Design And Implementation Of The Geometric Distortion Correction Of Map Scanning Digitization

Military GIS most require high-precision vector topographic map library as a support, while basic vector topographic maps are obtained by scanning digitization and vectorising and other means based on the original paper maps. Large format optical scanners are commonly used to digital scan the paper map. As the optical characteristics of the scanner itself, there is a certain geometric error when digital scanning the map, which will lead to a reduced accuracy of vector topographic map, affecting the performance of GIS. Therefor the geometric distortion correction must be preceded befor vectorising.On the basis of the analysis on the causes of scanner geometric errors,this paper focus on the acquisition of the optical distortion characteristics,the generation of the distortion correction coefficient and the realization of the distortion correction algorithm. The paper achieve the high-precision automatic acquisition of coordinates of the grid image control points through the sub-prixel algorithm,the distortion correction coefficient by polyfitting the doordinates of the control points under the principle of reverse mapping and the distortion correction by using geometric transformation and the combination of bilinear interpolation method and the nearest neighbor interpolation algorithm to gray-scale interpolation.In the end,the paper use VC mixed with MATLAB programming method to achieve the geometric distortion system of map scanning digitization. After simulation,the geometric distortion of the image has been effectively corrected and reached the design requirements.