not just space weather, I am pretty sure the atmosphere is being disturbed by toxic human activity both by accident and on purpose
I've run outside every morning for decades and used Garmin with GPS since 2015, I've never had so much trouble
Garmins finally supports dual-band (L1+L5) and BeiDou on newest models but it's still not enough to compensate, I have to use a Stryd footpod to guarantee accurate distances/speed
btw BeiDou GPS blows away US GPS for number of sats and precision but despite Russia's GPS being legal in US, technically BeiDou is not
For resiliency reasons alone, it's been proposed to allow (stop software-disabling) BeiDou in the US, but the last time this was brought up, the administration ran out of time. It's a shame, because when there is precise coverage, it enables things like lane-level city navigation.
but of course this administration is never going allow China-anything like low cost electric cars even if it means saving people a fortune in gas
so hopefully in 2029 it can be looked at again
or maybe Dems will also get the Senate too and can be petitioned if they run out of corruption investigations before 2029
it is critical to explain to everyone who isn't technical that GPS is "read only" and no data is being sent to China via BeiDou (just like it's not sent to Russia's Glonass) because that apparently is some kind of weird misunderstanding
on that same note if they somehow made Starlink into a lower resolution GPS backup I'd even trust that too despite personally being anti-Musk everything
Read only or not, relying on Chinese or Russian gps data for increased accuracy even in civilian increases dependency no?
That seems like a bad idea to me. I’ve thought for about 20 years that increasing our dependence on anti democratic regimes was a risk, no matter what the benefits for global development etc. It’s not isolationist to want to only rely on your friends and not enemies.
(Which is why Europe needs to disentangle itself from the US as fast as possible).
It increases dependency but decreases risk because if there's an attack on a GPS system by an adversary, it's likely that they will not be attacking their own system at the same time. I'd rather have my enemy's open source, perfectly functional clock in my back pocket than be without the time.
If you are relying on it without a graceful fall back then it would be a problem. If you take it as a boost on top of existing capabilities then it is a pure win. In practice it can be hard to parse the two scenarios. People get used to thinking that something is available and it turns out that it was always leverage against them.
Whoops I don't know how I missed that in your links!
The weird part to me is that Glonass was not approved either, yet it's as openly as allowed as Galileo that went through a tedious FCC approval process that was invented later. Grandfathered or not, we're clearly not in a worse place using Russian tech for the last 15 years.
> BeiDou GPS blows away US GPS for number of sats and precision
Both BeiDou and GPS are supposed to be limited to 10m precision for civilians.
But, going down a rabbit hole, I found that BeiDou is way more accurate than 10m--3.6m and 2.6m outside and inside the Asia-Pacific region, respectively [1]. And that's with the most simple algorithm. It goes down to ~2.5m using dual-frequencies to account for atmospheric error.
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 accuracy on it's own, and doesn't include a number for precision between the two units.
My understanding is that the encrypted military-level GPS is much more robust against jamming and spoofing. There's probably a lot of capabilities we don't know that's classified, too.
M-Code is a new encrypted signal that is not fully operational yet. OCX was supposed to enable it.
GPS has always had the P(Y) code, which is an encrypted signal, at a higher chip rate than the C/A code that has been broadcast on L1 forever. The P(Y) code has its own interesting history of (semi-)codeless processing. If the US military is lucky, the history books will close on that by 2030: https://www.gps.gov/codelesssemi-codeless-gps-access-commitm... . (Currently, 21 GPS satellites broadcast L5.)
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.
It seems that all the device manufacturers (they mention Apple, Samsung, and Google) are using BeiDou anyway. I don't know if that includes Garmin watches, though.
This is only to make getting a fix faster - A-GPS downloads the almanac data via the internet (fast, but needs internet) instead of directly from the GPS satellites (slow but works everywhere). It doesn't make it any more accurate.
The linked actual research article did look at multiple GNSS systems. GPS is presumably being reported out of familiarity https://doi.org/10.1029/2026GL124645
Adjacent to that, I'm a bit surprised that there hasn't been a mass rollout of assisted GNSS in large cities. Maybe not full RTK, but something more than just delivering almanac being delivered.
