How does a browser get GPS data from a computer?

Question

HTML5 browser can retrive the gps position of a computer. http://diveintohtml5.ep.io/geolocation.html

I would like to create an application that fakes a GPS device,

Answer 1

Chrome and Firefox:

• GPS via gpsd if available (Linux only) 1, 2
• system's Location API (Windows 7 only) 2
• WiFi networks via Google Location Services 1