Laser scanning or photogrammetry — which one measures your building?
Both produce a point cloud, and there the resemblance ends. One measures distance directly; the other infers geometry from overlapping photographs. The difference decides whether your survey works in a dark basement, whether it holds dimensional accuracy across a facade, and whether it can be done at all in an occupied building.
The short version
- A laser scanner measures distance directly, millions of times a second, and does not care about light.
- Photogrammetry reconstructs geometry from overlapping photographs, and depends entirely on light and texture.
- Indoors, in basements or on blank surfaces, photogrammetry degrades badly or fails outright.
- On a well-lit textured facade, photogrammetry produces excellent colour and comparable accuracy for less money.
- Most building surveys need laser scanning; photogrammetry earns its place on exteriors and roofs.
Side by side
| Criterion | Laser scanningMeasures distance. Indifferent to light. | PhotogrammetryInfers geometry from photographs. |
|---|---|---|
| How it works | Direct distance measurement by laser pulse | Geometry computed from overlapping photographs |
| Typical accuracy | ±2 to ±5 mm, consistent across the cloud | ±5 mm to several centimetres, varying with conditions |
| Lighting | Works in complete darkness | Needs even light; fails in low light |
| Blank or glossy surfaces | Handled, though glass remains difficult | Fails — no texture means no matching points |
| Colour quality | Good, from the integrated cameras | Excellent, at full photographic resolution |
| Indoors | Reliable, including basements and voids | Unreliable, often unusable |
| Roofs and high facades | Limited by line of sight from the ground | Strong when flown by drone |
| Time on site | Half a day for a flat | Comparable outdoors, longer indoors |
Choose laser scanning when
- The survey is indoors, which is most building work
- Basements, plant rooms or voids are in scope
- Walls are painted flat with no texture to match against
- The model will be used for fabrication, where accuracy has to be consistent
- The building is occupied and the visit has to be quick and unobtrusive
Photogrammetry earns its place when
- The subject is an exterior facade in good even light
- A roof has to be surveyed and a drone can fly it
- Photographic colour fidelity matters more than millimetres
- The building is textured — stone, brick, weathered render
- Budget is tight and the tolerance genuinely allows it
What we would do
On the work we are asked for, laser scanning does the survey and photogrammetry supplements it. A facade flown by drone adds roof geometry and photographic colour that ground-based scanning cannot reach; the interior, the basement and anything being fabricated to fit come from the scanner. Choosing photogrammetry alone for an interior survey is where projects go wrong, and it is usually discovered too late to redo cheaply.
Common questions
Is photogrammetry cheaper?
On paper, and sometimes in practice on an exterior. Indoors the saving usually evaporates: the capture takes longer, the result needs more cleanup, and blank painted walls produce holes that have to be filled by hand or by a second visit. The cheapest survey is the one you only do once.
Can photogrammetry produce a BIM model?
Yes, if the cloud is good enough. The question is whether it is. On a textured exterior it often is. On a white-walled interior it usually is not, and modelling from a cloud full of holes produces a model full of assumptions.
Do you use drones?
For roofs and high facades, where line of sight from the ground runs out. The drone survey is registered onto the same coordinate base as the laser scan, so roof and interior sit in one coherent model rather than two files that nearly line up.
Which one for a heritage facade?
Both, usually. The laser scan gives you dimensional accuracy for the modénature and the profiles; photogrammetry gives you the photographic record of the stone, the weathering and the repairs. Conservation work tends to need both kinds of truth.