Abstract
Accurate geometric correction including ortho-rectification is considered for Landsat TM imagery of large rugged terrain. Ortho-rectification requires off-nadir distance of satellite image and accurate digital elevation model. The digital elevation model published by the National Geographycal Survey are reprojected on the UTM coordinate system of the concerned region (Iwate Prefecture) with 30m spatial resolution. A simple method for estimating the offnadir distance are proposed based on the observation of the TM image which is normally processed by NASDA. For precise geometric transformation, 120 ground control points are systematically selected, and their image coordinates and map coordinates are carefully measured. Statistical analysis of the obtained points reveals that the errors both in pixel and line positions are less than 0.7 pixel if the relief displacement is removed, otherwise the error in pixel position increases by 0.3 pixel. These errors can be statistically explained by the pixel identification error (0.5 pixel), the digitizing error (0.3 pixel), and the relief displacement (0.6 pixel) . The ortho-rectified image is consistently overlaid on the map image.
