back to article Brit boffins build 'quantum compass'... say goodbye to those old GPS gizmos, possibly

British boffins have developed a self-contained and tamper-proof "quantum compass" that doesn't rely on GPS signals to provide a highly accurate measure of where it is in the world. The compass is a quantum accelerometer that is capable of measuring tiny shifts in supercooled atoms and so calculate how far and how fast the …

  1. onefang Silver badge
    Boffin

    It's not a compass.

    It only measures how far it moved, and currently only on one plane. Even once they get it up to three planes, as planned, it still only tells you how far it moved. You need another bit of information, where you started from. No idea how it works when rotating it in place, does it even notice? Though I guess having more of them and doing some calculations tells you if it's rotating. You still need to know which direction you where facing to start with. Not to mention that errors add up over time on these sorts of devices, though perhaps the error is really tiny, it wasn't mentioned.

    You can get that missing info from, oh I dunno, a GPS and a real compass I guess. Or a surveying point and it's records.

    Still, it's cool technology.

    1. Ken Hagan Gold badge

      Re: It's not a compass.

      A surveying point in the home harbour, probably made of concrete, is difficult for the enemy to block or interfere with.

      1. h4rm0ny

        Re: It's not a compass.

        Additionally, the threat of disrupting or hacking GPS that this addresses isn't just a theoretical one. This is how the Iranians captured a US drone some years ago. They flew another plane over the top of it and broadcast fake GPS signals to it causing it to think it was somewhere else and land.

      2. Fungus Bob Silver badge

        Re: It's not a compass.

        "A surveying point in the home harbour, probably made of concrete, is difficult for the enemy to block or interfere with."

        A torpedo could probably render it useless...

    2. David M

      Re: It's not a compass.

      onefang: your question, "No idea how it works when rotating it in place, does it even notice?", is answered in the video, where it says that they plan to build a version that can measure three orthogonal accelerations, and three rotations.

      It's a shame they don't give any clues about the accuracy, or predictions about the timescale to make something commercially viable,

      1. onefang Silver badge

        Re: It's not a compass.

        "onefang: your question, "No idea how it works when rotating it in place, does it even notice?", is answered in the video"

        Ah, I skipped watching the video. Back when I only had 30 GBs of Internet a month I would generally skip random videos, to conserve bandwidth. Now that I no longer have that problem, I still have that habit. Slowly breaking the habit.

        1. Anonymous Coward
          Anonymous Coward

          Re: It's not a compass.

          I didn't watch the video either but 3-axis accelerators are everywhere these days.

          1. Anonymous Coward
            Anonymous Coward

            3-axis accelerators are everywhere

            They are, but not accurate enough (long term) or with enough resolution to use for an intertal platform that doesn't use something else (e.g. gps) to compensate for drift.

            1. Anonymous Coward
              Anonymous Coward

              Re: 3-axis accelerators are everywhere

              They have been using compensations not relying on GPS for decades and it has been used with very good results in nuclear submarines that stay submerged for weeks if not months.

            2. Blank Reg

              Re: 3-axis accelerators are everywhere

              That depends on your time frame. There are extremely accurate accelerometers used for tracking the movement of soldiers indoors. But that only needs to be accurate for a matter of hours, I don't know how far off it would be after a few days, though I expect it would be adequate for navigating a boat or plane.

          2. Yet Another Anonymous coward Silver badge

            Re: It's not a compass.

            Yes it is a compass.

            A gryo left undisturbed will point in the same direction as the Earth turns. It tells you directly where the true north pole is. It's how you get a heading underground if you wanted to eg. dig a tunnel to France

            1. h4rm0ny

              Re: It's not a compass.

              It's how you get a heading underground if you wanted to eg. dig a tunnel to France.

              Why couldn't you use a regular compass to get a heading underground?

              1. onefang Silver badge

                Re: It's not a compass.

                "Why couldn't you use a regular compass to get a heading underground?"

                Depends on what you are digging through or near I guess. Or possibly digging with, that huge metal tunnel digger might be all the compass ever points at.

            2. disgustedoftunbridgewells Silver badge

              Re: It's not a compass.

              France? Why would anybody want to dig a tunnel to bloody France?

              I read that when they dug the chunnel they were only inches off course by the time they met up in the middle, which is pretty bloody impressive if you ask me ( I blame the french for those few inches, naturally ).

              1. DJO Silver badge

                Re: It's not a compass.

                Why would anybody want to dig a tunnel to bloody France?

                Maybe they were digging a tunnel from France.

              2. onefang Silver badge

                Re: It's not a compass.

                "I read that when they dug the chunnel they were only inches off course by the time they met up in the middle, which is pretty bloody impressive if you ask me ( I blame the french for those few inches, naturally )."

                Where the diggers from the English side using inches, and the French side using centimeters?

              3. JassMan Silver badge
                Trollface

                Re: It's not a compass. @disgusted of tunbridgewells

                You can't blame the french for a few inches. If they were at fault it would have been a few centimetres. The fact that the error was is in inches implies that if you can't trust the original positioning, why should you trust the check any further. The only thing known for sure is that there were 10s of millimeters difference between the 2 terminations, since engineers work in SI units as opposed to "imperial" or "metric". Still it was a pretty bloody impressive feat to dig that far without line of sight from one end to the other. Shame that once Brexit takes effect it will take 10 times as long to get to checkin and through customs as it will to get through the tunnel.

              4. Red Bren
                Coat

                Re: It's not a compass.

                If they were off course by inches, then that's the fault of the British. If they had been off course by centimetres, then it would be the fault of the French!

              5. Cookie 8

                Re: It's not a compass.

                If the French were off, wouldn't it be by a few centimetres?

          3. Uffish

            Re: "3-axis accelerators are everywhere these days"

            And most especially, they say, in a nice hot cup of tea.

      2. Anonymous Coward
        Anonymous Coward

        Re: It's not a compass.

        It's a shame they don't give any clues about the accuracy, or predictions about the timescale to make something commercially viable,

        The MoD are funding it, so I'll guess never, even if it turns out to have no military applications.

        1. macjules Silver badge

          Re: It's not a compass.

          The MoD are funding it, so I'll guess never, even if it turns out to have no military applications.

          Just so long as it runs on Windows ME or even Windows XP then it will be fine.

          1. Michael Habel Silver badge

            Re: It's not a compass.

            Well at least its not running that bloddy Vista thing (Shakes angy fist!).

