Evaluation of the geometric accuracy of Ikonos imagery

NIMA has initiated a program to evaluate high resolution commercial sensors developed by Space Imaging, Digital Globe, Orbimage and others. This paper presents the results of accuracy evaluations of Ikonos orthophotos, stereo pairs and triangulation block adjustments. Ikonos image products were compared to a globally distributed set of Ground Control Points (GCPs) and the calculated geometric accuracy was found to be better than the published Ikonos specifications. This paper also describes some important matters relating to sensor geometry models and pays special attention to a replacement math model called the rational polynomial coefficient (RPC) model. These coefficients were used to model Ikonos stereo images, and a special adjustable form of the RPC rational function was used in multi-strip block adjustments. Comparisons to ground control and the rigorous Ikonos geometry model are provided.