Waymo's lidar directly measures distance as a physical fact while Tesla's cameras compute it from pixel arrangements — a tradeoff between a costly measurement that can fail and a cheap derivation that can be wrong.

A camera records light intensity across a grid of pixels. Distance appears nowhere in that grid, so depth has to be computed from the arrangement of pixels, but that computation can be wrong. A large object far away and a small object nearby can occupy the same region of an image. Lidar arrives at the same answer by a different route. The unit emits laser pulses, measures how long each pulse takes to return after reflecting off a surface, and converts that interval into a distance. We can think of the output of this as a point cloud, which is a three-dimensional set of measured points describing the surfaces around the vehicle. The distance is no longer an estimate but a measurement. The tradeoff here is that a direct measurement costs money while adding a component that can fail noticeably. However, a derived value may not cost much, but it can be wrong as well.

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