Probably depends on the smartphone I guess, and satellite reception. I ask because I'm considering replacing my about to die ancient mobile with a cheap 2nd hand smartphone. The only reason I'm looking at a smartphone is because of GPS and, to a lesser extent, WiFi. GPS would be useful on some occasions but not as my primary means of navigation, nor secondary for that matter as I often carry a map if I'm on unfamiliar roads. It's only intended as a kind of 'get out of jail' card, if you get my drift. But if on-the-fly mapping sucks in practice on a smartphone then I'll not bother.