Why are there still lighthouses?
November 8, 2007 8:40 AM   Subscribe

In this day and age of ubiquitous GPS, why are lighhouses and foghorns still operating?

It's cheap, easy, and good operating procedure to carry a GPS device even on a cabin cruiser or sailboat. Larger ships have radar, as well, as a navigational aid. Clearly lighthouses and fog horns are today just backup systems to the electronic tools, and they're rather limited in their effectiveness. Does anyone have an insight into whether lighthouses and foghorns are still considered essential systems? Is any consideration being given to phasing them out completely?
posted by beagle to Technology (26 answers total) 6 users marked this as a favorite
 
Because you always have a failsafe. GPSs can break. And not every boat will have one - for example, refugee-filled old wrecks.
posted by Happy Dave at 8:48 AM on November 8, 2007


Also, lighthouses and foghorns are totally metal.
posted by illovich at 8:57 AM on November 8, 2007 [7 favorites]


Read up on "selective availability" - while I know that the US government "promised" never to use it again, I don't think their word is all that reliable when it comes to national interests...

However, there are others - Galileo, Beidou/COMPASS, GLONASS, etc.

But - I agree with Happy Dave - radio-waves can fail - heavy sunspot activity could theoretically interfere, etc...

And... how do we explain the Bermuda Triangle...

Besides - with innovations in lighting & automation technology - lighthouses are cheaper than ever to run.
posted by jkaczor at 8:59 AM on November 8, 2007


  • GPSs and RADARs break (infrequently).
  • Ships and yachts lose power (fairly frequently).
  • People make plotting errors on charts (frequently). On a GPS without a chart-plotter, or a chart-plotting GPS without the relevant chart, one must transcribe the co-ordinates from the GPS screen onto the paper chart to determine location, and it's easy to make mistakes under pressure.
  • Removing lighthouses may not be front-page news, but it would still be politically unpopular. Would you want to be the politician or civil servant who removed funding for a lighthouse on a rock a ship later crashed into? Especially if there was loss of life?
  • They don't cost very much. To maintain 70 lighthouses in England and Wales, Trinity House has an annual budget of £30m, which is small change in the context of the public sector as a whole.

    Imagine, a few years in the future when the majority of cars have sat-nav. Would removing all road signs be a good idea? Probably not.

    Also, remember that GPS is a US military program and, although it's unlikely it would ever happen, they are able disable access to anyone except themselves at the flick of a switch: the satellites are able to encode the signal, or introduce deliberate errors that only military GPSs can decode.

  • posted by Aloysius Bear at 9:00 AM on November 8, 2007 [1 favorite]


    Can GPSs operate effectively in thick fog or heavy clouds? I would also imagine in the worst of circumstances having a system that is external to your craft would be a good thing. If your battling waves having a large visual cue where the danger is relative to you would be very helpful, no need to look down and process abstract data. And, as mentioned it makes good backup if you're struck by lightning or something that shorts your delicate instruments.
    posted by edgeways at 9:03 AM on November 8, 2007


    Your GPS can run out of batteries or break, you might not have one, you might misread it ("wait, that was a one, not a seven? oh, crap!") ... basically, you need something that lets you sanity-check your other equipment. And a light on top of a tall tower works pretty well.

    Plus, I'm sure there are lots of fishing boats that, judging by the amount of 'deferred maintenance' they seem to have, probably don't have GPSes, and are captained by people who depend on the lighthouses/foghorns/buoys to navigate with. Or even if they do have GPSes, you don't just turn off or remove the landmarks that people may have spent their whole lives navigating around.
    posted by Kadin2048 at 9:04 AM on November 8, 2007


    From the Trinity House website (the agency responsible for UK lighthouses):

    "The function of lighthouses is not just to warn sailors of a potential danger. They also enable them to find their position."

    Apparently each lighthouse also has a distinctive flash pattern, enabling sailors to identify where they are. I never knew that!
    posted by Nugget at 9:06 AM on November 8, 2007


    A good mariner uses all the information available to him. He doesn't just rely on any one thing. GPS, radar, etc. are great, but can break, be wrong, or be read wrong. So the lights and horns aren't merely a backup, they're an integral part of the big picture you need on the bridge.

    Also, you have to look at a radar or a GPS display. The lights and horns are in your face while you're driving, like signs on the road.

