Terrestrial Laser Scanning (TLS)
Definition
A ground-based 3D LIDAR survey instrument that captures millions of range measurements per scan to produce a millimetre-accurate point cloud of the scene. Used for permanent scene documentation at major fire and explosion investigations, providing a spatial reference for expert testimony long after the scene is remediated.
- Measurement method
- Time-of-flight laser measurement from a fixed position
- Accuracy
- Millimetre-accurate point clouds
- Scan output
- Dense 3D point cloud of the scene
Common questions
What does a terrestrial laser scanner do?+
TLS fires a pulsed laser in a dense grid of directions from a fixed position and measures distance by time-of-flight. This produces a dense point cloud - millions of range measurements that capture the scene in millimetre-accurate 3D. It works faster and more accurately than photography-based methods.
Why is TLS useful in fire or explosion investigations?+
TLS creates a permanent 3D record of the scene that can be used for reference long after the scene is cleaned up or remediated. This is critical for expert testimony, since the spatial documentation exists in exact detail even when the physical scene is gone.
How is TLS different from photogrammetry?+
TLS fires a laser and measures distance directly without needing photographs. Photogrammetry reconstructs 3D from photos. Both work, but TLS is faster and more accurate per point, though it costs more to deploy.
Related terms
- Structure-from-Motion (SfM)
- A photogrammetric technique in which overlapping images from a drone or camera, processed by software, generate a three-dimensional point cloud and textured...
- Bare-Earth DTM
- A digital terrain model produced by filtering LiDAR returns to ground-level pulses only, removing vegetation and structure returns. The resulting surface represents...
- Cal Fire (California Department of Forestry and Fire Protection)
- California's state fire agency, which has integrated drone aerial survey and multispectral imaging into major wildfire investigations since 2018. Operational use in...
- Curvature
- A DTM derivative measuring the rate of change of slope. Profile curvature (along the slope direction) identifies convex mounds and concave hollows....
- Dense Point Cloud
- A set of millions of three-dimensional coordinate points, each with an RGB colour derived from the photographs, that together represent the surface...
- ENFSI EWG AI Working Group
- The European Network of Forensic Science Institutes Explosives Working Group's artificial intelligence working group, active from 2021. Produced a 2023 position paper...
- Ground Control Point (GCP)
- A physical marker in the scene whose three-dimensional coordinates have been measured independently by total station or GPS. Assigning those coordinates to...
- Handheld Raman
- A portable spectrometer using a near-infrared laser (typically 785 nm or 1064 nm) to measure inelastic light scattering from molecular bonds. Generates...
- Hillshade
- A raster derived from a DTM by simulating illumination from a defined sun position (azimuth and altitude angle). Produces light-and-shadow contrasts that...
- LIBS (Laser-Induced Breakdown Spectroscopy)
- A spectroscopic technique that uses a high-power pulsed laser to ablate and ionise a small amount of sample material, generating a plasma...
- LiDAR (Light Detection and Ranging)
- An active remote sensing technique that emits laser pulses and measures the time of return to calculate distance to reflecting surfaces. Airborne...
- Multispectral Imaging
- Photography or remote sensing in multiple wavelength bands beyond the visible spectrum, including near-infrared and short-wave infrared. Drone-mounted multispectral cameras are used...
Explained in these topics
- Close-Range Photogrammetry and 3D RecordingA survey method that fires a pulsed laser in a dense grid of directions from a fixed position and measures distance by time-of-flight, producing a dense point...
- Emerging Methods: Handheld Raman, LIBS, CT Imaging, MLA ground-based 3D LIDAR survey instrument that captures millions of range measurements per scan to produce a millimetre-accurate point cloud of the scene. Used...
- LiDAR Terrain Analysis for Concealment and DisturbanceGround-based laser scanning from a stationary instrument positioned at one or more stations within a scene. Produces extremely dense point clouds at close rang...