Scanning a building in 3D means measuring millions of points on its surfaces (walls, slabs, façades, roofs, building services) to produce a point cloud: a measurable digital copy of the existing building. Three technologies do the job: the terrestrial laser scanner (millimetre accuracy), the mobile scanner (speed indoors) and drone photogrammetry (roofs and façades). From that cloud you then extract 2D drawings, areas or a Revit/Archicad BIM model ready to use for a renovation, conversion or asset management project.
That is the definition. The rest of this guide unpacks what those three sentences condense: which technology for which building, what accuracy to expect in practice, how a survey actually unfolds, and what you receive at the end.
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The three 3D scanning technologies: strengths, limits, accuracy
No single technology covers everything. A well-designed survey often combines two methods; a badly designed one applies the wrong method everywhere. Here are the three families, with realistic accuracy figures rather than the ones in the sales brochures.
The terrestrial laser scanner (Leica RTC360 class): the benchmark for accuracy
The terrestrial scanner sits on a tripod and sweeps its surroundings through 360°, one station after another. An instrument such as the Leica RTC360 captures up to 2 million points per second and reaches an accuracy of around 2 to 3 mm at 10 m, roughly 5 mm at 40 m. It is the reference technology whenever geometry really matters: deformed structures, old buildings that are out of square, mouldings and heritage features, flatness checks.
Strengths: the best accuracy on the market, a uniform point density, and HDR panoramic images tied to the cloud (useful for resolving doubts during modelling).
Limits: time. Each station covers only what it can “see”; a partitioned interior (corridors, small rooms, stairwells) multiplies the stations. On a block of flats, the terrestrial scanner alone can turn one day on site into three.
The mobile scanner (NavVis VLX class): speed indoors
The mobile scanner is worn (harness or backpack) and captures while walking, relying on SLAM technology (simultaneous localisation and mapping). The operator walks the floors and the points are recorded continuously. Accuracy is lower than the terrestrial scanner: expect an order of magnitude of 5 to 15 mm depending on the length of the route and the quality of the registration. Indoors, however, its productivity is in a different league: an office floor is covered in minutes, not hours.
Strengths: speed in complex, partitioned interiors, car parks, attics and basements; less disruption for occupants (the walk-through is brief).
Limits: lower accuracy than the terrestrial scanner, sensitivity to drift on very long routes (corrected with control points), and reduced performance in very large empty spaces or repetitive environments where the SLAM “loses” itself.
In practice the two complement each other: on a multi-storey building in Geneva we combined the RTC360 for the demanding areas and NavVis for the circulation zones and standard floors. Accuracy where it counts, speed everywhere else.
Photogrammetry and drones: roofs, façades, external volumes
Photogrammetry reconstructs 3D geometry from hundreds of overlapping photographs taken by drone (or from the ground). With ground control points measured on site, accuracy reaches an order of 1 to 3 cm, depending on image resolution and flight altitude. It is the method of choice for what a scanner cannot see from the ground: roofs, chimneys, inner courtyards, tall façades, the surrounding terrain.
Strengths: access to high areas without a lift platform or scaffolding, photographic texture (valuable for heritage façades), and cost on large external sites.
Limits: centimetre accuracy (not enough for an interior renovation), dependence on light and weather, and the regulatory framework for drone flights in Switzerland (airport zones, built-up areas), which has to be built into the preparation.
In short
| Technology | Typical accuracy | Ideal ground | Main limitation |
|---|---|---|---|
| Terrestrial scanner (RTC360) | 2–5 mm | Structures, heritage, demanding geometry | Slow in partitioned interiors |
| Mobile scanner (NavVis) | 5–15 mm | Interiors, car parks, long runs | Lower accuracy, SLAM drift |
| Photogrammetry / drone | 1–3 cm | Roofs, façades, exteriors | Weather, regulations, interiors |
The 3D survey workflow, step by step
A 3D scan is not a site visit with a gadget: it is a protocol. Four steps, each of which determines the quality of the final deliverable.
1. Preparation
Before the first point is measured: defining the scope (which rooms, which levels, exteriors or not), choosing the technologies to suit the building, organising access (keys, badges, notifying tenants on behalf of a property manager), and identifying constraints (occupied premises, cluttered cellars, drone flights to authorise). This is also when the expected level of detail of the deliverable is decided, because it drives the scan density. Sloppy preparation is paid for in return visits to site.
2. Acquisition
The fieldwork itself. As a rough guide, a detached house is scanned in half a day to a day; a block of flats takes one to several days depending on the number of levels and how cluttered it is. The operator follows a planned route, checks the overlap between stations or trajectories, and places reference targets or spheres that will be used for registration. The building does not need to be empty, but anything that hides a wall (a wardrobe, a pallet, a temporary lining) is a wall that goes unmeasured.
3. Registration (assembling the clouds)
Back in the office, the dozens or hundreds of stations and trajectories are assembled into a single, coherent cloud: this is registration (or consolidation). The software aligns the clouds with one another using the overlap zones and the targets; the operator checks the registration residuals. Careful registration keeps the assembly error at millimetre level across the whole building; careless registration produces “double” walls and slabs that do not meet, defects that no amount of modelling will fix afterwards.
4. Georeferencing
The last step, and the one most often forgotten in enquiries: tying the cloud to the Swiss reference frame, MN95 (LV95) coordinates in plan and LN02 heights, using points measured by a land surveyor. Essential as soon as the survey has to interact with the cadastre, a land surveyor’s plan, a building permit application or other surveys. For a purely interior project, a local coordinate system may be enough; the choice is made during preparation, not after the fact.
