Submitted to: Transactions of the ASABE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/6/2006
Publication Date: 3/7/2007
Citation: Thomson, S.J., Smith, L.A., Hanks, J.E. 2007. An instrumentation platform and gps position latency issues for remote sensing on agricultural aircraft. Transactions of the ASABE. Interpretive Summary: To help support research programs at the Stoneville, MS research center (USDA-ARS and Mississippi State University cooperating), a remote sensing platform that uses thermal imaging and ultrasonic sonar has been developed. For several research projects to date, image-based remote sensing has been used from agricultural aircraft to detect crop water stress, crop nutrient insufficiency, weed populations, field areas favorable for insect infestation, deleterious constituents in water bodies, and fire ant mounds. The ultrasonic remote sensing system is being developed to obtain accurate readings of aircraft height when spraying pesticide or other crop inputs. Accurate determination of airplaine height above the canopy is crucial since propensity for drift is greatly influenced by spray release height and must be known for research studies on spray drift. Instrumentation used on the aircraft for both thermal and digital systems is described in detail, and example images from preliminary use of the thermal imaging camera are illustrated and interpreted. Two ultrasonic systems tested worked well over a blacktop road, but the return signals from both systems were insufficient to obtain accurate readings over crop fields. Design improvements are proposed to overcome these limitations.
Technical Abstract: To help support and enhance research programs at the Stoneville research center (USDA-ARS and Mississippi State University cooperating), there has been a need to sense field variables remotely from an easily scheduled remote sensing platform. In the Application and Production Technology Research Unit (APTRU), we are developing remote sensing systems to support these programs with an eye on providing low cost imaging tools that can be used by aerial applicators for site-specific management. Image-based remote sensing methods include optical and thermal methods for detection of weeds, soil variability, crop stresses, fishpond constituents, and fire ant mounds. Field variables and features such as weeds can be observed using optical remote sensing so prescription application of crop inputs can be made. 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 detail of specific field areas. An instrumentation platform for remote sensing is described, and pilot controls required for operation of thermal and digital imaging systems were evaluated. Example images of crop fields taken with a thermal imaging camera are presented. An ultrasonic ranging system is also being used on the platform for aircraft altitude determination close to the ground, an important variable for spray drift studies. Spray drift studies necessitate accurate representation of spray height for replicated tests. Two different ultrasonic ranging systems flown in aircraft showed good response over a hard surface (blacktop road), but poor response over crop fields. Design improvements are proposed to strengthen the sonar return signal for improved response over diffuse targets such as crop fields.