<p> There is more to a GPS than a pleasant voice telling you to turn right on Cedar Street, and showing a color display of adjacent ramps and intersections. This talk will focus on the technical implementation of the current GPS system, and how the user location is derived from precise clocks on satellites. You’ll see how to capture, send, and analyze NMEA data streams exchanged between your computer and GPS. Privacy issues, geocaching, and secret key codes required to manipulate GPS base maps will also be discussed. </p>