meeting, pages 244–249,
Bellevue, Washington, 2013.

159

Data Center Working Group
Technical Report 2015
C. NollNASA Goddard Space Flight Center
Code 690.1, Greenbelt, MD 20771, USA
E–mail: Carey.Noll@nasa.gov

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

2 Recent Activities
2.1 RINEX V3 Integration
The DCWG continues to work with the IGS Infrastructure Committee (IC) on various
topics of mutual interest. One primary area is the support of GNSS data in RINEX V3
format, initially utilized in the data holdings of the Multi–GNSS Experiment (MGEX)
but becoming increasingly important in IGS activities in general. The following recommendations were generated from the June 2015 DCWG meeting, held during the 2014 IGS
Workshop in Pasadena, CA:• Develop a transition plan that will integrate RINEX V3, including the V3 filename
convention, into the operational IGS archives by the end of 2015. (IC, DCs, ACs,
MGEX WG)

160

2 Recent Activities– Progress: This recommendation supports the IC goal of “one network one archive.”
The current parallel “campaign” structure found at the DCs supporting MGEX limits
the motivation of the ACs to switch to the RINEX V3 format. Integration of the twodata archives (operational and campaign) will promote use of multi–GNSS data andthe new format. Thus, the MGEX Working Group recommended the development ofa transition plan that outlined the steps necessary for integrating the MGEX/RINEX
V3 data into the operational archives. During 2015, the IC developed and circulated
the draft plan, which was approved at the IGS Governing Board meeting in December
2015.
The way forward on this task was to have stations/operations centers utilize thefile naming convention outlined in the RINEX V3 format documentation for any
data in RINEX V3 format supplied to the IGS. Messages were sent to the IGS
Analysis Centers (AC) and the user community in general, presenting the steps
outlined in the transition plan, and informing users of the impending updates to thedata center structure. A few GDCs, the CDDIS and IGN, began implementationof the recommendations in the plan in late December 2015 by agreeing to include
any RINEX V3 data (starting with 2016 data) supplied with the V3 file naming
convention in the operational archives. Thus, both RINEX V2 and V3 data canbe found in the main GNSS data directories at these data centers. The campaign
directories, e.g., for MGEX, continue to contain data in RINEX V3 format utilizing
the older, 8.3 filename format.
• Provide software tools that DCs can use to continue to provide needed QC andmetadata extraction enabling creation of data status information.
– Progress: During the past year, a candidate tool for the DCs that can provide QC
and generate reports from data in RINEX V3 format was suggested. The IC has had
some success with G–Nut/Anubis, a command line tool developed by the Geodetic
Observatory Pecny (GOP) for multi–GNSS data in RINEX V3 format. Tests areunderway at DCs with the Anubis software.
• Provide software tools to support data conversion (e.g., RINEX V3 to RINEX V2;RINEX V3 filename creation) that both DCs and ACs can use.
– Progress: In order to provide more data in RINEX V3 format in the main/non–campaign directories at the GDCs, the IC has requested that the DCs create files
using the RINEX V3 file naming convention from multi–GNSS data in the old filename format. The IC has had success with the gfzrnx tool, developed at GFZ; DCs
are testing the software for this function.

161

Data Center Working Group

2.2 Site Metadata Activities
Another area of interest for the IGS IC and DCWG involves metadata, particularly in thearea of site logs. The IGS CB uses the Site Log Manager System for handling IGS sitelogs, which provides a basis for promoting the transmission of these logs in XML format.
An XML/database management approach to site logs provides several advantages, suchas rapid update of site log contents, utilization of consistent information across data
centers, and availability of more accurate station metadata. The IGS CB and UNAVCO,
in conjunction with the DCWG, held email discussions and telecons to allow participantsin this effort to collaborate and plan for the way forward in design, development, andimplementation of a shared geodesy XML schema, possibly utilizing the site log schemadeveloped at SOPAC, for site information. During 2015, F. Boler continued coordination ofthis activity under the auspices of the IGS DCWG. Several telecons were held with various
IGS data center, network, and infrastructure contacts; the collaborators have identified
GeodesyML, an application schema of the Open Geospatial Consortium, for encoding theSite Log XML metadata elements.
DCWG members participated in a GGOS–sponsored technical interchange meeting on
metadata in August 2015, hosted by UNAVCO, in order to develop a space geodesy
metadata standard that can be used by the services and GGOS. The Site Log XML effort
was a topic for discussion and attendees agreed that this effort within the IGS will prove
useful to, and could be adopted and modified by, the other services.

2.3 Other Activities
DCWG members worked with contacts at the new GDC in Wuhan to begin their integration into the flow of IGS data and products. The chair also worked with ACs and coordinators on submission of repro2 products for their contributions to ITRF2014. Transmissionof data from the NGA GPS monitoring sites resumed in 2015 and GDCs were notified of
their availability for their archives.

3 Future Plans
The DCWG will continue to coordinate with the IC 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 “long”/RINEX V3 filenames into the operationalarchives is progressing for data in 2016. Data centers will continue to test software forcreating files using this V3 filename format to support the integration task. Once theseprocedures 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 address162

4 Membershipfollow.
• Support of the IGS Infrastructure Committee: A major focus of the DCWG will be tosupport the IC in its various activities to coordinate the resolution of issues related
to the IGS components. These activities will address recommendations from the2016 IGS Workshop as well as past workshops, including assessment and monitoringof station performance and data quality, generating metrics on these data.
• Data center harmonization: The working group will consider methodologies for ensuring key data sets are available at all GDCs.
• Compression: As per a recommendation from past IGS workshops, the DCWG
will develop a plan for the introduction of a new compression scheme into the IGS
infrastructure by evaluating tests of available tools, surveying the IGS infrastructure,making a recommendation on a new IGS compression scheme, and coordinating
recommendations with the IC to develop implementation schedule. Ideally, the newcompression scheme will be made part of the RINEX V3 file naming implementation.
• Next meeting: A meeting of the DCWG is planned for the next IGS workshop in
2016.

4 Membership• Carey Noll (NASA GSFC/USA), Chair• Yehuda Bock (SIO/USA)• Fran Boler (UNAVCO)• Ludwig Combrinck (HRAO/South Africa)• Bruno Garayt (IGN/France)• Kevin Choi (NOAA/USA), ex–officio• Heinz Habrich (BKG/Germany)• Michael Moore (GA/Australia)• 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)

163

Data Center Working Group164

Ionosphere Working Group
Technical Report 2015
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 Introduction
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 (Tech∗

Chair of Ionosphere Working Group165

Ionosphere Working Group
nical University of Catalonia, Barcelona, Spain). Independent computation of rapid andfinal VTEC maps is used by the each analysis centers: Each IAACs compute the rapid
and final TEC maps independently and with different approaches including the additional
usage of GLONASS data in the case of CODE.

2 Membership• Dieter Bilitza (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)

166

5 Recommendations after IGS Workshop 2016, Sydney, Australia

3 Productsa) final GIM (please note that GIMs also include GPS and GLONASS stations’ andsatellites’ DCBs)• combination of CODE, ESA, JPL and UPC iono products conducted by UWM• temporal and spatial resolution – at 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 hoursc) predicted GIM for 1 and 2 days ahead (pilot product)• combination of ESA and UPC iono products conducted by ESA• temporal and spatial resolution – at 2 hours x 5 deg. x 2.5 deg (UTxLon.xLat.),

4 Key accomplishmentsa) IGS Global ionosphere predicted products for 1 and 2 days ahead (pilot product). This
new IGS products are currently based on predicted ionosphere maps prepared by UPC
and ESA.
b) IGS Global ionosphere maps with 1 hour 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

5 Recommendations after IGS Workshop 2016, Sydney,
Australiaa) To accept CAS–IGG, NRCan and WHU as new Ionospheric Analysis Centers, contributing to the IGS combined VTEC GIMs,.