    Ultimately, all of those are only navigation aids. You pilot a ship in restricted waters by being on the bridge and using your eyes and ears.
    posted by ctmf at 9:06 AM on November 8, 2007


    Well, actually, most lighthouses have closed. There used to be lighthouses all up and down the east coast and now most are just tourist attractions. You're begging the question.
    posted by GuyZero at 9:07 AM on November 8, 2007


    Well, actually, most lighthouses have closed.

    That is a very geographically specific answer. Not necessarily a true one in general.
    posted by Brockles at 9:10 AM on November 8, 2007


    Can GPSs operate effectively in thick fog or heavy clouds?

    Yes - definately - they are reasonably low frequency radio-waves, designed to carry over long-distances. As well, they pickup several signals from several directions/seperate satellites.

    The things that interfere more with GPS are: mountains/hills/valleys, buildings and tree's - anything that can block a radio-wave from line-of-sight.
    posted by jkaczor at 9:11 AM on November 8, 2007


    Back in 2000, the US president promised never to use "selective availability".

    However, a certain event about a year later "changed everything" and I'm pretty sure they would rescind that in a flat second if pushed.
    posted by jkaczor at 9:14 AM on November 8, 2007


    the satellites are able to encode the signal, or introduce deliberate errors that only military GPSs can decode.

    The deliberate errors part can be defeated, with some extra effort. You need a shore-based station with a precisely known position. When the GPS lies to your ship, it also lies in exactly the same direction to your shore station. The shore station can then calculate a correction and send it to your ship, timestamped so the ship can back-correct its position from the signal it got.

    The time delay involved means it probably wouldn't be practical for say, a missile. For a ship, though, it could be close enough to real-time to work.
    posted by ctmf at 9:25 AM on November 8, 2007


    That's how Selective Availability works, but not all civilian GPSs are able to correct for it, particularly on leisure craft.

    Essentially, GPS is great but there are a large number of reasons (of which deliberate errors are only one unlikely possibility) why backup systems are required.

    Lighthouses have been drastically cut since their peak in the 19th century (in Britain), but they're not going to disappear completely in the foreseeable future.
    posted by Aloysius Bear at 9:33 AM on November 8, 2007


    I was an Electronics Technician in the USCG and maintained electronics in the Cape Lookout, Frying Pan Shoals and Oak Island lighthouses.

    GuyZero has a point. North Carolina's most famous lighthouse, Cape Hatteras, is no longer an active aid to navigation. It's just a pretty building.

    There are still many active lights, though, and mariners use them for the reasons described above.

    When the light went out, it was a fairly big deal and we made an effort to get out and fix it as soon as we could. But even in the days before civilian-available GPS, that could have been a couple of days, especially for Frying Pan Shoals. If you know where it is, you know why. Plus, back then the Coast Guard was comically underfunded, to the point we sometimes went to Radio Shack to get spare parts on our own dime and then put in an expense report to get reimbursed. Don't get me started.

    The foghorn was never that big a deal. It was supposed to be, but never was. I'm sure now days it's really neglected. The foghorn was some pretty cool audio equipment, though. The final PA could deliver 14 amps of signal to the speakers. Can't remember the overall power delivered. 300 Hz tone, IIRC. The speaker diaphragms were machined from a solid steel disc that tapered down to about 3/8 of an inch thick at it thinnest. It was 'explode your head' loud.

    I imagine one day all the lighthouses will just be National Park Service monuments because it's cheaper and just as effective to put out a buoy for the same purpose.

    The announcement that made me sad was when they stopped monitoring the 500kHz CW emergency and distress frequency. That was for morse code distress signals, like the Titanic sent out. Nobody listening now.

    The new 47' surfboats look awesome though, and I would love a ride. Any active duty Coasties out there?
    posted by neat-o at 9:37 AM on November 8, 2007 [2 favorites]


    If you've ever been out on a boat after sunset on a foggy evening you would quickly realize that trying to navigate into port with a GPS position and compass bearing is intimidating as hell. On the wrong evenings all you can see is light black, which is the sky and dark black which is the water. You begin to question your interpretation of the charts, bearing and GPS position. You wonder just how far ahead of yourself you can actually see and wonder if in the next few seconds you're going to have a sea wall pop up 10 meters in front of you.

