2023 Volume 2023 Issue 14 Pages 1-7
Summary Multi-view stereopsis technique can derive 3D structure from overlapping photography taken from multiple positions, which saves labor cost to obtain height information such as plant height by unmanned aerial vehicle. This technique requires validation by ground control point (GCP) or RTK-GNSS positioning by the vehicle, however, the former needs maintenance of the GCPs and manually correction before 3D construction, and the latter has not been implemented to domestic vehicles. Deriving 3D structure from photography taken by downward camera (angle: -90°) often produces systematic broad-scale deformations. Then, this study investigated the photographing condition reducing number of GCPs and minimizing error of check points by comparing the GCPs allocations and shooting angles. The results showed that oblique shooting (-60°) reduced vertical estimation error to 1.3 cm, the difference of vertical errors between center and periphery, and derived distortion even though the case of GCPs on the only four corners. On the other hand, downward shooting (-90°) produced vertical estimation error of 13 cm even though validation by 17 GCPs. Therefore, this study indicated that validation by the points on four corners with oblique shooting was the compatible practice for both labor effectiveness and accuracy of height information in cm order.