167

Ionosphere Working Group

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

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

b) The IONEX format shall be updated in order to accommodate contributions frommultiple constellation and adequately describe the associated differential code biases.
c) Cooperation with IRI COSPAR group for potential improvement of both IRI and IGSTEC.
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.
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

168

6 The pilot phase of the new IGS ionospheric productFigure 3: Evolutions of the daily ROTI maps for 30 May – 4 June 2013.

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

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 .
169

Ionosphere Working Group

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
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, JASON–
1 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, isassessedversusvery measuremen
precise direct
STEC
bycontri
GNSS
receiversin different
to JASOON2 direct
nts, compare
ed observations
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GIMs,
G
ibutingsincee 1998.5
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Ms present, ini general, siimilar, or eitther better prrecision thann the existingg IGS GIMs and their
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EC
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om anycomparedof thhe comparedd models,of VTEC
regardingto urements,
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direct ind
measurements,
withthe existing
willcontributing
be eemphasized. since 1998.5 (CODE, ESA, JPL & UPC). From the point of viewGIMs,
IIt is remarkaable as well thet general aagreement off the bias, at 1 to few TE
ECUs level, regardingrof the correspondingStandard
Deviations, the new GIMs present,in general,similar, or
the altim
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ost part of aanalysis centters. This haappens amonng different mapping
eitherfunction
betterprecision
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and
their
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The
extended
ns used (relateed with the generalglevelling) and the topside electron content climatology
y between
VTEC
will
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the STEC
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the assessment
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erse climatoology”, <VT
meter and GP
PS orbit(seen as variatwith
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eted as “inv
TEC_alt –VTEC_G
GPS>, in thee time series, appearing cclearly the So
olar Cycle annd seasonal ccycles, amonng others.

5. VTEC GIMS
GIM
MS Biasregaarding
JASO
ON*
VTEC (daily
values,, since days
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Figure Fig.5
5: VTEC
Bias
regarding
JASON*
VTEC(dailyvalues,days 2001.6 to2016.0).

170

7 Comparing performances of seven different global VTEC ionospheric models in the
IGS context
Finally the convenience of maintaining the good practice of a right assessment of ionospheric models, by using external measurements, absolutely independent from any of thecompared models, 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 different 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.

171

Ionosphere Working Group172

Multi–GNSS Working Group
Technical Report 2015
O. Montenbruck, P. Steigenberger
DLR, German Space Operations Center
Oberpfaffenhofen
82234 Wessling, Germany
E–mail: oliver.montenbruck@dlr.de

1 Introduction
As its primary task, the Multi–GNSS Working Group (MGWG) steers the performanceof the Multi–GNSS Experiment (MGEX), which promotes and prepares the use of new
signals and constellations within the IGS. As of Dec. 2015, the MGWG has a total of
16 members. These include representatives of selected analysis and data centers (BKG,
CODE, CNES/CLS, DLR, ESA, GFZ, JAXA, WU) as well as various individuals contributing to the overall goals of this project. No changes of membership occurred during
the reporting period, but the position of M. Uhlemann as representative of GFZ was takenover by M. Fritsche starting January 1, 2016.

2 GNSS Evolution
Within 2015, a total of three GPS Block IIF satellites were launched thus increasing their
total number to 11. By the end of that year only one Block IIA satellite remained activein the constellation. With 18 L2C-capable satellites (IIR–M and IIF) and 11 L5–capable
satellites, the GPS makes substantial progress towards provision of a dual–frequency service for civil users. Along with this goal, CNAV navigation messages are issued with amore frequent (once–per–day) upload cycle since the beginning of 2015, which yields auser performance compatible with that of the legacy LNAV message (Steigenberger et al.
2015d). In extension of prior policy, the US government announced in its new Federal
Aviation Plan to ensure availability of P(Y) code transmission for a minimum of two years
after availability of a 24 satellites L5 constellation. This is presently foreseen for 2024.

173

Multi–GNSS Working GroupNo GLONASS launches took place in 2015, but some of the satellites in spare slots started
to identify themselves with slot numbers in the range of 24–27. This enables tracking ofthese satellites by various types of receivers and first RINEX observation data could becollected. Among others this has enabled first analyses of the new Rubidium clock operated
on the GLONASS K1–2 satellite (A. Hauschild, private communication).
China initiated the build–up of their global navigation satellite system with the launchof four 3rd–generation BeiDou satellites. This includes two spacecraft in inclined geosynchronous orbit (IGSO) and two spacecraft in medium altitude Earth orbit (MEO). The
new satellites have started to transmit diverse types of next–generation signals overlaying(and planned to be compatible/interoperable with GPS and Galileo) in the B1 (L1/E1)
and B2 (L5/E5a/E5b) bands as well as B3 (E6). Legacy signals (identifying the four
satellites as PRN C31–C34) are transmitted on the legacy B1 frequency at 1561 MHz.
This has so far enabled single–frequency tracking by existing BeiDou capable receivers.
In the absence of a consolidated and publicly documented new signal structure as well as
various changes of the test signals transmitted so far, tracking of the new satellites is not
yet properly supported by the existing networks. Following the loss of one MEO satellite(C13) in Oct. 2014, the regional (second generation) BeiDou system comprised a total of
13 active spacecraft.
Galileo launched a total of six new Full Operational Constellation (FOC) satellites in 2015
and is now on a rapid pace to build up an initial service. The first pair of FOC satellites,
which had been launched into a wrong orbit and were later raised into a somewhat eccentric
orbit with a semi–major axis of 28,000 km, transmit high–grade signals and are alreadyincorporated into the IGS/MGEX tracking and product generation.
IRNSS, finally, launched its fourth satellite (IRNSS 1D) in spring 2015, which enabled
first standalone position solutions with this system.

3 Network
The number of stations contributing multi–GNSS observations for the MGEX projectcontinued to increase moderately and amounted to almost 130 near the end of 2015 (Fig. 1).
About 50% of these stations provide real–time data streams hosted by BKG’s MGEX
caster (http://mgex.igs-ip.net/). While the majority of streams is delivered in vendor–
specific data formats and converted to the RTCM–3 MSM format by BKG, an increasing
number of receivers is already able to output observation data directly in this new standard
format.
In accord with the currently offered capabilities of commercial GNSS receivers, the current
network supports tracking of Galileo (E1, E5a/b), BeiDou (B1, B2, B3) and QZSS (L1, L2,
E6, L5) signals next to GPS and GLONASS. So far, neither IRNSS nor the new BeiDou–3
signals can be tracked with the current infrastructure. Diversity of equipment (receivers,174

4 Products

MGEX Offline Network (4 Oct 2015, 129 Stations)

GAL
BDS
QZSS

Figure 1: Distribution of MGEX stations supporting tracking of QZSS (blue), Galileo (red), andBeiDou (yellow) as of Oct. 2015.

antennas) in the multi–GNSS network is generally considered an asset for the IGS, butalso poses notable challenges and concerns for high–end processing. Equipment characterization (including, e.g. antenna phase pattern and receiver–specific biases) remains acontinued task for the MGWG in coordination with other IGS working groups.
In accord with the RINEX transition plan, released by the IGS Governing Board (GB) in
Dec. 2014, efforts have started to migrate to the more flexible, long RINEX–3 file names
and to integrate the MGEX data into the standard IGS data repository. For a full harmonization, the vast majority of MGEX stations was included into the IGS network after
verification of their compatibility with the IGS site standards by the Infrastructure Committee (IC). Users are now offered a unified network with a strong multi–GNSS component
rather than two independent networks. In particular, sitelog holdings, station information
pages and network maps are now fully integrated and cover both legacy and multi–GNSSIGS stations (see http://www.igs.org/network). Selected MGEX stations not meeting
the IGS site standards are still available at the MGEX data centers and labeled as “MGEX
Experimental” in the IGS site database.

