Lights out for Space Vehicle Number 23: UK smacked when US sat threw GPS out of whack An error in the Global Positioning System (GPS) network apparently triggered by the decommissioning of a US satellite last week has had knock-on effect across a number of UK industries, it has emerged. Many industries are reliant on on GPS software for a swathe of critical applications such as financial trading and precision …
I am not clear what the article is actually talking about. Was the healthy bit set but ignored by ground segment users? Or did the problems occur between the onset of the failure and its recognition by the control segment?
The implications are vastly different.
Because it's a radio signal that is traversing the earth, so the recievers further away would be behind those closer to Anthorn.
For most things people do that wouldn't matter - but this was a 13 microsecond glitch causing issues...
That's 4 km
The UK is larger than that (citation needed)
Most of the critical stuff is probably static, so extra delays could be calculated - but this is a very high accuracy failure...
Could an equivalent be achieved by requiring all radio stations to broadcast their position and the current (accurate) time?
Seems a lot more simple than chucking satellites into space, although it wouldn't have the same coverage area, obviously.
I assume I'm missing something obvious though, just a thought.
"requiring all radio stations to broadcast their position and the current (accurate) time?"
only analog stations, not digital
and you'd have to get round the problem of multiple transmitters per station -e.g. BBC Radio Lancashire has four FM channels on different transmission sites
Hmm... indeed. One of those low-risk:high-impact failure modes that crop up in these discussions is a solar coronal mass ejection that takes out a significant number of orbiting electronic devices. Unless we believe that Galileo, GLONASS, etc. satellites are better hardened against radiation damage than GPS, they don't constitute an effective backup (for that scenario).
As far as I remember (haven't looked it up) we're currently on the downslope of the 11-year solar activity cycle: I'm sure we'll have reduced our dependency on orbital electronics by the time of the next maximum. [Insert unwarranted optimism icon of your choice].
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A 13 microsecond slew stops the prevision docking of oil tankers??? I would hope they used something more accurate than /just/ GPS for docking procedures, e.g. ship borne proximity sensors ... or even harbour 'pilots' and lots of eyes!
All systems can fail .. if you rely solely on /one/ system for anything important then you will get burned at some point.
"if you rely solely on /one/ system for anything important then you will get burned at some point."
.... And with an oil tanker, that burn has the potential to be serious.
Torn between Get My coat Icon and the one I eventually went for.
Tankers are pretty big. That is a lot of mass therefore when docking, the amount of thrust in one direction is critical that even a tiny amount of apparent movement can be too much. So yep, 13 ms when you are using that to determine position (radio travels a long way in 13 ms) means that you can't accurately determine the amount of thrust to bring the behemoth to a halt at the right point.
This is all supposition, btw. http://sploid.gizmodo.com/incredible-overhead-view-of-an-oil-tanker-perfectly-doc-1725572780
So yeah. Backup systems are key. I have no idea how accurate the other systems are compared to GPS. I am surprised, though, that some kind of, oh I dunno, laser ranging isn't employed against specified dedicated targets on a dock.
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What's 'precision docking of oil tankers' if it isn't navigation?!
Okay technically it's pilotage but it's pretty much the same thing.
As an aside I've seen it used to synchronise frequency hopping radios and the operator was completly unaware the numbers on the display had anything to do with the geographic position. Still it was handy to know his phone number for when there was an exercise fire on the bridge and we had to navigate from the upper deck.
Mort offered "radio travels a long way in 13 ms"
Even in the corrected 13µs (as opposed to 13ms), it's on the order of 13,000 feet. About a foot per ns.
It'd be a pretty poor navigation system that depends on absolute time, as opposed to relative. Typically, it's all relative timing.
it's on the order of 13,000 feet. About a foot per ns. It'd be a pretty poor navigation system that depends on absolute time, as opposed to relative.
It'd be a pretty poor navigation system that depends on 1/6th of a dead king's armspan as a unit.
But the metre is based on being one ten-millionth of the distance from the equator to the north pole of an utterly insignificant little blue green planet orbitting a small unregarded yellow sun, far out in the uncharted backwaters of the unfashionable end of the western spiral arm of the Galaxy. Not much better, really.
> A 13 microsecond slew stops the prevision docking of oil tankers ?
That is actually huge -- the speed of light is quite fast, so it correspond to about 4km so regardless of if you use the signal to calculate velocity (just a error of a few miles/h would make the docking impossible), or as a relative comparison to a second source it makes a big difference
In docking, the ship just needs to get close enough to the dock that it can be completed by tugs pushing it in place or longshoremen with ropes and winches pulling it into place. Beside, any tugger should be familiar enough with their port and their ship to be able to guide ships into place without anything more than basic instruments.
I suppose this is a symptom of skills going rusty because the computer does all the work for them, much like modern aircraft were if something goes wrong, better hope the pilot can read the manual in time...
