LiDAR (Light Detection and Ranging) measures distance by timing laser pulses: fire a pulse, catch the reflection, convert time to range. Mounted on aircraft, drones, vehicles or tripods and combined with precise positioning, a LiDAR scanner produces millions of exact 3D points per second — a point cloud that captures terrain, vegetation, buildings and wires with survey-grade fidelity, even beneath forest canopy.
How the measurement works
Each pulse’s travel time yields range; the platform’s GNSS position and inertial orientation convert range into a georeferenced 3D coordinate. Scanning mirrors sweep pulses across the flight path, painting the landscape in dense stripes of points — commonly tens to hundreds of points per square metre from modern airborne systems.
Crucially, one pulse can yield multiple returns: partial reflections from a canopy top, mid-storey branches, and finally the ground. Those last returns are why LiDAR maps terrain under forest where photogrammetry sees only leaves.
Platforms and their niches
Airborne LiDAR covers counties and corridors at survey grade — the source of national elevation programmes. UAV LiDAR brings similar physics to sites and difficult corridors at lower mobilisation cost. Mobile mapping systems scan roads and rail from moving vehicles; terrestrial scanners capture structures and interiors at millimetre detail.
Bathymetric LiDAR adds a green wavelength that penetrates clear water, profiling nearshore seabeds and river channels no aerial camera can reach.
From points to products
Raw clouds become value through classification — separating ground, vegetation, buildings, water, wires — and derivation: bare-earth terrain models, canopy height models, building models, powerline catenaries, flood surfaces.
Classification quality decides product quality, and at terabyte scale it is a production discipline of automated routines plus expert manual refinement and per-tile QC — the core of professional LiDAR services.
Frequently asked questions
What accuracy does airborne LiDAR achieve?
Modern surveys routinely deliver vertical accuracy around 5–10 cm RMSE against ground checkpoints, with horizontal accuracy of a similar order — genuine survey grade over entire landscapes.
Can LiDAR see through trees?
Effectively yes: enough pulses find gaps in the canopy for last returns to sample the forest floor, letting classification reconstruct bare-earth terrain beneath vegetation — LiDAR’s defining advantage over image-based methods.
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