What is an Occupancy Grid Map?

An occupancy grid is one of the simplest types of map that can be generated for robotics applications. The robot observes it’s surrounding area, and generates a map of which parts are occupied, and which parts are not.

Requirements

In order to generate an occupancy map, you need two things.

1. The precise location and rotation of the robot
2. A way to measure the distance to obstacles, such as a laser rangefinder, lidar or an ultrasound sensor

The robot does observations of the two data points regularly, and combines them to update its occupancy grid map.

Noise and precision

The algorithms for generating an occupancy grid map are probabilistic, meaning that they can handle noisy readings from the obstacle sensors. Unfortunately, keeping track of the position of robot is much more difficult. Without a precise position, the map will become very noisy and depending on the amount of inaccuracy, it might end up being completely unusable.