An effective method of vectorization in which both raster graphics and image data are converted into polygon features through tracing the run-length outline is developed. It is an important aspect in GIS to extract thematic vector information from remote sensing images and the resultant spatial analysis such as spatial overlay and spatial diffusion

which can be simplified in the raster data structures needs a powerful support of efficient vectorization technique. The run-length codes of raster have the characteristics of storing high precision image

containing the horizontal difference information

easy access

rapid conversion

operability and moderate compression ratio where these features are well shown in the paper. The concept of‘up neighbor run-length’and ‘down neighbor run-length’ is well defined and the efficient algorithms for seeking vertical neighbor run-length for vertical tracing are developed in this paper. The adaptation of vectorization technique based on run-length outline enhances computer’s ability and efficiency of handling large scale and high precision complex raster data. The result of the program test indicates that this method has stronger adaptability and weaker sensitivity to large scale and complex raster data. It is proved to be flexible and practical

as it can extract not only the arc links with topo-relation but also integral borders. This method could be widely used for raster-type geographical spatial analysis and also remote sensing images processing.