Orco_Survey

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Figure 1: The Orco River

 

The Orco River (Figure 1) flows from the Alps (maximum elevation, Becca di Moncorvè, 3 865 m a.s.l.) and discharges in the Po River (minimum elevation, 177 m a.s.l.) near Chivasso, a town in the Turin Province in Italy. Both Orco and Po rivers’ surveys were conducted between the 11th and 15th of July 2024. The survey generated signicant media interest by La Stampa,  and different local news websites (a, b, c). A total of 13 cross-sections (XSs) were selected and surveyed during this survey (Figure 2), in which 7 XSs were located in Orco river and 6 XSs located in Po river. The following datasets were collected at the Po/Orco site:

  • Orthophoto coverage using a helicopter-borne camera system operated by CNR.
  • Lidar coverage using a helicopter-borne lidar system operated by CNR.
  • Water surface elevation along Po and Orco rivers, using the UAWOS radar altimetry payload
  • Water penetrating radar bathymetry at all cross sections using UAWOS WPR payload
  • Doppler radar velocimetry at all cross sections using UAWOS Doppler radar payload
  • Various in-situ datasets for comparison and validation
  • Various satellite altimetry datasets (Sentinel, ICESat, SWOT)

A map of a river Description automatically generated

Figure 2: Overview map of the Orco/Po River survey

Figure 3 shows Doppler velocimetry results for cross section Orco S5. Different processing options were applied to the dataset (see https://doi.org/10.22541/au.170967865.54122848/v1 for details). The Doppler datasets from Orco/Po show high data quality and good consistency. Comparison with available in-situ datasets is ongoing.

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Figure 3: Doppler velocimetry results for cross section Orco S5

Figure 4 shows WPR bathymetry results for cross section Orco S5. Two separate acquisitions from July 14 and July 15 are shown. Please not the remarkable consistency of the WPR results between the two days, once we correct for the change in water surface elevation that occurred between the two acquisition days. Correction for WSE is necessary, because the WPR measures depth and not bottom elevation.

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Figure 4: WPR bathymetry results for cross section Orco S5

Figure 5 shows WSE results for Orco and Po rivers. The coverage has notable gaps due to (1) no-fly zones intersecting with the areas of interest and (2) system malfunctioning and data loss on a number of flights. However, the data that was collected is of very high quality and shows the water surface elevation evolution along the river at great detail, for instance backwater effects due to natural riffle-pool phenomena in the rivers.

Figure 5: WSE results for the Orco and Po rivers

The survey also served as an opportunity to collect GNSS, Inertial Measurement Unit (IMU) and LiDAR data with an experimental drone in the riverine environment. The purpose of this data is threefold:

  • To help improve the accuracy of the drone position (by fusing the IMU and GNSS data) to obtain robust georeferencing of the conducted airborne measurements.
  • To serve as a base of development for an obstacle avoidance algorithm based on LiDAR data to prevent crashes when operating the drone in difficult natural environments.
  • To help develop a LiDAR based cross section algorithm, to enable the drone to autonomously perform low altitude cross section flights over a river, thus alleviating pilot workload.

Figure 6: Experimental drone used for collecting GNSS, IMU and LiDAR data