There’s a laser scanner that sits on top of the car and spins really fast. Sixty-four laser beams constantly sweep the area to detect and measure the distance of objects around it. Using this data, we can build accurate three-dimensional maps of the streets we’re on. We also use sensors to ‘localize’ the car. The car’s tires are equipped with encoders, which allow it to sense how many times it has turned over or what fraction it has turned, so the car can calculate how far it’s moved. Machine learning, wireless networks, and improved computing power have allowed us to do this, at this moment, and at the scale Uber needs it to be done.