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What
is NDVI?
Different wavelengths of light are either absorbed or reflected
from plants. The amount of Chlorophyll in a plant determines
its green color. That, coupled with the leaf area or “BioMass”
in a given area, determines the intensity of reflectance that
can be measured by a sensor in certain wavelengths: specifically
the Yellow wavelength (VIS) and the Near Infrared wavelength
(NIR). The Crop Circle Sensor emits its own light source and
records the reflectance in these two wavelengths.
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There are many Vegetation Indexes, but the industry standard
for turf is NDVI, or Normalized Difference Vegetative Index.
NDVI is simply a mathematical method of representing the two
wavelengths’ reflectance intensities in a way that can
best show differences between healthy turf and poor growth. |
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Specifically it is: (NIR-VIS)/(NIR+VIS). The number range is
usually between .25000 and .85000. The lower range represents
a low BioMass/Chlorophyll level and the higher Range represents
a high BioMass/Chlorophyll level (a healthy turf).
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What is the procedure?
During The Sweep™, The
Crop Circle sensor is mounted
to a mower and records reflectance once per second. This
number is attached to a distinct GPS Lat/Long position. These
points are then interpolated by Krigling to determine an average
by area (5 ft square on greens, teeboxes, and aprons on 15
ft square on fairways and primary roughs) and broken into
7 classes divided by a Quantile methodology.
Each distinct area of the golf course (green, primary rough,
teebox, fairway, and apron (approach) is compared to the others
of that type so that the superintendent can determine the
differences between “Like” areas: Fairway on 17th
Hole vs. Fairway on 3rd Hole. This affords him a mechanism
to identify and prioritize his treatment resources.
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