Doppler for waves?
March 26, 2012 4:53 PM   Subscribe

For all you nautical types: what kind of instruments on a large ship could detect if a rogue wave were headed your way?

For story purposes. I know nothing about ships, much less the giant freighters which might be equipped with top-of-the-line sensor equipment.

(Please note the ship in my story is not a military vessel, so it wouldn't have the kind of equipment you'd have if you were expecting to be attacked.)

But if a rogue wave appeared out of the blue, with what instruments might the captain be able to detect it coming, and how much notice could their instruments potentially give them before it hit?
posted by np312 to Technology (17 answers total) 2 users marked this as a favorite
Not very nautical myself, but I would guess radar as the likely.
posted by Long Way To Go at 5:21 PM on March 26, 2012

I also am not nautical, I know there is a fleet of buoys designed to detect wave height and water temperature and such. I don't think they're resolution is near enough to track a rogue wave travelling through the ocean let alone have something that would detect them in the sea of information and send out a warning.
posted by Phantomx at 5:26 PM on March 26, 2012

I asked Mr. Pies (former sailboat captain with a 50-ton license) and he said he knows of nothing that would detect a rogue wave that the typical boat would have. Or, for that matter, of any device that could detect a rogue wave (albeit with the caveat that he has very limited knowledge of newer military vessels). His experience is limited to sailboats and catamarans, but he's very knowledgeable about both and spent around a decade sailing them professionally.
posted by pecanpies at 5:40 PM on March 26, 2012

Mr. Pies also states a radar wouldn't be able to do so.
posted by pecanpies at 5:41 PM on March 26, 2012 [1 favorite]

Best answer: There's an article about rogue wave detection here. The article indicates that radar, in fact, is used to detect them, along with software.
posted by dfriedman at 6:01 PM on March 26, 2012

Best answer: The thing is that rogue waves, by their nature, do not really "go" anywhere. They simply arise out of freak interference between two or more other existing waves, and then disappear as soon as those waves move apart. If one happens to crop up under or next to your ship, you "detect" it by having everything go to shit all at once. If it's off in the distance, you could see it visually or with some thing that bounces off water (microwave radar, maybe?) but it wouldn't affect you unless one of the component waves that formed it was headed in your direction.
posted by Aizkolari at 6:22 PM on March 26, 2012 [3 favorites]

Yes, I should clarify: as dfriedman's link points out, radar alone is insufficient to detect a rogue wave.
posted by pecanpies at 6:36 PM on March 26, 2012

There's an informative section on rogue waves and their potential detection in Sebastian Junger's book The Perfect Storm.
posted by ChuraChura at 7:09 PM on March 26, 2012

Best answer: Radio; to listen for warnings.
posted by theora55 at 8:05 PM on March 26, 2012

Radar might pick it up, if it was sufficiently larger than the surrounding seas and if someone happened to be looking at the radar closely enough to see the echo approaching. Not only would you have to spot it, you'd have to identify it as a wave from the background clutter at sea level and track it for long enough to know that it would intersect with your position. But 'rogue' waves don't have a particular life - they don't travel around the ocean until they hit something, they form suddenly out of particular circumstances, then dissolve just as quickly at some point. There's no pattern involved, which is why they're called 'rogue waves'. Radio might give you a warning if someone within range had spotted one, wasn't too busy trying to save themselves and was inclined to send out a general warning.

The main reason these waves are so dangerous is because they are hard to predict or detect in any meaningful way early enough to do anything useful. It's only relatively recently that they've been proven to exist at all, having for most of nautical history been stored on the same shelf as mermaids.
posted by dg at 8:17 PM on March 26, 2012

I am not a navy captain or pilot of a large commercial vessel or anything, but no such technology is available for private sailboats to my knowledge, including to very nice private sailboats designed to make ocean-crossing passages. This is probably because aizkolari is correct: a rogue wave is not of the long-period groundswell type that you can predict or track easily. If you're sailing in 20-foot seas and two waves run together into a 40 foot rogue wave, then it's going to happen right on top of you. If you're sailing through a 20-foot groundswell 1000 miles out from a large storm, it poses no real danger to your boat, since the waves won't break until they hit shallow water.

As it stands, you could be sailing across the pacific in a $5 million cruising yacht and you would not have any equipment available to detect this.
posted by tylerkaraszewski at 9:38 PM on March 26, 2012

Best answer: For your story purposes, I think your large ship could have a radar that's always on, and the crew suddenly notices a blip on the screen that's moving toward them. (surprise!) It turns out that the reason the rogue wave was actually visible on the radar is that the wave is enormous, 100 feet high. (suspense!)

Or, if there's another boat in the vicinity, that boat could frantically radio your boat with the news that the rogue wave has appeared out of nowhere and is about to break on them. (excitement!)

Because the rogue wave doesn't travel far (or, indeed exist for very long) there's no way it could be detected by sensors and a warning broadcast. (mystery!)
posted by exphysicist345 at 10:13 PM on March 26, 2012

I agree with the answers that say things along the lines of 'technically radar, but rogue waves don't really work like that'.

I would also like to note that the captain is highly unlikely to be the person who notices it. The captain has people for that. Unless there's a specific reason for him to have been called to the bridge (e.g. a Mayday has just been received by another ship that's been hit by a rogue wave and fallen apart), he is more likely to be in his cabin playing solitaire doing paperwork, or, you know, sleeping.
posted by Lebannen at 4:20 AM on March 27, 2012

Best answer: Coastal stations use CODAR, which would likely be relayed to ships at sea by radio alert. If you listen to the 20 and 60m shortwave bands, you'll hear CODAR's distinctive "twop!" sound, like someone tweaking a taut Slinky.
posted by scruss at 8:37 AM on March 27, 2012

Best answer: For your story, consider having the ship hear warnings from other ships. The best "detection" of a sea state is to go out and look at it. Ships and coast guards regularly broadcast the conditions they are experiencing.
posted by Cool Papa Bell at 9:24 AM on March 27, 2012

Best answer: This awesome book is about giant and rogue waves, and has lots of info on the equipment necessary to detect (or mostly, to not detect them):

The Wave: In Pursuit of the Rogues, Freaks and Giants of the Ocean
posted by SuperSquirrel at 10:25 AM on March 27, 2012

My dilettante interest in rogue waves was borne from reading about solitons. These are single, stable, 'nonlinear' waves that can travel large distances. (Examples: 1, 2, 3.) Rogue waves can sometimes exhibit characteristics of solitons, but I lack the math needed to know if a single, large wave/soliton could travel the distances necessary to become noticed the way your story requires.
posted by Yoshimi Battles at 10:46 AM on March 27, 2012

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