Are the current GNSS solutions good enough (or too degraded?) in city jungles that there would not be any mass benefit? Too expensive to run a few base stations here and there?
This is exactly the sort of thing that leads to people getting reincarcerated after their electronic monitoring devices mistakenly report them leaving their homes.
Sounds like you could be a convict, have your gang interfere GPS on a local level but enough to have other people in the neighborhood notice, make a quick run for whatever you'd need to, and still claim plausible deniability.
I'm reading your article and it seems to be about police coming to check and realizing that the reporting of being miles away was in error, not people getting reincarcerted because of GPS incorrectly reporting they moved ~30 feet too far? One of these is much more insane than the other.
Not sure where your confusion is coming from. Have you never used GPS in a place with bad signal? Where it gets confused and you miss your turn? It's the same failure mode. Just the repercussions are getting arrested instead of getting off on the wrong exit.
I think the confusion is probably coming from the fact that the one reference to people being potentially re-incarcerated is buried right down the story.
> Harkins said that since last October, she has seen 30-40 people ordered back into custody based on these progress reports. When asked what can be done to improve CCSO’s EM program, Harkins said that the sheriff’s office needs to “properly and fully” investigate alleged violations before writing reports or taking actions.
The story is about GPS errors which end up making life hell for people under monitoring since they end up generating a Police response. If 80% alerts were false, then an error like this can result in a surge of these alerts. It is an important story to tell.
The monitoring device story seems important to tell but the problem seems to be related to monitoring devices, which are supposed to be accurate to 30 meters 90% of the time, being miles off or even reporting the wrong state. That kind of systematic failure does not make a few meters of displacement any more relevant, saying so really makes it sound like the problem is something significantly less egregious than the devices being incomprehensibly inaccurate - as if we have to solve space weather prediction to a new level of science to not have them report someone in Chicagoland as being in Delaware.
Just somewhat mildly important though, given that how do you even end up under house arrest.
Of course, it is true that even criminals deserve a diginified life, and it is also true that this trickles down into the life of normal law-abiding people too, so being aware there makes sense.
I would just tune down the empathy a bit. Not to zero, but below "making life hell".
__
And yes, the legal system in the US has problems, but that is a different debate, and hyperbole doesn't help there either.
You do not win the hearts of the people whose hearts you'd need to win to change those issues by talking about how bad it feels to have an ankle monitor.
As far as those people are concerned, it feeling bad is working as intended.
Okay but the claim is people are being re-arrested because of this "sort of thing". But I read the linked article, and it doesn't mention anyone getting re-arrested. There is only one situation described where the person is arrested and then let go after the cops got proof the alert was faulty.
So yes, it absolutely sucks that this technology is so inconvenient and bad but at the same time, the author and GP claims are not proved or truthful in totality (even in the article they posted).
We can agree GPS tracking sucks but also question claims that are not true. Also telling people to "calm down" over text when they are not even talking to you is very passive aggresive for no reason.
Consider that, from the justice system's point of view, there's no distinction between between someone breaking house arrest for a drug fix versus due to GPS error. They don't have the resource to investigate every single violation, so they always just assume that the device is infallible and that the human is lying.
That's why there's no data for someone getting rearrested due to GPS, and why the few instances where someone do prove an error is concerning.
>Also telling people to "calm down" over text when they are not even talking to you is very passive aggresive for no reason.
Your "This" quote was the least genuine comment I've seen on HN in a very long time. You took a comment and removed all context to complain about how it's wrong, when it wasn't wrong at all. There should be no doubt that GPS glitches can cause people with ankle monitors a lot of needless trouble, and "the system" likely won't believe it, and simply won't care.
If you had an ankle monitor, and someone wanted to fuck with you, it would be trivially easy to block or spoof GPS signals to put you back in jail. All it takes is an SDR and some software you can find on github. Think about that before you quip "This" again.
> This time the glitch was 33 feet, who's to say next time it couldn't be 3300 feet?
People who study this. This glitch was caused by unusual, structured, widespread distortions in the ionosphere. There's no known mechanism that would cause enough distortion to make the errors 100 times as large. There would also be other symptoms of any unknown cause.
https://claude.ai/share/5cc4163e-9cbf-47cd-9749-4bb55bca42fe if you don't mind discursions into safety of aviation navigation systems. Caution: Do not take the error bounds in the second half as relevant to errors for unaugmented single-frequency users; those users will see much bigger errors.
