The potential of WorldView-2 for ortho-image production within the "Control with Remote Sensing Programme" of the European Commission

The imagery acquired by the WorldView-2 sensor is of potential interest for the Control with Remote Sensing Programme of the European Commission, and therefore, should be assessed. The horizontal accuracy of the ortho-images that can be derived from WorldView-2 imagery need to be considered since the Control with Remote Sensing guidelines require that the one-dimensional Root Mean Square Error (RMSE) estimated on the external Check Points for any ortho-image should not exceed 2.5 m in order to qualify WorldView-2 as a Very High Resolution prime sensor. This work summarizes the results regarding the orientation tests for five totally overlapping WorldView-2 Panchromatic images acquired at the Maussane test site (Provence, southern France), two Pan-sharpened images acquired at the Cosenza test site (southern Italy), and nine Pan-sharpened scenes also acquired at the Cosenza test site. Tests were carried out using the Geomatica 10.2 (PCI Geomatics), the ERDAS Imagine 2011, and the SISAR software using both a rigorous model and Rational Polynomial Functions (RPFs) model with Rational Polynomial Coefficients (RPCs). The Hold-Out-Validation accuracy assessment method was considered by computing the RMSE of the residuals between estimated and reference positions of the Check Points for each horizontal component (East, North) by varying the number of Ground Control Points. In addition, the Leave-One-Out Cross Validation method was used to identify possible outliers. The following conclusions regarding the orientation were drawn. The best orientation accuracy over both sites was reached using the RPFs model with the RPCs supplied by imagery metadata and by applying a shift refinement even with four Ground Control Points. Further, the orientation accuracy was practically software independent but displayed significant dependence on the off-nadir angle (a higher accuracy for the lower off-nadir angle). Concerning the Cosenza test site, it appeared more convenient to process the two long strips (up to 28 km) instead of the corresponding separate nine scenes, since for the former case the achieved orientation accuracy was practically the same, whereas the number of required Ground Control Points was much lower. In regards to the subsequent ortho-image validation, the already mentioned requirement, a one-dimensional RMSE below 2.5 m for each horizontal component, can be reached provided that a good quality Digital Surface Model (DSM) is used. For the Maussane test site all the ortho-images satisfied the previous requirement. Since a DSM with an appropriate accuracy was not available, the results for the Cosenza test site were not considered significantly representative of the real potential of the WorldView-2 sensor, so are not presented. In order to evaluate the potentialities of WorldView-2 stereopairs for generating a DSM suitable for ortho-imagery production, tests were carried out using overlapping images from the Maussane Site Test. The results indicated that proper stereopairs could be an effective additional resource in the event of a lack of external good quality DSMs. 0 2012 Elsevier B.V. All rights reserved.