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Generalization of cadastral map based on graphics matching
Xiaoyong CHEN, Jie DU, Takashi Doihara* Asian Institute of Technology, P.O. Box 4 Klong Luang, Pathumthani 12120, Thialand Email: xychen@ait.ac.th *Asia Air Survey Co., Ltd., 8-10, Tamura-Cho, Atsugi-Shi, Kanagawa 243, Japan
Abstract:
Old cadastral map records the geographic shapes of land partials and their related thematic information. It is generally drawn on an A3/A4 size paper and only presents the cadastral information of small city blocks. During the recent years, Japan government plans to make a kind of new cadastral map that is a typical formal map with the scale 1:2,500. So the editing works are needed to convert or transfer the old cadastral map to new one. The objective of this paper is to present the algorithms for automated generalization of old cadastral map based on graphics matching. Some practical examples are also given to show the efficiency of our algorithms. Introduction Old cadastral map records the geographic shapes of land partials and their related thematic information (such as land ID number, owner name, and prices). It is generally drawn on an A3/A4 size paper and only presents the cadastral information of small city blocks. During the recent years, Japan government plans to make a kind of new cadastral map that is a typical formal map with the scale 1:2,500. So the editing works are needed to convert or transfer the old cadastral map to new one. The purpose of this research is to develop the algorithms and a system for automated editing old cadastral map, which mainly contains feature point detection, feature point matching, conflicted line detection, automated conflicted line generalization.  Figure 1. An example of an old cadastral map As shown in Figure 1, there are four kinds of map data for our research. These data are cadastral line map, road line map, building line map and boundary line map. Cadastral line map is or target map, it will be overlapped on base maps and adjusted by existing base lines, such as road lines, building lines and boundary lines. There are two kinds of problems in our research. One is automated matching old local cadastral map with road base line map. Another one is automated detection of conflicted lines (such as cadastral lines with boundary lines, cadastral lines with building line, and cadastral lines with local small road lines) and make related automated adjustment. Methodology Cadastral Map Pre-matching The method of cadastral map pre-matching with road maps is based on Affine transformation by using four given points on each map. Why we select Affine transformation as our cadastral map pre-matching method is that two maps are not exactly similar and sometimes we need matching with several city blocks together. So free matching will be very difficult and reliability will be very low. Giving two points on each map is only for scaling and rotation transforms. So that giving four points on each map is the minimum numbers for reasonable complicated transformation. Cadastral Map Sequential Auto-matching After above pre-matching, two map layers may still have small differences. We designed an algorithm called sequential auto matching based on sequential Affine transforms.  Figure 2. An example of a cadastral map sequential auto-matching
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