Novel Observation of Bathymetry in the Surf Zone using a UAV-mounted Green LiDAR

For bathymetric measurements with LiDAR, a green laser light (532nm), which can penetrate clear even in seawater and reflect off the sea bottom, is used. LiDAR systems consisting of the transmission unit of the laser and the receiver of backscattering light have been large and thus typically mounted to large aircraft such as airplanes and helicopters. One of the problems of airborne LiDAR for nearshore bathymetry is that white bubbles generated by wave breaking scatter laser on the sea surface, and no laser can reach and come back from the sea bottom. Thus, multiple flights and high overlap rate are required to measure between breaking waves. In terms of cost, it is difficult to do them with a large aircraft. On the other hand, the green laser LiDAR system used here has been miniaturized so that it can be mounted on drones. The drone-mounted LiDAR has the advantage of taking a flight, focusing on the surf zone by the drone's mobility, thereby some lasers reaching the sea bottom from between the waves and the bathymetry being obtained efficiently.

In this presentation, we introduce the results of the drone-mounted LiDAR measurements in several highly transparent coral reef areas and show the usefulness of the method in bathymetric measurements in the surf zone.