Imaging from an unmanned aerial vehicle: agricultural surveillance and decision support

In September 2002, NASA's solar-powered Pathfinder-Plus unmanned aerial vehicle (UAV) was used to conduct a proof-of-concept mission in US national airspace above the 1500 ha plantation of the Kauai Coffee Company in Hawaii. While in national airspace, the transponder-equipped UAV was supervised by regional air traffic controllers and treated like a conventionally piloted aircraft. High resolution color and multispectral imaging payloads, both drawing from the aircraft's solar power system, were housed in exterior-mounted environmental pressure pods. A local area network (LAN) using unlicensed radio frequency was used for camera control and downlink of image data at rates exceeding 5 Mbit s(-1). A wide area network (WAN) allowed a project investigator stationed on the US mainland to uplink control commands during part of the mission. Images were available for enhancing, printing, and interpretation within minutes of collection. The color images were useful for mapping invasive weed outbreaks and for revealing irrigation and fertilization anomalies. Multispectral-imagery was related to mature fruit harvest from certain fields with significant fruit display on the tree canopy exterior. During 4 h loitering above the plantation, ground-based pilots were able to precisely navigate the UAV along pre-planned flightlines, and also perform spontaneous maneuvers under the direction of the project scientist for image collection in cloud-free zones. Despite the presence of ground-obscuring cumulus cloud cover of ca. 70% during the image collection period, the UAV's maneuvering capability ultimately enabled collection of cloud-free imagery throughout most of the plantation. The mission demonstrated the capability of a slow-flying UAV, equipped with downsized imaging systems and line-of-sight telemetry, to monitor a localized agricultural region for an extended time period. The authors suggest that evolving long-duration (weeks to months) UAVs stand to make a valuable future contribution to regional agricultural resource monitoring. (C) 2004 Elsevier B.V. All rights reserved.