Orientaton and Calibration of Alos/prism Imagery

High-resolution satellite images (HRSI) at sub-5m footprint are becoming increasingly available. A set of algorithms for processing of HRSI has been developed at the Institute of Geodesy and Photogrammetry (IGP), ETH Zurich and realized in a software suite called SAT-PP (Satellite Image Precision Processing). The SAT-PP features mainly include: GCP measurements, image georeferencing with RPC approach and various other sensor models, DSM generation with advanced multi-image geometrically constrained Least-Squares matching for Linear Array and single frame sensors, ortho-image generation, and feature extraction. The software has been used for processing of a number of high resolution satellite sensors, such as IKONOS, QuickBird, and SPOT-5 HRS/HRG. The new generation Japanese remote sensing satellite ALOS (Advanced Land Observing Satellite) has three remote-sensing instruments onboard: PRISM (Panchromatic Remote-sensing Instrument for Stereo Mapping), AVNIR-2 (Advanced Visible and Near Infrared Radiometer type-2), and PALSAR (Cloud Phased Array type L-band Synthetic Aperture Radar). PRISM is a panchromatic radiometer with 2.5-meter spatial resolution. It has three optical systems for forward, nadir and backward view. The photogrammetric processing of PRISM imagery has special requirements due to the Linear Array CCD sensor structure. The interior geometry and the exterior orientation have special characteristics, and the physical sensor model should be developed accordingly. As a Member of the ALOS Calibration/Validation Team, we have implemented new algorithms for the geometric processing of the PRISM images, in particular for the interior orientation and self-calibration. In addition, we have refined our physical sensor model according to the multiple optical camera heads of the sensor. Our rigorous model for the PRISM sensor is based on a modified bundle adjustment algorithm with the possibility to use two different trajectory models: the Direct Georeferencing Model and the Piecewise Polynomial Model. Both models were initially developed for modelling the trajectory of the airborne Linear Array CCD sensor imagery. Their implementations are modified according to the requirements of the PRISM sensor geometry. The self-calibration is introduced into the adjustment to model the systematic errors of the sensor and the system as a whole. The additional parameters for the self-calibration are defined in accordance with the physical structure of the PRISM cameras. We have tested our methods of georeferencing and DSM generation using the PRISM datasets acquired over four different testfields (Piemont, Italy, Saitama, Japan, Thun/Bern, Switzerland, and Okazaki, Japan). The rigorous sensor model performs well and results in sub-pixel accuracy for georeferencing and point positioning in all testfields. The self-calibration model has been tested in two different phases of the project separately. In the initial phase, where no laboratory calibration data was available, the use of the selfcalibration was essential to achieve good accuracy. However, in the latter phase the laboratory calibration data became available and the additional parameters became less significant. A detailed analysis of the DSM generation is presented in another publication.