camera (Sony NEX5N with 16 mm fixed focal length), flying altitude of
70 m, longitudinal overlap 80%, and lateral overlap 60%.
A total of 64 images were recorded providing a ground resolution of
2 cm per pixel at an estimated mean error of 2 cm (horizontal) and 6 cm
(vertical). A more detailed error analysis was performed in some of the
selected excavation areas: thesewere a larger area (8300m2) and three
smaller earth piles (see Fig. 7D). All were measured with a RTS and the
UAV.