Soil Moisture Mapping Using S1_SLC product and s1tx

Andiray · May 20, 2019, 9:10am

Sir, how to kind of tools to make this picture?

graphic of backscatter and moisture

ABraun · May 20, 2019, 10:13am

you need a shapefile with attributes (moisture), import it in SNAP and use the correlative plot view.

Andiray · May 20, 2019, 12:33pm

how can i get shapefile sir?

ABraun · May 20, 2019, 12:54pm

measure soil moisture in your study area at the time when the image is acquired and locate the meastrements by a GPS device, for example.

Andiray · May 20, 2019, 12:59pm

Yes sir, I have these data
But i don’t know how to import these data to SNAP

hriston_bg · May 20, 2019, 1:18pm

Why not try this one - https://land.copernicus.eu/global/themes/Vegetation . This is verified product.

For SHP files import just do File->Import->VectorData->ESRI Shapefile

Andiray · May 20, 2019, 1:41pm

Hi @hriston_bg,
But when I search Surface Soil Moisture, I don’t find my study area because Spatial information is only in Europe

Andiray · May 20, 2019, 1:42pm

Hi @ABraun, how to use the correlative plot?

hriston_bg · May 20, 2019, 1:44pm

@Andiray I didn’t know that your area is outside EU. Sorry.

Andiray · May 20, 2019, 1:46pm

Hi @hriston_bg, thanks for your response.

hriston_bg · May 20, 2019, 1:50pm

@Andiray You may try Vegetation Condition Index as a proxy for SM.
The global product is here - https://land.copernicus.eu/global/products/vci

ABraun · May 20, 2019, 5:19pm

First you need a shapefile with numerical values (hoehe_cm in my case)

Load it into SNAP and overlay it with your SAR data

Then open the correlative plot view

Select the point shapefile and the attribute and correlate the raster values with the point information

Andiray · May 21, 2019, 1:38am

Hi @ABraun, how to make this shapefile? I only have ground data but I don’t know how to make it to shapefile.
I have coordinate point and value of soil moisture in ground data. I’m so sorry. I don’t have basic in SNAP

Thanks

ABraun · May 21, 2019, 4:55am

SNAP can import csv files when they are formatted correctly.
If not, load the coordinates (and moisture attribute) in a GIS and export it as a shapefile. There are lots of tutorials on this around.

Andiray · May 21, 2019, 5:01am

Okay sir @ABraun, I will learn about it

ABraun · May 21, 2019, 7:17am

Import of CSV files into QGIS: https://www.qgistutorials.com/en/docs/importing_spreadsheets_csv.html

Import of CSV files into SNAP: Import CSV File

Andiray · May 22, 2019, 4:06am

I have correlative plot now.
%20Correlative%20VV

whether this graph is true to soil moisture validation?

Andiray · May 22, 2019, 4:10am

My step backscatter is:

Multilooking (4:1)
Calibration: Sigma 0
Speckle Filter : Gamma Map
Terrain Correction

Does it only at this step? Shouldn’t I find its polarimetric decomposition?

Regards

ABraun · May 22, 2019, 4:39am

R²=0.17 means that you can currently only explain 17% of the variations of both variables by the each other. For statistically valid predictions you need probably more measurements and higher R² (0.5 and above).

If you have the chance for polarimetric decomposition, you can correlate the moisture with new rasters and see if their predictive value is higher. But Sentinel-1 is dual-pol only.

Andiray · May 22, 2019, 4:49am

What kind of new raster can i use sir?

Can’t I use sentinel 1 _SLC for calculate Polarimetric Decompotion?
Apply Orbit file>>Calibrate>>Tops Deburst>>H/A dual deccomposition.