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.
Urban environments have larger buffer areas due to multipath interference.
The story you linked has examples about false alerts triggering in a different state.
Do you have any actual examples of 33 feet getting someone arrested? I’ve worked enough with GPS that I could tell you that any system with thresholds that low would result in everyone getting false triggers
According to this firm selling them, this model has <15ft error, usually 3-4 ft. Given the permissible area is entirely up to what the judge orders, it seems eminently plausible that someone confined to their apartment could be placed outside with a 33ft jump causing a false alarm.
At the very least, it's not enough evidence provided to claim the scenario is inherently impossible based on undefined "allowances" without any actual numbers for something completely dependent on the jurisdiction, monitoring software implementation, and attitude of the police officer/judge.
I also found Reddit anecdotes of getting alert texts stepping outside onto the street from their yard, or false alarms while still inside but not enough details were provided to be sure they were actually GPS and not RF so not as helpful.
It happened with both RF and GPS! The Cook County Sheriff's Office moved between the two at one point so it was possible to see the effects over time as folk moved over. Some people got more false alarms when moving to GPS, some got fewer. IIRC it was about even.
Maybe not intentionally (at least by the U.S. Government, but the consequences are far greater now.
Now that GPS has subsumed a large part of air navigation as more VOR and ILS approaches at non-towered airports are being left to fall into disrepair, it forces more and more aircraft operating in instrument conditions to fall back to a navigation system that may not operate to the tolerances that you need to shoot an approach to LPV minimums (which puts you close to 200 feet or so above the ground) or LNAV minimums (higher, but still pretty low to the ground). If you lose signal integrity, you abort the approach. You don't want to break out at minimums only to find that the runway is 33 feet to the left or right of the centerline when it's not a circling only approach where you're expecting it. If that field only has RNAV (GPS) approaches, you have to divert. Hopefully the alternate airport you filed has a ground based approach plate available that is authorized .
When SA was around, we had more VORs, more VOR and ILS approaches, and while NDBs (decades old radionavigation beacon that operated on the AM band) were on their way out, they were still around.
One of the reasons SA was discontinued was that if you knew the coordinates of a base station, you could correct for the error. Are airports not doing this already?
Actually, several airports are. So you have normal WAAS and it has a ground segment. Most (new) IFR certified GPS receivers installed in airplanes today are WAAS capable.
To that, you can augment something called GBAS (we used to call it Local Area Augmentation System but switched over to the ICAO name for it). It’s basically a ground station that sits at an airport and corrects for GPS errors where you need it most (airports definitely qualify here and that’s where you need the best GPS performance).
Ultimately, the FAA is going to go 100% GPS and it’ll fall back to the minimum number of land-based sources for redundancy. It’s about cost. The issues with GPS may cause them to push the timeline back and develop plans to mitigate the issue, but they’re too far down this path to stop now.
To meet its integrity budget, a GBAS needs at least triple redundancy, not just a single station.
If one has a lot of patience, one can read the details of how it works at https://elibrary.icao.int/product/299828 (along with SBAS, the ICAO name for what WAAS does; the constellations they can augment; GRAS, a weird hybrid between GBAS and SBAS that apparently went nowhere; ILS; VOR; DME; and VHF marker beacons). Annex 10 Vol I probably doesn't say explicitly that triple redundancy is required, because if you had a single receiver with an MTBF of something like 10 billion hours then you could use just that one.
This particular 30-foot error should go away almost entirely for future receivers that implement DFMC SBAS or ARAIM.
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. Nationally, this equates to an estimated half-billion dollars in lost earning potential, Griffin says."
So yeah, hard to believe was the right call. Very few farms were affected, but if we assume half of the total 900 million acres of farm land were, add 10% to get a round number, and guess it at a dollar per acre, we get the quoted big number.
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.
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.
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.
It's not reasonable because the error bars of each estimate compound and they may not even be normally distributed in the first place.
You should rather convolve probability distributions - assuming factors are independent - and if the IQR covers a huge range, perhaps orders of magnitude even, you should state that.
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.
