Photogrammetry vs LiDAR: which survey do you actually need?
If you can see the ground everywhere on your site, photogrammetry will almost certainly do the job for less money. If trees or vegetation hide the ground you need to measure, you want LiDAR. That single distinction settles the choice for most UK survey jobs — the rest of this post is the why, the costs and the edge cases.
How photogrammetry works
A drone flies a grid pattern taking hundreds of overlapping photos. Software matches millions of common points between frames and triangulates them into a 3D point cloud — the same depth trick your eyes do with two viewpoints, done with thousands. From that come an orthomosaic (a true-to-scale photo-map), a surface model, contours and a textured 3D mesh.
It measures what the camera can see. That sentence is the entire limitation: photogrammetry needs visible, textured, reasonably lit surfaces.
How LiDAR works
A LiDAR sensor fires laser pulses — hundreds of thousands a second — and times the returns. It’s an active sensor: it brings its own light, doesn’t care about surface texture, and, crucially, individual pulses slip through gaps in foliage and return from the ground underneath. Classify those returns and you get a digital terrain model — the actual ground — under woodland a camera could only photograph the top of.
Where photogrammetry wins
- Price. Camera drones cost a fraction of LiDAR rigs and far more pilots fly them. Typical jobs run £400–£2,000+ depending on site and spec.
- Photo-real outputs. Orthomosaics and textured meshes that planners, clients and committees understand at a glance. A LiDAR point cloud carries no imagery unless a camera is flown alongside.
- Inspection detail. Cracks, slipped tiles, corrosion — visual condition lives in photographs.
- Accuracy on open ground. With RTK/PPK and ground control, photogrammetry matches LiDAR on hard, visible surfaces — the accuracy post has the numbers.
Where LiDAR wins
- Vegetation — the big one. Photogrammetry maps the top of the canopy and calls it ground. On an overgrown plot in July, “ground level” from photos alone can be out by metres. LiDAR returns from the actual terrain through gaps in the leaves.
- Thin structures. Powerlines, lattice masts, steelwork — photo-matching struggles with thin geometry against a busy background; laser returns don’t.
- Uniform surfaces. Fresh tarmac, sand, standing water margins: photogrammetry needs texture to match between frames; LiDAR doesn’t.
- Low light. An active sensor flies at dusk. A camera doesn’t.
What you get back
| Deliverable | Photogrammetry | LiDAR |
|---|---|---|
| Photo-map (orthomosaic) | Yes — its core output | Only if a camera is flown too |
| Surface model (DSM) | Yes | Yes |
| Terrain under vegetation (DTM) | Poor to none | Yes — its core output |
| Textured 3D mesh | Yes | No — points, not pictures |
| Typical formats | GeoTIFF, DXF/DWG, OBJ | LAS/LAZ point cloud, DTM, DXF/DWG |
What each costs
Photogrammetry surveys typically run £400–£2,000+, scaling with area and accuracy spec. Drone LiDAR usually starts around £1,000 and climbs from there — the sensor hanging under the drone often costs more than the van it arrived in, and quotes reflect that. Neither price is padding: LiDAR’s premium is hardware and processing time; photogrammetry’s spread is mostly accuracy spec and site size.
Accuracy: a tie, with an asterisk
Done properly — RTK or PPK positioning, ground control, checkpoints — both methods deliver centimetre-grade results, and on hard open ground there’s nothing meaningful between them. The difference isn’t the headline figure; it’s where the figure holds. Photogrammetry’s vertical accuracy quietly degrades over anything green, because it’s measuring leaves and calling them terrain. LiDAR’s accuracy holds under canopy, which is the whole reason it gets hired. Whichever you commission, ask for the checkpoint report rather than the adjective.
The five-minute decision
- Roof, stockpiles, open fields, construction site, quarry → photogrammetry.
- Woodland, overgrown plots, riverbanks in summer, any job needing ground levels under green → LiDAR.
- Powerlines, masts, lattice structures → LiDAR, usually with photos alongside.
- Need measurements and a photo-real record → many pilots fly both sensors in one visit; ask for a combined quote.
- Deciduous site you can wait on → a leaf-off winter flight narrows the gap, though under dense canopy LiDAR still wins.
Say the site, not the sensor
The practical move: describe the site and the end use — “ground levels across six acres, half of it wooded, for a drainage design” — and let pilots tell you which sensor they’d fly. A pilot who carries both will quote the honest option rather than the one they happen to own, and the ones who only carry a camera should say so when the brief mentions woodland.
Photogrammetry and 3D mapping quotes and land and topographic surveys both run through the same form: one request, up to 4 CAA-certified, insured pilots, free and no obligation. Describe the vegetation honestly — it’s the first thing a good pilot will ask about anyway.