Is It Really GPS If It Doesn't Use Satellites? 298
cartechboy writes: "GPS was originally developed by the military, but today it's in your smartphones, and soon, possibly your watches. Now the British military is developing something called quantum compass. The concept is a GPS-style navigation for submarines that doesn't use satellites. The quantum compass uses the movements of super-cooled subatomic particles to pinpoint a vessel's location. These particles, stored in a vacuum, react to the Earth's magnetic field. The movements caused by this interaction can be used for location positioning. At the moment, the Ministry of Defense's prototype resembles a '1-meter long shoe box,' so the next step is to miniaturize it. It could then be used by individual soldiers, as well as huge ships and submarines. Not only is it useful, but it's secure too—the technology is apparently interference-proof. Is this the future of navigation systems, or the reinvention of the compass? Possibly both."
Not GPS (Score:5, Informative)
Nope. [wikipedia.org]
Sounds like more like an inertial navigation system, [wikipedia.org] but one that uses the Earth's magnetic field instead of just being shaken around.
depends. (Score:5, Informative)
Are we saying Global Positioning System, capitalized and considered a Proper Noun?
Then, no.
Are we saying global positionin system, a generalized term for systems that give you position data on the globe?
Then yes.
LORAN, EPLRS (when used as it was actually created for instead of a mesh data network), VORTAC, and probably many other systems were all generic positioning systems.
If the earths magnetic field moves (and it does), then won't this system also be affected?
Re:Does it give you a position on the globe? (Score:5, Informative)
I'm skeptical (Score:4, Informative)
These particles, stored in a vacuum, react to the Earth's magnetic field.
I work for a company that deals with inertial navigation systems, specifically systems based on mechanical gyroscopes. The reason we use gyroscopes is because testing, running, and updating our tools for the last 30 years has shown us that we are inherently more precise than a magnetic measurement tool that measures the Earth's (local) magnetic field. Contrary to our tools, a magnetic measurement device is easily influenced by outside interference. Events like variations in the solar wind, such as solar flares, can easily interfere with the local magnetic field, which in turn changes your measurement of the field. Of course you can compensate for this with a lot of math, but even then those tools are still not as accurate as the tools we provide. I'd really like to know how they solved that problem, if they actually did.
Re:Durability? (Score:5, Informative)
About 3 inches. The GPS satellites transmit signals on two carrier frequencies. The L1 carrier is 1575.42 MHz and carries both the status message and a pseudo-random code for timing. The L2 carrier is 1227.60 MHz and is used for the more precise military data stream
Salt water attenuates 1.5ghz signals quite effectively.
Re:stable magnetic field (Score:2, Informative)
If you measure the magnetic field at a point on the Earth's surface, do not expect to get the value predicted by the IGRF! Quite apart from the errors discussed above, there might be fixed contributions from buildings, parked cars, etc., and the magnetization of crustal rocks will certainly add its own local, small-scale, field, typically of magnitude 200 nT, but often much larger. There are also a large variety of time-varying fields, both man-made (traffic, DC electric trains and trams, etc.) and natural (from electric currents in the ionosphere and magnetosphere), and the associated induced fields from currents induced in the conducting earth. The ionospheric and magnetospheric fields occur at time scales mostly ranging from seconds to hours; in "quiet" conditions they may be as small as 20 nT (though enhanced near the geomagnetic equator and over the polar caps), but up to 1000 nT and more during a magnetic storm. On a longer time scale (days to years), the large-scale magnetic field of the external ring current (approximately represented by the Dst index) will give perhaps 1000 nT during and after a magnetic storm.
Re:Well ... (Score:4, Informative)
GPS specifically refers to the system created by the US military for tracking your position using a bunch of satellites they put up there.
So, its a System that gives you your Position on the Globe, but not a GPS(TM). Thanks for the clarification...
Unless its just a super-accurate way of finding out which way is North in which case it is probably a compass (not trademarked, at least in that context, AFAIK). Carefully analysing the name "quantum compass" suggests that maybe, just maybe, that's the case - although it could still form part of a System that gives your Position on the Globe.
Maybe the key distinction is that a GPS (TM-or-otherwise) will work out your position from scratch, whereas the sort of hyper-accurate dead reckoning/inertial navigation system that TFA appears to describe would need to know where you started from...
Article is lame blogspam. Here's the real info. (Score:5, Informative)
Lame article, which points to a blog, which points to another blog, which points to the wrong place on a Russian site, which copied the article from The Daily Mail. [dailymail.co.uk] The Daily Mail, even though a tabloid, has a halfway decent article.
I'm not going to explain inertial guidance; that's what Wikipedia is for. This is better inertial guidance. Here's a popular article which describes this new class of "gyros" and accelerometers. [army.mil] If you really want to know what's going on here, read Advances in Atomic Gyroscopes: A View from Inertial Navigation Applications [mdpi.com]
Laser "gyros", which work by interferometery and have no moving parts, have been around for decades. The best laser gyros still have more drift, by about 2 orders of magnitude, than the best mechanical gyros. Laser gyro technology has hit the limits of what you can do with photons. The idea here is to do interferometry with coupled atoms, rather than photons. That technology has been slowly improving for a decade or so, and it looks like it's getting close to deployment for high-end applcations.
One of the more interesting possibilities here is chip-scale gyros of moderate precision. Here's a Honewell patent from 2006 [google.com] for one.
Re:Well ... (Score:4, Informative)
A sextant can find longitude through the lunar distance method, comparing the moon's position to that of a reference star and looking up that position in a Nautical Almanac to find Greenwich Time. This method was actually discovered a few years after the marine chronometer was invented, but was the dominant method during the 18th century because of the insane cost of chronometers at the time.
A sextant is also needed to find the local time at your current location regardless of whether you use a chronometer or the moon to find GMT, so it's at the least half of the process in finding longitude either way.
Re:stable magnetic field (Score:5, Informative)
Re:Not GPS (Score:2, Informative)
Currently subs need very accurate gravity maps to deal with local differences in the gravity field. With this they will need even more accurate ones. An INS and a gravity meter are in some ways the same instrument. The better they are, the more similar they are.
Re:Man-portable supercooling? (Score:2, Informative)
Just the ultra high vacuum vessel and the turbo pumps, allowing you to reach vacuum better than in orbit at 200 km altitude, are enough... and you haven't started to cool yet.
You don't need a large pump for a small volume, especially if the vessel will not be opened regularly during normal operation. Ten years ago I was a on a project using a small vacuum vessel, and we had a self contained commercial vacuum system in a box the size of a shoe box that included a turbo and a two stage oil-free roughing pump. We regularly got down to 10^-7 with that setup, and if purpose built it could have been smaller for our use. With a high quality turbo, you can get down to the 10^-9 needed for laser trapping of atoms, but a small cryopump setup would work well to augment a cheaper/smaller turbo. Self contained cryopump setups were already shoe box sized years ago, and again used on something with larger volume than what they would need here for a purpose-built system. Small, ultra high vacuum systems are straightforward to build and have commercial sources, although you don't see them in a lab as often because the smallest have very tiny pumping rates that are not useful for labs that need to open their vacuum vessel from time to time.
The equipment volume and weight isn't so much an issue for making something man portable, as is having the power to run them for any length of time. Batteries to supply a couple hundred watts continuously get kind of heavy for any decent amount of time.