Basic principles of aerial photogrammetry

The basic principle of aerial photogrammetry is perspective transformation of central projection, and the basic principle of stereo mapping is geometric inversion of projection process. The work of aerial photogrammetry is both outdoor and indoor. The field work includes: ① Joint survey of photo control points, which are generally landmark points laid on the ground before aerial photography, or obvious feature points in photos (such as road intersections), and their plane coordinates and elevations are measured by common survey methods such as angle intersection, ranging traverse, contour leveling and elevation traverse. (2) photo adjustment, that is, by interpreting photos, drawing features, landforms and other elements with prescribed topographic map symbols; Surveying and mapping without images and new important features; Pay attention to the place names obtained through investigation. (3) Comprehensive surveying and mapping, using a flat plate to survey contour lines on a single photo or photo map. The indoor work includes: ① Encrypting the control points of mapping, generally using aerial triangulation, calculating the control points needed for mapping according to the control points of photos, and checking their plane coordinates and elevations. ② Measure the original topographic map.