          2. BillG Silver badge
            Megaphone

            Galileo, Galileo

            ...Europe made it clear that following Brexit, the UK would no longer gain secure access to Europe's new Galileo GPS system despite years of assisting in the system's development and deployment.

            I don't know the history of Galileo GPS, but this seems spiteful for the EU to treat the UK like this.

      3. veti Silver badge

        Re: It's not a compass.

        My guess is that "commercially viable" will be available about the same time as fusion power.

        There's a certain type of boffin - and for reasons that are pretty obvious when you think about it, they're often a type that loves working on govt-funded R&D projects - who think that once they've demonstrated an effect in principle, everything after that is just boring donkey-work. This is the demonstration-in-principle, now it's "just" a matter of bolting six of the things together, reducing space, weight and power requirements by a factor of 10,000, and manufacturing costs by a thousand times that, and fixing all those annoying glitches that they still don't fully understand but managed to work around for demo purposes...

        How hard can it be? - as they said about fusion, back in the '70s.

        And then someone will have to interface it to Android and iOS. That's where things will really get tricky.

        1. Yet Another Anonymous coward Silver badge

          Re: It's not a compass.

          >My guess is that "commercially viable" will be available about the same time as fusion power.

          Depends what you mean by commercially viable.

          To replace the 10c mems accelerometer in your phone = no

          To replace the set of $25,000 laser fog gyros in a submarine/aircraft = not so hard

        2. jake Silver badge

          Re: It's not a compass.

          "And then someone will have to interface it to Android and iOS. That's where things will really get tricky."

          Nah. That's the easy part. Industrial controllers are a known thing.

          1. Dave 126 Silver badge

            Re: It's not a compass.

            The concept (and practice) is called Dead Reckoning and is used on submarines. However there is no way to avoid Cumulative Errors which limit its accuracy over time. A submarine is moving relatively smoothly compared to a phone in someone's pocket, which is why dead reckoning can't practically be used to augment a phone's GPS (for navigating with a building, for example)

            1. Hurn

              Re: It's not a compass.

              The original concept was (is) called SINS: Ship's Inertial Navigation System

              accelerometers sense movement along all 3 axes and track displacement

              It is not Dead Reckoning, but a technological replacement. From over 50 years ago.

              The main difference between SINS's gyroscopes and quantum "compass" is sensitivity (and need for extreme cooling).

        3. Teiwaz Silver badge

          Re: It's not a compass.

          And then someone will have to interface it to Android and iOS. That's where things will really get tricky.

          Oh, good, the app makers can use the 'because it's quantum' excuse as to why the app will only work when given every permission under the sun, including inside leg measurements in realtime.

    3. katrinab Silver badge

      Re: It's not a compass.

      Surely you have three of these devices, with three different starting points for their movements, then you can triangulate where you are?

    4. e_is_real_i_isnt

      Re: It's not a compass.

      They need to subtract out the rotation of the Earth around its axis, the movement of the Earth around the center of mass between the Earth and the Moon, the movement of the Earth around the Sun, and the Sun around the galaxy. It should be easy.

      1. Sampler

        Space?

        Would this work in space? I mean, once you're outside the GPS satellites it must be pretty tricky to work out where you are, star charts can be so accurate but you'd have to have been there before to know where you are and how to get back?

        But, if you know you've moved A miles on the X axis, B miles on the Y axis and C miles on the Z axis from Earth, you know how to get back.

        1. jake Silver badge

          Re: Space?

          "but you'd have to have been there before to know where you are and how to get back?"

          Nah. Just find a handful of quasars and/or pulsars and do a little easy trig. You can pinpoint yourself pretty much anywhere in known space. (The real known space, not the scifi version.) On the other hand, getting home might take a little more energy than remembering basic High School maths.

          On the gripping hand, I wouldn't mind being on the first ride that would require the above. It would probably be either boring as shit, or the entire crew would be dead ... but what a story to tell if you survived!

        2. Deltics
          Coat

          Re: Space?

          Which then just leaves the question of figuring out where Earth is once you've returned to the spot it was at when you left (assuming that you can either compensate for the expansion of The Universe, the duration of the trip is such that this expansion doesn't amount to a significant drift or that there is no such expansion after all so it simply doesn't figure).

      2. Snapper

        Re: It's not a compass.

        Could you use a.......oh, I dunno, a big calculator for that?

    5. Anonymous Coward
      Anonymous Coward

      Re: It's not a compass.

      "Pirates are now sophisticated enough to cause disruptions to ships, and lure them to rocks or take over and board them, by disrupting GPS,"

      Proper military systems use navigation systems that contain an inertial navigation system (INS) and GPS. INS's measure the accelerations the object has undergone form it's last known position & calculate where it is. (Many have pointed out this "quantum compass" is merely a single axis INS that supposedly has a quantum noise limited integration error.) INS's are not subject to external influences like jamming. They are however, limited by the accumulation of what are essentially round-off errors (or LSB resolution) in the acceleration measurements, and that results in an accumulated position error called "integration error". That accumulated position error gets larger over time and in the course of several hours can be large enough to matter. So top notch military navigation systems use both GPS & INS, and detect GPS jamming by watching whether the GPS reported position exceeds the INS reported position by an amount significantly larger than the INS integration error. (At which point, if say it's a drone, you can have it head towards home using the INS until it clears the GPS interference area, which it will by the time it's near it's home base.)

      1. DropBear Silver badge

        Re: It's not a compass.

        "Many have pointed out this "quantum compass" is merely a single axis INS that supposedly has a quantum noise limited integration error."

        Exactly. This thing isn't any more magical than any inertial positioning system, and it must be subject to accumulating error exactly just as all the others are. Where it may indeed differ substantially is the level of that drift, which may really be astonishingly small for all we (don't) know, much like atomic clocks aren't absolutely precise either*, only mind-bogglingly precise.

        * we could conceivably keep on splitting hairs about the second being defined as a fixed number of atomic oscillations therefore these clocks being infinitely precise and zero drift by definition, but I have a hunch that any practical implementations might just conceivably introduce some further sources of error, no matter how small, making atomic clocks still less than ideally precise.

      2. Brewster's Angle Grinder Silver badge

        Re: It's not a compass.

        "...that supposedly has a quantum noise limited integration error."

        You want measurements accurate down to the Planck scale? Jeez, you guys are hard task masters.

        Seriously, I don't know what they say in the video, but you can accumulate an error of hundreds of thousands of atomic diameters and still be accurate to less than a millimetre.

