The question is inspired by an experience I had a few weeks ago. A few weeks ago my wife and I took a somewhat harrowing drive at night. She was driving on a two lane highway which I have driven many times, but this particular night there was some very thick fog and extremely limited visibility. Being familiar with the road I know that there are only a few curves. None the less, the whole drive I was looking at my phone to let her know when we should slow down and prepare for an upcoming curve. We did arrive safely, but the experience got me wondering about the extreme case.
Let’s say I’m driving a car with an opaque windshield. For the sake of safety let’s say there are no other vehicles on the road, no pedestrians, and no sudden drop offs or other such hazards on the side of the road. A passenger is zoomed in on Google maps or Apple maps as close as possible and is calling out instructions to me as I drive. Do you all think it would be possible to drive a few miles using only the GPS to navigate? How slowly would I have to be going if it is at all possible? Yes, it’s a silly question, but I do wonder if anything like this has ever been attempted in a closed off area
This. Even with WAAS, it’s only accurate to about 3 feet on a good day.
DGPS systems can get the accuracy down to just a few inches, provided you’re not too far from a reference station (GPS errors vary with position, so if you’re far from the reference station, your GPS error may be different from the correction provided by the reference station). But even a few inches can be problematic in driving.
Success also depends on accurate surveying of the road, including lanes and shoulders, so that you can stay in the correct lane at any given moment. Google Maps knows that you need to be in certain lanes at certain times (“use the left two lanes to turn left on Main Street…”), but I doubt they actually know which lane you’re currently in, and I doubt their map database indicates the centerline of the road with the kind of accuracy you would need to navigate in the blind.
No navigation system I know of includes detailed and accurate knowledge of traffic controls. Unless your hypothetical is also stipulating "no stop signs, no traffic lights, no variable traffic flow roads (like street lanes that change direction based on time of day)… no, nav systems won’t be able to tell you everything.
And as pointed out, satnav accuracy isn’t inches-precise, so expect to run over curbs, drive on shoulders, etc.
I’m reminded of an episode of Speed Racer (“The Most Dangerous Race, Part 3”), in which Speed was temporarily blinded. Racer X (who was, in fact, Speed’s disguised brother) faked an injury, claiming that he was unable to use his legs, then teamed up with Speed to race, with Racer X calling out directions (“Fifteen degrees to the right!”).
I suppose that it might be possible with GPS, but moving very, very slowly, and probably only on a highway, where you wouldn’t have to worry about traffic signals, narrow lanes, etc. Certainly not at race speeds.
When you drive normally, you look far away (maybe 100 m ahead) and steer towards that far-away point. You’re always making small corrections along the way, half-consciously. If driving blind, of course, you couldn’t aim for anything. So you’d end up either swerving or driving straight into the ditch.
An ordinary GPS unit / satnav / phone doesn’t know the car’s exact bearing. So there’s no feedback as to whether that last 3-degree correction to the left should have been only 2 degrees. (Well, there is feedback, but too late!)
If you had rumble strips along both the edges of the roadway, it would help. But I suspect you’d stand a good chance of getting mixed up between left vibration and right vibration, and ending up in the ditch anyway.
The placement of the icon representing your car on the line representing the road, on screen, typically uses ‘snapping’ - that is, it will generally assume you’re driving on a road, rather than driving on a parallel course to the road, but ten feet off the side, in the long grass.
This effect is most noticeable when the road has a long off-ramp that runs parallel to the main carriageway for a distance after splitting off - if the satnav tells you to take that exit, but you don’t, you sometime see it assume that you have taken the off-ramp, until the roads diverge sufficiently and the device has an ‘oh shit’ moment and corrects its idea of where you actually are.
This alone makes them pretty useful for blind navigation.
How do you stay in the lane? So, no drop-offs off the side of the road but the road isn’t absurdly wide. How do you know to precisely turn when entering a curve, etc.?
And the reality of GPS going wonky makes it all that much more ridiculous.
Could you use GPS? No, not on its own, for the reasons stated above.
You shouldn’t even have been using it in the way you did. If your wife couldn’t see far enough ahead to be able to slow down for curves at the speed you were going then she couldn’t see far enough to stop for an obstruction on the road (such as a car accident or even just a car driving slowly.) If it’s foggy like that, you just have to slow right down until your speed is appropriate for the visibility.
A self driving car would be able to handle fog better, depending on the limitations of its vision systems (radar etc).
It is possible but not safe. You were using one of the worst tools for the job. My windshield mounted Garmin GPS unit is much better than using a phone because you can still see whatever you can of the road. A true HUD (Heads UP Display) like they use on fighter jets and a few cars would be much better. Still, it depends on how accurately the area is mapped because they aren’t all the same. You generally wouldn’t have a problem driving on an interstate highway that way as long as there were no other cars but side streets can be inaccurate enough to result in either a comedy or tragedy.
I have driven in completely blind conditions due to blizzards and violent rainstorms without a GPS or anything else and even that is possible if you go slowly enough, We are talking 5 - 10 mph. You just have to pay hyper-attention to changes in the road surface through feel and any glimpses you can get from the sides and back.
Self-driving cars are already on the horizon but that is mainly in densely populated cities. Common consumer GPS units do not have the resolution to safely navigate less well mapped streets without supplemental aids. It is up to you as a driver to figure out how to figure out how to make it work with the information at hand and pray there isn’t a kid lying in the street in front of you.
Possible yes, but i need access to military or govt or nasa GPS not public, the updates and resolution are too low.
I can pilot a boat down the ohio river in pitch black and fog via GPS and stay in channel
(yes, i have done it) but that is much wider than a car lane, and its moving much slower, 20 knots tops as opposed to 65 mph.
But given a fast enough update rate and resolution, yes it could be done.
It would take a while to get used to, i would be going snail speed for a while
You would have to have **extremely *good mental math and “feel” for distance.
*
“Turn right onto Baker Street in 500 feet” - can you mentally calculate how far 500 feet is, with your opaque windshield, when your car is going 35 mph? Probably about 99% of people couldn’t do that. Not to mention that, by the time GPS tells you, there’s already a 1-second lag, so that “500 feet” is more like 430 feet.
