SUJET :

Hello. I'm new to XyGrib. I'm interested in obtaining Grib files when internet connectivity is limited, e.g. on the high seas via satphone. Is this possible? Thank you.

Hi Andrew and welcome to the forum.

Low bandwidth and medium or high resolution grib files just don't go together.
With a satphone the best com rate is 2400 bits/sec which is very slow. This dictates file sizes of about 20 kbytes as the largest reasonable and it would take some 5 minutes to download. To meet the target file size one needs low resolution grib files 1 or 2 degrees and also with larger time steps - 12 or 24 hours instead of 3. One would also need to reduce the number of variables - perhaps wind only or wind and pressure at sea level.

It is possible to use Xygrib to select a minimal GFS grib (lowest res is 1deg) and download it using a satphone data connection, however, this is not the most efficient way to do the job.

POP3 email protocol (pulling an email from a mail server) is more efficient and tolerant to both low bandwidth and low latency (response times). There are mail servers that are optimised for satphone data connections and use compression to get more data down over the slow connections. Most of these mail server charge a fee but it is worth the money.

Now to getting the data (small grib files). I suggest that you use a free data retrieval system based on emails called saildocs.com. If you a planning an ocean crossing you really need to investigate this resource combined with a suitable mail server and a suitable mail client on the computer connected to the satphone.
With saildocs it is very easy to get small gribs and other valuable weather resource to you via email.

I hope this answers some of your questions
David

Hi David,

Thank you for the helpful response. With hindsight my post was extremely badly worded. I am signed up with Mailasail for email and data compression. I am looking specifically for a service whereby I can order a modest-size Grib by email and receive an email attachment by auto-response. ZyGrib claims to do this for members of its forum but does not appear to be working. I'm a bona-fide member of the forum but the personal code generator won't recognise me. Without a personal code (valid for 2-months) I can't order a forecast. The forum appears to be moribund because I've received no response. In fact the last time I looked the moderator hadn't even released my posts for publication. I believe that XyGrib has picked up the baton from ZyGrib so I was wondering whether XyGrib offers a Grib-by-email auto-response service similar to ZyGrib.

A friend has suggested siriuscyber.net/wxfax/ but I was hoping to stick with ZyGrib (or XyGrib) which I have become very comfortable using on land. I've recently activated a satphone for a forthcoming voyage from Falmouth, UK to the Azores hence my current interest in setting up Grib-by-email.

Andrew

XyGrib has forked off ZyGrib and is no longer the same product. Our grib server is a different one with much more to offer but not all the functionality of ZyGrib was carried through.

Again, saildocs.com is a grib-by-email auto-response service. Once you receive the grib files by email they can be opened and viewed in XyGrib

David

Thanks again. I'll give it a go. A