AgLeader SMS now includes Sentinel 2 Imagery Analysis Downloads

Imagery Index Overview

Multi-spectral imagery that is imported into SMS via the generic File-Read options or Sentinal-2 import, will create many different image indexes that will help you
to assign a numerical value that reflects the soil or crop that is growing in a field. Some of these indexes are more useful during certain times of the growing
season than others. Below is a time line of when some of the indexes are best used.

Depending on what your goals are, there are different indexes that may better shed light on what is happening in your fields. The graphic above shows when
during the season you would use the different indexes for your goals. Use the reference information below for further explanation. There are also numerous
articles online that can provide further explanation as the indexes are all widely used and published in the agriculture industry.
Bare Soil Index
This index provides information on bare soils with little to no vegetation. It often provides value in helping to define soil regions/differences within a field. This index
will generally provide a guide to the darker soils (higher values) to the lighter soils (lower values).
OSAVI (Optimized Soil-Adjusted Vegetation Index)
This index provides information on early season plant growth. It is a variant of the Soil Adjusted Vegetation Index (SAVI), where the background soil colors are
attempted to be reduced to focus on the growing plants. OSAVI provides a fixed value for the reduction of the soil background and is best used when a
considerable amount of soil is visible during the growing season.
MSAVI2 (Modified Soil-Adjusted Vegetation Index)
This index provides information on early season plant growth. It is a variant of the Soil Adjusted Vegetation Index (SAVI), where the background soil colors are
attempted to be reduced to focus on the growing plants. MSAVI2 reduces soil noise, as well as increases the range of plant based values.
NDVI (Normalized Difference Vegetation Index)
This is one of the most common indexes to use in-season as it provides a measure of healthy growing plants. There can be times at peak growing season that
this can become saturated (> .95), at which point it is recommended to switch to NDRE to see differences in the field with low stress areas.
VARI (Visible Atmospherically Resistant Index)
This index is similar to NDVI that uses Red and NIR bands to monitor crop variations over time. In some cases this can be used to identify different phenotypes of
plants.
GNDVI (Green Normalized Difference Vegetation Index)
This index is similar to NDVI but it uses the Green Band rather than the Red band for its calculation. This index is more sensitive to the chlorophyll in the crop,
which can imply Nitrogen concentration in crops such as corn and sorghum.
NDRE (Normalized Difference Red Edge index)
Similar index to NDVI, but doesn’t become saturated and washout at high levels. This index uses the Red Edge band in place of the Red band, and is
recommended to be used when the NDVI goes beyond .95. Using this at the higher biomass portion of the crop cycle will show variation where NDVI will not.
NDMI (Normalized Difference Moisture Index)
This index is used to determine vegetation water content. It is calculated as a ratio between NIR and SWIR (Near InfraRed, and Short wave InfraRed). Lower
values in the growing season will indicate stress due to prolonged dry spells or other stress’.
PSRI (Plant Senescence Reflectance Index)
This is an index that will key off the differences of the carotenoids and chlorophyll in plants. As plants reach maturity and start to die back, the lower values of this
index will indicate where the plants are maturing slower than those with higher values which are reaching or at maturity.

This information is provided by AgLeader in the SMS Help documentation.