I'll take it the software to use the data isn't available for free. I have a
little GIS experience and could
probably figure it out. If the resolution in SH3 is pretty poor anyway then low-resolution data would be all that would be required, really just to give a reasonable indication of depth in a given area. I haven't actually measured the resolution in SH3 yet but I can see it is very course, like you say.
It would be good to get some rough maps, though, since I find the in-game one quite hard to read. Another thing that strikes me is that the NA puts to sea with no charts. He has maps, yes, but there is not even an indication of depth on these. I've seen sea charts, coming form a island, and all, and I don't think that any skipper would put to sea with just a basic map. Reefs etc. would need to be marked, there are point depths and contours on real charts. Just a wee gripe that I hadn't thought of till now
.