4 Products
Data from the IGS multi–GNSS network are routinely used by various MGEX analysis
centers (ACs) to generate various forms of products. Most importantly, these include
precise orbit and clock solutions as well as differential code biases. Other types of auxiliary

175

Multi–GNSS Working Group
Table 1: Multi–GNSS orbit and clock products provided by the MGEX analysis centers (Status
12/2015). ACs with clock sampling in brackets do not provide dedicated RINEX clock
files
AgencyID

GNSS

Sampling (Orbit/Clock)

CNES/CLS
CODE
GFZ
JAXA
TUM
WU

grm
com
gbm
qzf
tum
wum

GRE
GRECJ
GRECJ
GJ
EJ
GRECJ

15 min/30 s
15 min/5 min
5 min/30 s
5min/(5 min)
5 min/(5 min)15 min/5 min

Jan
2013

Jul
2013

Jan
2014

2016-01-21

com
esm
gbm
gfm
grm
qzf
tum
wum
Jan
2012

Jul
2012

Jul
2014

Jan
2015

Jul
2015

Jan
2016

Figure 2: Overall availability of multi–GNSS orbit and clock product contributions from individual MGEX analysis centers. Note that the set of supported constellations has gradually
been increased over time by some ACs.

products include cumulative broadcast orbits (available in offline and real–time formats),
station coordinates, and intersystem biases
Within 2015, a total of six analysis centers generated multi–GNSS obit and clock products
for MGEX on a routine basis (Tab. 1). Three of these are full five–constellation products
including GPS, GLONASS, Galileo, BeiDou–2, and QZSS in a common reference frame
and time. A bar chart indicating the overall product availability is shown in Fig. 2.
The availability of orbit and clock products from multiple ACs enables a basic assessmentof the product quality for each constellation based on the consistency of the individual
solutions. In addition, satellites of all new GNSSs are equipped with laser retroreflector
arrays, that enable satellite laser ranging for validation of the orbit accuracy.
As summarized in Tab. 2, a precision of a few decimeters is typically achieved for MEO
and IGSO satellites, with best results obtained for Galileo as a result of the large numberof worldwide tracking stations. Worst results are obtained for geostationary BeiDou–2
satellites, where the orbit determination suffers from the quasi–static and thus nearly
degenerate viewing geometry. Further studies will be required to investigate the potential1764 Products
Table 2: Representative precision of orbit for new constellations as provided by the MGEX analysis centers in the 2013–2015 time frame
GNSS

Consistency(3D RMS)

SLR

Notes

Galileo
BeiDou10 − 20 cm
20 − 40 cm
few m
20 − 40 cm

10 cm
10 cm
0.5 m
0.2 m

MEO/IGSOGEO

QZSS

benefit of a combined processing of GNSS and laser ranging observations for this class ofsatellites.
Compared to GPS and GLONASS, the orbit determination accuracy achieved for the new
constellations is still substantially lower, which presently limits the use of these products
for high–grade geodetic applications. The inferior performance can in part be attributed
to the specific choice of orbits, the regional visibility of IGSO and GEO satellites, andthe moderate overall number of satellites deployed within each constellation, which impacts the ambiguity success rate. More notably, however, uncertainties in the observation
modeling limit the capability to accurately propagate and adjust the orbits for the new
constellations. These problems refer to the description of• the spacecraft attitude (which affects the modeling of the antenna phase center
location and carrier phase wind–up, but also solar radiation pressure),• the antenna phase center offset and variation (preferably for individual frequencies),• the solar (and Earth) radiation pressure, and• the orbital maneuvers.

As part of the development of relevant models and standards, a harmonized conventionof spacecraft body systems and nominal attitude control laws has been established inclose cooperation of the antenna working group and the MGWG for all constellations andsatellite types (Montenbruck et al. 2015a). So far, conventional values of the phase center
offsets (PCOs) are recommended for use with the new constellations along with dummy(zero) phase center variation (PCV) values. Even though initial estimates for PCOs (andin part PCVs) have been obtained for BeiDou (ESA, WU) and Galileo (DLR, GFZ), theresults are not consolidated, yet. Further comparisons and performance assessments willprobably be required prior to their introduction into the IGS antenna model.
With respect to radiation pressure modeling, the introduction of the new ECOM2 model(Arnold et al. 2015) into the MGEX processing at CODE has shown particularly beneficial
results for Galileo. Similar to the box a priori model proposed earlier by DLR, use of
ECOM2 effectively removes systematic radial errors in the precise orbit products. Despitea better performance of this model (e.g. in terms of SLR residuals) the benefit does not

177Multi–GNSS Working Groupshow up, yet, in the inter–agency comparison, since other MGEX ACs do not presently
use ECOM2 or a suitable a priori box(–wing) model.
To facilitate a precise orbit modeling and the generation of high–grade products, further effort will need to be made to obtain relevant information on the satellites fromthe manufacturer or operator. Information deemed necessary for this purpose include
geometric data (surface dimensions, antenna locations), optical/thermal radiation properties, ground based phase center calibrations and documentation of non–standard attitude(noon/midnight turns, mode transitions).
Aside from orbit and clock products, the multi–GNSS DCB product constitutes a major
contribution of the MGEX analysis centers for the GNSS community. In 2015 the quarter–
annual product provided by DLR since 2014 has been complemented by a new productcontributed by the Institute of Geodesy and Geophysics (IGG) of the Chinese Academyof Sciences (CAS) in Wuhan. This new product is generated on a daily basis to minimize
latency for the user. For performance studies two years of backwards data have also been
provided by IGG.

5 Acronyms and Abbreviations
BKG
CLS
CNES
CODE
DLR
ESA
GFZ
JAXA
RTCM
TUM
WU

Bundesamt für Kartographie und Geodäsie
Collecte Localisation Satellites
Centre National d’Etudes Spatiales
Center for Orbit Determination in Europe
Deutsches Zentrum für Luft– und Raumfahrt
European Space Agency
Deutsches GeoForschungsZentrum
Japan Aerospace Exploration Agency
Radio Technical Commission for Maritime Services
Technische Universität München
Wuhan University

The following list provides an overview of MGEX–related publications issued in 2015 by
the members of the multi–GNSS working group. It does not reflect the much wider list of
publications using MGEX data and providing MGEX–related results that has been madeby the scientific community in this period.

References
Arnold, D., M. Meindl, G. Beutler, R. Dach, S. Schaer, S. Lutz, L. Prange, K. Sosnica, and
L. Mervart. CODE’s new solar radiation pressure model for GNSS orbit determination.
Journal of Geodesy, 89 (8):775–791, 2015. DOI: 10.1007/s00190–015–0814–4.

