Usefull links: http://www.colorado.edu/geography/gcraft/notes/gps/gps.html#SpaceSeg click on http://www.colorado.edu/geography/gcraft/notes/gps/gif/orbits.gif to see a "view from the Moon" This is all well and good, but the planned orbit is not complete, some birds up are dead, and so there are lots of coverage drop outs.
http://igscb.jpl.nasa.gov/overview/links.html#GenLinks http://www.navcen.uscg.gov/misc/about.htm http://www.aero.org/publications/GPSPRIMER/index.html http://www.nstb.tc.faa.gov/vpl.html
