How does a robot find its way without GPS?

Through LiDAR-based mapping: during teach-in, the robot creates a three-dimensional map of its surroundings and continuously compares its position against this map.

The method is called SLAM – simultaneous localisation and mapping. It works entirely without a satellite signal and is therefore the basis for use in buildings, tunnels and basements.

Limits become apparent in very uniform surroundings. To a laser scanner, a long tunnel without distinctive geometry looks almost identical over hundreds of metres. In such cases, a practical test before procurement is advisable.

How this plays out in tunnels is set out under Does the robot work in tunnels without reception?.