TOPOLOGICAL CONSISTENCY OF COMPLICATED OBJECT ON MAP DATA
H. Huang, H. Liu
Department of Cartography, Institute of Surveying and Mapping
The spatial topological relationship is the most important in graphics spatial relationship. Currently, the digital mapping systems exists some deficiencies to solve the problem which is to process the data include topological information. If we edit (add/delete) one line, we need establishment the tropical relationships of whole spatial data again. The paper put forward a specific method to retain the data spatial relationships, which is on the basis of complicated object on map. The method could not only maintain topological consistency, but also promote the efficiency of data processing and maintain symbolization consistency. The main subjects of this paper are as follows:
1．Introduce the methods, which solve the problem in the current digital mapping systems, analyze the deficiency and difficulty for these methods. There are two disadvantages: First, when you edit the lines have public points, you must edit each line, and then establish the spatial topological relationship again; Second, when you edit one polygon, you could not maintain the symbolization consistency.
2．Define the complicated object structure on map data. The main subjects are as follows: using the topological data module, establish the spatial topological relationship among the point, line, and area features accord to the geometry characters of map features; put all information about nodes and arcs in database, and add the point array about the areas in database to maintain symbolization consistency.
3．Method of maintaining topological consistency according to complicated objects on map. The complicated objects have two kinds: the first kind complicated objects make up of two or more lines with public nodes. We can use the nodes information to process; the second kind complicated objects make up of two or more areas with public lines, which might have public nodes, so we should calculate from node to line and then to area, and update all features at the same time.
4．Conclusion. We test and analyze the algorithm with the 1:250000 relief map data. As a result, it could not only maintain topological consistency, but also promote the efficiency of data processing and maintain symbolization consistency.