How accurate is the reading for GPS in iPhone's SDK?

Using iPhone's SDK GPS API, how accurate can I get? Is it within a few meters or kilometers? I'm interested 开发者_Go百科in the accuracy when it is indoor. My software will only be used in door.

The best possible accuracy seems to be 9 meters. Common values (outdoor, good coverage) is 17 m, 23 m and 49 meters. With trees covering the sky you'll probably stay under a hundred meters, but hardly accurate enough for GIS or anything like that.

The API has a property or method that returns the current accuracy of the location measurement. If your goal is only to use the location if accuracy is within some limit then you should make sure that you check the returned accuracy, since the location may be only accurate to within a few thousand meters initially as its just using your location from the cell towers, and it will typically get better and better accuracy as the GPS powers up and starts getting a fix.

Most standard GPS chips (and the iphone is that) can get around 10 meters accuracy. Best results are outside on a clear sky obviously.

The difference between GPS chips is usually how quickly they can reception and how well they can hold it. Accuracy is pretty constant except for those using WAAS sattelite (which the iphone GPS doesn't do)

Based on my own experience it's within meters.