    6. Apprentice

      Re: It's not a compass.

      Oh, I guess they haven't thought about all that, I guess they should have consulted Joe Public first as clearly you know better than these well educated scientists. Back to the drawing board it is then.

    7. diodesign (Written by Reg staff) Silver badge

      Re: It's not a compass.

      Nah, we're happy with quantum compass. It pretty much explains why in the article. The eggheads call it a quantum compass. It's not a traditional compass. It's a quantum compass.

      C.

    8. Alfred

      Re: It's not a compass.

      "You need another bit of information, where you started from."

      OMG, you've spotted the fatal flaw. Unless... unless... yes, it's just possible that someone could make a note of where they're starting from.

  2. Ken Hagan Gold badge

    "A GPS signal could be spoofed or blocked for instance. When you're thinking about nuclear submarines, it usually best to consider the worst."

    Actually, when you are thinking about submarines, you probably don't want to be using a GPS in your navigation system. A blocked signal is "what happens", not "the worst", because sea-water is basically impenetrable to EM waves.

    And if you are thinking about ballistic missile subs, I hope you've factored into your thoughts the near-certain fact that in just a few years the enemy will be able to track those with one of their mass-produced robotic drones and so their locations while out on patrol will cease to be "totally undetectable" (as they have been for the last half-century or more) and instead be "posted on the internet, by the enemy, just because they can, for shits and giggles".

    1. Spamfast Bronze badge

      Probably won't even need drones - the Chinese may have magnetometers sensitive enough to detect the hull of a sub from the air.

      https://www.newscientist.com/article/2144721-chinas-quantum-submarine-detector-could-seal-south-china-sea/

      Add air-launched torpedos and there goes your nuclear deterrent.

      Remind me again why the UK still insists on paying the US vast sums of money for sub-based ballistic missiles that we can't even launch without getting permission from the White House?

      1. Blane Bramble

        "that we can't even launch without getting permission from the White House?"

        Because that last bit is wrong.

      2. The Man Who Fell To Earth Silver badge
        Boffin

        @ Spamfast

        Superconducting Interference Devices (SQUIDs) are quantum noise limited magnetic sensors & have been in use for submarine detection by the US & Russia since the 1970's.

      3. SkippyBing Silver badge

        'the Chinese may have magnetometers sensitive enough to detect the hull of a sub from the air.'

        Aww bless, only a few decades after everyone else then.

        https://en.wikipedia.org/wiki/Magnetic_anomaly_detector

      4. Anonymous Coward
        Anonymous Coward

        'Air Launched torpedoes'?

        Nah, too subtle, battlefield nuke dropped in, submarine pancakes.

    2. Phil O'Sophical Silver badge
      Coat

      be able to track those with one of their mass-produced robotic drones

      Until the navy starts filling the oceans with mass-produced decoy submarine drones for them to track, that is.

      1. Anonymous Coward
        Anonymous Coward

        Until the navy starts filling the oceans with mass-produced decoy submarine drones for them to track, that is.

        UK Navy? Rather optimistic assumption of capability I am afraid. In order to simulate a sub well and be viable as a decoy the drone should be able to run under water for a sufficient amount of time and/or be suitably sized for the decoy to be difficult to distinguish from the real thing. That requires compact reactor or high power thermoelectric isotope battery technology. A small conventional battery powered drone will be immediately distinguishable on active sonar. While a sub captain will not use active echolocation unless they have no choice as it will give away their position, an unmanned drone will have no such qualms. In fact it, is likely to use that on purpose as a part of psychological warfare against the sub crew: "We see you all the time, we have a weapon's lock all the time and you do not stand a chance of reacting before we blow you up".

        Neither small reactors, nor high power thermoelectric is in the works in the UK. Neither one is in the works in the USA. They are however (both of them) in production in Russia now and according to the Internet rumour mill in final testing stages in China. The west is ~ 10 years behind here.

        1. Anonymous Coward
          Anonymous Coward

          > A small conventional battery powered drone will be immediately distinguishable on active sonar. While a sub captain will not use active echolocation unless they have no choice as it will give away their position, an unmanned drone will have no such qualms.

          If a drone sub uses active sonar then it is immediately detectable by the anti-drone-sub drone sub. (Which only has to prevent the drone sub from being able to fire its torpedoes accurately which is easily achieved by attaching a buoyancy balloon, filling it with air and dragging the thing to the surface.)

      2. Anonymous Coward
        Anonymous Coward

        > "Until the navy starts filling the oceans with mass-produced decoy submarine drones for them to track, that is."

        I would bet they've had those for years already.

    3. Yet Another Anonymous coward Silver badge

      If you have a balistic missile sub then GPS is useless. All your GPS satelites have already been taken out by the massive thermonuclear first strike of the other guys - unless you were intending to shoot first.

      It's why ICBMs have star trackers not GPS.

      1. h4rm0ny

        unless you were intending to shoot first.

        Less of a problem than you might hope. The USA has been pursuing a policy of Nuclear Primacy for some years now. Nuclear Primacy is the capability to first strike so hard there cannot be an effective response. Long, but good, article on this:

        https://www.foreignaffairs.com/articles/united-states/2006-03-01/rise-us-nuclear-primacy

      2. Sampler

        subs

        Lot of people talking about subs using GPS - and the article too, however, my watch loses GPS signal in mere millimetres of water. I'm not suggesting the military signals the subs are using are the same as the ones I'm using to log my triathlon, but, they've got to behave to the same physical laws, and if a little water's enough to block one, then a few leagues should impact the other?

        1. DropBear Silver badge

          Re: subs

          To be fair to the subs, just because you don't have GPS signal while diving (relying on your cutting edge dead-reckoning rig instead) and just because the satellites might no longer be there when you surface it doesn't mean you're not going to take the opportunity to get a position fix to recalibrate your inertial reckoning whenever you're on the surface and you do see the sats. Corroborating it with sextant data and stellar observations in case of the slightest suspicion of foul play, no doubt.

        2. Hey Nonny Nonny Mouse

          Re: subs

          You might also consider that the antenna used in your watch is ridiculously undersized and inefficient, you wouldn't want a surveying GPS antenna on your wrist.

      3. OnlyMortal

        So Hollywood is a goner then :-)

    4. Cragganmore

      "... the near-certain fact that in just a few years the enemy will be able to track those with one of their mass-produced robotic drones and so their locations while out on patrol will cease to be "totally undetectable..."

