sarproz-group

Ramp

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This topic contains 9 replies, has 3 voices, and was last updated by  periz 1 year, 8 months ago.

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  • #1456

    bahari
    Participant

    Dear all,
    I am processing sentinel data, I see the RAMP effect in the interferograms. How can I remove this effect? can I use “Residual fringes estimation and removal” or I can remove it in next steps e.g., in ‘Multi image InSAR processing”.
    Please help me.!

    thank you
    Nader

  • #1457

    periz
    Keymaster

    hi Nader,

    as mentioned by Yuxiao in a previous topic, there could be several reasons for having a ramp on an interferogram.
    E.g. orbital inaccuracies, coregistration problems, atmospheric artifacts and so on.
    Yuxiao is checking it because the Sentinel processing still deserves some extra care.
    Generally speaking, forgetting for a moment that you are dealing with Sentinel, as you said you have several options in Sarproz for removing ramps.
    One is residual fringes estimation and removal. That is removing linear artifact directly from the interferogram.
    An other option is to remove it as if it would be atmosphere, using the APS module. Finally, should this ramps affect the final estimated parameters, you can remove them after the MISP processing. All these options have pros and cons, depending on your particular case at hand.
    For giving you a suggestion, we should at least see the fringes
    bye

  • #1459

    Yuxiao
    Moderator

    Hi Dear Nader,

    Yes first we should at least see the fringes.

    In the second place, as said in the previous topic, It would be great for you to send me you master image’s file name (or date, but file name preferred), the image pairs (same as master image) that has ramps, and the range (coordinates, samples and lines) you set for your area so that I can investigate your case.

    Yuxiao

  • #1480

    bahari
    Participant

    Dear Yuxiao,

    For testing my results: what method can you introduce? how you can help me in this check?
    Nader

    • #1481

      Yuxiao
      Moderator

      Hi Nader,

      Dr. Perissin has already introduced you two methods in the post above. If you can also post your interferograms with fringes on to the forum we can help you by taking a look and giving suggestions.

      Yuxiao

  • #1482

    bahari
    Participant

    Dear Yuxiao,
    Please inform me on the files that I must send. (the files and their formats)

    Nader

    • #1483

      Yuxiao
      Moderator

      your interferograms. screenshot them.

  • #1487

    bahari
    Participant

    thank you,
    please see attachment
    Nader

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  • #1490

    bahari
    Participant

    Dear all,
    Who can lead me in next step. As I sent the fringes, there is good fringe in this step (with some ramp), but I don’t know why I can receive good results as displacement?

    Best regards
    Nader

  • #1491

    periz
    Keymaster

    Hi Nader,

    yes, there are some residual fringes, when Yuxiao will have time he will improve his code.
    In the meanwhile, as previously said, you can still process your data. There are several ways to remove or at least reduce spurious fringes.
    The first thing to do is using the residual fringes estimation and removal module: did you do it? afterward process again your interferograms and check them. linear ramps should be removed.
    then, you can carry out a multi-temporal analysis. How many images do you have? set the images graph to STAR and follow the steps described by Timo for the APS processing.
    dp

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