How to create a TrueColor image?

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ebradbury
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How to create a TrueColor image?

by ebradbury » Mon Apr 11, 2022 10:26 am America/New_York

Hello,

I'm a new user trying to learn how to use SeaDAS and the command line tools create a highest possible resolution TrueColor image (and later an animation) such as this one: https://oceancolor.gsfc.nasa.gov/gallery/feature/images/A2014270171500.GulfOfMaine.jpg.

It seems like reproducing a TrueColor image from raw (modis level1?) data might be a good way to learn how to access and process data. I would like to do the same with SST.

Some questions I have...
- Most of the products seem to be at 4km max resolution... can we get higher resolution by processing ourselves?
- Are there tools for removing clouds from generated images?
- How do you georeference the images?
- Are there NASA tools for producing animations or is this up to the end user?

Thanks for the help!

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OB SeaDAS - xuanyang02
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Re: How to create a TrueColor image?

by OB SeaDAS - xuanyang02 » Mon Apr 11, 2022 2:34 pm America/New_York

You can use mapgen to create a true color image with --use_rgb option -- https://seadas.gsfc.nasa.gov/help-8.2.0/processors/ProcessMapgen.html#cl

Code: Select all

mapgen --ifile A2010283180500.L1B_LAC --geofile A2010283180500.GEO --use_rgb
The generated true color image has cloud already removed.

Modis L2 files have resolution at 1km and they are already geo-referenced.

SeaDAS does not have tools to produce animations.

ebradbury
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Re: How to create a TrueColor image?

by ebradbury » Wed Apr 13, 2022 12:31 pm America/New_York

Thank you for your reply.

I'm running `mapgen` and got an error: "Unrecognized HDF-EOS file A2013208173500.L1A_LAC"

I downloaded the input file from here: https://oceancolor.gsfc.nasa.gov/cgi/browse.pl?sub=level1or2&per=CU&day=19095&prm=TC&set=10&mon=19052&sen=amod@tmod@vrsn@vrj1&rad=0&frc=1&rgn=GeorgesBank&id=1649864421.1882237&cn=42.88&cs=39.64&cw=-69.05&ce=-65.34&dnm=D&file=A2013208173500.L1B_LAC_BRS_BRS&ndx=15483&wid=170&hgt=254

Then extracted it using `bzip2` and ran `mapgen --ifile A2013208173500.L1A_LAC --geofile A2013208173500.GEO --use_rgb`.

I noticed that your example uses a `.L1B_LAC`... could that be the issue?

OB SeaDAS - xuanyang02
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Re: How to create a TrueColor image?

by OB SeaDAS - xuanyang02 » Wed Apr 13, 2022 1:28 pm America/New_York

Yes, mapgen with --use_rgb option needs L1B + GEO files as input

You can create an L1B file with modis_L1B --https://seadas.gsfc.nasa.gov/help-8.2.0/processors/ProcessModis_L1B.html#cl

Code: Select all

modis_L1B A2010283180500.L1A_LAC  A2010283180500.GEO

ebradbury
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Re: How to create a TrueColor image?

by ebradbury » Mon Apr 18, 2022 9:43 am America/New_York

Thank you - I was able to generate a TC image using these commands...

`modis_GEO A2013208173500.L1A_LAC`
`mapgen --ifile A2013208173500.L1B_LAC --geofile A2013208173500.GEO --use_rgb --oformat tiff --resolution 1km --projection mercator`

Am I correct that this command will generate the highest possible resolution?
How can I achieve cloud removal?

Thank you

(Attached file is for reference... I had to downscale it to meet the upload size limit)
Attachments
A2013208173500.L1B_LAC.MAP copy.jpg
A2013208173500.L1B_LAC.MAP copy.jpg (478.11 KiB) Not viewed yet

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