FUZZY REPRESENTATION OF GEOGRAPHICAL BOUNDARIES IN GIS

Polygon boundaries on thematic maps are conventionally considered to b e sharp lines representing abrupt changes of phenomena. However, in re ality changes of environmental phenomena may also be partial or gradua l. Indiscriminate use of sharp lines to represent different types of c hange creates a problem of boundary inaccuracy. Specifically, in the c ontext of vector-based GIS, use of sharp lines to represent gradual or partial changes may cause misunderstanding of geographical informatio n and reduce analysis accuracy. In this paper, the expressive inadequa cy of the conventional vector boundary representation is examined. A m ore informative technique-the fuzzy representation of geographical bou ndaries-is proposed, in which boundaries describe not only the locatio n but also the rate of change of environmental phenomena. Four methods of determining fuzzy boundary membership grades from different kinds of geographical data are described. An example of applying the fuzzy b oundary technique to data analysis is presented and the advantages of the technique are discussed.