Rainbows

Rainbows

Postby arb » Wed Dec 04, 2013 11:30 am

Hi, I'm seeing some odd artefacts whenever I run polar2grid.
It looks as though areas which are black or white are being turned into rainbows, see attachment.
Does anyone recognise this problem?
Attachments
npp_viirs_true_color_crefl_None_20131127_124307_tco_lcc.a.gif
npp_viirs_true_color_crefl_None_20131127_124307_tco_lcc.a.gif (153.09 KiB) Viewed 6966 times
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Re: Rainbows

Postby davidh » Tue Dec 10, 2013 12:24 pm

We've noticed this too. As far as I can tell it has to do with the corrected reflectance algorithm (which I don't really have control over). In past cases I've looked at the bands used by CREFL and didn't see anything out of the ordinary so I have always blamed CREFL. Let me know if you notice anything that might give us an idea what's causing this. In the mean time I'll look at a case that Kathy gave me today and see if I find any answers.
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Re: Rainbows

Postby kathys » Tue Jan 07, 2014 5:24 pm

We think we have found the problem you are seeing and the solution. The problem occurs when we are trying to combine bands to create the RGB file that have different regions missing data. If you try to create an RGB using CREFL input files where a FOV has 2 or 1 band missing, you will get these types of colors. The solution is to mask FOVs where 1 or more of the bands you are using to create the RGB are missing. We are working on a patch to the polar2grid software that will fix this. Sorry for any problems this might have caused.

Kathy Strabala
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Re: Rainbows

Postby jenniffer07 » Mon Jan 27, 2014 4:04 am

i think its not an odd artefacts but it may happen in some circumstances.. :)
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Re: Rainbows

Postby kathys » Wed Sep 03, 2014 3:28 pm

This issue has been fixed in the polar2grid version 1.2 software release. The problem was that incorrect saturation and fill values were being stored in the crefl files. The bug was corrected, and this updated version of the crefl software is now executed as part of the crefl2gtiff.sh processing script. We have also notified the crefl software developer about this problem.

Kathy
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Re: Rainbows

Postby Louise » Thu Oct 08, 2015 4:00 am

really different one!!!!!
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Re: Rainbows

Postby arb » Thu Nov 19, 2015 12:00 pm

I'm still seeing this type of artefact in polar2grid v2.0, see attachment.
Not in bright areas like previously but in dark sea between bright clouds, so it looks like a polar atoll!
Attachments
viirs_201511131226_rgb_crop1.jpg
viirs_201511131226_rgb_crop1.jpg (19.06 KiB) Viewed 6578 times
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Re: Rainbows

Postby davidh » Mon Nov 23, 2015 12:29 pm

Hi Andrew,

Would it be possible to get access to the data for this case too, like the data drop out problem you saw? My guess is something with remapping and combining the various resolutions that are overlapping oddly. One thing you could try until I have a chance to look at the data is running the P2G commands but don't provide the I-band data. This will result in an unsharpened image. If this output image looks good then I'll have to see why the I and M band data differs so much.

Thanks,
Dave
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