Torne_Survey

The Torne River flows along the border between Sweden and Finland from North to South and drains into the Gulf of Bothnia. The UAWOS focus area on the Torne was the river reach between Pello and Övertorneå (see map) and the survey was carried out from September 3^rd to 9^th, 2024. The survey generated a lot of interest in the local community and media and was also highlighted on the SMHI homepage. The following data were collected:

• Orthophoto coverage of selected river reaches
• Lidar coverage of selected river reaches
• Water surface elevation along ca 10 km of river, using the UAWOS radar altimetry payload.
• Water penetrating radar bathymetry at 24 cross sections using UAWOS WPR payload.
• Sonar bathymetry at 5 cross sections using the UAWOS tethered echosounder payload.
• Doppler radar velocimetry at 24 cross sections using UAWOS Doppler radar payload.
• Boat-borne Doppler Laser velocimetry (Teledyne ISCO LaserFlow) at one cross section using an early version of the UAWOS Doppler laser payload.
• ADCP ground truth for bathymetry, flow velocity and discharge at 5 cross sections
• Land surface elevation ground truth (submerged and unsubmerged) using an RTK for portions of 24 cross sections.
• Flow velocity ground truth using an Ott MFPro electromagnetic velocity sensor for portions of 24 cross sections.
• Various satellite altimetry datasets (Sentinel, ICESat, SWOT)

The Torne River was the largest river surveyed so far in UAWOS. Some cross sections were up to 700 m wide. As shown in the video above, the surface-following, low-altitude flights with the water penetrating radar payload worked flawlessly at all cross sections. Below are first results from the WPR and Doppler velocimetry surveys as well as some pictures illustrating ground truth data collection.

Doppler velocimetry results for cross section 4. Red dots are ADCP surface velocity estimates and white dots along right edge are MFPro ground truth.

WPR bathymetry results for cross section 4: Red dots are ADCP ground truth, white dots along the right edge are RTK ground truth.