Sentinel-1 image decible in Google Earth Engine?

Question

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);

Answer 1

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():

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