Towards accurate and practical drone-based wind measurements with an ultrasonic anemometer

Abstract

Abstract. Wind data collection in the atmospheric boundary layer benefits from short term wind speed measurements using unmanned aerial vehicles. Fixed and rotary wing devices with diverse anemometer technology have been used in the past to provide such data, but the accuracy still has the potential to be increased. We developed a light weight drone (weight including sensor 45 min) for carrying an industry standard precision sonic anemometer. Accuracy tests have been performed with the isolated anemometer at high tilt angles in a calibration wind tunnel, with the drone flying in a large wind tunnel, and with the full system flying at different heights next to a bistatic lidar reference. The propeller-induced flow deflects the air to some extent, but this effect is compensated effectively. Our data fusion shows no signs of crosstalk between ground speed and wind speed. When compared with the bistatic lidar in very turbulent conditions, with 10 seconds averaging interval and with the UAV constantly circling around the measurement volume of the lidar reference, wind speed measurements have an average absolute bias of 1.9 % (0.073 m s−1), wind elevation average absolute bias is 0.5°, and wind azimuth average absolute bias is 1.5°, indicating excellent accuracy under challenging and dynamic conditions. The system was finally flown in the wake of a wind turbine, successfully measuring the spatial velocity deficit distribution during forward flight, yielding results that are in very close agreement to lidar measurements and the theoretical distribution. We believe that the results presented in this paper can provide important information for designing flying systems for precise air speed measurements either for short duration at multiple locations (battery powered) or for long duration at a single location (power supplied via cable). UAVs that are able to accurately measure three-dimensional wind might be used as cost effective and flexible addition to measurement masts and lidar scans.

Ultra-Light Airborne Measurement System for Investigation of Urban Boundary Layer Dynamics

“…Atmospheric measurements by using a UAV can be applied in high-resolution research, verification of modeling results [ 58 ] and as an additional source for data assimilation in the lower troposphere [ 59 ]. Recent study indicates that UAVs that are able to accurately measure three-dimensional wind might be used as a cost-effective and flexible addition to measurement masts and LIDAR scans [ 60 ].…”

Unmanned Aerial Vehicle Communications for Civil Applications: A Review

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How accurate are ultrasonic anemometers, calibrated in a laminar wind tunnel, under turbulent conditions?

“…This study examines two ultrasonic anemometers: the Gill HS-100, a high-end three-axis research anemometer used to classify atmospheric stability and analyse offshore wind fields in the Belgian part of the North Sea [7], and the Anemoment TriSonica Mini. The TriSonica Mini is compact and lightweight, making it particularly suitable for mounting on unmanned aircraft systems, and could therefore be a cost-effective solution for offshore wind profiling [8,9] instead of using floating met masts or Lidars. However, when mounted on a drone, inaccurate measurements can eventually occur under the influence of the drone's pitch and roll angle and the influence of the drone's propeller wash [10].…”