IGS Analysis Center Coordinator (ACC) run by Geoscience Australia and MIT
General Information About the IGS Products
This site gives information about the products of the
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. 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 periods 2008-2011 and 2012-2015, the IGS ACC functions are performed by
NOAA's National Geodetic
Survey (NGS) in Silver Spring, Maryland, USA. During previous periods,
the ACC functions were performed by the
GeoForschnungsZentrum (GFZ Department 1) in Potsdam, Germany (2003-2008),
Center for Orbit Determination in Europe (CODE) in Bern, Switzerland
and Vienna, Austria (1999-2003), and
Natural Resources Canada (NRC) in Ottawa, Canada (1994-1998).
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
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
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
The next 24 hours of each file are predicted orbits, extrapolated from
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
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.