# How to estimate baseline

Hi,

I’m strongly want to know that how to estimate the baseline between master with each slave images before interferogram formation in order to continue inSAR?

Kindly provide the solution.

Cheers,
Boris.

You can do this in the InSAR Stack Overview operator.

Thanks appreciate all the help for a beginner like me in InSAR processing!

@ABraun: It seems wrong with my study,there is no interference fringe appear,why the coherence is so low .only because of Temp baseline is 24 and Coherence is .87?

Good luck and let us know,thank you

yes, the coherence of the InSAR Stack tool is only a theoretical one. It does not reflect decorrelation based on changes at the earth’s surface.
If there is much vegetation in your study area, phase decorrelation is a problem.

Excellent, thank you for the detailed info.
as I am trying to create a DEM,Why of my histgram is full of fine lines compare to yours are smooth,After applying the steps below;
1.Open product
2.S1 TOPS Coregistration with ESD
3,Creating Interferogram

these lines are just thresholds in the color manipulation tab. They do not really interrupt the histogram. For DEM genration, more important is your perpendicular baseline.

Great, thanks for the quick response.
yes ,I’d to interrupt the progress til find a pair of images with suitable perpendicular baseline and short temproal baseline

for DEM generation, the ideal perpendicular baseline is 150-300 meters. You can use the ASF Baseline tool to find suitable image pairs (I described it here: How to prepare Sentinel-1 images stack for PSI/SBAS in SNAP)

Thank you for the detailed info.I’ll be petient in finding a suitable image pairs first!

Sorry to disturb you again,@ABraun,I 'm confused about how to set the parameters in multi-looking below in making DEM, I’ve follow some instructions while the result have a big difference.one said I should choose i and q bands while others are phase and coh. or i and q and coh. bands,why?

if you want to multi-look after interferogram you select Phase (and coh if you need it later), but if you want to multi-look the complex parts of the radar image, you at best select no source band.

In both cases, you are fine without selecting any source band, because this takes all available and transfers them to the target product.

HI, i want to implement three pass Dinsar,following steps below:

1. 2 SLC befor event;1 SLC after event.
2. creat to stack separately.
3. interferogram formation(check ‘subtract topographic phase’)、debust 、
4. band math:Phase subtration
5. flt, unWrap,phase to displacement ,TC.
6. deformation map
Are these steps necessary and in the right order?
Thanks,
Boris

Dear ABraun, ‘no appropriate product reader found’ appears when I turn on my lap this morning,though everything is ok last night when I turned of the lap.Then, I reinstall my snap7 and update all plugins .message appers again.Can you help me?

this is normal. The basic installation of SNAP comes without the intermediate updates. Once you re-install SNAP from scratch, all updates have to be installed additionally.