When to perform EAP?

Just to make explicitly clear when EAP procedure should be done?
I follow the standard way in processing SAR for interferogram - Split->Orbits->Cregistration->ESD…
I’m asking this since I’m in vicious circle - the EAP module says the EAP has been already preformed, while the Interferogram module says one of the products is not EAP corrected.

The pair I’d like to use is:

  1. S1A_IW_SLC__1SDV_20150127T043804_20150127T043832_004352_0054F2_C61E.zip
  2. S1A_IW_SLC__1SDV_20150912T043813_20150912T043840_007677_00AA81_1816.zip
    both downloaded from ASF.

Thank you.

Hi there

You must apply EAP correction to the images that has been processed with IPF < 243 (you can get this info in the metadata of the image). This processor is the one that generates the SLC and V243 and above already correct EAP elevation. Images processed before April 2015 usually requires EAP correction, so your image S1A_IW_SLC__1SDV_20150127T043804_20150127T043832_004352_0054F2_C61E.zip must be EAP corrected prior interferogram formation.

You have very detailed information about this in:



@Joaquin - Thank you for your reply. My question concerns usage of SNAP software - when should EAP be used.


Hello again Hriston:

Let´s see if this answer your question:

Top read should be your 20150127 image and Read(2) the 20150912 image. You can modify the later as you want (ESD, Topophase removal, etc…).


@Joaquin - Thank you!! I’ll try it and inform about the results.

you mean we shoud do eap phase correction and also coregistration with esd for those images?

@survivere13 I’d suggest to aplly EAP procedure after Split and Apply Orbit BEFORE co-registration

would you please take a look at this? is it true? should i use it just for 2015 and before 2015 images?

@survivere13 The graph you show is too heavy for ordinary desktop/laptop. I see you need to process three IWs at once, but most probably you will need a lot of memory (> 64GB RAM).
With regard to EAP it is at place. As far as I know EAP is needed for images from the interval Nov2014-Apr2015 so the graph you posted is too specific.
Moreover I found this:

Generally users do not need to run this operator if they do not need to review the azimuth shift values. They can run the S-1 Enhanced Spectral Diversity operator directly where the azimuth shift is estimated using EDS and used directly in the azimuth shift correction.

I hope if you explain your task the support from the forum users will be most topical.


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hi, thanks a lot for your explanation, i’m gonna study land subsidence using PSI method on a region which is in both IWs, my superviser asked me to do the process for whole image.
so what should I do? should I just split it step by step? I’m a bit worried I get confused about IWs!:confused:
thanks for EAP explanation, what about ESD? Is it necessary for all images or it’s for nov2014-apr2015 too?
I’m sorry i don’t have much information about steps

EAP is only for the images nov2014-apr2015

ESD is must for obtaining good interferogram (IF)

With regard to IWs - select only the ones you need e.g. 1-2 or 2-3, process separately and after filtering merge the IWs

I’m nit sure if you could apply PSI with SNAP - search the forum for the workaround. Please notice PSI is not trivial task and will take time.

Good luck!

thank you so much it was really helpful