3D scanning existing buildings: LiDAR, point cloud, BIM – white paper

Abstract

Projects in existing buildings are demanding mainly because the data is unreliable: drawings are missing, out of date or contradictory. This white paper by Felsch Lighting Design shows how 3D scans with LiDAR and stereoscopic depth capture record existing buildings completely, neutrally and reproducibly, how the point cloud is georeferenced and transferred to CAD and BIM systems, and what economic benefits this brings. Case studies are the KölnBäder pools in Cologne and the Tempodrom in Berlin.

Key findings

A site walk records selectively and subjectively. A 3D scan measures every visible area – installations under the ceiling, niches, cable routes, unevenness – with metric accuracy and permanently.

LiDAR provides geometric accuracy, stereoscopic cameras provide visual quality. Hybrid systems combine both into a point cloud that allows measurement and intuitive understanding.

Even larger buildings can be captured completely within a few hours.

Georeferencing – globally in the national coordinate system or relative to a project origin – is the basis for collaboration between all trades in BIM.

The workflow from scan to as-built BIM has three phases: clean the point cloud and export it as .las or .e57, model components parametrically, transfer the model into the planning systems.

Scans are most useful at the start of a project as a data basis and at the end as documentation of the as-built state for acceptance and facility management.

Subjective perception and objective capture

During a conventional site visit, the picture of a space is formed from a subjective selection of impressions. Details are forgotten, dimensions estimated and relationships remembered wrongly. Photos only help selectively.

Technical capture systems work completely, neutrally and reproducibly. The scanner measures all surfaces, geometric elements and spatial relationships – regardless of whether they are perceived as relevant. The data is available again at any time, without another site visit.

The challenge of existing buildings

Existing buildings change over the years. Conversions, repairs and temporary solutions are often undocumented, and drawings are incomplete or contradictory. A conventional survey only records what is needed at the moment. If information is missing later, further site visits are necessary. With historic fabric, such as the city palace in Cologne, the scan must also take place before scaffolding goes up.

Technologies: LiDAR, stereoscopy and 360° imagery

LiDAR (light detection and ranging) emits laser pulses and calculates the distance to surfaces from the travel time of the reflected light. Millions of measuring points create an accurate spatial image, regardless of lighting conditions.

Stereoscopic systems calculate depth from the image differences of offset cameras and produce convincing visual documentation.

360° imagery adds a digital walk-through to the survey, making coordination and decisions easier.

Georeferencing as the basis for data integration

With global referencing, the point cloud is integrated into a higher-level coordinate system, such as an official national coordinate system. This suits larger projects with indoor and outdoor areas and trades working in parallel. Relative referencing refers to a project origin and is sufficient if only interiors are captured or no survey data is available.

From measuring point to parametric component

Preparation and cleaning: reduce noise, filter artefacts caused by mirrors or open windows, check registration accuracy, export as .las or .e57.
Model reconstruction: surfaces are translated manually or semi-automatically into walls, ceilings, beams, windows and building services components.
Integration: transfer into CAD, BIM and planning systems as a shared planning space for all trades.

Economic benefits

A 3D scan saves time, reduces effort and avoids errors. Return trips to the site are no longer needed, planning phases become shorter and unnecessary adjustments during construction are avoided. Planning starts earlier and runs in a more structured way.

Case study: KölnBäder

KölnBäder operates numerous indoor and outdoor pools in Cologne that have been extended, refurbished and retrofitted over the years. For alterations to building services and lighting, consistent as-built documents were missing, and site visits were restricted by pool operations. A combined LiDAR and 360° camera system produced a complete point cloud within a few hours. The result: complete documentation of the installations in the ceiling and beam areas, exact heights and distances, and far fewer site appointments – all specialist planners were able to work remotely.

Case study: Tempodrom Berlin

The roof structure of the Tempodrom, with radial ribs and irregular heights, is a particular challenge for structural, building services and event technology planning. The scan provided a reliable basis, reduced safety-critical work at great height and made tight installation areas visible early on.

Outlook and conclusion

The future of planning in existing buildings lies in linking point clouds, BIM models and digital twins. Artificial intelligence will increasingly recognise components and installations automatically, and mobile and robotic systems will capture data during operation and across large sites. 3D scans make reality visible, measurable and traceable – the basis for fact-based planning.

Key terms

LiDAR

Light detection and ranging: optical measuring method that calculates distances from the travel time of reflected laser pulses.

Point cloud

Digital collection of millions of measuring points with exact spatial positions; the basis for measurements, clash detection and CAD/BIM models.

Georeferencing

Spatial positioning of the point cloud, globally in a national coordinate system or relative to a project origin.

.las / .e57

.las is an established exchange format for LiDAR data; .e57 is vendor-neutral and can also store image and sensor data.

As-built BIM

Parametric building model based on real as-built data, with components, materials and technical systems.

Digital twin

Digital image of a real building that is maintained throughout its life cycle and used for planning and operation.

Frequently asked questions

How long does a 3D scan of a building take?

Even larger buildings can be captured completely within a few hours. Processing into a point cloud, floor plans or a BIM model follows in the office.

What is the difference between LiDAR and stereoscopy?

LiDAR measures distances with laser pulses and provides geometric accuracy. Stereoscopy calculates depth from offset camera images and provides visual quality. Hybrid systems combine both.

In which formats is the point cloud delivered?

Usually .las and .e57. If required, an IFC model for BIM and CAFM is created from it.

At what point in a project is a 3D scan worthwhile?

At the start of a project as a reliable data basis, and at the end to document the as-built state for acceptance, later alterations and facility management.

Digital as-built documentation with 3D scans