Topographic exposure is a variable which represents the degree of shelterafforded to a location. A detailed knowledge of exposure is useful for awide variety of applications, ranging from the dynamics of drifting snow tothe optimal location of wind-farms. The degree of exposure can be calculatedby considering the relative heights and distances of the horizon surroundingthe point of study. Numerous approaches have been developed to measure thisuseful variable, from the early qualitative studies of wind-shaped trees toPyatts's quantitative TOPEX assessment. However, these studies have beensuperseded by the use of computers and in particular the application ofdigital terrain models. These provide a fast office-based solution,virtually eliminating the need for fieldwork.