| Popis: |
SPANS (SPatial ANalysis System) is a quadtree/raster GIS developed by Tydac Technologies Inc. of Canada. Two versions of SPANS are available at present (February 1991). Version 4 runs under MS-DOS and has as a minimum hardware requirement a 286 AT compatible with dual mono and color (EGA) graphics cards and monitors. However, to realize fully the potential of SPANS 4 a 386 machine is desirable, together with an extended memory manager. SPANS version 5 (which has additional functionality) runs under OS/2 on a 386 machine with a minimum of 8 Mbyte of memory. SPANS is a menu-driven system. In version 4 menus and help are displayed on the mono screen, with graphical output appearing on the color screen. In version 5 a hierarchy of menus is provided by windows, so that only a single (color) graphics card and monitor are needed. An interesting feature of SPANS, possibly unique amongst commercial GIS at the time SPANS was introduced, is that it uses quadtrees as the medium for storing all map data. The aim of this paper is to explore the extent to which the use of a quadtree data structure influences the functionality of the system; it should not be taken to be a complete account. SPANS terminology is indicated in bold type, and explained where necessary. |
