Technical note: Bathymetry observations of inland water bodies using a tethered single-beam sonar controlled by an unmanned aerial vehicle

摘要

High-quality bathymetric maps of inland water bodies are a commonrequirement for hydraulic engineering and hydrological science applications.Remote sensing methods, such as space-borne and airborne multispectralimaging or lidar, have been developed to estimate water depth, but areineffective for most inland water bodies, because of the attenuation ofelectromagnetic radiation in water, especially under turbid conditions.Surveys conducted with boats equipped with sonars can retrieve accurate waterdepths, but are expensive, time-consuming, and unsuitable for unnavigablewater bodies.We develop and assess a novel approach to retrieve accurate and high-resolution bathymetry maps. We measured accurate water depths using atethered floating sonar controlled by an unmanned aerial vehicle (UAV) in alake and in two different rivers located in Denmark. The developed techniquecombines the advantages of remote sensing with the potential of bathymetricsonars. UAV surveys can be conducted also in unnavigable, inaccessible, orremote water bodies. The tethered sonar can measure bathymetry with anaccuracy of  ∼ 2.1 % of the actual depth for observations up to35 m, without being significantly affected by water turbidity, bed form, orbed material.