I have come across many indices from the internet to calculate Built-up index using LANDSAT 8 imagery. I am not satisfied with any of those indices as it is taking water and crop lands as built-up.
I am in serious need of calculating this index.
Can someone please guide me to calculate this index?
You may want to look into applying a water-mask during the preprocessing step to anticipate confusion of built-up areas with water.
I wanted to ask if the croplands the get confused with built-up areas are bare croplands or covered (vegetation)?
In both cases, I think including time series would benefit your application to account for vegetation dynamics and possibly also mask it out efficiently.
I am extremely thankful for your kind attention and reply sir.
May i get a clarity on how to apply this water- mask.
The croplands are covered ones with some kind of vegetation on it.
Dear Sankalp
For water-mask. you have to extract first water bodies. This you can do by Normalized Water Index (NDWI) formula :
NDWI= (Green- NIR)/(Green+ NIR) for Landsat 8:
NDWI= (B3 – B5) / (B3 + B5)
Reclassify NDWI into two classes. Then convert it into polygon features. After that Select water body shape files and save for mask.
Best wishes,
Dr. Indra Prakash
Dear Prakash Sir
Thank you for kind attention and reply.
I followed your step till selecting water body shape files.
May i know the further processes to be done. Hope u reply Sir.
Dear Sankalp,
You have to save water body shape file. If you don't know how to mask, then you can simply clip the image with water body shape file. Remaining image will be without water body. Then you can do built up index analysis.
Best wishes
In continuation to my earlier reply, for clipping the area of your interest (without water body)you have to draw polygon covering your image. Then use erase tool to remove water body area. remaining shape file will have holes. Clip your image from that file. you will get area of your interest for the analysis without water body.
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