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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: address@hidden
Unisys Corp                 Title: Engineer/Meteorologist
221 Gale Lane               Phone: 610-444-2407
Kennett Square PA 19348     Fax: 610-444-2420