L. Xingui, S. Qun, X. Qing, L. Haiyan

Institute of Surveying and Mapping, Information Engineering University, Zhengzhou, China



It is the main method to get the vector data that raster-to-vector conversion. Generally speaking, we often switch the image to a binary image or distribute the plate of colored map before vector. Sometimes we collect the geographic data on the separated original directly. But, it is inefficient, at the same time, it may lead to some consequences such as elements separation and data tattered. In order to remove the effects of map separating and thinning and extract the linear objects skeleton speedily and efficaciously from colored scanning map, this paper presents a detailed lens tracing method of liner objects based on its various appearance in image. An algorithm of part thinning and asynchronous operations is put forward. During the process of line tracing, a lens window is open and it moves along the line. Now, the contents in the window are only lines except the map background. We can put part-image into the memory of the computer and do some thinning. And then we can judge what is the middle and what is the intersection or the end of the line. According to the idea, we can extract the whole geometric information of the lines. Examination is done in many different liner objects conditions and in the actual map digitization, the system that take the algorithm as the dominant factor is used by the author. It is proved that it is rapid and perfect to fellow lines on a 24-bits scanning map in some actual data-extraction. It can be applied in many fields of data acquisition and data update of map surveying and GIS.