18
Meter Indexes
The LCD of the TCM500 NDVI meter displays
measurements in one of three modes (see
MODE
key p.
11). The modes are described below:
1.) Normalized Difference Vegetative Index (NDVI)
NDVI is defined as:
NIR - Red
NDVI = ----------------
NIR + Red
Where:
NDVI = Normalized Difference Vegetation Index
NIR = Reflectance in the band of 850 + 5 nm
Red = Reflectance in the band of 660 + 5 nm
2.) Grass Index
The Grass Index has a scale of 1 to 9 and approximates
the rating a visual observer would assign to the turf grass.
This provides a more objective value for this, generally,
very subjective parameter. The Grass Index is calculated
as follows:
Grass Index = (NDVI X 6.6) + 2.26
3.) Reflectance Values
The percent of incident light of each wavelength band that
is reflected back to the optical sensor in the meter. These
same reflectance values are used to calculate NDVI and
the Grass Index.
