Main tasks of photogrammetry

Photogrammetry is a branch of surveying and mapping. Its main task is mapping topographic maps of various scales, establishing digital ground models and providing basic data for various geographic information systems and land information systems. The two major problems to be solved in photogrammetry are geometric positioning and image interpretation. Geometric positioning is to determine the size, shape and spatial position of the object being photographed. The basic principle of geometric positioning comes from the forward intersection method of surveying, which is based on two known photographic stations and two known photographic direction lines, and intersects the three-dimensional coordinates of the undetermined ground points that constitute these two photographic rays. Image interpretation is to determine the attributes of the object corresponding to the image.