A comparison between UHF field strength measurements and predictions using different resolution terrain databases

For over 20 years the BBC has used a computer based field strength prediction program to assist with the planning of its VHF and UHF transmitter network. It uses a terrain height database, produced in conjunction with the Joint Radio Committee (JRC), which has a resolution of 500 metres. The advent of satellite imaging techniques has resulted in the availability of much higher resolution databases. SPOT Image are offering such data in the form of a 20 metre grid; Ordnance Survey (OS) offer a 50 metre resolution grid. This then poses the question that if such terrain height data were to be used, how would field strength prediction accuracy be affected? In 1992 the European Broadcasting Union obtained a sample of such data from SPOT Image/Istar and offered it to various European broadcasters for evaluation. The author describes BBC activities in this area. The author discusses the initial evaluation of the SPOT data, measurement methods and comparison of measurements with predictions of field strength