Although I do not like users dependingn on GPS instrctions the following link is an example of a specific location that is causing trouble. My own GPS has a fault that tells the user to turn right maening make an immediate right after crossing the RR. My GPS should say cross the RR then turn right. My GPS does this even though the RR tracks are shown on the display. So instead of saying turn left cross RR tracks and then turn right. It jjust says turn left then turn right. MY location is subject to dense fog for about 20 days a year.
This is not so much a GPS problem as it is a GPS UNIT problem. It’s the software that has the glitch, not the satellite positioning equipment (or even the functionality derived from sequential fixes).
Having said that, yes, there are areas where pure-satellite GPS does not have adequate resolution to give unambiguous data to the software in the unit. That was the reason to investigate NDGPS (which adds fixed beacons on the ground to the satellite constellation) and HA-NDGPS (which uses differential beacons and additional calibration to give the high accuracy). Once your fix resolves reliably down in the centimeter or millimeter range, the input to mapping software can be more reliable too.
But if the maps are wrong, or poorly updated – well, remember the poor bastid who relied on his BMW navi system in Poland, and drove straight into the river at the ferry slip, going around 70mph in (I believe) fog, where the system told him faithfully to expect a bridge…
In my opinion, a big, big additional factor is the lousy UI in many of these GPS boxes. All you get is a limited view ahead, often with no ability to scroll or zoom handily while also driving, and stupid voice prompts like ‘turn left’ rather than more detailed prompting about what you’re supposed to be turning left onto.
There was, a few years ago, an interesting idea being tried, which rendered the 3D view of the road (it would be done with Google Street View data nowadays) with the chosen route depicted as an OVERHEAD line, which wouldn’t obscure the ground-level detail. I found this remarkably easy to follow, and it would have worked nicely in synthetic vision or data fusion too, which is probably the next sensible step for car-mounted nav systems.
Overmod is right. The GPS units only determine latitude, longitude and elevation from external input (and only within the accuracy allowed). The mapping part of it (and subsequently the directions) is from the map in it’s memory and has to be upgraded from time to time (if the unit is capable) to keep it current.
Reminds me of when my parents asked me “if all your friends jumped off a cliff would you do it too?”[:O]
If your GPS unit told you to drive over a cliff, would you do it? [(-D]
It’s the GIS (Geographic Information System) at fault, not the GPS (Geographic Positioning System)…followed by operator total lack of common sense issue.
Surveyor comment on GIS = Get It Surveyed
Railroader comment on GIS = Garbage-In Standard
The precision of autonomous GPS is often squirrely. Programmers, most engineers and most of the public are putting their faith in a black box that is hardly sub-meter accurate (more like half a football field in reality). They have no idea what reliability that geographic coordinate given them really has…and then get around buildings, bridges and those pesky trees[^o)]
Between the i-zombies and the geographically challenged, it’s gonna be a tough road ahead.
I run with a Garmin wristwatch that uses GPS technology to tell me how far I have run from my start point, but only in linear terms. It seems to me that its standard error of measurement is somewhere between 3-5 meters as the watch stops shortly after I pause, and then displays “resume” after I have run another 4-5 m upon resuming my run.
Last week my wife’s cell phone’s navifation app told us to turn left onto a street where the obvious and requisite turn was to the right.
I don’t rely on it at all, but give it half an ear when she insists on using it to run checks as to its accuracy. So far, about 99.9%. It seems drivers, those ultimately responsible for the safe conduct of their vehicle and its passengers, are sometimes lulled into complacency and reliance. It’s that one instruction in 1000 that is wrong that’ll getcha. Witness the Canadian elderly couple that ended up a logging road in some mountains in the USA about two years ago now. Didn’t go so well after they got stuck in the snow.
What MC says is pretty much spot on. Witness an iphone that gave directions (since corrected) to the Fairbanks, AK airport that had people crossing an active runway. That could have nasty results.
People take these GPS devices far too seriously. They need to get their head out of a dark area and look out the window once in a while. Common sense (which seems to be severely lacking these days) would dictate you cross the tracks rather than turn onto them.
I have GPS that runs on my laptop. It’s a good guide but I don’t take everything it says as gospel.
I’ve heard tell that some drivers will drive “IFR,” relying completely on their GPS to keep them on the road under conditions of extremely limited visibility. Kinda scary to think that there’s a fully loaded semi ripping down the highway at speed, counting on his GPS because he can’t see beyond the end of his hood in the fog…
I have GPS based speedometer apps in my phone and tablet. When I use them in the truck they are actually displaying an average, not the “moment” speed, witness the relatively gradual “slowing down” that occurs after I’ve come to a complete stop.
I used my phone GPS once to plot the scene of an accident for a fire report. When I verified the result on a mapping program, it had the site a fair distance off the road, and I was sitting on the shoulder when I shot it.
Another problem that may occur is insufficient satellites available, because the GPS isn’t placed where it can pick up as many as possible. Most GPS’s will work on three satellites, but eight or nine gives much better results, accuracy-wise.
Some of our engines are equipped with NY Air Brake’s Leader system. The in-cab display has a map with the train’s location updated by GPS. Our version of Leader only shows the location of crossings and bridges/culverts and curves. It doesn’t display other tracks or block signals although NYAB’s brochure (pdf) shows those features available.
Usually when running at or near track speed, when the display shows the engine starting over a crossing or bridge, in the real world the crossing or bridge is about 2 or 3 cars back.
When I lived at 4778 West West Point Drive, I had at least two people call me asking how to get to my house when they were coming to see me. When they reached the intersection of 4800 West and my street, their devices told them to turn in the wrong direction, and sent them farther out.
