back to article Navigating without GPS is one thing – so let's jam it and see what happens to our warship

Learning to fix your position without GPS is one thing. Actively jamming it to induce a deliberate system failure aboard your own ship is quite something else, as we found on Monday. The Register is currently embedded aboard HMS Severn, the Royal Navy's navigation training ship. Yesterday afternoon we witnessed the practical …

  1. Gene Cash Silver badge

    I guess I'm too much of a navigation geek...

    I instantly knew what a cocked hat was.

    If I have 2 acres of woods, then wait a week and send in the army to find me. I will be totally lost. I never have the slightest idea of where North is, or what direction I'm traveling without a compass or Google Maps. As a result, I've been forced to become a complete mapping and navigation geek. All my motorcycles have a small eyeball-sized spherical compass stuck somewhere on them, the pin-on kind you can get at the camping store.

    Thanks for the article.

    1. Andy The Hat Silver badge

      Re: I guess I'm too much of a navigation geek...

      Cocked hat navigation is great in the middle of the North Sea ... I presume they break out the emergency sextants and super accurate Casio watches (with calculator) at that point?

    2. Chris G Silver badge

      Re: I guess I'm too much of a navigation geek...

      I have no problems when out in the woods or any countryside but get lost in cities with high buildings and narrow streets, that is where I find the ball compass on my backpack straps, invaluable.

      Otherwise I prettymuch always know where North is, sitting with friends drinking at the weekend, one chap (a biker) pointed vaguely in the direction of Valencia.

      I pointed out he was nearly 30° off to the south, a discussion followed with proof of my point provided by smart phone gps.

      My brother used to sail a lot, got hit by a squall out of site of Northern Brazil in the early daysof GPS, the squall had damaged the antenna by dumping a few tons of water on it so he just used his compass an ancient plastic sextant and a radio time signal.

      1. Anonymous Coward
        Anonymous Coward

        Re: I guess I'm too much of a navigation geek...

        I got lost in Sydney the first time I went there. I can usually get by in cities navigating with a map and the sun. But in Sydney I kept getting lost. It took me ages to remember that I knew what the problem was.

        1. Neil Barnes Silver badge

          Re: I guess I'm too much of a navigation geek...

          Got lost that way once in New Delhi, the first time I worked there. Took me a little while to discover that on the street map I was using, North was off to the side for some reason.

          When I'm in Rio, I'm *always* confused because the sun goes the wrong way...

        2. GreyWolf

          Re: I guess I'm too much of a navigation geek...

          Same experience, but in Sweden. At home in UK I couldn't get lost; I had some kind of built-in awareness of direction and time.

          But in Sweden the sun was in the wrong place in the sky, and I was always disoriented, until a few years in when I got used to it.

          Then I moved back home, and was disoriented all over again.

          1. Jimmy2Cows Silver badge

            Re: I guess I'm too much of a navigation geek...

            Yout built-in nav system (dead reckoning) got screwed up by unexpected signals, but gradually recalibrated. Ain't evolution wonderful?

            Except perhaps in Tennessee (though I understand this bastion of progressiveness since lifted the outright ban, instead favouring to inject doubt into the scientific process whenever they feel like it).

        3. Jim Whitaker

          Re: I guess I'm too much of a navigation geek...

          In Sydney, I too found that my instinctive rough knowledge of location was lost and I had to keep repeating "No, that's South" to myself. Took a week to, mostly, wear off.

      2. John Brown (no body) Silver badge
        Coat

        Re: I guess I'm too much of a navigation geek...

        "Otherwise I prettymuch always know where North is,"

        It must be your magnetic personality.

    3. J.G.Harston Silver badge

      Re: I guess I'm too much of a navigation geek...

      You'd be better off with a proper map. Y'know, one that actually has *features* on it.

      1. Cederic Silver badge

        Re: I guess I'm too much of a navigation geek...

