Research On The Method Of Selecting Elements For River Chief Map Service

With the comprehensive deepening of the work of the river chief system,the special map of the river chief system is an indispensable step to describe the visualization information of a river chief system in a region.According to the needs of the river chief system map service,the elements in the watershed thematic map are selected as the connotation and extension of the map synthesis,which becomes the core link of the river chief system map design and production.Facing the new map comprehensive demand,the river basin map synthesis research of river chief system has ushered in new challenges.In the traditional thematic map preparation process,most of the computers use the selection model and algorithm to select the strategy,but how to make the computer program select according to the specific demand environment of the river chief system is a new research content,and become the main obstacles to the selection element for the river chief system map service.This mainly involves two aspects: one is to objectively recognize the geographical characteristics of the river chief system;the other is to implement the comprehensive selection behavior based on the geographical environment characteristics of the river chief system.Combining the above problems,the paper takes the selection of elements in map synthesis as an example.Through the discussion of the background significance of the research on the selection method of the elements of the river system and the basic theory of the comprehensive selection of geographic elements,the research on the method of selecting the elements for the river chief system map service is carried out.The main research is as follows:1.Analyzed the geographical features of the river chief system map service.According to the original meaning of the river chief system policy and the necessity of the river chief system geographic information platform,combined with the specific demand environment expressed by the special map of the river chief system and the basic characteristics of the map comprehensive project to summarize the concept of factor selection in demand environment of the river chief system.Base on this foundation constructs the selection characteristics and selection requirements of different factor levels.2.Discuss the research on the selection methods of factors that take into account the specific needs environment of the river chief system.At the conceptual level,the selection method of each element is proposed,and the experimental analysis is carried out by the selection model of each element on the logical level.(1)proposed and implemented a residential point selection method that takes into account the characteristics of the river chief system.Considering the difference of geographic information value in the spatial distribution of point groups,a structural selection model considering semantic constraints,position importance,area distribution,spatial conflict and river related elements is proposed.At the same time,this paper combined with the target group target for experimental analysis and discussion.(2)A river selection method that takes into account the structural grading of rivers is realized.Considering the spatial hierarchy of rivers and the importance of individual targets,the selection model based on river classification optimization is realized,which solves the application of existing structured selection methods in the river chief system map service.(3)A method for selecting planar features that maintains the characteristics of the subject is implemented.The lakes and reservoirs in the river basin are comprehensively expressed by thematic elements.Through the use of typical planar feature selection algorithms,the treatment processes and lakes selected for lakes and reservoirs(not specifically stated below,collectively referred to as lakes)are studied,and algorithms such as contour graphics optimization,the purpose of selecting the results to maintain the distribution characteristics of the main body of the lake group is achieved.Through the above research,this paper proposes and implements the residential point group selection model considering the river elements,realizes the river selection model based on river hierarchy optimization,and uses the typical planar element selection model to comprehensively select the corresponding lakes and reservoirs.Finally,the above selected models are integrated and applied to the river chief system watershed map synthesis software.Through the selection and processing of the the river long watershed thematic map and the decoration of the map,the feasibility and reliability of the research method are proved from the perspective of engineering application.