ABSTRACT
The use of satellites for establishing the location of points on the surface of the earth has been one of the revolutions in surveying. It might be argued that the first revolution was the discovery of the theories of geometry and trigonometry which made it possible to calculate or deduce quantities which would be very difficult to measure directly, for example the value for the circumference of the earth determined in the third century bc by Eratosthenes (Lewis, 2001, p.144). Perhaps the second was the appearance of instruments which could measure angles with great precision (Ramsden’s telescopic theodolite of about 1785 could measure angles to a single second), and the third the development of electronic instruments which could determine distances with a similar degree of precision – first suggested as a technique in 1929, and coming into common use as a surveying tool in the 1980s (Bannister et al., 1998). Satellite location doesn’t require the surveyor to measure any angles or distances at all; co-ordinates are displayed instantly on a screen.
