Low-altitude remote sensing systems for precision agriculture
Modern precision agriculture began by mapping crop fields at different scales to support agricultural planning and decision making. With the development of variable-rate technology, precision agriculture focuses more on tactical actions in seeding, fertilizer/chemical application, and irrigation instead of simply mapping the field in the current year for improvement the next year. This is a major difference between remote sensing for precision agriculture and for general earth observation. With the development of aerial- and ground-based variable-rate systems, low-altitude airborne and ground remote sensing systems, rather than satellite systems, provide high-resolution data for prescribed variable-rate operations.
We developed systems for multispectral and thermal imaging on manned agricultural aircraft, ground based on-the-go hyperspectral imaging, and hyperspectral imaging in greenhouse. Unmanned aerial vehicles (UAVs) provide a unique platform for continuous remote sensing of crop fields at very low altitudes, which is advantageous over manned aircraft. Manned aircraft often cannot fly low enough when fine detail is required, and ground systems can take discrete measurements but slowly. Ground based systems are frequently restricted by field conditions.
Herein we describe systems developed for detection of crop stress caused by multiple factors. The issues of system and data calibration are investigated and discussed. Methods and results of crop sensing using these systems are analyzed and compared. UAVs as a special platform are discussed for crop sensing based on our field practices.