      The ocean's still a big place... a very big place. Unless you put a nuclear reactor on board an underwater drone it won't be on station long enough to have any chance of searching - let alone travelling fast enough to keep up with a nuclear powered submarine. And I don't buy the Russian propaganda around nuke-powered drones. (I'm not talking about nuclear warheads - which I know they've also talked about - and I hope to god they would trust the thing not to go wrong). Why else would they mention a mother-ship concept to launch a nuclear drone as it would have the endurance and speed to traverse from a Russian base. Plus, if you realistically wanted to put develop a reactor small enough and autonomous/reliable enough to stick on board an underwater drone it would probably cost something approaching the costs of building another small SSN. So what's the point?

      Physics ultimately gets in the way of making oceans 'transparent' - things will get incrementally better in terms of detection, but conversely folk will find ways of making things quieter and find better ways of countering. Classic definition of an arms-race :)

      1. Charles 9 Silver badge

        But it's still a thing going through the water. It will inevitably interfere with something (the earth's magnetic field if nothing else), and there WILL be ways of picking it out. Put it this way. Has there been any significant advance of stealth technology since multistatic and passive radar (which BTW is ALSO much tricker to detect and defeat, especially in passive radar which uses ambient radio waves) has made even today's state of the art practically useless if not counterproductive?

  3. Mr Lion

    GPS accuracy

    "A phone's GPS accurate to roughly 15 feet, although military GPS devices can be accurate to centimeters"

    I don't think this is any longer true. As I understand it, GPS signals were originally designed to be available in two flavours - a civilian one, that was made deliberately less accurate, and a military one, that had the *real* data. The reason for this was - the US military didn't want to be giving foreign powers the ability to target their cruise missiles more effectively.

    Now when the gulf war came, military GPS devices were in very short supply. Several soldiers received gifts of yachting units from family and friends and were using them to navigate through Iraq - as a result of this the military decided to broadcast the civilian signals at the same accuracy as the military ones.

    1. onefang Silver badge

      Re: GPS accuracy

      "The reason for this was - the US military didn't want to be giving foreign powers the ability to target their cruise missiles more effectively."

      I always wondered about that. Missing with a nuclear weapon by 15 feet likely isn't a problem for the people delivering it. Still gonna be a big problem for the people it was aimed at. Then there is the modern "mount a camera on it and steer it for the last stretch of flight". Oh look, there's the front door to the White House on the right, guess they moved it.

    2. hugo tyson
      Coat

      Re: GPS accuracy

      You're conflating turning off selective availability (SA), which they did 'cos of various gulf wars, and making access to the military signals available. They didn't do the latter.

      SA dithered the civilian signals to cause a wandering inaccuracy of several hundred meters. It is defeated by using a fixed ground station to work out the current offset, and delivering the difference data to receivers - this is Differential GPS. So people were working around it anyway.

      With SA turned off as it has now been for decades, the civilian signals are still only accurate to a few metres 'cos the chipping rate of the PRN code (orthogonal CDMA code) is 1023 chips per millisecond, so each chip is about 300 metres long. Curve fitting to multiple correlation results gives timing to fractional chips but it's inherently noisy - so you might get actual results accurate to 10s of meters (30ths of microseconds). Solving with many satellites reduces the combined error, sure, but it's stlll meters not centimeters.

      AIUI the military signal has a faster chipping rate with longer PRN sequences and so it's inherently more accurate because the basic unit of "knowing when the signal is" which you have if you're managing to track the signal at all, can be not about a microsecond = 300m, but a fraction of that. It's a 10th of that - 30m - in the old versions, and it's not in wikipedia for the latest actually secret stuff. I only ever worked on civilian receivers, so had no need to look at the mil stuff.

      1. Richard Simpson

        Re: GPS accuracy

        The military signals are also transmitted on a second quite different frequency (about 1.2 GHz if I recall) and this is another reason for their enhanced accuracy.

        Atmospheric refraction affects the accuracy of GPS because it affects how long the signals take to pass through the atmosphere. Civilian GPS has a model to correct for that, but it is based on an average atmosphere. To go a step up in accuracy you need to know the state of the atmosphere right now and that depends on things like the sun. The atmosphere affects the two different GPS frequencies (civilian and military) differently and by measuring the difference you can get a better estimate of the current atmospheric refraction and improve your estimate of position.

        1. Mage Silver badge

          Re: GPS accuracy

          Also solar flares and laser weapons to disable satellites?

          Inertial navigation started with gyroscopes in 1930s. Needed historically near poles before GPS and in space before using Pulsars and automated star sighting.

          1. This post has been deleted by its author

        2. Anonymous Coward
          Anonymous Coward

          Re: GPS accuracy

          You don't need civilian and military frequencies to do that. These days you can use civilian L1 plus civilian L5 and determine the ionospheric propagation delay which is what you need to correct for variable delays. Civilian cell phones have L5 capability. Broadcom makes a chip that does this. It is unclear if present chip sets apply a correction but it is quite within reach.

          1. Dave 126 Silver badge

            Re: GPS accuracy

            BAE also have systems to compile maps in real-time of stationary FM transmitters and other sources of RF, so a drone can tell if the GPS signals are being spoofed.

            There was a Reg article about it.

      2. John Smith 19 Gold badge
        Unhappy

        "AIUI the military signal has a faster chipping rate with longer PRN "

        Correct.

        IIRC the Civvy chipping rate is 1024 and repeats about 1024 times a second (easy to lock) and the mil spec is a whole different beast, which is sent at 10x the bandwidth and cycles over a time of something like a week

        Military cycle lock is achieved by clues hidden in the "Almanac" that is downloaded at 50bps, probably (but necessarily) in the stuff that's repeated on every 300bit long "page."

        During a series of articles on a Transputer based GPS system the author said the trick is to design a "Synthetic" common chipping code from each of the ones used on the GPS sats so when you run it against the incoming data it pull all the visible GPS sat signals at once. They were very vague on wheather this should be a sum, an And, an average or what this code should be.

        Should make an interesting study for someone, given processors with 10MIPS are very much more common than in the late 80's.

        1. hugo tyson
          Go

          Re: "AIUI the military signal has a faster chipping rate with longer PRN "

          Civilian GPS really is 1023 chips/cycle so the PRN shift-and-feedback 10-bit register never has to go through zero, 'cos if it did it would stay on zero. Repeating every millisecond (nominally, subject to doppler and clock errors).