        The map indicates that there are at this location two acres of natural woodland, no changes in altitude sufficient to require contour lines and an unpaved track along one edge.

        You look around you and can see only trees, bushes, ferns and bluebells. Which part of the wood are you stood in, and how has your map assisted you in that determination?

        1. W.S.Gosset Silver badge

          Re: I guess I'm too much of a navigation geek...

          Ah! That's just a problem of map scale/resolution. Buy a map that's 1;1 scale and you'll be sorted.

    4. Timbo Bronze badge

      Re: I guess I'm too much of a navigation geek...

      "If I have 2 acres of woods, then wait a week and send in the army to find me. I will be totally lost. I never have the slightest idea of where North is, or what direction I'm traveling without a compass or Google Maps"

      If you are "stuck in woods" you don't need to wait a week...or even much more than a day.

      Just look at your watch/mobile phone, check what the time is and then look up at where the Sun is - that will give you enough information to figure out which direction to travel in, even if it is only basic - but it will give you a point of reference so you do not stay lost.

      1. Snapper Bronze badge
        Joke

        Re: I guess I'm too much of a navigation geek...

        Another reason to hate The Cloud...

        1. Anonymous Custard Silver badge
          Paris Hilton

          Re: I guess I'm too much of a navigation geek...

          It always amuses my better half that (at least before the pandemic) I can happily fly to Europe and then drive all over the place (usually into Geneva then across into southern France, but other times into Germany or Benelux) without batting and eyelid or getting at all lost, but every time I go into one of the local housing estates around here I tend to get lost.

          Although in my defence that place is a complete soulless rabbit-warren of little streets that all look the same and are crammed full of identiclone carbon copy houses jammed in as tightly as possible, and they all look exactly the same after you've gone down a few of them to try and get to your destination.

          It's almost like being in Fantastic Voyage and trying to navigate into the branching bits in the lungs.

          Paris, for being lost and confused...

      2. phuzz Silver badge

        Re: I guess I'm too much of a navigation geek...

        2 acres is small enough that you can usually see clear across (1 acre is ~64x64m), and if it's not too overgrown would take about one minute to walk across. I think OP was making a joke ;)

      3. Keith Langmead

        Re: I guess I'm too much of a navigation geek...

        So long as you remember that while most people generalise that the sun rises in the east and sets in the west, that's only true at around this time of year and March (eg the equinox). June/July for instance it can be closer to rising in the NE and setting NW.

        Actually had to explain that to a friend on holiday in July when working out which path to take, as while I think they knew it in a factual sense, they'd never needed to think of it in a practical sense. Me on the other hand... years of trying to photograph sunrises/sunsets and planning when to be in certain locations has made me very aware of that fact. The suncalc website is probably my favourite website... after thereg of course. ;)

        Without that knowledge it's fine if you're just after rough "head in a vaguely northern direction", but not so useful if you need more precision.

        1. the Jim bloke Silver badge
          Happy

          Re: I guess I'm too much of a navigation geek...

          Before GPS became nearly universally available, mining operations used to work from localised "mine grids", which were set up for convenience of mining operations, with interoperability with external entitys a distant second concern. Basically they were established with a major axis aligned to the strike of the orebody, so you could have 'mine grid north' say, 37 degrees off true (grid) north.

          So, one winter morning, the engineers were telling the earthmovers they wanted such and such a job done at the north end of operations, and the earthmovers supervisor asks "which way is north?.."

          I respond without thinking..

          "North is where the sun rises.."

        2. W.S.Gosset Silver badge
          Happy

          Re: I guess I'm too much of a navigation geek...

          > years of trying to photograph sunrises/sunsets

          Elusive little beasts, aren't they? Keep at it! I'm sure you'll succeed in finding one one day.

          1. Anonymous Coward
            Anonymous Coward

            Re: I guess I'm too much of a navigation geek...

            I've tried during the day, and I've tried during the night. Never around.

      4. Wibble

        Re: I guess I'm too much of a navigation geek...

