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