The documentation for a computer system called MAPS (Map Assembly and Processing System) is presented. MAPS is a package of 18 programs that can be used for input, processing and display of land classification maps and associated numerical information. The programs are written in BASIC for execution on a Wang 2200 minicomputer with 8K of core memory. In addition to the Wang 2200 C.P.U., a graphics terminal, a digitizer, two cassette units and a printer are used by the system. Currently, hard copies of output maps are obtained on a CALCOMP plotter driven by magnetic tapes produced on an IBM 360-370 to which the Wang 2200 communicates via telephone line. The present system has limited capacity for the automatic handling of overlays obtained by superimposing separate source maps. A conceptual design for a system with full overlaying capability is presented in an appendix.
MAPS uses the polygon method to obtain a computer representation of a map. With this method, the map is considered as a partition of the plane into regions delimited by boundaries that are approximated by polygonal lines. The sequences of vertices of these polygonals represent the map in the computer. Arcs -- pieces of boundary that separate two regions -- are the basic units or building blocks for the system. The system can produce maps consisting of any subset of the arcs of the original map. Specifications for map preparation may be conditions on numerical data associated with the regions of the base map. In general, processing of a source map will involve a map data file and a numerical data file.
The functions of MAPS include the following: entry and editing of maps; computation of areas; entry, editing and processing of numerical data; sorting of numerical data; selection and display of regions satisfying some specified logical condition concerning the associated numerical data; generation of maps obtained by grouping regions of the source map in classes defined by the associated numerical data; superposition of maps; general geometrical transformations of maps.
The appendix on overlays describes algorithms for adjusting for closure errors in the region boundaries, finding intersections between arcs, and recognizing regions formed by intersection.