(NDVI) normalized difference vegetation index,

is the ratio of the difference between the red and near-infrared bands divided by their sum used to identify and enhance the vegetation contribution in a digital remote sensing analysis.


refers to an electromagnetic sensor that collects data in a single wave bands that span the colors of the visible spectrum.

post processing,

is the differential correction of GPS positions at some time after the data are recorded.


describes sensing or control actions that occur instantaneously, or nearly instantaneously. An example of real-time sensing and control would be a device that optically recognizes a weed and immediately directs a spray onto that weed.

remote sensing,

is the acquisition of information by a recording device not in physical contact with an object being studied. Devices such as cameras, radar, lasers, or radio receivers can collect information from remote locations such as airplanes or satellites.


as referred to in agriculture is a visual assessment of crop condition including growth stage/maturity, plant vigor, and presence of disease, weed, and insect pests.

(SA) selective availability,

is a purposeful degradation in GPS navigation and timing accuracy that is accomplished by intentionally varying the precise time of the clocks on board the satellites, which introduces errors into the GPS signal. With selective availability, the civilian signal is limited to an accuracy of 100 meters, 95 percent probability. Military receivers with the appropriate encryption keys can eliminate the effects of SA and obtain an accuracy of approximately 21 meters (95 percent) probability.

spatial variation,

refers to differences in field conditions, such as crop yield, from one location in a field to another.

temporal variation,

refers to differences in conditions, such as soil nitrogen, from one sampling period to another.

turnkey system,

refers to the integration of information technologies into a system that is ready to operate.

(VI) vegetation index,

is a ratio created by dividing the red by the near-infrared spectral bands used to identify and enhance the vegetation contribution in a digital remote sensing analysis.

(VRT) variable-rate technology,

refers to a system that varies the rate of agricultural inputs such as seed, fertilizer, and crop protection chemicals in response to changing local conditions.

yield mapping,

refers to the process of collecting georeferenced data on crop yield and characteristics, such as moisture content, while the crop is being harvested. A yield mapping system combines the output of a yield monitor with the position information provided by a DGPS receiver.

yield monitors,

are devices that estimate the yield per area by measuring the flow rate of the crop and the area covered by the harvester.

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