Definition
Terrestrial Laser Scanning (TLS) is a ground-based surveying method that uses a stationary laser scanner to capture the exact shape and dimensions of buildings, sites, and objects. Instead of measuring points one at a time, the scanner fires millions of laser pulses in every direction and records where each pulse lands, producing a dense collection of measured points known as a point cloud.
Because the scanner sits on a tripod on the ground (rather than flying overhead), TLS is especially good at capturing vertical surfaces, interiors, and intricate structures with millimetre-level detail. The result is a highly accurate digital record of a space exactly as it exists at the moment of the scan.
In simple terms, TLS lets you take a precise three-dimensional ‘snapshot’ of the real world that engineers, architects, and surveyors can measure and work from long after they have left the site.
How It Works
A terrestrial laser scanner rotates on its base while a mirror sweeps the laser vertically, allowing it to cover almost a full sphere around its position. For each pulse it emits, the scanner measures either the time the light takes to return (time-of-flight) or a shift in the light wave (phase-based) to calculate distance, then combines that with precise angle readings to fix each point in 3D space.
A single setup rarely captures everything, so surveyors move the scanner to several positions around a site. These individual scans are then aligned, or ‘registered’, into one unified point cloud using overlapping features or reference targets. Many scanners also capture colour photos, so the finished point cloud can look almost photographic.
Applications
TLS is widely used across construction, architecture, heritage conservation, engineering, and forensics. On construction sites it documents as-built conditions and feeds Scan-to-BIM workflows. In heritage work it preserves historic buildings and monuments as detailed digital records. Engineers rely on it for structural monitoring, tunnel and bridge inspection, and clash detection, while surveyors use it to produce floor plans, sections, and elevation drawings quickly and safely.
Benefits
- Extremely high accuracy, often within a few millimetres over short ranges.
- Rapid data capture, collecting millions of points in minutes rather than manual measurements over hours.
- Non-contact and safe, allowing hazardous or hard-to-reach areas to be surveyed from a distance.
- A complete, reusable 3D record that can be re-measured at any time without revisiting the site.
- Strong compatibility with BIM, CAD, and digital twin platforms.
Related Terms
- LiDAR (Light Detection and Ranging)
- Point Cloud
- Scan-to-BIM
- Reality Capture
Frequently Asked Questions
What is Terrestrial Laser Scanning used for?
It is used to create accurate 3D models of buildings, sites, and objects for construction documentation, heritage preservation, structural inspection, and as-built surveys.
What is the difference between LiDAR and a terrestrial laser scanner?
LiDAR is the underlying ranging technology that measures distance with laser light. A terrestrial laser scanner is a ground-based instrument that uses LiDAR from a fixed tripod position, whereas airborne LiDAR captures data from aircraft or drones.
How accurate is terrestrial laser scanning?
High-end terrestrial scanners typically achieve accuracy within a few millimetres at short to medium range, though accuracy decreases gradually with distance.
How long does a TLS scan take?
A single scan position usually takes a few minutes, but the total time depends on how many setups a site needs and how much overlap is required for registration.
About Track3D
Track3D helps organizations transform laser scans, drone imagery, and spatial data into actionable digital twins and reality capture insights. Learn more at Track3D.