It seems worth mentioning that the last time GPS had issues like this afaik, it was due to the US utilizing 'selective availability' due to national security issues. We used it somewhat famously during the 9/11 attacks.
Also the page 404's via archive.org, but information formerly from gps.gov can still be found here:
https://archive.ph/trwOo
Indeed, the link in the parent even says it hasn't been used since May 2000. So, yeah, it certainly wasn't used "famously".
Perhaps the commenter is thinking of the fact it was used globally prior to May 1, 2000. From a civilian point of view, GPS appeared to be invented around this time but it had actually been available for a couple of decades already, just in a degraded form that wasn't very useful.
Differential GPS was already in widespread use in many counties by 2000, which made "selective ability" pointless at it provided automatic corrections to the 'degraded' GPS signal.
I'm an Amazon driver and we heavily rely on GPS for delivering. We don't just use it for navigating, we also make each delivery inside of a geofence, and the delivery location is recorded and used for future routing. When the GPS says you're a block away from where you are, you're unable to make the delivery without contacting support. I've had days where GPS problems wasted a lot of my time, so I imagine it would be expensive if it happened across an entire region. On the other hand, these kinds of disruptions are already factored into the business model and planned for, so saying it cost an industry X amount of dollars is assuming that the industry was planning for ideal conditions in the first place.
It's strange that agriculture incurred so large losses, I would expect precision farming to rely on RTK (with relatively close reference base station at a fixed location).
The article doesn't mention, but how immune or affected were base station corrected RTK positioning systems?
It sounds a lot less dramatic if we can absorb such events with RTK base stations.
That does add the extra dependency of network links to get the RTK correction stream, unless some day it is standardized to be broadcast locally on FM or so.
I recall that event. It wasn’t the error that was the problem, it was that the units weren’t able to get fixes amid the solar storm, rendering the machines inoperable; save driving by hand, of course, but that isn’t practical with many modern planters.
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.
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.
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.
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.
101 comments
[ 0.21 ms ] story [ 77.0 ms ] threadI've run outside every morning for decades and used Garmin with GPS since 2015, I've never had so much trouble
Garmins finally supports dual-band (L1+L5) and BeiDou on newest models but it's still not enough to compensate, I have to use a Stryd footpod to guarantee accurate distances/speed
btw BeiDou GPS blows away US GPS for number of sats and precision but despite Russia's GPS being legal in US, technically BeiDou is not
* https://warontherocks.com/a-signal-point-of-failure-integrat...
* https://payloadspace.com/gps-faces-growing-competition-from-...
* https://en.wikipedia.org/wiki/BeiDou#GPS_vs._BeiDou_Capabili...
https://warontherocks.com/a-signal-point-of-failure-integrat...
but of course this administration is never going allow China-anything like low cost electric cars even if it means saving people a fortune in gas
so hopefully in 2029 it can be looked at again
or maybe Dems will also get the Senate too and can be petitioned if they run out of corruption investigations before 2029
it is critical to explain to everyone who isn't technical that GPS is "read only" and no data is being sent to China via BeiDou (just like it's not sent to Russia's Glonass) because that apparently is some kind of weird misunderstanding
on that same note if they somehow made Starlink into a lower resolution GPS backup I'd even trust that too despite personally being anti-Musk everything
The weird part to me is that Glonass was not approved either, yet it's as openly as allowed as Galileo that went through a tedious FCC approval process that was invented later. Grandfathered or not, we're clearly not in a worse place using Russian tech for the last 15 years.
Both BeiDou and GPS are supposed to be limited to 10m precision for civilians.
But, going down a rabbit hole, I found that BeiDou is way more accurate than 10m--3.6m and 2.6m outside and inside the Asia-Pacific region, respectively [1]. And that's with the most simple algorithm. It goes down to ~2.5m using dual-frequencies to account for atmospheric error.
[1] https://www.nature.com/articles/s41598-022-12012-y
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...
I am not sure how to interpret your link, though. It doesn't measure accuracy on it's own, and doesn't include a number for precision between the two units.
GPS has always had the P(Y) code, which is an encrypted signal, at a higher chip rate than the C/A code that has been broadcast on L1 forever. The P(Y) code has its own interesting history of (semi-)codeless processing. If the US military is lucky, the history books will close on that by 2030: https://www.gps.gov/codelesssemi-codeless-gps-access-commitm... . (Currently, 21 GPS satellites broadcast L5.)