          About the mil signal, the really long cycle time is for security only - makes it really hard to find unless you have pre-loaded tracking data somehow, from that encrypted almanac as you say. But that aspect doesn't add at all to accuracy: only a higher chipping rate can do that, which as you say is 10x the civvy version. But only 10x, so each chip is ~30m. You might get 30cm correlation data out of that.

          The ionospheric correction - the naive algorithmic one (ramps up linearly from 0600 local to noon, ramps down from 1800 local to midnight, times cosine something I think) in civilian GPS standards docs anyway - is under 10m, ISTR it being 5m to 7m max usually. So the naive model is good for a system whose overall accuracy is 5-10m anyway. Interesting that of course the mil system needs better Iono corrections from the ephemerides (I guess) 'cos its native accuracy is higher.

          But it can never be reliably that accurate. I had a GPS antenna on the windowsill of an office about 15m up. It saw half the sky OK. I generally got accurate positions, being of course the position of the antenna not my computer connected to it. But when it rained, a sloping roof across the road turned into a radio reflector and I could "see" much of the other half of the sky too. Great! you might think, but it saw the new sky with extra path length, since the new signals went across the street and back extra. So my positions were solved for about 10m away, in the middle of the road. Ain't nuthin' you can do to prevent that sort of situation short of rejecting some signals in the solver - but which ones? - whatever your chipping rate and correlation accuracy, it can still be fooled by reflections.

          1. DropBear Silver badge
            Trollface

            Re: "AIUI the military signal has a faster chipping rate with longer PRN "

            So were you measuring continental drift, or just wanted the ultra-stable frequency reference like the rest of us...?

          2. John Smith 19 Gold badge
            Unhappy

            "from that encrypted almanac as you say. "

            "Encrypted" is putting it a bit highly.

            The GPS standard dates from a time when processing was very expensive. Consequently it incorporates lots of tricks designed to simplify the processing task on the end users processor (this is at a time when the Z80 was considered pretty impressive, if you couldn't get an 8088, and the 68000 was still on the horizon).

            This results in lots of "funny" units for different parameters, like fractions of the Earths diameter, or the eccentricity of the Earth as an oblate spheroid. The */ operators in Forth are a similar device.

            Fast forward 40 years and few people have any idea how to use this stuff.

            As to where the multi path problems that's where phased array techniques with multiple antennas come in handy. On Sounding rockets and ELV's they have also been used for attitude sensing.

            Now, where is/are the key(s) to allow you to lock to the Military grade code? I'd guess anywhere marked in the standard "reserved," or possibly not.

      3. Sweep

        Re: GPS accuracy

        I'll take your word for it!

    3. Lars Silver badge
      Happy

      Re: GPS accuracy

      The Wikipedia has this on accuracy for Galileo: 1 metre (3.28 feet) (public), 1 cm (encrypted).

      15 feet (4.6 metre) is clearly too pessimistic for GPS.

  4. Pascal Monett Silver badge

    Impressive kit

    Unfortunately it seems to be the size of the engine in a car. It'll have to be squeezed down to half a brick if they want to use it in vehicles, and you can forget about having that in a phone before a few decades at least.

    But still, interesting kit.

    1. Anonymous Coward
      Anonymous Coward

      Re: Impressive kit

      "It'll have to be squeezed down to half a brick if they want to use it in vehicles, [...]"

      A book published in 1940 covered the history and technology of electric clocks. The final chapter covered the latest cutting edge method which it confidently said would only ever exist in a laboratory owing to its immense bulk. That was the quartz crystal oscillator.

      1. DropBear Silver badge

        Re: Impressive kit

        I seem to recall having seen atomic clocks of matchbox size being advertised not long ago (right here on El Reg IIRC). So, yeah..

    2. SkippyBing Silver badge

      Re: Impressive kit

      'It'll have to be squeezed down to half a brick if they want to use it in vehicles'

      Have you seen how big a nuclear submarine is? Plenty of room for one of those bad boys, just take the shower out.

    3. John Brown (no body) Silver badge
      Coat

      Re: Impressive kit

      "It'll have to be squeezed down to half a brick if they want to use it in vehicles, "

      Once the manufacturing has been outsourced to a Chinese factory, expect a surge of cheaper, smaller models to suddenly appear on the market.

      The one with Mandarin for Dummies in the pocket ----------->

  5. Neil Barnes Silver badge
    Coat

    Quantum navigation

    So it knows *where* it is, but it doesn't know how fast it's going? Or the other way around?

    I'd get my coat, but I can't find it.

    1. Commswonk Silver badge

      Re: Quantum navigation

      I'd get my coat, but I can't find it.

      That's cos you lent it to some chap called Heisenberg, and he in turn passed it some Schrödinger fellow because he wanted to see if it was both raining and not raining at the same time.

      Or something...

      1. Doctor Syntax Silver badge

        Re: Quantum navigation

        "passed it some Schrödinger fellow because he wanted to see if it was both raining and not raining at the same time."

        And he left it in a box where it's folded up or not folded up.

        1. Mephistro Silver badge

          Re: Quantum navigation

          I'm pretty sure the cat has already unfolded the coat to use it as a bed.

          Or not.

          1. jake Silver badge

            Re: Quantum navigation

            Nah. The Whippet got there first.

            Quantum mechanics is not only stranger than you imagine, it's stranger than you can imagine. (apologies to many giants who came before all of us).

    2. Chemist

      Re: Quantum navigation

      "So it knows *where* it is, but it doesn't know how fast it's going? Or the other way around?"

      But if it has a fixed position at time T and then T+x ( where x might be quite small) then the direction and travel are a trivial calc. That's what my hand-held GPS ( 14+ years old I'd guess) has always done.

    3. LDS Silver badge

      "So it knows *where* it is, but it doesn't know how fast it's going?"

      Only if you're looking at it...

    4. DropBear Silver badge
      Trollface

      Re: Quantum navigation

      I'd get my coat, but I can't find it.

      Admit it, that's only because it has a camo pattern and it's just too good...

  6. David Given

    Isn't this inertial guidance?

    ...which has been tried for years, hasn't it? And has always fallen down due to error compounding in the integration process, where cumulative errors grow very quickly until after about forty-five seconds your guidance system thinks you're on Mars? (Disclaimer: if you are *actually* on Mars, it'll think you're on Earth.)

    It sounds like the original press release used the word 'quantum' a lot. How would this help?

    1. ThatOne Silver badge

      Re: Isn't this inertial guidance?

