Locating a point on a spherical surface relative to a spherical polygon of arbitrary shape |
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| Authors: | Michael Bevis and Jean-Luc Chatelain |
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| Institution: | (1) Department of Marine, Earth and Atmospheric Sciences, North Carolina State University, 27695-8208 Raleigh, North Carolina;(2) Institut Français de Recherche Scientifique pour le Développement en Coopération (ORSTOM), Nouméa, New Caledonia |
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| Abstract: | An algorithm for determining if any given point,P, on the surface of a sphere is located inside, outside, or along the border of an arbitrary spherical polygon,S, is described. The polygon is described by specifying coordinates of its vertices, and coordinates of some pointX which is known to lie withinS. The algorithm is based on the principle that an arc joiningX andP will cross the border ofS an odd number of times ifP lies outsideS, and an even number of times ifP lies withinS. The algorithm has been implemented as a set of FORTRAN subroutines, and a listing is provided. The algorithm and subroutine package can be used with spherical polygons containing holes, or with composited spherical polygons. |
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| Keywords: | Spherical polygon locate sort algorithm FORTRAN subroutine |
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