Quantifying the Accuracy of a Quad-Rotor Unmanned Aerial Vehicle as a Platform for Atmospheric Pressure, Temperature and Humidity Measurements near the Surface.

Abstract:

Miniature multi-rotor unmanned aerial vehicles (UAVs) can be used to directly sample the lower atmosphere over land and over the ocean in the vicinity of ships or shorelines. These UAVs are generally inexpensive and easy to operate. The author used the InstantEye quad-rotor UAV, manufactured by Physical Sciences Inc., as a test platform for meteorological measurements. In this case, the atmospheric sensor was the RS-92 radiosonde manufactured by Vaisala Inc. The author will present quantitative results of several experiments performed over land at Camp Roberts, California in which the InstantEye with radiosonde sensors was flown alongside a calibrated meteorological tower, thus allowing the accuracy of the UAV measurements to be quantified. Measurements near the surface were most strongly affected by turbulent fluctuations during sunny, low wind days over a dry surface. The rotor wash (1) provides sensor aeration which counteracts radiation contamination effects (2) creates a dynamic pressure effect in lowest 1.5 m and (3) moves air from a different level (1 - 2 m). Horizontal motion of the UAV had little effect on the measurements. The accuracy of the mean temperature measurements in the surface layer during unstable conditions was estimated to be 0.2 to 0.3 C, if samples are taken for at least one minute, except in the lowest 1.5 m above the surface, where rotor wash effects brought hot surface air to the sensors, degrading the accuracy. Above the turbulent surface layer, the temperature measurements approached a 0.1 C accuracy.