Research On The Method And Application Of Rapid Making Urban Topographic Map

Urban topographic map data are widely in demand in all kinds of theoretical research and practical application about city. But how to obtain urban terrain data quickly and conveniently has been become a focus of attention for users and researchers.Terrain data acquisition is the key of topographic map production, traditional measurement method of plotting topographicmap and aerial photography method for object data are high cost and low efficiency, especially urban topographic map in large scale is always difficult to achieve, the development of satellite remote sensing technology and computer technologyprovide a new way for terrain information acquisition.Remote sensing satellite can obtain high resolution image data of large scale in a short period, stereo pairs and image contains a large number of terrain and object information. Google Earth, as a virtual Earth softwareintegrated remote sensing images with the terrain height data, isavailable free of charge to users.This papergets urban terrain data and buildings based on Google Earth, computer programming and image processing technology.Firstly, write a program based on VC++6.0to call internal function of Google Earth through Google Earth API, extract elevation points of study area by the program to provide urban terrain basic data.Simulate terrain surface using of elevation points and extract the terrain contours in ArcGIS, choose projection zone and geographical transformation to converse coordinate system of contours map according to longitude and datum, prove the feasibility of this method for terrain datathroughexperiment and the accuracy analysis.Secondly, extract needed ground features from remote sensing image, which get from Google Earth, by computer image processing technology to provide urban buildings data.Account for the complexity of large scale buildings extraction, extract and remove other ground objects according to their spectral features first, then implement multi-scalesegmentation to the image without removed objects to extract buildings.Specific idea is:present a multiband ratio method based on pixel according to vegetation spectral characteristics and principle of vegetation index calculation, extract vegetation area with this method and eliminate with mask; extract shadows using of threshold segmentation method and eliminate with mask; develop a multi-scale segmentation program based on heterogeneous of spectral and shape, set scale and merge weights of spectral and shape, set threshold of buildings attributes after segmentation throughclassification function, preview the results and extract buildings outline.Finally, urban topographic map is made by overlying buildings and contours data.The method of urban topographic map production presented by this paper, can not only get contours map of study area quickly, but also can obtain the feature data such as buildings and vegetation, which make topographic map meet various actual needs such as urban flood risk analysis and urban land planning.Illustrate the practical value of acquired topographic map data with the applications in HunHe governance planning and urban flood analysis.