Block Adjustement of Landsat-7 Etm Images

This research study shows the potential of large image-block adjustment with nadir viewing sensor images. The method uses the geometric correction system developed for multi-source images at the Canada Centre for Remote Sensing. The results with 15 Landsat-7 ETM images show that the same accuracy can be obtained with a large image block than with a single image using the same number of ground control points (GCPs). The number of GCPs depends on cartographic data accuracy to reduce the propagation of GCP error in the leastsquare block adjustment. To insure consistency and convergence in the block adjustment, strips of same-path and date images has to be generated. Furthermore, elevation tie points (with known elevation value) are used in the overlaps (North-South and East-West) because the viewing-angle differences of overlapping images are small: less than 1o in North-South overlaps and less than 10o in East-West overlaps.