        Natural navigation... Trees will have moss growing on their north side (in the northern hemisphere) as it doesn't like light. Use that for a bearing. The sun's simple to use, but slowly moves around at 15 degrees/hour, moon too. Slope of the ground helps with general direction. Bushes slope away from the prevailing wind, generally south westerly in the UK.

    5. the Jim bloke Silver badge
      Pirate

      Re: I guess I'm too much of a navigation geek...

      I perfected my navigation skills playing the original Wizardry computer game..

      I could tell exactly where I was from 3 perpendicular white lines, identical to every other white line, on a blank field.

      This is actually based on a similar principle to the fallback system for when GNSS loses lock - most have some sort of inertial tracking that calculates your new position based on last good position and measured movement...

  2. Pete 2 Silver badge

    Are we there yet?

    > and in some circumstances it's possible for the ship's true position to be outside the cocked hat.

    would this be known in the trade as a "cocked up hat"?

    1. 2+2=5 Silver badge
      Joke

      Re: Are we there yet?

      > would this be known in the trade as a "cocked up hat"?

      Dunno, but if the true position is really badly out you might find yourself about to redefine the 'dead' in 'dead reckoning'.

      1. Korev Silver badge
        Coat

        Re: Are we there yet?

        These puns are bearing on awful...

        1. Will Godfrey Silver badge
          Happy

          Re: Are we there yet?

          That comment encompasses the whole matter

      2. John Brown (no body) Silver badge

        Re: Are we there yet?

        That would be an ecumenical matter.

        Signed

        The Cardinal

        1. Korev Silver badge
          Windows

          Re: Are we there yet?

          Yes!

          1. John Brown (no body) Silver badge
            Thumb Up

            Re: Are we there yet?

            And your point?

    2. TReko

      Re: Are we there yet?

      Then you'd be told that the bearings were "duff gen"

  3. Andrew Findlay
    Boffin

    It's worse than you think...

    > and in some circumstances it's possible for the ship's true position to be outside the cocked hat.

    The actual position is most likely to be *outside* the cocked hat...

    Each of those lines is a bearing to some known object, and if done carefully there is an equal chance of being to the right or to the left of the line. Being inside the cocked hat has a probability of about 1/8 to a first approximation. The size of the hat does give an indication of how good your fix is, but don't assume that you are in the middle!

    [ Credit to Prof Edward Stansfield for explaining this a few years ago - his inaugural lecture at Reading University was titled something like 'In My Cocked Hat'. ]

    1. J.G.Harston Silver badge

      Re: It's worse than you think...

      I remember that - years'n'years ago, so probably an Open University lecture combining mapping and probabilities.

      To quote Captain Pickard: Why doesn't somebody look out of a damn window!

      Edit: Bingo! The reference to the OU here !

      Wow. 1984. I feel old....

    2. Lotaresco

      Re: It's worse than you think...

      I just spent ages composing a similar reply. The error on each bearing will be randomly +/- the actual bearing. Hence you can be either side of any of those lines meaning that being outside the cocked hat is more probable than being in it. Many navigators have had an unfortunate rock/hull interface as a result of assuming they are safely inside the cocked hat. Even GPS doesn't eliminate unfortunate position errors. For example I nearly dinged an unlit buoy in the dark despite GPS telling me I was a couple of hundred metres away from it. Low tide and a strong current mean the buoy had been pushed to the end of its chain and there was a lot of chain to cope with the tidal range. There's a reason why "Ooops sorry, left hand down a bit." is the Cry of the Navigator.

  4. Boris the Cockroach Silver badge
    Thumb Up

    Must admit

    it is bloody hard to get lost around here....

    However... the real danger is the tide levels, the currents and the sandbanks....

