[Captain Rhino]

No, you can get something like an approximate triangulation on a cell phone’s location by analyzing the arrival time of signals at cell phone towers in the area PROVIDED there is more than one. With two, the fix is not so good. Three or more will give you an approximate location. The location is only approximate since the difference between the signal arrival times can only be measured so precisely (we’re talking of differences in the hundredth of a second or less here) and there is atmospheric distortion to signal travel times that has to be considered as well. This may seem like GPS but it is not even close to its precision. Further, while there are obviously cell phone relay towers in the area (that how the calls went back and forth), they are probably somewhat dispersed due to the terrain and there may not have been enough towers or the overlapping coverage areas needed to do the triangulation as described above.

A cellphone doesn’t have a GPS receiver (for picking up location signals from GPS satellites) unless it is specifically built into the telephone. Adding GPS usually adds significantly to the cellphone’s cost. Further, a GPS receiver doesn't emit a signal (to triangulate on), it just receives ones that are already in the air and computes its location using timing differences from the multiple satellites it “sees” overhead. GPS is superior to the cellphone triangulation method because the likelihood of getting three or more GPS satellite signals is very high due to the extensive coverage in geosynchronous orbits around the Earth and because the calculation algorithm used in determining location is fairly precise.

Pitt said their cellphones didn’t have the GPS capability. Since he was one of the two lost hikers, maybe you should believe him.

[Reeses]

GPS satellite signals is very high due to the extensive coverage in geosynchronous orbits around the Earth

GPS satellites are not in geosynchronous orbits, they are in low Earth polar orbits, and their accuracy is not as good as triangulating from cell towers can potentially be. A few years ago a special geosynchronous WAAS satellite was added that sends out a correction signal. This information is computed by land stations that know their exact location and compare it to their GPS calculated location, which is usually in error. The gravity of the Earth is not uniform and the GPS satellite positions vary constantly from their predicted positions.

Rather than just timing signals a system could be implemented to measure the phase of a radio wave when it hits. This would improve the accuracy down to a tiny fraction of an inch. Some very precise surveying equipment uses this technique.