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[Datastream #LLB-351971]: Question about FNEXRAD datasets

Hi Munsung,

re:
> I uploaded example files in my google drive.
> Please download the files through the following link.
> https://drive.google.com/open?id=1Nj5Kvmz1EJCRgs65pB2u7o15SpDFea8Q
> 
> Original files taken from the LDM have no file extension (i.e. 
> dhr_20180306_2205 ),
> and decoded files using the "pngg2gini" have a ".gini" extension 
> (dhr_20180306_2205.gini).
> 
> If you have any problems in downloading files, please let me know.

I downloaded all 4 files yesterday.  Thanks for making them available.

I first tested them in McIDAS-X, and they all displayed fine.

I next tested the files in a current version of the IDV, and it would
go through the process of displaying the images, but the screen would
remain black.  At this point, I got our IDV developer involved to
do some debugging.  What we found out was that the pixel values from
the file were being interpreted as large negative numbers.  We also
found that you could force the IDV to show the values by selecting
Change Range and then select setting the data range from the data
values read.  This made sense given the interpretation of the values
as being large negatives.

Since we were shocked that the current IDV would not correctly read
and display the values from the files, the developer decided to see
if an older version of the IDV (he had v5.0 readily available) would
display the images correctly, and it did.  The implication of this
is that a change made in the netCDF-Java/CDM library at some point
along the way broke the reading of these files.

Since current versions of the TDS, the IDV and McIDAS-V all use the
same netCDF-Java/CDF library, they all fail because of the same
change.  I will be submitting this as a bug report to our netCDF-Java/CDM
developers tomorrow (I'll be out of the office today).

Presumably, our netCDF-Java/CDM developers will be able to figure
out what change broke the reading of the NEXRAD Level III national
composites, implement a fix, and release a new version.  At that
point, the new code will be incorporated into the IDV first as a
nightly build and then in a new release.  When SSEC will be able to
get around to incorporating the change/fix into McIDAS-V is unknown
to us.  When the change/fix can be incorporated into the TDS is also
an unknown at this point.

Cheers,

Tom
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Ticket Details
===================
Ticket ID: LLB-351971
Department: Support Datastream
Priority: Normal
Status: Closed
===================
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