From laser scanner surveys to the BIM model

Scan to BIM is the process of creating the BIM model of an existing building from a 3D digital survey. Discover its many advantages in construction projects

If you are new to the world of BIM methodology or you have already being using it for some time in your work, you have probably heard about ‘Scan to BIM’. But does this process consist in and what are its advantages?

In this article we’ll take a detailed look at construction site surveys from a Scan to BIM perspective based on laser scanner and point cloud workflows also covering some of the main advantages that can derive from integrating these new technologies into building redevelopment projects.

In particular, to fully understand the “Scan to BIM” process, we will analyse a practical example starting from the survey of a historical building.

But what is a Scan to BIM process?

Scan to BIM is the process of creating the BIM model of a building or an existing space, starting from the data acquired from the survey carried out with advanced technologies, such as 3D laser scanning, Structure for Motion and high-definition photogrammetry.

The digital survey outcome processed through specific software is a point cloud or 3D mesh, i.e. a set of points distributed in a three-dimensional space. The point cloud can be imported into a BIM modelling software and used to obtain digital models of the existing building.

The phases of the “Scan to BIM” process

The “Scan to BIM” process can be subdivided into 3 basic phases:

• 3D survey of the building with laser scanner
• data processing
• BIM modelling.

3D survey of the building with laser scanner

The 3D survey of the building subject to a “Scan to BIM” process is an operation that must be carried out in the field by professionals equipped with 3D scanners capable of capturing the entire building. 3D scanners are advanced technologies that facilitate, improve and speed up the survey phase in the field.

The 3D scanner collects data with high speed and precision through a laser beam projected in all directions. When the laser beam hits a solid surface, its position is recorded through a large number of points that are located relative to the scanner in the X, Y and Z axes.

The set of all these points that gives rise to the 3D visualization of the building is called the “point cloud”.

Data processing and treatment

Once the data has been acquired in the field with 3D scanners, it needs to be processed and combined in point cloud editing software. These software extract the physical and functional information of the building from the point cloud scan. The multiple observation points in the scan provide complete visibility of the structure, ensuring an absolutely accurate representation.

At this stage it is advisable to keep in mind the final use to which the point cloud will be destined, because remember that this type of file can be very large. For this reason, the point clouds are generally cleaned and modified, the density of the points is reduced depending on the use or the cloud is divided into sectors or levels in order to be able to work without loading the entire project into the BIM authoring software. and start BIM modeling.

BIM modeling

BIM modeling from the point cloud is not an automatic process. The point cloud is loaded into building design software for BIM modeling and the creation of a 3D BIM model.

The BIM model is created starting from the geometric and spatial information contained in the cloud but is also enriched with all the other complementary information such as brands and models of the equipment, photos and videos that give us visual information about the project.

All this information must be duly incorporated into the model and correctly structured so that the final result of this BIM modeling phase is useful for the different fields of application of the “Scan to BIM” process (requalification, restoration, facility management through a digital twin etc).

“Scan to BIM” fields of application

The reason behind the application of Scan to BIM is to acquire the real conditions of the building, but at this point you are wondering what is the “Scan to BIM” actually used for? At which stage of the project can it be applied?

So let’s examine in which phases it is possible to apply the “Scan to BIM” and how it can be advantageous:

• Design: the BIM model allows designers to better understand the conditions of the site and make better decisions in the design of the building;
• Construction: with BIM it is possible to identify any type of discrepancy between the BIM model as built and a BIM model as designed;
• Facility Management (FM): Thanks to the rich and well-organized 3D visualization and building information in BIM, more FM functionality can be improved, such as space management, renovation planning and execution, emergency management and staff training and development .

The advantages of the “Scan to BIM” process

We therefore clarified how the “Scan to BIM” process allows you to create a highly accurate three-dimensional digital representation of the building in a very short time. But this is only one of the most obvious advantages that the adoption of a scan-to-BIM workflow can give.

Among the main advantages we can mention:

• higher quality of the project: extremely detailed BIM models are obtained, with high quality and accuracy of the assets (land, infrastructures, buildings, etc.) in a short time;
• substantial reduction of errors in the modeling and planning of the project: thanks to an optimal and precise collection of information and data from the environment, the modeling quality level increases;
• significant time savings: the team only has to visit the site once to collect data while subsequent inspections can take place off-site more frequently than on-site, reducing the need for travel;
• decrease in project costs: although it is necessary to incur additional costs for the 3D survey, an important reduction in costs due to the reduction of processing times and the added value of the BIM model is undeniable;
• greater transparency and better collaboration: thanks to the BIM methodology, information can be shared faster and more efficiently.

