A New Algrithm of Automatically Plotting the Area Symbols in the Thematic Mapping Systems

The area symbol's automatic plotting plays an important role in the thematic mapping systems. Hatching method is often used in plotting area symbols. However, because of its simple graphic construction, when it is used to plot a complicated map, the effects of classification and contrast are not very optimal. So, the authors put forward a new method——the pattern-hatching method in this paper. This new method is based on the hatching method, using different kinds of hatching lines, break hatching lines to form many new patterns and realize the automatic output of the area symbols. The design of this pattern-hatching method is very simple and practical. Not only could it be in interactive output, but also could automatically form different kinds of patterns. On the one hand, it has the advantages of the hatching method, on the other hand, it also has the advantages of itselfautomatically forming the various area symbols. With the pattern-hatching method, the authors plotted successffully the thematic maps of the LPMCGIS-the Lesso Plateau Microcomputer Geographical Information System, and gain a very optimal effect.