THE CENTRAL PROJECTION OF THE SPHEROID AND SURFACE LINES

Author: Bowring B. R.  

Publisher: Maney Publishing

ISSN: 1752-2706

Source: Survey Review, Vol.34, Iss.265, 1997-07, pp. : 163-173

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Abstract

The gnomonic (central) projection for a sphere is well known ([2] page 596). It has the characteristic that great circles project into straight lines, so that the shortest distance on the sphere projects into the shortest distance on the projection plane between the projections of the ends. Given a map obtained from the central projection, a pilot might plan a great circle route by drawing a straight line on it from starting point to destination. The positions of towns and geographical features on the map may then become apparent with regard to the line. The present paper studies the central projection for the spheroid, for which the corresponding characteristic is that great elliptic lines project into straight lines. Comparison may be made with [3] which shows the geodesic on various projections (e.g. UM and Lambert) as curved lines.