1.3 Notes concerning photo flights

Photogrammetric photo blocks flown with film cameras often show considerable discrepancies in the photo measurements or at the control points along the edges of the block, not harmonising with the other parts of the block. The reason for this often is a bad geometry of the first photos of a strip, which can be explained as follows: after the completion of a strip the camera is switched off. The film section for the next photo is already lying in the film plane. The film section for the following photo is partly already taken off the magazine. These film sections are now for several minutes under other environmental conditions than the film in the magazine. This can lead to an irregular film distortion, which can’t be compensated anymore. This has been proven by practical tests.

Therefore it is highly recommended for the photo flight with film camera to take two additional photos before the beginning of each new strip. These redundant photos are not to be used for evaluation.

With digital aerial cameras such effects are unknown and not to be expected.