Photogeologic procedures in geologic interpretation and mapping

In the past few years increasing use has been made of aerial photographs for geologic interpretation and mapping within the U.S. Geological Survey. As a specialized technique in interpretation and mapping, however, photogeologic procedures were extensively used (1947-1953) in the Survey's geologic mapping of Naval Petroleum Reserve No. 4 in northern Alaska and in mapping part of the Colorado Plateau of western United States, principally in Utah (1951-present). Photogeologic work was performed by a specialized group of geologists that was organized as the Photogeology Section in June 1953. This group has more recently made studies of northeastern Utah, southern and southeastern Alaska, and central Alaska. Various photogeologic procedures have been used in these studies; some procedures have been modified, and new ones have been developed. It is primarily the purpose of this paper to discuss these procedures. Photogeologic procedures or techniques used outside the Geological Survey are not discussed herein.