Principle of aerial photogrammetry

The basic principle of single photo surveying and mapping is the perspective transformation of central projection, and the geometric inversion of photography process is the basic principle of stereo surveying and mapping. Broadly speaking, the basic principle of the former case is also the geometric inversion of the photographic process. After 1930s, the geometric inversion in photography was realized by using various sophisticated instruments with complex structures. In 1950s, it was realized by mathematical analysis. Figure 1 is a schematic diagram to realize photographic geometry inversion by optical projection method. In the figure, it is assumed that two adjacent aerial photographs cover the same ground AMDC. Their image on the left P 1 is ι1m1d1c1,and the image on the right P2 is ι2 m2 D2 c 2. The distance between the two stations S 1 and S2 is the baseline B. If these two photos are put back into the same projector as the camera lens box and illuminated by a condenser, a projection beam similar to that when shooting will be projected. Then put the two projection beams in the same spatial orientation as when shooting, so that the distance between the two projection centers is b(b is the shooting baseline reduced according to the surveying and mapping scale). At this time, all the projection beams with the same name should intersect in pairs, so as to obtain the three-dimensional model of the ground A'M 'D 'C'. At this time, the topographic map can be drawn by measuring with the spatial floating marker (which can move in three dimensions).