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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.

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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.

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minutes (bad firmware, faulty memory, tunnels, underground parking lots, etc), it will be relying on increasingly outdated info and drift far off its actual location.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.

_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

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.

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)

>(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

For anything other than driving Organic Maps (iOS) or OSMand (Android) are the very best.

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.

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.

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.

GPS jamming for incoming drones?

Yep

> 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.

Well you can also drive off road too.

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?

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