Why are the satellites which transmit the GPS signals not geostationary?

Answer 1

To get a good GPS fix you need to receive signals from several satellites at large angular separations from each other, along the dimension that you're trying to get a fix for. If all the GPS satellites were in geosynchronous orbits (and therefore in the plane of the equator) there would never be much separation in the north-south direction, so you couldn't get a good latitude fix. Even the longitude fix would be poor (compared to the present configuration), since the satellites would not have quite as much east-west separation (as seen from the US, for example). This separation problem exists even in the current system when you try to determine altitude with GPS. Since all the visible satellites are "up" and none are "down," the altitude determination is a lot less accurate than the determination of latitude or longitude.

Answer 2

As others have said, the geostationary orbits are very special and coveted and there is only enough room for so many satellites, so those that don't really need to be there should be put there.
The GPS system does not need for the satellites to be in any one place. The GPS satellites talk to the GPS receiver on multiple channels. The information transmitted is much more than the stand alone "tick" of the atomic clock. The GPS satellite is telling the receiver exactly where it is in the sky as well as other information. The GPS satellite knows where it is because every day a highly accurate radar is beamed to it from the Naval Observatory to measure its position, and then the GPS satellite's database is updated.
There used to be a very good explanation on how the GPS system works at the Trimble Website.

Answer 3

Very simple - There's no need to be geostationary.

The satellite orbits are distributed so that at least 4 satellites are always visible from any point on the Earth at any given instant (with up to 12 visible at one time).

There are a few geostationary GPS Satellites used for checking the accuracy of system (Look up WAAS in realtion to GPS)

Also remember that Geostationary orbit is one of the most sought after areas of orbital real estate, and it's probably best not to clutter this up with the 24 GPS satellites.

Answer 4

They don't need to be. Since geostationary orbital positions are very coveted they and are relegated to weather and communications satellites there was no reason to waste them on the GPS system.

Answer 5

TV/defense satellites have already taken up the geo spots, being the distance from earth determines the orbital path

Answer 6

because of the gravotatial pull on them there size makes them move faster than the earths rotation