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GPS glitched across the US by as much as 33 feet

sciencealert.com

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Re: GPS glitched across the US by as much as 33 feet

#141

Post by rotringlvr »

weberer wrote: post #132
rotringlvr wrote: post #73

Earlier quoted context omitted.

Feet are actually great units for RF because a nanosecond is very close to a foot. Since feet has many prime factors and/or the foot-meter conversion is also easy, you can quickly get a wavelength of, say a 2GHz (6 inches), and get it in cm (15cm). Of course, ideally we'd ditch the silly metric system and use natural units. Then these 30 feet are a more comfortable 50M/eV. But those SI guys are really conservative an…

I would love a new measurement system based on planck units.

[dead]

Re: GPS glitched across the US by as much as 33 feet

#142

Post by MarkusQ »

qlte wrote: post #94
Waterluvian wrote: post #34

Earlier quoted context omitted.

There’s probably a reasonable methodology but it has a lot of multiplications and some base parameters that make the whole thing wildly sensitive.

Yes, it's actually based on an economic model seemingly developed with a detailed understanding of modern farming practices and historical effects of timeline disruptions on yields. It may be approximate but isn't just some random dude guesstimating based on vibes or something. https://farmdocdaily.illinois.edu/2024/05/how-will-the-gps-o... https://shiny.agmanager.info/cottonBotsDev/

It's an order of magnitude estimate of the worst case per acre, multiplied by a very course estimate of the number of acres affected, with little or no accounting for the length of the outage, the timing of the outage relative to specific crop-planting times in specific regions, and similar factors. It relies on manufacturer's estimates of the benefit of using their technology to assess the impact of not being able to use the technology. In other words, it's a SWAG.

Consider: the outage may have meant that some equipment would be slower, less accurate, or missing some features, causing time delays and other losses that may or may not be equivalent to using the non-GPS equipment. Or it could have rendered the equipment entirely unusable during the outage. It could even have permanently damaged the equipment (e.g. causing it to drive over an embankment or something). There is no apparent attempt to differentiate these outcomes, which could have significant impact on the estimate.

Re: GPS glitched across the US by as much as 33 feet

#143

Post by fhn »

chaps wrote: post #12

This is exactly the sort of thing that leads to people getting reincarcerated after their electronic monitoring devices mistakenly report them leaving their homes. Some reporting I did on the topic a few years back: https://chicagoreader.com/news/many-on-house-arrest-in-cook-...

There's always someone who roots for the criminals

Re: GPS glitched across the US by as much as 33 feet

#144

Post by Yhippa »

Is this considered "outside-in" GPS? That is, relying on satellites orbiting the Earth? Is there such thing as "inside-out" where maybe you rely on the images of the sky above? I guess without IR or other secondary scanning technologies, that would be difficult.

Re: GPS glitched across the US by as much as 33 feet

#145

Post by mrguyorama »

Yhippa wrote: post #144

Is this considered "outside-in" GPS? That is, relying on satellites orbiting the Earth? Is there such thing as "inside-out" where maybe you rely on the images of the sky above? I guess without IR or other secondary scanning technologies, that would be difficult.

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

It's old tech

There's also the classic of dead reckoning, which is usually infeasible but modern commercial aircraft have the capability of bounded accuracy in their dead reckoning navigation for several hours at a time if needed, and if you are the US government, you can build fantastical machines to measure your own motion and dead reckon yourself to a very very tight point on the other side of the world.

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

That thing still has orders of magnitude better stability than common laser ring gyros as used on those airplanes, and the same for the price tag.

GPS was dominant because it's cheapish and high performance and easy for a lot of contexts. However, it is critically easy to jam, for physics reasons. A jamming transmitter will always be thousands of miles closer to you than the GPS satellites are. Jamming GPS is cheap and easy, so all war will involve the denial of precision GPS guidance, so we are looking into alternative guidance again.

TERCOM as used in the Tomahawk missile existed to guide them semi-inertially back in the 80s and was functional.

In Ukraine, various providers have developed (supposedly) ways of using commodity cameras to watch the scenery pass by under a flying drone to ground medium quality inertial systems, to allow dirt cheap, unjammable navigation over long distances. It will be interesting how this plays out.

