Can't find selected_algorithm in L2A GEDI elevation and canopy height dataset

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alvioli
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Can't find selected_algorithm in L2A GEDI elevation and canopy height dataset

by alvioli » Sat Dec 31, 2022 4:00 pm America/New_York

I am trying to extract ground elevation data from L2A GEDI "elevation and canopy height" dataset.
I managed to extract different variables, mostly elev_lowetreturn_a[N], corresponding lon/lat coordinates, and quality flags. I can't seem to find a way to extract the variable selected_algorithm, which is supposed to tell me which [N] I should actually be using, if I am not wrong. Moreover, I don't know to select different beams from the dataset.

I have been using the gedi_to_vector.py python script, which seems pretty neat - described here:
https://medium.com/@abt0020/extracting-canopy-height-with-gedi-data-5af8c87df158

The typical command line I have been using is something like:
python gedi_to_vector.py ./ -variables [lon_lowestreturn_a1,lat_lowestreturn_a1,elev_highestreturn_a1,quality_flag_a1] -outFormat CSV
which should extract results for all of the eight beams; I mean, with no specification about which point correspond to which beam.

I do not care about the gedi_to_vector script - I can turn to whatever works to get what I need.

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LP DAAC - jwilson
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Re: Can't find selected_algorithm in L2A GEDI elevation and canopy height dataset

by LP DAAC - jwilson » Wed Jan 11, 2023 12:14 pm America/New_York

@alvioli,
We apologize for the delayed response. I have forwarded your inquiry to our Subject Matter Expert and will be in contact with the data provider. Once we receive a response, we will let you know.
Kind regards,
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Re: Can't find selected_algorithm in L2A GEDI elevation and canopy height dataset

by LP DAAC - dgolon » Mon Jan 30, 2023 10:54 am America/New_York

Hi @alvioli Here is what we heard back:

We recommend using the LP DAAC - Getting Started with GEDI L2A Version 2 Data in Python (usgs.gov)(https://lpdaac.usgs.gov/resources/e-learning/getting-started-gedi-l2a-version-2-data-python/) script. Although it is not command line executable it should yield similar results when walking through this tutorial. Fields will need to be changed but will give you a geojson file which then can be input into qGIS or ArcGIS. This tutorial does not explicitly extract the selected algorithm however, but future updates to the tutorial will include the steps to extract it.
The user guide for GEDI V2 data (GEDI02_UserGuide_V21.pdf (https://lpdaac.usgs.gov/documents/998/GEDI02_UserGuide_V21.pdf) on page 13 explains further elevation and height metrics for alternative algorithm settings in L2A. Also referenced in the user guide is the ATBD for GEDI Waveform Geolocation L1 & L2 Products (GEDI__WFGEO_ATBD_v1.0.pdf (https://lpdaac.usgs.gov/documents/579/GEDI__WFGEO_ATBD_v1.0.pdf), section 5 goes into additional details.

Thanks!
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Re: Can't find selected_algorithm in L2A GEDI elevation and canopy height dataset

by LP DAAC - afriesz » Mon Jan 30, 2023 1:20 pm America/New_York

Hey @alvioli ,

We recently made some updates to the GEDI tutorials found here: https://git.earthdata.nasa.gov/projects/LPDUR/repos/gedi-v2-tutorials/browse in response to your question. The output geojson files for the L2A and L2B tutorials should both include the selected_algorithm.

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