What is the purpose of perspective transformation and important points, lines and surfaces in photogrammetry?

Perspective transformation: refers to the transformation that makes the bearing surface (perspective surface) rotate around the trajectory (perspective axis) by a certain angle according to the perspective rotation law, destroys the original projection beam, and still keeps the projection geometry on the bearing surface unchanged.

Important points, lines and surfaces: including photography center, image point, target point and nuclear point; Photographic baseline and polar line; Nuclear surface and so on.

Please refer to the textbook Photogrammetry for details.