  5. Victor Ludorum

    Outside the cocked hat

    As an occasional sailor with a Day Skipper qualification, I get how the cocked hat reckoning etc works. Other reasons for errors can include not correcting for True/Magnetic North, inaccuracies in the compass itself (fixed onboard compasses should be recalibrated occasionally), and large ferrous bodies (oo-er) interfering with the compass.

    Loving the series, more please!

    1. SkippyBing

      Re: Outside the cocked hat

      There was a nice period where the difference between True and Magnetic North where I was regularly flying was less than a couple of degrees. Given no one ever flies that accurately it could be safely ignored.

      1. imanidiot Silver badge

        Re: Outside the cocked hat

        Depends on where you are. In NL magnetic declination is roughly 2 degrees east currently. Not really enough to worry about for short hops, but enough to take into account on longer distances. Head east and it starts rising. It's up to about 5 to 6 degrees by the time you get to Poland.

        1. W.S.Gosset Silver badge

          Re: Outside the cocked hat

          Yes, I've read that Poland is increasingly leaning to the Right.

      2. Lotaresco

        Re: Outside the cocked hat

        "There was a nice period where the difference between True and Magnetic North where I was regularly flying was less than a couple of degrees."

        Late 1990s for what felt like forever at the time. I got out of the habit of bothering with the correction at that time. Much of sailing around the Isle of Wight is pilotage anyway, so for a decade or more I did it without GPS/Decca or even bothering much with a chart.

    2. John Jennings

      Re: Outside the cocked hat

      I regularly use the cocked hat method for transits offshore. Its as quick as transferring a gps coord. Of course I do have paper charts too....

  6. Antron Argaiv Silver badge
    Coat

    Navigation

    I usually have a fairly good idea of where I am and what direction I should be going in. Even when walking in the [small] woods around my home, it's hard to get lost...keep walking and you'll hit a road. Camping and hiking in the wilderness is a bit more challenging; step off the trail a few hundred meters and you'll have ni idea where you are, and the tree cover will keep you from seeing any landmarks. A real map and compass are your friends then. Also having a good idea of your last known position.

    I practice navigation whenever I can, and have some strategies for self-correction in case I've got it wrong. I do own a sextant, and have used it on land. My hat is off to those who can plot their position within yards...the best I could do was several miles. But I am pretty good with map (not chart) and compass. Even got 2d place in an orienteering meet when my kids were in Scouts (they had an adult contest so we wouldn't feel left out).

    // map & compass in the pocket

    1. Cederic Silver badge

      Re: Navigation

      I've navigated by dead reckoning and approximate sun position in a mountain forest in Morocco (with wild apes) and in the outback in Australia (with a 4 foot lace monitor). Both times I had a mobile phone with me, I just didn't use it.

      I've since decided that this was silly and now have a compass in my camera bag.

      1. W.S.Gosset Silver badge

        Re: Navigation

        > with a 4 foot lace monitor

        Crucial for the preservation of footwear stability in rough country

        1. W.S.Gosset Silver badge

          Re: Navigation

          We have cockatoos, too.

          Don't ask...

  7. mhs1973

    jamming isn't the point

    but gradually changing the offset well enough to put the training ship from the north sea to lake Geneva.

    1. Nifty Silver badge

      Re: jamming isn't the point

      This is what I was thinking. I am certain that the current gen of potential enemy jammers are already perfectly capable of spoofing location by recreating what looks like a genuine GPS signal, avoiding setting off alarms and gradually shifting a ship off position. I just hope that the GCHQ tech dept is working on decent countermeasures.

      1. imanidiot Silver badge

        Re: jamming isn't the point

        I'm pretty sure they already have systems checking if GPS heading starts deviating too much from magnetic/gyro heading (and similar for speed probably)

      2. martinusher Silver badge

        Re: jamming isn't the point

        The smart move would be to carry a GLONASS handheld somewhere and use it to cross check. (Many handhelds can use both systems.)

        Its always a good idea to know where you are just in case. Equipment can break down and batteries go flat.

    2. Cederic Silver badge

      Re: jamming isn't the point

      R V Jones approves.

