Advancements in the Develop ment of Drainage Maps from Aerial Photographs

This paper reports the progress as well as the improvement in the methods being used in the development of drainage maps of fine detail from aerial photographs of the several counties of Indiana. This drainage mapping, which is about 25 percent complete, is a part of the current highway research program at Purdue University; it is conducted by the State Highway Commission of Indiana and the Joint Highway Research Project (a cooperative endeavor financed by the State Highway Commission of Indiana and administered by Purdue University). The field of civil engineering has been broadened in scope by the introduction of airphoto interpretation. Superperformance is de­ manded of our highways, railroads, power lines, and other transporta­ tion agencies. There is a growing need for detailed drainage maps for use in the location, design, and construction of highway, airport, public-health, and flood-control projects. Airphotos can be employed in the construction of detailed drainage maps. Such maps can be used by both technically trained and untrained personnel. The airphotos used in making these drainage maps were taken in 1937-1943 in connection with the United States Department of Agri­ culture map program. The prints were obtained from the Agricultural Adjustment Administration along with the photographs of uncontrolled mosaics known as county index sheets. Approximately 25,000 prints were required for complete stereo-coverage of the state (5).*