evo , da ne bi bilo da sam nešto izmislio :
The Global Positioning System (GPS) is a technical marvel made possible by a group of satellites in earth orbit that transmit precise signals, allowing GPS receivers to calculate and display accurate location, speed, and time information to the user.
Once 3~5 Satellites are being captured users will receive the position accurate within 5~10 meters.
GPS Accuracy is affected by a number of factors, including satellite positions, noise in the radio signal, atmospheric conditions, and natural barriers to the signal. Noise can create an error between 1 to 10 meters and results from static or interference from something near the receiver or something on the same frequency.
Once capture 3 Satellites or more the receiver accuracy will be within about 3 to 15 meters (3D).
A Fake GPS:
Any Device say it is a GPS Navigator but without direct connection with the GPS Satellites Signal is only a Fake GPS.
Fake GPS is a general term describing the use of signals from cell phone towers or Wi-Fi hotspots to triangulate and display the position of a user of a mobile electronic device.
Fake GPS users will only receive a limited position accurate over 100~1000 meters (2D only).
Testing the iPhone's fake GPS:
Which is great if you just want to know where you are (which is what it was designed for, obviously). But not so great if you're actually trying to do something you'd need GPS for (like geocaching).
Links to find free GPS map:
http://www.maps-gps-info.com/fgpfw.html