# Backscatter values extracted and make regression analysis

Dear all,
How can i backscatter values from Sentinel-1 A extracted from the image & The AGB at the sample plots on the ground was correlated with the corresponding image backscatter values using linear

method.
How can i make this type of graph( from the picture 2)?
Thanks all…

using “ggplot2” package in R

sir,

https://stats.stackexchange.com/questions/30975/how-to-add-non-linear-trend-line-to-a-scatter-plot-in-rscatter plot with fitting line using ggplot2 in R.txt (1.6 KB)
I upload an example for you and about how to add the fitting line to scatter plot there are a lot of resource in stackoverflow(https://stackoverflow.com/). you could search and find the answer.

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I am a girl, OK?

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Sorry mam…

But how can i extracted backscatter values form the Sentinel image?

i am a new member of group and i am very happy to participate, also i don’t know to manage english very i just try, is it a problem?

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If your English is not perfect it is not a problem. We try to guess what you are saying
And if something is not clear we will ask you.
So, welcome in the SNAP community!

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Thank you very much.

Did you ever find out how to extract backscatter values from S1?

you can use the pin manager for this.

Let me explore that. Thanks

I would be interested in the study where these graphs are used.

You can try the Regression Plot in the toolbar where linear, log and exponential regressions are performed between the two bands you selected.

You can stack bands of one location (of multiple products separate polarization!!!) and calculate slope and intercept values for each pixel via BandMaths, this can produce a new product of the area with these parameters.

Slope and intercept can be than used for linear regression or the other way around.

Here is a chapter of my work at internship should you achieve to get to the stack of [db], terrain-corrected backscatter values, it should help to build the BandMaths:

Well if you manage it congratulations, until then good luck.

Petr

if you have the GPS point of sample plots on the ground, you could extract the backscatter coefficient based on that. In addition, maybe you need some tutorial about SNAP. And if you used ENVI, maybe you just export the processing image to a TIF and extract the back scatter value in ENVI.

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I have a stack of 30 images and I have a point shape file overlaid on it. How can extract the average backscatter values from those points with a 3x3 window size?

wouldn’t this be easier with the zonal statistics tool of QGIS, for example?

Hi, weishao,

I am interested with this issue.
So, I have extracted the backscatter value in envi by using NRCS sigma Naught. Anyway i used alos palsar data. It was extracted, but I cannot differentiate the backscatter number like I have done in sentinel 2 toolbox or snap. In those two I can make regresion linear by indicating the backscatter value. But I cannot do that in envi. Do you know how to present the bacsckatter value in envi and make it a graph afterwards?
Thank you