I live in a city of urban canyons, so finding GPS satellites can be dicey, and it's definitely better in some neighborhoods than others. In general, I've found that my phone (currently an HTC One M8) finds a GPS signal more quickly and reliably than my Garmin Edge 500, which some days takes forever. I don't think there's ever been a time, even in the city, when the phone or the Garmin was completely unable to find a GPS signal, though it can take a long time.

The thing is, there doesn't seem to be any rhyme or reason as to when the Garmin works, or when it has trouble. Starting from the same spot, say in front of my apartment, some days it will find satellites almost immediately, other it will take minutes, and the status bar creeps up, and jumps back, repeatedly. Some days the track it draws is more accurate than other days, when I apparently careen wildly through buildings. Is it possible that satellites move around, so the Gamin can find them some days, but not others? Oddly, I've found the Garmin to be more accurate and less cranky lately, compare to when I first got it. Is it possible there are more satellites over the city now?