Accurate reference for shallow water bathymetry using a tilt-compensating dual-prism pole and time-synchronized robotic total stations

Abstract

Accurate and reliable reference data are key elements for advancing remote sensing techniques and validating the quality of geo data. This includes remote sensing methods for bathymetric data collection, such as SONAR or bathymetric LiDAR. In this work, we present a method for acquiring accurate bathymetric reference data for shallow water depths. We use a tilt-compensating dual-prism measurement pole combined with two time-synchronized robotic total stations to allow tilted and non-static pole measurements. The accessible water depth of our method is restricted only by the pole length. The error induced by pole tilt and movement, caused by water currents, large water depths, or the operation from unstable vehicles, is minimized by using the time-synchronized tilt information gathered from two reflectors mounted on the measurement pole. With our approach, we show in an air-only experiment that we achieve better than 1 cm height RMSE and 8 cm position RMSE for tilted measurement with a 4.65 m long pole. The variance propagation and precision values derived from our in-water study suggest an even lower position RMSE of 3 cm.