Scan to BIM: from 3D laser scanning to the BIM model

It is the set of millions of points measured by the laser scanner, each one with its position in space and, when the capture is in colour, its colour value. Seen together they reproduce the actual geometry of the building or facility, including the deformations and deviations it really has. It is not a BIM model yet: it does not tell a wall from a duct and carries no associated information. It is the raw material for the modelling that follows in Revit.

In the starting point. In Scan to BIM the current state is measured with 3D laser scanning and the model is built on that measurement. In CAD to BIM the starting point is existing drawings or CAD files, which show what was designed and not necessarily what was finally built: unrecorded refurbishments, site deviations or services that were moved. If those drawings are reliable, CAD to BIM is faster and cheaper. When they are not — or simply do not exist — scanning is the only way to know what is there.

The scope is defined at the start of each project, depending on what the model will be used for. Typically we deliver the BIM model in Revit together with the processed point cloud and the 360° imagery from each scan position. The disciplines modelled — structure, architecture, building services — and the level of detail of each one are agreed before starting, because they are what drives cost and schedule the most. If the model is going to feed a digital twin or a maintenance system, we prepare it for that use as well.

Yes. The survey can be limited to the areas or disciplines that matter: a single floor, a plant room, the service routing of one wing. It is a common way to start when the investment has to be justified: the critical area is digitised first and extended later if the project calls for it. What should be decided before going on site is how far the scan reaches, because setting the equipment up again to cover a forgotten area costs more than having included it from the start.

We have digitised more than 500,000 m² with laser scanning, mostly in industrial buildings, and have also applied it in historic buildings, car parks and stadiums. In general it fits whenever something already built has to be worked on: refurbishments, retrofits, services over existing structures, as-built documentation or digital twins for maintenance. Size is not a limitation; what changes is how the capture is planned.

Not necessarily. Besides the full service — capture, processing and modelling — we rent out Leica RTC360 scanners with specialised technical support for teams that prefer to carry out the capture themselves. Hiring only part of the process is common too: some clients ask us just for the registered point cloud, and others already have one and commission only the BIM modelling.

Two different things are worth separating. The point cloud inherits the accuracy of the scanner, which is millimetric on the equipment we work with. The accuracy of the BIM model also depends on the agreed level of detail: modelling the envelope and structure of a building is not the same as reproducing the full routing of services with their fittings. That is why tolerance and LOD are set at the start, based on what the model will be used for, and not the other way round.

It depends on the size and, above all, on the level of detail of the model. Capture is the fastest and most predictable stage: on an industrial complex we documented more than 100,000 m² in 20 days, with a team of 6 technicians and over 100 scan setups a day. Point cloud registration and the modelling that follows are planned according to the agreed scope, and they are what drives the overall schedule. Given the size of the asset and the intended use of the model, we can commit to a specific timeframe.

The model is developed in Revit, which is the usual working environment of our clients. From there it can be exported to IFC for openBIM exchange with other platforms, and the 2D documentation derived from the model can be generated in formats AutoCAD opens. The point cloud is delivered in formats compatible with both Revit and the usual viewers. The specific delivery formats are agreed at the start of the project, along with the rest of the scope.