How to check GPS signal whether is available on iPhone?

as topic...

I try to use the didError method , but it开发者_StackOverflow does not works ... if I am in room , the iPhone sdk seem insist try to got the location as it could in my app, even the value is not accurate ...

how to deal with such problem ?

thanks for your help in advance .

Regards

I've found that when I get a location from the core location service, if the verticalAccuracy was less than 0, that means the GPS isn't being used to get the position. It seems that you can't get an altitude from the Wifi/Cell methods of determining a location.