Study On Cartographic Generalization Of Land-Use Status Based On Multi-level Control

Land-use data is the data that reflects the geographical location,quantity,spatial distribution structure and utilization of land,and is the scientific basis for the relevant departments to manage land and resources and formulate various development plans,but different departments usually need different scale of land-use map,so it must involve land-use data cartographic synthesis.At present,there is a lot of research on cartographic generalization of land use data,and there are also quite rich research results.However,the existing cartographic generalization focuses on the generalization of single factor,that is,the generalization of factor-oriented cartography.The research focuses on the selection and improvement of the algorithm for the operation of a certain factor.From the perspective of map oriented,this paper takes the cartographic generalization process of land use data as the research object,and establishes a multi-level control system,which controls the layout of map element structure,the position accuracy of map content and the topological relationship of elements before and after cartographic generalization with the control of attribute,graphic and topological relationship.Attribute control is divided into two levels.The first level control is level control,which is to ensure the correctness of the subject content of the comprehensive results and meet the needs and standards of the industry.The second level control is the importance control of land type,which is needed in the process of graphic synthesis.The second level control is the importance control of land class,which is needed in the process of graphic synthesis.The control is to ensure the integrity of map expression content and maintain the consistency of regional geographic features before and after synthesis.The graphic control is realized by means of control points,which are divided into two levels.The first level controls the whole map uniformly to ensure the position accuracy of the integrated graphic;the second level controls the single element to ensure the basic shape of the graphic is consistent before and after the integration.Topological relation control is to ensure the correctness of topological features of map elements before and after synthesis and the consistency of topological relations among multi elements.It uses the way of topological points to realize control.This paper takes the land use data of 1?10000 in Xianfeng County as the research object,synthesizes it to 1?50000,and comprehensively evaluates the comprehensive quality from the map content graphic precision,attribute precision and topological precision after synthesis.The following conclusions are drawn from the research: 1.The control effect of graphic control on the location and basic form of map spot is significant,which can effectively control the cumulative propagation of errors,make the overall position of elements on the newly compiled map change slightly,and the whole map has a high position accuracy;2.The attribute control ensures the correctness of the content of map expression,and has a good effect on maintaining the similar structure of land and stable layout The results meet the requirements;3.The topological relationship control can ensure the correctness of the internal topological relationship of a single layer,and maintain the consistency between multiple elements before and after the integration.