  8. Anonymous Coward
    Anonymous Coward

    I may need this in the city too

    I'm in Odessa at the moment, and I needed to get to an address.

    I ended up using the basic map I got from the hotel (old habit that saved me more times than I can count) because this is what GPS navigation gave me at a certain point. Note: using local SMS for Google data stream because the phone company price gouging on data usage outside the EU is at a level that even Martin Shrekli would not have dared to inflict (think charges at approx 28000 x local tariffs, and that's retail):

    - TomTom: meh, don't know that street. Try entering it in the local language (good luck typing Cyrillic on a UK keyboard, and that's assuming you even speak the language). So, absolutely, totally brutally useless.

    - Google Maps: go left

    - Apple Maps: go right

    I'm not kidding, the end points on both maps were more than 2km apart. I must admit I forgot to check which one was accurate (I was way too relieved to actually get there), but I'll go there again tomorrow so I'll check this time. After I have walked there with a map, that is.

    On the plus side, at least the phone compass worked :).

    1. Anonymous Coward
      Anonymous Coward

      Re: I may need this in the city too

      What's OpenStreetMap like around those parts? It can be surprisingly good when commercial maps don't see much profit in an area.

    2. Irony Deficient Silver badge

      I’m in Odessa at the moment, …

      … and I needed to get to an address.

      I ended up using the basic map I got from the hotel (old habit that saved me more times than I can count)

      If your hotel has English-speaking staff behind the front desk, perhaps one of them could advise you on how to get to a particular address? (A hotel’s basic map generally shows the main thoroughfares, which is certainly useful, but doesn’t always show side streets in sufficient detail.)

      1. Anonymous Coward
        Anonymous Coward

        Re: I’m in Odessa at the moment, …

        Oh, they did, but it gets kinda annoying having to walk back to the hotel for every new target. I know I need more exercise, but there are limits :)

  9. Anonymous Coward
    Anonymous Coward

    Hmmmm....

    " Navigating accurately without GPS availability is something the Navy places a high premium on."

    I would have hoped that navigating accurately without GPS was the default approach, and GPS was a nice to have confirmation of that.

    As for navigating onland and around towns, I find satellite dishes and TV aerials are a very good indication when the sun is not shining. Not much use in the dark though.

    1. Aristotles slow and dimwitted horse Silver badge

      Re: Hmmmm....

      I'm not sure it is any more as I like to discuss this with a friend who is a senior officer on a big Maersk container vessel. I know in the leisure sphere that the RYA takes the view that you should know how to navigate using charts and stuff etc, with GPS being a good tool "but not to be relied upon" due to failure.

      But I think the whole commercial and military view is that GPS and such like is the primary source with good old charts and stuff being the secondary method and for close inshore work.

      Happy to be corrected.

      1. Yet Another Anonymous coward Silver badge

        Re: Hmmmm....

        No the Royal Navy is very clear that 'proper' navigation is what you rely on and GPS isn't even a backup - it's there because it came with the systems.

        Commercial tends to rely much more on GPS because they can't afford to have a bunch of navigation officers taking sightings around the clock and you have to be quite precise maneuvering a container ship the size of the Isle of Wight, passed the isle of Wight

        1. BaudToDeath

          Re: Hmmmm....

          Which is why they use a pilot for the bits where you can see land...

        2. HarryBl

          Re: Hmmmm....

          Sights aren't taken 'round the clock'. They are (or were before Transit/GPS arrived) taken at noon. Occasionally star sights were taken too.

          If you're manoeuvring close enough to something to be able to see it you're expected to use your eyes (plus bins) to navigate rather than a sextant.

  10. Colonel Mad

    Cocked up

    There is an Open University programme about the error of assuming your position is within the cocked hat, one of the people involved went on to lecture at BRNC

  11. This post has been deleted by its author

  12. Zenubi

    Not as easy as it used to be

    I did a lot of offshore / passage sailing (42ft sloop) back in the 80's. That's before GPS. We did have a stupidly expensive sat-nav but you had to look up tables to see a sats azimuth / position to use it - we also found we had to heave to so it basically never got used.

