An Empirical Model for Orientation of Alos-prism Images of Level 1b2

The Japanese satellite ALOS incorporates the PRISM sensor, dedicated to high resolution stereo imaging. It has a potential to derive elevation data compatible with medium scale topographic mapping scales, such as 1:25,000 or even larger. Being dedicated to systematic stereo coverage it can contribute for topographic mapping purposes in many undeveloped regions of the world. Rigorous photogrammetric treatment is not always a simple task for many users, for several reasons. This paper presents a methodology of image orientation using an alternative empirical sensor model, applicable to images of processing level 1B2. It is based on adjustments in image space and in height determination by a linear relation with parallax. It uses the approximate geolocation information derived from the sensor navigation instruments, provided with images Tests were realized with PRISM images of a relatively mountainous region in Portugal. A total of 50 accurate ground control points (some used as check points) were used to test the proposed method. The overall accuracy, assessed with 41 independent check points, was of 2.1 m for the planimetry and 2.6 m for height. These results are slightly worse than the ones referred in the literature for precise sensor models, but compatible with the standards for 1:25,000 scale mapping.