178

References
Deng, Z., M. Fritsche, M. Uhlemann, and G. Dick. Validation of Multi–GNSS Data
Derived Troposphere Parameters at GFZ. COST ES1206 Workshop, 11–13 May 2015,
Thessaloniki, Greece, 2015a.
Deng, Z., M. Uhlemann, M. Fritsche, G. Dick, and J. Wickert. Troposphere Parameters Derived from Multi–GNSS Data Processing at GFZ. In: Geophysical Research
Abstracts, Vol. 17, EGU2015–10444. Vienna, Austria, 2015b.
El-Mowafy, A., M. Deo, and C. Rizos. On biases in PPP with multi–constellation andmulti–frequency GNSS data. Accepted in Measurement, Science and Technology, 2015.
Fritsche, M., Z. Deng, M. Uhlemann, X. Li, G. Dick, M. Ge. GFZ Analysis Centre: Multi–
GNSS Processing and Products. COST ES1206 Workshop, COST ES1206 Workshop,
11–13 May 2015, Thessaloniki, Greece.
Fritsche, M., Z. Deng, M. Uhlemann, T. Nischan, M. Bradke, M. Ramatschi, A. Brand, and
G. Beeskow. GFZ Analysis Centre: Multi–GNSS Processing and Products. Workshop
on GNSS Biases 2015, 5–6 Nov 2015, Bern, Switzerland, 2015.
Fritsche, M., Z. Deng, M. Uhlemann, T. Nischan, M. Bradke, M. Ramatschi, A. Brandt,
and G. Beeskow. GFZ Analysis Centre: Multi–GNSS Processing and Products. 5thInternational Colloquium – Scientific and Fundamental Aspects of the Galileo Programme, 27–29 Oct 2015, Braunschweig, Germany, 2015.
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, 2016 DOI:10.1007/s00190–015–0862–9
Hackel, S., P. Steigenberger, U. Hugentobler, M. Uhlemann, and O. Montenbruck. Galileo
Orbit Determination using Combined GNSS and SLR Observations. GPS Solutions,19(1):15–25, 2015. DOI:10.1007/s10291–013–0361–5
Langley, R.B. and T. Cozzens. The Almanac: Orbit Data and Resources on Active GNSS
Satellites. GPS World, 26(1):56–58, 2015a.
Langley, R.B. and T. Cozzens. The Almanac: Orbit Data and Resources on Active GNSS
Satellites. GPS World, 26 (8):46–49, 2015b.
Nadarajah, N., P. Teunissen, J.M. Sleewaegen, and O. Montenbruck. The Mixed–Receiver
BeiDou Inter–Satellite–Type Bias and its Impact on RTK Positioning. GPS Solutions,19(3):357–368, 2015 DOI:10.1007/s10291–014–0392–6
Montenbruck, O. MGEX Bias Products. IGS Workshop on GNSS Biases, 5–6 Nov 2015,
Bern, Switzerland, 2015.
Montenbruck, O. and P. Steigenberger. IGS–MGEX: Preparing for a Multi–GNSS World.
National PNT Advisory Board Meeting, 10–12 Jun 2015, Annapolis, MD, 2015.

179

Multi–GNSS Working Group
Montenbruck, O. and A. Hauschild. High–rate clock variations of the Galileo IOV–1/2
satellites and their impact on carrier tracking of geodetic receivers. 5th Int. Colloquium on Scientific and Fundamental Aspects of the Galileo Program, 27–29 Oct 2015,
Braunschweig, Germany, 2015a.
Montenbruck, O. and A. Hauschild. Häberling S., Braun B., Katsigianni G., Hugentobler U. High–rate clock variations of the Galileo IOV–1/2 satellites and their impact on carrier tracking by geodetic receivers. GPS Solutions, 10291–015, 2015b.
DOI:10.1007/s10291–015–0503–z
Montenbruck, O., R. Schmid, F. Mercier, P. Steigenberger, C. Noll, R. Fatkulin, S. Kogure,and A.S. Ganeshan. Satellite Geometry and Attitude Models. Advances in Space
Research, 56 (6):1015–1029, 2015a. DOI:10.1016/j.asr.2015.06.019
Montenbruck, O., P. Steigenberger, and A. Hauschild.
Broadcast vs. Precise
Ephemerides: a Multi–GNSS Perspective. GPS Solutions, 19(2):321–333, 2015b.
DOI:10.1007/s10291–014–0390–8
Montenbruck, O., P. Steigenberger, and U. Hugentobler. Enhanced Solar Radiation
Pressure Modeling for Galileo Satellites. Journal of Geodesy, 89(3):283–297, 2015c.
DOI:10.1007/s00190–014–0774–0
Montenbruck, O., P. Steigenberger, and S. Riley. IRNSS Orbit Determination and Broadcast Ephemeris Assessment. ION International Technical Meeting, 26–28 Jan 2015,
Dana Point, CA, pp. 185–193, 2015e.
Orliac, E., L. Prange, R. Dach, S. Schaer, and A. Jäggi. Assessment of the CODE MGEXClock Products. 26th IUGG General Assembly, 22 Jun–02 Jul 2015, Prague, Czech
Republic, 2015a.
Orliac, E., L. Prange, R. Dach, S. Schaer, and A. Jäggi. MGEX Clock Determination at
CODE. IGS Workshop on GNSS Biases, 5–6 Nov 2015, Bern, Switzerland, 2015b.
Prange, L., R. Dach, S. Lutz, S. Schaer, and A. Jäggi. The CODE MGEX orbit andclock solution Willis P. (Ed.), IAG 150 Years; International Association of Geodesy
Symposia, Vol. 143, Springer, 2015a.
Prange, L., E. Orliac, R. Dach, D. Arnold, G. Beutler, S. Schaer, and A. Jäggi. Jäggi A.;
CODE’s five–system orbit and clock solution for the IGS Multi–GNSS Experimentwith updated orbit model; Submitted to Journal of Geodesy, 2015b.
Prange, L., E. Orliac, R. Dach, D. Arnold, G. Beutler, S. Schaer, and A. Jäggi. CODE’s
multi–GNSS orbit and clock solution. EGU General Assembly 2015, 12 – 17 April
2015, Vienna, Austria, 2015. April 2015, Vienna, Austria (2015c)
Prange, L., E. Orliac, R. Dach, D. Arnold, G. Beutler, S. Schaer, and A. Jäggi. CODE’s
multi–GNSS orbit and clock solution – status 2015. COST Action ES1206 Workshop,
11 – 13 May 2015, Thessaloniki, Greece, 2015d.

