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rightbyte 8 months ago

"Its particular superpower is that it can generate high resolution images of its surroundings much better than radar can."

Is this true tough? Car radars are fixed. I guess a comparable lidar would be fixed too and have n points for n lasers.

A rovolving radar would have continuous resolution around while a lidar samples?

I thought the advantage of lidars were accuracy and being better at measuring heights of objects, where as radars flatten the view.

ender7 8 months ago | parent | next [-]

The issue isn't one of fixed vs rotation, it's that radar can't fundamentally achieve the resolution necessary to distinguish important features in the environment. It's easily fooled by oddly-shaped objects, especially concave features like corners, and so while it's great for answer the question of "am I close to something" it's not reliable for telling you what that something is, especially at longer ranges.

lupusreal 8 months ago | parent | prev | next [-]

Very high tech radars can generate amazing imagery, but they'll never top what lidar can do. Conceptually they're both doing the same sort of thing using EM radiation, but lidar uses a much smaller wavelength which gives it an intrinsic resolution advantage. Particularly at distances and with hardware sized relevant to cars.

xnx 8 months ago | parent | prev [-]

I believe automotive radar has a cone of sensitivity that is read as a single "pixel" worth of data. Even if the radar spun like lidar, the radar cone of sensitivity is thousands of times wider than the lidar beam so you can't make much of a picture with radar.

0_____0 8 months ago | parent [-]

IIRC the data coming out of the Conti radars was preprocessed to give bearing, distance, and size of an object in the FOV of the unit. I don't know if I ever saw the true raw data out of one of them, but I'm curious what it looks like.

rightbyte 8 months ago | parent | next [-]

Ye I have a hard time imaganing how a car radar image looks like.

On boat radars it seems like the radar have really high resolution (can see much further than lidars) but have worse accuracy. I.e. things looks like blobs.

A lidar image at 50+ meters is very sparse.

0_____0 7 months ago | parent | next [-]

If you want more points downrange, you design your scanner to work on a smaller FOV. Some things change - you need an optical design that scans a small area in front of it somehow (faceted mirrors are popular), and at some point you need a laser source of higher quality, possibly moving away from diode lasers and towards things like fiber laser sources. This isn't conjecture BTW, this is what players like Waymo do and is evident from studying the sensor package if you're curious.

jeffreygoesto 8 months ago | parent | prev [-]

Roughly like in this paper https://www.semanticscholar.org/paper/RadarScenes:-A-Real-Wo...

rightbyte 8 months ago | parent [-]

Thanks. Spot on!

itishappy 8 months ago | parent | prev | next [-]

I'd be curious if the design of the Cybertruck affects readings at all. It's got angles straight outta an F-117.

0_____0 8 months ago | parent | next [-]

I reckon it's probably not that bad, there are big surfaces that are almost normal to what would be incoming radio energy. Stealth shapes tend to reflect energy in a completely different direction from the source.

itishappy 8 months ago | parent [-]

Here's the closest thing to data I've been able to find. I have no idea what to do with this info.

https://x.com/jwt0625/status/1848218860513628203

0_____0 8 months ago | parent [-]

The polar plot at the end would be useful if there were plots for other cars and trucks to compare to. I'm assuming that it's a simulation?

rightbyte 8 months ago | parent | prev [-]

I think "stealth" planes assumes the radar is under the plane on the ground? For the geometry. And they have some color or alloy that reflect less.

0_____0 8 months ago | parent [-]

It's cooler than that these days - under the paint are antennas plated? printed? onto the skin panels that are tuned to absorb specific frequencies of interest.

ndileas 8 months ago | parent | prev [-]

"Size" might be as simple as radar cross section. Not necessarily a good thing for us squishy blobs.