Lidar waveforms are worth 40x128x33 words | Hacker News Reader

Lidar waveforms are worth 40x128x33 words

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43 pointsteleforce14 comments

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168,960

Clearly 10,813,440. Gotta factor the words!

Can lidar be purchased for hobbyist use yet?

https://www.adafruit.com/product/4010

Depends on your budget and the resolution you need.

E.g Livox mid 360 https://store.dji.com/en/product/livox-mid-360

Check out PiLIDAR for one of many options:

https://github.com/PiLiDAR/PiLiDAR

I haven’t done it myself but I’ve heard of people harvesting LiDAR units from their old/broken robot vacuums.

Sure. Line scan indoor units are extremely affordable, and some cost less that $20, sold as spare parts for robot vacuum cleaners. Outdoor units (with higher ambient light tolerance and longer range) are an order of magnitude more expensive, but also available.

Here is some detailed information about low cost units: https://github.com/kaiaai/awesome-2d-lidars/blob/main/README...

BTW with self-driving cars, what happens when there are hundreds of Lidar signals at one intersection?

There's no way a sensor can tell if a signal was from its own origin?

Guessing any signal should be treated as untrusted until verified somehow

but I suspect coders won't be doing that unless it's easy

If one lidar hits another, it will result in at most one bad reading (perhaps a bad column?). This can likely be filtered, or a bad scan (360deg) can be altogether rejected and the data predicted using models based on past sensor readings.

I guess phase and timing sensitivity help a lot, because it's unlikely that another emitter will perfectly match your emission/detection duty cycle. It's also hard to get hundreds of cars at one intersection, because cars are very big.

The key terms in your literature/patent search should probably be "Crosstalk" and "multi-LIDaR".

Typically you use a pulse train and filter your train from the noise

Worked adjacent to the AV space 5~ years ago. This wasn’t my area but I remember learning that this was a robustly solved problem long ago.

> There's no way a sensor can tell if a signal was from its own origin?

https://ui.adsabs.harvard.edu/abs/1978ntc.....2...18F/abstra...

https://apps.dtic.mil/sti/tr/pdf/ADA218226.pdf

> An increasingly popular modulation scheme is Binary Pseudo Random Phase Coding (BPRPC), whereby the phase of the transmitted signal is switched between 0 and 180 under the control of a binary pseudo random sequence

this applies straightforwardly to lidar

basically: optical CDMA or DSSS

spoofing replay may still be a concern

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