AVHRR gtanule straddling the date line

Errors and unexpected results
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hproe
Posts: 503
Joined: Sat Nov 27, 2010 3:46 pm

AVHRR gtanule straddling the date line

Post by hproe »

Hi -

I have an AVHRR granule from Metop-A that straddles the date line. I find it impossible to display a correct image from it. Even the native projection is not helpful. I am sure this problem is not new, but I cannot find any relevant reference to this problem.

HP
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bobc
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Joined: Mon Nov 15, 2010 5:57 pm

Re: AVHRR gtanule straddling the date line

Post by bobc »

Hi HP -

I believe this may be related to Inquiry 911 (Metop data is not displayed correctly over the dateline). I ordered some Metop AVHRR L1b data from NOAA CLASS that crosses over the dateline, and I'm seeing the following issues:

    1. In the native projection, there is a block at the bottom of the granule that probes as 'missing' and displays as solid white with the gray scale enhancement.
    2. In the 'World' projection, there are a lot of horizontal streaks of data coming out of the granule. This is worse at high texture quality levels (set in the Layer Controls) and improves a bit with lower texture quality, but it is still a problem either way.
    3. In the 'North Pole' projection, there is a projection seam at the dateline that shows up as a jagged black line. Dependent on the texture quality level, there may also be some horizontal streaks in the display (but not as bad as in the world projection).

Does this sound like what you are seeing? Either way, can you please post your file to ftp? I can then add this to our collection of testing data.

Thanks -
Bob Carp
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hproe
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Re: AVHRR gtanule straddling the date line

Post by hproe »

Hi Bob -

Yes, I see similar things. Where shold I stage the file?

HP
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bobc
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Re: AVHRR gtanule straddling the date line

Post by bobc »

Hi HP -

You can post the file to our anonymous ftp. Here are some instructions:

ftp ftp.ssec.wisc.edu
user anonymous
password e-mail address
cd pub
cd incoming
bin
put {file name}

Once you post the file, please let me know the name of the file and I'll pick it up.

Thanks -
Bob
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hproe
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Re: AVHRR gtanule straddling the date line

Post by hproe »

Granule is staged as
NSS.FRAC.M2.D15071.S2111.E2254.B4356162.SV
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bobc
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Re: AVHRR gtanule straddling the date line

Post by bobc »

Thanks for the granule. I picked it up and I'm replicating the same issues that I was with my granule from earlier. I've added both of our granules to our testing repository. I also updated Inquiry 911 to give some more specifics about the types of display problems we are seeing.

Thanks again -
Bob
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