Global Positioning System

Global Positioning Systems (GPS) can define geographical location and altitude to varying degrees of accuracy. GPS can be very useful for providing locational information where map coverage is limited.

They do this by using triangulation geometry based on signals received from the NAVSTAR GPS satellites. Hand held ground receivers need to get a fix on at least 3 satellites. The results are displayed on the receiver and can be downloaded to a computer.

Some problems exist in terms of accuracy but the use of local base stations on well located objects means that differential GPS measurements can be accurate within 1m.