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TitlePre-processing of RADARSAT Images of Tucuruí reservoir and Lago Grande Floodplain, Amazon.
AuthorCosta, M P; Novo, E M L; Pietsch, R W; Ahern, F
SourceInternational Symposium, Geomatics in the Era of RADARSAT (GER'97), Ottawa, Canada, May 25-30; 1997 p. 6
Alt SeriesEarth Sciences Sector, Contribution Series 20042222
AbstractSeveral acquisitions of RADARSAT data were programmed as part of the ADRO project for the Lago Grande floodplain and the Tucuruí reservoir areas in the Amazon Basin of Brazil. The general objective of the projects was to evaluate multiangle RADARSAT imagery. The evaluations were based on detecting seasonal dynamics of different habitats and to understand the relationship between C-band backscattering and aquatic plant variables. To accomplish these tasks RADARSAT images were acquired in three periods of the hydrological cycle; high flood water, rising flood water and low water. The acquired images have the following characteristics; CEOS RADARSAT format, single bean detected product, 16 bits unsigned data, SAR georeferenced fine resolution (SGF), standard mode with different incidence angles and resolution, 12.5 by 12.5 m pixel spacing; and 1(range) by 4(azimuth) looks. Image pre-processing techniques for correcting radiometric and geometric distortions of RADARSAT imagery are necessary. To retrieve relative radiomatrically calibrated data it is required to apply the reverse process of output scaling by altering the gain and offset factors. The output scaling process is performed at the Canadian Data Processing Facility in order to ensure optimum utilization of the available output dynamic range. The offset is a fixed value and the gain is range dependent. The CEOS Radiometric Data Record provides the values for the scaling factors, allowing the conversion of the digital numbers to sigma nought. The second step in pre-processing is geometric correction. The images were ortho-rectified by integrating the complete viewing geometry, the characteristics of the Earth and the cartographic projection. Maps with a scale of 1:100 000 were used for the collection of ground control points to complete de registration.

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