Method of orthotransformation of space images in conditions of lack of cue

The paper introduces a method of prompt orthotransformation of space images, based on the integration of the orbital and polynomial methods of photogrammetric image processing. The concept of the method consists in fragmentary formation of an orthoimage. Fragments (quadrangles) of a definite size are marked in space images, so that geometric constraints between their elements are adequately described by a bidimensional polynom of the first order. The adjacent fragments have common vertexes on the contact line, providing integrity of the orthoimage being formed. The location of the fragment (the coordinates of its vertexes) is defined by the orbital method with consideration for the configuration of terrain, thus, if the fragment is small enough, it provides terrain correction for all the points of the fragment. To use the orbital method we define initial values of the orientation angles of the on-board equipment of the spaceship and the laws of variations of these angles in course of survey with subsequent specification of these values in terms of the coordinates of four check points. The compliance between tolerance points of fragments of the initial image and the image being formed is achieved on the basis of the models, the implementation of which is computationally less complex than that based on orbital methods. Experimental approbation of the proposed method proved that the method of prompt orthotransformation makes possible four-fold reduction of the time of photogrammetric space image processing   while providing comparable accuracies of the resulting images.