QCam: sUAS-Based Doppler Radar for Measuring River Discharge

Abstract

The U.S. Geological Survey is actively investigating remote sensing of surface velocity and river discharge (discharge) from satellite-, high altitude-, small, unmanned aircraft systems- (sUAS or drone), and permanent (fixed) deployments. This initiative is important in ungaged basins and river reaches that lack the infrastructure to deploy conventional streamgaging equipment. By coupling alternative discharge algorithms with sensors capable of measuring surface velocity, streamgage networks can be established in regions where data collection was previously impractical or impossible. To differentiate from satellite or high-altitude platforms, near-field remote sensing is conducted from sUAS or fixed platforms. QCam is a Doppler (velocity) radar mounted and integrated on a 3DR© Solo sUAS. It measures the along-track surface velocity by spot dwelling in a river cross section at a vertical where the maximum surface velocity is recorded. The surface velocity is translated to a mean-channel (mean) velocity using the probability concept (PC), and discharge is computed using the PC-derived mean velocity and cross-sectional area. Factors including surface-scatterer quality, flight altitude, propwash, wind drift, and sample duration may affect the radar-returns and the subsequent computation of mean velocity and river discharge. To evaluate the extensibility of the method, five science flights were conducted on four rivers of varying size and dynamics and included the Arkansas River, Colorado (CO), USA (two events); Salcha River near Salchaket, Alaska (AK), USA; South Platte River, CO, USA; and the Tanana River, AK, USA. QCam surface velocities and river discharges were compared to conventional streamgaging methods, which represented truth. QCam surface velocities for the Arkansas River, Salcha River, South Platte River, and Tanana River were 1.02 meters per second (m/s) and 1.43 m/s; 1.58 m/s; 0.90 m/s; and 2.17 m/s, respectively. QCam discharges (and percent differences) were 9.48 (0.3%) and 20.3 cubic meters per second (m3/s) (2.5%); 62.1 m3/s (−10.4%); 3.42 m3/s (7.3%), and 1579 m3/s (−18.8%). QCam results compare favorably with conventional streamgaging and are a viable near-field remote sensing technology that can be operationalized to deliver real-time surface velocity, mean velocity, and river discharge, if cross-sectional area is available.

Applications of Unmanned Aerial Systems (UASs) in Hydrology: A Review

“…The system, termed by the authors as RAPTOR-UAV, enabled to capture large-scale, nonstationary regions of the velocity field where the flow fields are persistent and chaotic. Recently, remote sensing of surface velocity and river discharge has been addressed in [92] through UAS-based doppler radars yielding results comparable to conventional streamgaging if cross-sectional area is available.…”

Measuring River Surface Velocity with Doppler Radar and Particle Image Velocimetry (PIV) Using Unmanned Aerial Systems (UASs)

“…At a short temporal scale, river waves can be dominated by eddies and secondary currents. Thus if the sampling time of a Doppler radar was inadequate and eddies were large, the radar would measure the eddy-dominated velocities rather than the surface scatterers that are located on the surface of larger scale waves, which represent the river flow primary velocity [47]. Thus the SVR instrument has internal filters to smooth velocity measurements and cancel the effect of local eddies.…”

“…In their outlook on future work, the authors discussed UAS deployment of this instrument. To date, there is only one study reporting actual UAS-deployment of a Doppler radar sensor [47], in which Fulton et al tested a continuous wave 24 GHz Doppler radar (developed by the USGS and Sommer Messtechnik) in five flights over four different rivers in the USA. UAS-borne observations were compared with another reference handheld radar and an acoustic Doppler velocimeter: differences were typically of a few cm/s when comparing the velocity value retrieved at the location of maximum velocity; however, comparisons of the horizontal velocity profile across the XS are not reported in the paper.…”

Efficient Multipath Clutter Cancellation for UAV Monitoring Using DAB Satellite-Based PBR

“…Therefore, more and more attention has been paid to the corresponding monitoring technologies as detection is required before proper disposal. Compared with other surveillance means such as laser and photoelectricity, radar-based systems have an insensitivity to environmental changes and strong all-day, all-weather applicability and, thus, are used in many applications [1][2][3][4] in which the feasibility for UAV detection has been shown in [5][6][7]. Unfortunately, the high radiation power from active radar aggravates the complexity of the surrounding electromagnetic environment, and its use might be limited to avoid other severe safety accidents in some sensitive areas, such as oil depots and granaries.…”