Research On Road Selection And Simplification Method Considering Hierarchical Structure And Spatial Conflicts

With the rapid development of China’s infrastructure construction, the number and coverage degree of roads increases sharply, making the road become one of the most rapidly changed feature, and the road automatic generalization has become the focus and hard problem of the research. The road network is perplexing and comprehensive, and the traditional road network generalization model can no longer meet the demand of highly efficient map production. So it has been urgent affairs to develop an effective road network automatic generalization algorithm. By analyzing the background and current situation of road network generalization research, this paper pointed out the main problems existing in the generalization of road network. Aiming at solving the existing problems of the selection of the road network and the simplification of the road shape, this paper proposed a road network selection method based on road hierarchical structure control, which is more in line with the hierarchical thinking of the cartographer in the selection of road. And a road simplification method based on the three-element-bending group and a simplification conflicts-avoiding strategy by using road bend was also proposed in this paper, which can well maintain the hierarchy and morphological characteristics of the road,making the automatic generalization result more in line with the map production requirements. The work and innovation is mainly reflected in the following aspects:(1)Road network selection method based on road hierarchical structure control. Under the premise of no dependence on the attribute information, firstly this paper seeks to establish a road hierarchical structure similar with the semantic level; Then deliver the importance value of the roads from top down and build an organic control evaluation system in which main road affects the branch roads and branch road affects detailed roads,under the control of the hierarchical structure; Lastly select the roads step by step according to the results of the evaluation. This method simulates the cartographer’s hierarchical thinking during the selection of road, and highlights the control of the whole road network structure and the detailed road hierarchy framework by the hierarchical structure, which makes the selection results to keep the structure characteristics of the original in the whole, and at the same time reflects the dependency relationship with hierarchical framework in detail to reduce the random selection.(2) The road shape simplification method based on the three element bending group division. In order to solve the deficiency in the hierarchy maintaining in the simplification of the continuous small bending on the current curve simplification method, a new bend based line simplification method is proposed in this paper. Aiming at the simplification problem of continuous sides curved, the method put forward the concept of three-element-bending group division, dividing the road into different three element bending groups, simplifying the bending group in different way according to the different type of bending groups, and design a circulating simplification strategy. The simplification method gives attention to both sides of the road bend, considering the mutual influence between adjacent bending, simplification results shows a clear hierarchy, and maintains the morphological characteristics of the original road.(3)The simplification conflicts-avoiding strategy by using road bending. From the angle of bending, this paper analyzed the changes of spatial relationship between the roads and other features summarized the possible conflicts during the simplification; proposed judgment rules which can quickly identify and locate the position of the conflicts; used different strategy to avoid the conflicts. This method can quickly identify and locate the position of the conflicts, avoid the simplification conflicts efficiently, and guarantee the consistency of spatial relationship between the roads and other features.(4) Detailed experiment and analysis are conducted in each chapter to test and verify the scientificalness and accuracy of the method and theory proposed in this paper. This paper also integrated the selection and simplification algorithm, designed and realized the prototype system of road network selection and road shape simplification.