From point cloud to deliverables
The raw point cloud is heavy (several tens of gigabytes for an apartment building) and cannot be “read” like a drawing. The value lies in what you extract from it.
The delivered point cloud (E57, LAS/LAZ, RCP). The standard exchange format is E57 (an ASTM standard), readable by most professional software; RCP (Autodesk ReCap) provides a direct bridge to Revit and AutoCAD. A properly delivered cloud is cleaned (passers-by, vehicles and measurement noise removed), structured by level or by zone, and documented: coordinate system, density, acquisition date.
2D drawings (DWG, PDF). Cut directly from the cloud: floor plans, sections, elevations, with the real dimensions of the existing building rather than those of a 1970s archive drawing. Sufficient for many light-renovation files or lettable-area updates.
The BIM model (Revit, Archicad, IFC). Scan-to-BIM: modelling the existing building from the point cloud, at the agreed level of detail (LOD 300 as standard, which covers most renovation projects; another level can be discussed at quote stage), delivered in native Revit or Archicad format (both are common practice in French-speaking Switzerland) and in IFC for exchange. This is the deliverable that carries the most value: SIA 416 areas that can be calculated, design options drawn directly into the existing building, quantities that can be extracted. Several articles in this series are devoted to it, including the guide to LOD 100–400.
A word of caution drawn from a real case: a client sent us the existing E57 of a barn in Vaud, produced by a third party, to have an Archicad model made from it. On analysis, the cloud was not good enough for proper use: patchy overlap, whole areas missing. It had to be re-scanned. The lesson: insist on the E57 and have it audited before ordering any modelling based on it. And if you are thinking of swisstopo’s public LiDAR data as a starting point, read our comparison Swiss public LiDAR vs dedicated scan: its decimetre accuracy and aerial coverage are no substitute for a building survey.
What a 3D scan is for, depending on who you are
Architect working on a renovation or conversion. The central use case. Archive drawings lie: undocumented added storeys, partitions that have moved, levels that do not match. The scan delivers the real existing building, to the millimetre where it matters, and the BIM model becomes the direct basis for the preliminary design, the construction drawings and the building permit application. The manual survey time saved is counted in days; the site surprises avoided, in tens of thousands of francs.
Property management and portfolio management. Reliable lettable areas (SIA 416 basis), up-to-date drawings for inspections and maintenance tenders, documentation of a car park or plant rooms. And a less expected use: selling. A Geneva property management firm had a house surveyed and modelled before putting it on the market; the 3D file helped close the sale by giving buyers a complete, verifiable reading of the property.
Building owner. A 3D scan is insurance: a dated, documented and measurable record of the existing building before works (a useful reference in the event of a dispute), during works (checking that execution complies) and after (an as-built record based on reality). For a public or institutional owner, it is also the foundation of a long-term BIM strategy for facility management.
FAQ: the questions we get asked
How accurate is a 3D building scan? Around 2 to 5 mm for a terrestrial laser scanner, 5 to 15 mm for a mobile scanner, 1 to 3 cm for drone photogrammetry. The accuracy of the final deliverable also depends on the registration and, for a BIM model, on the agreed modelling tolerances: an old wall is never perfectly flat, and the model deliberately idealises it.
How long does a 3D survey take? Allow 3 to 4 working days in total for a small property such as a detached house. Acquisition is fast (around 400 m² per day per team) and processing (registration, cleaning) takes a few days. When a BIM model is ordered, modelling makes up most of the lead time (roughly 100 m² per day per modeller): 16 to 20 working days for a 1,500 m² building, for example. Beyond that, we split the work into lots and add resources.
How much does a 3D building scan cost in French-speaking Switzerland? A scan on its own (delivery of the point cloud) starts at CHF 610; a full survey with a BIM model starts at CHF 1’350. As an anchor, for roughly 850 m²: around CHF 5’350 for survey + BIM model, around CHF 2’850 for the scan alone. The detail of the price factors (floor area, chosen service, scope options such as MEP, furniture or a SIA 416 report, number of levels) is covered in our dedicated article: How much does a 3D survey cost in French-speaking Switzerland? For a figure on your own project: quote in 2 minutes.
Does the building have to be empty to be scanned? No. We scan occupied, furnished premises every day, at no extra charge. Two caveats: anything that hides a surface will not be measured (furniture against walls), and the occupants must be told about the visit, which we coordinate with the property manager or the owner.
What is the difference between a 3D scan and a traditional survey with a laser measure? A laser measure records a few hundred dimensions chosen on site; the scan measures everything, with no pre-selection. You go back to site “virtually” as often as you like: a forgotten dimension is taken from the cloud, not on a second visit. Above a certain floor area or complexity, the scan is also cheaper; the exact threshold depends on the project.
Which file format should I ask for? At the very least the cloud in E57 (an open standard), with the coordinate system stated. Add RCP if you work in Revit/AutoCAD, DWG for the 2D drawings, and the native format (RVT or PLN) plus IFC for a BIM model. Refuse any “viewing only” deliverable from which you could extract nothing.
From the question to the figure
You now have the map: technologies, accuracy, workflow, deliverables. The logical next step is a figure for your building. Our configurator gives you a transparent estimate in 2 minutes (floor area, service, options), with no email exchange or prior meeting. And for the detail of our acquisition service, see the 3D scan only page.