LiDAR — short for Light Detection And Ranging — is a laser-based ranging method that measures distance by timing how long a laser pulse takes to return after striking a surface. On a drone, a spinning or solid-state lidar payload fires hundreds of thousands of pulses per second and assembles them into a 3D point cloud. The output is geometrically similar to drone photogrammetry but produced by an entirely different physical principle.
How LiDAR differs from photogrammetry
Photogrammetry reconstructs surface geometry from overlapping 2D photographs. It needs visible surface. LiDAR sends laser pulses and measures return time — the geometry is computed from the pulse-return timestamps, not from images. Two consequences follow:
- LiDAR penetrates vegetation. A laser pulse can find its way through a forest canopy and return from the ground surface beneath. Photogrammetry sees the top of the canopy and stops there.
- LiDAR runs in low light. The sensor provides its own illumination. Photogrammetry needs visible-light conditions and adequate texture for image matching.
Typical drone LiDAR accuracy
- Horizontal: 3-6 cm on well-controlled sites with RTK or PPK GNSS
- Vertical: 3-8 cm depending on payload, flight altitude and ground texture
- Point density: 100-500 points per square metre at typical survey altitudes; substantially higher on slower, lower flights
When LiDAR earns its cost
- Vegetated sites — forestry, pipeline ROW, transmission corridors, parks and natural areas
- Low-light or shadow-heavy environments — deep open pits, canyon walls, north-facing slopes in winter
- Powerline and structural inspection — lidar resolves wires and small linear features photogrammetry struggles with
- Tight-tolerance engineering deliverables where independent geometry redundancy is preferred
When photogrammetry is the better choice
- Open-air sites with good sun angle and adequate surface texture — aggregate yards, urban survey, construction sites
- Projects where the deliverable is the orthomosaic image itself, not just geometry
- Cost-sensitive work — a typical photogrammetry job is 30-60% the cost of an equivalent lidar deliverable
- Recurring monthly stockpile cycles where the geometry is open, repeatable and unobstructed
Blended deliverables
The increasingly common pattern on larger projects is a blended deliverable — photogrammetry for the bulk surface, lidar for the vegetated patches, ground survey for the structural detail. The point cloud and orthomosaic from each method are merged in the post-processing step into a single deliverable.
How UAV Imaging applies LiDAR
The Matrice 300 RTK supports lidar payloads on the dual-payload bay. UAV Imaging deploys lidar for vegetation-heavy mapping (forestry, ROW, pipeline corridor), powerline and transmission inspection, and high-rigour engineering deliverables where independent geometry redundancy is preferred. For most central Alberta open-site work — aggregate, construction, urban survey, ag scouting — photogrammetry is the default tool. The choice is a pre-flight planning decision based on the site and deliverable, not a sales preference.