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《Acta Geodaetica et Cartographica Sinica》 2007-01
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Map Objects Displacement under Constraints

MAO Jian-hua1,2,LI Xian-hua1(1.School of Communication and Information Engineering,Research Centre of Remote Sensing and Spatial Information Science,Shanghai University,Shanghai 200072,China;2.Key Lab of Poyang Lake Ecological Environment and Resources Research of Ministry of Education,Jiangxi Normal University,Nanchang 330022,China)  
Map objects displacement is an important operator in the map generalization and visualization of spatial information,and the key of displacement operator is how to satisfy constraints necessary for the maintenance of spatial relationship between map objects.In this paper a method of map object displacement under constraints,based on the finite element method and spatial reasoning,is examined.At first,some basic concepts of finite element method are introduced, and three common constraints of position,characteristics and legible in the map objects displacement are discussed,and then the strategies of classification and weighting rules for the map objects are examined,and then a method for the constraints satisfaction based on the finite element method and spatial reasoning is presented,which is followed by the discussion of a progressive node displacement algorithm,and at last,a case study of road widening with this method is presented.And the result shows that the road is parallel strictly and spatial topological relationship between roads and districts are maintained after the widening process,but spatial confliction still happened to district objects in the dense objects areas.And at the same time,the method shows some characteristics including that the forces produced by the road node displacement and push on the partition boundaries of other objects can be assembled and evaluated simultaneously,and through the spatial reasoning process,the force propagation in the displacement process can be controlled by setting boundary conditions and then map objects displacement outer this boundary are avoided.
【Fund】: 国家自然科学基金项目(4040105060672053)
【CateGory Index】: P283.7
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