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Comment by rightbyte | Hacker News Reader

"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.

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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.

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.

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.

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.

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.

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.

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

Thanks. Spot on!

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

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.

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

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?

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.

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.

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

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