Abstract
Several physical sources of errors have been neglected in photogrammetry because of their negligible effects compared to the required accuracy, for example, the minimum size of sensitized particle of film, tangential distortion of lens, irregular film shrinkage, image movement due to the motion of aircraftetc.
But several of them should not be ignored if the higher accuracy is considered, and some of them often produce larger errors than commonly believed.
They shall be pointed out, criticized, and estimated about their effects and correlations, some of them such as colour abberation, and image movement, result the error greater than 30cm, which can not be reduced by simple change of photo-scale.
As the conclusion, reduction of errors beyond 30cm can not be obtained for any photoscale, unless necessary physical considerations are given to those physicalphenomena.
