LiDAR SLAM

LiDAR SLAM is a way for a robot to build a map of a place and figure out where it sits inside that map, using a laser sensor called a LiDAR. The LiDAR fires thousands of laser pulses every second in many directions and times how long each pulse takes to bounce back, which tells it the distance to whatever it hit. Out of all those distances comes a sharp snapshot of the surrounding walls, furniture, and obstacles — a kind of laser sketch of the room. SLAM stands for simultaneous localization and mapping, the trick of drawing the map and tracking your own position at the same time, even though doing one well seems to require already knowing the other.

The robot works frame by frame. Each instant it takes a fresh laser sketch, then slides and rotates it until it lines up with the sketches it took just before. How far it had to slide and turn to make them match is exactly how far the robot moved — so it recovers its motion from the scans alone, without needing a finished map up front. As it travels, it stitches these aligned sketches together into one growing map, and its tracked path is the chain of all those small movements added up.

LiDAR is prized here because it measures distance directly and precisely, and it works in the dark or in plain rooms where a camera would struggle to find features. The catch is that long featureless corridors, mirrors, and glass can fool it, and small errors in each step slowly pile up into drift — the map gently bends away from reality. To fight this, LiDAR SLAM systems watch for places they have visited before and snap the map back into shape when they recognize one, a correction called loop closure.