IGS Analysis Center Coordinator (ACC) at NOAA/NGS
General Information About the IGS Products
This site gives information about the products of the
International GNSS
Service (IGS),
especially their quality. This introductory page provides general background
information. Most of the other pages here contain figures and tables
summarizing the results from the IGS product combinations. Those pages
are mainly of interest to the
IGS Analysis Centers and other GNSS specialists.
The tables and figures for the Final products are updated weekly.
Other pages are updated shortly after the corresponding combinations. The
figures show the results of the past 60 weeks except for the "Final (ALL)"
plots which show the results of the IGS orbit combinations since their
beginning in late 1993.
The IGS Analysis Center Coordinator (ACC) has overall responsibility
for generating the main official IGS combined products. During the
period 2008-2011, the IGS ACC functions are performed by
NOAA's National Geodetic
Survey (NGS) in Silver Spring, Maryland, USA. Currently, there
are three IGS product lines for GNSS satellite orbits and clocks, namely
the IGS Final, the IGS Rapid, and the IGS Ultra-rapid products. During
the previous period, the ACC functions were performed by the
GeoForschnungsZentrum (Department 1) in Potsdam, Germany.
Certain IGS product combination tasks are shared. For the Final products,
those components involving the terrestrial reference frame, including
the Earth rotation parameters, are produced by a combination of SINEX
file submissions, work done at
Natural Resources Canada in Ottawa, Ontario, Canada, through January
2010 and done since that time at
Institut Géographique
National in Paris, France. The internally
realized timescales of the IGS, formed by a weighted ensemble of the
frequency standards available in the IGS clock products, are maintained
by the Naval
Research Laboratory, Space Applications Branch, in Washington, DC,
USA. Such high-stability timescales are supported for the IGS Rapid and
Final products.
The available IGS products are:
- IGS Final products (IGS)
The IGS Final products have the highest quality and internal
consistency of all IGS products.
They are made available on a weekly basis, by each Friday, with a delay
up to 13 (for the last day of the week) to 20 (for the first day of the
week) days. The IGS Final products are the basis for the IGS reference
frame and are intended for those applications demanding high
consistency and quality.
- IGS Rapid products (IGR)
The IGS Rapid products have a quality nearly comparable to that of the Final
products. They are made available on a daily basis with a delay of about
17 hours after the end of the previous observation day; i.e., the IGS Rapid
products are released daily at about 17:00 UTC. For most applications
the user of IGS products will not notice any significant
differences between results obtained using the IGS Final and
the IGS Rapid products.
- IGS Ultra-rapid products (IGU)
To reduce the age of the prior, discontinued Predicted orbits, the IGS
started the Ultra-rapid products officially week 1087, in November
2000. Like the former IGS Predicted products, the Ultra-rapid
products are available for real time and near real time use.
The Ultra-rapid products are released four times per day, at 03:00,
09:00, 15:00, and 21:00 UTC. (Until week 1267 they were released twice
daily.) In this way the average age of the predictions is reduced to
6 hours (compared to 36 hours for the old IGS Predicted products
and 9 hours for the twice-daily Ultra-rapids). The shorter latency
should lead to significantly improved orbit predictions and reduced
errors for user applications.
Contrary to all other IGS orbit products the IGS Ultra-rapid orbit files
contain 48 hours of tabulated orbital ephemerides, and the start/stop
epochs continuously shift by 6 hours with each update. All other orbit
products contain strictly the 24 hours from 00:00 to 23:45.
The first 24 hours of each IGS Ultra-rapid orbit are based on the most
recent GPS observational data from the IGS hourly tracking network.
At the time of release, the observed orbits have an initial latency of
3 hours.
The next 24 hours of each file are predicted orbits, extrapolated from
the observed
orbits. The orbits within each Ultra-rapid product file are, however,
continuous at the boundary between the observed and predicted parts.
Normally, the predicted orbits between 3 and 9 hours into the second
half of each Ultra-rapid orbit file are most relevant for true real time
applications.
