Query about GEDI time quantum

Use this Forum to find information on, or ask a question about, NASA Earth Science data.
Post Reply
deace
Posts: 7
Joined: Sun Jun 26, 2022 6:01 am America/New_York
Answers: 0

Query about GEDI time quantum

by deace » Sun Aug 07, 2022 9:25 am America/New_York

Is there exists GEDI campaign table(equivalent to ICESAT-1 which about 91 days for one campaign) so that I could know how to choose time quantum so that it could covered global forest/terrain .If not ,any time quantum for suggestions. Thanks so much for any
information!

Tags:

LP DAAC - jwilson
User Services
User Services
Posts: 199
Joined: Mon Sep 30, 2019 12:39 pm America/New_York
Answers: 1
Has thanked: 8 times

Re: Query about GEDI time quantum

by LP DAAC - jwilson » Tue Aug 16, 2022 1:34 pm America/New_York

Hi @deace ,
We have forwarded your question to our subject matter expert for further assistance.

LP DAAC - afriesz
Subject Matter Expert
Subject Matter Expert
Posts: 35
Joined: Tue Nov 12, 2019 4:02 pm America/New_York
Answers: 0

Re: Query about GEDI time quantum

by LP DAAC - afriesz » Wed Aug 31, 2022 8:55 am America/New_York

@deace ,

It is not clear to me what you’re asking for exactly. GEDI continuously collects lidar samples globally from the International Space Station. If you’re trying to find and access data that spatially and temporally intersect with you research parameters, I would recommend using Earthdata Search (https://search.earthdata.nasa.gov/search) to do this. From there, you can specify an area of interest, a temporal range, and the specific GEDI data product you wish to query against. If this is not what you are looking for, please supply us with some more details regarding what you are accomplish. I’m not familiar with the ICESAT-1 campaign table. Would you be able to provide a link to that resource?

deace
Posts: 7
Joined: Sun Jun 26, 2022 6:01 am America/New_York
Answers: 0

Re: Query about GEDI time quantum

by deace » Sat Sep 24, 2022 12:37 am America/New_York

equivalent to revisit time

LP DAAC - afriesz
Subject Matter Expert
Subject Matter Expert
Posts: 35
Joined: Tue Nov 12, 2019 4:02 pm America/New_York
Answers: 0

Re: Query about GEDI time quantum

by LP DAAC - afriesz » Tue Nov 22, 2022 10:55 am America/New_York

@deace,

Would you be able to share a link to the ICESAT-1 campaign table? I'm curious what it looks like. I don't think there is a 'table' containing the revisit intervals. Is there any reason why Earthdata Search doesn't at least get you partially there? You can search for you area of interest using the Earthdata Search interface to generate a list of scenes through time that you can download. You could then use the python scripts here: https://git.earthdata.nasa.gov/projects/LPDUR/repos/gedi-v2-tutorials/browse to identify the shots you are interested in and process them.

deace
Posts: 7
Joined: Sun Jun 26, 2022 6:01 am America/New_York
Answers: 0

Re: Query about GEDI time quantum

by deace » Thu Dec 22, 2022 4:06 am America/New_York

LP DAAC - afriesz wrote:
> @deace,
>
> Would you be able to share a link to the ICESAT-1 campaign table? I'm
> curious what it looks like. I don't think there is a 'table' containing the
> revisit intervals. Is there any reason why Earthdata Search doesn't at
> least get you partially there? You can search for you area of interest
> using the Earthdata Search interface to generate a list of scenes through
> time that you can download. You could then use the python scripts here:
> [url]https://git.earthdata.nasa.gov/projects/LPDUR/repos/gedi-v2-tutorials/browse[/url]
> to identify the shots you are interested in and process them.

with 33–56-day campaigns, roughly each four months the ICESat/GLAS collected full-waveform records with near global coverage.So how can i decide the temporal settings when i want nearly global coverage GEDI data?(one month,6 months or one year ?for example)because when i download gedi data within the single month,i find large rhombus-shape gap bewteen the satellite tracks,thats means many area within my ROI lack of those observations .
looking forward to your Suggestions.
THANKS!

LP DAAC - afriesz
Subject Matter Expert
Subject Matter Expert
Posts: 35
Joined: Tue Nov 12, 2019 4:02 pm America/New_York
Answers: 0

Re: Query about GEDI time quantum

by LP DAAC - afriesz » Tue Dec 27, 2022 4:51 pm America/New_York

@deace ,

The areas of no observations, or the ‘rhombus-shape’, you are seeing is a result of a couple things (probably more, but I’ll mention the things I know about). The first being the ISS orbit and the second being the altitude of the ISS. The ISS has a precessing orbit and not a polar orbiting one. This video has a pretty good depiction of the ISS orbit: https://www.youtube.com/watch?v=wxgrxvAKpTo. The precessing orbit results in continuous measurements between ~52°N and ~52°S latitude with revisits around 1-5 days depending on latitude. This causes the initial ‘rhombus-shape’ you see. In the case of GEDI, the size of the rhombuses has been influenced by the actual altitude the ISS and the expected altitude of the ISS when the GEDI instrument specification were developed. Fairly early in the GEDI mission the ISS increased its altitude which resulted in more overlap of GEDI observations and subsequently less spatial coverage.

Post Reply