While we're on the subject of maps-related bugs, I was recently borrowing a new Tesla Model Y and took it on a RORO ferry. After the crossing, the car’s GPS was convinced I was still at the port where I had departed from. I restarted it a couple of times, but nothing. I drove off using Waze on my phone instead of the car's navigation. The map on the car kept moving relative to the direction I was driving, so the navigation was showing me driving into the sea and eventually started complaining that it would be impossible to find a charger.
Approximately 5 hours later, just as I was about to arrive, the car finally managed to figure out my correct location.
Exciting trip, not a huge fan of Teslas, but their charger planning is really nice. It was very unpleasant to suddenly lose it.
I just genuinely wonder how such a bug can actually occur, surely you'd update the GPS fix more often than every couple of hours. Hard to imagine the car just suddenly couldn't get a GPS fix for hours either. But if it did somehow totally lose the ability to use GPS, the car must have a pretty good dead reckoning system given how well it was responding to my changes in direction.
On a vaguely related note, driving 3000 kilometers through Europe in an electric car was surprisingly nice. Certainly didn't affect the length of the trip nearly as much as I'd have expected, but it was certainly super annoying to try and figure out the optimal rate of travel on the Autobahn. Charging at Tesla's supercharges was vastly more expensive than I expected, the "fuel" costs weren't much lower than what you could easily reach with a diesel car.
I had a Volvo XC90 that “jumped” off the interstate and onto a parallel mountain road east of Knoxville. It did its best to track along those roads and somehow made its way into North Carolina. But even when I was back in Chicago, it was still stuck in NC trying to find a way off those mountain roads. Dozens of on/off cycles did nothing. I disconnected the battery overnight and that didn’t work. At the next service appointment, the dealer had to do a full firmware reset to wipe the memory and get it working again.
It amazed me that Volvo programmed an SUV to disbelieve that it could ever actually leave a road.
Last summer traveling down a rural road in southwestern Ontario, Apple maps told me to return to the route. We hadn't turned in 10 kilometers, but it was showing that we were 200 meters into a cornfield.
I don't think I could have ended up there if I tried in the Golf we were in. Nice try.
My kids thought it was the funniest thing, but it's a good technology lesson.
In Boston it's a very frequent occurrence to be driving in the Central Artery Tunnel and have your map software think you're on the surface, or vice versa, or to be on a highway overpass and again have it think you're on a surface road that is inaccessible from your location. You get used to it.
This seems like an entirely different level of craziness, though.
Yeah I remember back in the early 2000s before phones had turn-by-turn navigation, there were PDAs to do it and it was common for the software to just ask whether you were driving on the surface road or an elevated viaduct.
That's no excuse for disbelieving GPS for extended periods of time.
Google Maps gets it right: it tried to keep you on road, but only for a few tens of seconds. After that, if you are in the middle of uncharted territory, it'll show the marker there.
(This is probably because Google Maps can be used for walking/biking too)
Well, when I’m driving in Kyiv, and there is an air raid alert, usually my car navigation starts to derp, and after a few minutes it thinks that it’s suddenly in Lima, Peru.
Not that I mind too much, I know how to get around without navigation.
It does teleport to Peru but it also fast-forwards time to about a year into the future, which caused my car to think its overdue for that oil change. It even synced that back to the headquarters and I got an email asking me to take it to service.. (and arriving there on the wrong side of the Dnieper, I just decided to wait it out)
Wish we could put it into a manual mode where you just reset it's position once and then it updates based on wheel encoders & snapping to roads.
The technology should be resilient against GPS spoofing. If it “knows” it never left the mountain road, it’s not crazy to design it to reject an anomalous GPS signal, which might be wrong or tampered with.
I think the likelihood of that happening is significantly less than the likelihood that a car took a new road or other path not show in the cars mapping data.
>(This is probably because Google Maps can be used for walking/biking too)
Please don't do that. The map is simply not good enough and does not have enough context (road quality, terrain, trail difficulty) for anything but very causal activity. Even then I highly recommend to use a proper map, electronic or paper.
It has a lot more map data accessible and you can even overlay National Park Service maps, land ownership, accurate cell service grids, mountain biking trails, weather conditions and things like that.
Disclaimer: Just because you see a route on a map, digital or paper, does not mean it is passable today. Or it may be passable but at an extremely arduous pace.
We used the walking directions for dual sport motorcycles once. It was pretty nice. We did have a few places where it became sketchy. Those and maybe more places would be sketchy for walking too. Not that google maps could do much about it. Terrain is a living thing. These were mostly huge cracks in the earth due to rain water.
Trail? Terrain? I use it for walking for 10-20mins around a (mostly flat) city and I expect that’s what 90% of people use it for, the comment didn’t mention hiking
It depends what you are doing but for hill walking in Italy I found the footpathapp.com app good. There are no decent paper maps in the area I go and Google maps are also rubbish for local paths but the app kind of draws in paths based on satellite images I think and you can draw on it to mark the ones you've been on.
Yeah, that is my guess, there must have been bug, issues where GPS suddenly teleports you. One way to remedy that is to give the roads virtual walls so what ever GPS weirdness comes in, the location service will at least put the car close to its "previous" location for some time.
My dad used to have a crappy aftermarket GPS in his car that did the same thing. It would get lost dozens of miles away, and then hundreds of miles away.
The explanation I found online at the time was that a GPS receiver needs to download data about the exact orbits of all GPS satellites from time to time. Satellites slowly lose altitude and change their orbits. Up-to-date information is constantly broadcasted by every satellite, but it takes about 15 minutes for a device on the ground to download this dataset.
