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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

#61

Post by myself248 »

arijun wrote: post #18
myself248 wrote: post #15

Earlier quoted context omitted.

> Both BeiDou and GPS are supposed to be limited to 10m precision for civilians. Maybe in 1998, but Selective Availability was turned off in 2000, and here in the modern era: https://rtklibexplorer.wordpress.com/2024/04/28/dual-frequen...

Oh interesting, I think I conflated two things; Selective Availability and the military-only bands on GPS. While it's true that access to the military band could improve accuracy with dual-band receivers, consumer devices can use dual-band as well (as your link shows), since there are multiple unencrypted bands from navigation satellites nowadays. I am not sure how to interpret your link, though. It doesn't measure a…

There are a couple of points:

The L1 signal had selective availability in the 90s, and it no longer does. SA had the real-world accuracy around 30m in practice; the "up to" 100m rarely happened. Without SA, plain L1 with good skyview (low DOP) gets you around 10m, or down under 5m if WAAS is having a good day.

Availability of multiple civilian bands, and cost-effective dual-band receivers, allows an ionosphere-free (no need for WAAS) solution in the 1-2m range, with a single receiver.

Ubiquity of internet connections makes it trivial to apply RTK correction data without having to set up your own base station, and/or, availability of affordable medium-range data radios makes it easy to set up your own base station. In either case, it's easier to run RTK than ever before, and dual-band RTK gets you down into the low centimeters, limited mostly by how accurately your base station was surveyed-in.

And none of that touches the military signals.

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

#62

Post by [deleted] »

ryandrake wrote: post #57
avazhi wrote: post #54

Earlier quoted context omitted.

> so presumably a number of them are attached to people who did no crimes. You and I have very divergent views of the type of person likely to be charged or prosecuted for a crime or indeed to participate in a diversion program that involves GPS trackers, my friend.

Right, because only guilty people become involved with the justice system.

[deleted]

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

#63

Post by dataflow »

chaps wrote: post #58
dataflow wrote: post #47

Earlier quoted context omitted.

Do you have any examples of someone getting thrown behind bars due to a GPS error on the order of ~30ft like you're claiming? That's all I'm asking. Really don't understand why you keep avoiding it. You've essentially claimed police/judges are doing something rather stupid and terrible. I'm asking you to show example(s) of what you claimed (~30ft error → thrown behind bars), not something significantly different (~1+…

"You've essentially claimed police/judges are doing something rather stupid and terrible." Yes, yes I am. You really need to realize just how unbelievably fucking arbitrary the criminal courts are. At every level. They're not tech people. To answer your question, I have examples of motions by prosecutors to suspend people from the EM program where they specifically cite specific data points just barely out of their h…

> To answer your question

Looking forward!

> motions by prosecutors

Motion ≠ incarceration. So, not an answer (yet?)...

Did defendants get incarcerated as a result of these motions, or no?

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

#64

Post by crtified »

avazhi wrote: post #54
boomboomsubban wrote: post #46

Earlier quoted context omitted.

The trackers are part of CCSO’s pretrial house arrest program, so presumably a number of them are attached to people who did no crimes.

> so presumably a number of them are attached to people who did no crimes. You and I have very divergent views of the type of person likely to be charged or prosecuted for a crime or indeed to participate in a diversion program that involves GPS trackers, my friend.

Not at all. They're remarkably similar. What differs is our cost:benefit analysis of closing off this errata.

Yours (inferred) is "Too Much : Zero".

Given that those are terminal values it would challenging for literally-any-other-view not to diverge from yours, on this.

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

#65

Post by [deleted] »

crtified wrote: post #64
avazhi wrote: post #54

Earlier quoted context omitted.

> so presumably a number of them are attached to people who did no crimes. You and I have very divergent views of the type of person likely to be charged or prosecuted for a crime or indeed to participate in a diversion program that involves GPS trackers, my friend.

Not at all. They're remarkably similar. What differs is our cost:benefit analysis of closing off this errata. Yours (inferred) is "Too Much : Zero". Given that those are terminal values it would challenging for literally-any-other-view not to diverge from yours, on this.

[deleted]

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

#66

Post by Aurornis »

chaps wrote: post #41
dataflow wrote: post #38

Earlier quoted context omitted.

You're claiming that erroneously reported movements by ~33 ft lead to incarceration, yet the article you're linking to reports that erroneously reported movements by ~1mi+ lead to police coming to double-check what's going on. Am I incorrect and do you therefore have examples of ~30ft errors actually leading to their incarceration , or are you struggling to see the disconnect between what you're claiming vs. what is…

If someone's home is 30' by 30' feet, yes, that person's device will report them having left their home and they'll get a visit if GPS suddenly shifts 30 feet to the left. I'm talking about the class of problem. It happens in normal weather conditions and things like this exacerbate the problem. Really not sure what the hostility's about.

GPS is not that accurate even on a good day. A small device attached to someone’s ankle with a small antenna and an obstructed view of the sky will frequently be registering locations outside of the footprint of someone’s house.

A single 33 foot anomaly is already within the geofence buffer zones used. In dense urban areas the geofence buffer allowance may be 10X that already.

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

#67

Post by CGMthrowaway »

sen wrote: post #31
MarkusQ wrote: post #30

TFA article claims: "Indeed, the solar storm of May 2024 is estimated to have cost the US agricultural industry $500 million due to disruptions in precision navigation." This seems hard to believe. The link provided hand waves through how it maybe could happen, and ends with an Economist just SWAGing that it could have been maybe a dollar an acre or so. "He estimates that affected farms lost about $1 per acre. Nation…

That’s how all “estimated damages” work. It’s all just made up by some random person who guesstimated a number then multiplied it by the maximum possible people effected, realistic or not.

Tell me "it's different" with this one please https://sustainability.stanford.edu/news/study-links-past-em...

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

#68

Post by Aurornis »

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-...

Geofence monitors have buffer zones because a small GPS on someone’s ankle inside a house, potentially a high rise, isn’t going to be that precise.

33 feet is well within the allowances IIRC. Varies by state.

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

#69

Post by chaps »

dataflow wrote: post #63
chaps wrote: post #58

Earlier quoted context omitted.

"You've essentially claimed police/judges are doing something rather stupid and terrible." Yes, yes I am. You really need to realize just how unbelievably fucking arbitrary the criminal courts are. At every level. They're not tech people. To answer your question, I have examples of motions by prosecutors to suspend people from the EM program where they specifically cite specific data points just barely out of their h…

> To answer your question Looking forward! > motions by prosecutors Motion ≠ incarceration. So, not an answer (yet?)... Did defendants get incarcerated as a result of these motions, or no?

They did, yes. I hope you have a better day.

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

#70

Post by chaps »

Aurornis wrote: post #68
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-...

Geofence monitors have buffer zones because a small GPS on someone’s ankle inside a house, potentially a high rise, isn’t going to be that precise. 33 feet is well within the allowances IIRC. Varies by state.

That might be true for a place in the middle of nowhere with no features, the same device model managed by the same company and the same call center person and same sheriff and judges and prosecutor. But with GPS in an urban environment where many homes are over 100 years built from many different materials, 33 feet is a lot.
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