180References
Prange, L., E. Orliac, R. Dach, D. Arnold, G. Beutler, S. Schaer, and A. Jäggi. CODE’s
multi–GNSS orbit solution. 5th Int. Colloquium on Scientific and Fundamental Aspects of the System, 27–29 Oct 2015, Braunschweig, Germany, 2015e.
Rizos, C. The International GNSS Service (IGS) in a Multi–Constellation World. Invited
presentation, Xi’an, P.R. China, 12 May 2015, 2015.
Steigenberger, P. and A. Hauschild. First Galileo FOC Satellite on the Air. GPS World,
26(1):8–12, 2015.
Steigenberger, P. and O. Montenbruck. Precise Products of the IGS Multi–GNSS Experiment. COST Action ES1206 Workshop,; 11–13 May 2015, Thessaloniki, Greece,
2015a.
Steigenberger, P. and O. Montenbruck. Precise Orbit and Clock Determination of theGalileo FOC Satellites. 5th Int. Colloquium on Scientific and Fundamental Aspectsof the Galileo Program, 27–29 Oct 2015, Braunschweig, Germany, 2015b.
Steigenberger, P., R. Dach, L. Prange, and O. Montenbruck. Galileo satellite antennamodelling. EGU General Assembly 2015, 12–17 Apr 2015, Vienna, Austria, 2015a.
Steigenberger, P., U. Hugentobler, S. Loyer, F. Perosanz, L. Prange, R. Dach, M. Uhlemann, G. Gendt, and O. Montenbruck. Galileo Orbit and Clock Quality of the
IGS Multi–GNSS Experiment. Advances in Space Research, 55(1):269–281, 2015b.
DOI:10.1016/j.asr.2014.06.030
Steigenberger, P., O. Montenbruck, and U. Hessels. Performance Evaluation of the EarlyCNAV Navigation Message. ION International Technical Meeting, 26–28 Jan. 2015,
Dana Point, CA, pp. 155–163, 2015c.
Steigenberger, P., O. Montenbruck, and U. Hessels. Performance Evaluation of the EarlyCNAV Navigation Message. Navigation–Journal of the ION, 62(3):219–228, 2015d.
DOI:10.1002/navi.111
Steigenberger, P., O. Montenbruck, and U. Hugentobler. E–B Solar Radiation Pressure
Modeling for Precise Orbit Determination. Advances in Space Research, 55(5):1422–
1431, 2015e. e). DOI:10.1016/j.asr.2014.12.009
Uhlemann, M., G. Gendt, M. Ramatschi, and Z. Deng. GFZ Global Multi–GNSS Network
and Data Processing Results. Willis P. (Ed.), IAG 150 Years, International Associationof Geodesy Symposia Vol. 143, Springer, 2015. DOI: 10.1007/1345_2015_120
Uhlemann, M. Galileo–Aktivitäten am GFZ. DGON Navigations Konvent 2015, Berlin,
Germany, 2015.
Václavovic, P., and J. Dousa. New features of Anubis tool for GNSS data quality monitoring. IUGG Assembly 2015, 22 Jun–5 Jul 2015, Prague, Czech Republic, 2015.

181

Multi–GNSS Working GroupWang, N., Y. Yuan, Z. Li, O. Montenbruck, and B. Tan. Determination of differential code biases with multi–GNSS observations. Journal of Geodesy, 2015a. DOI:
10.1007/s00190–015–0867–4
Wang, N., Y. Yuan, Z. Li, O. Montenbruck, B. Zhang, and T. Liu. Multi–GNSS Differential
Code Biases (DCB) Process at IGG. IGS Workshop on GNSS Biases 2015, 5–6 Nov.
2015, Bern, Switzerland, 2015b.
White, R.M. and R.B. Langley. Precise Point Positioning with Galileo Observables. Proceedings of 5th Int. Colloquium on Scientific and Fundamental Aspects of the Galileo
Programme, 27–29 Oct 2015, Braunschweig, Germany, 2015.
Zhao, Q., J. Guo, X. Xu, G. Chen, and C. Wang. Precise orbit determination for quad–
constellation satellites: strategy, comparison, and validation. China Satellite Navigation Conference 2015, 13 May 2015, Xi’an, China, 2015.

182

Reference Frame Working Group
Technical Report 2015
P. Rebischung1 , B. Garayt2 , Z. Altamimi1
1

2

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

1 Introduction
Besides a continuous quality monitoring of the operational IGS SINEX combination products (Sect. 1), the main activity of the Reference Frame Working Group in 2015 was the
finalization of the IGS contribution to ITRF2014, which consists of daily combinations of
the AC SINEX solutions from the IGS 2nd reprocessing campaign (Sect. 3).

2 Operational SINEX combinations
Figure 1 shows the RMS of the AC station position residuals from the daily IGS SINEX
combinations of year 2015, i.e. the global level of agreement between the AC and IGS
combined station positions once reference frame differences have been removed. Unlike in2014, where successive updates of the AC’s analysis strategies translated into a progressive
improvement of the inter–AC agreement (Rebischung et al. 2015), the RMS of the ACstation position residuals have remained at nearly constant levels in 2015.
Figures 2 and 3 show the AC Earth Orientation Parameter (EOP) residuals from the IGS
SINEX combinations of year 2015. The inter–AC agreement on EOPs has not shown any
major evolution either in 2015. Simply note that SIO’s pole rate estimates have been
included back with weight in the daily IGS SINEX combinations since week 1832.

183

Reference Frame Working Group

4 mm

East

4 mm

3 mm

3 mm

2 mm

2 mm

1 mm

1 mm

0 mm

North

0 mm
1830

1840

1850

1860

1870

8 mm

1830

1840

1850

1860

1870

Up

6 mm

cod

gfz

mit

4 mm

emr

grg

ngs

2 mm

esa

jpl

sio

0 mm
1830

1840

1850

1860

1870

GPS week

Figure 1: RMS of AC station position residuals from the 2015 daily IGS SINEX combinations.
All time series were low–pass filtered with a 10 cycles per year cut–off frequency.

xp residuals (mas)yp residuals (mas)

0.0

0.0

cod

−0.2

−0.2

emr

−0.4

−0.4

esa

−0.6

−0.6

gfz

−0.8

−0.8

grg

−1.0

−1.0

jpl

−1.2

−1.2

mit

−1.4

−1.4

ngs

−1.6

−1.6

sio

1830

1840

1850

1860

GPS week

1870

1830

1840

1850

1860

1870

GPS week

Figure 2: AC pole coordinate residuals from the 2015 daily IGS SINEX combinations. The
individual AC time series have been shifted by multiples of 0.2 mas for clarity.

184

3 The IGS contribution to ITRF2014
xp rate residuals (mas/d)

yp rate residuals (mas/d)

LOD residuals (ms)

0

0

0.0

cod

−1

−1

−0.1

emr

−2

−2

−0.2

esa

−3

−3

−0.3

gfz

−4

−4

−0.4

grg

−5

−5

−0.5

jpl

−6

−6

−0.6

mit

−7

−7

−0.7

ngs

−8

−8

−0.8

sio

1830

1840

1850

1860

GPS week

1870

1830

1840

1850

1860

1870

GPS week

1830

1840

1850

1860

1870

GPS week

Figure 3: AC pole rate and LOD residuals from the 2015 daily IGS SINEX combinations. The
individual AC time series have been shifted by multiples of 1 mas/d and 0.1 ms forclarity.

3 The IGS contribution to ITRF2014
The IGS contribution to ITRF2014 is based on the products from the second IGS reprocessing campaign (repro2). A complete list of the models and conventions used in the
repro2 data analyses can be found at http://acc.igs.org/reprocess2.html. A total of
9 ACs contributed to the repro2 campaign and provided daily terrestrial frame (SINEX)
solutions among other products. The AC repro2 SINEX time series were extended withconsistent operational products up to GPS week 1831, when available, and daily combinations of the AC repro2+operational SINEX solutions were performed over the period
1994–01–02 to 2015–02–14 (GPS weeks 730 to 1831). The resulting daily combined SINEX
solutions, named ig2, were made available on February 27, 2015 (IGSMAIL–7055) andcan be retrieved from the IGS global data centers. They constitute the IGS contribution
to ITRF2014.
From WRMS values of the residuals of the daily repro2 combinations, the overall inter–AC level of agreement is assessed to be 1.5 mm for the horizontal components and 4 mm
for the vertical component of station positions, 25–40 µas for pole coordinates, 140–200µas/d for pole rates, 8–20 µs/d for calibrated LOD estimates, 4 mm for the X and Y
components of geocenter motion, 8 mm for its Z component and 0.5 mm for the terrestrial
scale. On the long term, the origins (resp. scales) of the AC terrestrial frames show relative
offsets and rates within ±3 mm and ±0.3 mm/yr (resp. ±0.5 mm and ±0.05 mm/yr). The
combination residuals also present AC–specific features, some of which are explained by
known analysis specifics, while others remain under investigation.
See Rebischung et al. 2016 for a complete description of the repro2 SINEX combination
methodology and results.