Most GPS devices do this automatically whenever they get the chance. But if your GPS is somehow unable to stay online for 15 consecutive minutes (bad firmware, faulty memory, tunnels, underground parking lots, etc), it will be relying on increasingly outdated info and drift far off its actual location.
There's no way a modern smart phone or car relies on those ephemeris transmissions. They all just get it from the internet, which takes less than a second. That's one of the reasons why a smart phone has a reliable GPS fix basically instantly after being booted up, while old-school offline GPS units needed minutes to get a fix.
That's only the case for non-internet connected GPS units. Throwback to the early 2000s when my family car had such a unit, which, after having been turned on, would require ~15 minutes of waiting before it became functional. Funnily, I remember the mapping app would refuse to use the device clock and only use the time from GPS satellites. So at least you would know you need to wait if it didn't know the current time.
Well, that's certainly not the case. Each satellite transmits a low-precision almanac to the receiver that helps it lock onto the others, as well as a higher-resolution ephemeris that provides the necessary pseudorange accuracy for that particular SV.
But it's true that neither of those factors accounts for miles of error. That has to come down to either poor sky coverage/signal strength, poor software, or (more likely) both.
2. Car entered dead reconning mode used for tunnels and such
3. Car left ferry, acquired GPS
Then either:
4a. Location via dead reconning vasty disagreed with GPS because the car doesn't know about the ferry's movements, triggering some kind of failsafe.
Or:
4b. There's just a plain old bug in the condition to switch back to GPS and maybe people haven't noticed because you don't get as badly desynced in a tunnel.
>the car must have a pretty good dead reckoning system
Yeah all the pieces are there: accelerometers and gyros for stability control, compass for navigation, and the wheel speed sensors give you exact distance traveled.
My local roro ferry drops you off pretty close to downtown. If you don't get a good fix as you get off the boat before you get into the urban canyon, satnav is pretty hopeless for a few minutes.
Doesn't usually take 5 hours to figure out where it is though. At least not on my vehicles, even the one that's always getting confused.
Dead reckoning shouldn't be a problem for a built-in nav device that has access to the car's odometer (or at least its speed). But as long as the car itself isn't moving, because it's parked in a ferry's car deck, I reckon (SCNR) it shouldn't do any dead reckoning...
TomTom's have for at least 15 years or so. They have accelerometers to measure the motion when cut off from the GPS satellites. I worked there, knew the guy who developed it, and saw him give a presentation about it.
That's cool... so I guess this works something along the ways of "calculate the speed via GPS before entering the tunnel, and then try to update this speed using the data from the accelerometer while in the tunnel"? Because as long a the car is moving at constant speed in a straight line, the accelerometer shouldn't register anything...
Well it registers gravity, so you can detect i.e. driving off a cliff. ;)
What helps is that tunnels don't usually branch, so once you're in it, your path is usually quite predictable.
TomTom maps also have a statistical model of what speed is expected along each stretch of road by hour and weekday/weekend (not 7 individual days, but 2 kinds of days). But I don't know if it uses that to help estimate your expected speed when dead reckoning, it's actually for route planning.
One of my co-workers came up with the great idea of gamifying driving: maintain a real time speed leader board, showing the top ten speeders along any stretch of road! So on every road in the world you could compete with other TomTom users who drove it. Kind of like checking in with 4Square, but more fun and dangerous! TomTom legal did not approve.
I suggested gamifying and monetizing driving with TomTomagotchi, a virtual pet that gets depressed if you don't drive it around enough, begs you to visit interesting landmarks and sponsored points of interest, like driving through McDonalds to feed it, or through the park to let it take a shit, or driving fast enough to make the leaderboard to entertain it. I'm sure Bandai's lawyers wouldn't approve.
I swapped out the satnav in a 2008 Honda for a modern unit and the car had a “speed pulse” wire. I looked it up and that wire is used for dead reckoning.
A practical issue is that GPS can be spoofed relatively easily. If autonomous driving became a thing, and ubiquitous, with vehicles that prioritized remote over local consistency, then a single GPS spoof could cause some interesting things to happen. This is probably a concern that does drive decisions, at least to a degree. It creates a weird scenario where you kind of need to trust GPS, but you simultaneously also can't treat it as authoritative.
OTOH creating a dumb user experience for a fairly common scenario, to try to preempt a hypothetical scenario is probably not a great idea. A fun problem to think about, though it may be completely unrelated to this issue.
I do hope self-driving software works out a better system, before it becomes common place. Autopilot has been incorporating GPS in aviation for decades, and it's still surprisingly common to have major problems when a loss of GPS occurs.
Every swept-wing jet has a tendancy to enter a positive feedback loop of rolling and yawing, called a dutch roll, when flying at altitude, so even when not using autopilot, an active system is needed to fly straight and level. If the Phenom 300 doesn't have a valid GPS signal, that system fails.
If it becomes common place, spoofing is easy to counter. Directionality and parallax of the signal is enough to figure out the true signal, all it requires is an additional antenna.
This won't prevent jamming, that requires a different mechanism, but spoofing should be prevented.
> On a vaguely related note, driving 3000 kilometers through Europe in an electric car was surprisingly nice.
Having done a number of multiple-thousand km trips in Europe in an EV (not a Tesla, nobody buys those anymore) — it's amusing how non-EV muggles think this is somehow an ordeal. It's just fine! There are drawbacks: you do have to use your brain and plan ahead more than you do when burning dinosaurs. But I found that the 20-30 minute stops every 2h really improve how I feel after a day or two of driving.
