Originally Posted by SVAuspicious
.....The phone or tablet "knows" the location of the cell tower it is connected to as part of network interaction (thus no data) and uses that as a seed to speed up the GPS position determination. It still works offshore, well out of cell phone range. It just takes longer to get a position solution.
To be clear, this is only for the initial fix, as the device would know which satellites it should be looking for. Otherwise, it just takes a few more seconds to figure it out. Thereafter, it works just as fast, with or without.