    Having even one known point of light on the horizon to allows you to convert all your abstract data into something practical and concrete. It allows you to have an understanding of the atmospheric conditions and allows you to estimate just how far ahead of yourself you can see. It is incredibly useful and a great relief to be able to look at a point of light on the horizon and know that your in the right place.
    posted by 517 at 9:44 AM on November 8, 2007


    I could be wrong. Wiki says Cape Hatteras is still considered operational
    posted by neat-o at 9:45 AM on November 8, 2007


    Yes - definately - they are reasonably low frequency radio-waves, designed to carry over long-distances.

    Actually, they use microwaves. All carriers are between 1100 MHZ and 1600 MHZ.

    But they're using a low bit rate and a decent chip rate, so they get a lot of coding gain. GPS definitely does work in the fog and in bad weather -- it would have been useless for its design function if it did not. (That being, helping military units move around accurately.)
    posted by Steven C. Den Beste at 10:19 AM on November 8, 2007


    Clearly lighthouses and fog horns are today just backup systems to the electronic tools, and they're rather limited in their effectiveness.

    I can't speak to how things are done on commercial vessels, but lighthouses and such are not at all a backup to electronic tools for many private vessels. GPS, compass, charts, lights, and buoys are all used together to navigate safely. Relying exclusively on the GPS would be foolhardy. I'd also disagree that lighthouses are limited in effectiveness. If you have a rock sticking out of the water, people might misread their GPS, miss the rock on the chart, etc. If there is a big light on the rock, it would be pretty hard to hit it. That seems like a pretty high degree of effectiveness to me.

    I'm not sure how you can separate lighthouses specifically from the broader context of navigational markers. Is there some reason that lights on rocks, islands, and points should be treated differently than buoys (lighted or not) that mark harbour approaches, dredged channels, reefs, etc? Surely no one would argue that GPS makes all of those superfluous.
    posted by ssg at 10:57 AM on November 8, 2007


    GPS signals were inadvertently jammed for over a month at the harbor in Moss Landing, CA.
    Many of the TV tuner amplifiers that caused it are still installed on an unknown number of vessels.
    posted by whoda at 11:01 AM on November 8, 2007


    Thanks for the input, it was enlightening, to a landlubber like me.
    posted by beagle at 11:25 AM on November 8, 2007


    GPS will give you position (assuming it's working perfectly, which it doesn't always) but it won't give you orientation. Lighthouses help with that a great deal, along with magnetic compasses, radar, etc.

    Re the US government's ability to disable GPS on a whim, that's one of the motivations for things like GPS+GLONASS dual-system receivers and the Galileo system. People are already relying on satnav for life-and-death decisions (witness the periodic stories of people driving off bridges or piers because their in-car navigation told them to) and having a single, potentially unfriendly, country control that makes people nervous.
    posted by hattifattener at 1:45 PM on November 8, 2007


    For what it's worth, some fog signals on lighthouses and floating marks, at least in Northern Europe, are being removed.

    Saying 'I thought everyone had GPS these days' is all very well, but GPS alone (when it's working properly) only tells you where you are, it doesn't say anything about where the rocks are. Being able to look out of the window and see those rocks is significantly more useful as a constant indicator of your position.
    posted by Lebannen at 2:00 PM on November 8, 2007


    Fog horns are also for other ships in the area. Say there are two ships moving through some heavily fogged-in area. Both of them should be sounding their horn at regular intervals to let the other one know where it is, so they don't run into each other. Sure radar could solve this problem for large ships, but not for small ships (that can't be seen reliably on radar). And like what was said up-thread about having a real world indicator of the shore, a real world indicator of other large ships would be helpful in addition to the radar screen.
    posted by philomathoholic at 2:13 PM on November 8, 2007


    Yesterday a ship under the control of an experienced pilot ran into the Bay Bridge which to the best of my knowledge hasn't moved much lately. The ship had radar and my guess is that it had GPS also. People fail, systems fail, and when the cost of failure is large it's a good idea to have as much redundancy built into a system as possible.
    posted by rdr at 2:15 PM on November 8, 2007


    However, a certain event about a year later "changed everything" and I'm pretty sure they would rescind that in a flat second if pushed.

    Not going to happen, at least not stateside or in Europe. (SA can be manipulated on a regional basis.)

    The reactivation of SA would instantly cripple multiple multi-billion-dollar industries.
    posted by dmd at 5:42 PM on November 8, 2007


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