Geographic-feature Oriented Map Generalization Of Complex Lake

Map automatic generalization has been one of challenges in the research of geographical science over years,and so far no more relatively complete automatic generalization solution has been put forward yet.There are many research results on lake generalization because of one of the important research in water system generalization.The traditional lake generalization studies are mostly concentrated on the geometric features of lakes with relatively simple contour.However,the traditional method is difficult to generalize the lakes,which have complex shoreline,many lake branches and a large number of islands,effectively.The complex lakes have great geographical features,such as bending shoreline,narrow branch,pot-shaped branch,chain branching of islands and other geographic features within the lakes.The research for analyzing the generalize strategy of complexity lakes by concentrating on geographic features has great significance.This paper presents an approach to generalize the complex lake with considering geographic feature.Firstly,paper presents the key point in lake generalization by collecting and summarizing the relevant document.Secondly,for shoreline generalization,paper uses the stripping operation and Delaunay triangulation to calculate the width of lake-branch,and then extract the feature information of shoreline,recognizes the narrow branch and pot-shape branch by the position of features,uses the operation of dimensionality reduction and exaggeration to generalize and completes the shoreline generalization by select operation.Finally,for islands group generalization,this paper uses Minimum Spanning Tree and gestalt psychology to calculate islands group distribution and recognize the islands chain structure,propose the principle and standard in islands selection,analyze the conflict between islands and lake shore and complete the islands generalization by merging,deletion and replacement operations.Taking Dongting Lake as an example,this paper selects the data of the south Dongting Lake to verify the comprehensive method of complex lakes.Scale of the original data is 1:100 000,and the target scale of this data is 1:250 000.According to the specific needs of complex lake generalization,a prototype system of lake generalization considering geographic-feature.The constraint verifications of the experiment are the shoreline of the Lake Branch narrow features,pot-shape branch characteristics,island group distribution characteristics,island-chain morphological characteristics and visualization.The result of this experiment imply that the complex lake generalization method considering geographic-method can extract the geographic-feature inner of lake effectively,and also its visual effect is good.