DISTORTION-FREE MAP PROJECTION FOR ANALYSIS OF SATELLITE IMAGERY
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A dynamic map map projection is formulated and tested numerically. In contrast to classical static map projections, the invariant line (projected free of length and normal-view curvature distortion) is not restricted to be an equator, a meridian, or a parallel; rather the satellite's subpoint trace (groundtrack) on the reference ellipsoid is the invariant line. Since the projection is dynamic, a local sensing time is associated with each ( phi lambda ) in the satellite sensors' field of view (assumed to be a LANDSAT-type scanner/electro-optical detector). Length and angle distortions are rigorously zero along the groundtrack projection; the largest distortion within the finite sensed strip of the earth's surface are a few parts per 10,000 for most applications. The formulation is valid for any continuous satellite orbit or orbit segment. The resulting algorithms for projection of dense sets or remotely sensed data are efficient, since the solution is analytical, except for certain orbit-dependent integrals which appear as constants evaluated for a specified nominal orbit. This map projection (the Space Oblique Mercator projection) provides a continuous normal view for the earth's surface; it has immediate significant applications for display and analysis of remotely sensed information.