Agreed about prices: there is gouging going on with some crazy margins. When charging at home, an EV is 2-4x less expensive per km than a gasoline-powered car, but when fast-charging on a road trip the cost of energy is nearly the same.
> But I found that the 20-30 minute stops every 2h really improve how I feel after a day or two of driving.
I honestly started considering this a feature. I am a huge believer in "productive friction" - where some things are intentionally made annoying or hard so that humans avoid them - and this is a really good example.
Muggles, in Harry Potter books, are non-magic people, who do not have magic, do not understand it, have a lot of misconceptions about it, and fear it. :-)
Back in the days of MapQuest there was a (usually) very good site called mapsonus.com, but it evidently had one of the ferries that crossed Boston Harbor in its map as a zero distance link.
Since it was offline, the bug was obvious although a bit frustrating - you had to put in multiple waypoints to make it forget its urge to send you on the ferry to Hull when you were trying to get to parts of the South Shore.
I suspect that my Tesla adjusts its location based on dead reckoning after losing GPS lock except that it assumes that I'm driving forwards. I.e. If I reverse out of my garage, then the map ends up in the wrong place and now I'm driving parallel to the road!
As you're mentioning a RO/RO ferry, recently, and Europe... are you sure you weren't in a GPS-denied environment, where the car (correctly) detected that GPS was jammed or spoofed and ignored it?
Possibly it was using WPS keyed to the ferry's WiFi and didn't consider the possibility that the ferry itself could move out of where it was registered (ie, the port)?
Perhaps the car is programmed to ignore all external signals for a while if it detects significant disagreement for a prolonged time, as might have happened if it had access to both WPS and GPS during the ferry ride. In such cases it would be safe to assume that something is being spoofed, and fall back to INS.
Civilian GPS (as in, the DoD’s Navstar) alone isn’t accurate enough to actually place you on a specific road. To compensate, auto navigation systems will snap you to the nearest road parallel to your current heading. Tesla likely didn’t consider the edge case of ferries and other off road situations in their mapping software and you hit some corner case bug.
This used to be true, but the DoD turned off "selective availability" (the intentional degrading of the civilian signal) back in 2000, and the current generation of satellites do not have the capability (https://www.gps.gov/selective-availability). What they do have though is a separate, encrypted, military broadcast that can be used for those purposes (I think the plan in those situations is to turn off civilian GPS entirely - but I think that there's no reason for that, now, due to the other navigation systems like GLONASS).
Even without selective availability gps is only accurate to within about 30’ in normal urban conditions which is more than enough to punt you over to a side street without heuristics on top.
One hypothesis I can offer is that your car could not, for whatever reason, use assisted gps to download the almanach which relies on mobile networks. Gps devices that download the almanac via gps itself can take up to twelve hours (in higher latitudes i think)!
I wonder if it's using a compass and odometry (distance) with dead reckoning. A strange choice when GPS is available, but it would account for the map moving in the car's direction and it not changing locations when it moved without rolling (ferry).
Almost certainly. GPS is not only easily jammed, but easily spoofed. If the car believed GPS instead of its own eyes, so to speak, then there’s significant potential that you’d see glitches more often. It could also be something of a safety risk when using its self-driving capabilities.
Makes me wonder why there isn't a UI feature within easy reach to let the user drag a pin on a map and tap "I know I'm here right now"... and if that agrees with where GPS also indicates, let's it reset its notion of "I must be getting spoofed right now" thoughts in addition to calibrating other notions of current location.
In addition to sibling's comments about jamming and self driving safety, there are many driving situations where there is no or poor GPS reception: tunnels, double deck bridges, double deck freeways, underpasses, urban canyons, actual canyons, etc. Also regional problems. The GPS constellation is in a 55° inclination, so if you are north of ~55N, or south of ~55S, you need a clear view of the southern/northern sky, respectfully, for reception, since there will be no overhead satellites.
Tangentially, why won't computerized maps - e.g., Apple Maps, Google, etc. - show a scale? Generally they'll show one as you pinch/zoom, but it disappears when you release your fingers.
Sometimes I just want to eyeball distances, and not plug in addresses and request routes for everything.
I know not everyone always wants it, but a scale is a fundamental feature of mapping! Scale almost defines mapping.
Edit: One reason I ask is because I suspect some technical limitation.
I thought it'd be cool if the scale were shown by some channel, like coloring roads (pink at neighborhood scale, blue, green as you zoom out) so you could intuit the scale at a glance.
With map simplification and symbolic markers (roads are the same thickness at multiple scales) it can be really hard to figure out distances. I was once going to a less populated area, based on my local intuition I thought the distance between two locations was a maybe 30m walk max if I missed the bus, but it turned out it was a 3h walk.
I made a comment earlier that was rightly flagged for its tone, and I would like to restate the technical point more constructively.
The post author, Dan Piponi, clearly knows about fractals, but his post raises the question of whether asking Fermi questions in interviews is actually effective. I am skeptical that such questions would have prevented this type of bug.
I suspect the issue stems from small measurement imprecisions accruing over long distances, which is—in my view—tied to the fractal nature of roads traversing natural landscapes.
However, as others have pointed out, it may also be tied to road closures: if closed segments are set to a higher length internally (to discourage routing), these values might be getting summed up blindly over longer distances.
None of these issues would have been prevented by being good at estimating quantities alone.
Apologies again for the unconstructive tone of my previous comment.
A pure spirit is required to admit your own mistake. Don’t be let down by an error, never lose the opportunity to fix it. May this be of example to everyone to keep improving this already wonderful but not perfect community.
