The LiDAR device plays a central role in the navigation process: it’s used to gather information about the objects surrounding the robot (walls, doors, etc).

Screenshot from 2014-11-20 18_06_56

Fig. 1 – Basic scanning in ROS

In the picture above ‘Basic scanning in ROS’, we see two things: the robot, as represented by the red circle, and the “range data” as represented by the white dots. This range data represents the basic information produced by the LiDAR device.

Internally, the LiDAR device is composed of a range measurement sensor that repeatedly transmits a pulse of light. This pulse of light hits a target (wall, person, cardboard box, etc), then bounces off and returns to the range measurement sensor. By measuring how long it takes for the light to travel out and return back, the sensor can determine the distance to the object. Additionally, the range sensor is mounted on a spinning platform that allows the device to take these range measurements at many points around a 360 degree sweep. As the range measurement sensor is rotated, range readings are taken rapidly (1000’s of samples per second), and this yields a two dimensional view of the entire surroundings of the robot.

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