Video acquired from an Uncrewed Aerial System, UAS, and hydroacoustic measurements of flow velocity obtained along the North Santiam River, Oregon, in July 2022

A reach of the North Santiam River, Oregon, was used as a case study in an ongoing effort to develop and test image velocimetry algorithms for estimating surface flow velocities in river channels from remotely sensed data. Video was acquired from an unoccupied aircraft system, UAS, and used as input to the image velocimetry algorithms. Direct measurements of flow velocity were obtained using an acoustic Doppler current profiler, ADCP, and used to assess the accuracy of the image velocimetry algorithms.

The UAS-based video was acquired from a DJI Matrice 210 quadcopter equipped with a Zenmuse X4S optical camera on July 25, 2022. The video is provided in its native form, with a frame rate of 30 Hertz and an *.mov file format. The video was acquired from a nominal flying height of 120 meters above ground level and has a duration of 32 seconds.

The in situ velocity measurements were collected using a SonTek M9 RiverSurveyor ADCP deployed from a cataraft. The SonTek RiverSurveyor Live software package was used to set up the ADCP prior to data collection, control the instrument, view the data in real-time, and save the raw data into MATLAB *.mat data files. A total of four passes back and forth across the channel were completed at a single cross section located within the field of view of the UAS-based video. These files were then read into the USGS Velocity Mapping Toolbox (VMT) and further processed to combine the four passes into a single mean cross section and compute depth-averaged velocities (Parsons et al., 2013). The VMT output was summarized by creating a single ASCII text file consisting of a header row with variable names and four columns: 1) x_meters: easting (x) spatial coordinate in meters; 2) y_meters: northing (y) spatial coordinate in meters; 3) u_meters_per_second: east (u) component of the depth averaged velocity vector in meters per second; and 4) v_meters_per_second: north (v) component of the depth averaged velocity vector in meters per second. The spatial coordinates are in the UTM Zone 10 projection, WGS84 datum.
 
Reference cited:
Parsons, D. R., Jackson, P. R., Czuba, J. A., Engel, F. L., Rhoads, B. L., Oberg, K. A., Best, J. L., Mueller, D. S., Johnson, K. K., & Riley, J. D. 2013. Velocity Mapping Toolbox, VMT: a processing and visualization suite for moving-vessel ADCP measurements. Earth Surface Processes and Landforms, 38(11), 1244–1260. https://doi.org/10.1002/esp.3367