Normalized Difference Vegetation Index:
NDVI Stands for Normalized Difference Vegetation Index. NDVI is a number that tells us how Healthy and Green Plants are in a certain area. Scientists use it to check crops, forests and grasslands from satellite or drone images.
- NORMALIZAED: The number is always between 1 and 1, easy to compare.
- DIFFERENCE: Its based-on difference between two types of light that plants reflect.
- VEGETATION: Its all about plants especially green healthy ones.
- INDEX: It’s a single value that tells us how much plants life there is and how healthy it is.
- FORMULA:
- NDVI = (NIR-Red) / (NIR +Red)
Healthy plants reflect a lot of NIR and not much red, so NDVI is close to 1.
Lose to 1 -Lots of healthy green plants.
Around 0 – Not much vegetation bare soil dead plants.
Less than 0 – Water, clouds, snow, man-made surfaces.
Unhealthy or no plants reflect both NIR and red similarity, so NDVI is close to 0 or even negative.
WOKING:
NDVI helps farmers, scientists, and environmentalists.
Check crop health. Spot drought or disease. Monitor forests. Track plant growth over time.
- TNDVI = sqrt((NIR – Red) / (NIR + Red) + 0.5)
Transformed NDVI:
The formula for Transformed NDVI. This formula is a modification of the Normalized Difference Vegetation Index (NDVI) that aims to address potential issues with NDVI’s sensitivity to low vegetation cover.
NIR = Near-Infrared reflectance
RED = Red reflectance
+0.5 in the denominator is used to adjust and stabilize the result Square root is used to compress the values and make them smoother.
Functionality:
It reduces the effects of soil brightness in areas with little vegetation. It is smooths out NDVI values for better comparison, especially when vegetation is not dense. It helps in improving the contrast in areas with low NDVI values.
TNDVI is particularly useful for mapping and monitoring vegetation cover in regions with sparse vegetation, values more limited.
Aimed at improving the sensitivity of vegetation cover, especially use in arid and semi-arid regions
Normalized Difference Water Index ( Mc Feeters’)
NDWI (GREEN– NIR) / (GREEN + NIR)
Over snowy areas where red reflectance can be confusing. In wetlands or water where plants behave differently. when green light gives better results for a specific study uses the reflectance of green and near-infrared bands from satellite imagery to identify and map water bodies.
Green: Represents the reflectance in the green band of the satellite image.
NIR: Represents the reflectance in the near-infrared band of the satellite image. This normalization process highlights water bodies because water absorbs NIR light and reflects green light, leading to a positive.
Working Formula:
NDWI value ranges from -1 to +1.
Higher NDWI values (closer to +1) indicate a higher presence of water.
The McFeeters’ NDWI is a valuable tool for remote sensing applications related to water management and monitoring.
