Topographic mapping from small satellites : a case study of CHRIS/PROBA data

The new technology of small satellites (microsatellites) opens a new era in satellite Earth observations. Small satellites such as the ESA’s Project for On-Board Autonomy (PROBA), launched on October 22, 2001, are of interest due to their low cost, flexibility of positioning, and capability for multiangular scanning in both across-and along track directions. PROBA’s Compact High Resolution Imaging Spectrometer (CHRIS) provides multidirectional, as well as hyperspectral data at 18m resolution and is supplied mainly to the scientific community for experimental environmental applications. This research evaluates the use of various empirical models for satellite orientation and terrain modelling using multidirectional CHRIS data, and evaluates the potential of small satellites with multidirectional viewing capabilities for topographic mapping.Geometric correction and co-registration of multiangle images is essential for their use for data extraction. Ideally, rigorous mathematical models should be formulated which precisely describe the satellite motion and represent the relationship between the image and the object spaces. Using CHRIS/PROBA data, the use of rigorous mathematical models has not been fully investigated because the satellite information provided is not adequate for rigorous sensor modelling. In this paper, several alternative empirical models are tested for the orientation and 3D-geopositioning of CHRIS sensor images.The images used in this study cover extremely mountainous terrain in central Hong Kong, A set of five images from CHRIS/PROBA taken in December 2005 from different angles are used to test the applicability of different forms of the empirical models for 3D geopositioning. The accuracy of the models is tested for different numbers and distribution, of Ground Control Points (GCPs) using different combinations of observation angles and Base/Height ratios. The results obtained show high integrity of the models used for CHRIS/PROBA image orientation. In some cases, accuracy approaching one pixel could be achieved using a modest number of GCPs, and this is adequate for topographic mapping at the scale of 1:25,000.Department of Land Surveying and Geo-InformaticsRefereed conference pape