Multi-sensor integration of hydroacoustic and optoelectronic data acquired from UAV and USV vehicles on the inland waterbody

Hydrographic and photogrammetric measurements in the coastal zone are performed using hydroacoustic and optoelectronic methods, in particular with the use of Unmanned Aerial Vehicles (UAV) and Unmanned Surface Vehicles (USV). It should be remembered that each of the devices registers data in a different spatial reference system. Therefore, before starting the analysis of geospatial data, e.g. terrain relief, it is necessary to carry out the process of their integration (harmonisation). The aim of this article is to present a multi-sensor integration of hydroacoustic and optoelectronic data acquired from UAV and USV vehicles on the inland waterbody. Bathymetric, Light Detection And Ranging (LiDAR) and photogrammetric measurements were carried out on the Lake Kłodno (Poland) in 2022 using the DJI Phantom 4 RTK UAV and two unmanned vessels: AutoDron, which was equipped with a Global Navigation Satellite System (GNSS) Real Time Kinematic (RTK) receiver and a Single Beam Echo Sounder (SBES), as well as HydroDron, on which a GNSS/Inertial Navigation System (INS) and a LiDAR sensor were mounted. The topo-bathymetric chart generated using the Surfer software by the Inverse Distance to a Power (IDP) (p=1) method was developed. A Digital Terrain Model (DTM) generated by the IDP method is characterised by high accuracy. The difference between the interpolated value and the measurement value for the R68 measure is 0.055 m, while for the R95 measure, it has a value of 0.187 m. Research has shown that multi-sensor fusion of geospatial data ensures the possibility of performing bathymetric, LiDAR and photogrammetric measurements in the coastal zone in accordance with the accuracy requirements provided for the International Hydrographic Organization (IHO) Exclusive Order (horizontal position error ≤ 1 m (p=0.95), vertical position error ≤ 0.15 m (p=0.95)).