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Currently we have GPS, GLONASS and Galileo to choose from and by 2020 ish China will have expanded BeiDou to be global, then as has been mentioned there is the wi-fi/celltower geolocation stuff if close is good enough or are they proposing some apocalypse proof system? in which case id suggest the stop and ask someone method, you will be furnished with a list of turnings and pubs you will go past to get to where you want to be.