What is NDVI and how is it calculated?

What is NDVI and how is it calculated?

NDVI is calculated from the visible and near-infrared light reflected by vegetation. Healthy vegetation (left) absorbs most of the visible light that hits it, and reflects a large portion of the near-infrared light. Unhealthy or sparse vegetation (right) reflects more visible light and less near-infrared light.

How do you calculate vegetation index?

Formula of SAVI vegetation index:

1. SAVI = ((NIR – Red) / (NIR + Red + L)) x (1 + L)
2. ARVI = (NIR – (2 * Red) + Blue) / (NIR + (2 * Red) + Blue)
3. EVI = 2.5 * ((NIR – Red) / ((NIR) + (C1 * Red) – (C2 * Blue) + L))
4. GCI = (NIR) / (Green) – 1.
5. SIPI = (NIR – Blue) / (NIR – Red)
6. NBR = (NIR – SWIR) / (NIR + SWIR)

What is NDVI value?

The well known and widely used NDVI is a simple, but effective index for quantifying green vegetation. The value range of the NDVI is -1 to 1. Negative values of NDVI (values approaching -1) correspond to water. Values close to zero (-0.1 to 0.1) generally correspond to barren areas of rock, sand, or snow.

How do you calculate NDVI and NDWI?

The Add Predefined Formula allows the user to choose between different analyses built into the Raster Calculator.

1. NDVI = (NIR-RED)/(NIR+RED)
2. NDWI = (G-NIR)/(G+NIR)
3. NBR = (NIR-SWIR)/(NIR+SWIR)
4. NPCRI = (Red-Blue)/(Red+Blue)
5. NDSI =(Green-SWIR) / (Green+SWIR)
6. NDGI = (NIR-Green)/(NIR+Green)
7. NDMI = (NIR – SWIR) / (NIR+SWIR)

How is NDVI used in agriculture?

At the beginning of the season, the NDVI index helps to understand how the plant has survived through the winter.

1. 1 If the NDVI is lower than 0.15, most probably all the plants died in this part of the field.
2. 2 0.15−0.2 is also a low value.
3. 3 0.2−0.3 is a relatively good value.
4. 4 0.3−0.5 is a good value.

Why is NDVI used?

Simply put, NDVI helps to differentiate vegetation from other types of land cover (artificial) and determine its overall state. It also allows to define and visualize vegetated areas on the map as well as detect abnormal changes in the growth process.

What is NDVI in agriculture?

NDVI measures the difference between visible and near-infrared (NIR) light reflectance from vegetation to create a snapshot of photosynthetic vigor. The imagery represents these differences in light reflectance using a color classification ranging from red to green, with red indicating the least vigorous crop canopy.

What does NDVI of 1 mean?

Negative values of NDVI (values approaching -1) correspond to water. Values close to zero (-0.1 to 0.1) generally correspond to barren areas of rock, sand, or snow.

What NDWI means?

Normalized Difference Water Index
The Normalized Difference Water Index (NDWI) is known to be strongly related to the plant water content. It is therefore a very good proxy for plant water stress. The Normalized Difference Water Index (NDWI) (Gao, 1996) is a satellite-derived index from the Near-Infrared (NIR) and Short Wave Infrared (SWIR) channels.

What is NDVI and NDWI?

NDWI divides the difference between reflected green-light and reflected near-infrared by the sum of those two bands. NDVI helps researchers determine the density of vegetation in an area, and NDWI gives a measurement of the soil moisture.

Is NDVI a sensor?

Radiation reflected from surfaces (e.g., plant canopies, soil) provides information about the state of the surface. Reflectance is the ratio of radiation reflected by the surface to radiation incident on the surface. NDVI sensors calculate the normalized difference vegetation index. …

How is NDVI used?

The NDVI index detects and quantifies the presence of live green vegetation using this reflected light in the visible and near-infrared bands. Put simply, NDVI is an indicator of the vegetation greenness —the density and health—of each pixel in a satellite image.

How is NDVI calculated?

NDVI is calculated on a per-pixel basis as the normalized difference between the red and near infrared bands from an image: where NIR is the near infrared band value for a cell and RED is the red band value for the cell.

Is NDVI equivalent to biomass?

The NDVI is correlated with both plant biomass (e.g. leaf area) and chlorophyll content (e.g. plant photosynthetic activity), with higher NDVI values representing more chlorophyll and biomass.

What is NDVI used for?

An NDVI is often used worldwide to monitor drought, monitor and predict agricultural production, assist in predicting hazardous fire zones, and map desert encroachment. The NDVI is preferred for global vegetation monitoring because it helps compensate for changing illumination conditions, surface slope, aspect,…

How does NDVI work?

NDVI works because when sunlight reaches a plant, certain wavelengths are absorbed while others are reflected. Chlorophyll strongly absorbs visible light while the cell structure of leaves strongly reflects near-infrared light. A spongy layer along the bottom of a plant causes these reflections.