185

Reference Frame Working Group

References
Rebischung, P., B. Garayt, X. Collilieux, and Z. Altamimi. IGS Reference Frame Working
Group Coordinator Report 2014. In: Y. Jean and R. Dach (eds.): IGS Technical Report 2014, International GNSS Service, pp. 179–185, ftp://igs.org/pub/resource/
pubs/2014_techreport.pdf, 2015.
Rebischung, P., Z. Altamimi, J. Ray, and B. Garayt. The IGS contribution to ITRF2014.
Journal of Geodesy, 2016 (in press).

186

Real–Time Service
Technical Report 2015
L. Agrotis1 , M. Caissy2 , A. Rülke3
1
2
3

ESA/ESOC
Natural Resources Canada
BKG

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

2 WG membership
Loukis Agrotis (ESA)
Axel Rülke (BKG)

187

Real–Time Service
Steve Fisher (JPL)
Allison Cradock (JPL)Mark Caissy (NRCan)
Georg Weber (BKG)
Guillermo Tobías González (GMV)
Manuel Hernandez–Pajares (UPC)
Andre Hauschild (DLR)
Denis Laurichesse (CNES)
Martin Schmitz (GEO++)
Gerhard Wubbena (GEO++)
Ken Macleod (NRCan)
Lou Estey (UNAVCO)
Erik Vigen (Fugro)
Carey Noll (CDDIS)
Mathias Fritsche (GFZ)
John Braun (UCAR)
Fabian Hinterberger (TUW)
IGS Working Group Chairs
IGS Analysis Center Representatives
ex officio: R. Neilan (JPL), Kevin Choi (NGS)

3 Summary of Activities in 2015
• GPS–only combinations from ESOC and BKG were continuously available without
significant performance issues.
– Two outages of IGS01 and IGC01 were encountered over two weekends. The
cause was due to issues with the RTCM ephemeris streams that are used for
stream encoding/decoding.
– There was an issue with encoding/decoding of G03 on 7 December, which
resulted in a corruption of the results for that satellite.
– Occasional performance degradation is still observed when Block IIA satellites
are in eclipse.
– Orbit performance degradation of the Block IIF satellites was observed in several instances. The suspected cause is uncertainty in the radiation pressure
modeling, probably related to non–nominal spacecraft attitude.
• Focus on GLONASS products to promote AC improvements– Four AC streams and the GPS+GLONASS combination stream IGS03 are188

4 Plan in 2016
monitored by the ACC.
– One stream, from DLR, is currently unavailable, leaving 3 available AC solutions.
– Daily clock comparisons against the ESA rapid products are made available byemail.
– PPP monitoring is performed continuously by BKG.
– There are still encoding/decoding issues with GLONASS, but steps are in place
to update software in order to eliminate them.
• Members of the WG participated in RTCM meetings in the US. Concerns on competition with commercial services and magnitude of implementation effort are still
holding back acceptance of the SSR format extensions for ambiguity resolution andsupport for additional constellations (Galileo, QZSS and Beidou). Adoption of the
RTCM MSM format for multi–GNSS observation streaming in receiver firmware is
finally starting to appear. The standards for Beidou and Galileo I/NAV ephemeris
messages have not yet been approved, so the MGEX streams are using draft formats
for these. However, these messages cannot yet be streamed directly from receiver
firmware.
• The latest statistics for registrations to the IGSCB caster: (unavailable at time of
preparation. Update will be provided ASAP.
• A presentation on the RTS status was given at the IUGG (Axel Ruelke).

4 Plan in 2016
• Encourage additional RTAC’s to contribute GLONASS solutions• Improve the reliability of the broadcast ephemeris streams used by RTAC’s.

• Encourage processing of MGEX streams. One key objective is that all RTACs become able to use MSM streams in their routine RTS processes.
• Participation in SSR interoperability testing – for example ambiguity fixing andionosphere• Contact station operators and encourage the delivery, when possible, of a minimumof two streams to separate independent real–time data centers/casters.
• Optimization of real time observation data infrastructure in order– to reduce the total latency– avoid bandwidth problems at specific data centers

189

Real–Time Service– improve reliability• Discussion on objectives of the IGS RTS (possible product limitations, broadcasting
methods, competition with commercial providers etc.)• Participation of some members in a newly formed IAG Real Time Ionosphere working
group, starting work in 2016

190

RINEX/RTCM Working Group
Technical Report 2015
Ken MacLeod1 , Loukis Agrotis2
1
2

Canadian Geodetic Survey, Canada
E–mail: ken.macleod@canada.ca
ESOC
E–mail: loukis.agrotis@esa.int

1 Highlights in 2015
• RINEX Version 3.03 released in July, 2015. Most significant updates include:– Addition of the Indian Regional Navigation Satellite System (IRNSS) Constellation– Updates to support BeiDou– Numerous message clarifications– Additional App. ?? RINEX 3.0x support is strong within both the IGS and
RTCM–SC104.
– Application support for RINEX 3.0x is growing.
• Formation of the RTCM–SC104/IGS GNSS Receiver Calibration Working Group:– This effort involves the cooperation of RTCM–SC104 members, the IGS Bias
Working Group and NRCan. The calibration site is located in Ottawa, Canada
and operated by Natural Resources Canada. The site hardware and infrastructure is at the initial operation stage.

• RTCM–SC104 Activities:– RTCM–Multiple Signal Messages (RTCM–MSM) now support all constellations(with the exception of SBAS (patent issue)). However, approval is still pending for ephemeris messages for Galileo I/NAV and Beidou. RTCM State Space
Representation (RTCM–SSR) messages are used by the IGS Real–Time Service.

191

RINEX/RTCM Working Group
Currently there are several draft messages being defined (at the interoperability testing stage) they include: GPS and GLONASS phase bias, Vertical TEC(VTEC) and Galileo and QZSS orbit and clock correction messages. At the last
meeting (September, 2015) the committee voted to proceed with: the VTEC
and Galileo and QZSS Stage 1 messages. However, the GPS and GLONASS
phase bias messages were not recommended as the committee determined that
there was insufficient interoperability testing. Geo++ are leading this effort
and are reassessing their options and deciding how to proceed. At this time
IGS partners are using draft experimental message formats (testing and development) and the delay in message approval is not significant. However, if themessages are delayed for too long it could become a problem.

2 Plans in 2016
• Continue to update the RINEX 3.0x documentation to meet the needs of the GNSS
community.
• Work with RTCM–SC104 to define a new navigation message to support the contentsof the GPS CNAV messages.
• Work with the RINEX WG to define a RINEX CNAV message.
• Release a draft CNAV format in 2016.

