Aerial Color Analyses of Water Quality

A new technique utilizing color photography in aerial water analysis is described. The technique termed the scene color standard (SCS) technique, uses natural objects in the photographic image to remove peripheral effects in the water quality measurement. The color of a body of water is shown to depend upon: (1) source effects, (2) atmospheric effects, (3) surface reflection effects, and (4) volume effects. These phenomena are reviewed, and volume spectral reflectance is shown to be the only definition of water color sensitive to water quality. All other color effects are peripheral effects, and can be described by three parameters: α; α' and β. Crucial to the SCS technique is use of shadow information; information traditionally of limited value to the photointerpreter. The technique is applied to measurement of chlorophyll content in Lake Chautauqua in New York State. Reflectances of ground objects are shown to be in excellent agreement with the aerial data.