Development and evaluation of low-altitude remote sensing systems for crop production management.

Precision agriculture accounts for within-field variability for targeted treatment rather than uniform treatment of an entire field. It is built on agricultural mechanization and state-of-the-art technologies of geographical information systems (GIS), global positioning systems (GPS) and remote sensing, and is used to monitor soil, crop growth, weed infestation, insects, diseases, and water status in farm fields to provide data and information to guide agricultural management practices. Precision agriculture began with mapping of 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 controlling variable-rate seeding, fertilizer and pesticide application, and irrigation in real-time or within the crop season instead of mapping a field in one crop season to make decisions for the next crop season. With the development of aerial variable-rate systems, low-altitude airborne systems can provide high-resolution data for prescription variable-rate operations. Airborne systems for multispectral imaging using a number of imaging sensors (cameras) were developed. Unmanned aerial vehicles (UAVs) provide a unique platform for remote sensing of crop fields at slow speeds and low-altitudes, and they are efficient and more flexible than manned agricultural airplanes, which often cannot provide images at both low altitude and low speed for capture of high-quality images. UAVs are also more universal in their applicability than agricultural aircraft since the latter are used only in specific regions. This study presents the low-altitude remote sensing systems developed for detection of crop stress caused by multiple factors. UAVs, as a special platform, were discussed for crop sensing based on the researchers' studies. [ABSTRACT FROM AUTHOR]