Contents
What is indices in remote sensing?
A spectral index is a mathematical equation that is applied on the various spectral bands of an image per pixel. This translates to approximately 10.000 by 10.000 pixels for the bands that have 10 meters spatial resolution. Half by half for the bands that have 20 meters spatial resolution, etc.
What do spectral indices do?
Spectral indices are combinations of the pixel values from two or more spectral bands in a multispectral image. Spectral indices are designed to highlight pixels showing the relative abundance or lack of a land-cover type of interest in an image.
What is NDVI NDWI?
NDVI is the difference between the visible (red) and near-infrared (nir) bands, over their sum. The NDVI is a measure of vegetation amount and condition. NDWI divides the difference between reflected green-light and reflected near-infrared by the sum of those two bands.
How to calculate the NDVI of a planet?
Calculate NDVI 1 Extract the Visible Red and NIR bands. In a python script, open the image and extract just the Red and Near-infrared bands, numbers 3 and 4. 2 Normalize to Top of Atmosphere Reflectance. 3 Perform the NDVI calculation. 4 Save the NDVI image 5 Apply a color map.
How to calculate NDVI and ndwi for Landsat 7?
However, NDBI calculation is simple and easy to derived. NDVI can be calculated by following formula. NDBI = (SWIR – NIR) / (SWIR + NIR) For Landsat 7 data, NDBI = (Band 5 – Band 4) / (Band 5 + Band 4) For Landsat 8 data, NDBI = (Band 6 – Band 5) / (Band 6 + Band 5) Also, the Normalize Difference Build-up Index value lies between -1 to +1.
When to use NDVI and ndwi for water bodies?
NDBI value for vegetation is low. Normalize Difference Water Index (NDWI) is use for the water bodies analysis. The index uses Green and Near infra-red bands of remote sensing images. The NDWI can enhance water information efficiently in most cases. It is sensitive to build-up land and result in over-estimated water bodies.
When to use normalized difference Water Index ( ndwi )?
Normalized Difference Water Index (NDWI): Normalize Difference Water Index (NDWI) is use for the water bodies analysis. The index uses Green and Near infra-red bands of remote sensing images. The NDWI can enhance water information efficiently in most cases.