I’ve had that bug a few times. I think it’s related to some roads being closed and/ or under reconstruction. I’ve seen this happen multiple times on the same route, and it always fixed itself after I passed the construction site.
So it might be a hack to get it to take another way -- rather than invent some way of marking a road section as being closed, mark it as being 1000 miles long?
> One of my AirTags is inexplicably 1600 miles away in Texas. It's one of my floating ones that I throw into bags when traveling as needed.
> Maybe it dropped out of my bag only to be found by someone who thought it'd be fun to confuse the owner. Or maybe it became e-waste to be dumped in another country.
The distance is more than the circumference of the Earth. If you wrapped a rope around the planet at the equator, the length would be around 25k miles.
That's fair, but even the commonly cited longest route [0] you could theoretically walk without intentional detours, Cape Town, South Africa to Magadan, Russia, is approximately 14k miles.
If you account for the satellite being further away because it would be above the point the distance works out okay - except that geostationary satellites go around the equator and that is a thousand miles away from that.
Maps has gone backwards on CarPlay, too. Hysteresis is completely broken - I stop at a traffic light and the map will jump back and forth between two resolutions, often once a second, which is extremely distracting.
I also love that Find My says my partner was "last seen" at home "8,912 days ago".
Apple just doesn't give as much of a shit any more.
The most annoying thing about iPhone Maps for me is the inaccuracy of the direction indicator. I've googled and it doesn't seem to be a universal complaint even though I've experienced this on multiple devices over the years even after following instructions to re-calibrate multiple times. Maybe I've just been unlucky.
It intensely frustrating to use maps for direction finding while walking or cycling when the app is telling you are facing one direction when in fact you are facing another.
Settings - privacy - location services - system services - compass calibration. Make sure it’s enabled. In a bout of paranoia I disabled location for everything I didn’t recognize as necessary and then it took me many months to find out why compass cone behaves funny in mapping apps.
The flight distance is 2,520 miles, Google puts road distance at 3,179 mi = 1.26x, 29,905 mi is 11.87x. Road miles are not even close to accounting for it, it’s just a bug.
Being a little bit clever can lead you to make some pretty bad mistakes.
Yes, the distance according to roads can be different from the distance as the crow flies. No, it cannot realistically be 10x the distance when the crow's distance is 2500 miles.
You would have to take an implausible number of wrong turns to have a chance of making it anywhere near that long a drive. For an example of a shorter but still entirely unreasonable path: Head straight north all the way to the pole, continue south to the pole, continue north to the latitude of the destination, then head due east until arrival.
While we're on the subject of maps-related bugs, I was recently borrowing a new Tesla Model Y and took it on a RORO ferry. After the crossing, the car’s GPS was convinced I was still at the port where I had departed from. I restarted it a couple of times, but nothing. I drove off using Waze on my phone instead of the car's navigation. The map on the car kept moving relative to the direction I was driving, so the navigation was showing me driving into the sea and eventually started complaining that it would be impossible to find a charger.
Approximately 5 hours later, just as I was about to arrive, the car finally managed to figure out my correct location.
Exciting trip, not a huge fan of Teslas, but their charger planning is really nice. It was very unpleasant to suddenly lose it.
I just genuinely wonder how such a bug can actually occur, surely you'd update the GPS fix more often than every couple of hours. Hard to imagine the car just suddenly couldn't get a GPS fix for hours either. But if it did somehow totally lose the ability to use GPS, the car must have a pretty good dead reckoning system given how well it was responding to my changes in direction.
On a vaguely related note, driving 3000 kilometers through Europe in an electric car was surprisingly nice. Certainly didn't affect the length of the trip nearly as much as I'd have expected, but it was certainly super annoying to try and figure out the optimal rate of travel on the Autobahn. Charging at Tesla's supercharges was vastly more expensive than I expected, the "fuel" costs weren't much lower than what you could easily reach with a diesel car.
I had a Volvo XC90 that “jumped” off the interstate and onto a parallel mountain road east of Knoxville. It did its best to track along those roads and somehow made its way into North Carolina. But even when I was back in Chicago, it was still stuck in NC trying to find a way off those mountain roads. Dozens of on/off cycles did nothing. I disconnected the battery overnight and that didn’t work. At the next service appointment, the dealer had to do a full firmware reset to wipe the memory and get it working again.
It amazed me that Volvo programmed an SUV to disbelieve that it could ever actually leave a road.
Last summer traveling down a rural road in southwestern Ontario, Apple maps told me to return to the route. We hadn't turned in 10 kilometers, but it was showing that we were 200 meters into a cornfield.
I don't think I could have ended up there if I tried in the Golf we were in. Nice try.
My kids thought it was the funniest thing, but it's a good technology lesson.
In Boston it's a very frequent occurrence to be driving in the Central Artery Tunnel and have your map software think you're on the surface, or vice versa, or to be on a highway overpass and again have it think you're on a surface road that is inaccessible from your location. You get used to it.
This seems like an entirely different level of craziness, though.
Yeah I remember back in the early 2000s before phones had turn-by-turn navigation, there were PDAs to do it and it was common for the software to just ask whether you were driving on the surface road or an elevated viaduct.
The problem is that roads are continually being built and maps aren’t always as quick to be updated.
There are also private paths that aren’t public roads but are still intended for vehicles.
That's no excuse for disbelieving GPS for extended periods of time.
Google Maps gets it right: it tried to keep you on road, but only for a few tens of seconds. After that, if you are in the middle of uncharted territory, it'll show the marker there.
