05/05/03 12.540 Lec 21 1
12.540 Principles of the Global
Positioning System
Lecture 21
Prof. Thomas Herring
05/05/03 12.540 Lec 21 2
– Major international organizations involved in GPS
– Examine access to GPS data
– Examine access to GPS results
Summary
? Sources of GPS data and results
1
GPS Groups/IGS
? There are many international and national groups
involved in the deployment of GPS.
? The international organization is the International GPS
Service (IGS)
? Started as pilot project by the International
Association of Geodesy (IAG) in 1992.
? Involves:
– Data collection (standards for stations)
– Data dissemination (through several archives)
– Data analysis (IGS analysis centers)
– Analysis improvements (working groups and standards)
05/05/03 12.540 Lec 21 3
05/05/03 12.540 Lec 21 4
Current IGS Network (approximately 200 stations)
2
05/05/03 12.540 Lec 21 5
North American Portion of network
05/05/03 12.540 Lec 21 6
European part of network
3
05/05/03 12.540 Lec 21 7
IGS
http://igscb.jpl.nasa.gov/
05/05/03 12.540 Lec 21 8
http://www.scign.org/
? Data for each IGS station is openly available
usually within <1 day of collection. Some sites
are available hourly.
? The central bureau of the IGS is located at:
? Explore site for structure: Web site index gives
an overview of page content.
US Groups
? There are a number of large US groups that
run GPS networks.
? Largest array is the Southern California
Integrated array (SCIGN) with 250 stations
? Other groups in the Western United States
have networks of 20-50 stations. In all over
400 geophysical class stations in Western US.
4
National Geodetic Survey CORS
? Main reference frame of the United States.
? Continuously Operating Reference Stations
(CORS)
? http://www.ngs.noaa.gov/CORS/
? Serves the geodetic control needs of the US.
? About 300 GPS sites currently in the network
many of them shared with other institutions.
05/05/03 12.540 Lec 21 9
Western US Groups
? Networks in the Western United States
– BARD (Bay Area Regional Network)
http://quake.geo.berkeley.edu/bard/
– PANGA (Pacific Northwest Geodetic Array)
http://www.panga.cwu.edu/
http://www.geophys.washington.edu/GPS/gps.html
– WCDA Western Canada Deformation Array
http://www.pgc.nrcan.gc.ca/geodyn/wcda.htm
– BARGEN (Basin and Range Geodetic Network)
http://cfa-www.harvard.edu/space_geodesy/BARGEN/
– For list of arrays see:
http://sopac.ucsd.edu/cgi-bin/dbShowArraySitesMap.cgi
? Explore these web sites.
05/05/03 12.540 Lec 21 10
5
Availability of processed GPS data
? Many of the network groups put analyzed results on
their web pages as well as access to data.
? IGS also sponsors 7 global analysis groups (funding
comes from other sources).
? SCIGN uses three analysis groups:
http://milhouse.jpl.nasa.gov/scign/analysis/
http://sopac.ucsd.edu/cgi-
bin/dbShowArraySitesMap.cgi?array=SCIGN
http://pasadena.wr.usgs.gov/scign/Analysis/
05/05/03 12.540 Lec 21 11
Other important groups
? University Navstar Consortium (UNAVCO) facility and
corporation
http://www.unavco.ucar.edu/
http://www.unavco.org
? Supports a variety of applications of GPS. Initially
tectonic deformation but now Antarctic Research and
low-precision GIS applications
? Supports US Universities in installing GPS through out
the world for geophysical studies.
05/05/03 12.540 Lec 21 12
6
05/05/03 12.540 Lec 21 13
stations)
Summary
? Data from thousands of GPS stations are
collected and processed each data
? Largest single array is in Japan (>1000
? GPS developments are like the internet
development: Many active contributors but
often quality is debatable.
7