Photogrammetry is the art, science, and technology of measuring geometric properties of constructed and natural features and boundaries on the surface of the earth using photographs (aerial) and digital images. The geometric properties could be length, height, area or distance between two points. Constructed features could be buildings, roads, railroads and parks. Natural features could be rivers, lakes, islands, bays, gulfs, oceans, mountains, and valleys. Stereophotogrammetry is used to estimate the coordinates of natural and constructed features. Photogrammetry is used in making topographic maps. It is also used in geology, engineering and many other fields.
To the right and below are links to the best online sources about history, art, science, technology and applications of photogrammetry and stereophotogrammetry.

Basics of Photogrammetry