GEOMETRIC MODELS FOR THE ORIENTATION OF HIGH RESOLUTION OPTICAL SATELLITE SENSORS

Abstract

Images taken by high resolution optical satellite sensors are available with different product levels, starting with the original images over close to original images, improved by the sensor calibration, to projections to a plane with constant object height and orthoimages based on very course digital elevation models (DEMs). All imaging satellites are equipped with satellite positioning systems like GPS and attitude control systems. Some very high resolution optical satellite systems do have precise attitude determination systems allowing a geo-reference sufficient for some purposes. The direct sensor orientation is available as satellite position together with attitudes or as rational polynomial coefficients (RPCs) describing the relation between object and image position by the relation of polynomials. An improvement of the orientation based on control points is necessary. The number and type of required unknowns is not the same for the different sensors. Images projected to a plane with constant height or a course DEM do require a different mathematical model for the correct georeferencing. For some of these image products no information about the sensor geometry is published, so a geometric reconstruction or a simplified mathematical model has to be used. In addition for some images additional parameters are required for reaching the highest possible accuracy. The geometric models for handling original images are well known, but some have to be improved by special adapted parameters for an optimal solution. Not in any case orientation parameters are available with acceptable accuracy, so in some cases nearly the whole orientation is not known. An overview about different solutions with advantages and disadvantages together with the achievable accuracy will be given.