sarproz-group

Height and Relative Height from ground

  • This topic has 14 replies, 2 voices, and was last updated 1 year ago by antig.
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    • #3376
      antig
      Participant

      I am still left confused that mean H estimation in sarproz. does it is dem or aditional height form ext.Dem or height difference from reference point. For example in H.jpg major H estimates are negative. I calculated APS result was fine. Calculate Sparse points seems also ok. Even output seems ok and logigal. Othe only thing that disturbs are “Height relative from ground” are almost all points negative values (result.jpg). I dealing with Senitnel data

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    • #3379
      antig
      Participant

      Seems like all set is turned upside down. Points that are close to ground are smaller negative values than points that are on top of buildings. Heights numbers, if take absolute value, seems also ok.

    • #3383
      periz
      Keymaster

      1. Height of point P is relative to the reference point Ref
      2. Final Height = External DEM Height + Residual Height
      3. The way in which things are estimated depends on your choices: if you remove or not the external DEM height, if you use multi-master differential interferograms or simple star (single master) interferograms, if you take your estimation from the APS processing module (integrated in space) or from the MISP (with single ref point), and so on.
      You give no details about the steps you followed and in particular you do not show the external DEM height.
      So, plot and past the ext DEM height, and tell us more about processing steps and ref point location.
      best

    • #3394
      antig
      Participant

      I use single star graph with APS. Coherence is good. APS is calculated at Amlitude stabiliti index form valuse >0.75. Test coherence is good. So everything should be ok. Ext. DEM model is used and its SRTM.

      I calculated other orbit to (different direction). There are all hights ok. If I look both dataset, there are diffrences in defermation, but not crusial. Only thing is that one data sets are heights from ground negative other positive. Negative heights geocoding is shifted fiew pixels, but its understandable because reference surface is wrong.

    • #3396
      periz
      Keymaster

      so, is it a problem of the reference point?

    • #3397
      antig
      Participant

      I tried diffrent reference points it does not helped.
      I changed dem global-> local (ALS based 10 m res). helped so that -29 m become -27 . So practicaly nothing.

      Stuck as jeep in mud. Wheels spinnig but no result 🙂

    • #3399
      periz
      Keymaster

      can u attach the ext DEM in SAR coordinates?

      • #3402
        antig
        Participant

        Yes I did

    • #3400
      antig
      Participant

      I calculated also Small area with no APS. Result is same negative height and height from ground are negative ~20m

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    • #3403
      periz
      Keymaster

      can u attach the ext DEM in SAR coordinates? (third and last time)

    • #3404
      antig
      Participant

      yes

    • #3406
      antig
      Participant

      Hi

      I had made some progress. I changed APS Graph from delanuay to autoflowers(clusters). Result is that some points have already positive heights :). But they are minor.

    • #3571
      antig
      Participant

      Hi again
      I have realy hard to understand thats happening.
      i have stack of sentinel 1 images and I mada Small area PSInsar analysis. Estimating booth LT and H.
      In result analysis may seen that major H residuals has positive values (out.png).As I understood correctly, then H should be Ex.Dem+residual H. So Relative height from ground should be H-ext.dem. But as seen in result, major points has negative Height from ground values (height from ground.jpg). Cohherence is good >0.8 and no APS is estimated (Small area).

      Any help is good for clear thats happening.

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    • #3574
      periz
      Keymaster

      can u attach the ext DEM in SAR coordinates? (fourth time)

    • #3576
      antig
      Participant

      Sry yes both cases are done that.

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