What is the basic idea of completing the whole process of photogrammetry with more than two photos?

Simulated aerial photography. Dual-image mapping, also known as stereo photogrammetry, is a unit of measurement for a pair of overlapping photos taken by two adjacent photography stations. The basic idea of this method is to simulate the aerial photography process, or the geometric inversion of the photography process. Photogrammetry refers to the technology of measuring the shape, size and spatial position of the target by combining camera and film. Since 1839, when Nips and Dale invented photography, photogrammetry has a history of 170 years.