Some of the most striking images of the earth’s surface have been made from aircraft in level flight using radar in a sophisticated modality. The foliage of trees is stripped away and the ridges and gullies of the hard surface are shown in stark relief. For the purpose of topographic survey the technique supersedes airborne stereophotography, which itself had earlier superseded ground survey, in mountainous and forested areas. An example of such an image is shown in Fig. 16-1.