The Offshore Voyaging Reference Site

Q&A: Getting Greenland Ice Charts By Satellite Phone

Question: What can you tell me about receiving Greenland ice charts by satellite phone?  Is it a good solution and more reliable than weather fax?

Answer: We have had problems getting ice information reliably by weather fax too, but unfortunately satellite transfer does not completely solve the problem either: We have an Iridium and a computer aboard, but the problem is that the Danish Ice Office puts the charts up on its site in a high resolution Adobe Acrobat PDF format, resulting in a 60 to 100 Kbytes or larger file—very expensive to download over Iridium. It’s a pity since a simple change to the Acrobat parameters dropping resolution to 100 DPI (plenty for legibility) would result in a four-fold decrease in file size to 25 Kbytes, a practical size. (I have the same program they use and so was able to verify this by experiment.)

In 2003 I solved this problem by e-mailing the ice office in Greenland at and asking them to send me the file as an e-mail attachment compacted to 72 DPI. This worked, but is dependent on the willingness of the operator to do this on a case-by-case basis.

Another option would be to have a friend on shore download the files on a regular basis, make them smaller in Adobe Acrobat and then e-mail them to you.

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