Collaborative Map Displacement Method Of Typical Feature For The Consistency Of Spatial Relations

As one of the three main theories of the cartography, map generalization has always been the key points and difficulty in the field of map cartography. With the development of GIS technology, cartographic generalization has no longer limited to the matter of information abandon and graphic expression after comprehended map scale. It’s one of the important contents in data integration, information analysis and data mining in spatial database. In addition, map generalization is also used in the implementation way of multi-scale representation. Aiming at realizing multi features generalization, earlier scholars decomposed complex task into conflict handling after single cartographic element generalization. But a large number of spatial conflict may appeared if we generalize different feature separately. With the continuous development of map generalization, the single element generalization has become increasingly prominent its drawbacks and limitations. Recently, a new generalization type named multi-feature cooperative generalization is getting more attention. Multi-feature cooperative generalization is different from the single-feature generalization. In the new type of generalization, collaborative spatial relations and evaluation mode of map features was proposed on the basis of traditional cartographic generalization. The conflicts of the map will limited in a certain range in this way.The displacement algorithm is an important part of cartographic generalization, which plays an important role in conflicts handling and consistency keeping of different features. Contour, river, road and settlement are the most common elements in the topographic map. According to the relationship, these four type of elements are divided into two group, which are contour and river, road and settlement. Collaborative movement operating depend on the construction of relationship.The main contents and achievements of this paper include as follows:1. In facing with collaborative spatial relationship of typical two-features, this paper first presents spatial relationship of each feature. On this basis, this paper mainly put forward the collaborative relationship which is used in collaborative displacement of typical two-feature.2. In facing with the contour and river collaborative movement and in the process of spatial data integration and matching, the inconsistency often occurs between the rivers and contour lines that generate some spatial conflicts just like "river climbing slope". Aiming to solve the problem by displacing the contours to matching the river network, this paper put forward a new method for every feature point on contour lines to establish its displacement model by affine transformation. The method comprehensively considered relative positions of adjacent ridge and valley points, the angle proportion of different feature points for displacing and local shape of contours to be maintained and transformed, so that the calculation of three constrained parameters determine the displacement of points on the contours that is angle, location and scaling was proposed.3. In facing with the road and settlement collaborative movement, this paper presents an optimized Douglas-Peucker (D-P) algorithm to simplify roads curve which is focus on the inconsistency between simplified roads and settlements. In order to make sure the simplified roads are not cross the nearby settlements, this paper put forward a concept named Security Area of Object Displacement (SAOD) which is extracted by Delaunay triangulation (DT) of two features. The SAOD of a road is decided by the nearby settlements. The simplification ensure simplified road in a certain range by changing the recursion condition of the D-P algorithm. That is to say, the method not only can simplify the curve, but also can maintain consistency of spatial relations.4. After simplify road data by way of SAOD, the parallel relation between road segment and the collinear or curvilinear alignments of settlements created by MST may be break. This paper put forward a way to move settlement to keep the parallel relation.To test the method, several experiments were taken to analysis. The results showed that the research of contour and river collaborative displacement can effectively complete the displacement of contour lines to match the river network. The method of road and settlement collaborative displacement can effectively avoid the conflicts between simplified roads and settlements. The parallel relation keeping method can effectively held the parallel relation between road segment and the collinear or curvilinear alignments of settlements.