Experiments with Lights, Shadows, and Contours, and the Resulting Shadowgraphic Contour Maps

Abstract

This paper describes some experiments with the photography of sidelighted folded surfaces made for the purpose of developing a technique that would enable the direct application of lights and shadows to structural contour maps and thereby facilitate their interpretation. For many years the mapping agencies of various governments throughout the world have exerted much effort toward the development of a type of topographic map that would give a better expression of relief than the conventional contour map. Noteworthy progress in this direction has been made by the United States Geological Survey and the Engineering Corps of the United States Army. Both branches appear to agree that the desired ends may be obtained through the application of lights and shadows, but their tec niques differ. The writer of this paper suggests that lights and shadows could be used to good advantage as supplemental aids to the contours of structural maps. The name is proposed and defined to describe this new type of structural map. Certain fundamental rules which now appear desirable in connection with the construction and interpretation of these maps are stated. The application of lights and shadows to structural contour maps adds the element of unity to the contour framework and furnishes a method by which data on faults and fault patterns may be recorded with proper emphasis. Five examples of published maps, first in their original published form and then after shadowgraphic treatment, conclude the paper.