Theory And Algorithm Of The Isoline Analyzing System

Isoline analyzing is a fundamental and important part in Visualization in Scientific Computing. It has been used widely in many different subjects such as Geoscience,Material Science,Architectonics,Surveying and Meteorology. In GeoBeans,which is a platform software of Web-based GIS independently developed by National Engineering Research Center for Geoinformatics of China and has its own copyright,Isoline analyzing is one of its important functions in Version 4.0 and Version 4.5. As a member of Geobeans development group,I accomplish this function independently.The paper mainly discusses the tracking ,building,filling and labeling of isolines etc. from the point of view of algorithm .Finally it describe the application of Isoline Analyzing System that developed by myself in ANFAS project,which is presided over by EU(European Commission).In Chapter Two and Chapter Three,this paper discusses the tracking and building of isolines from two aspect,regular grid data and random discrete data. The system adopt Griding-method to build isolines from the two data.The edge-information structure is designed firstly in program and isopoints are deposited in the edge-information linked lists ,which is convenient to the tracking and building of isolines. In addition,for regular grid data it presents an effective algorithm for some particularity that there are four isopoints in one grid cell and for random discrete data points it lays emphasis on triangulation.This paper firstly put forward three principles :Attribute principle of adjoining isolines ,Attribute principle of isoregions and Inclusion principle of ioslines after studying the character of isolines. The bivalue- topology algorithm based on boundary tracking is given ,which is founded on the three principle and is used to fill isoregions. Because this algorithm is based on vector data,it avoids the disadvantages of the algorithm based on raster data and at the same time presents a solution for inaccuracy in topological area dividing and color filling in the algorithm based on vector data. The filling algorithm brought forward independently by myself adapt to any data and any border.Besides,the paper presents a simple but useful method of isoline labeling,azimuth angle judgement algorithm . This algorithm is also introduced for the first time.In the end,all algorithm in this paper has been testified to be right. Isoline Analyzing System has been released along with the releasing of Geobeans and has been used in some applied project.