Visualisation of the terrain-sensitivity of radio communications

Planning for VHF and UHF communications has traditionally involved calculation of point-to-point radio-path losses using terrain data derived from a paper map. With the increased availability of digital terrain data, this process can be readily automated. The calculation of point-to-point losses, however, presents the user with limited information, and does not answer questions such as "if there is a transmitter located on that hill, over what area can receivers be located?" In this paper, we present a new approach based on area planning. This new approach generalises previously used point-to-point techniques, presenting a clear map overlay showing communications coverage from a user-selected transmitter location. Following the presentation of the algorithm, we present a number of cases in which misleading predictions of performance are given by point-to-point methods. Using the area-planning technique, we demonstrate how these misleading results arise.