sarproz-group

amplitude values

This topic contains 5 replies, has 3 voices, and was last updated by  periz 1 year, 5 months ago.

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  • #1257

    ivca-cz
    Participant

    Hello,

    I would like to ask in what units are the amplitude values. As these values (up to 4 for most of the area, high-amplitude points up to 30-40) do not seem to be the absolute values (expecting to 10^3, high-intensity points up to 10^8), neither the decibels (or decibels w.r.t. what?).

    Thank you, Ivana

  • #1261

    periz
    Keymaster

    Images are equalized via a simple normalization process.
    You need it to perform statistics on amplitude time series.
    The unit of amplitude is volt. But its value is useful only if compared to other values, not in an absolute way.
    If you could calibrate it by knowing the amplitude of a reference corner reflector,
    you could derive the RCS of targets (in sqm). I think you find it in my phd thesis.

  • #1361

    ivca-cz
    Participant

    Hello Daniele,

    could you please let us know the relation between original image intensity (in the SLCs) and the values got in “refl. map”?

    I need to compute sigma_0 and know how to do it from original SLC but these values are different.

    Thank you very much, Ivana

  • #1363

    periz
    Keymaster

    Hi Ivana,

    you raised a good point. We used to store the normalization constants many years ago, but we did not implement it when we included the SLC module. The image amplitude is normalized to have an average value equal to 1. You could further equalize the images using only stable targets. But the matter of fact is that at this moment the constant is not saved.
    We are including it in the todo list…
    d

  • #1659

    seppi-santiago
    Participant

    Hello Daniele,

    I’m interested in getting this information too. I exported the Synthetic Amplitude via the Time Series Module and would like know whether its values are the normalized ones you mention to Ivana.

    I enclose the created CSV file. As you see the values for the first date are always 0. Why? Is it the Synthetic Amplitude the correct parameter?

    Thanks,
    Santiago

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  • #1663

    periz
    Keymaster

    Hi Santiago,
    first of all, the Synthetic Amplitude (which you can plot using the view params module) is the amplitude generated from the DEM (showing the geometric distortions derived from the topography).
    Secondly, the parameter choice in the TS module is for displaying points with a color. So, used only in case you export a kml.
    Thirdly, the time series module exports deformation time series.
    If you want to export amplitude time series, I suggest you to use the small area module.
    At this moment we do not have a module for exporting amplitude time series for the full site.
    If this is what you need, we should discuss about it.
    d

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