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