      > It sounds like the original press release used the word 'quantum' a lot. How would this help?

      To reassure people with the classic "Quantum = Magic" principle... :o)

      "But inertial systems tend to drift over time" - "Yes, but this is a quantum one!"

      Now increasing the resolution might indeed have helped somewhat, the question remains "how much", and "at what cost". I guess there are probably several years before this idea is ready to leave the labs as anything else than a technology demonstrator. It's a cool idea (laser-cooled even!), but still just a lab success.

    2. Charles 9 Silver badge

      Re: Isn't this inertial guidance?

      "And has always fallen down due to error compounding in the integration process..."

      Which as I recall was due to the lack of precision in the initial measurements. But with this, your initial measurements are MUCH more precise, meaning the compound effect is greatly reduced making the final result much more reliable.

      What piques my curiosity is just HOW sensitive these instruments really are. I mean, are they sensitive enough to measure astronomic motion like that of the Earth's rotation and revolution in space (which are both curved and therefore will always have an acceleration invovled)?

      1. Yet Another Anonymous coward Silver badge

        Re: Isn't this inertial guidance?

        > mean, are they sensitive enough to measure astronomic motion like that of the Earth's rotation

        They always have been gyrotheodolite

        Making an accurate INS that is fixed is easy, making one accurate on a large smoothly moving submarine or aircraft is relatively easy. Making it accurate in a phone bouncing around in your pocket is tricky

        1. Charles 9 Silver badge

          Re: Isn't this inertial guidance?

          Are you sure you didn't mean a gyrocompass, which at least works in a mobile setting (gyrotheodolites need to remain stationary)?

          Anyway, what I'm wondering is if the increased precision in this experimental setup might be spoiled by "noise" factors such as accounting for the earth's celestial movement, which also produces measurable forces.

          1. Yet Another Anonymous coward Silver badge

            Re: Isn't this inertial guidance?

            Fundamentally the same thing, gyrotheodolites are probably the main use/form of gyrocompasses

            The north seeking drift is fairly slow (15deg/hour) and absolutely predictable so usually taken out by the software, or more commonly used to give you an absolute heading relative to North.

      2. DCFusor Silver badge

        Re: Isn't this inertial guidance?

        Half right Charles.

        Integration itself is error prone, we don't have infinite precision in math processing itself - we have floats, doubles...and on up to a point, but it's not enough as errors accumulate - it's integration. Done over small enough sample intervals to whatever precision the buildup of error will kill you with any known processing power that is or likely will become available in the next few hundred years. See N body gravitational problem which has to be solved by perturbation (there is no closed form feedforward solution) and the inability to predict where, say, Jupiter will be in a hundred years to better than a bunch of miles accuracy. And that's with known inputs to any precision you'd like and things that take years to move around in a well known elipse - or close, as they pull on things that move and pull back and so on.

        Same class of problem here.

        In this case, the initial measurement by accelerometers, even if utterly exact (infinite bits/sample!), will still give errors due to gravitational anomalies making a thing that measures acceleration think its drifting up or down depending on what the gravity is where it happens to be, versus where it was calibrated. For example only - the field can be skewed in other directions as well. Looking at that is is one way to find things underground as a fairly well developed technology all its own.

        Slight changes in gravity even affect clocks at this precision level: https://physicsworld.com/a/a-brief-history-of-timekeeping/

        Yeah, for that, with a 100% accurate gravitational map (NASA is making them) you could correct. Thing is, at this level of accuracy, the tides and so on become significat sources of error. This is just more press-release "gimme another grant" technology with a hint of some science attached.

    3. LDS Silver badge

      Re: Isn't this inertial guidance?

      Inertial guidance systems have been in use for a long time before GPS became available. The disadvantages were they took time to be calibrated before leaving, and they would drift off after some time requiring corrections - which can be sometimes be automated. Anyway, gyroscopic compasses became widespread long ago because they are faster than magnetic ones, and don't have the peculiar behaviour magnetic compass exhibit in fast turns, when they can be "slower" or "faster", depending on heading and latitude, and require skills to obtain the right heading.

      Ships, planes, and many other vehicles used inertial systems and still use them, as it doesn't depend on an external signal to be available. How do you believe the Vulcan bombers reached the Falklands in the 1980s?

    4. Anonymous Coward
      Anonymous Coward

      Re: Isn't this inertial guidance?

      Bit pessimistic there - commercial INS are available with an error rate of about 1 kilometer an hour for something nice and smooth like a plane. Presumably expensive secret squirrel ones can do better Using the accelerometers in your phone, 45 seconds to Mars is probably about right.

      1. werdsmith Silver badge

        Re: Isn't this inertial guidance?

        The trick of turning on a magnetic compass was UNOS - undershoot north overshoot south and with experience you would learn how to roll out of a turn on heading.

        The directional gyro would point its heading right through the turn, but would drift off over time. Part of the regular checks was to re-align the gyro with the magnetic compass after a period of flying straight and level at a constant speed.

  7. Lee D Silver badge

    Anyone else reminded of The Big Bang Theory episodes?

    1. Rupert Fiennes Bronze badge

      Exactly

      Yup, this is exactly the BBT plotline :-)

  8. Morrie Wyatt
    Trollface

    Had to be said.

    "A phone's GPS accurate to roughly 15 feet, although military GPS devices can be accurate to centimeters. Then there is the fact that tall buildings will often throw a signal off and signals can be impaired by any large, dense object."

    So GPS doesn't work for politicians then.

    1. DJV Silver badge

      Re: Had to be said.

      Damn, you beat me to it! I came here to post something very similar (though it might have mentioned a certain Boris J by name).

      1. Morrie Wyatt

        Re: Had to be said.

        Why?

        What makes you think it's restricted to the UK?

        As I'm not British either, I felt it best to be carefully non-specific.

        Examples:

        https://www.theregister.co.uk/2011/01/28/malawi_legislation/

        https://www.theregister.co.uk/2018/09/19/oz_anticrypto_legislation/

        And just about anything to do with Donald Trump.

        It seems to be endemic to the breed anywhere around the world.

        (I'm an equal opportunity cynic.)

  9. Contrex

    America takes over

    The MOD is the "Ministry of Defense" now?

    1. Korev Silver badge
      Childcatcher

      Re: America takes over

      >The MOD is the "Ministry of Defense" now?

      You have a licence to kill, don't waste it...

