Method for making digital orthophoto image

Due to the differences in data sources, technical conditions and equipment, there are many ways to make digital orthophoto maps, including the following three methods:

1. All-digital photogrammetry method is realized by digital photogrammetry system, that is, after digital image pairs are internally oriented, relatively oriented and absolutely oriented, DEM is formed, unit digital differential correction is carried out according to the inverse method, and a single orthographic image is embedded. Finally, digital orthographic image is obtained by cutting according to the contour of the image, and place name annotation, kilometer grid and contour modification are carried out. After modification, draw it into DOM or burn it into CD for storage.

2. Single chip digital differential correction. If a region has DEM data and image control results, DOM data can be used directly. The main process is to scan the aerial film, orient the digital image according to the coordinates of the control points, and then use the DEM results for digital differential correction. The rest of the subsequent processes are the same as the above methods.

3. Orthophoto scanning. If there is an orthophoto map made by optical projection, the orthophoto map can be directly scanned and digitized, and then the geometric correction is carried out to obtain the data of the digital orthophoto map. Geometric correction is a direct digital simulation of scanning transformation, and the whole deformation process of scanned image can be regarded as the comprehensive result of basic deformation such as translation, scaling, rotation, affine, deflection and bending.