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Article

Overcoming the Challenges of Thermal Infrared Orthomosaics Using a Swath-Based Approach to Correct for Dynamic Temperature and Wind Effects

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Hydrology, Agriculture and Land Observation Group, Water Desalination and Reuse Center, Biological and Environmental Science and Engineering Division, King Abdullah University of Science and Technology, Thuwal 23955-6900, Saudi Arabia
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VanderSat, Wilhelminastraat 43a, 2011 VK Haarlem, The Netherlands
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Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA
*
Author to whom correspondence should be addressed.
Academic Editor: Gilles Boulet
Remote Sens. 2021, 13(16), 3255; https://doi.org/10.3390/rs13163255
Received: 16 June 2021 / Revised: 4 August 2021 / Accepted: 11 August 2021 / Published: 18 August 2021
(This article belongs to the Section Remote Sensing in Agriculture and Vegetation)
The miniaturization of thermal infrared sensors suitable for integration with unmanned aerial vehicles (UAVs) has provided new opportunities to observe surface temperature at ultra-high spatial and temporal resolutions. In parallel, there has been a rapid development of software capable of streamlining the generation of orthomosaics. However, these approaches were developed to process optical and multi-spectral image data and were not designed to account for the often rapidly changing surface characteristics inherent in the collection and processing of thermal data. Although radiometric calibration and shutter correction of uncooled sensors have improved, the processing of thermal image data remains difficult due to (1) vignetting effects on the uncooled microbolometer focal plane array; (2) inconsistencies between images relative to in-flight effects (wind-speed and direction); (3) unsuitable methods for thermal infrared orthomosaic generation. Here, we use thermal infrared UAV data collected with a FLIR-based TeAx camera over an agricultural field at different times of the day to assess inconsistencies in orthophotos and their impact on UAV-based thermal infrared orthomosaics. Depending on the wind direction and speed, we found a significant difference in UAV-based surface temperature (up to 2 °C) within overlapping areas of neighboring flight lines, with orthophotos collected with tail wind being systematically cooler than those with head wind. To address these issues, we introduce a new swath-based mosaicking approach, which was compared to three standard blending modes for orthomosaic generation. The swath-based mosaicking approach improves the ability to identify rapid changes of surface temperature during data acquisition, corrects for the influence of flight direction relative to the wind orientation, and provides uncertainty (pixel-based standard deviation) maps to accompany the orthomosaic of surface temperature. It also produced more accurate temperature retrievals than the other three standard orthomosaicking methods, with a root mean square error of 1.2 °C when assessed against in situ measurements. As importantly, our findings demonstrate that thermal infrared data require appropriate processing to reduce inconsistencies between observations, and thus, improve the accuracy and utility of orthomosaics. View Full-Text
Keywords: thermal infrared; unmanned aerial vehicle; UAV; wind; flight direction; orthomosaic; precision agriculture; temperature thermal infrared; unmanned aerial vehicle; UAV; wind; flight direction; orthomosaic; precision agriculture; temperature
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MDPI and ACS Style

Malbéteau, Y.; Johansen, K.; Aragon, B.; Al-Mashhawari, S.K.; McCabe, M.F. Overcoming the Challenges of Thermal Infrared Orthomosaics Using a Swath-Based Approach to Correct for Dynamic Temperature and Wind Effects. Remote Sens. 2021, 13, 3255. https://doi.org/10.3390/rs13163255

AMA Style

Malbéteau Y, Johansen K, Aragon B, Al-Mashhawari SK, McCabe MF. Overcoming the Challenges of Thermal Infrared Orthomosaics Using a Swath-Based Approach to Correct for Dynamic Temperature and Wind Effects. Remote Sensing. 2021; 13(16):3255. https://doi.org/10.3390/rs13163255

Chicago/Turabian Style

Malbéteau, Yoann, Kasper Johansen, Bruno Aragon, Samir K. Al-Mashhawari, and Matthew F. McCabe. 2021. "Overcoming the Challenges of Thermal Infrared Orthomosaics Using a Swath-Based Approach to Correct for Dynamic Temperature and Wind Effects" Remote Sensing 13, no. 16: 3255. https://doi.org/10.3390/rs13163255

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