Hello,
I am using the GEDI 2B product to derive forest height statistics in our study area in Colombian Amazon. I use only l2b_quality_flag = 1 data. I was comparing two variables: rh100 and height_bin0. I noticed there are in many cases quite significant difference. And on average, the height_bin0 values are 3 m higher than the rh100 values in our study area.
What is the difference between between these two variables? And which one do you recommend using?
Best regards,
Jukka
GEDI02_B height metrics
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jmiettinen
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LP DAACx - dgolon
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Re: GEDI02_B height metrics
Hi @jmiettinen I am having our data team look into this. Could you please let us know what your study area / study time period is or if there are any specific granules you are looking at where you are seeing this? If so, could you please let us know their IDs (ex: GEDI02_B_2023075201011_O24115_03_T08796_02_003_01_V002). Thanks -- Danielle
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jmiettinen
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Re: GEDI02_B height metrics
Thank you for the fast reply. I processed the last year of GEDI data (from Mar 2022 until the end). And our interest area is "min_lon": -75.0, "min_lat": -4.0, "max_lon": -69.4, "max_lat": 0.0. In this area, there were over half a million valid observations during the year. Here is one of the products as an example: GEDI02_B_2022262070651_O21346_04_T10135_02_003_01_V002.h5
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Re: GEDI02_B height metrics
Just an update on this, we have a question out to the GEDI Science Team. Once we hear back, we will follow up on this post.
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Re: GEDI02_B height metrics
Hi @jmiettinen,
For height, you should use rh metrics from the L2A product (rh100 in the L2B product is copied from L2A).
In terms of the difference between height_bin0 and rh100, please refer to the data dictionary:
https://lpdaac.usgs.gov/documents/980/gedi_l2b_dictionary_P003_v2.html
Note that “height_bin0” is defined as “Height of the first bin of the pgap_theta_z, relative to the ground.” pgap_theta_z is an 1D array similar to rx_waveform in L1B. The height of the first bin is at an arbitrary point along the shot path and is above the observed return signal start. It is included in L2B so that users can derive a height value for each sample in pgap_theta_z and should not be interpreted as canopy height.
For height, you should use rh metrics from the L2A product (rh100 in the L2B product is copied from L2A).
In terms of the difference between height_bin0 and rh100, please refer to the data dictionary:
https://lpdaac.usgs.gov/documents/980/gedi_l2b_dictionary_P003_v2.html
Note that “height_bin0” is defined as “Height of the first bin of the pgap_theta_z, relative to the ground.” pgap_theta_z is an 1D array similar to rx_waveform in L1B. The height of the first bin is at an arbitrary point along the shot path and is above the observed return signal start. It is included in L2B so that users can derive a height value for each sample in pgap_theta_z and should not be interpreted as canopy height.