Typically those are map data issues rather than routing algorithm issues. Just in the last few years modern crowdsourcing techniques are starting to do a lot to alleviate those problems, but there still is a long way to go. The world is a big place!
I found that when I was in New Jersey several years ago that GPS units have trouble distinguishing roads that overlap (overpasses & underpasses,etc). This was also the case in the Philadelphia metro area.
As far as the recent couple that depended on their GPS unit and were lost, I have some serious questions about that. Even if they were depending on their GPS unit it should have become painfully obvious to them shortly after they left a main highway that they didn’t have the correct vehicle to traverse the landscape in which they found themselves.
Frankly I suspect that they had attempted to perhaps can’t for the night to save money and then found it impossible to move when they tried to in the morning. While that may make them look foolish, her (the wife’s) current explanation is so implausible that continuing to use it makes her look more foolish.
Are you sure you had it programmed for the international airport rather then the downtown airport? There are both in Edmonton.
I make maps of, among other places, rural New Mexico. There are still huge areas of the USA with only the most rudimentary of maps—much less trustworthy geodata.
It really is implausible - I’m just not sure how people get themselves into a situation that bad and stupid.
We were talking about this yesterday, and I posited that this was an elaborate plan of the husband’s to leave his wife. 
There’s an iPhone app called Waze that is all based on crowdsourcing. Seems like the best way to do things, to take the data from actual use and adjust your information from that.
Not exactly a horror story, but…
I was driving my 15 YO grandson from his house in Redmond, WA to some place in the next town north that was programmed on my son’s GPS. I knew the area around my son’s house fairly well. The first part is to go down 95th St and cross 166th. Well, 166th is fairly heavily trafricked and what I decided to do (having seen my son do the same) was turn right at 166th and then left at the light at 104th. The GPS reacted to my turning right at 166th by recalculating and directing me to turn right at 104th. This was total nonsense and I ignored it. It worked correctly after that, but I have since wondered where it would have sent me, since that right turn made no sense at all.
The strangest thing mine has done is to tell me to get on the Alaska Marine Highway when I was wandering around Bellingham, WA. As I don’t drive an amphibious vehicle, I’ve ignored that instruction.
But 95% of the time, it gives reasonable directions. And sometimes, if I’ve got time and it doesn’t look like it will be dangerous, it’s fun to follow it for the other 5%, just to see what the hell the GPS is doing.
I’ve never experienced a complete disaster with my Android Google Maps GPS but I’ve had some inconveniences:
[ol]
[li]When I drove to Montreal, Canada from Vermont I had hoped my US only data plan would be okay because once the route is calculated you don’t need to maintain a data connection, it caches the whole thing. This appeared to be true, right up until my phone rebooted itself five minutes into Canada! Frustrating, but luckily it was a well marked route into Montreal and where I wanted to be specifically.[/li]
I’ve used this feature with great success in rural Alaska: navigate somewhere from Anchorage and still have great instructions two hours out of the city. Of course I would never go anywhere dangerously far from help with this strategy, but it was a convenience.
[li]The Google algorithm sometimes will try to be smart, and if it knows the exact location of the building you are trying to get to will navigate to the road closest to it, which is not always the technical street address. This is not always correct, since sometimes it has told me I’ve arrived when I’m on an interstate or onramp / offramp! Of course there is no easy way to fix this, because it’ll try get you back on the interstate again![/li][/ol]
Not sure if this qualifies as a horror story or a minor inconvenience. Back when **geneb **and I were getting married, my family and friends were flying/driving in from across the country. Their GPSs misdirected them to an address across town, so something like 7 people ended up being half an hour late. XD
Maps and GPSes think the road I live on doesn’t dead end, and it doesn’t. But to drive all the way down it to meet the next road you have to go on a gravel section with big rocks (like basketball sized) for 1/4 mile or so. You can’t fly down it but if you take your time no harm will befall your vehicle.
How about this one?
Charleston?
Yeah, going from MIT to Harvard Square by way of South Carolina is not such a good idea. 
[/QUOTE]
That’s just silly. He obviously means Charleston, WV.
I have no real horror stories, but I always back up the directions with a search on google maps or consult a paper map.
A friend of mine and I went to NC from Philly for a little trip. Her GPS had us taking 95 straight through DC. I know this is not the most desirable route, but it was a Saturday afternoon, so we didn’t encounter a whole lot of traffic.
My GPS doesn’t know about the iWay in Providence (we got the cheapest one) so we don’t turn it on till we get over the bridge or it’ll freeze up.
I-95 doesn’t go straight through DC, it goes around it to the east, as part of the Capital Beltway, crossing the Potomac River with the Woodrow Wilson Bridge. US 1 does go straight through the city though.
Technically, there was nothing wrong with my GPS unit or the map installed. The issue on my road trip around Ireland was that a given road’s official speed limit was used to calculate the fastest route to a destination.
What was labeled a 60kph road was a single-lane backroad lined with hedges. Next to nearly causing an accident the day before, this was the most scared I’ve ever been driving. My wife was no better from riding half the day almost in a ditch. I couldn’t even really go back, by the time I really realized how far into boon-fuck nowhere we had gotten, it was equal distances in every direction to civilization.
It wouldn’t have been too bad if we could look at the scenery, but we could only catch glimpses in breaks in the hedges.
It took over six hours to reach Beleek from Coleraine, that should only take three hours or less, not counting stops. We decided to plot longer distances on a traditional map, sticking to M- and N-and maybe A-level thoroughfares, and R- and B-level only when closer to a place of interest. (I’m not sure the road we were on had a name or number.)
We call them Satnavs, but I had one act like a total penis a couple of years ago.
I was in the north of Snowdonia in Wales, an aptly-named mountainous region, trying to get back down south to where I live in England. There’s a major freeway running through the northern part of the mountains that would connect me with the English freeway system, and I was on said freeway.
I missed one exit. I thought the unit was turning me around, as my Garmin used to, so I followed its directions. Instead it sent me off into a one-car-width farm track, going up the side of a mountain, in deep snow. By the time I realized how stupid it was being, I was too far into the mountains to turn around. If I’d have met something coming the other way I’d have been hosed.
To make matters worse, I had planned to get gas and water at the next service station on the freeway - but there was nothing in the mountains. The adventure continued for another two hours, over rickety medieval bridges, through farmyards, over mountain passes on tiny slippery tracks next to rivers. I was thirsty as hell and eking the damn car along on vapor, no cell signal anywhere.
Finally found a gas station in the middle of nowhere, filled up, had a drink, waited until I stopped shaking - and when I got home after what should have been a 3.5 hour trip, which actually took 8 hours - threw the unit in the trash.
French food and culture yes, French technology, never again.
I hadn’t been reading this thread nearly as closely as I should have been since I posted.
All I can plead is that I was having some major heat-related insomnia that night, and it killed my geography. :smack:
Haven’t suffered a GPS incident myself—don’t own one—but for electronic maps like Google Maps or Mapquest, the story of the ordeal of James Kim and his family scared the hell out of me at the time. Despite the wiki version of events, I had thought from following the story at the time, that Kim used an electronic map (IIRC, Google Maps, but I might be wrong.) to plot their route across SW Oregon, rather than the highway map mentioned in the wiki. Of course, the electronic map’s route didn’t send Kim off the Forest Service road through an open gate (via vandalism by some of the locals) and down a logging road to doom. But when I typed in his route in Google Maps, the route sure looked a hell of a lot bigger and busier on the map than later news pictures of it did.
The map is not the territory.