Research On The Indices System Framework For Map Graphics Generalization And Recognition Of Graphics Structure

The map graphics generalization is an important part of the map generalization. The purpose is to improve the readability and understandability of the map, so as to meet the requirements of map-graphics accuracy and maintain topo logical relations. In order to maintain the structural features of the map graphic and type of characteristics, it is necessary to effectively identify the basic structure of the map graphics, and improve the comprehensive quality of the map graphics. Many scholars have done a lot of researches referring to the indices of map-graphics generalization, and made a series of research results. However, there are still a blank in map graphic indices framework based on basic map graphics (points, lines, triangles, curved). In this paper, indices framework is explored, and identify indices of the basic structure of the map graphic are selected rationally with the framework. More graphic knowledge is obtained through spatial reasoning for identifying the basic structure of the map graphic indices effectively. Specific research works are as follows:1) Some basic knowledge is briefly introduced, such as cartography, automated cartographic generalization, automated cartographic operators, map graphics generalization, map graphics generalization based constraints, spatial relationships and spatial reasoning. The map graphics integrated indices framework and basic structure recognition of the significance of the status quo as well as domestic and foreign research is analyzed.2) The indices system of the present study the map graphics is briefly analyzed. These indices system are not specific to the graphics unit. On the basis of defining graphical elements, the basic graphic unit indicator framework, the framework of indices of the spatial relationships between the basic graphic elements, the geometric characteristics of a single map graphics target indicator framework, the spatial relationship between the two graphical target indicator framework, the distribution characteristics of the single elements within the target group indicator framework, the inherent relationship between the target group of the multi-factor framework of indices are studied. Finally, the rationality of indicator framework is verified using building generalization indicator. It is a guidance and reference for establishment of sound map graphic indicator system.3) The bending recognition and indices of bending analysis are determined according to the framework of the indices system. On the basis of careful analyzing the defects of identifying the curve bends using the inflection point, the extreme points, line segments around the direction and diagonal cut-off point, a new methods and corresponding algorithms to identify bending are proposed with starting and ending endpoints of the curve, the extreme points, circuitous curve cut-off point, inflection point, the direction around the fixed singular points of cut-off point. And the rationality of the method is demonstrated. To identify bending with the basis of different characteristic points on the same curve, by analysis, it concludes as follows:①There are greater differences in shape, bending the number, area, arc length, baseline length and bending height based on different characteristics point bending.②Online simplify bending identifiable feature points is reasonably to determine the appropriate threshold.4) The automatically identify indices are determined for the tree river and main tributaries according to the indices framework. Spatial characteristics of different river types are simple analyzed. The non-mesh river is interrupted to form river segment at nodes. Based on180°and an acute angle assumptions, quantitative decision-making table of river flows are improved. River flow is determined according to the decision table. When the river flows conflict, the flow of the river is determined based on the principle of majority rules. River eigenvalue table is established. The river systems relationship of the main tributaries is inferred and coding according to river eigenvalue table. Finally, the algorithm proposed in this paper is verified.5) The gradual recognition indices of the urban road network in the grid is determine according to the framework of the indicator system. The spatial characteristics of different types of urban road network are briefly analyzed. Four indices are clearly defined, that's the grid index, shape similarity, overlap rate of the common side and position similarity, and the details of their formula is introduced. With part of the road network as the experimental data in Wuhan city, and the progressive methods and theories, the grid structure in the urban road network is identified according to four indices related to the grid index, similarity of shape, overlap rate of the public side and similarity of orientation. The results show better and there is no leakage of the election and the wrong election.