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I am working on bamboo distribution mapping using Sentinel-2 and Landsat-8 based on Bamboo index on ArcMap. The formula used is i.e. (BI) = (NDVI-SI)/(NDVI+SI); Where NDVI equals Normalized Difference Vegetation Index and SI equals soil Moisture Index.

I created a Bamboo Index map using both Sentinel-2 and Landsat-8; however, the pixel value for Bamboo coordinates of same point in Landsat-8 and Sentinel-2 is different; why does this happens? Moreover, the Bamboo index value is far greater than 1 in some of the bamboo coordinates. How to solve this issue?

Info: - Formula with band combination that I used for Bamboo index is as shown: - (BI) = (NDVI-SI)/(NDVI+SI)

For landsat-8:- SI = (NIR-SWIR)/(NIR+SWIR) = (Band5-Band6)/(Band5+Band6) & NDVI= (Band5-Band4)/(Band5+Band4)

For Sentinel -2:- SI = (NIR-SWIR)/(NIR+SWIR) = (Band 8- Band 11) / (Band 8+ Band 11) & NDVI= (Band8-Band4)/(Band8+Band4)

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There are 2 reasons why they would be different.

  1. They are different sensors with different hardware, spectral resolutions, spatial resolutions, and processing algorithms.
  2. The imagery are from different dates and times, reflecting differences in atmospheric and on the ground conditions.

To use Sentinel2 and Landsat together you can use the Harmonized Landsat Sentinel data product. This addresses most of the differences in #1 above, but not #2.

For index values greater than 1 a common problem is not applying the correct scaling factor to the original data. Sentinel2 data comes in the range 0-10000 and must be divided by 10000 to get reflectance, then you calculate the indexes. Landsat has some more complicated scaling you must do before calculating indexes.

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  • Can you please simplify it. Actually, I wasn't aware about it. How can I use this correction factor for NDVI and Soil Moisture Index in Landsat-8 and Sentinel-2.
    – Pushkar
    Jul 2, 2023 at 16:16
  • Be also aware that recent Sentinel-2 data have an offset in addition to the 10k scaling. See processing baseline 4.00 here: sentinel.esa.int/web/sentinel/technical-guides/sentinel-2-msi/…
    – remi.braun
    Jul 5, 2023 at 9:33

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