[bigiain]

You don't need to know "when it starts", it transmits in a loop, you need to collect ~12.5 minutes of that loop to get the entire almanac. (lousy software _might_ not understand unless it finds some particular preset mark in the loop, but it's not a GPS system architecture problem)

[morganw]

The user needs to know when the almanac is being received and when the whole thing is in when looking for a clear-view-of-sky spot to sit a while.

The best you can do with CoreLocation is set desiredAccuracy to kCLLocationAccuracyBest and wait for it to fall below 100 feet with no way to find out if it ever will.