How to put a “Scan to BIM” process into practice: the GEOSLAM case study

At this point you may be wondering how do I carry out a “Scan to BIM” process? What tools do i need?

Now that we understand how a Scan to BIM process is structured and what are the numerous advantages offered by this survey method, we can go into a practical case. Specifically we will describe the 3 phases of the “Scan to BIM” process to arrive at the realization of the BIM model of a historic building.

To put into practice the “Scan to BIM” process yourself, I recommend that you immediately download the trial version of the point cloud to BIM software. You can import your point cloud or a point cloud example file present on usBIM in the “exemples” folder, and experience the strength of this new technology in the redevelopment of buildings.

Phase 1: Building survey with geoSLAM

In this case study, we conducted a survey of a historical building using the GeoSLAM Horizon. There was no need to bring additional devices or tools to the site and the entire campaign was carried out with a single operator.

This instrument uses SLAM (Simultaneous Localization And Mapping) technology, which enables it to orientate itself in the absence of a GPS signal, based on what is detected during the scanning period. In practice, all the operator has to do is walk with the instrument in a given space (either indoors or outdoors) to automatically generate the point cloud.

Laser scanning with SLAM technology is extremely efficient and fast, requires no additional tools and requires only one operator.

We started off with surveying the building interiors. Once the Scanning equipment was ready and set up, we simply took a walk around the spaces at normal pace avoiding sudden movements, inside each room to be surveyed.

In a just under 10 minutes we completed the scanning campaign and acquired the whole building with its interior environments.

Applying the same technique as for the survey of the interior of the building, we can complete the scanning phase by walking around the perimeter walls.

Laser scanner survey for BIM modelling

Phase 2: Data processing

After that, we could download the scan results into the geoSLAM software comfortably from our office and view the detected point cloud and the route we followed during the survey.

Viewing a laser scanner point cloud with SLAM technology

In just a matter of minutes and with very little effort we obtained a very detailed and complete point cloud. In addition, having surveyed both the interior and exterior of the building, we also obtained the walls thicknesses and all information needed to prepare project drawings and documents. This obviously means that further inspections aren’t necessary as we already have all the information that we need.

At this point, with the point cloud file already available, we were able to export it in the different file formats (.LAS, .LAZ, .E57, etc.) and then import it into our point cloud BIM software.

Phase 3: 3D modelling from point clouds with Edificius

The final step to the true digitisation of the model is the reconstruction of the BIM model of the survey. This is the most delicate and complex phase. In fact, from the three-dimensional surface depicting the surveyed work, it is necessary to pass to a parametric 3D model composed of objects such as walls, windows, doors, etc..

For the 3D modelling we used the BIM software Edificius. One of the great advantages of this software is its integration with the usBIM cloud platform. This integration allows us to:

• manage even large point clouds, taking advantage of the cloud storage space;
• have all the files available at all times and can be shared with other collaborators.

Point cloud viewed on usBIM

So, we first uploaded the point cloud to usBIM.pointcloud and then imported into Edificius only the portion of the cloud on which we wanted to work.

Point cloud import into Edificius

In the point cloud to BIM software we first defined the levels and elevations of the different floors of the building. In this way we were able to easily position the point cloud to align it with our reference system.

Management of the point cloud levels in Edificius

Using the automatic object recognition functions, we have identified the various architectural elements directly within the point cloud:

• vertical envelopes: we modelled the vertical envelopes, simply using the points in the cloud as a guide on which to draw the length of the wall. Using the editor, we then indicated the alignment, thickness, section (constant or variable), angle, etc. and used a series of automations allowed by the software to trace all the walls in the building in no time at all. From the properties we also defined the stratigraphy and materials, choosing objects from the online BIM objects library;

Modelling vertical envelopes from point cloud

• windows: we have drawn the width of the window, again using the 3D point cloud as a guide. From the editor we easily defined the right window height, the height and the approximate values according to our needs. From the properties we specified the type of glass, the frame, the thermal transmittance of each window to have a complete model full of useful information.

Windows modelling from point cloud with Edificius

In the same way, we can model the interior doors and other objects of the building, obtaining in a few steps a 3D model that is extremely faithful to the actual state of the building surveyed.

Scan to BIM: from point cloud to 3D model with Edificius

At this point, the model becomes very easy to obtain all the executive graphic tables complete with plans, elevations, sections and 3D views and to generate static renders, real-time renders and video presentations.

Once the BIM modelling phase is complete, we are ready to export the model in IFC format.

If you want to obtain an IFC model from a point cloud directly online and without using BIM authoring software, you can try a Scan to BIM software instead. This way you create BIM models in openBIM IFC format and create 100% openBIM workflows.