I just use foursquare first time, looks it find my location and shows on the map very correct. I am using desktop at home, just curious, how does it know my address? Thanks.
It uses HTML5's Geolocation API to determine a user's location
It uses the GPS from your phone and updates your position on that.
For an exact businesses you are at, you "Check-In" to a business through the app.
来源：https://stackoverflow.com/questions/9899694/how-foursquare-determine-a-user-location