Originally Posted by
philbob57
There's some fuzziness in civilian GPS positioning, +/- 50 meters, IIRC. Both are likely to be off.
Not exactly. That is the guaranteed worst case accuracy. Actual is closer to about a meter in broadcast signal. Typical smartphone accurate is about 4-5m.
See:
GPS.gov: GPS Accuracy
Lots of good information there about GPS accuracy.
Originally Posted by
Steve B.
As far as I know, the devices get little accurate info from cell location, just general location, nothing as accurate as GPS.
Correct.
Phones use the cell tower to get an approximate position fix so that GPS positing fix is determined much faster. If you don't know where you are on the planet and the GPS has to figure that out on it's own, it takes a while. Older GPS units used to take a minute or more to get a fix. If you gave it position data that got it close, it was much faster. With cell tower triangulation, the phone has a pretty good idea where it is all the time and the GPS can rapidly get it's position accurately. Once the GPS is on and locked in position, it's going to be more accurate and there would be no need for cell tower triangulation.
J.