Aerial photography has two uses that are of interest within the context of this course: (1) Cartographers and planners take detailed measurements from aerial photos in the preparation of maps. (2) Trained interpreters utilize arial photos to determine land-use and environmental conditions, among other things.
Although both maps and aerial photos present a “bird’s-eye” view of the earth, aerial photographs are NOT maps. Maps are orthogonal representations of the earth’s surface, meaning that they are directionally and geometrically accurate (at least within the limitations imposed by projecting a 3-dimensional object onto 2 dimensions). Aerial photos, on the other hand, display a high degree of radial distortion. That is, the topography is distorted, and until corrections are made for the distortion, measurements made from a photograph are not accurate. Nevertheless, aerial photographs are a powerful tool for studying the earth’s environment.
Because most GISs can correct for radial distortion, aerial photographs are an excellent data source for many types of projects, especially those that require spatial data from the same location at periodic intervals over a length of time. Typical applications include land-use surveys and habitat analysis.
This unit discusses benefits of aerial photography, applications, the different types of photography, and the integration of aerial photographs into GISs.