G PHYSICS
G01 MEASURING; TESTING
G01C MEASURING DISTANCES, LEVELS OR BEARINGS; SURVEYING; NAVIGATION; GYROSCOPIC INSTRUMENTS; PHOTOGRAMMETRY OR VIDEOGRAMMETRY
11/00 Photogrammetry or videogrammetry, e.g. stereogrammetry; Photographic surveying
G01C11/04 Interpretation of pictures
G01C11/06 by comparison of two or more pictures of the same area