This paper, and the paper which follows it, were first presented at the IBC '98 Conference ‘Space-Based Navigation Industry’, which was held in London, 11–12 June 1998.

In conventional arable agriculture, position within the field was usually irrelevant! However, the advent of precision agriculture, wherein inputs are targeted according to locally-determined requirements within the field, has opened up a potentially large market for GPS. Indeed, it was the availability of GPS which permitted the development and implementation of precision agriculture – a concept which holds the promise of significant economic and environmental benefits to the farmer. This paper indicates the technical requirements for GPS and presents three case studies where a positioning system is required.