hello , as i am interested in calculating soil moisture from sentinal 1 data , i directly downloaded sar data from EO browser, as i am not getting how to convert backscater coefficient to %
Please take a look at this thread, soil moisture issue is well discussed, also give a glance to the article has been mentioned within the first post,
Thank you soo much for the reply sir i wii go through the steps
I am not doing any ground moisture content test as i am interested in detecting the percentage change in the moisture from month to month for 2 years, so how can i interpret the sigma0_vv_db data into moisture percentage, i am getting the values from 0 to 1.i have the monthly sentinal data for past 2 years.
There is no direct relationship between soil moisture and backscatter intensity. You first have to eliminate the impact of roughness and other factors by field measurements or long time series.
I think this one is essential: Soil moisture identification -Sentinel
Thank you so much for your guidance sir , as i am trying to collect the ground data and also i did change detection by subtracting the before monsoon data to after monsoon data as a result i am getting the variation in the moisture scale interms of pixel value.
Hello sir as i got the ground soil data of 30 training points from theta probe in terms of soil moisture % and i tried to correlate with the sentinal 1 data VV(bd) , i am getting zero corellation. please help me in this as i am confused
you have to remark that moisture is just one factor contributing to backscatter intensity. It also depends on roughness and vegetation cover of the surfaces which, as I expect in your case, superimpose the variation of the moisture.
Were the images acquired at the same time as the field data was collected?
@johngan has outlined this topic quite nicely: Soil moisture identification -Sentinel
You have the advantage that you have measurements, but the ambiguity of backscatter intensity remains a problem.
Thank u for the reply sir, yes sir the image is of same data as of ground data taken.
Interesting study, recently published:
Thank you for the paper sir.
Great example on the impact of soil moisture on SAR backcatter:
Hello sir , my VV (db) values of sentinal 1 is ranging in between 0 to 1 for all the 30 watersheds for different seasons , is it correct or my procesing is going somwhere wrong, as i go through different research papers the values are in negative. Please guide me in this
initially, calibrated SAR backscatter is scaled so that 1 represents a fully isotropic scatterer.
However, as most of the values range between 0. and 0.1, the data is translated into log-scale. You can to this by right-clicking the raster and selecting “Convert to/from dB”
Then you will have values ranging between -40 and +5 (roughly) as used in many studies.
Some more details on this: Classification Sentinel-1 problems with MaxVer
Thank you so much sir
values are ranging between -24 to +3
that is fine and within the expected range
thank you soo much sir