Originally Posted by Lightingbird
Huh? Not a real compass? Do you know what I am talking about? It works with GPS to get true north to act like a real compass.
The only way GPS knows the direction of true north is when the device is moving. Once the device becomes stationary, the satellites can't tell the position of the device. It can only tell its location and, at the very most, the last direction it was pointing. If you know someone that has the iPhone and that compass application, try it. Turn on the device, remain stationary, and spin the device around. It doesn't know the direction it is pointing. Then start walking/moving. The map will then orient itself correctly.
A real compass will always point to true north even when it is stationary.
If you are going to use only the iPhone, or any GPS device for that matter, as a "compass" for navigation while backpacking/trekking then you are very foolish. Get a real compass, that is not battery-powered, for navigation. Most times, you will use the compass (when you are stationary) to get your bearings in coordination with real (hard copy) maps.
The only use of that compass application on the iPhone is for eye candy, not any real situations.