What SLAM means
SLAM (Simultaneous Localisation and Mapping) is the technique that lets a device build a map of an unknown space and locate itself within that map at the same time. In surveying it powers handheld and mobile scanners that capture dense 3D point clouds simply by being carried through a building, tunnel or site — with no GPS and no fixed setup. For the buying side of this, see our handheld SLAM scanner buyer's guide.
How SLAM scanning works
Many times per second, three things happen together:
- The LiDAR measures range — a rotating laser builds a 360° slice of distances.
- The IMU tracks motion — accelerometers and gyroscopes record how the device moves between slices.
- The SLAM algorithm fuses both — stitching each slice onto the growing cloud and estimating your path.
The main challenge is drift: small motion errors accumulate over distance. SLAM fixes this with loop closure — when you revisit a place already scanned, the algorithm recognises it and snaps the trajectory back into alignment, spreading the error out.
LiDAR SLAM vs visual SLAM
| Type | Sensor | Strengths | Weakness |
|---|---|---|---|
| LiDAR SLAM | Laser + IMU | Works in the dark, robust geometry, accurate | Struggles in long featureless tunnels/corridors |
| Visual SLAM | Cameras + IMU | Rich colour/texture, low cost | Needs light and texture; fails in the dark |
Most survey-grade handhelds use LiDAR SLAM and add RGB cameras to colourise the cloud — combining the robustness of laser geometry with the readability of colour.
What SLAM scanning is used for
SLAM shines wherever you must capture a lot of space quickly: as-built documentation, BIM, renovations, real estate, mining, forestry and heritage. Typical accuracy is 1–5 cm — see our SLAM accuracy guide for the full picture, and the SLAM vs total station comparison for where it fits alongside other methods.
Frequently Asked Questions
What does SLAM stand for?
SLAM stands for Simultaneous Localisation and Mapping. It is the technique that lets a moving scanner build a 3D map while tracking its own position within that map, without GPS.
Is SLAM scanning accurate?
Handheld SLAM scanning typically reaches 1–5 cm accuracy, with relative (local) accuracy often 1–3 cm. That suits BIM, as-built and documentation, but not millimetre control work.
What is the difference between LiDAR SLAM and visual SLAM?
LiDAR SLAM uses a laser and works in the dark with robust geometry. Visual SLAM uses cameras and needs light and texture. Many scanners combine LiDAR SLAM with RGB cameras for colour.
Does SLAM scanning need GPS?
No. SLAM determines position from its LiDAR and inertial sensors, so it works indoors and underground. You georeference the cloud afterwards using control points or a GNSS receiver.