Mapping Shallow Waters of the Baltic Sea with Sentinel-2 Imagery

Benthic habitats and changes in them are indicators of coastal water quality. Bathymetry is nearly impossible to measure with conventional methods (sonar on a ship) in shallow (less than 3-4 m) water due to high damage risk for the ship and instruments. Both water depth and bottom type are critical information for environmental monitoring, maritime spatial planning and managing of coastal waters. Airborne remote sensing can solve the problem and provide the necessary information. However, covering very large areas with airborne sensors is quite expensive. ESA launched Sentinel-2A and 2B satellites in the frame of Copernicus program. This imagery is free of charge, comes with high frequency (every 2-3 days at the latitude of Estonia) and has 10 m spatial resolution. We carried out in situ measurements to assess the suitability of Sentinel-2 to map benthic habitat and bathymetry in optically complex water like the Baltic Sea. The high frequency free data enables new possibilities in mapping shallow coastal waters.