• Update RINEX 3.0x to a new version number when there is a significant change(once a year at the most)• Work with the IGS and RTCM Bias Working group to define the standard operatingprocedure of the working group. This includes:– Equipment and data sharing and observing procedures– Work towards having the calibration site in initial operations in the first halfof 2016– Enter into production in the second half of 2016
– Data from receivers running released firmware will be freely available. If receiver, beta firmware is being tested access to the data may be restricted (non–disclosure agreement required).
• Attend RTCM–SC104 North American meetings (Loukis Agrotis attends European
meetings; Ken MacLeod attends North American meetings).
– Ensure that RTCM–SC104 messages meet the needs of the IGS and high precision GNSS community.

192

3 RINEX WG Membership List
– Communicate and coordinate IGS partner’s needs to the RTCM. Prepare meeting reports for the IGS Governing Board.

3 RINEX WG Membership List
Table 1: RINEX WG Membership#

Name

Institution

Country

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52

Agrotis, L.
ESOC
Great Britain
Alves, P.
Hemisphere GNSSCanada
Artushkin, I.
AshtechRussiaBagge, A.
Geo++
Germany
Boriskin, A.
AshtechRussiaBrockmann, E. Swiss Topo
Switzerland
Colombo, O.
NASA
USA
Dach, R.
U of Bern
Switzerland
Ellum, C.
NovatelCanadaEstey, L.
UNAVCOUSA
Euler, H. J.
Inposition
Switzerland
Ferguson, K.
Hemisphere GNSS
Habrich, H.
BKG
GermanyHan, S.
BeiDouChina
Hatanaka, Y.
GSI
Japan
Hauschild, A.
DLR
Germany
Hedling, G.
Land Survey
SwedenHilla, SNGSUSA
Hirokawa, R.
Mitsubishi
Japan
Honghe, H.
BeiDou Office
China
Kaori, K.
JAXA
Japan
Kirchner, M.
Astrium
Germany
Kolosov, D.
TopconRussiaKopcha, P.
NGA
USA
Kozlov, D.
AshtechRussiaLemoine, B.
Hemisphere
CanadaLiu, L.
BeiDouChina
Lu, G.
TrimbleUSA
MacLeod, K.
NRCanCanadaMarukawa, Y.
NEC
Japan
Miyoshi, M.
JAXA
Japan
Montenbruck, O. DLR
Germany
Nischan, T
GFZGermany
Noack, T.
DLR
Germany
Pache, F.
Leica Geo.
Switzerland
Petersen, T.
TrimbleUSA
Renfro, B.
U of Texas
ESA
Roesler, G.
NovatelCanadaRomero, I.
ESOCEU
Rossbach, U.
IFEN
Germany
Sass, Joe
Spectra Precision USA
Schmitz, M.
Geo++
Germany
Sleewaegen, J. M.Septentrio
Belgium
Springer, T.
ESA
Germany
Stansell, T.
Stansell C
USA
Stoecker, D.
AlberdingGermany
Stuerze, A.
BKG
Germany
Takac, F.
Leica Geo.
Switzerland
Weber, G.
NTRIP.org
Germany
Willems, T.
Septentrio
Belgium
Wuebbena, G.
Geo++
Germany
Zinoviev, A.
TopconRussiaE–mailloukis.agrotis@esa.int
palves@hemispheregnss.com
iartushkin@ashtech.com
andreas.bagge@geopp.deaboriskin@ashtech.com
elmar.brockmann@swisstopo.chocolombo@puuoo.gsfc.nasa.gov
rolf.dach@aiub.unibe.chcameron.ellum@novatel.com
lou@unavco.org
h-j.euler@inposition.chkferguson@hemispheregnss.com
heinz.habrich@bkg.bund.deshaowei.han@sbcglobal.net
hata@gsi.go.jp
andre.hauschild@dlr.de
gunnar.hedling@lm.se
steve.hilla@noaa.gov
hirokawa.rui@mitsubishielectric.co.jp
haohh@beidou.gov.cn
kawate.kaori@jaxa.com
michael.kirchner@astrium.eads.net
dkolosov@topcon.com
peter.d.kopcha@nga.mil
dkozlov@ashtech.com
blemoine@hemispheregps.com
loweliu@hotmail.com
gang_lu@trimble.com
ken.macleod@canada.ca
y-marukawa@aj.jp.nec.com
miyoshi.motoyuki@jaxa.jp
oliver.montenbruck@dlr.debackslashnisn@gfz-potsdam.dethoralf.noack@dlr.defranck.pache@leica-geosystems.com
tim_petersen@trimble.com
renfrob@arlut.utexas.edu
greg.roesler@novatel.com
nacho@canaryadvancedsolutions.com
u.rossbach@ifen.com
joe_sass@spectraprecision.com
martin.schmitz@geopp.dejm.sleewaegen@septentrio.com
tim.springer@esa.int
tom@stansell.com
dirk.stoecker@alberding.eu
backslashandrea.stuerze@bkg.bund.defrank.takac@leica-geosystems.com
georg.webber@ntrip.det.willems@septentrio.com
gerhard.wuebbena@geopp.deazinoviev@topcon.com

193

RINEX/RTCM Working Group194

Tide Gauge Benchmark
Monitoring Working Group
Technical Report 2015
T. Schöne, R. Bingley, Z. Deng, M. Gravelle,
J. Griffiths, M. Guichard, H. Habrich, D. Hansen,
A. Hunegnaw, M. Jia, M. King, M. Merrifield,
G. Mitchum, R. Neilan, C. Noll, E. Prouteau,
L. Sánchez, A. Santamaría–Gómez,N. Teferle, D. Thaller, P. Tregoning,
S. Williams, G. Wöppelmann

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.
TIGA provides vertical geocentric positions, vertical motion and displacements of GNSS
stations at or near a global network of tide gauges. To a large extend the TIGA Working
Group uses the infrastructure and expertise of the IGS.
The main aims of the TIGA Working Group are:
• Maintain a global virtual continuous GNSS Tide Gauge network• Compute precise coordinates and velocities of GNSS stations at or near tide gauges
with a significant delay to allow as many as possible stations to participate. Provide
a combined solution as the TIGA official product.
• Study the impacts of corrections and new models on the GNSS processing of thevertical coordinate. Encourage other groups to establish complementary sensors to
improve the GNSS results, e.g., absolute gravity sites.
• Provide advice to new applications and installations.

195

Tide Gauge Benchmark Monitoring Working Group

2 Main Progress in 2015
• TIGA Working Group members primarily continued with the reprocessing of the
TIGA network. Nearly 800 GNSSTG stations and IGS08b core sites are processedby the TIGA Analysis Centers.
• Two of the TIGA centers significantly contributed to the IGS repro2.

• Members participated in the GLOSS-GE14 in Goa (India); http://ioc-unesco.
org/index.php?option=com_oe&task=viewEventRecord&eventID=1534; reports havebeen given by the TIGA-WG and the SONEL data center• Participation/reporting in/at the IUGG 2015 (Prague) meeting.

• TIGA Network operator works with Tide Gauge and GNSS station operators tomake existing stations available to TIGA
• 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 thedensification and extension of the TIGA Observing Network to GGOS.

