Getting a GPS fix from scratch (aka a cold start, where the receiver doesn't know anything in advance) takes minutes. Even if you take advantage of tricks like

Getting a GPS fix from scratch (aka a cold start, where the receiver doesn't know anything in advance) takes minutes. Even if you take advantage of tricks like out-of-band time, almanac, and ephemeris data, it can still take in the neighborhood of 10 seconds to get a fix. I imagine wifi is also less susceptible to issues that plague GPS like multipath and urban canyons