    We used dead reckoning and an occasional sextant fix but on a passage and out of shipping lanes this got sloppy quickly. That said we never actually missed our targets which were quite big like Barbados or Senegal.

    Inshore and out of Europe where Decca was in use we used RDF using aero beacons. This could be very accurate but I think these are gone now. We were also sensibly not above asking passing ships for a position check. Sometimes inshore ships / fishing boats would call us (VHF) with helpful info like "don't worry - you are still 20 nms from the rocks"

    I watch YouTube cruising sailor vids and see how easy it is now. No idea how many of them would cope without GPS.

    1. Nifty Silver badge

      Re: Not as easy as it used to be

      IIRC insects and maybe some birds can apparently detect the suns position through cloud via polarisation or maybe IR sensitivity. I would have expected by now that there is at least a daytime instrument that could do that too.

      1. GreyWolf

        Re: Not as easy as it used to be

        An instrument to detect the sun through clouds? The Vikings had that over 1000 years ago - it's called a sun stone

        https://en.wikipedia.org/wiki/Sunstone_(medieval)

      2. Manolo
        Pirate

        Re: Not as easy as it used to be

        A sunstone?

        https://en.wikipedia.org/wiki/Sunstone_(medieval)

    2. imanidiot Silver badge

      Re: Not as easy as it used to be

      Even today, relying solely on GPS is a surefire way to wind up (best case) in need of rescue or (worst case) in Davy Jones' locker. Anybody sailing open water should still know at least the basics of old school analog navigation.

      1. Zenubi

        Re: Not as easy as it used to be

        YES ! Also use your eyes - many areas that have significant weather often have new obstructions / sand bars not on any charts (yet).

      2. Aristotles slow and dimwitted horse Silver badge

        Re: Not as easy as it used to be

        Totally agree. I do have GPS and such like, but I think it's a lot more satisfying using old school methods.

  13. Santa from Exeter

    Jackspeak

    Scran isn't Jackspeak, as any good Scally will tell you.

    Good bit of scran that scouse, even if it is blind by now.

    Translation available if required.

  14. Anonymous Coward
    Anonymous Coward

    Oh those naughty Russians…

    “While no nation state has made a firm attribution of GPS disruption to any one source, Russia has an increasing presence in and around Syria.“

    Here we go again, default position of anything nefarious is to always blame Russia.

    There just so happens to be a highly technically advanced nation in the eastern Mediterranean which is regularly bombing its neighbours. Jamming GPS guided anti-aircraft systems would be logical for them to do.

    And let’s not forget our own British military base just a short hop away in Cyprus.

    And yes, it could be the Russians too. Or the Turks. Or the Greeks. Or the French. Or the Yanks.

    1. Cederic Silver badge

      Re: Oh those naughty Russians…

      Without wishing to enter a discussion on the source of the jamming, I'm intrigued at the idea of GPS enabled air defences.

      I perhaps foolishly assumed they work off relative positioning.

      1. Yet Another Anonymous coward Silver badge

        Re: Oh those naughty Russians…

        > I'm intrigued at the idea of GPS enabled air defences.

        When your target is helpfully broadcasting its GPS position and airline call sign over ADS it makes it much easier.

    2. John Brown (no body) Silver badge

      Re: Oh those naughty Russians…

      "And yes, it could be the Russians too. Or the Turks. Or the Greeks. Or the French. Or the Yanks."

      And radio direction finding has been a thing almost since the invention of radio. I would imagine that there will be people who know exactly when GPS spoofing is happening and the direction (at least) of the source(s)

      Even a my Garmin SatNav will give an approximation of where the currently visible sats are if I do a long press on the battery symbol in the top left corner of the screen. (admittedly that's using info from the sat, not directional locating.) So I'm sure military kit is a tad more advanced.

