| 摘要 |
Signal transformations of inputted data brought about by 58 new subroutines in combination with other subroutines to display world maps or other display items with the unique capability of performing the following functions in complete generality. (1) Arbitrary selection of map center and coverage, including global displays, (2) filling of all land and lake areas defined by polygons composed of an arbitrary number of vertices, (3) clipping of map features and overlays at map boundaries and poles, (4) selection from any of nineteen currently implemented map projections with provision to install any other projection topologically similar to an oblique conic, (5) calculation of latitude/longitude for any point on a map without the need for inverse mapping equations, and (6) an efficient method of plotting polyline segments along great circles. These are a number of feature functions provided by this inventive concept. The software could potentially be used with any digital global geographic data base, such as World Data Bank II (WDBII), a geographic information system or other data base where polylines are used to depict linear and/or areal features. Polygon (region filled) maps and other display items can be constructed from any data base from which closed polygons can be extracted directly, or constructed via additional processing.
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