Last spring, while visiting my college, my daughter and I were going to our hotel, and I, not following the map closely, told her to turn right before we should. Some time after continuing on that road too long, she looked at her cell phone and saw where we were, and how to get to where we wanted to go. On the same trip, my map(from Streets and Trips) indicated that we should turn right to get to another hotel–and the hotel was visible on the left.
In the town where I grew up, there is an alley which you will go up if you do not make a 90 degree turn on US 521–and Streets and Trips will direct you to take the alley (it’s the alley that a Greyhound driver started up one evening after my brother pruned a privet hedge drastically, about sixty-five years ago).
Streets and Trips also shows my house as being east of the street that marks the beginning of the 600’s (my house is at 584).
Don’t confuse consumer GPS devices with what more sophisticated units can do. Example: the US military, although they are developing alternatives to get around jamming.
One problem is that most people have no clue of how GPS works, i.e. the position is determined by the intersection of hyperboloids determined by the difference in noted in timing signals from the satellites. There’s also issue of these signals being affected by the ionosphere and multi-path. To top it off, getting a good fix requires having enough birds in view with enough directional orthogonality (i.e. no buildings, trees or terrain blocking significant portions of the sky) to avoid having to solve an ill conditioned set of linear equations to derive the positional fix.
As for GIS - the rangers at Death Valley called several of the GPS receivers mfrs to come to the site and see the death traps of rails that were marked as passable roads on the device maps.
One of the problems I encounter with mapping programs (Earth, Acme Mapper, etc) is their inability to deal with variations in a road name. I live on a road numbered by the county, it is usually variously represented by people as CR999, Co Rt 999, Co Rte 999, Co Rd 999, County Route 999, and County Road 999 (plus probably one or two more, not to mention an older name).
Humans can easily parse that out on a paper map. But unless I spell it Co Rte (with the E) when searching such programs, I’ll end up with a really wild response. I’m sure the same is true of GPS’s.
Another problem can come from the mailing address. I live in one township, and the village of the same name does rural delivery for about half the town. the other half is split between two neighboring post offices, and the post office here in the hamlet doesn’t do rural delivery at all.
The only difference between the military GPS receivers and the commercial variety is the accuracy and stability of the internal clock. Military systems will have less variation in the indicated lat/lon location.
Most commercial systems are so unstable that if you just sit still for very long, you will find that it will show that you are not sitting still, but traveling around the area, at speeds up to 30 MPH, in a range of ± 150 feet (or maybe a bit more), depending on the particular device you have, the temperature and how much that temperature changes, and variations in the weather between you and the (ever moving) satellites.
As for following a map that your route is overlaid upon, they also will have some (possibly gross) errors in the geographic location of the streets/roads and landmarks (military units are no better here!).
I have found many places where the map shows roads intersecting (and as such, the “Plan a route” feature indicates one should turn there) but the roads are physically separated by an overpass and there are no entrance/exit ramps between the two.
I have also attempted to create a route to follow that would take me on a road I know quite well, but it would not allow it. Closer examination revealed that when the road was digitized it was broken in the middle and the two “ends” are separated by about 10-feet and the “Plan a route” feature will not “jump the gap” to allow the route to take that path.
And don’t forget the tourists in Florida that a GPS enabled rental car directed to drive down a boat launching ramp into the Miami River… They said they accepted the instruction because in the Midwest, where they were from, it is common for small streams to be crossed on what are called “low water bridges”… small pipes laid parallel to the flow of the water and covered with concrete; during normal times the water flows through the pipes, but after a storm th
I find the Garmin GPS-18 that runs on my laptop to be of good accuracy. I never plan a route on it. In Michigan there are too many construction zones to navigate around, and that’s where it’s truly handy. It even tells me whether the escape route is paved. I have, though, found some errors in things like road names.
That said, I use it purely for reference. I drive with my head up so I can see where I’m going.
I don’t know about the Garmin systems, but some will automatically reposition the location on the map (or the map under the position indicator) so that it appears you are “ON” the primary road nearest the GPS reported location. This is good most of the time, and makes it appear to be a very accurate system.
One of my old systems often shows me as weaving from one farm field on the left to the ditch on the right, when I am driving quite straight on a straight road.
This can present a problem if there are parallel roadways near where GPS has determined you are… i.e.: you might actually be on a “service road” adjacent to the primary highway, but GPS has you in the ditch on the other side of the primary highway. So it will ‘adjust’ the indicated position to be on the highway since it might assume that is where you are supposed to be.
I use an older DeLorme Street Atlas and I think it is FUNNY when the mapped road that it thinks I should be on deviates from where the GPS is telling it where I am. The first time this happened when I had the audible instruction feature turned on, I was having trouble understanding what it was saying and it sure seemed to be issuing some sort of mild cursing in the warning… it kept yelling:
“AW FRUIT! Recalculating route!”
That was the strangest expletive I had ever heard. I glanced at the display and it showed that I was out in the middle of a farm field. The road actually had a wide “S” curve in it around a pond, but the map showed the road was straight and no pond was indicated.
The system hurled that epithet dozens of times before I realized it was actually saying, “Off Route!”
The previous voice system was even harder to understand. When I had it plot the first route after I got it, it told me to:
That’s why I don’t pre-program routes. Those voices drive me nuts.
I’ve had the ‘across the field’ experience but it was because the database was outdated. I can set mine to ‘lock on road’ but don’t usually need to do so.
We have a crossing here that over the years has become so humped by track work that trucks over 3 axles are prohibited. Due to cross streets and existing buildings its not feasible to raise the approaches. We have posted numerous signs on the approaches, and we still have trucks getting hung up there about every 3-4 months. One was hit about two years ago, though the train had enough warning that it was down to about 10 mph when it hit, from about 40. Its on a tangent. Every time it has been, " the GPS sent me this way". Our police have a good relationship with the CSX police here and there drivers get slammed pretty with local and CSX tickets and fines.