Ground photogrammetry background

185 1 year, A.Laussedat of France first compiled topographic maps by ground photogrammetry. The practice at that time was to set up a photography station on the ground first. When shooting, the optical axis of the camera remains horizontal and the image plane is in a vertical position. At least two camera stations are used to take photos of the same position, and the positions of the camera stations and the direction of the camera are determined by ordinary measurement methods. When measuring points indoors with photos, the horizontal angle and vertical angle between the direction from the camera station to each point and the optical axis are calculated according to the coordinates of the image points on a single photo. Then, using the obtained horizontal angle, the direction line from each camera station to each corresponding point is drawn on the drawing board, which is similar to the graphic intersection of flat panel instruments, and the plane position of each point is obtained, and then the elevation of each point is calculated by using the vertical angle and the measured distance. This method is called flat photogrammetry or cross photogrammetry. 190 1 year, the German C.Pulfrich created the stereo coordinate measuring instrument, and the ground photogrammetry developed into the ground stereo photogrammetry, that is, using the stereo image pairs photographed on the ground, the model was established on the ground stereo mapper, and then the topographic mapping technology was carried out. It is suitable for surveying and mapping in mountainous areas, small mountainous areas and hilly areas, and can be used for exploration in geology, metallurgy, mines, water conservancy and railways. From 1966 to 1968, China drew the topographic map of Mount Everest with the scale of 1:25000 and 1:50000 respectively.