Abstract
Uncooled thermal infrared sensors are increasingly being deployed on unmanned aerial systems (UAS) for agriculture, forestry, wildlife surveys, and surveillance. The acquisition of thermal data requires accurate and uniform testing of equipment to ensure precise temperature measurements. We modified an uncooled thermal infrared sensor, specifically designed for UAS remote sensing, with a proprietary external heated shutter as a calibration source. The performance of the modified thermal sensor and a standard thermal sensor (i.e., without a heated shutter) was compared under both field and temperature modulated laboratory conditions. During laboratory trials with a blackbody source at 35 °C over a 150 min testing period, the modified and unmodified thermal sensor produced temperature ranges of 34.3–35.6 °C and 33.5–36.4 °C, respectively. A laboratory experiment also included the simulation of flight conditions by introducing airflow over the thermal sensor at a rate of 4 m/s. With the blackbody source held at a constant temperature of 25 °C, the introduction of 2 min air flow resulted in a ’shock cooling’ event in both the modified and unmodified sensors, oscillating between 19–30 °C and -15–65 °C, respectively. Following the initial ‘shock cooling’ event, the modified and unmodified thermal sensor oscillated between 22–27 °C and 5–45 °C, respectively. During field trials conducted over a pine plantation, the modified thermal sensor also outperformed the unmodified sensor in a side-by-side comparison. We found that the use of a mounted heated shutter improved thermal measurements, producing more consistent accurate temperature data for thermal mapping projects.
Highlights
Laboratory experiments were conducted to quantify the difference between the performance of a modified thermal sensor and an unmodified sensor, both of which were housed in a controlled environment
Drone-acquired thermal imagery using uncooled thermal infrared sensors is subject to substantial temperature errors due to sensor drift
The objective of this study was to assess the efficacy of an uncooled thermal infrared sensor designed for unmanned aerial systems (UAS) operations and modified with an externally mounted heated shutter
Summary
UAS-mounted sensors are increasingly being used for a range of environmental, agronomic and forestry applications [1,2,3] and have enhanced our capacity to monitor wildlife. Compared to manned aerial and satellite-based remote sensing, UAS-mounted sensors can acquire real-time, high-resolution imagery at relatively low cost. Apart from the resolution advantage over satellite systems, UAS-mounted thermal infrared sensors can deliver non-destructive, non-contact thermal maps of study areas in ways that were not previously possible. Thermal sensors have great potential for use in a variety of applications requiring accurate temperature data at high spatial and temporal resolution [4,5,6,7,8]. Applications include detection of disease infestations in forest canopy [3], assessing water stress in crops [7], and investigating transpiration and temperature fluxes of land surfaces [9]
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