A Calibration Procedure for Field and UAV-Based Uncooled Thermal Infrared Instruments

Area of Science:

• Remote Sensing
• Thermal Imaging
• Sensor Calibration

Background:

• Uncooled thermal cameras are valuable for environmental, industrial, and agricultural applications.
• Field and UAV-based thermal data collection face challenges like vignette effects, sensor drift, and ambient temperature influences.

Purpose of the Study:

• To develop and apply an ambient temperature-dependent radiometric calibration function for thermal infrared sensors.
• To improve the accuracy of surface temperature measurements from thermal cameras.

Main Methods:

• Evaluated an ambient temperature-dependent radiometric calibration function against three thermal infrared sensors (Apogee SI-11, FLIR A655sc, TeAx 640).
• Used calibrated resistance temperature detectors to measure black body temperature at various ambient temperatures to derive calibration equations.
• Independently calibrated each pixel for 2D thermal cameras.

Main Results:

• All calibrated systems showed significant improvement in measured surface temperatures compared to a black body target.
• Measurement bias and vignette effects were substantially reduced for FLIR A655sc and TeAx 640 cameras.
• Achieved reduced RMSE values, e.g., from 6.219 to 0.815 °C for FLIR A655sc.

Conclusions:

• The developed radiometric calibration approach is effective in enhancing the accuracy of thermal infrared sensors.
• This method enables more reliable surface temperature retrievals for field and UAV-based data collection.
• The straightforward calibration process supports broader adoption of accurate thermal imaging.