Hi
I have a question
I try this graph without spekle filter
it gives me just Sigma0_VV !
shouldn’t it give me amplitude or somethings like that?
amplitude information is converted to Sigma0 in the calibration module.
Thank you ABraun
there is no deference between Sigma0 and amplitude?
how about gamma0 and beta0?
for change detection I should select which band?
you should actually understand the difference between amplitude and Sigma0 when you are working with radar data 
Change detection should be performed ony with calibrated information to exclude the influence on sensor specifics at the time of image acuisition.
yes I know but for doing change detection at first we should transform slc to grd but when I do it, I don’t get amplitude data
how can I get it?
amplitude is your backscatter before calibration. What you need for change detection is a calibrated signal, such as Sigma0.
You could as well make change detection with SLC data and later on convert your data to ground range. This prevents detection of ‘false changes’ due to resampling of your data.
Can you guide me how to do it step by step?, please!
I want to work in urban area
I can’t do that, sorry.
It is basically calibrating and co-registering SLC images and then looking for changes. But it requires a bit of willingness to learn new things from your side.
I have collected a few documents which help you to acces the world of SAR in another post. The topic initially dealt with interferometry and crop monitoring but the same applies to change detection.
Good luck!
Thank you so much!
I do this step to preprocess my SLC data and convert to GRD for change detection in urban area without any decrease in resolution on 2 images with exactly 1 year in between
Does anyone think it is true?
1- at first I use S-1 TOPS split to reduce amount of computation and select area of interest
2- Apply orbit file
3- Radiometric > calibrate (here I don’t know in processing parameter select either save as complex output or output sigma0 beta0 gamma0. because when I select complex output in further step SNAP says it shouldn’t be complex)
4- S-1 Thermal noise removal
5- S-1 TOPS deburst
6- Geometric> Slant range to ground range
7- make a graph that includes just { read> GRD-post> write }
is it appropriate after this step I do :
SAR application > urban area> speckle divergence
Radiometric> radiometric terrain flattening
Geometric > terrain correction> Range doppler terrain correction
how about Ellipsoid correction
I am so thankful if every one can help me
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Is the workflow correct for GRD data processing? I attended an ESA workshop last year and we were asked to perform multilooking on GRD data (ftp://ftp.itc.nl/pub/dragon4/SAR/D1SP1-S1TBXIntro-MFoumelis/Dragon_2017_D1SP1_Cookbook_SNAP.pdf)
Also, does this process also account for the topographic variations in the data or do I need to perform some other step (such as terrain flattening) for that? If yes, then my final product will be gamma not (instead of sigma not). So is it ok to perform the analysis with gamma values?
Which order should ThermalNoiseReduction and Calibration be run and if it makes any difference then what are the difference(s)?
Earlier in this thread (see above) lveci’s graph shows Cal>TNR but SLC to GRD within SNAP runs them the other way round.
Thank you
It should not make any difference in the results. That being said, sometimes users find a new creative ordering of the operators that triggers errors in some cases. Therefore we are defining a set of “recommended processing graphs” to simplify finding a working solution.
When you say “we are defining …” I guess that implies you are in the process of doing this - unless you are referring to the SLC to GRD graph that already exists within the Radar tools menu.
But if a set of “recommended processing graphs” exists elsewhere or will do in the near future please point me towards them.
Many thanks for the very prompt reply!
story of my life
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Dear Andy I’d like to comeback to this point, Applying speckel divergence on GRD, Do you have any suggestions on the following approach?
Thermal noise removal--------->apply orbit --------->calibration to sigma0--------->apply speckel divergence,
The other question is, which window do you suggest in urban approach in speckel divergence?
I don’t have experience in tuning this operator, sorry. I would systematically increase and reduce it to see which window size is most suitable for your case.
Hello. I will very appreciated if somebody helps. How from GDR make SLC or how with GDR from S1A make coregistration and interforogram or how from .h5 CosmoSkymed make interferogram. I often have an errors in difrent stages. Can anybody prompt me clear algoritms with such files.
you can turn SLC into GRD products but not in reverse.
sir, can you please explain how to convert SLC TO GRD.