Where to get more information about the IGS ?
For more information about the International GNSS Service please visit
the IGS Central Bureau, which is located at the Jet Propulsion Laboratory in
Pasadena, California, USA.
- Some especially helpful IGSCB pages:
Where and when to get IGS products ?
For product archive locations at the
IGS Global Data Centers
please refer to the information in the link below.
How to use IGS products?
The links below address some frequently asked questions regarding the
generation and use of IGS products.
General Information
- "A Guide to Using IGS Products"
by J. Kouba (May 2009)
- Status of
IGS orbit products (IGS Mail 6053, 7 January 2010)
- IGS Workshop 2010,
28 June-2 July 2010, Newcastle upon Tyne
File Formats
- RINEX updates to handle
phase shifts & other new features
- IGS file formats
- IGS ERP file format (version 2)
- IGS table of receiver and antenna equipment
Terrestrial Reference Frame
- Since
week 1400 the IGS reference frame is IGS05 (IGS Mails 5447
&
5455)
- Change of
IGS Reference Frame Coordinator
(IGS Mail 6067, 28 January 2010;
IGS Mail 6070, 02 February 2010)
SP3 Satellite Files
- Use the SP3 orbit accuracy codes
- Handling IGS reference frame changes
- SP3 orbit interpolation algorithms:
- Syntax of SP3 file comment lines
- Perl script to convert IGS orbit
files from current SP3C format to obsolete SP3A (from G. Gendt &
Th. Nischan); see IGS Mail 5000
Antenna Information
- How to use IGS antenna
phase center corrections (GPS World Tech Talk, 03 February 2010)
- General information on IGS antennna files
- Background on IGS
antenna calibrations (IGS Mail 5189)
- IGS switch to
absolute antenna calibrations & IGS05 frame starting week 1400
(IGS Mail 5438)
- Current antenna calibration file
(igs05.atx)
- IGS conventions for SINEX antenna + radome
information
Inter-Signal Code Biases
- Latest version (v6.2) of cc2noncc.f routine
(from ESA group at European Space Operations Centre)
- Information on
P1-C1 code biases (from CODE group at Astonomical Institute, University of
Bern)
- File of historic
P1-C1 code bias values (from ESA group at European Space Operations Centre)
Recent Changes, Announcements, Notices, & Reports
- IGS Workshop 2010,
28 June-2 July 2010, Newcastle upon Tyne
(IGS Mail 6075, 12 Feb 2010)
- Change of
IGS Reference Frame Coordinator
(IGS Mail 6067, 28 January 2010;
IGS Mail 6070, 02 February 2010)
- Status of
IGS orbit products (IGS Mail 6053, 7 January 2010)
- Proposed change
to IGL sp3 file contents postponed (IGS Mail 6007, 29 September 2009)
- Calls
for next-generation IGS combination system & for next Analysis Center
Coordinator (IGS Mail 5984, 13 August 2009)
- IGS submission for ITRF2008
extended to add reprocessed years 1997 - 1999 (22 July 2009)
- IGU clock prediction
exclusion policy modified (IGS Mail 5969, 14 July 2009)
- Exclusion of
some IGU satellite clock predictions (IGS Mail 5965, 1 July 2009)
- C2 data
versus P2 data (IGS Station Mail 3163, 29 June 2009)
- Precise Point
Positioning Software Centre (IGS Mail 5949, 22 May 2009)
- IERS Workshop
on EOP Combination & Prediction, 19-21 October 2009, Warsaw (IGS Mail 5943, 8 May 2009)
- IGS combined SINEX solution for
reprocessed years 2000-2008 submitted to IERS for ITRF2008
(19 February 2009)
- Final 30s
clock products modified (IGS Mail 5902, 19 February 2009)
- Status of
IGS Ultra-rapid products (IGS Mail 5874, 2 January 2009)
Miscellaneous advice and information for ACs
25 February 2010, originator J. Ray