The effect of direction of illumination upon the visibility of a smoke column

Abstract

Preliminary investigations in the detection of forest fires at the California Forest and Range Experiment Station were based on the assumption that the visibility of smoke columns in the field would vary as the visibility of the landscape with varying conditions of atmospheric suspensoid concentration and with the position of the sun. This led to the determination of the effect of direction of the sun with respect to the observer's line of sight upon the visibility of natural features in the landscape through analysis of a large number of lookout observations of natural targets on the Shasta National Forest. Later observations of test-fire smokes, however, indicated clearly that the visibility of smoke columns as reflected in fire-discovery time docs not vary in the same manner as landscape visibility. The following laboratory experiment was devised, therefore, to determine in just what manner the visibility of a smoke column varies with different positions of the sun with respect to the observer's line of sight.

Citation

Buck, Charles C.; Fons, Wallace L. 1935. The effect of direction of illumination upon the visibility of a smoke column. Journal of Agricultural Research 51(10): 907-918.