Outside-in: An Alternative Approach to Forest Map Digitizing

This paper examines the problem of polygon digitizing, and suggests an inversion of the traditional approach for polygons of the environmental type, where each individual polygon, rather than its boundaries, is of primary interest. Many workers in geology, forestry, soil science, etc. have found the tedious specification of boundary arcs and their topological linkage and editing to be a major block to productivity. An alternative digitizing approach is described using Thiessen/Voronoi polygons to generate topology automatically and to reduce map digitizing times significantly. The digitizing of representative points within each polygon is performed using the GIS. The stand-alone Voronoi polygon building and boundary extraction module then generates linked arcs that are returned to the GIS for further analysis. Examples of the productivity enhancement in a production environment are given, along with the algorithms used. 1. The digitizing problem ‘When he killed the Mudjekeewis, of the skins he made him mittens, Made them with the fur side inside, made them with the skin side outside. He, to get the warm side inside, put the inside (skin side) outside; He, to get the cold side outside, put the outside (fur side) inside. That’s why he put the fur side inside, why he put the skin side outside; Why he turned them inside outside.’ Anon., after Longfellow, ‘The Song of Hiawatha’. In the early days of thematic mapping by computer, it was taken for granted that the primary object type being manipulated was the polygon, as it was the map object to which the attributes of interest were attached. This naturally led to the digitizing 0269-3798/96 $12.00