Photographic description and appraisal of water resources (Commission VII, Invited Paper, Lisbon 1964)

Summary Interpretation of aerial photographs is of great value in virtually all types of hydrologic studies. These investigations range in scope from rapid reconnaissance studies based only or largely upon aerial photographs to highly detailed studies that include field work. Single and stereoscopic pairs of vertical aerial photographs, oblique aerial photographs, aerial mosaics, index aerial mosaics, and single and stereoscopic ground photographs all are of value in some phases of hydrologic studies. Infrared film is superior to panchromatic film for certain purposes. Photogrammetric techniques for measuring vertical and horizontal distances on stereoscopic pairs of vertical aerial photographs have wide application in hydrologic studies. Remote-sensing techniques involving infrared imagery and microwave systems are of value in certain hydrologic studies, but much remains to be learned regarding their full value.