Introduce variable/ Indices using landsat image
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International Centre for Integrated Mountain Development
Mountain Environment & Natural Resources’ Information System (MENRIS)
What is Image Index?
- Image Index is a “synthetic image layer” created from the existing bands of a multispectral image. This new layer often provides unique and valuable information not found in any of the other individual bands.
- Image index is a calculated results or generated product from satellite band/channels
- It is help to identify different land cover from mathematical definition .
Band/Channel of Satellite Image
There are different type of Band/ Channel
Following Band/Cannel are commonly used
Band 1 0.45 - 0.52µm (blue)Band 2 0.52 - 0.60µm (green)Band 3 0.63 - 0.69µm (red)Band 4 0.75 - 0.90µm (nir)Band 5 1.55 - 1.75µm (infra-red)Band 6 10.4 - 12.50µm (tir)Band 7 2.08 - 2.35µm (nir)Band 8 0.52 - 0.90µm (pan)
False color composite: (4,3,2)Vegetation appears in shades of red Urban areas are cyan blue, and soils vary from dark to light browns. Ice, snow and clouds are white or light cyan. Coniferous trees will appear darker red than hardwoods. This is a very popular band combination and is useful for vegetation studies, monitoring drainage and soil patterns and various stages of crop growth. Generally, deep red hues indicate broad leaf and/or healthier vegetation while lighter reds signify grasslands or sparsely vegetated areas. Densely populated urban areas are shown in light blue.
Natural color composite: (3,2,1) Ground features appear in colors similar to their appearance to the human visual system
Healthy vegetation is green, recently cleared fields are very light,
Unhealthy vegetation is brown and yellow
Roads are gray, and shorelines are white.
This band combination provides the most water penetration and superior sediment and bathymetric information.
It is also used for urban studies. Clouds and snow appear white and are difficult to distinguish.
Matural-like composite: (7,4,2)Healthy vegetation will be a bright green and can saturate in seasons of heavy growthGrasslands will appear green, pink areas represent barren soilOranges and browns represent sparsely vegetated areas. Dry vegetation will be orange and water will be blue. Sands, soils and minerals are highlighted in a multitude of colors. This band combination provides striking imagery for desert regions. Urban areas appear in varying shades of magenta. Grasslands appear as light green.
Composite: (4,5,1)Snow area will be pink
Healthy vegetation appears in shades of reds, browns, oranges and yellows.
Soils may be in greens and browns, urban features are white.
Clear, deep water will be very dark in this combination, if the water is shallow or contains sediments it would appear as shades of lighter blue.
This is not a good band combination for studying cultural features such as roads and runways.
Normalized difference vegetation index (NDVI)
Index values can range from -1.0 to 1.0, but vegetation values typically range between 0.1 and 0.7.
NDVI is related to vegetation is that healthy vegetation reflects very well in the near infrared part of the spectrum.
It can be seen from its mathematical definition that the NDVI of an area containing a dense vegetation canopy will tend to positive values (say 0.3 to 0.8) while clouds and snow fields will be characterized by negative values of this index.
Normalized Difference Vegetative Index (NDVI)
NDVI = (NIR - red) / (NIR + red)
NDVI (ETM+) = (Band 4 - Band 3) / (Band 4 + Band 3)
Free standing water (oceans, seas, lakes and rivers) which have a rather low reflectance in both spectral bands and thus result in very low positive or even slightly negative NDVI values,
soils which generally exhibit a near-infrared spectral reflectance somewhat larger than the red, and thus tend to also generate rather small positive NDVI values (say 0.1 to 0.2).
Difference Snow/Ice Index calculations are related to reflections different bands. Snow and ice have very high reflectance values in visible spectral bands (blue, green and red), but very low reflectance in mid-infrared band.
Normalized Difference Snow Index (NDSII)
The value is then normalized to the range -1<=NDVI<=1 to partially account for differences in illumination and surface slope. All the snow will carry positive value.
NDSII = (green – infra-red) / (green + infra-red)
(ETM+) NDSII = (Band 2 - Band 5) / (Band 2 + Band 5)
Land and Water Masks (LWM)
Index values can range from 0 to 255, but water values typically range between 0 to 50
Water Mask = infra-red) / (green + .0001) * 100(ETM+) Water Mask = Band 5) / (Band 2 + .0001) * 100
Modification of Normalized Difference Water Index (NDWI)
Index values can range from 0 to 255, but water values typically range between 130 to 255
NDWI=(NIR – infra-red) / (NIR + infra-red)(ETM+) NDWI = (Band 4 - Band 5) / (Band 4 + Band 5)
Green normalized difference vegetation index
Index values can range from 0 to 255, but vegetation values typically range between 150 to 255
GNDVI=(NIR - Green) ÷ (NIR + Green)(ETM+) GNDVI = (Band 4 - Band 2) / (Band 4 + Band 2)
Normalized Difference Moisture Index
Index values can range from –1 to +1 , but vegetation values typically range between 0 to 1
Soil Adjusted Vegetation Index (SAVI)
SAVI = (NIR - red) / (NIR + red)
NDVI (ETM+) = (1.5* ((Band 4 - Band 3) / (Band 4 + Band 3) +.05))