| Autor: |
Zhou, Zhen, Riis‐Klinkvort, Laura, Jørgensen, Emilie Ahrnkiel, Lindenhoff, Christine, Frías, Monica Coppo, Vesterhauge, Alexander Rietz, Olesen, Daniel Haugård, Lavish, Makar, Dobrovolskiy, Alexey, Kadek, Alexey, Orlic, Niksa, Grubesa, Tomislav, Drmić, Luka, Grosen, Henrik, Nielsen, Sune, Wennerberg, Daniel, Fagerström, Viktor, Axén, Jenny, Gustafsson, David, Bauer‐Gottwein, Peter |
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| Zdroj: |
Water Resources Research; Nov2024, Vol. 60 Issue 11, p1-26, 26p |
| Abstrakt: |
Using Unoccupied Aerial Systems (UAS) equipped with optical RGB cameras and Doppler radar, surface velocity can be efficiently measured at high spatial resolution. UAS‐borne Doppler radar is particularly attractive because it is suitable for real‐time velocity determination, because the measurement is contactless, and because it has fewer limitations than image velocimetry techniques. In this paper, five cross‐sections (XSs) were surveyed within a 10 km stretch of Rönne River in Sweden. Ground‐truth surface velocity observations were retrieved with an electromagnetic velocity sensor (OTT MF Pro) along the XS at one m spacing. Videos from a UAS RGB camera were analyzed using both Particle Image Velocimetry (PIV) and Space‐Time Image Velocimetry (STIV) techniques. Furthermore, we recorded full waveform signal data using a Doppler radar at multiple waypoints across the river. An algorithm fits two alternative models to the average amplitude curve to derive the correct river surface velocity based on Gaussian models with: (a) one peak, and (b) two peaks. Results indicate that river flow velocity and propwash velocity caused by the drone can be found in XS where the flow velocity is low, while the drone‐induced propwash velocity can be neglected in fast and highly turbulent flows. To verify the river flow velocity derived from Doppler radar, a mean PIV value within the footprint of the Doppler radar at each waypoint was calculated. Finally, quantitative comparisons of OTT MF Pro data with STIV, mean PIV and Doppler radar revealed that UAS‐borne Doppler radar could reliably measure the river surface velocity. Plain Language Summary: Based on the Doppler effect occurring when electromagnetic waves are reflected by a moving target, a Doppler radar can measure the river surface flow velocity. Doppler radars mounted on Unoccupied Aerial Systems (UAS) are attractive because they are suitable for real‐time velocity determination and contactless measurement under a wide variety of environmental conditions and river sites. Here, five selected cross‐sections were surveyed within a 10 km stretch of Rönne River in Sweden by using UAS Doppler radar. The recorded raw Doppler radar signals were processed to obtain the river surface velocity and the drone‐induced propwash velocity. To validate the Doppler results, river surface velocity was recorded in situ and using image‐cross correlation techniques as well. Comparisons of flow velocities derived from different techniques indicated that the UAS Doppler radar can reliably measure the river surface velocity with the footprint resolution. This paper provided processing procedures for the raw Doppler radar signals, which are useful for further development of UAS‐borne Doppler radar. Key Points: Unoccupied Aerial Systems Doppler radar can measure river surface flow velocityWe pick the correct river surface velocity from the raw Doppler spectra, using either a Gaussian one peak model, or a Gaussian two peak modelParticle Image Velocimetry results within the Doppler footprint verify the estimated velocities from Doppler radar [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
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