The Construction Of Geometry Library And It's Usenesses In Automatic Cartographic Generalization

The development of computer technology promotes the development of Computational Geometry,and at the same time it extends it's application area.Now Computational Geometry is warmed welcome by many departments.The development of society,economy, science and technology makes GIS,which is known as a brinkscience,embed in departments of national economy gradually,playing a greate pole.There are various requirements to GIS data by some departments when it servers them,they often desire many different scale geography information data in a same region.But we have to devote a lot of people and a great deal of material resource to collect geography information data of different scale,at the other hand,wo must pay a great deal of resource,such as disk memory,to preserve and manage the data.So State Bureau of Surveying and Mapping puts out a project of infrastructural surveying and mapping which is mainly studied in the incremental multi-represent of state infrastructural GIS data,we hope it can realize data deriving and transfer-update of GIS information.These years cartographic workers are searching a approximate answer for above questions all along.When we find the true answer,we can only collect and preserve the data as detailed as possible,and all other bigger scale data can be derived from it.This process is named Geography Information Generalizaion. Map makers have made a lot of study in Automated Cartographic Generalization,which is a branch of Geography Information Generalizaion,and gained a good study harvest. Computational Geometry is good at geometrical computing,and it can help us carry through the process of Cartography Generalizaion.Traditional methods of Automated Cartographic Generalization only do with one object,without considering the consistent of objects' spatial relationship in fore-and-aft data.By using triangulated network and voronoi graph,we can realize simplification of objects and also preserve the consistent of spatial relationship between objects.Considering these,we make a good use of some computational knowledge and construct a fundamental library of Computational Geometry.Firstly,this text analyzes the study actuality of Automated Cartographic Generalization,and describes the structure and functions of the library combining the need of project. Secondly,it discusses the fundamental theory to construct all kinds of triangulated network and voronoi graph,and tells out their character. Thirdly,it proposes an improved method to extract the medial axes of a region and a method of group graphics generalization by medial axes.At last,a method of graphics generalization based on constrained delaunay triangle network is brought forward.