RE: DIFAX Source

I'll chime in on Larry's email since I have some say on the Unisys end of 
things.

We (Scripps Inst of Oceanography) use DIFAX, but do not get it from Alden.  We 
are a customer of Unisys.  This message is NOT an endorsement of Unisys.  We 
have our own, if different, set of problems with Unisys.  However, the system 
is usually reliable.

We pay Unisys $300.00 per year (ie, $25.00 per month, once per year) for the service.  There are 
three major problems.   First, this is a "pull" technology system.  My old friend  
"cron" ftp's to Kennett Square once an hour (about 5 minutes  past) to get the maps for 
the previous hour.  Not an elegant  solution, but it works.

Unisys provides a couple of methods for accessing Difax data.  We do offer a Ku 
band feed similar to Alden where Difax charts are pushed to the end user.  
There is a user/passworded FTP site where you can obtain Difax charts using a 
pull method.

We are currently addressing several new methods for providing Difax to the end 
user.

The second problem has to do with reliability.  The maps are produced on some 
other machine and transferred to the ftp host.  Frequency of transfer is 
unknown.  The problem is that this transfer is periodically shutdown (or fails) 
and they forget to restart it.

This is true.  The Difax we have comes in via land line to a server which then 
queues it for Ku uplink.  Afterwards, the files get transferred to the FTP 
site.  The Difax charts are compressed PCX files.

The third problem is format.  The maps are created as "pcx" format files.  They 
can be fairly large.  The latest 00Z chart is about 340K.  The latest western tropical 
surface chart is about 600K.  When I print these files on my 11x17 inch printer, I get 
large, crisp, clear maps.

PCX format is a legacy format for software Unisys provides to the end user.  We 
could have moved to a better format but we have too much software in the field 
that only supports PCX to do that at this time.

These files would be a lot smaller, with no loss of detail, if they  were in 
"gif" format.  They don't seem to be in any hurry to make this change.  
Remember, Unisys is the patent holder for the compression algorithm in gif.  Seems 
strange.  My connect time (and their consequent cpu time) on their ftp host would be much 
shorter with gif files.

At some point, you will be able to obtain GIF image Difax charts on the FTP 
server.  I'm working on this now.

One plus is that their trouble desk is manned 24/7 and I've never called there 
and not spoken with a real human being.  They don't always know how to solve 
problems (or have authority to solve problems), but they can usually contact 
someone who does.  Usually.

We do have an elaborate system for monitoring all the feeds coming in including 
Difax.  We do have 24x7 support for the trouble desk.  The operators can resend 
products if needed.

Finally, I have had conversations with Mike Porrecha (sp?) who indicated (but 
did NOT promise) that when the NWS shuts DIFAX down, Unisys might continue to 
produce the maps.

We are investigating a couple of methods for accessing Difax charts in the 
post-Difax-feed days.  We currently download a number of various fax charts 
from the NWS FTP server and will upgrade this feature in the future.  Some 
charts will be recreated from Redbook graphics or use of products like WXP in 
the future as alternatives to Difax.

BTW, it Mike Porreca.

This is all "for what it's worth".  I think that, if a bunch of Unidata folks 
transferred their allegiance to Unisys and all started pulling maps down, their system 
would probably choke.  But, it might be a short term solution for some of you.

We're talking here on how we might be able to help.  However, this is still in 
its early stages.  We do have some issues to work out on this end.

________________________________________________________
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