Check Points In order to provide the benchmark to infer vertical accuracy, 3D coordinates of 1033 check points have been collected from topographic map with a scale of 1:10000. These points are homogeneously distributed in the area and the number is enough to guarantee error control reliability. Check points have a particular importance as a reference or planimetric and elevation, which are always located in areas which are presumed to be stable over the last decades, and have been reported with particular care. The elevations H are ground truth ellipsoidal heights. The vertical accuracies of the CPs are