Orthorectification and Geometric Quality Assessment of Cartosat-1 for Common Agricultural Policy Monitoring

The European Union uses remotely sensed data in a large operational programme to monitor subsidies given to farmers and to identify irregularities in claims. The trend over the last few years has been a sharp increase in the use of very high resolution sensors, with a number of different sensors being used in a complementary manner. For instance, whilst instruments able to provide imagery with a ground sampling distance (GSD) of <1m make up the primary use (with acquisition in 2005 of around 150,000 km2), sensors acquiring data with around a 2m GSD are in general used as a back-up in case of primary instrument acquisition failure. Cartosat-1 falls into this 2nd category and potentially could provide useful data in the main programme. A study site located near to Mausanne-les-Alpilles (France), used since 1997 with a time series of reference data series for the checking of farmers’ aid applications, was imaged in the framework of the Cartosat-1 Scientific Assessment Programme (C-SAP). The determination of the performance of image orthorectification and geometric quality assessment of the results in relation to the different factors, were the principle goals of the programme. To this end, the availability of high quality reference data is essential. The assessment will be achieved through the quantitative and qualitative evaluations of orthorectified imagery using independent check points, according to a standardized protocol, helping to identify the influence of different factors (e.g. acquisition parameters, methods of orthorectification, site conditions, ancillary data quality) on the geometric accuracy level of orthoimage products. Two secondary objectives of the study will cover: • The testing of agricultural field area measurement performance • An assessment of the instruments ability to assist in the detection of typical crop types, in particular olive trees, vineyards and the main crops targeted under the EU subsidy programme. A positive outcome of this assessment would serve as a demonstration of the validity of the use of the CARTOSAT-1 instrument for control purposes, as well as serving to validate the instrument’s use in a particular agricultural monitoring application.