Ground control pointing and geometric transformation of satellite imagery

Abstract

LANDSAT imagery has been corrected for Earth curvature and rotation, satellite attitude errors and sensor non-linearities, it still contains significant geometric distortions with the centre of the scene only located to an accuracy of a few kilometres. For some applications these errors are unimportant but an increasing number of users need geometrically transformed imagery either for direct comparison with maps or for multitemporal analysis. To determine the transformation the user must select a number of ground control points, i.e. features which are readily identifiable on both the image and a map. The transformation matrix between image and map co-ordinates is then determined and the scene resampled using interpolation techniques.