Table 1: TIGA Working Group Members in 2015
Name

EntityHost Institution

Country

Guy Wöppelmann
Laura Sánchez
Heinz Habrich
Minghai Jia
Paul Tregoning
Zhiguo Deng
Daniela Thaller
Norman Teferle
Richard Bingley
Ruth Neilan

TAC, TNC, TDC
TAC
TAC

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

FranceGermany
Germany
Australia
Australia
Germany
Switzerland
Luxembourg
UK
USA

Carey Noll
Tilo Schöne
Simon Williams
Gary Mitchum
Mark Merrifield
Matt King

196

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

USA
Germany
UK
USA
USA
Australia

Troposphere Working Group
Technical Report 2015
C. Hackman, S. M. Byram
United States Naval Observatory
3450 Massachusetts Avenue Northwest
Washington DC 20392 USA
E–mail: christine.hackman@usno.navy.mil
Tel. +1–202–762–1444

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 2015
USNO produces IGS Final Troposphere Estimates for nearly all of the stations of the
IGS network. Each 24–hr site result file provides five–minute–spaced estimates of total
troposphere zenith path delay (ZPD), north, and east gradient components, with thegradient components used to compensate for tropospheric asymmetry.
IGS Final Troposphere estimates are generated via Bernese GPS Software 5.0 (Dach et al.
2007) using precise point positioning (PPP; Zumberge et al. 1997) and the GMF mapping197

Troposphere Working Groupfunction (Boehm et al. 2006) with IGS Final satellite orbits/clocks and earth orientation
parameters (EOPs) as input. Each site–day’s results are completed approximately three
weeks after measurement collection as the requisite IGS Final orbit products become
available. Further processing details can be obtained from Byram and Hackman 2012.
Figure 1 shows the number of receivers for which USNO computed IGS FTEs 2011–
5. The average number of quality–checked station result files submitted per day in2015 was 323, slightly lower than the 2014 average value of 326 due to an aging of thestation–identification file used to download observations for processing. This station–
identification file was updated in December 2015; since then, the average number of station files submitted per day has risen to nearly 350. The result files can be downloaded
from ftp://cddis.gsfc.nasa.gov/gps/products/troposphere/zpd. 20.9 million files
were downloaded in 2015 by users from approximately 1900 distinct hosts (Noll 2016), amarked increase in usage over the 10.3 million files downloaded in 2014.
USNO will use Bernese GNSS Software 5.2 (www.bernese.unibe.ch/features) to compute troposphere estimates for the IGS Reprocessing 2 effort (http://acc.igs.org/
reprocess2.html).

Number, QC-ed Tropo Files Submitted to IGS
update station list

350

update station list

improved results screening# receivers for which files submitted

400

300

250
2011
mean: 322

2012
mean: 302

2013
mean: 325

2014
mean: 326

2015
mean: 323

200
0

365

730
1095
days since 1 Jan 2011

1460

1825

Figure 1: Number of IGS receivers for which USNO produced IGS Final Troposphere Estimates,
2011-5. (Estimates were produced by Jet Propulsion Laboratory up through mid-April
2011.)

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3 IGS Troposphere Working Group Activities 2015

3 IGS Troposphere Working Group Activities 2015
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 biennial IGS Analysis Workshop.
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 Working group meetings
The working group met twice in 2015: on 15 April 2015 at the Technical University of
Vienna (in conjunction with EGU) and on 15 December 2015 in San Francisco, CA (inconjunction with AGU).
The April 2015 meeting featured presentations by:• WG chair C. Hackman on– the quality and production of IGS Final Troposphere Estimates– the status of current working–group projects• Dr. Rosa Pacione (e–geos, ASI/CGS1 ; Italy) on– the status of tropo_sinex standardization efforts (see “Working Group Projects,”
below)The December 2015 meeting featured a status report by outgoing–chair C. Hackman on• quality/production of IGS Final Troposphere Estimates• current working group projects• the leadership transition to incoming chair Dr. Sharyl Byram

Presentations from both meetings were distributed via the IGS TWG email list (message
IGS–TWG–137) and can be obtained by contacting this report’s first author.
1

Agenzia Spaziale Italiana/Centre for Space Geodesy

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Troposphere Working Group

3.2 Working group projects• 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 comparethem to those obtained for the same time/location using an independent measurement technique, e.g., VLBI2 , DORIS3 , radiosondes, or from a numerical weathermodel. Comparisons of 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 can contact Dr. Dousa 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 with supporting documents authored by WG chair C. Hackman, wasfunded. 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 3–13 November 2015.
Completion of this project is expected in 2016. This system has received interest
from climatologists/meteorologists, e.g., those associated with the GRUAN4 and
COST5 Action 1206 (GNSS4SWEC) projects, as it will simplify quality–comparisonand perhaps acquisition of data used as input to their studies.
• Standardization of the tropo_sinex format

The IGS Troposphere Working group also supports a project to standardize thetropo_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 STDEV and STDDEV are used to denote standard deviation

2

Very Long Baseline Interferometry
Doppler Orbitography and Radiopositioning Integrated by Satellite
4
GCOS (Global Climate Observing System) Reference Upper Air Network: http://www.gruan.org
5European Cooperation in Science and Technology: http://www.cost.eu
3200

4 How to Obtain Further Informationin 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
IAG6 organizations and other communities; its work is further supported by the
EUREF Technical Working Group7 as well as E–GVAP8 expert teams. The WG iscurrently 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 2015 on
a proposed “SLANT/SOLUTION BLOCK”. For more information, please contact
Dr. Pacione at rosa.pacione@e-geos-it or Dr. Douša.

3.3 Presentation at FIG Working Week 2015 ; preparations for 2016 IGS
Workshop• A presentation highlighting the IGS and its troposphere–related activities, “International GNSS Service (IGS) Troposphere Products and Working Group Activities,”
authors C. Hackman, G. Guerova, S. Byram, J. Dousa and U. Hugentobler, wasdelivered by G Guerova 18 May 2015 at FIG9 Working Week 2015, Sofia Bulgaria,
with the corresponding article published in the conference proceedings.
• Incoming chair Dr. Sharyl Byram began organizing troposphere–related activities
for the then–future 2016 IGS Workshop, soliciting presenters for the troposphereplenary and poster sessions, and planning the working–group meeting to be held
there.

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
6International Association of Geodesy
http://www.euref.eu/euref_twg.html
8
EUMETNET EIG GNSS Water Vapour Programme; http://egvap.dmi.dk
9International Federation of Surveyors; http://www.fig.net
7201

Troposphere Working GroupTo 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://igs.org/projects-working-groups/
twg, and/or• subscribe to its email list: http://igscb.jpl.nasa.gov/mailman/listinfo/igs-twg

5 Acknowledgements
Development of the troposphere–comparison database/website is supported by KONTAKT II project number LH14089. The authors furthermore thank the Technical University of Vienna (especially J. Boehm, S. Linsmayer and G. Moeller) for hosting theApril 2015 working group meeting, IGS/UNAVCO (especially A. Craddock) for providing
a room for the December 2015 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.
Dach, R., U. Hugentobler, P. Fridez, and M. Meindl. Bernese GPS Software Version 5.0(User Manual). Astronomical Institute of University of Bern, Bern, Switzerland, 2007.
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, 2016.
Hackman, C., G. Guerova, S. Byram, J. Dousa, 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, 2016.

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References
Zumberge, J.F., M.B. Heflin, D.C. Jefferson, M.M. Watkins, and F.H. Webb. Precise Point
Positioning for the Efficient and Robust Analysis of GPS Data from Large Networks.
J. Geophys. Res., 102(B3):5005–17, 1997.

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Troposphere Working GroupAppendix 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
Dousa
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

204

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

205

Troposphere Working GroupAppendix 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.

206

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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Troposphere Working Group

208

g

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