What does the spinning device on Google's Self-Driving car do?

It is a Velodyne 32 or 64 series lidar. The number corresponds to the number of individual lasers within the rotating housing. They all send out short pulses of light and measure the time before some reflected light is sensed, essentially they are optical radars. read more

Google kickstarted its own self-driving car project in 2008, and it has been rumbling on ever since, first with modified Toyota Prius and then with customised Lexus SUVs, which took the car’s existing sensors, such as the cruise-control cameras, and added a spinning laser scanner on the top. read more

Google has long pitched self-driving cars as a way to cut down on traffic deaths (more than a million worldwide every year) and as a tool for those who cannot drive. It's an altruistic spin on an industry whose potential value Boston Consulting Group pegs at $42 billion a year by 2025. read more

Google’s driverless car tech uses an array of detection technologies including sonar devices, stereo cameras, lasers, and radar. All these components have different ranges and fields of view, but each serves a particular purpose according to the patent filings Google has made on its driverless cars. read more