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Using the script available in this forum (belowlink), I tried for terrain correction (flattening) of Sentinel 1 images

Getting local incidence angle from Sentinel-1 GRD image collection in Google Earth Engine

Here is my working script.

https://code.earthengine.google.com/0a0ae5e730afd766d0c2eb4c4a07c937

Unfortunately, why the resulted gamma0dB is all white?

Could someone look at above link and solve it?

I really want to return terrain corrected (flattened) gamma0dB.

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1 Answer 1

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You can calculate gamma0 like this:

function toGamma0(image) {
  var gamma0 = image.expression('i - 10 * log10(cos(angle * pi / 180))', {
    i: image.select(['VV', 'VH']),
    angle: image.select('angle'),
    pi: Math.PI
  })
  return image.addBands(gamma0, null, true)  
}

https://code.earthengine.google.com/33e9cffee06f27b92b86e15b713a17cc

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