Thermal Infrared

Thermal Infrared (TIR) imaging is a remote sensing technique that measures thermal radiation emitted by the Earth surface. It uses infrared sensors to create images that represent temperature variations across the surface. In vegetation studies, thermal imaging measures leaf or canopy temperature, which provides insights into plant health and environmental stress. 

The Zenmuse XT2 camera is utilized on a DJI Matrice 210 RTK (M210 RTK) drone. This camera features a TIR thermal sensor with a resolution of 640 × 512 pixels, sensitive in the spectral range of 7.5–13.5 μm. Additionally, it includes an RGB camera with a resolution of 4000 × 3000 pixels, which overlays RGB images on the thermal ones using a 1/1.7″ 12 MPixel CMOS detector. The M210 RTK quadcopter can carry a payload of 1.34 kg and is equipped with RTK technology for centimeter-level positioning accuracy. It is compatible with the Zenmuse XT2 thermal sensor.

To accurately estimate temperature using the DJI Zenmuse XT2 sensor, it is essential to correct the uncorrected temperature values provided by the sensor by removing environmental and atmospheric contributions. Emissivity values from literature for different surfaces and atmospheric transmittance, derived from temperature, relative humidity, and sensor-target distance using FLIR ResearchIR software, are used for this purpose. Once corrected, orthomosaics are created using Agisoft Metashape, aligning photos based on the drone's position and overlap. Ground control points are then used to accurately overlap the thermal and RGB mosaics.