Research On The Method Of Progressive Typification Of Buildings

Map is a visual representation of geographical knowledge and an important tool of human spatial cognition.Generalization is one of the foundations of human knowledge acquisition,which aims to reduce the level of detail of geographic data to meet specific needs.Since the 1960 s,automatic map generalization has become a hot issue in mapping and GIS industry,is one of the challenging problems of the map data processing most,the goal is to obtain a smaller scale maps from a larger scale maps by using transformation operations.The strategy of generalization varies by geographical area,and in some cities and suburbs,buildings are shown on the map in certain regular patterns.The generalization process should pay special attention to these groups of buildings with regular patterns in order to reduce the number of buildings and retain the characteristics of the original pattern,that is,the typification.There should be different typification methods for different patterns,and the typified building should be clearly represented on the target scale map.Therefore,taking buildings as the research object,this paper studies the progressive typification method of building groups with different pattern structure characteristics,and solves the spatial graphic conflict between the patterns and buildings,so as to finally achieve the purpose of typification.The research contents and innovation points are as follows:(1)A method of building group division based on the proximity of buildings and the similarity of building spatial characteristics,and identifies the patterns in the building group is proposed.When dividing the building group,three indexes of shape,size and orientation are selected to describe the spatial characteristics of the building.Road and other factors are considered when building groups are divided based on proximity.In order to extract the patterns,the results of NNG,MST,RNG and GG were compared.The better RNG was selected to extract the straight linear patterns,curved pattern and one-sided alignment pattern based on the similarity of the spatial characteristics of the buildings and the path Angle of the proximity graphs;Based on the similarity of spatial characteristics of buildings,the random pattern of building groups in the remaining buildings can be identified.Experimental results show that the proposed method can effectively identify the patterns of building groups,which is helpful for the expression and maintenance of the building group's automatic generalization geographical features.(2)Defines the constraints and conditions of typification of patterns,proposes a progressive typification method of different patterns to solve the typification problem of straight linear pattern with cross characteristics.Firstly,determines whether the pattern needs typification;secondly,symbolizes the buildings on the pattern that need typification and calculates the number of buildings on the pattern after typification;Finally,the pattern is typified by deleting buildings and shifting.For the most basic and the most complex straight linear pattern in the map,the cross straight linear pattern needs to be split,and the sub-pattern after splitting should be typified as independent pattern.Experiments show that the proposed method can reduce the number of buildings and maintain the overall structural characteristics and interrelationships of patterns effectively.(3)A method to solve the spatial graphic conflict between the typified patterns and the buildings is proposed.The spatial graphic conflicts among patterns are divided into three categories: the spatial graphic conflicts within a single pattern,the spatial graphic conflicts between proximity patterns and the spatial graphic conflicts between straight linear patterns within a group.By making the importance ordering rules of buildings and patterns,deleting the minor buildings in the minor patterns,the spatial graphic conflicts can be solved,and the buildings will be adjusted which need to be adjusted.The experimental results show that the proposed method can avoid the spatial graphic conflict between the buildings in the patterns,and finally achieve the purpose of typification of the buildings.