"Exactly. There were big ships like oil tankers and aircraft carriers and whatnot decades before there was GPS. Makes you wonder how they managed? "
and thats why we had the Torrey Canyon, Amoco Cadiz, Exxon Valdez.................maybe they didn't manage
"how many super tankers ran aground whilst docking?". Yes indeed, referring to docking is a bit silly, the real danger is at problematic parts of the sea where no referent points are visible (and rocks are not visible) . Take, for instance, the Baltic where lots of tankers move to and from Russia.
Short non dramatic answer - yes oil tankers have different systems - usually a laser based one.
Sorry, I mean "OMG, all the tankers are going to explode!"
The issue more is that the reliance on a space borne radio signal seems woven in to many aspects of daily life and critical infrastructure as a convenience more than anything else. I remember being told in a previous life that the reason I needed to learn to use a map and compass was because, comparatively, GPS is like looking up into space for the light from a torch strapped to a satellite whilst its directly in front of the Sun. An oversimplification, but accurate enough.
Radios break, radios fail, radio can be jammed. The issue seems to be more an over-reliance on super accurate synchronized timing sources. The more accurate you need something to be, the more likely you'll get an undesirable result after all.
I hope that the designers of high reliability, mission critical GPS receivers use more than the mathematical minimum number of sats (four, I believe) to establish position.
My little handheld unit can usually get eight or nine good GPS sats, plus half a dozen GLONASS on the average day.
He said: "A more effective backup for GPS is desperately needed."
Anyone else thinking that misses the issue - a more effective replacement for GPS is desperately needed.
Companies place their dependence on systems that can have their accuracy manipulated by a foreign entity. Yes I know that the commercial GPS services are supposed to come with higher accuracy & reliability service levels - but that didn't help in this instance.
Serious question as I've not had to do this for a long time - what ever happened to taking the atomic clock signals as the prime source?
My navigation gear was always synched to WWV and we'd pay attention to the clock slew across the different systems. My being very proactive with the systems seemed to be appreciated by the navigator and quartermasters and I'd hear about even minor glitches long before they'd graduate to career enders. And it kept the Captain happy which is always a consideration.
Their sales should take off...
Amusingly, the CSAC has a pin to input the GPS 1pps signal (a pulse precisely aligned with the exact 'top' of each GPS second) to discipline the atomic clock. So any system design would likely still have a connection back to the GPS Time.
Life just got a lot more complicated for system designers.
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MEMS devices used commonly in smartphones used to be in that price range too, when they were produced in quantities of tens of thousands a year.
The advantage to including an atomic clock in a phone would be a massive improvement in position acquisition time as well as some improvement in accuracy (especially altitude) but you have a chicken and egg situation. The only chance for the price of a CSAC to drop like six axis MEMS did to allow their inclusion in cell phones would be if someone commits to ordering massive quantities. So probably Apple would have to think it is worth including to drive the price down enough for widespread adoption, as they did with flash and MEMS.
Apple bought an outdated fab in San Jose from Maxim last year, there was some speculation as to exactly why since it uses a very outdated process and would only be suitable for things like MEMS devices. I suppose there's a chance it could be used to produce a couple hundred million CSACs a year - to give Apple the benefit of this improvement in the iPhone without driving up volumes in the industry to where it is cheap and easy for everyone else to quickly match them.
This year they increased processing power by 70% (benchmarks run by anandtech and others proved their claims were quite justified) so that's not a "slightly increased" amount, but the 6 was already 'fast enough' so there are diminishing returns in utility of faster SoCs even if they were able to do that every year, which they obviously can't.
They'd prefer to add something unique that Samsung and other competitors can't easily duplicate, I'm just not sure "faster and more accurate GPS positioning" is going to move the needle. Perhaps combined with improved MEMS that allowed dead reckoning to a high degree of accuracy for when are out of range of GPS they could have a winner - and that fab they bought would allow them to gain economies of scale for their needs while similar capabilities would be too expensive for the competition unless they were willing to commit to ordering fifty million a year (and even then require a few years to catch up)
So I wouldn't be surprised to see something that's unique and not very easy for the Android world to duplicate in the 7S. Whether it is something that people care enough about having to influence their choice of what phone to buy (whether it means getting people to switch to iPhone, or stop them switching from iPhone) well that remains to be seen I guess.
I used to manage private Stratum 1 NTP servers. They did indeed use GPS as Stratum 0.
Proper NTP (as opposed to, say, Simple NTP) corrects for clock differences by accelerating or decelerating the local clock to gradually bring it back into harmony with the reference time.
I'm not sure that even El Reg's blind suicidal harbor pilot would notice a few ms drift over 12 hours.
I have an interesting story about NTP. Suppose you have redundant pairs of NTP servers, and hosts are configured to use both, in case one is offline. Now suppose that one of your NTP servers doesn't go offline, but just throws a wobbly and gets "stuck" at the wrong time. Many NTP clients (at least, those running the standard ISC code) will exit if the difference between local clock and the reference clock is too implausibly great. In this hypothetical case, there would be just a minor hiccup on your (redundant) NTP infrastructure with no downstream effects...until that threshold is reached, at which point thousands of systems would start to unrecoverably fail their NTP clients as they randomly hit the wobbly NTP server. Sometimes redundancy introduces new and exciting failure modes!
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