(This is probably because Google Maps can be used for walking/biking too)
Well, when I’m driving in Kyiv, and there is an air raid alert, usually my car navigation starts to derp, and after a few minutes it thinks that it’s suddenly in Lima, Peru.
Not that I mind too much, I know how to get around without navigation.
GPS jamming for incoming drones?
Yep
It does teleport to Peru but it also fast-forwards time to about a year into the future, which caused my car to think its overdue for that oil change. It even synced that back to the headquarters and I got an email asking me to take it to service.. (and arriving there on the wrong side of the Dnieper, I just decided to wait it out)
Wish we could put it into a manual mode where you just reset it's position once and then it updates based on wheel encoders & snapping to roads.
Well you can also drive off road too.
> That's no excuse for disbelieving GPS for extended periods of time.
You've got it backwards. I was explaining why GPS should take priority over mapping data. Not the other way around.
They’re saying that not prioritising (disbelieving) GPS data is bad, hence there’s no excuse for it
So that’s the same thing you’re saying
Yes, I know. And saying that as a rebuttal to a comment where I’d said the same. Hence my reply ;)
The technology should be resilient against GPS spoofing. If it “knows” it never left the mountain road, it’s not crazy to design it to reject an anomalous GPS signal, which might be wrong or tampered with.
I think the likelihood of that happening is significantly less than the likelihood that a car took a new road or other path not show in the cars mapping data.
>(This is probably because Google Maps can be used for walking/biking too)
Please don't do that. The map is simply not good enough and does not have enough context (road quality, terrain, trail difficulty) for anything but very causal activity. Even then I highly recommend to use a proper map, electronic or paper.
yeah I'm not gonna open some paid trail map or buy a paper map so I can walk across my local city park and give my friends a pin to find me...
I've found Organic Maps to be better than any paid app for hiking (and I've tried a bunch) for what it's worth
I find Gaia Maps even better for the boonies.
It has a lot more map data accessible and you can even overlay National Park Service maps, land ownership, accurate cell service grids, mountain biking trails, weather conditions and things like that.
Disclaimer: Just because you see a route on a map, digital or paper, does not mean it is passable today. Or it may be passable but at an extremely arduous pace.
For anything other than driving Organic Maps (iOS) or OSMand (Android) are the very best.
We used the walking directions for dual sport motorcycles once. It was pretty nice. We did have a few places where it became sketchy. Those and maybe more places would be sketchy for walking too. Not that google maps could do much about it. Terrain is a living thing. These were mostly huge cracks in the earth due to rain water.
Trail? Terrain? I use it for walking for 10-20mins around a (mostly flat) city and I expect that’s what 90% of people use it for, the comment didn’t mention hiking
It depends what you are doing but for hill walking in Italy I found the footpathapp.com app good. There are no decent paper maps in the area I go and Google maps are also rubbish for local paths but the app kind of draws in paths based on satellite images I think and you can draw on it to mark the ones you've been on.
A badly programmed Kalman filter perhaps
Yeah, that is my guess, there must have been bug, issues where GPS suddenly teleports you. One way to remedy that is to give the roads virtual walls so what ever GPS weirdness comes in, the location service will at least put the car close to its "previous" location for some time.
> It amazed me that Volvo programmed an SUV to disbelieve that it could ever actually leave a road.
Only for footpaths in residential areas.
I wonder what class of vehicles is least likely to go off roading?
My dad used to have a crappy aftermarket GPS in his car that did the same thing. It would get lost dozens of miles away, and then hundreds of miles away.
The explanation I found online at the time was that a GPS receiver needs to download data about the exact orbits of all GPS satellites from time to time. Satellites slowly lose altitude and change their orbits. Up-to-date information is constantly broadcasted by every satellite, but it takes about 15 minutes for a device on the ground to download this dataset.
Most GPS devices do this automatically whenever they get the chance. But if your GPS is somehow unable to stay online for 15 consecutive minutes (bad firmware, faulty memory, tunnels, underground parking lots, etc), it will be relying on increasingly outdated info and drift far off its actual location.
There's no way a modern smart phone or car relies on those ephemeris transmissions. They all just get it from the internet, which takes less than a second. That's one of the reasons why a smart phone has a reliable GPS fix basically instantly after being booted up, while old-school offline GPS units needed minutes to get a fix.
That's only the case for non-internet connected GPS units. Throwback to the early 2000s when my family car had such a unit, which, after having been turned on, would require ~15 minutes of waiting before it became functional. Funnily, I remember the mapping app would refuse to use the device clock and only use the time from GPS satellites. So at least you would know you need to wait if it didn't know the current time.
_deleted incorrect statement_
Well, that's certainly not the case. Each satellite transmits a low-precision almanac to the receiver that helps it lock onto the others, as well as a higher-resolution ephemeris that provides the necessary pseudorange accuracy for that particular SV.
But it's true that neither of those factors accounts for miles of error. That has to come down to either poor sky coverage/signal strength, poor software, or (more likely) both.
You are correct, there's several words of data at the end of the packet that is a low precision almanac
My guess would be:
1. Car entered ferry, loses GPS
2. Car entered dead reconning mode used for tunnels and such
3. Car left ferry, acquired GPS
Then either:
4a. Location via dead reconning vasty disagreed with GPS because the car doesn't know about the ferry's movements, triggering some kind of failsafe.
Or:
4b. There's just a plain old bug in the condition to switch back to GPS and maybe people haven't noticed because you don't get as badly desynced in a tunnel.
>the car must have a pretty good dead reckoning system
Yeah all the pieces are there: accelerometers and gyros for stability control, compass for navigation, and the wheel speed sensors give you exact distance traveled.
