An investigation into the spatial accuracy of the IKONOS 2 orthoimagery within an urban environment

This letter reports the results of an orthorectification exercise applied to a panchromatic IKONOS image (GEO format) from the city of Athens, Greece; a region with gentle relief. Seventeen ground control points (GCPs) were collected within the framework of a differential GPS campaign, and were inserted to the orthorectification model together with a 20 m digital elevation model. The root mean square error at the GCPs was less than 0.6 pixels, while the same error at the checkpoints was less than 1 pixel. This shows that in areas where elevation changes are not large, the necessity for large-scale DEMs is diminished. We also show that users can process GEO data to the same standards of accuracy available from the Precision IKONOS data all at a lower cost and in less time.