The global positioning system (GPS) consists of 24 operational satellites (with several spares) orbiting the earth at an altitude of approximately 11,000 miles.

 

The satellites orbit the earth twice per day in a pattern which ensures that at least 4 satellites can be viewed from the earth at any position any time of the day. Typically however between 5 and 7 satellites may be in view.

 

The Swift Tracking GPS receiver also contains a GSM GPRS device inside (much like that found inside a mobile phone). This allows the receiver to transmit its information from the receiver back to the host server in real time via the internet.