纸质地形图扫描影像的几何校正

由于多种因素的影响,经扫描纸质地形图得到的栅格影像图均会出现不同程度的变形,为了消除或减小这种变形,结合有限元的理论和计算机图像处理的技术,提出了一种基于有限元的校正法,充分利用了地形图自带的控制点信息,将地图区域划分成若干由控制点组成的四边形单元,再对四边形单元采用双线性方程逐个进行校正.研究结果表明:该方法不仅充分利用了均匀分布的控制点信息,而且有效避免了高次项运算的缺点,提高了地形图扫描影像失真纠正的精度.

Method of Geometric Rectification on Scanned Image From Papery Topographic Map

As a result of multiple factors, Scanned Images from papery topographic map will present the distorting errors. For the sake of rectifying the errors, the geometric rectification on scanned images is discussed. Based on the theory of finite element and the technology for image processing, the method of rectifying the distorting errors on the scanned image is presented. The method takes full advantage of reference points on the topographic map, and the region of map is partitioned into some quadrilateral elements by reference points, then bilinear equation is adopted to rectify the quadrilateral region one by one. The method not only makes the best of information of reference points, but also avoids operation of polynomial equation. Precision of rectifying the distorting errors on the scanned image is remarkably enhanced.