Potential of Ikonos and Quickbird Imagery for Accurate 3d Point Positioning, Orthoimage and Dsm Generation

This paper describes the processing of IKONOS and QUICKBIRD imagery of two different datasets in Switzerland for analyzing the geometric accuracy potential of these images for 3D point positioning, and orthoimage and DSM generation. The first dataset consists of panchromatic and multispectral IKONOS and QUICKBIRD images covering the region of Geneva. In the second area around Thun with a height range of ca. 1650 m, the dataset consisted of a triplet and a stereo pair with an overlap of 50 %. In both areas, laser DTM/DSM existed and in Geneva also aerial orthoimages. GCPs with an accuracy of 0.2-0.4 m have been used in both sites. The investigations for 3D point positioning included 4 different sensor models, different GCP measurement, variable number of control points and area covered by them. The results showed that the Rational Polynomial Coefficient (RPC) model compared to 2D and 3D affine models are more general and can model sufficiently imaging modes that depart from linearity. This is particular so for QUICKBIRD which needs after the use of RPCs an additional affine transformation in order to reach accuracies of 1m or less. With sufficient modeling, the planimetric accuracy was 0.4 – 0.5 m, even for few GCPs and only partly covering the images. Orthoimages were generated from both QUICKBIRD and IKONOS with an accuracy of 0.5-0.8 m, using a laser DTM. A sophisticated matching algorithm was employed in Thun. In spite of various difficult conditions like snow, long shadows, occlusions due to mountains etc., the achieved accuracy without any manual editing, was 1-5 m depending on the landcover type, while in open areas it was about 1 m. Under normal conditions, this accuracy could be pushed down to about 0.5 m. Thus, IKONOS, and to a lesser degree QUICKBIRD, could be an attractive alternative for DSM generation worldwide.