Topographic Correction for Differential Illumination Effects on Ikonos Satellite Imagery

The problem of differential terrain illumination on satellite imagery has been investigated for at least 20 years and has not been solved satisfactorily. Most past research has been conducted on Landsat imagery where the look angle is nadir. There is no research on topographic correction of IKONOS imagery, which has a higher spatial resolution. The high spatial resolution of IKONOS imagery requires a more accurate digital elevation model (DEM) than is obtained using standard interpolators. This paper assesses some existing topographic correction methods and applies them to off-nadir multispectral IKONOS-2 imagery in the mountainous terrain of Lam Tsuen country park in Hong Kong. The IKONOS-2 image was orthorectified using PCI Ortho Engine achieving an accuracy of approximately 4m over the whole image. Slope and aspect parameters derived from the terrain model were applied in different topographic correction algorithms. This research makes a contribution to existing knowledge on the subject. It demonstrates existing algorithms for topographic correction of satellite image can be successfully adapted to IKONOS images.