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.
https://www.reuters.com/technology/us-agency-probes-risks-fo...
Are the current GNSS solutions good enough (or too degraded?) in city jungles that there would not be any mass benefit? Too expensive to run a few base stations here and there?
1. Not today. November 2025. They don't make it clear.
2. It is unclear what is the source of the claim.
3. Navigation issues happened before, they state it right there. They were more disruptive as well.
Every presented link seem to have this awful Cluodflare js challenge.
Bad article overall.
The author has articles all over the topics. Everything is sensationalized.
My brother in christ it's the first 3 words of the article.
7th paragraph of the article states the source, and contains a link to research paper where they go into great detail.
He's talking about your first (incorrect) claim. The article begins "In November 2025"
Some reporting I did on the topic a few years back: https://chicagoreader.com/news/many-on-house-arrest-in-cook-...
As in, GPS being off by 33 feet?
> leads to people getting reincarcerated
I'm reading your article and it seems to be about police coming to check and realizing that the reporting of being miles away was in error, not people getting reincarcerted because of GPS incorrectly reporting they moved ~30 feet too far? One of these is much more insane than the other.
Also wrote this one, hopefully it helps your confusion: https://chicagoreader.com/news/false-alarms/
Not really sure what it has to do with tech though. That’s a problem with how certain humans behave, not ancillary technology.
> Harkins said that since last October, she has seen 30-40 people ordered back into custody based on these progress reports. When asked what can be done to improve CCSO’s EM program, Harkins said that the sheriff’s office needs to “properly and fully” investigate alleged violations before writing reports or taking actions.
Of course, it is true that even criminals deserve a diginified life, and it is also true that this trickles down into the life of normal law-abiding people too, so being aware there makes sense.
I would just tune down the empathy a bit. Not to zero, but below "making life hell".
__
And yes, the legal system in the US has problems, but that is a different debate, and hyperbole doesn't help there either.
You do not win the hearts of the people whose hearts you'd need to win to change those issues by talking about how bad it feels to have an ankle monitor.
As far as those people are concerned, it feeling bad is working as intended.
You're cherry-picking a single word to start a pointless internet argument? Calm down. Nobody claimed this exact event lead to problems for anyone.
This is what OP actually said:
>>This is exactly the sort of thing
Yes, this absolutely is the sort of thing. No, 33 feet isn't "the thing" but GPS glitching is the sort of thing at a different increment.
So yes, it absolutely sucks that this technology is so inconvenient and bad but at the same time, the author and GP claims are not proved or truthful in totality (even in the article they posted).
We can agree GPS tracking sucks but also question claims that are not true. Also telling people to "calm down" over text when they are not even talking to you is very passive aggresive for no reason.
That's why there's no data for someone getting rearrested due to GPS, and why the few instances where someone do prove an error is concerning.
Your "This" quote was the least genuine comment I've seen on HN in a very long time. You took a comment and removed all context to complain about how it's wrong, when it wasn't wrong at all. There should be no doubt that GPS glitches can cause people with ankle monitors a lot of needless trouble, and "the system" likely won't believe it, and simply won't care.
If you had an ankle monitor, and someone wanted to fuck with you, it would be trivially easy to block or spoof GPS signals to put you back in jail. All it takes is an SDR and some software you can find on github. Think about that before you quip "This" again.
People who study this. This glitch was caused by unusual, structured, widespread distortions in the ionosphere. There's no known mechanism that would cause enough distortion to make the errors 100 times as large. There would also be other symptoms of any unknown cause.
https://claude.ai/share/5cc4163e-9cbf-47cd-9749-4bb55bca42fe if you don't mind discursions into safety of aviation navigation systems. Caution: Do not take the error bounds in the second half as relevant to errors for unaugmented single-frequency users; those users will see much bigger errors.
33 feet is well within the allowances IIRC. Varies by state.
The story you linked has examples about false alerts triggering in a different state.
