What does the encryption point mean in photogrammetry?

The encryption point in photogrammetry is a method often used in aerial triangulation, and it is a measurement method to encrypt the control points indoors according to a small number of field control points in stereo photogrammetry to obtain the elevation and plane position of the encryption point. Its main purpose is to provide absolute direction control points for regional mapping lacking field control points. Aerial triangulation is generally divided into two types: analog aerial triangulation, that is, optical mechanical aerial triangulation; Analysis of aerial triangulation, commonly known as computer encryption. Analog aerial triangulation is carried out on an omni-directional stereo measuring instrument (such as a multiplier). It is to restore the three-dimensional model of the route similar to or corresponding to photography on the instrument, select the encryption point according to the needs of surveying and mapping, and determine its elevation and plane position.

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