Positioning Technology Of Space Photogrammetry

Space photogrammetry is a quick and effective means of acquiring the global basic geographical space information, and the difficulty of which is the high-precision position without ground control points. On the foundation of analyzing the main factors which influence the Space photogrammetry's position accuracy, this paper analyses researches the calibration methods of the camera station coordinates, the camera's focal length and the satellite-earth camera's inter-attitudes etc. The major contents are generalized as follows:1. On the condition of known camera photo elements of interior and exterior orientation, The ground points' space coordinates can be required by the stereoscopic pair's space intersection. It is of guidance meaning for designing the parameter of Space photogrammetry project to transform the stereoscopic pair's space intersection formulation into a accuracy estimation formulation of measuring ground points' space coordinates without ground control points.2. The camera station coordinates errors are the main factor which influences the photogrammetry position accuracy without ground control points. By Constructing high-precision test field on the ground and processing single photo space resection, Camera station coordinates precision can be calibrated. The experiment of the simulation data show that it is valid to calibrate the camera station coordinates' accuracy by single photo space resection and that the calibration accuracy is correlated to the ground points' accuracy.3. The camera parameters are another main factor of the photogrammetry position accuracy without ground control points. On the condition of approximately vertical photography, because of the correlation between the elements of interior orientation and the camera station coordinates, The camera's focal length can't be calibrated accurately just only by the single photo space resection. Introducing the laser measurement altitude data as constraints, The calibration accuracy of the camera's focal length can be improved. The experiment on the simulation data indicates that: although there is some errors of the laser measurement altitude data and the ground control points data, by making use of this method. The higher calibration accuracy can be acquired; By taking the average values of the camera's focal length values of multi-photo calibration as result, The influence of the accident errors can be eliminated effectively.4. Acquiring the ground points' space coordinates by the photogrammetry methods, according to are different control conditions, there are several data process algorithms such as with ground control points, without ground control points and the orbit extrapolation with few ground control points at the first step of the air line. Applying with ground control data or with ground control data at the first step of the air line to control position, it is effective to eliminate the cumulative error and improve the whole accuracy of the final results by increasing the camera station coordinates and the photo's attitude data as additional condition.