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I've wrote this code for Sentinel-1 decible image. although it doesn't show any error but decible image contains many NaN values.

Code link: https://code.earthengine.google.com/0803e3f7e3518013e310f7d1c666acf9

var fall = ee.ImageCollection('COPERNICUS/S1_GRD')
.filterBounds(table)
.filterDate('2018-10-01','2019-01-01')
.filter(ee.Filter.listContains('transmitterReceiverPolarisation','VV'))
.filter(ee.Filter.equals('instrumentMode','IW'))
.select('VV')
.median()
.clip(table)
.focal_median(50,'square','meters')
.log10().multiply(10.0)
.rename('fall');

Map.addLayer(fall);
  • 2
    what doesn't work? – Ian Turton May 23 at 9:23
  • although it doesn't show any error but image result, is not correct. the most of the pixels have nan values! – Johny Astine May 23 at 10:30
  • 1
    please edit the question to update it with new information – Ian Turton May 23 at 10:32
  • ok, I did it. thanks – Johny Astine May 23 at 10:56
2

Just for remember:

What is the natural logarithm of a negative number? The natural logarithm function ln(x) is defined only for x>0. So the natural logarithm of a negative number is undefined.

Sentinel-1 product has mainly negative values (range -50 to 1), removing .log10():

enter image description here

Also, check Sentinel-1 SAR GRD product description:

Each scene was pre-processed with Sentinel-1 Toolbox using the following steps:

  1. Thermal noise removal

  2. Radiometric calibration

  3. Terrain correction using SRTM 30 or ASTER DEM for areas greater than 60 degrees latitude, where SRTM is not available. The final terrain corrected values are converted to decibels via log scaling (10*log10(x).

You are trying to pre-process data already pre-processed

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