ground identification using GEDI waveform

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deace
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ground identification using GEDI waveform

by deace » Tue Apr 04, 2023 7:30 am America/New_York

How can I reproduce the RH metric given in the L2A product using GEDI raw waveform(especially deciding the lowest mode the same way as the L2A product has done)?
[question description]
I followed the Algorithm Theoretical Basis Document (ATBD) for GEDI Transmit and Receive Waveform Processing for L1 and L2 Products document and noticed that the lowest mode(referred to the ground) is determined from a zero crossing point of the first derivative of the de-noised waveform. However, I found that in some cases the lowest mode using this method is more likely to refer to the noise with low amplitude/intensity.
I also noted that the candidate lowest mode could be overruled in subsequent processing mentioned in the ATBD section 4.3.6 but no more detail about how this subsequent processing is performed. So I want to turn to the forum for helps with any detailed information about related algorithm.In the GEDI L2A product dictionary, Labels including amp_thresh,botlocdist_limit,ampval_limit,cumulative_energy_thresh, etc are all marked with "the final ground return pulse selection parameter" in the description. Are these parameters utilized to determine the lowest mode?
[more detail]
the GEDI ATBD file is obtained from the links:
https://gedi.umd.edu/data/documents/
Thank in advance for your expert knowledge and quick feedback.

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LP DAAC - dgolon
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Re: ground identification using GEDI waveform

by LP DAAC - dgolon » Tue Apr 04, 2023 10:27 am America/New_York

Hello - I have passed your question along to our science team. We will write back when we have more information.
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Re: ground identification using GEDI waveform

by LP DAAC - dgolon » Tue Apr 11, 2023 9:36 am America/New_York

Hi @deace the science team would like to know what you are trying to achieve, that will help them understand your question more. They did mention the RH metric is given in the L2A product from the raw form data. Thanks
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deace
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Re: ground identification using GEDI waveform

by deace » Tue Apr 11, 2023 10:20 pm America/New_York

LP DAAC - dgolon wrote:
> Hi @deace the science team would like to know what you
> are trying to achieve, that will help them understand your question more.
> They did mention the RH metric is given in the L2A product from the raw
> form data. Thanks
I am trying to reproduce the results using the L1B product so that I can compare them with the one given in the L2A product.
To be more specific, I am trying to make a change detection analysis using ICESat-1 and GEDI data based on the RH metric. The RH metric is only adopted in GEDI and LVIS products, so I have to recalculate the RH metric followed by the GEDI algorithm theoretical basis using the ICESat-1 waveform. That is why I want to know the detail as much as possible about the algorithm and how to calculate it rather than the RH metric itself given in the L2A product. It is important to me.
Thanks!

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Re: ground identification using GEDI waveform

by LP DAAC - lien » Wed May 03, 2023 9:13 am America/New_York

Hello,
The GEDI science team responded:

There is sufficient information in the ATBD to derive an RH metric, but unfortunately no code examples. The L2A code is not yet publicly available, but derivation of RH metrics from simulated GEDI waveforms is available in the GEDI simulator (https://bitbucket.org/StevenHancock/gedisimulator/src/master/).
Please let us know if we can be of more assistance.
Thanks,
LPDAAC Team.

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