4 ms·

I am surprised that for dead-reckoning of an automobile position, one would not just use a something akin to a "mouse". Why not compute optical flow from a cam

I am surprised that for dead-reckoning of an automobile position, one would not just use a something akin to a "mouse". Why not compute optical flow from a camera on the underside of the car? Surely that would be more sensitive than an IMU?

djmips 4y ago
I think that's a cool idea. But I think the answer is as simple as it would require mounting a camera on the underside of the car. If you are going that route why not just point a camera at the speedometer right? Or integrate into the can-bus of the car and read it right from the onboard computer. I think the presented idea was probably something that was constrained by what you could do on a phone without interfacing externally.
cogman10 4y ago
Cameras get dirty and the underside of a car doesn't tend to stay pristine. In any event, GPS + measuring how fast the axial spins would be able to get some pretty precises measurements. Two things most vehicles already have. The only issue is calibration at the start of movement.
- hotpotamus 4y ago
  Do you mean axle? I had the same thought, but I believe most every car has speed sensors on all 4 wheels for anti-lock breaks and I would imagine a way of telling the steering angle, so there are plenty of ways to get data; I'm sure more than I can think of since I'm just an occasional backyard mechanic, not an engineer.
  - cogman10 4y ago
    Do you mean anti-lock brakes? But yeah, most cars have sensors for all those things.
    - hotpotamus 4y ago
      Yes, I mean brakes.
deleted 4y ago
[deleted]
Someone 4y ago
For optic flow, you also would have to know the height above the road. That varies with vehicle load, tire pressure, speed bumps, etc. It also would have to work on all kinds of road surfaces, day and night, in rain and snow, with different amount of sunlight, and with varying locations of the sun in the sky. ⇒ I don’t think this is as simple as you make it look.
- _kulang 4y ago
  Fuse it with inertial or depth data, and illuminate the surfacE
alphabettsy 4y ago
Factory systems almost always use the vehicle sensors in addition to GNSS, some early systems only had this ability since GPS wasn’t used. Most cars have speed sensors, compass and steering angle sensors, but having that work with a smartphone is another problem. Also there were these things: https://www.thedrive.com/news/34489/car-navigation-systems-before-gps-were-wonders-of-analog-technology https://www.thedrive.com/news/34489/car-navigation-systems-b...

djmips 4y ago

I think that's a cool idea. But I think the answer is as simple as it would require mounting a camera on the underside of the car. If you are going that route why not just point a camera at the speedometer right? Or integrate into the can-bus of the car and read it right from the onboard computer. I think the presented idea was probably something that was constrained by what you could do on a phone without interfacing externally.

cogman10 4y ago

Cameras get dirty and the underside of a car doesn't tend to stay pristine. In any event, GPS + measuring how fast the axial spins would be able to get some pretty precises measurements. Two things most vehicles already have. The only issue is calibration at the start of movement.

hotpotamus 4y ago
Do you mean axle? I had the same thought, but I believe most every car has speed sensors on all 4 wheels for anti-lock breaks and I would imagine a way of telling the steering angle, so there are plenty of ways to get data; I'm sure more than I can think of since I'm just an occasional backyard mechanic, not an engineer.
- cogman10 4y ago
  Do you mean anti-lock brakes? But yeah, most cars have sensors for all those things.
  - hotpotamus 4y ago
    Yes, I mean brakes.

deleted 4y ago

[deleted]

Someone 4y ago

For optic flow, you also would have to know the height above the road. That varies with vehicle load, tire pressure, speed bumps, etc. It also would have to work on all kinds of road surfaces, day and night, in rain and snow, with different amount of sunlight, and with varying locations of the sun in the sky. ⇒ I don’t think this is as simple as you make it look.

_kulang 4y ago
Fuse it with inertial or depth data, and illuminate the surfacE

alphabettsy 4y ago

Factory systems almost always use the vehicle sensors in addition to GNSS, some early systems only had this ability since GPS wasn’t used. Most cars have speed sensors, compass and steering angle sensors, but having that work with a smartphone is another problem. Also there were these things: https://www.thedrive.com/news/34489/car-navigation-systems-before-gps-were-wonders-of-analog-technology https://www.thedrive.com/news/34489/car-navigation-systems-b...