My local roro ferry drops you off pretty close to downtown. If you don't get a good fix as you get off the boat before you get into the urban canyon, satnav is pretty hopeless for a few minutes.
Doesn't usually take 5 hours to figure out where it is though. At least not on my vehicles, even the one that's always getting confused.
It probably doesn't do dead reckoning even in tunnels
And maybe the system sucks to get the GPS almanac if badly desynced
Dead reckoning shouldn't be a problem for a built-in nav device that has access to the car's odometer (or at least its speed). But as long as the car itself isn't moving, because it's parked in a ferry's car deck, I reckon (SCNR) it shouldn't do any dead reckoning...
TomTom's have for at least 15 years or so. They have accelerometers to measure the motion when cut off from the GPS satellites. I worked there, knew the guy who developed it, and saw him give a presentation about it.
That's cool... so I guess this works something along the ways of "calculate the speed via GPS before entering the tunnel, and then try to update this speed using the data from the accelerometer while in the tunnel"? Because as long a the car is moving at constant speed in a straight line, the accelerometer shouldn't register anything...
But tunnels that go up or downhill (or a mixture) would confuse the accelerometer.. well I guess they'll have the road gradient data.
I drove in tunnel where the asphalt had undulations today, I'd like to see them try to figure that out!
Well it registers gravity, so you can detect i.e. driving off a cliff. ;)
What helps is that tunnels don't usually branch, so once you're in it, your path is usually quite predictable.
TomTom maps also have a statistical model of what speed is expected along each stretch of road by hour and weekday/weekend (not 7 individual days, but 2 kinds of days). But I don't know if it uses that to help estimate your expected speed when dead reckoning, it's actually for route planning.
One of my co-workers came up with the great idea of gamifying driving: maintain a real time speed leader board, showing the top ten speeders along any stretch of road! So on every road in the world you could compete with other TomTom users who drove it. Kind of like checking in with 4Square, but more fun and dangerous! TomTom legal did not approve.
I suggested gamifying and monetizing driving with TomTomagotchi, a virtual pet that gets depressed if you don't drive it around enough, begs you to visit interesting landmarks and sponsored points of interest, like driving through McDonalds to feed it, or through the park to let it take a shit, or driving fast enough to make the leaderboard to entertain it. I'm sure Bandai's lawyers wouldn't approve.
I swapped out the satnav in a 2008 Honda for a modern unit and the car had a “speed pulse” wire. I looked it up and that wire is used for dead reckoning.
A practical issue is that GPS can be spoofed relatively easily. If autonomous driving became a thing, and ubiquitous, with vehicles that prioritized remote over local consistency, then a single GPS spoof could cause some interesting things to happen. This is probably a concern that does drive decisions, at least to a degree. It creates a weird scenario where you kind of need to trust GPS, but you simultaneously also can't treat it as authoritative.
OTOH creating a dumb user experience for a fairly common scenario, to try to preempt a hypothetical scenario is probably not a great idea. A fun problem to think about, though it may be completely unrelated to this issue.
I do hope self-driving software works out a better system, before it becomes common place. Autopilot has been incorporating GPS in aviation for decades, and it's still surprisingly common to have major problems when a loss of GPS occurs.
The Phenom 300 jet can't fly straight without a valid GPS signal: https://news.ycombinator.com/item?id=12519629
Every swept-wing jet has a tendancy to enter a positive feedback loop of rolling and yawing, called a dutch roll, when flying at altitude, so even when not using autopilot, an active system is needed to fly straight and level. If the Phenom 300 doesn't have a valid GPS signal, that system fails.
If it becomes common place, spoofing is easy to counter. Directionality and parallax of the signal is enough to figure out the true signal, all it requires is an additional antenna.
This won't prevent jamming, that requires a different mechanism, but spoofing should be prevented.
> On a vaguely related note, driving 3000 kilometers through Europe in an electric car was surprisingly nice.
Having done a number of multiple-thousand km trips in Europe in an EV (not a Tesla, nobody buys those anymore) — it's amusing how non-EV muggles think this is somehow an ordeal. It's just fine! There are drawbacks: you do have to use your brain and plan ahead more than you do when burning dinosaurs. But I found that the 20-30 minute stops every 2h really improve how I feel after a day or two of driving.
Agreed about prices: there is gouging going on with some crazy margins. When charging at home, an EV is 2-4x less expensive per km than a gasoline-powered car, but when fast-charging on a road trip the cost of energy is nearly the same.
> But I found that the 20-30 minute stops every 2h really improve how I feel after a day or two of driving.
I honestly started considering this a feature. I am a huge believer in "productive friction" - where some things are intentionally made annoying or hard so that humans avoid them - and this is a really good example.
Stray anywhere off the main roads and suddenly your 'just fine' turns back into an ordeal.
And God forbid you come across inclines!
What is a non EV-muggle?
Muggles, in Harry Potter books, are non-magic people, who do not have magic, do not understand it, have a lot of misconceptions about it, and fear it. :-)
> draws swastikas to emphasize anti-fascism
> breaks windows
> sets cars on fires
>> nobody buys those anymore
surprised pikachu
Back in the days of MapQuest there was a (usually) very good site called mapsonus.com, but it evidently had one of the ferries that crossed Boston Harbor in its map as a zero distance link.
Since it was offline, the bug was obvious although a bit frustrating - you had to put in multiple waypoints to make it forget its urge to send you on the ferry to Hull when you were trying to get to parts of the South Shore.
I suspect that my Tesla adjusts its location based on dead reckoning after losing GPS lock except that it assumes that I'm driving forwards. I.e. If I reverse out of my garage, then the map ends up in the wrong place and now I'm driving parallel to the road!
