Photogrammetry is the process of taking a series of overlapping two dimensional photographs and combining them to create accurate 3D digital models. If you ever had a View Master when you were a kid then you have seen photogrammetry in action. Now, however, modern algorithms and high powered computers make it possible to process tens, hundreds or thousands of photographs to create three dimensional digital models of anything from small architectural details to sculptures or entire landscapes with structures.
Along with 3D models, photogrammetry can be used to create orthophotos (also known as orthomosaics or orthorectified imagery) An orthophoto is made from a series of overlapping images that have had camera lens and perspective distortion digitally removed so that the scale is uniform over the entire image. An Orthophoto has the same lack of distortion as a map or CAD drawing and can be scaled to true dimensions. Orthophotos can be used as the basis for CAD drawings, combined with CAD drawings or be brought into CAD and have dimension lines put onto them.
Photogrammetric models can be made with hand held cameras for building facades and details or with drone mounted cameras to capture entire properties.