The bathymetric survey was completed in April 2019 using a fishing boat with a Kongsberg EM2040 multibeam echosounder (Kongsberg Maritime, Horten, Norway, provided by University of Bern) in a single-head configuration (1° by 1° beam width, 300 kHz standard operating frequency; 400 depth detections per ping). The angular coverage was 148° maximum, with a coverage of up to ~3 times water depth on a flat bottom. The transducers and auxiliary sensors Kongsberg Seatex MRU5+ motion sensor (Kongsberg Seatex, Trondheim, Norway), a Trimble SPS361 heading sensor (Trimble Navigation Limited, Sunnyvale, CA, USA), a Leica GX1230 GNSS receiver (Leica Geosystems, Heerbrugg, Switzerland) using the TUSAGA Aktif GEO real-time positioning service (national active fixed GNSS, Turkey; typical position accuracy 2 to 3 cm) and a Valeport MiniSVS sound velocity sensor (Valeport Limited, Totnes, UK) were used. The transducers, motion sensor, and mini sound velocity sensor were incorporated in a rigid mounting attached to the bow of the ship. The ship speed ranged from 7-9 km/h. The vertical sound velocity in the water column was recorded daily by a Valeport Sound Velocity Profiler (SVP) that recorded pressure, temperature, and the sound velocity in the water column. Sound velocity depends on the temperature and the salinity of the water. The absolute depth accuracy depends on the correctness of the water velocity profiles, the motion sensor's capability to compensate for ship movements due to waves, positioning accuracy, the water depth and is in the range of centimeters (shallow waters) to a few decimeters (>50 m depth). Data were recorded using Kongsberg's SIS software and processed in HIPS/SIPS 10.4.13 software (University of Bern), then interpreted using ArcGIS 10.4.1.
The provided file is a 5 m-grid, and the lake-level reference used is 83.5 m a.s.l.
