This is a question that has been bugging me for a long time, since my Nokia 5800 days. On my Nokia, the GPS function works very well, but that was when it was used as a normal phone. But when I changed to an iPhone, I wanted to keep the 5800 as a GPS device, since I thought that it can work independently from my service provider. The GPS took ages to lock, if it even locks at all. I begin to suspect that normal GSM signal also help in determining your location.
Here using my iPhone, I do a simple test. I turn off wifi and turn on airplane mode (no GSM signal from Maxis). Then I tried to locate myself using my Garmin. Here’s a screenshot:
It took me ages to get a location lock. Note the airplane icon on the top left, indicating airplane mode. Then I turned on GPS, and guess what?
It’s confirmed, turning GPS on alone is not enough for GPS to work. It also depends on either GSM signal or wifi. I tried turning on wifi (I am using a YES modem), and it also can lock my location too!
Now I know …..
EDIT : Reader Darren reported that this is the same for the iPad 3 as well. In airplane mode, GPS does not function. When airplane mode is off, GPS works, even without a SIM card. Thanks Darren for the info!