Submitted to: International Society Remote Sensing of Environment
Publication Type: Proceedings
Publication Acceptance Date: June 18, 2003
Publication Date: November 10, 2003
Citation: THOMSON, S.J., VOGT, J.T. APPLICATIONS FOR THERMAL REMOTE SENSING ON A FIELD SCALE USING GROUND-BASED METHODS AND AGRICULTURAL AIRCRAFT. INTERNATIONAL SOCIETY REMOTE SENSING OF ENVIRONMENT. 2003. CD-ROM paper no. PS-V-7.pdf. Interpretive Summary: Detection of land features from the air sometimes requires sophisticated methods. Surface temperature can be used as criteria to determine crop water stress for irrigation scheduling or to detect ground features such as fire ant mounds. Remote sensing may be useful for tracking fire ant status as self-sustaining biological control agents are introduced. Little labor and intervention by the farmer would be required when using remote sensing to detect crop water stress, since there would be no in-field instruments to read or water balance model outputs to interpret for irrigation scheduling. A thermal image of an entire field could allow the farmer to schedule different parts of a field for irrigation or select a sequence of fields to irrigate based on relative water need. Higher canopy temperatures can signify crop water stress, but temperature elevation for a given increase in stress is smaller in a humid region like the Midsouth compared with an arid region due to limited canopy cooling by evaporation. Thus, detection of a smaller temperature difference requires sensitive instruments and more careful consideration of plant and weather factors. An experiment was conducted from agricultural aircraft in a humid climate to detect relative water stress in a crop field using a thermal imaging camera. Ground-based infrared temperature sensors and soil water sensors were used to provide data for comparison with data from imagery. Thermal imaging was also used to detect the presence of fire ant mounds from the bucket of a power company truck on a levee overlooking a field. Preliminary data showed that relative stress differences could be observed between irrigated and non-irrigated fields using thermal imagery, but there was no correlation with data from soil water sensors within the same cotton field. Fire ant mounds were distinguishable from most surrounding ground features, and their shape characteristics might be useful to further distinguish them from other ground features exhibiting similar temperature signatures.
Technical Abstract: Infrared thermometry and thermal imaging were evaluated to detect crop water stress and the presence of fire ant (S. richteri Forel) mounds. Infrared temperature sensors were used to obtain leaf temperature readings for cotton (Gossypium hirsutum L.) in a humid climate. A color thermal imaging camera was installed on agricultural aircraft to obtain data for determination of relative water stress for soybean (Glycine max (L.) Merr) and cotton. Granular-matrix sensors were placed at six stations in the cotton field to indicate soil water status for preliminary comparison with leaf temperature data obtained using infrared thermometry. Fire ant mounds were detected by thermal imagery from a bucket truck approx. 15-m above a levee overlooking a field. Differences in temperature over a fully closed soybean canopy were discernable from thermal images. Results of the crop study also indicated good potential for detection of crop vigor tied to soil type differences in cotton. Fire ant mounds were distinguishable from surrounding ground features, and thermal signatures exhibited distinct shape characteristics.