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Vegetation indices are calculated using the electromagnetic spectrum
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DroneDeploy's Vegetation Index Options:
Vegetation indices are calculated using the electromagnetic spectrum
Vegetation indices are mathematical formulas that use specific image bands to assess plant health. Image bands are specified wavelength ranges within the electromagnetic spectrum captured by the drone's camera. Each band corresponds to a different part of the spectrum (e.g., visible, infrared) that allows us to detect different characteristics about plant health. Images captured by drones predominantly contain information from visible to near-infrared spectrums.
The visible spectrum is detectable by human eyes, where each color corresponds to a specific band. Standard cameras capture in Red, Green, and Blue bands, resulting in images that accurately reflect the colors as perceived by the human eye (i.e. true-color images). In this type of image, the colors appear natural, and closely resemble what one would see in reality, making it useful for visual interpretation and analysis. Vegetation indices such as VARI use Red, Green, and Blue bands from standard cameras to help visualize plant health. Read more on the mathematical formula for VARI below.
Within the infrared spectrum is the near-infrared band (NIR), which lies adjacent to the visible spectrum. Even though near-infrared bands are invisible to the human eye, they play a vital role in evaluating vegetation health, as plants respond to near-infrared light in ways that indicate their overall health. By capturing in the near-infrared bands, we are able to estimate the chlorophyll content in plants, which gives us clues to the plant's viability prior to visible changes in the plant's coloration.
When using DroneDeploy, the camera type determines which Vegetation Index options are available. Please refer to Filter and Algorithm Types Based on Camera Type for more information.
DroneDeploy's Vegetation Index Options:
Visible Atmospherically Resistant Index (VARI)
VARI is a vegetation index that evaluates the 'greenness' in plants, where greener plants are assumed to be in healthier condition. VARI is useful for mitigating atmospheric interference which enhances the ability to detect coloration differences between plants.
VARI uses Red, Green, and Blue bands to assess plant health. Since VARI only uses bands in the visible spectrum, this index is appropriate for cameras that capture in standard RGB (see Filter and Algorithm Types for more information).
VARI is calculated using the following equation:
Normalized Difference Vegetation Index (NDVI)
NDVI is an industry standard vegetation index that that assesses plant health by comparing the difference between near-infrared and red bands of the electromagnetic spectrum. NDVI measures the chlorophyll content and photosynthetic activity of plants. Higher NDVI values indicate healthier, denser vegetation, while lower values suggest stress, drought, or sparse plant cover.
Since NDVI uses the near-infrared band, this index requires a multispectral camera (see Filter and Algorithm Types for more information).
NDVI is calculated using the following equation:
Enhanced Normalized Difference Vegetation Index (ENDVI)
ENDVI is a variation of NDVI that improves sensitivity to vegetation by incorporating the Green and Blue band, which enhances the detection of chlorophyll content. ENDVI is only available for modified cameras that take false-color images.
ENDVI is calculated using the following equation:
Green Normalized Difference Vegetation Index (GNDVI)
ENDVI is another variation of NDVI that uses green reflectance instead of red reflectance. The green band improves the index's ability to detect healthy vegetation, as healthy plants reflect more green light. GNDVI is useful for landscapes with dense canopies due to a high sensitivity to chlorophyll. GNDVI is only available for modified cameras that take false-color images.
GNDVI is calculated using the following equation:
Soil Adjusted Vegetation Index (SAVI)
SAVI is a vegetation index that minimizes the influence of soil brightness when assessing plant health. Bright or reflective soils can lead to inaccurate readings of plant health by reflecting more light when soil is exposed. The SAVI equation includes a soil adjustment factor, which is effective for areas with sparse vegetation or bare soil. SAVI is only available for images taken with our supported multispectral cameras.
SAVI is calculated using the following equation:
Optimized Soil Adjusted Vegetation Index (OSAVI)
OSAVI modifies the SAVI equation by adjusting the soil correction factor to 0.16 instead of 0.5 to allow for greater soil variation. OSAVI is meant to capture vegetation health with landscapes that have variations in soil brightness, such as landscapes with relatively sparse vegetation where the soil can be seen through the canopy. OSAVI is not well suited for landscapes with high canopy cover (>50%).
OSAVI is calculated using the following equation:
Renormalized Difference Vegetation Index (RDVI)
RDVI is a variation of NDVI, where the equation is normalized to reduce the influence of soil brightness. By normalizing the reflectance values, RDVI mitigates the impact of soil reflection when assessing plant health, leading to more accurate results for landscapes with sparse vegetation.
RDVI is calculated using the following equation: