Other Ways to Obtain NDVI data - field sensors (Greenseeker, Crop by rbb25794

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									                 Other Ways to Obtain NDVI data using Field Sensors -
                         Greenseeker, Crop Circle, Yara, etc.
                                         by
                                   Randy R. Price
                           K-State Extension and Research

         Remote sensing imagery is not the only way to get NDVI data of a field. Ntech®,
Crop Circle®, and Yara® sell sensor heads that record NDVI values from the toolbar or
cab of a tractor. These units bolts to the frame of a sprayer or tillage equipment and
record NDVI values as they are pulled through a field. These units are exceptionally good
since they emit and received a pulsed light source and do not use the passive light source
of the sun. This attribute means that the unit can be used any type of conditions: cloudy,
sunny, night time, shading from the tractor or implement at certain
orientations, etc.), without interference from the changing light
conditions. The units also come pre-calibrated from the factory so a
field radiometer is not needed (for the comparison of different fields or
multiple years). The only disadvantage is that the unit sees an area
approximately ½ inch thick by 24 inches wide (for the Greenseeker®),
and field mapping to a high degree of spatial acquiring (such as every
meter) may require multiple trips over the field (or the investment of multiple sensors).
Still, these units are very rugged and mapping can be done during spraying operations.
Readings are output in a serial port format which can be captured by most computers and
PDA’s using different programs. Ntech® also has programs to combine the readings with
GPS coordinates and provide mapping utilities. Their website list many researched
methods on how to use the units to save money. Typical costs for the sensor are $2000 to
$3000 per head.




         (A)                               (B)                              (C)

Figure 1: Ntech® Greenseeker system – (A) Head mounted on tractor, (B) Components
of system, (C) Field mapped with Greenseeker system.




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Figure 1: Yara ALS (active light source) system.




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