As you're mentioning a RO/RO ferry, recently, and Europe... are you sure you weren't in a GPS-denied environment, where the car (correctly) detected that GPS was jammed or spoofed and ignored it?
It was further west than you typically see significant GPS jamming, and GPS on other devices was fine.
Possibly it was using WPS keyed to the ferry's WiFi and didn't consider the possibility that the ferry itself could move out of where it was registered (ie, the port)?
I drove away from the ferry and passed lots of WiFi APs on the way, presumably it should have figured out the new location pretty quick with WPS.
Perhaps the car is programmed to ignore all external signals for a while if it detects significant disagreement for a prolonged time, as might have happened if it had access to both WPS and GPS during the ferry ride. In such cases it would be safe to assume that something is being spoofed, and fall back to INS.
Civilian GPS (as in, the DoD’s Navstar) alone isn’t accurate enough to actually place you on a specific road. To compensate, auto navigation systems will snap you to the nearest road parallel to your current heading. Tesla likely didn’t consider the edge case of ferries and other off road situations in their mapping software and you hit some corner case bug.
This used to be true, but the DoD turned off "selective availability" (the intentional degrading of the civilian signal) back in 2000, and the current generation of satellites do not have the capability (https://www.gps.gov/selective-availability). What they do have though is a separate, encrypted, military broadcast that can be used for those purposes (I think the plan in those situations is to turn off civilian GPS entirely - but I think that there's no reason for that, now, due to the other navigation systems like GLONASS).
Even without selective availability gps is only accurate to within about 30’ in normal urban conditions which is more than enough to punt you over to a side street without heuristics on top.
One hypothesis I can offer is that your car could not, for whatever reason, use assisted gps to download the almanach which relies on mobile networks. Gps devices that download the almanac via gps itself can take up to twelve hours (in higher latitudes i think)!
It doesn't just become invalid; almanac is good enough to use for satnav for over a day.
My farming GPS does this every time I ship it with my vehicle to a new continent.
I always figured it has some code to get a quick location, and it assumes that location is very close to the last time it got a sat lock.
I just ignore it for the first day, then it comes good.
I wonder if it's using a compass and odometry (distance) with dead reckoning. A strange choice when GPS is available, but it would account for the map moving in the car's direction and it not changing locations when it moved without rolling (ferry).
Almost certainly. GPS is not only easily jammed, but easily spoofed. If the car believed GPS instead of its own eyes, so to speak, then there’s significant potential that you’d see glitches more often. It could also be something of a safety risk when using its self-driving capabilities.
Makes me wonder why there isn't a UI feature within easy reach to let the user drag a pin on a map and tap "I know I'm here right now"... and if that agrees with where GPS also indicates, let's it reset its notion of "I must be getting spoofed right now" thoughts in addition to calibrating other notions of current location.
In addition to sibling's comments about jamming and self driving safety, there are many driving situations where there is no or poor GPS reception: tunnels, double deck bridges, double deck freeways, underpasses, urban canyons, actual canyons, etc. Also regional problems. The GPS constellation is in a 55° inclination, so if you are north of ~55N, or south of ~55S, you need a clear view of the southern/northern sky, respectfully, for reception, since there will be no overhead satellites.
Looks like others have reported similar issues. Entering a navigation route may help?
https://teslamotorsclub.com/tmc/threads/map-location-and-rou...
> Entering a navigation route may help?
Didn't work for me.
I remember cars in the early 2000's doing this. Haven't seen that behavior in years.
Context is confusing because we arrive in the middle of a story arc, at a point where an unrelated tech snafu happens.
The story arc is about a lost airtag that is living it's secret life in Mexico.
The link is for a post where Apple decides the distance to it's location in Mexico is greater than the circumference of the Earth.
GPS has an altitude component so maybe it thinks either the AirTag or the tracking phone is really high up?
Nah, the altitude component is less than a rounding error at the scales involved.
It's clearly in a vaguely geostationary orbit above Guatemala City.
Tangentially, why won't computerized maps - e.g., Apple Maps, Google, etc. - show a scale? Generally they'll show one as you pinch/zoom, but it disappears when you release your fingers.
Sometimes I just want to eyeball distances, and not plug in addresses and request routes for everything.
I know not everyone always wants it, but a scale is a fundamental feature of mapping! Scale almost defines mapping.
Edit: One reason I ask is because I suspect some technical limitation.
I thought it'd be cool if the scale were shown by some channel, like coloring roads (pink at neighborhood scale, blue, green as you zoom out) so you could intuit the scale at a glance.
With map simplification and symbolic markers (roads are the same thickness at multiple scales) it can be really hard to figure out distances. I was once going to a less populated area, based on my local intuition I thought the distance between two locations was a maybe 30m walk max if I missed the bus, but it turned out it was a 3h walk.
It’s purely a UI thing, the same (misguided) reason scrollbars disappear.
Directions suggest an average speed over 500 mph. Not bad for driving.
It’s the speed of a passenger flight, but I wouldn’t want to spend 57 hours aboard.
Actual distance about 3.2k miles plus equator length of 25k miles plus what else?
Altitude
I made a comment earlier that was rightly flagged for its tone, and I would like to restate the technical point more constructively.
The post author, Dan Piponi, clearly knows about fractals, but his post raises the question of whether asking Fermi questions in interviews is actually effective. I am skeptical that such questions would have prevented this type of bug.
I suspect the issue stems from small measurement imprecisions accruing over long distances, which is—in my view—tied to the fractal nature of roads traversing natural landscapes.
