Geometric quality assessment of orthorectified VHR space image data

Two QuickBird images delivered in "basic" and "standard" processed formats and an IKONOS Geo-processed image, covering an area of 108km(2) near to Aradippou, Cyprus, were orthorectified using a Digital Elevation Model derived from medium scale map data and off-the-shelf software. The resulting orthoimages were tested for geometric correction quality using a standardized protocol. A network of ground control points (GCPs) was surveyed using a dual-frequency carrier-phase Global Positioning System receiver, with an estimated accuracy of better than 0.1 m. The GCPs were divided into two sets: a calibration set (of 18 points) was used for a repetitive orthocorrection trial using between one and four GCPs, and a validation set (of 28 points) was used to evaluate the precision of each orthoimage. The system corrected "Standard" QuickBird image delivered by the supplier was found to meet the documented specification of 14m RMSE, and is suitable for medium scale mapping applications. The upper 95% confidence limits of the one-dimensional RMSE of orthoimages made from IKONOS Geo and QuickBird Basic images were 1.65 and 1.27 meters respectively: Both systems are well within 1:10,000 scale Class I accuracy requirements of the EU Common Agricultural Policy.