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Abstract. Thermal imaging is an important imaging modality for measuring the physiological parameters of the plant. Thermal images need to be calibrated and corrected in the field, especially for those taken using aerial systems, to get accurate and comparable measurements over different environmental conditions. The temperature from the aerial thermal images can be greatly affected by the atmosphere and became undesirably inaccurate. The main goal of this paper was to develop an in-field calibration method for aerial thermal imaging to correct the atmospheric effect. To calibrate thermal images, we designed a calibration panel that can maintain constant temperature using an active heating system. The calibration panel was tested in the lab and the results showed it can maintain temperature accurately at the target temperature with small oscillation and spatial nonuniformity. An in-field calibration method was proposed. To validate the method, the calibration panel and one validation target were placed on the ground and aerial thermal images were collected at 20 m above the ground. Temperature of the validation target was measured using a thermocouple. The calibrated temperature reduced the error of the validation target from 0.5ºC to 0.2ºC.