3 ms·

> Rep rate is not so good. 45 ms = 20Hz maximum. If that's their per-sample time, they probably would've dissolved by now after admitting total defeat - 20 Hz

by saulrh 9y ago

> Rep rate is not so good. 45 ms = 20Hz maximum. If that's their per-sample time, they probably would've dissolved by now after admitting total defeat - 20 Hz is totally unusable for navigation. I'd guess that that's something more like maximum latency from real world to computer, either due to deep pipelining or because they communicate data frames rather than a stream of individual samples. Very easy for that kind of thing to fall through when talking to the media.

Judgmentality 9y ago
> 20 Hz is totally unusable for navigation. What? I've seen lots of autonomous robots that operate at 10 Hz, including mission critical systems for the military. Compared to cameras, which might operate as fast as 60 Hz (but are far more likely to operate at 30 Hz or a fraction thereof) I am confused where you're getting these numbers from. Do you have any citations?
- joshvm 9y ago
  20Hz refers to a single point measurement, as this is (to the best of my knowledge) a 1D LIDAR. Every 45 ms you make a single range measurement. You still need to scan the sensor head to image your scene. Though as the parent comment mentions, it may have gotten lost in the noise somewhere. There's no way GM is using this as a 1D sensor on a car.
  - posterboy 9y ago
    the light cone doesn't have to be focused, a single scan can illuminate a big area, it should be enough that the phase is coherent over the area. or so I'd imagine, but on the other hand, a 100ms ping doesn't mean 10*packetsize throughput per second on the internet either.
joshvm 9y ago
A bit more digging suggests it may be per frame: https://www.strobeinc.com/strobe-lidar/ https://www.strobeinc.com/strobe-lidar/ > Number of pixels and field of view is controllable in real time to 'zoom' the resolution. and the IEEE quote is a bit ambiguous (emphasis mine): > An image on Strobe’s website seems to suggest that the lidar will be much smaller too, with a footprint as small as an American quarter. A number of these would be needed to generate the 360-degree coverage provided by the rotating, roof-mounted lidars seen on many experimental self-driving cars today. Needing several implies a fixed field of view, but that could be either 1D or 2D. Given the size of the device (a US quarter apparently) it could be an area imaging device, but that would imply a pretty big improvement in optical technology to get enough signal-to-noise per pixel. I know they claim FMCW requires less sensitive detectors, but there's a limit.
- infogulch 9y ago
  "pixels" and "field of view" along with the comparatively terrible "20 Hz" rate strongly hints to me (a total layman, admittedly) that these are full 2D frames at 20 Hz, not single pixel samples at 20 Hz. The thought that it would take a full 45ms to sample a single pixel sounds absurd, even for research tech in this area when industry standard is pushing 100 kHz. A 2D surface sampling, say, 200x200 = 20k pixels per frame * 20Hz sounds much more reasonable. If it was only 1D, it would be utterly unfit for navigation if you just scatter a few of them around on the vehicle in fixed locations like their marketing suggests. You can't replace a spinning roof-mounted lidar with just a few fixed 1D sensors. The spinning lidar gets something on the order of one sample per degree, right? To even come close to replacing that with fixed 1D sensors you'd need on the order of 360 of them around the vehicle, and their marketing doesn't sound like that they expect you to use anywhere near that many.

by saulrh 9y ago

Judgmentality 9y ago

> 20 Hz is totally unusable for navigation. What? I've seen lots of autonomous robots that operate at 10 Hz, including mission critical systems for the military. Compared to cameras, which might operate as fast as 60 Hz (but are far more likely to operate at 30 Hz or a fraction thereof) I am confused where you're getting these numbers from. Do you have any citations?

joshvm 9y ago
20Hz refers to a single point measurement, as this is (to the best of my knowledge) a 1D LIDAR. Every 45 ms you make a single range measurement. You still need to scan the sensor head to image your scene. Though as the parent comment mentions, it may have gotten lost in the noise somewhere. There's no way GM is using this as a 1D sensor on a car.
- posterboy 9y ago
  the light cone doesn't have to be focused, a single scan can illuminate a big area, it should be enough that the phase is coherent over the area. or so I'd imagine, but on the other hand, a 100ms ping doesn't mean 10*packetsize throughput per second on the internet either.

joshvm 9y ago

A bit more digging suggests it may be per frame: https://www.strobeinc.com/strobe-lidar/ https://www.strobeinc.com/strobe-lidar/ > Number of pixels and field of view is controllable in real time to 'zoom' the resolution. and the IEEE quote is a bit ambiguous (emphasis mine): > An image on Strobe’s website seems to suggest that the lidar will be much smaller too, with a footprint as small as an American quarter. A number of these would be needed to generate the 360-degree coverage provided by the rotating, roof-mounted lidars seen on many experimental self-driving cars today. Needing several implies a fixed field of view, but that could be either 1D or 2D. Given the size of the device (a US quarter apparently) it could be an area imaging device, but that would imply a pretty big improvement in optical technology to get enough signal-to-noise per pixel. I know they claim FMCW requires less sensitive detectors, but there's a limit.

infogulch 9y ago
"pixels" and "field of view" along with the comparatively terrible "20 Hz" rate strongly hints to me (a total layman, admittedly) that these are full 2D frames at 20 Hz, not single pixel samples at 20 Hz. The thought that it would take a full 45ms to sample a single pixel sounds absurd, even for research tech in this area when industry standard is pushing 100 kHz. A 2D surface sampling, say, 200x200 = 20k pixels per frame * 20Hz sounds much more reasonable. If it was only 1D, it would be utterly unfit for navigation if you just scatter a few of them around on the vehicle in fixed locations like their marketing suggests. You can't replace a spinning roof-mounted lidar with just a few fixed 1D sensors. The spinning lidar gets something on the order of one sample per degree, right? To even come close to replacing that with fixed 1D sensors you'd need on the order of 360 of them around the vehicle, and their marketing doesn't sound like that they expect you to use anywhere near that many.