Bias compensation in rational functions for Ikonos satellite imagery

A method for the removal of exterior orientation biases in rational function coefficients (RPcs) for Ikonos imagery is developed. These biases, which are inherent in RPcs derived without the aid of ground control, give rise to geopositioning errors, The 3D positioning error can subsequently be compensated during spatial intersection by two additional parameters in image space that effect a translation of image coordinates. The resulting bias parameters can then be used to correct the RPCs supplied with Ikonos Geo imagery such that a practical means is provided for bias-free ground point determination, nominally to meter-level absolute accuracy, using entirely standard procedures on any photogrammetric workstation that supports Ikonos RPCs. The method requires provision of one or more ground control points. Aside from developing the bias compensation method, the paper also summarizes practical testing with bias-corrected RPCs that has demonstrated sub-meter geopositioning accuracy from Ikonos Geo imagery.