Accession Number : AD0762824

Title :   Solar-Altitude Nomogram,

Corporate Author : MCGILL UNIV MONTREAL (QUEBEC) DEPT OF GEOGRAPHY

Personal Author(s) : Parry,J. T. ; Gold,C. M.

Report Date : 1972

Pagination or Media Count : 9

Abstract : Parallax procedures are most frequently employed in making height measurements on air photos. However, there are situations where parallax procedures cannot be applied and the only alternative is the shadow-length method which requires the calculation of the solar altitude. The procedures currently used to obtain this value are tedious and time-consuming, and for this reason graphical solutions are preferable. By careful scaling of the axes, the shadow-height nomogram described in this article incorporates all the variables within a single, conveniently sized diagram, thus permitting a solution for the solar altitude using either the date and time of photography, or the date and azimuth of the object shadow. The nomogram provides a means of obtaining the solar altitude rapidly with a minimum of calculation and within an error margin of plus or minus of a degree. With a little practice the solution for the solar altitude can be obtained in approximately two minutes for any given set of conditions, thus providing a considerable economy of time and effort if compared with conventional methods. (Author)

Descriptors :   (*AERIAL PHOTOGRAPHS, PHOTOINTERPRETATION), (*PHOTOGRAPHIC IMAGES, HEIGHT FINDING), PHOTOGRAMMETRY, NOMOGRAPHS, CANADA, MAPPING

Subject Categories : Cartography and Aerial Photography

Distribution Statement : APPROVED FOR PUBLIC RELEASE