Accession Number : AD0723998

Title :   Automatic Relief Shading,

Corporate Author : NATIONAL RESEARCH COUNCIL OF CANADA OTTAWA (ONTARIO) PHOTOGRAMMETRIC RESEARCH SECTION

Personal Author(s) : Marsik,Z.

Report Date : 13 FEB 1970

Pagination or Media Count : 14

Abstract : The theoretical law of shading is expressed by the formula D=log (1/cos i), where D is the density of shade of a terrain element and i is the angle of incidence of the illumination on that element. The general theory of automatic shading is based on the consideration that within the vicinity of any terrain point, the terrain surface may be replaced with a geometrical surface and the angle i is then the angle between the incident ray of light and the normal to the geometrical surface. However, as proven both by theoretical analysis and by experiments, an adequately modified law of shading not only makes possible a simple instrument design for automatic shading, but also results in a three-dimensional impression which does not differ much from the one obtained when the theoretical law is applied. The NRC(National Research Council) shading device, working with the modified law of shading, coupled with an orthophoto plotter, is described. (Author)

Descriptors :   (*MAPPING, *PHOTOGRAPHIC CONTRAST), MAPPING, AUTOMATION, PHOTOGRAPHIC PROCESSING EQUIPMENT, CANADA

Subject Categories : Cartography and Aerial Photography
      Photography

Distribution Statement : APPROVED FOR PUBLIC RELEASE