Research On Horton Code And Graphic Generalization Of Catchment

Map generalization has long been an active question in cartography and GIS field over years In the digital environment, map generalization turns to special geo—feature oriented generalization research from general geometry oriented generalization research on model algorithm, then map generalization have different semantic oriented essential generalization , this paper which emphases on catchments generalization fit the process.Map generalization is to remain primary and essential feature,and remove minor feature Different semantic elements reflect different importance based on quantity and quality characteristic. Horton code of catchments is a rank code about geography entity, and reflects the importance of river. Horton code reflects the grade relation of river network. Horton code reflects depth of child-tree of river network.The paper sees Horton code as a primary characteristic value and generalizing condition of the river network, and selects, simplifies and generalizes river based on scale of before and after generalization,, The main contents of paper include: (1)Reviews generalization concept, arithmetic operators, methods, influence factor and frame of map generalization and design, analyze core theory of feature —oriented map generalization, discuss the main context and applicable method of river feature generalization(2) Summarizes natural form and spatial configuration characteristic of the river network, and describe the river network using digraph Paper mostly researches tree —like river, identifies the direction of river based on the angle of the main and secondary reach, and identifies the main river based on most length and predominant continuation of the flow direction along the major channel , then receives the grade of river by recursion and structuralize river network, builds hiberarchy rank system of river based on Horton coding(3)Designs the model of river network based on Horton code, and organizes the data of node, branch and river. The branch structure includes the length drained area and Horton code, which benefit to operation of generalization.(4) Paper takes example for the river generalization from 1:250,000 to 1:500,000, and resolves the issue of "select what" in generalization according to the drained area, Horton code and the length of river. In the instance,generalization result has been evaluated by using the square root rule and the amount standard of the map generalization.