2019 Volume 75 Issue 2 Pages I_121-I_126
In usual, it is dangerous to measure a settlement of wave-dissipating blocks immediately after a disaster. The surveys are implemented, sometimes, with standing directly on the blocks by the surveyors. Therefore, the measurements based on UAV particularly with a RTK-GNSS system, which are provided reasonably in recent, are expected to achieve a safer, more reasonable and accurate survey. In this study, the UAV-based surveys are implemented with targeting port structures by some different systems for comparison. The first is a conventional photogrammetric survey based on a UAV. The second is the conventional survey by UAV with GCP. The third is a survey based on a UAV with an installed RTK-GNSS system, which does not require the additional GCP survey on the target structure. The last is a survey based on a UAV with PPK-GNSS system, which is a relative new method. The last system also does not require the GCP survey. The experiment shows an effectiveness of the RTK and PPK GNSS-UAV systems getting small errors no more than a few cm.