Author
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Thomson, Steven |
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Submitted to: Annual Agricultural Research Service Remote Sensing Workshop
Publication Type: Abstract Only Publication Acceptance Date: 2/25/2003 Publication Date: 3/6/2003 Citation: THOMSON, S.J. DIGITAL IMAGING AND THERMAL REMOTE SENSING FROM AGRICULTURAL AIRCRAFT. Annual Agricultural Research Service Remote Sensing Workshop. 2003. CD-ROM. Interpretive Summary: Technical Abstract: Imaging systems on satellites and aircraft are used to detect field variables so site-specific management plans can be implemented. These plans might include selective spraying for weeds or insects, prescription nitrogen application, or zoned irrigation management. Agricultural aircraft already used for field spraying are particularly well suited for remote sensing because they can be scheduled frequently and conveniently. The ability to schedule frequent flights is extremely important in critical periods of a crop's development where close monitoring of pending stress, for example, may be important. Data from agricultural aircraft can also supplement data from higher-flying aircraft or satellites, providing greater detail of specific field areas. Four camera systems are in various stages of implementation for agricultural aircraft. These include a digital video camera (with electronic image stabilization), high-resolution still-digital camera, a Color-Infrared (CIR) multispectral camera system, and thermal imaging system. An example application using digital video flown at 54-m altitude showed success separating spurge weeds (E. maculata L.; Euphorbia hyssopifolia L.), Johnsongrass (Sorghum halepense (L.) Pers.), and early cotton (Gossypium hirsutum L.). Supervised image classification provided good visual discrimination of plants, and data compared well with ground-collected plant identification. Using thermal data for water stress detection presents particular challenges in our humid region because of limited cooling of the crop through evaporation. This limits the resolvable canopy temperature difference for a given difference in crop stress. Preliminary ground-based thermal data showed good correlation of canopy-air temperature difference with relative humidity, but there was no correlation with data from soil water sensors. Extreme cases (irrigated vs. non-irrigated fields) did, however, indicate wide canopy temperature differences in an unusually dry summer in the Mississippi Delta. As there is evidence that temperature differences may be resolvable for practical irrigation management, a color thermal imaging system is being configured on the aircraft to detect areas of crop water stress. All remote sensing methods are being improved to both facilitate their practical use on the airplane and expand their sensing capabilities as essential components of integrated site-specific crop management. |
