Assessing iMET Performance and Optimal Placement on a Small Unmanned Aerial Vehicle (UAV), as a Function of Atmospheric Conditions

In the past decade, Unmanned Aerial Vehicles (UAVs) or drones have become affordable, portable, and easy to use. Drone-based sensors have been developed by various vendors and university research groups. Because of these advances, modern UAVs are an ideal platform to address the shortage of boundary layer observations. This study examines the performance of drone-based temperature sensors and their optimal placement on a 3D Robotics Inc. Iris+ quadcopter. The iMET-XQ sensor is a small sensor package manufactured by Intermet Inc. specifically for the use on UAVs. The iMET-XQ measures temperature (T), relative humidity (RH), and pressure and is equipped with a GPS sensor to provide location and timestamp information. Traditionally, T and RH sensors are placed in radiation shields to protect them from direct sunlight and rain. These shields have louvers to allow wind flow to aspirate the sensors to obtain accurate measurements of air temperature and relative humidity. Installing a radiation shield is difficult to accomplish on a UAV, but perhaps ventilation from the quadcopter rotors or movement of the UAV through the air provides sufficient aspiration for the sensors to obtain accurate measurements. The performance of iMET-XQ temperature measurements is evaluated by 1) side-by-side placement of iMET-XQ sensors near a South Alabama Mesonet tower; 2) comparing iMET sensors unexposed and in a radiation shield on the Mesonet tower; and 3) flying a quadcopter equipped with iMET XQ sensors in different locations on the drone, in hover mode near a Mesonet tower. The tower is equipped with temperature sensors whose performance have been validated and confirmed. Statistical analyses are used to determine if the locations of the sensors on the drone are significantly different and to provide recommendations for optimal sensor placement. Some preliminary 400-ft sounding data showing nocturnal to daytime boundary layer transitions will be shown.