Lidar and Self-Driving Cars

From Wired, 2/6/18 https://www.wired.com/story/lidar-self-driving-cars-luminar-video/

"IF YOU'VE BEEN in Silicon Valley, Pittsburgh, Boston, San Francisco, or any of the other cities where autonomous cars are crawling the streets in a 21st century version of drivers ed, maybe you've wondered: What's up with that overgrown gumdrop-looking spinning thing on the roof? That, dear carbon-based life form, is lidar, perhaps the most important piece of hardware in the race to unlock self-driving cars for everybody.

Lidar works much like radar, but instead of sending out radio waves it emits pulses of infrared light—aka lasers invisible to the human eye—and measures how long they take to come back after hitting nearby objects. It does this millions of times a second, then compiles the results into a so-called point cloud, which works like a 3-D map of the world in real time—a map so detailed it can be used not just to spot objects but to identify them. Once it can identify objects, the car's computer can predict how they will behave, and thus how it should drive.

Self-driving cars use other sensors to see, notably radars and cameras, but laser vision is hard to match. Radars are reliable, but don't offer the resolution needed to pick out things like arms and legs. Cameras deliver the detail, but require machine-learning-powered software that can translate 2-D images into 3-D understanding. Lidar, by contrast, offers hard, computer-friendly data in the form of exact measurements.

That's why every serious player in the self-driving car race believes the laser sensor is an indispensable ingredient for a fully robot car, the kind that doesn't need a steering wheel or a human hand. (The notable exception is Tesla's Elon Musk, who insists cameras can do the job.) This is why lidar is at the center of the blockbuster legal case between Waymo and Uber: The company that started life as Google's self-driving car project says that when its longtime engineer Anthony Levandowski left for Uber, he brought Waymo's lidar trade secrets with him.

It's also why dozens of companies are competing to overcome lidar's key weakness: It's too young for a rough life on the road."

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