sarproz-group

cumulative displacement isn't accuarte

This topic contains 3 replies, has 3 voices, and was last updated by  periz 2 years, 4 months ago.

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  • #991

    cnu_lee
    Participant

    Hi, Professor Daniele,

    The cumulative displacement value in DBF file of result are relative to the reference point. But I don’t know the cumulative displacement of reference point.So the value isn’t accurate?

    How to understand the value of cumulative displacement? Whether I should plus or minus a value to obtain the true displcement value?

    Thank you.

  • #993

    periz
    Keymaster

    the title of this post is pretty misleading.
    insar is relative, but it can still be accurate.
    so, deformation trend, time series, cumulative displacement and any other insar product are RELATIVE to a reference point.
    unless you know whether the ref. point is stable, your measurements will always be RELATIVE to it.
    the true displacement value does not exist (better: it exists, but you do not know it). in any case, you need to know what is the displacement relative to.

    • #1011

      seppi-santiago
      Participant

      Hello Daniele,

      I’ve tried to generate Cumulative Displacement files covering different periods of time, entering different dates in the Cumulative Displacement tool. However, when exporting to KML/KMZ I think I’m always getting the same file,as the initially generated for the complete temporal length. covered by mi images. Looking at the logfile it does not show any error when saving the CumDisp.mat file.

      Another question related to this, when exporting time series the displacement values (corresponding to each acquisition date )stored in the .csv file are calculated using the same polynomial coefficients in the Cumulative displacement tool?

      Thanks,
      S

  • #1013

    periz
    Keymaster

    yes, that is something to be tided up.
    Initially, the Cum Disp tool was generated to calculate it based on the estimated coefficients of a polynomial.
    Later on, I invented the smart tool, which is a non-parametric time series analysis.
    So, the Cum Disp tool is consistent with the rest of the results (and it calculates the proper things) only if you estimated a polynomial.
    However, I strongly suggest you to become familiar with the smart option, which is much more powerful.
    In such case, the Cum Disp is only calculated as a difference between the last and the first samples.
    We will generalize it and we will tidy up this matter when we will renew the time series exporting tool.

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