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Emissivity calculation from Sobrino's method

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Hey everyone,


While calculation emissivity from NDVI index using Sobrino's method, it is clear what we have to do when NDVI is greater than 0.2. But when NDVI is less than 0.2, we are given an equation a + b®. where a and b are regression coefficients and R is the reflectivity. R can be calculated easily. How do we estimate or select the values of a and b? My project area also has water body which has a negative NDVI value. Please help!

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If NDVI values are lower that 0 (-0.1 to -1) we have water bodies. The emissivity value for water is 0.995.


So, I think that the NDVI threshold should look like this:


  • if NDVI is under 0 (negative values), then we have water > emissivity for water is 0.995
  • if NDVI is between 0 and 0.2, then we have bare soil > emissivity for bare soil is 0.97
  • if NDVI is > 0.5, then we have vegetation > emissivity for vegetation is 0.99
  • if NDVI is between the values 0.2 and 0.5 ( 0.2 NDVI 0.5), then we have a mixture of bare soil and vegetation > emissivity is calculated by the equation of Sobrino method
Edited by Arhanghelul
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