Sensitivity of the WorldView-2 satellite orthoimage horizontal accuracy: with respect to sensor orientation method, number and distribution of ground control points, satellite off-nadir angles and strip length

Imagery acquired by the WorldView-2 (WV2) sensor is of potential interest to the Control with Remote Sensing (CwRS) Programme of the European Commission and therefore needs to be assessed. In details, the horizontal accuracy of the orthoimages which can be derived from WV2 imagery have to be concerned, recalling that in order to qualify WV2 as a Very High Resolution (VHR) prime sensor (i.e. a sensor suitable for measuring parcel areas to the accuracy requested by the Common Agriculture Policy - CAP regulation), the CwRS guidelines requires that the one-dimensional RMSE error (i.e. in the East and North components) measured on the external Check Points - CPs for any orthoimage should not exceed 2.5 m. This report summarizes the results regarding the orientation tests of the five WorldView-2 Panchromatic (WV2 PAN) images acquired over the JRC Maussane Test Site (Provence, Southern France), two Pan-sharpened (WV2 PANSHP) images (COSE_MODE_1) acquired over Cosenza Test Site (Southern Italy) and 9 Pan-sharpened (WV2 PANSHP) scenes (COSE_MODE_3) acquired over Cosenza Test Site (Southern Italy), carried out with Geomatica (PCI Geomatics), ERDAS Imagine 2011 and SISAR software, using both Rigorous model and Rational Polynomial Functions (RPFs) model with Rational Polynomial Coefficients (RPCs). The Hold-Out-Validation accuracy assessment method (HOV) was considered, computing the Root Mean Square Error (RMSE) of the residuals between the estimated and the reference positions of the Check Points (CPs) for each horizontal component (East, North) varying the number of the GCPs. In addition the Leave-One-Out Cross Validation (LOOCV) method was been used to identify possible outliers.