NDVI: NDVI is a tool used to measure the plant health by determining how much light a plant is absorbing and using effectively in its growth. The algorithm that NDVI is calculated from takes the light band from the sun and then determines how much of that light the plant is taking in and using for growth. The more light that is reflected to the satellite, the less healthy a plant is. NDVI is also measured with numerical values. The scale for NDVI is -1 to +1. -1 to 0 are non-vegetative objects like roads. 0 to +1 is the scale for plant health. 0 being unhealthy vegetation and +1 being very healthy vegetation.
NDVI Red: NDVIR is the most common index used to measure the amount of light that is absorbed by the plant. The light that is absorbed is used as energy for the vegetation to grow. This will show healthy vegetation as a green color on the map and unhealthy vegetation as a red/orange color. NDVIR is better than NDVIG for early stage plants.
NDVI Green: NDVIG is another type of NDVI used to measure plant health and It uses a similar algorithm as NDVIR. The only difference is that it uses green band of light instead of red band of light in the equation. NDVIG is better than NDVIR for later stage plants.
NDVI Blue: NDVIB is another type of NDVI used to measure plant health. NDVIB is not as often used as NDVIG and NDVIR. It is typically not used in agriculture. It uses the blue band of light instead of the red or green.
NDWI: NDWI measures moisture and is great for detecting pools of water in the field. These pools of water show up on the map as red areas.
SAVI: “Soil Adjusted Vegetation Index” and is better than NDVI when there's no canopy closure. This index takes into account that there is bare soil along with the plant that light is reflecting off of. So this index works really well for early stage plants or crops that often have bare soil present.
RGB: RGB is what we'd see as humans looking down from space. This is part of the visual light spectrum, red, green and blue.
NIR: NIR is the infrared color of the image. This is a band of light humans cannot see but the satellite can.
RVI: Simple ratio- it’s the ratio of NIR to Green. This is often very sensitive to grasses and is a basis for the FarmShots pasture management system.
EVI: “Enhanced Vegetation Index” - it’s slightly more sensitive than regular NDVIR to the same kind of vegetation that NDVIR is sensitive to, but it is not the main index because it’s not well known. What makes it more sensitive is that it filters out some atmospheric inconsistency that NDVI does not.
ARVI: “Atmospherically Corrected Vegetation Index”- useful for really hazy/humid areas like a jungle.
RDVI: “Renormalized Difference Vegetation Index”- a variation on NDVI that’s very sensitive to grasses, similar to RVI.
Sentinel Satellite: The sentinel satellite constellation is composed of two satellites, each at a 10 meter resolution.
LandSat Satellite: The LandSat satellite constellation captures multispectral imagery at a 30 meter resolution.
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