IMPROVEMENTS IN CARTOSAT-1 STEREO ORTHOKIT DATA PRODUCTS SINCE LAUNCHING ISPRS-ISRO CARTOSAT-1 SCIENTIFIC ASSESSMENT PROGRAMME

摘要

Along-track stereo data from the two panchromatic CCD sensors Fore and Aft onboard Cartosat-1 satellite are being operationally received and data products generated after the satellite was launched by the Indian Space Research Organisation (ISRO) from the Satish Dhawan Space Centre, Sriharikota on May 05, 2005. ISPRS-ISRO Cartosat-1 Scientific Assessment Programme (C-SAP) was initiated with an announcement of opportunity on January 13, 2006, through an e-mail and a web-page announcement in Commission-IV website for evaluating the mapping potential of Cartosat-1 stereo data. A number of test sites and investigators spread across the globe were selected for this Programme by an international evaluation team. Principal Investigators provided reference data sets over the test sites for which Cartosat-1 stereo orthokit data products were provided by ISRO. The Phase-I investigations carried out by different teams have yielded useful insights for improving the Cartosat-1 stereo orthokit data products, both radiometrically as well as geometrically. Radiometrically, MTF (modulation transfer function) of the images acquired by both Fore and Aft sensors onboard Cartosat-1 have been enhanced considerably based on pre-launch ground calibration data. Geometrically, the RPCs (rational polynomial coefficients), which provide the image-to-ground geometric relationship, for the images acquired from the Fore and Aft sensors, have been modified to rectify the anomaly of occasional zero crossovers in the denominators; as well as to modify the longitude convention used in the data products to -180 to+180 degrees instead of 0 to 360 degrees. This Paper presents the details of both these radiometric and geometric improvements along with a few sample results.