    3. SundogUK Silver badge

      Re: Oh those naughty Russians…

      Here we go again, default position of anything nefarious is ...and the anti-Semites are blaming Israel again.

      1. John Brown (no body) Silver badge

        Re: Oh those naughty Russians…

        Pointing out that Israel is likely also involved in GPS spoofing isn't being anti-semitic. Considering their known and proven "exploits" in the cyber world, I doubt anyone would be surprised it extends to other areas of tech too. Considering the attitudes both of some in their government and that of many of their neighbours, I'd fully expect them to have and use GPS jamming and spoofing capabilities. No go crawl back under your bridge!

  15. Aristotles slow and dimwitted horse Silver badge

    Indeed...

    "DR" or dead reckoning (i.e. course + speed + time) is slightly easier for a power vessel as they are less inclined to be influenced by tidal streams and leeway. For a sailing yacht however we also need to account for both of these, which when having done so ends up giving us the "EP" or estimated position. If near a coastline this might then be backed up by a 3 point fix.

    Other than that, I'm based near the Solent myself, so what a lovely week they must be having mooching about in the Channel what with this sunny calm spell we are having.

  16. Grunchy Bronze badge

    War with China becoming more likely

    It’s funny you should do this article right now, according to the experts they consulted at 60 Minutes Australia, probably the first thing China will do when they invade Taiwan is to burn down the global GPS system using fricken space lasers.

    https://youtu.be/kA2KaEKs1LA

    (When GPS quits worldwide — that was our warning.)

    1. John Brown (no body) Silver badge

      Re: War with China becoming more likely

      "the global GPS system"

      Did you mean the global Global Positioning System system? :-)

      I suppose they would try. Not forgetting the other three (at least) sat based navigation systems also already up there.

    2. imanidiot Silver badge

      Re: War with China becoming more likely

      Doing so would be an act of war against the US (Or at the very least taken that way). I doubt China would take that step. IF they invade Taiwan, they're going to want to have taken the island before the US can even react and get a carrier group into the area.

  17. Anonymous Coward
    Anonymous Coward

    Be surprised if there wasn't a sextant or two onboard the vessel. The Royal Navy seems like it's all about traditions.

    1. John Brown (no body) Silver badge

      Only in some instances. The Rum ration was abolished in 1970 :-(

      1. This post has been deleted by its author

      2. Yet Another Anonymous coward Silver badge

        I hope they at least kept the lash

  18. Ian Mason

    Tricorns

    In precision timekeeping, of the electronic variety, there is a technique known as the three cornered hat that allows you to take three clocks (as in signals with a defined but slightly varying frequency) and figure out the most likely estimate of the 'true' time and plot variances in the accuracy of the three individual clocks against the 'true' time. Without knowing at the beginning which clock(s) are 'right' you can work towards knowing the correctness of all of them. For those who care, it's done by comparing covariances of each pair of clocks with the third. One place it can be used is in figuring out the 'true' time according to GPS and hence your 'true' position.

    The mathematics of the three cornered hat technique ought to work just as well on three bearings, as long as you took continuous bearings to give yourself the time series that the technique requires. Not exactly practical unless they are either radio bearing that you can automate, or you've got three Ensigns you want to keep busy and out from under proper officer's feet. I just found the parallel with the 'cocked hat' and the similarity in names quite intriguing.

  19. Anonymous Coward
    Anonymous Coward

    GPS.....It really depends where you are using it..................

    There are unsubstantiated claims that someone near the Gulf of Hormuz is broadcasting fake GPS.

    Some ships in the area (you know...actually floating in the sea) have seen GPS locations reported as hundreds of miles inland!

    Please tell me that sextants, sightings, compasses and paper maps are a thing of the past!!!!!!!

    I suppose this sort of thing could happen anywhere......say in the English Channel.....

