A-GPS is about downloading the almanac over the fast ground data link. Solving the equations for partial signals is DIFFICULT and is where most innovation is th

A-GPS is about downloading the almanac over the fast ground data link. Solving the equations for partial signals is DIFFICULT and is where most innovation is these days. Your phone takes two seconds (and so does mine) probably because you have WiFi on and you live in the States. Try living in the middle of nowhere in, say, Serbia, and see how fast you get a lock, regardless of WiFi.