2. Ships are at sea for longer than planes are in the air, so their power supplies are less reliable, and they are generally dirtier and more chaotic.
2. Ships tend to have proportionally smaller budgets for fancy electronics. More of them are run by random people from poor countries.
None of these is a fundamental limit. There are tens of thousands of ships designed and run such that none of these points matters. But I think that, generally, they tend to damp down enthusiasm about relying on electronics at sea.
If you believe what you see in those "reality" fishing shows on the Discovery Channel, they are using computerized charts and setting crab pots using GPS so the know exactly where they are. Not to say they don't also carry paper charts, and maybe even a sextant so they can navigate if the GPS goes down, but I am guessing they are not used in practice very often.
Yes, offshore fishing boats in the developed world almost universally use GPS, as do most ships of any size. But there’s still a lot of conservatism in the regulation of what you have to have aboard and know how to use.
Reading nautical charts is nontrivial. They tend to be extremely dense (in areas where you need to use one at all); you have to know a bunch of buoy symbols, implicit rules, and so forth. Switching entirely to an electronic system where you could choose optional display layers and tap unrecognized symbols for help could make navigators’ licensing considerably easier.
Edit: A chart I happen to know a little: http://www.charts.noaa.gov/OnLineViewer/18432.shtml . Notice the cable zones (where you can’t anchor), the international boundary, the shipping lanes (where you’re liable to be run over if you’re not a 1000-ton vessel), the magnetic declination rosettes, the angles showing lighthouse visibility, the warning of local magnetic disturbance, the nature preserves … and not far off this particular chart, there are even markings for unexploded ordnance, left over from exercises in the Cold War. And this is a simpler chart than one you would theoretically use to move an oil tanker through the shipping lane, if you did it on paper. So you can imagine how much a good electronic system could clear things up.
Ships also have much more space to store and use charts - it's difficult to unfold a full chart in a small aircraft
Ironically there was a US submarine that hit a reef recently - which was NOT marked on the paper charts it carried.
It was on the electronic charts which are updated much more often
1. Electronics are vulnerable to salt water.
2. Ships are at sea for longer than planes are in the air, so their power supplies are less reliable, and they are generally dirtier and more chaotic.
2. Ships tend to have proportionally smaller budgets for fancy electronics. More of them are run by random people from poor countries.
None of these is a fundamental limit. There are tens of thousands of ships designed and run such that none of these points matters. But I think that, generally, they tend to damp down enthusiasm about relying on electronics at sea.