What is aerial triangulation and aerial photogrammetry?

Aerial photogrammetry is a technique for creating two dimensional 2D or 3D models from aerial photographs, which are pictures of the Earth from a high point, usually an airplane. Aerial photogrammetry usually requires photographs of two or more angles of the same area in order to map the image, and it may or may not involve computer software. These photographs are then turned into the models by cartographers.
The Aerial photogrammetry services is used to create topographical maps. These maps may be either 2D or, more recently, 3D computer models of terrain. The resulting maps and models may be useful in analyzing both small and large geographical areas. These maps may be used as a basis for, or in conjunction with, GIS data.Also Aerial Triangulation is the calculation of true ground co-ordinates, used as the base reference in photogrammetry.