It was not practical to calibrate the camera simultaneously on the box
due to the experimental set up. Therefore, the camera was calibrated in two steps. In the first step the camera was
calibrated to determine the interior orientation and additional parameters accounting for systematic image errors using the testfield. Then, a strip of 7 vertical images with 60% forward overlap at an average scale of 1:88 of the box
was taken. Tie points were manually measured on the soil surface in the images and a second calibration only with
additional parameters was carried out with BLUH, after applying the first calibration for initial correction of
systematic image errors.