Abstract. High-quality bathymetric maps of inland water bodies are a common
requirement for hydraulic engineering and hydrological science applications.
Remote sensing methods, such as space-borne and airborne multispectral
imaging or lidar, have been developed to estimate water depth, but are
ineffective for most inland water bodies, because of the attenuation of
electromagnetic radiation in water, especially under turbid conditions.
Surveys conducted with boats equipped with sonars can retrieve accurate water
depths, but are expensive, time-consuming, and unsuitable for unnavigable
water bodies. We develop and assess a novel approach to retrieve accurate and high-resolution bathymetry maps. We measured accurate water depths using a
tethered floating sonar controlled by an unmanned aerial vehicle (UAV) in a
lake and in two different rivers located in Denmark. The developed technique
combines the advantages of remote sensing with the potential of bathymetric
sonars. UAV surveys can be conducted also in unnavigable, inaccessible, or
remote water bodies. The tethered sonar can measure bathymetry with an
accuracy of ∼2.1 % of the actual depth for observations up to
35 m, without being significantly affected by water turbidity, bed form, or
bed material.
Bathymetry observations of inland water bodies using a tethered
single-beam sonar controlled by an Unmanned Aerial Vehicle