Point a laser at something and time how long the light takes to bounce back. Do that 4,000 times a second while spinning the sensor in a full circle, and suddenly your robot knows exactly where every wall, chair leg, and wandering cat is — all in real time.
What is LiDAR?
LiDAR stands for Light Detection and Ranging. A small motor spins a laser emitter and receiver around a central axis, typically at 5–10 Hz (rotations per second). Each pulse of infrared light bounces off an obstacle and returns; the sensor measures the time of flight (TOF) to calculate distance.
The result is a continuous stream of distance readings arranged around a 360° ring — a point cloud. Affordable units like the RPLidar A1 produce 2,000–4,000 samples per rotation with a range of up to 8 metres — for a hobby robot, the cheap spinning disc does the job brilliantly.
A spinning ring of measurements
As the laser sweeps round, each pulse records the distance to whatever it hits at that angle. Stitch all the angles together and you get a top-down outline of the room — distances in every direction at once, not just straight ahead:
wall (28 cm)
· · · · · · · · · ·
· ·
· ↖ ↑ ↗ · wall
· ← [L] → · (1.1 m
· ↙ ↓ ↘ · behind)
· ·
· · · · · · · · · ·
[L] = LiDAR spinning at 5–10 Hz
· = a returned distance sample (a point)
Each spoke = one laser pulse + its echo time.
2,000+ spokes per rotation = a full 360° point cloud.
Where a single ultrasonic sensor sees one direction, the LiDAR hands your robot the whole room at once — which is exactly what map-building and path-planning need.
LiDAR is unaffected by ambient light levels, which makes it far more reliable than cameras in dark or glare-heavy environments.
Why robot builders care
A single ultrasonic sensor tells you there’s something 30 cm ahead. A LiDAR tells you there are walls 28 cm ahead, 42 cm to your left, and 1.1 metres behind — all at once. That rich spatial data is what makes truly autonomous navigation possible.
With a LiDAR you can:
- Build a 2D floor plan of a room in real time (SLAM — Simultaneous Localisation and Mapping)
- Detect and avoid obstacles in every direction without turning the robot
- Give a path-planning algorithm the data it needs to choose routes intelligently
- Localise the robot inside a known map
LiDAR is the core sensor in most serious mobile robots, from Roombas to self-driving cars. Getting one spinning on your own build is a massive step up from bumping into walls.
Get started
The RPLidar A1 from Slamtec is the most popular entry-level unit. It connects via USB (or UART) and costs under £100. Pair it with a Raspberry Pi and you have everything you need to produce your first live map.
Kevin’s Guiding Light post walks through mounting an RPLidar on a Raspberry Pi Zero 2W, installing ROS, and visualising the scan output in Rviz — a great first project that takes you from zero to spinning laser in an afternoon.
Once you’ve seen a live scan, the natural next step is SLAM. Kevin’s Viam SLAM post uses the Viam robotics platform to build a full room map and navigate it autonomously, with LiDAR as the primary sensor. The Cubie-1 robot uses exactly this setup, and the LidarBot project shows a compact Pico-based build that uses LiDAR for obstacle avoidance.
If you want to go deeper, the Learn ROS with me course covers the full software stack around LiDAR data — scan topics, transforms, and the nav stack that turns raw distance readings into a robot that can find its own way home.
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