      1. Anonymous Coward
        Anonymous Coward

        Re: America takes over

        "licence"

        Beg to differ. Everywhere I go it's license, incense, offense, defense, etc. It all makes "sense" to me (Or does it make "sence" to you?).

    2. jake Silver badge

      Re: America takes over

      No need to be so defensive.

      (This one falls under the "If you have to explain it" banner ...)

  10. Jeffrey Nonken Silver badge

    So it's an inertial tracker that will work on the Discworld, provided you don't need to know your elevation.

    1. John Brown (no body) Silver badge

      "So it's an inertial tracker that will work on the Discworld, provided you don't need to know your elevation."

      That explains why it's so big. You need somewhere for the ants to live in the CPU.

  11. arctic_haze Silver badge

    Inertial navigation system

    This is what it is:

    https://en.wikipedia.org/wiki/Inertial_navigation_system

    Maybe it is supposed to be better than the existing ones due to the quantum thing, but for mow it is two orders of magnitude larger than what is commercially available.

    1. jake Silver badge

      Re: Inertial navigation system

      When I mow the larger of the fields, I use bog-standard GPS, on the rare occasion that I don't use my Mk I eyeball, as gawd/ess intended.

    2. David Roberts Silver badge

      Re: Inertial navigation system

      Yes. An inertial navigation system to tell you precisely where you are. Part of that can also tell you which way you are pointing.

      A compass doesn't care where you are it just tells you where North is (for various values of North).

  12. John Smith 19 Gold badge
    Unhappy

    It'll still be a damm sight cheaper than the UK launching it's own Nav Sat constellation.

    Which is good.

    Yes it needs to shrink several orders of magnitude.

    Yes it needs to operate in 3 dimensions.

    But it'll still be a damm sight cheaper than the UK launching it's own GPS system, which is basically post Brexit willy waving.

    1. DCFusor Silver badge

      Re: It'll still be a damm sight cheaper than the UK launching it's own Nav Sat constellation.

      No it won't. One set of birds will serve however many users. This needs one per user.

      There is a big number of users....times the cost per each of these.

      The rest, well...I agree with the willy waving part.

      1. Anonymous Coward
        Anonymous Coward

        Re: It'll still be a damm sight cheaper than the UK launching it's own Nav Sat constellation.

        "I agree with the willy waving part"

        "Every Prime Minister needs a Willy" said the previous female PM at Westminster.

        1. werdsmith Silver badge

          Re: It'll still be a damm sight cheaper than the UK launching it's own Nav Sat constellation.

          No it won't. One set of birds will serve however many users. This needs one per user.

          You still need at least one receiver per user.

  13. Obesrver1

    it a start

    and it will work on other planets & maybe in space & higher gravity.

    Noted above: It is a part of a system not the full system that would need to maintain a starting point reference, & by adding extra planes for 3 dimensions X,Y,Z of movement & would provide rotational measurement functionality.

    A great beginning !

  14. Will Godfrey Silver badge
    Linux

    An Achillies heel?

    What are the power requirements? Also I'm assuming that even a brief interruption would be pretty dire.

    Hmmm, don't suppose it uses Linux for control.

    1. jaduncan

      Re: An Achillies heel?

      This kind of thing is literally what RTOSes are made for.

    2. SkippyBing Silver badge

      Re: An Achillies heel?

      'Also I'm assuming that even a brief interruption would be pretty dire.'

      As long as it stores where it was when the interruption happened it shouldn't be too bad depending on how fast you're going. You could just reinitialise it at you're last known position, you'd then have a circle of error based on how far you could have gone in the time you didn't know where you were.

  15. Rich 11 Silver badge

    Acceleration

    As the atoms move, their wave properties are affected by the acceleration of the vehicle. The optical ruler can measure these minute changes very accurately and then with a few relatively simple equations it is possible to figure out exactly where you are.

    Great stuff. I suppose that if you know where you already are then you can determine your angular acceleration with regard to the centre of the Earth and your overall acceleration with regard to that of the Earth around the Sun. Obviously I can see that one might be overwhelmed by the other, but it'd be nice to know for certain how this factors out in a fortnight's time.

  16. Anonymous Coward
    Anonymous Coward

    From the article:

    >A phone's GPS accurate to roughly 15 feet, although military GPS devices can be accurate to centimeters.

    Can we please drop these gross misunderstandings? Please? Or is this par for the course when the word boffins is being thrown around? It is not as if these mistakes have not been pointed out earlier.

  17. Anonymous Coward
    Anonymous Coward

    quantum quantum quantum quantum

    It can also find Deepak Chopra under a 100 metres of lead!

    1. jake Silver badge

      Re: quantum quantum quantum quantum

      I'd pay good money to watch that happen.

  18. Emdeha

    Nice cable ties there on your helmholtz coils... would be a shame if something happened to them...

    like slipping, vibrating or slacking due to thermal variations. Guess we won't get anything better than maybe +- 2% accuracy like this ? =( ;^P)

    About that 'compass' comparison: Velocity has magnitude and orientation, and is defined as length by time - therefore if (and only if) those accelerometers are reeeally precise, getting a compass-like direction out of a relative position change measurement is a mere subtraction and division away. Zero problemo.

    Trying that calculation with our everyday axe-celery-metres of a jesus-phone would leave one spinning erratically, hence the additional gryo-accelerometers in our phones.

    Since we can just buy a (quantum interference, so there !) laser gyro compass, the compass part of that thing is moot anyhow - And as long as said boffins don't get better linear accelerometry than, say, a contemporary gravimeter, said gps part goes down the drain, too.

    Just my arrogant (yeah, I studied physics, sorry) 2 cents 'bout that contraption.

  19. MiguelC Silver badge

    One plane gives you 2-dimensional positioning

    When they manage 3 planes will they get 4-dimensional positioning? Awesome!

  20. Malcolm Boura

    They will give it to the yanks for a bad trade deal and sell it to China.

  21. Simon B-52

    "Useful for things like autonomous cars"

    Do you actually believe that, for even a fraction of a second?

    This is boilerplate BS, tacked onto the end of most "defence" tech announcements to foster the illusion that it will have some use other than killing us all faster.

    Also, please consider the actual meaning of the word autonomous. An autonomous car is unlikely to ever be useful to people.

  22. This post has been deleted by its author

  23. Milton Silver badge

    Physics and engineering are not the author's speciality, are they?

    It isn't a compass. It's a new method for implementing the venerable concept of an inertial guidance system, which is itself simply a technological form of dead reckoning practised since the first manned boat got lost in poor visibility 11,174 years ago.

