Limiting External Absorptivity of UAV-Based Uncooled Thermal Infrared Sensors Increases Water Temperature Measurement Accuracy

Thermal mapping of surface waters and the land via UAVs offers exciting opportunities in many scientific disciplines; however, unresolved issues persist related to accuracy drift uncooled microbolometric thermal infrared (TIR) sensors. Curiously, most commercially available UAV-based TIR sensors are black, which will theoretically facilitate heating sensor absorbed solar radiation. Accordingly, we tested hypothesis that modifying absorptivity can reduce by limiting absorptance associated microbolometer heating. We used two identical (DJI Zenmuse XT2) but retrofitted one with polished aluminum foil alter compared temperature measurements from each accurate instream loggers. In addition, because passive measure longwave radiation emitted environment, hypotheses overcast conditions would irradiance, therefore induce drift, increases air drift. The former is contrast conceptual model others who have proposed flying increase accuracy. found foil-shielded yielded temperatures were on average 2.2 °C more than those matte black (p < 0.0001). Further, positive correlations between light intensity (a proxy for incoming irradiance) increased both Interestingly, explained 73% variability sensor, only 40% deviations sensor. Unsurprisingly, an led a decrease sensors, where 14% 31% propose discrepancy amount due changes heat energy budget arising absorptivity. Additionally, suggest fine-scale river-bed reflectance errors UAV measurements. conclude suite guidelines increasing mapping.