Two different tools for 3D mapping
LiDAR and photogrammetry both produce point clouds, terrain models, and measurable 3D data from a drone flight. But they work through completely different physics, and each has clear strengths depending on what you’re surveying and what you need back.
We operate both LiDAR and photogrammetric platforms at Drone Services Ireland, so we recommend whichever actually fits the project rather than just using what we have on the shelf.
The basics
Photogrammetry
The drone takes hundreds or thousands of overlapping photos. Software finds matching features across multiple images and uses triangulation to work out the 3D position of every identifiable point. You end up with a dense, coloured point cloud and a photorealistic 3D model.
LiDAR
A laser scanner on the drone fires hundreds of thousands of pulses per second. Each pulse bounces off a surface and returns to the sensor, which calculates distance from the time-of-flight. Combined with the drone’s RTK/PPK position and IMU data, each return becomes a 3D point. LiDAR point clouds don’t have colour natively, but you can colourise them from camera imagery captured at the same time.
When photogrammetry is the better choice
- You need visual outputs: Orthomosaics, textured 3D models, and visual site records are native photogrammetry products. LiDAR can’t produce these without a separate camera.
- The site is open: On bare earth, hard surfaces, and construction sites, photogrammetry matches LiDAR accuracy at lower cost.
- Budget matters: Photogrammetric survey typically costs 30 to 50% less than LiDAR for the same area, because the equipment is cheaper.
- Colour and texture are important: For condition assessment, building inspection, and visual documentation, you need the photos.
For a typical topographical survey of a development site, road corridor, or construction project on open ground, photogrammetry gives most engineers everything they need.
When LiDAR is the clear winner
- There’s vegetation in the way: LiDAR pulses pass through gaps in tree canopy and undergrowth to hit the ground. Photogrammetry only sees the top of the vegetation. If you need a bare-earth DTM under trees, LiDAR is your only real option.
- The site is forested or overgrown: Forestry, overgrown brownfield sites, and archaeological sites under vegetation all need LiDAR.
- You need tighter vertical accuracy: LiDAR typically hits plus or minus 2 to 3 cm vertical on bare earth versus 3 to 5 cm for photogrammetry. For fine grading checks or structural deformation monitoring, that matters.
- Power lines and thin features: LiDAR picks up overhead power lines reliably. Photogrammetry struggles with thin linear features.
- Flood modelling: Hydraulic models need the ground surface, not the vegetation canopy. LiDAR is the standard data source for flood modelling in Ireland and the UK.
Accuracy side by side
| Parameter | Photogrammetry | LiDAR |
|---|---|---|
| Horizontal accuracy | plus or minus 2-3 cm RMSE | plus or minus 2-3 cm RMSE |
| Vertical accuracy (bare earth) | plus or minus 3-5 cm RMSE | plus or minus 2-3 cm RMSE |
| Vertical accuracy (vegetated) | Not reliable | plus or minus 3-5 cm RMSE |
| Point density | 100-500 pts/m2 | 50-300 pts/m2 |
| Vegetation penetration | None | Multiple returns per pulse |
More detail in our accuracy guide.
Using both together
For some projects, combining the two gives you the best of both worlds. We regularly fly LiDAR and camera payloads on the same mission to produce:
- LiDAR bare-earth DTM (for engineering design and flood modelling)
- Photogrammetric orthomosaic (for visual base mapping and planning drawings)
- Combined colourised point cloud (LiDAR geometry with photographic colour)
This combined approach works well on large renewable energy projects, construction sites with mixed terrain, and environmental assessments needing both topographic and visual data.
Rough cost comparison
- Photogrammetry: From around 500 to 800 euro for small sites, scaling with area
- LiDAR: Typically 40 to 60% more than photogrammetry for the same area
- Combined: About 20 to 30% on top of LiDAR alone
The gap narrows on larger sites where mobilisation cost (same either way) becomes a smaller share of the total.
Not sure which you need?
Send us your site details and deliverable requirements. We’ll recommend the most practical and cost-effective approach. See our LiDAR service or photogrammetric survey service for more.