Geometric Investigations on ALOS/PRISM Imagery over Adana and Wellington Testfields
Sultan Aksakal(1) and Armin Gruen(1)
(1) ETH Zurich, ETH Hoenggerberg, 8093, Zurich, Switzerland
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 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, Cartosat-1, and SPOT-5 HRS/HRG.
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 (DGR) and the Piecewise Polynomial Model (PPM). The DGR and the PPM were initially developed for modelling the trajectory of the imagery acquired with aerial Linear Array CCD sensors. Their implementations are modified according to the requirements of the PRISM sensor geometry. The self-calibration is introduced to the adjustment to model the systematic errors of the sensor. The additional parameters for the self-calibration are defined in accordance with the physical structure of the PRISM cameras.
We tested our methods of georeferencing and DSM generation using the PRISM datasets acquired over a number of different testfields (Piemont, Italy, Saitama and Okazaki, Japan, and Zurich/Winterthur and Thun/Bern, Switzerland) in the past. In this paper, we present recent results for georeferencing, which we have obtained in the Adana, Turkey, and Wellington, South Africa testfields. The PRISM images over the two testfields were acquired during the same orbital pass. 75 and 67 GCPs were installed under an ESA/ESRIN contract. The rigorous sensor model performs well and results in sub-pixel accuracy for georeferencing and point positioning in both testfields, in planimetry and height. Both the DGR Model and the PPM result in the same level of accuracies. The self-calibration model has been applied to both datasets.