How to Get Reflectance Data for Lat/Lon?

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nmapes
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How to Get Reflectance Data for Lat/Lon?

by nmapes » Fri Sep 10, 2021 3:25 pm America/New_York

How do I get the reflectance data for a specific latitude and longitude at a particular date range i.e. daily for 2020?

Example reflectances:
aot_869 angstrom Rrs_412 Rrs_443 Rrs_469 Rrs_488 Rrs_531 Rrs_547 Rrs_555 Rrs_645 Rrs_667 Rrs_678 chlor_a chl_ocx etc.

Example Lat/Lon:
26.114 97.305

Preferably this would have the clouds removed.

Respectfully,
John

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OB.DAAC - SeanBailey
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Answers: 1

Re: How to Get Reflectance Data for Lat/Lon?

by OB.DAAC - SeanBailey » Fri Sep 24, 2021 9:37 am America/New_York

John,

The answer depends on your needs.

If you need the highest resolution, you'll want to grab the Level 2 files and extract the data from them (SeaDAS can help with the data extraction). You can order the L2 files that cover your region of interest from our L1/2 browser.

If you are looking for the highest quality data (but at a lower resolution), you can order the Level 3 products from our L3 browser.

You can also get the L3 data from our OPeNDAP server

By the very nature of the product, clouds are excluded. ...we can only provide remote sensing reflectance data when the sensor sees the surface, if there's a cloud in the way, there will be no Rrs retrieval.

Regards,
Sean

nmapes
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Re: How to Get Reflectance Data for Lat/Lon?

by nmapes » Fri Sep 24, 2021 5:38 pm America/New_York

Dear Sean,

Thank you for helping me, I put the links in a saved document so that I can refer to them as needed. Today we had a meeting on how to export data from Seadas. First we collected from the link in L1/L2 browser the OC and SST files. I am particularly interested in getting Seadas masking and exporting to be run from the command line for a set of OC and SST files for a lat/lon box.

Respectfully,
John

nmapes
Posts: 7
Joined: Fri Sep 10, 2021 3:19 pm America/New_York

Re: How to Get Reflectance Data for Lat/Lon?

by nmapes » Wed Sep 29, 2021 4:42 pm America/New_York

Dear Sean,

So I have built a graph in Seadas to perform WGS84 reprojection, how do I run this on the command line?

I tried to install:
https://seadas.gsfc.nasa.gov/help-8.1.0 ... ation.html
https://oceandata.sci.gsfc.nasa.gov/ocssw/
https://github.com/seadas/seadas-toolbox

But I cannot find gpf.sh in the bin directory.

I tried to install gpf.sh from install_ocssw.py and seadas_8.1.0_linux64_installer.sh.

Respectfully,
John

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Re: How to Get Reflectance Data for Lat/Lon?

by OB SeaDAS - knowles » Thu Sep 30, 2021 10:09 am America/New_York

SeaDAS (as of 8.1.0) does not yet support gpt command line operations, but gpt is planned for the next SeaDAS release.

However, you can do command line operations currently with the SeaDAS science processing (OCSSW) tools such as l2gen, l2bin, l2mapgen, etc.

If you wish to explore the gpt tools now (which will be in SeaDAS shortly), the SNAP software has them now and you can download SNAP. There is a GPT Cookbook in the SeaDAS help menu in SeaDAS 8.1.0 which can aid you.

Danny

nmapes
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Re: How to Get Reflectance Data for Lat/Lon?

by nmapes » Thu Sep 30, 2021 11:41 am America/New_York

Dear Danny,

Thank you, I installed SNAP and I was able to get the command line run of the graph.

I would like to use the Seadas Menu "Export Mask Pixels" in the graph so I can run from the command line. I have a Mask that is built from an expression to use with the "Export Mask Pixels".

I tried BandMaths but it does not seem to export all bands, so I am trying this:

______/-> bandmaths -> subset -> reproject -----\
read -______________________________________-> collocate -> write
_____\-> bandmaths2 -> subset2 -> reproject2---/

All I could find for help was at https://seadas.gsfc.nasa.gov/docs/gpt_introduction.pdf

And since we are using all of the bands will we have to build a large graph or is there a simpler way to get this to work on the command line?

Respectfully,
John

OB SeaDAS - knowles
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Re: How to Get Reflectance Data for Lat/Lon?

by OB SeaDAS - knowles » Thu Sep 30, 2021 1:32 pm America/New_York

There are a lot of gpt help pages other than the one you listed, either on the SeaDAS web page or in the SeaDAS application itself:

See https://seadas.gsfc.nasa.gov/help/

For instance the GPT Cookbook:
https://seadas.gsfc.nasa.gov/help-8.1.0 ... kbook.html

Also since gpt is a tool in SNAP, you might additionally look on the ESA forum:
https://forum.step.esa.int/

Danny

nmapes
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Re: How to Get Reflectance Data for Lat/Lon?

by nmapes » Thu Sep 30, 2021 2:54 pm America/New_York

Thank you, that helped tremendously.

I found that you can edit the xml file and copy and paste this section:

<targetBand>
<name>chlor_a</name>
<type>float32</type>
<expression>not (l2_flags.LAND) and not (l2_flags.STRAYLIGHT) and not(l2_flags.CLDICE) and not(l2_flags.HILT)?chlor_a:NaN</expression>
<description/>
<unit/>
<noDataValue>0.0</noDataValue>
</targetBand>

except changing the name for every reflectance needed.

I also had to put it also in the Subset as follows:

<sourceBands>chlor_a,latitude,longitude,l2_flags</sourceBands>

Respectfully,
John

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