Kompsat-2 Geometric Quality Assessment for Measuring the Area of European Land Parcels

Measurement errors in orthorectified imagery are very important when it comes to checking the subsidies claims made by European farmers. The Control with Remote Sensing (CwRS) Programme managed by the GeoCAP and CID actions of the Monitoring Agricultural Resources Unit of the EC Joint Research Centre (JRC) requires the establishment of guidelines to be applied by Member States when using remotely sensed imagery to verify farmers¿ claims under the EU Common Agriculture Policy (CAP) subsidies. The area of land parcels used for farming are verified based on very fine spatial resolution (VHR) orthoimages that must meet specific geometric and visual qualities. As such, all VHR orthoimages used within this context must meet or exceed the EU standard as reported in KAPNIAS et al. (2008) based on external quality control (EQC). EQC is based on the root-mean-square (RMS) error between the true geographic position and the image position of the independent check points (ICPs). The ICP are points not included in sensor model parameter estimation process and derived from an independent source preferably of higher accuracy. This report presents the applied EQC methodology and the geometric quality results recorded for the four samples of the Kompsat-2 (K2) radiometrically corrected images (processing level 1R) acquired over the JRC Maussane Test Site. The key issues identified during the testing based on the limited Kompsat-2 sample images that were made available to us are as follows: (1) The 1-D RMS errors measured on the final K2 orthoimage after the single scene correction applying either the PCI rigorous model, the PCI RPC-based or the ERDAS RPC-based model are not sensitive to the number of GCPs used if they are well-distributed and range between 9 and 15 (provided a DTM with 0.6m vertical accuracy); and they are sensitive to the overall off-nadir angle and increase with increasing off-nadir angle. (2) The average 1-D RMSE are 2.1m and 4m, while the maximum 1-D RMSE values are 3.2m and 6.2m of Easting and Northing direction respectively, provided a DTM with 0.6m vertical accuracy and the GCPs with mean RMSEx, RMSEy of 0.60 are used. (3) The orthorectified Kompsat-2 imagery do not fall within the accuracy criteria of the CwRS 1:10.000 scale requirements, i.e. an absolute 1-D RMSE not exceeding 2.5m, except where the imagery is characterised by an overall off-nadir angle close to zero degrees and the rigorous model or first order Rational Polynomial sensor model is applied.JRC.H.4-Monitoring Agricultural Resource