VOLUME MEASUREMENT OF SAND CARRIER USING UAV-BASED MAPPING
To improve the operation efficiency and reduce the risks associated with exposing surveyors to danger during on-site operations, this paper presents a volume measurement approach of the sand carrier using unmanned aerial vehicle (UAV) imagery. Instead of the 3D surface interpolation of the sand carrier by total station measuring method or real-time kinematic global positioning system (RTK GPS) measuring method, the finely detailed surfaces of the sand carriers are reconstructed from dense point clouds derived by UAV-based mapping. Then, the volume of sand is calculated by the differential method, which multiplies the height difference between the UAV-derived 3D surfaces of the vessel and sand by the resolution of these surfaces. A total of 10 sand carriers are selected to test and evaluate the performance of the proposed approach, the absolute values of relative deviation between the volume obtained by UAV-based and the reference volume are approximately equal to 2%, which can be considered acceptable and satisfy the need of volume measurement of sand carriers. Compared with the manual field measurement and the laser scanning-based method, the proposed approach performs better in the accuracy of volume measurement or the reliability under the circumstance of a moving carrier. The overall results suggest that UAV-mapping can be used as an effective alternative to the commonly used method for volume measurement of the sand carrier.