A warm start is actually typically faster than 30 seconds, averaging closer to 20 seconds. Additionally, almost all fixes using smart phones are hot starts. This is because smartphones use assisted GPS, they download almanac and ephemeris data not from the GPS network itself (where they are broadcast every 12.5 minutes and 30 seconds, respectively) but over a data network, in seconds. Similarly, smartphones have a pretty good idea of where they are already, because they keep track of their positions historically and they use cell tower triangulation as a secondary location system. From a hot start a GPS receiver could get a fix in only a handful of seconds, potentially.