However, as others have pointed out, it may also be tied to road closures: if closed segments are set to a higher length internally (to discourage routing), these values might be getting summed up blindly over longer distances.
None of these issues would have been prevented by being good at estimating quantities alone.
Apologies again for the unconstructive tone of my previous comment.
A pure spirit is required to admit your own mistake. Don’t be let down by an error, never lose the opportunity to fix it. May this be of example to everyone to keep improving this already wonderful but not perfect community.
Oh wow, a bug
In Apple Maps? Unpossible!
Except this one is not on the windshield.
I’ve had that bug a few times. I think it’s related to some roads being closed and/ or under reconstruction. I’ve seen this happen multiple times on the same route, and it always fixed itself after I passed the construction site.
So it might be a hack to get it to take another way -- rather than invent some way of marking a road section as being closed, mark it as being 1000 miles long?
Maybe they are running into https://en.wikipedia.org/wiki/Coastline_paradox
It's unlikely that would cause a 10x increase, especially since the directions are presumably aligned to roads of non-vanishing length.
context?
I went back to their posts in November for this
> One of my AirTags is inexplicably 1600 miles away in Texas. It's one of my floating ones that I throw into bags when traveling as needed.
> Maybe it dropped out of my bag only to be found by someone who thought it'd be fun to confuse the owner. Or maybe it became e-waste to be dumped in another country.
The distance is more than the circumference of the Earth. If you wrapped a rope around the planet at the equator, the length would be around 25k miles.
Some roads aren’t perfectly straight (not that this seems like it could explain what happened in this particular case).
That's fair, but even the commonly cited longest route [0] you could theoretically walk without intentional detours, Cape Town, South Africa to Magadan, Russia, is approximately 14k miles.
[0] https://www.reddit.com/r/MapPorn/comments/a2mcjq/21212_km_fr...
Sure. However, if the road around the planet goes to Everest and back, the total length of travel will exceed the circumference of the planet.
Seems like the author of the linked post has a lost airtag located in the abyss.
It’s sitting next to Apple’s values.
Looks like a bug that I hope someone will have a fun time fixing.
You wouldn't imagine ...
I have seen API calls you people wouldn’t believe.
Requests hanging off the edge of the load balancer, Ethernet tubes glittering in the dark.
Latency logs reporting some API calls that took longer than the age of the universe.
Their means and percentiles burning on the shoulders of weekly reports.
Plot points dying at the edge of y axis
... like tears in the rain.
Time to reboot
Indeed and Voigt-Kampf the signed from the unsigned, dynamic types from static.
Fixing bugs. At Apple. OK.
I think the developers didn’t account for lost AirTags many hundreds of miles away. And that long calculation was not the best.
As one of the commenters pointed out, altitude.
A geostationary orbit is ~26,000 miles. Dollars to donuts, that's where it is.
If you account for the satellite being further away because it would be above the point the distance works out okay - except that geostationary satellites go around the equator and that is a thousand miles away from that.
Loved the comment about the fractal shaped path.
Maps has gone backwards on CarPlay, too. Hysteresis is completely broken - I stop at a traffic light and the map will jump back and forth between two resolutions, often once a second, which is extremely distracting.
I also love that Find My says my partner was "last seen" at home "8,912 days ago".
Apple just doesn't give as much of a shit any more.
Sidenote, I love spotting random binary numbers out on the wild
48 137 km.
1.2 times the circumference of the Earth. Is space compressed between SF and Guatemala City somehow?
The most annoying thing about iPhone Maps for me is the inaccuracy of the direction indicator. I've googled and it doesn't seem to be a universal complaint even though I've experienced this on multiple devices over the years even after following instructions to re-calibrate multiple times. Maybe I've just been unlucky.
It intensely frustrating to use maps for direction finding while walking or cycling when the app is telling you are facing one direction when in fact you are facing another.
Settings - privacy - location services - system services - compass calibration. Make sure it’s enabled. In a bout of paranoia I disabled location for everything I didn’t recognize as necessary and then it took me many months to find out why compass cone behaves funny in mapping apps.
On my past iPhones, the compass always got screwed up over time somehow. Sometimes recalibrating fixed it, but only for a minute.
Yep - exactly what I’ve experienced. Calibrate the compass and at least it’s within a right angle of being correct. But the problem returns.
Was it serviced? In some models they used to have a non-ferrous screw put next to the compass, if a tech puts the wrong one in it will not calibrate.
That's a phone compass problem no? Perhaps the specific way you're holding the phone is confusing for the algorithm?
You're holding it wrong part 2?
It is easily 29,905 road miles away.
If you put all of your blood vessels end to end they would go to the moon and back.
The flight distance is 2,520 miles, Google puts road distance at 3,179 mi = 1.26x, 29,905 mi is 11.87x. Road miles are not even close to accounting for it, it’s just a bug.
> If you put all of your blood vessels end to end they would go to the moon and back.
The moon orbits too quickly to make this practical
Being a little bit clever can lead you to make some pretty bad mistakes.
Yes, the distance according to roads can be different from the distance as the crow flies. No, it cannot realistically be 10x the distance when the crow's distance is 2500 miles.
But what if you count the distance of going in and out of each tiny crack on the road surface?
Look up "fractal dimensions".
I know :)
I question your use of the word “easily”.
You would have to take an implausible number of wrong turns to have a chance of making it anywhere near that long a drive. For an example of a shorter but still entirely unreasonable path: Head straight north all the way to the pole, continue south to the pole, continue north to the latitude of the destination, then head due east until arrival.