AN INSTRUMENTATION PLATFORM AND GPS POSITION LATENCY ISSUES FOR REMOTE SENSING ON AGRICULTURAL AIRCRAFT

摘要

TO help support and enhance research programs at the Delta States Research Center, Stoneville, Mississippi (USDA-ARS and Mississippi State University cooperating), there has been a need to sense field variables from an easily scheduled remote sensing platform. Agricultural aircraft are widely used for aerial spraying in the mid-southern U.S., so they are also convenient platforms for remote sensing. Research programs are being supported with an eye on providing low-cost imaging tools that can be used by aerial applicators for site-specific management and that include optical and thermal methods for detection of weeds, soil variability, crop stresses, deleterious fishpond constituents, and fire ant mounds. Global Positioning System (GPS) receivers, instrumentation, and pilot controls for use of the remote sensing systems are described, and data and thermal imagery from a field application are illustrated. A novel event triggering device was used to determine positioning accuracy of the GPS receiver that is a component of the Satloc Airstar M3 guidance system. Testing this receiver was a prerequisite to testing two stand-alone GPS units (Garmin 76S and Lowrance Airmap 100) used for position-based camera triggering and image georeferencing. Satloc-derived ground position was found to be within 8 m of actual ground position using the event trigger, so stand-alone GPS units were compared with readings from the Satloc. The Garmin receiver showed a distinct influence of ground speed on position, but the Lowrance unit showed little change in position with changing ground speed. Both stand-alone GPS receivers showed a curious lead in position by as much as 2 s (126 m) over the Satloc, which should be taken into account if using stand-alone GPS receivers for camera triggering or image georeferencing.