C or F value, the X and Y coordinates of the center of a pixel at the up-left corner of the image, can be measured according to characteristic point in topographic map.
值为栅格图像左上角像素中心在地图上的X，Y坐标，其值可以根据特征点在地形图中的坐标量测获得。
3
This paper discussed in detail algorithm of geometric rectification by scanned topographic map based on teaching model with least squares method to heighten image quality and data accuracy.