RE: DIFAX Source

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Thanks for the input.  I was hoping you'd contribute to the  discussion.

The Unisys DIFAX ftp system can be very irritating at times. But, it is 
reliable enough that we've never considered going over to Alden.  In 
retrospect, this appears to have been a wise decision.

The FTP setup here is a bit of a kludge.  The FTP server is a RedHat 6.0 system 
which has some NFS incompatibilities with LANtastic TCP/IP. We run LANtastic on 
our LAN.  Even though the rest of the network is monitored, the FTP system 
isn't.  I'm working on a way to monitor that system better.

My biggest complaint is having to pull the charts.  That gives me just one 
chance to get a chart under normal circumstances.  Since cron does this, if it 
doesn't make a connection, I just get a nastygram from the OS (via  email) in 
the morning.  That isn't as useful as the chart  would have been.

The Ku feed is the best way but that's not for everyone.  FTP service is not as 
reliable as other services.  I've developed a more reliable FTP pull mechanism 
written in Perl.  It does a remote directory listing, queries the time for each 
file and then writes the time to a local database.  Then, any time the remote 
time is different from the local databased time, it transfers the file.  This 
makes sure you don't lose data even if you have a network outage.

I'm doing this with the NWS FTP server for Fax charts.  I transfer all 900+ 
charts (.TIF) from that site to the FTP server here.  Then I convert them to 
PCX in preparation for uplinking (see difax directory .pcx files).  I will 
eventually save these in GIF as well.  The only problem is that many of the 
multipanel charts (4 panel ones) are saved on the FTP site as two 2 panel 
charts.  I am working with ImageMagick's montage program to piece these 
together.  When I get this working fully, we may use this as our primary method 
of obtaining Difax charts.

On a side note, our main feed from NWS is not working.  Thanks to a mushroom 
barn fire 9 months ago (local arson spree), the dedicated line to NWS is too 
noisy to use for Difax.  We've been fighting the phone company for months on 
this issue.  Anyway, our backup is... guess...  Alden!  Considering Alden's 
situation, this is putting a priority on getting these other sources working.

I do go back via cron (at about 2300L California time) and run a long request 
for all charts produced the previous UTC day.  I figure net congestion and 
other ftp users will be at a minimum then.  It usually works, but significantly 
increases Unisys' cpu time per chart.

Our FTP server is not on a fast network connection so speed will always be an 
issue.  This is another reason why feeding IDD could be a problem for us.  This 
doesn't count potential firewall problems.  If you are curious, the web server 
isn't located at our facility due to the same bandwidth issues.  It is 30 miles 
away at another facility.

We are in the process of upgrading network capabilities here.  With upgrades 
for E-Commerce, our network bandwidth should increase by an order of magnitude. 
 However, it is unclear how weather will link into this or whether we'll be 
able to.

The charts are really great quality.  When printed, they're very crisp and 
clear.  You might consider placing a map out where any Unidata people who are 
curious can grab it.

I haven't dealt with Alden's charts that are in g3 format.  The PCX files we 
have are very good quality.

Preferably in gif format.  That cuts the file  size (and tranferred bytes) 

That wouldn't be a problem.

I hope Unisys is considering allowing paying Unidata  customers to get DIFAX 
charts via the LDM?

We're considering it.  I'm getting some resistance due to a lot of factors 
here.  But I will continue to pursue this...

Daniel Vietor               Mail: devo@xxxxxxxxxxxxx
Unisys Corp                 Title: Engineer/Meteorologist
221 Gale Lane               Phone: 610-444-2407
Kennett Square PA 19348     Fax: 610-444-2420

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