20000621: Unidata-Wisconsin datastream additions: CIMSS products (cont.)

>From: "James D. Marco" <address@hidden>
>Organization: Cornell
>Keywords: 200006211552.e5LFqCT10971 Unidata-Wisconsin ldm-mcidas pnag2area

Jim,

>       Yes, the conversion time is a bit rushed, but do-able for
>straight forward McIDAS users such as myself.  The time frame
>doesn't permit enough testing before the semester starts, if you 
>delay.

I agree.

>If the delta-formatted products remain available, then 
>customized programs should still work, sans new stuff.

Yes, we could start broadcasting the same products in both PNG and delta
compressed formats, but I would much rather not do this.

I figured that essentially all folks out there were converting the UW
stream image products back into their native McIDAS AREA format; I
guess that I was wrong about at least one site.  The other assumption
that I was making was that either pnga2area would work on a user's
system or it wouldn't.  If it did, then the user would be in exactly
the same position as s/he was before.  If it didn't, I would be here to
step in and help get it working.  The addition of the CIMSS products
would give the sites some products _they are not dependent on_
that they could use to get the new decoding working.

>A thought (these are rare): 
>       Would it possible to modify a copy of the pnga2area decoder
>       to produce an intermediate delta encoded file that could be
>       piped back in to the local LDM data queue for decoding by 
>       the old tools? (Work for Unidata while users get ready for the
>       new format.)

This could be done, but I think that it is time that would be better spent
getting sites up using the new compression.

>Goal:
>       Allow unmodified customized programs to use the new format.

I think that NMIT might be using WXP's ability to read the delta
encoded image files directly (which I always considered a bad idea
since the delta encoding format was not guaranteed).  If this is the
case, there shouldn't be a problem since WXP can also read AREA files
directly.  All that would have to happen is the addition of the
decoding.

>       Allow compression of the network feed to: 
>               Reduce network bandwidth
>               Increase product availability
>       Allow users time to perform the modifications to their
>               locally customized programs, without slowing much needed 
>               upgrades to the data stream.

Good thinking.  I will keep this in mind as a backup position.

>Downside: The local machine would spend more CPU cycles, and 
>               handle data twice, with a 'conversion' program running.
>  
>               Hence, any home-grown programs using the old format are
>               eventually forced into rewrite, simply for efficiency. 

Right.

>               ...and, of course, "We'll get Tom to do it." 

Hmm... :-o

Tom