Re: GPS glitched across the US by as much as 33 feet

#146

Post by dataflow »

chaps wrote: post #139
dataflow wrote: post #135

Earlier quoted context omitted.

Thanks for the feedback, but I think you're missing something. This is not about us, it's about everything and everyone else implicated in the discussion. About the fact that we're essentially being demanded to assume - without clear evidence - that the vast majority of those with power over us are categorically incredibly incompetent or malicious. That is not only incredibly insulting toward the good subset of human…

Next time try to make yourself easier to talk to and maybe you'll get better answers. When responding to you it felt like all you were trying to do was "own the left" instead of approach it with actual curiosity and interest. The sort of thing where nothing I say will ever, ever, ever satisfy you. Have a good one.

Neither I nor you should appreciate spreading unsubstantiated rumors that directly attack the public servants neither of us personally know. If it bothers you that I'm defending them, then perhaps don't launch your attacks on them until you can share solid evidence that directly supports your claims. They're not going to be the ones defending themselves here and neither are you, and surely you don't expect us to accept whatever we read as true with zero evidence. Otherwise you're just spreading rumors. You owe it to the people you're talking to to justify any distrust that you're sowing.

And no, I'm not here to "own" anyone, whether left or right or up or down. I'm here to figure out what is true and what is false, and what is a rumor. Hence my question. If you had actually provided solid evidence for your claims in the beginning, I would have spread your words in support of your cause. I don't want innocent people being harmed any more than you do, whether they're wearing ankle monitors or robes.

Re: GPS glitched across the US by as much as 33 feet

#147

Post by woodrowbarlow »

mrguyorama wrote: post #145
Yhippa wrote: post #144

Is this considered "outside-in" GPS? That is, relying on satellites orbiting the Earth? Is there such thing as "inside-out" where maybe you rely on the images of the sky above? I guess without IR or other secondary scanning technologies, that would be difficult.

https://en.wikipedia.org/wiki/Star_tracker It's old tech There's also the classic of dead reckoning, which is usually infeasible but modern commercial aircraft have the capability of bounded accuracy in their dead reckoning navigation for several hours at a time if needed, and if you are the US government, you can build fantastical machines to measure your own motion and dead reckon yourself to a very very tight poin…

fun fact: the first mass-produced consumer in-car live navigation (1981) was all dead reckoning and gyroscopes. at this point, the GPS network was operational but not available for consumer use until 1988.

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

Re: GPS glitched across the US by as much as 33 feet

#148

Post by 12_throw_away »

John7878781 wrote: post #36
nwbear90 wrote: post #35

An interesting warning as Austin is blanketed by Cybercabs. I think a town full of golden driverless cars 33 feet from where they think they should be is terrifying.

I would be shocked if Cybercabs solely rely on GPS for positioning. I imagine they look at their surrondings, etc.

I would be shocked if Tesla had properly considered and mitigated all of the single points of failure, given their track record. [1]

[1] https://www.bloomberg.com/features/2025-tesla-dangerous-door...

Re: GPS glitched across the US by as much as 33 feet

#149

Post by tyffanypastecf »

rotringlvr wrote: post #73
delta_p_delta_x wrote: post #8

*10 metres

Feet are actually great units for RF because a nanosecond is very close to a foot. Since feet has many prime factors and/or the foot-meter conversion is also easy, you can quickly get a wavelength of, say a 2GHz (6 inches), and get it in cm (15cm). Of course, ideally we'd ditch the silly metric system and use natural units. Then these 30 feet are a more comfortable 50M/eV. But those SI guys are really conservative an…

[dead]

Re: GPS glitched across the US by as much as 33 feet

#150

Post by lazyasciiart »

GJim wrote: post #124
lazyasciiart wrote: post #120

Earlier quoted context omitted.

Everyone knows video footage can be faked. Why would the judge ever trust video provided by the defendant over serious professional technology like GPS? Might as well just take their word for it! What’s funny here is that you are displaying misplaced trust in the justice system that exactly parallels my hypothetical judge’s misplaced trust in technology.

> Everyone knows video footage can be faked. Everyone also knows GPS can be spoofed. Your point?

No, most people don't know GPS can be spoofed, or at best think of it as a nation-state level action. I'd be surprised if you got less than 100% of non-tech people saying that if GPS contradicts a video then the video is faked.
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