Preprint Article Version 2 Preserved in Portico This version is not peer-reviewed

Challenges with Regard to Unmanned Aerial Systems (UASs) Measurement of River Surface Velocity Using Doppler Radar

Version 1 : Received: 17 September 2021 / Approved: 30 September 2021 / Online: 30 September 2021 (14:53:11 CEST)
Version 2 : Received: 5 March 2022 / Approved: 7 March 2022 / Online: 7 March 2022 (14:55:21 CET)

A peer-reviewed article of this Preprint also exists.

Bandini, F.; Frías, M.C.; Liu, J.; Simkus, K.; Karagkiolidou, S.; Bauer-Gottwein, P. Challenges with Regard to Unmanned Aerial Systems (UASs) Measurement of River Surface Velocity Using Doppler Radar. Remote Sens. 2022, 14, 1277. https://doi.org/10.3390/rs14051277 Bandini, F.; Frías, M.C.; Liu, J.; Simkus, K.; Karagkiolidou, S.; Bauer-Gottwein, P. Challenges with Regard to Unmanned Aerial Systems (UASs) Measurement of River Surface Velocity Using Doppler Radar. Remote Sens. 2022, 14, 1277. https://doi.org/10.3390/rs14051277

Journal reference: Remote Sensing 2022, 14, 1277
DOI: 10.3390/rs14051277

Abstract

Surface velocity is traditionally measured with in situ techniques such as velocity probes (in shallow rivers) or Acoustic Doppler Current Profilers (in deeper water). In the last years, researchers have developed remote sensing techniques, both optical (e.g., image-based velocimetry techniques) and microwave (e.g., Doppler radar). These techniques can be deployed from Unmanned Aerial Systems (UAS), which ensure fast and low-cost surveys also in remotely-accessible locations. We compare the results obtained with a UAS-borne Doppler radar and UAS-borne Particle Image Velocimetry (PIV) in different rivers, which presented different hydraulic–morphological conditions (width, slope, surface roughness and sediment material). The Doppler radar was a commercial 24 GHz instrument, developed for static deployment, adapted for UAS integration. PIV was applied with natural seeding (e.g., foam, debris) when possible, or with artificial seeding (woodchips) in the stream where the density of natural particles was insufficient. PIV reconstructed the velocity profile with high accuracy typically in the order of a few cm s−1 and a coefficient of determination (R2) typically larger than 0.7 (in half of the cases larger than 0.85), when compared with acoustic Doppler current profiler (ADCP) or velocity probe, in all investigated rivers. However, UAS-borne Doppler radar measurements show low reliability because of UAS vibrations, large instrument sampling footprint, large required sampling time and difficult-to-interpret quality indicators suggesting that additional research is needed to measure surface velocity from UAS-borne Doppler radar.

Keywords

UAS; drone; Doppler radar; PIV; river; velocity

Subject

EARTH SCIENCES, Geophysics

Comments (1)

Comment 1
Received: 7 March 2022
Commenter: filippo bandini
Commenter's Conflict of Interests: Author
Comment: -Paper title was changed to better communicate the content
-All figures were improved
-Changes in text were made to complly with the requests of the reviewers of Remote Sensing journal

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