PSI PlantPen NDVI 300, Инструкция по эксплуатации

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PRI - PHOTOCHEMICAL REFLECTANCE INDEX
The Photochemical Reflectance Index or PRI is a reflectance measurement. The PRI is sensitive to changes in
carotenoid pigments (e.g. xanthophyll pigments) in live foliage. Carotenoid pigments are indicative of
photosynthetic light use efficiency, or the rate of carbon dioxide uptake by foliage per unit energy absorbed. As
such, it is used in studies of vegetation productivity and stress. Because the PRI measures plant responses to
stress, it can be used to assess general ecosystem health using satellite data or other forms of remote sensing.
Applications include vegetation health in evergreen shrublands, forests, and agricultural crops prior to
senescence. PRI is defined by the following equation using reflectance (ρ) at 531 and 570 nm wavelength:
The values range from -1 to 1.
NDVI - NORMALIZED DIFFERENCE VEGETATION INDEX
Normalized Difference Vegetation Index or NDVI is an important indicator of chlorophyll content in plants.
The device compares reflected light at two distinct wavelengths, 660 and 740 nm.
The NDVI is calculated from these individual measurements as follows:
where VIS and NIR stand for the spectral reflectance measurements acquired in the visible (red) and near-
infrared regions, respectively These spectral reflectances are themselves ratios of the reflected over the
incoming radiation in each spectral band individually, hence they take on values between 0.0 and 1.0. By
design, the NDVI itself thus varies between -1.0 and +1.0. It should be noted that NDVI is functionally, but not
linearly, equivalent to the simple infrared/red ratio (NIR/VIS). The advantage of NDVI over a simple
infrared/red ratio is therefore generally limited to any possible linearity of its functional relationship with
vegetation properties (e.g. biomass). The simple ratio (unlike NDVI) is always positive, which may have practical
advantages, but it also has a mathematically infinite range (0 to infinity), which can be a practical disadvantage
as compared to NDVI. Also in this regard, note that the VIS term in the numerator of NDVI only scales the
result, thereby creating negative values. NDVI is functionally and linearly equivalent to the ratio NIR / (NIR+VIS),
which ranges from 0 to 1 and is thus never negative nor limitless in range.But the most important concept in
the understanding of the NDVI algebraic formula is that, despite its name, it is a transformation of a spectral
ratio (NIR/VIS), and it has no functional relationship to a spectral difference (NIR-VIS).