Orthorectification and Geometric Quality Assessment of Very High Spatial Resolution Satellite Imagery for Common Agricultural Policy Purposes

37 sites for the checking of farmers’ aid applications under the Common Agricultural Policy (CAP), covering an area of over 10,000 km, were imaged with very high resolution (VHR) images (Ikonos, QuickBird, Eros) in the framework of an operational testing programme. Determining the performance of VHR imagery orthorectification, and geometric quality assessment of the results in relation to the different factors, were important goals of the programme. The study, located throughout the extended European Union (15 Member States and 10 accession countries) and managed by the European Commission in parallel to its operational work, was intended as a broad validation programme of VHR data use. Two sources of results and experiences – one delivered by contractors and a second one from internal reprocessing of orthorectification done at the JRC – were compared and evaluated. This paper presents results recorded for Ikonos (Geo Ortho-kit), QuickBird (Standard OrthoReady) and EROS 1A level data, applying different approaches (variants, models) to orthorectification. The results show that VHR orthoimage products generally meet the geometric specification of 2.5m (1D) RMSE corresponding to EU technical requirements. Existing limits of geometric accuracy under certain circumstances are identified and described. Quantitative and qualitative evaluations of orthorectified imagery were carried out using independent check points, according to a standardized protocol, helping to identify the influence of different factors on the geometric accuracy level of orthoimage products. A positive outcome of this assessment is a demonstration of the validity of the use of VHR remote sensing inside the CAP for control purposes, as well as for the use of spaceborne VHR in CAP applications in general.