Do you have any actual examples of 33 feet getting someone arrested? I’ve worked enough with GPS that I could tell you that any system with thresholds that low would result in everyone getting false triggers
At the very least, it's not enough evidence provided to claim the scenario is inherently impossible based on undefined "allowances" without any actual numbers for something completely dependent on the jurisdiction, monitoring software implementation, and attitude of the police officer/judge.
https://www.youtube.com/shorts/o0sPXL9C53g
I also found Reddit anecdotes of getting alert texts stepping outside onto the street from their yard, or false alarms while still inside but not enough details were provided to be sure they were actually GPS and not RF so not as helpful.
Now that GPS has subsumed a large part of air navigation as more VOR and ILS approaches at non-towered airports are being left to fall into disrepair, it forces more and more aircraft operating in instrument conditions to fall back to a navigation system that may not operate to the tolerances that you need to shoot an approach to LPV minimums (which puts you close to 200 feet or so above the ground) or LNAV minimums (higher, but still pretty low to the ground). If you lose signal integrity, you abort the approach. You don't want to break out at minimums only to find that the runway is 33 feet to the left or right of the centerline when it's not a circling only approach where you're expecting it. If that field only has RNAV (GPS) approaches, you have to divert. Hopefully the alternate airport you filed has a ground based approach plate available that is authorized .
When SA was around, we had more VORs, more VOR and ILS approaches, and while NDBs (decades old radionavigation beacon that operated on the AM band) were on their way out, they were still around.
To that, you can augment something called GBAS (we used to call it Local Area Augmentation System but switched over to the ICAO name for it). It’s basically a ground station that sits at an airport and corrects for GPS errors where you need it most (airports definitely qualify here and that’s where you need the best GPS performance).
Ultimately, the FAA is going to go 100% GPS and it’ll fall back to the minimum number of land-based sources for redundancy. It’s about cost. The issues with GPS may cause them to push the timeline back and develop plans to mitigate the issue, but they’re too far down this path to stop now.
If one has a lot of patience, one can read the details of how it works at https://elibrary.icao.int/product/299828 (along with SBAS, the ICAO name for what WAAS does; the constellations they can augment; GRAS, a weird hybrid between GBAS and SBAS that apparently went nowhere; ILS; VOR; DME; and VHF marker beacons). Annex 10 Vol I probably doesn't say explicitly that triple redundancy is required, because if you had a single receiver with an MTBF of something like 10 billion hours then you could use just that one.
This particular 30-foot error should go away almost entirely for future receivers that implement DFMC SBAS or ARAIM.
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. Nationally, this equates to an estimated half-billion dollars in lost earning potential, Griffin says."
So yeah, hard to believe was the right call. Very few farms were affected, but if we assume half of the total 900 million acres of farm land were, add 10% to get a round number, and guess it at a dollar per acre, we get the quoted big number.
https://farmdocdaily.illinois.edu/2024/05/how-will-the-gps-o...
https://shiny.agmanager.info/cottonBotsDev/
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.
[1] https://www.bloomberg.com/features/2025-tesla-dangerous-door...
Also the page 404's via archive.org, but information formerly from gps.gov can still be found here: https://archive.ph/trwOo
Edit: The selective availability page moved to https://www.gps.gov/selective-availability
I have not been able to locate any source that backs up this claim.
Perhaps the commenter is thinking of the fact it was used globally prior to May 1, 2000. From a civilian point of view, GPS appeared to be invented around this time but it had actually been available for a couple of decades already, just in a degraded form that wasn't very useful.
Differential GPS was already in widespread use in many counties by 2000, which made "selective ability" pointless at it provided automatic corrections to the 'degraded' GPS signal.
https://en.wikipedia.org/wiki/Differential_GNSS
https://news.ycombinator.com/item?id=49500504 Cheap GPS jammers are filling the world with navigation dead zones (wsj.com) 3 days ago
https://news.ycombinator.com/item?id=48606271 Satellite reveals immense scale of GPS signal tampering (space.com) 3 months ago
The article doesn't mention, but how immune or affected were base station corrected RTK positioning systems?
It sounds a lot less dramatic if we can absorb such events with RTK base stations.
That does add the extra dependency of network links to get the RTK correction stream, unless some day it is standardized to be broadcast locally on FM or so.
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.
https://en.wikipedia.org/wiki/Electro_Gyrocator