Error Problems in Aerial Photogrammetry

Aerial photography has its greatest use in mapping, in which the problem is basically one of stereoscopy. The normal case that exists when both photographic images are coplanar is used to develop the fundamental relationships that (1) the y-coordinates in both photographs for a specific point are equal, and (2) the differences in the x-coordinate value is a measure of the elevation of a point on the ground. Error sources occur in both image space and object space, and include earth curvature. Regarding photographic problems, relative orientation in which two photographs are properly oriented with respect to each other, and absolute orientation in which the two photographs are properly oriented in the object space are examined both theoretically and practically. Finally, the role of a more detailed error analysis of the photogrammetric system is demonstrated as offering the most promise for the future. Mathematical mapping is suggested as a suitable method for expressing the error relationships in photogrammetry.