    Inertial navigation systems are still very important to submarines (such as boomers, spending long periods under water and unable to receive GPS) and I might guess that they would be the first operational priority for this new tech, given that its early-version mass and size won't be prohibitve in a sub, compared with a missile or an aircraft.

    It will be extremely interesting to see how the noise problem will be managed. With mechanical weaknesses such as friction removed (it is a core problem of current INS tech), the sensitivity of the new system is both advantage and disadvantage. There will need to be some clever design in dealing with local mascons, determining honest-vs-deceitful frames of reference, multi-axis rotation and relativistic effects—the latter cease to be ignorable when you're finely analysing the performance of kit which may accelerate at 100g, moving in three spatial dimensions, potentially rotating around one or all of those as well, and reaching speeds in the miles per second range¹.

    It'll be even more interesting to see what kinds of countermeasures might work against such a system. I'm guessing local EMP would banjax it thoroughly, as would an x-ray laser, not to mention finely tuned peppering by minute chunks of high-velocity debris (strikes by waves of microgram particles timed to arrive in a sequence to ensure destructive interference). That said, if you can shoot close enough to achieve that, you're probably close enough for a kinetic kill anyway ...

    ¹ Consider that even the 1960s Sprint ABM had incredible performance at this level, and furthermore that a rapidly spinning missile is one obvious countermeasure against laser strikes.)

  24. Anonymous Coward
    Anonymous Coward

    Love the Brexit snipe!

    But by the time this technology becomes, I'm not sure the UK will have a navy to use it on...

  25. eionmac

    Ah demonstation just in time. Norway / Finlands GPS knocked out by A.N. Other

    Just in time.Aircraft in Norway / Finland had GPS knocked out last week by an intruder, so military sexercise and all civilian aircraft had to navigate independent of GPS. probably absolutely necessary for nuclear subs, which have a very accurate known starting point

    1. Anonymous Coward
      Anonymous Coward

      Re: Ah demonstation just in time. Norway / Finlands GPS knocked out by A.N. Other

      > had to navigate independent of GPS

      Most Norwegian should know how to navigate by the sun or by the stars, use map and compass, sailing a ship by light houses at night (the crew at Helge Ingstad was probably drunk) or use any of the numerous ways of navigating between sails first were hoisted and the introduction of GPS.

      Finland and Norway has national service where you would learn these things if you didn't know how beforehand.

      1. Anonymous Coward
        Anonymous Coward

        Re: Ah demonstation just in time. Norway / Finlands GPS knocked out by A.N. Other

        But isn't the North Sea notoriously stormy, meaning celestial AND terrestrial visibility was bad, your ship would regularly be tossed around off course, AND there's the risk of a lightning bolt throwing off your compass?

        1. SkippyBing Silver badge

          Re: Ah demonstation just in time. Norway / Finlands GPS knocked out by A.N. Other

          'But isn't the North Sea notoriously stormy, meaning celestial AND terrestrial visibility was bad, your ship would regularly be tossed around off course, AND there's the risk of a lightning bolt throwing off your compass?'

          Presumably why no one went anywhere by boat until the invention of GPS...

          1. Anonymous Coward
            Anonymous Coward

            Re: Ah demonstation just in time. Norway / Finlands GPS knocked out by A.N. Other

            "Presumably why no one went anywhere by boat until the invention of GPS..."

            OR...presumably why there were lots of errors and shipwrecks until one had a better idea of one's location in such tempestuous waters...

            1. SkippyBing Silver badge

              Re: Ah demonstation just in time. Norway / Finlands GPS knocked out by A.N. Other

              'OR...presumably why there were lots of errors and shipwrecks until one had a better idea of one's location in such tempestuous waters...'

              Yeah, that was pretty much cracked pre-GPS though, if you're out of sight of land you don't need GPS level accuracy and if you're in sight of land visual fixing is more than good enough.

              1. jake Silver badge

                Re: Ah demonstation just in time. Norway / Finlands GPS knocked out by A.N. Other

                For example, humans had no difficulties moving from one speck of an island to another in the Pacific long before even magnetic compasses made it to that part of the world. See Polynesian navigation in your encyclopedia of choice.

    2. onefang Silver badge
      Paris Hilton

      Re: Ah demonstation just in time. Norway / Finlands GPS knocked out by A.N. Other

      "Just in time.Aircraft in Norway / Finland had GPS knocked out last week by an intruder, so military sexercise"

      That sounds like a very fun military they have in Norway / Finland.

  26. Andrew Dancy

    eLORAN?

    I recall reading a few months ago there had been a UK Gov report into the vulnerabilities of GPS (it's not just navigation - GPS timing signals are used for all sorts of scary things like synchronising electrical grid frequencies and regulating frequency slicing on the mobile phone networks). The conclusion was that jamming or solar events leading to a loss of GPS would have potentially catastrophic effects on modern life.

    They suggested a number of solutions, one of which was eLORAN . Basically an update of the old LORAN navigation network used until the mid 90s it would provide both location and timing (whilst many other GPS alternatives only do one or the other) whilst being virtually impossible to jam due to the much lower frequencies used. Unfortunately a trial a few years ago was kyboshed when other European countries turned off their transmitters (rumour has it there was pressure from the Commission not to support tech which could rival Galileo), so there's currently only one transmitter running (enough to support timing but not location, which needs multiple transmitters).

    Setting up a chain of eLORAN transmitters would have the same utility as a British GPS system and would be considerably cheaper!

    1. Anonymous Coward
      Anonymous Coward

      Re: eLORAN?

      Wow! I got all the way to the bottom of page three of the comments before an eLORAN proponent hove over the horizon.

  27. Anonymous Coward
    Anonymous Coward

    Will it be ready by March 2019

    When we lose access to GPS?

  28. Stevie Silver badge

    Bah!

    Bad news is the subspace quantum nuclear magnetic flux buggers up mechanical *and* digital watches, so while you might know exactly where you are, you won't ever be able to calculate your average speed over the orienteering course.

    I had a pedometer once. I switched it on and walked twelve miles. I checked the output on the device while celebrating in the pub and it correctly showed I had two feet.

    1. Charles 9 Silver badge

      Re: Bah!

      How would the pedometer know you had two feet? You could have three legs for all it knows.

  29. Anonymous Coward
    Anonymous Coward

    Cool lasers in there..

    (That's my coat over there, the one by the angry mob. Can you fetch it for me?)

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