Global Positioning System (GPS)

 ## Benefits include:

• Access to satellite signals is available over most of surface of earth unlike signals from terrestrial transmitters

• Transmission of GPS signals is not dependent on political boundaries

• Satellite signals are accessible over oceans where terrestrial transmissions are difficult to receive due to the long distances from land

• Signals are available to anyone who wishes to use them (unless switched off by operator of satellite)

• Satellites are vandal-proof/ inaccessible to those who would physically attempt to disrupt their function

## Drawbacks include:

• Requires a large number (c.25 to 35) of satellites to be in orbit to provide adequate coverage of terrain

• Cannot easily be repaired if malfunctioning

• Requires at least 3, preferably 4, satellites to be visible to / received by GPS

receiver to achieve reliable/accurate positioning

• Satellite signals are blocked by solid objects/buildings/in tunnels/trees/dense

clouds/ snow storms so, in these circumstances, GPS receivers may«

• «fail to provide locations

• «may provide erroneous locations.