Abstract : This handbook contains measured line-of-sight (LOS) data for 12 types of terrain and vegetation combinations. The terrain/vegetation types are identified or classified with word descriptions, topographic maps, and aerial and ground photographs. The user can compare these standarized types with the terrain in which he is interested, and select one that matches as closely as possible. The LOS data are provided in the form of graphs that show the probability of a clear LOS as a function of range and altitude, and also the critical altitude (the altitude necessary for a clear LOS) as a function of range.