    1. Phil O'Sophical Silver badge

      Re: GPS.....It really depends where you are using it..................

      I suppose this sort of thing could happen anywhere......say in the English Channel.....

      If governments start trying to recoup fuel duty by road pricing I daresay we'll start seeing it on the M25, or the autoroutes & autobahns in Europe.

  20. Mike 137 Silver badge

    Deja vu

    An exercise like this was done by Trinity House some time back (I forget when exactly but around 20 years ago). They sailed a trawler up and down past Grimsby and jammed its GPS signal (awfully easy to do). There were two interestig findings: [1] at one point it broadcast that it was doing around 200 knots over land, and [2] the "fallback" radar navigation system didn't work because it used the GPS clock for synchronisation.

    1. Electronics'R'Us Silver badge
      Facepalm

      Re: Deja vu

      Some years ago when I was using public transport (trains) for my commute from east Kent to the Medway towns, there would be the occasional time when the train pulled into a station and the doors would not open for quite a while.

      It turned out that the train onboard GPS had to agree that the train really was in a station to let the driver open the doors as normal and if it had lost the signal (or position which is the same thing really) the driver had to manually override the system (yes we really are at a station) to open the doors.

      The older trains on that route still use it - not sure if the newer ones still do (but it would not surprise me if they did).

      Someone with a GPS jammer could cause havoc on that line.

  21. Richard Pennington 1

    Many years ago, I went on a couple of Inter-Rail holidays around Europe with my brother. Essentially, we had the run of the trains all around Europe for a month. Coming to a new city, we always had the same routine: pick up the local map, visit the local tourist information centre, and see what we could find. Mostly, this worked.

    But at Skopje, we hit a problem. We picked up a map at the station, went out through the station entrance, turned left ... and we were immediately lost. We were walking out of town, and that should not have been happening.

    It turned out that the station was brand new (in its first week of service) and the map showed the location of the old station.

  22. Alpharious

    Laughs in SPS-55

    It's not the GPS that they care about during a sea and anchor, it's the navigation radars. THOSE are far more important then the gps. Also the radar indicators as well.

  23. Fruit and Nutcase Silver badge
    Coat

    AIS

    I was looking at the track of HMS Severn since she left port on Monday...

    after some repeated runs between Torquay and Plymouth, they head over to the Channel Islands, and she is currently near Guernsey. Now, let your imagination run riot on the tracks that were done to the north of Sark...

    I used https://www.myshiptracking.com/, and, at the time of writing, selected the 4 day track history

  24. Jim Whitaker
    Coat

    Pedantry - Picture caption

    It's not THE HMS Severn, it's HMS Severn or, depending on the context, the Severn.

  25. Conundrum1885

    Jusrt wait

    Until there is a big solar storm knocking out GPS at the same time as a magnetic field anomaly.

    One day soon the poles WILL flip and for a brief time navigation will be problematic.

    Its been suggested that something very much like this might have done for MH370.

    The working hypothesis is that there happened to be a brief magnetic spike in the area which has

    in fact been reported before by both shipping and aviation.

    By sheer coincidence one of the passengers had a faulty phone that "hooted" on the GPS L1 and L2

    bands and this unfortunately coincided with the magnetic anomaly causing the plane to fly in effective

    circles until it ran out of fuel.

    Normal communcations being knocked out may well have been a short in the wiring: likely the

    transmit side went bad or off frequency but reception was still possible.

    Similar issues have been reported before with older equipment more susceptible to certain types of

    faults.

  26. Binraider Silver badge

    Keeping up traditional practises and cross referencing is a great way to stay sharp and keep your options open. Running a specific exercise for this is perhaps an indication that workloads reductions and convenience of "GPS" perhaps are demonstrating slightly too much reliance on said tools.

    Automation clearly has a very, very long way to go...

    Knowing how to use a slide rule is still a useful capability, for the day after that EMP bomb takes down your pocket calculators.

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