Scan To BIM: What you need to know about this method for modeling an existing building

20 June 2018 by Snapkin

 

If BIM and digital models are widely adopted in the new-build sector, their use in renovation and rehabilitation projects or simply for maintenance issues and the use of buildings is not an easy task. First, you must capture reality using laser scanner technology, and then proceed to modeling that into a digital mockup.

 

Why use 3D scanners?

Because we estimate that a scan is five times faster than the traditional method, 3D scanners today are the optimal point of entry for creating digital models of existing structures. Whether stationary or mobile, a scanner projects a laser in all directions around its axis to detect distances to each wall. Several models exist with prices ranging from 15,000 € to more than 80,000 € with varying levels of precision.

“3D scanners are the most efficient and reliable option for digitizing a building. Indeed, contrary to 2D plans, which very often prove to be outdated, these machines can create a replica of a building “as built”, taking into account all the specifics of the structure”, explains Tristan Aurigny, BIM manager in the surveyor’s office at Alpes Topo. Using a scanner model, numerous deliverables are possible, such as digital plans/mockups (interiors, facades, etc.) as well as area calculations.

As such, the model represents an excellent foundation for technical or legal studies. “The BIM digital model made from a 3D laser scanner building diagnostics is now more accessible, and a growing number of professionals are equipped with scanners”, explains Etienne Ternisien, head of modeling at ITGA. “By integrating information from the diagnosis such as, for example, the presence of asbestos, it allows for better knowledge of the building by the project owner, and represents a real added value for the diagnostician’s services. This is especially the case for housing authorities whose number of bids is increasing.

What are the steps to follow for a successful scan?

If you wish to scan your property in order to create a digital avatar, you must either purchase or rent a scanner, or call a provider (surveyor, scanning company, etc.). The scan can be done in any type of infrastructure – empty or not, but the amount time spent scanning will be higher or lower depending on the size of the space. The site survey then generates what are called point clouds: three-dimensional georeferenced coordination points. These point clouds are then merged into a single file, which must be reprocessed or “transferred” manually using dedicated CAD software in order to create a digital 3D model.

What are the limitations of this method and its solutions?

The main limitations of the scanner survey are, first and foremost, the cost of the equipment which, of course, continues to decrease but nevertheless represents a significant investment, especially for small structures. 

point cloud sample

Leasing is an option if you wish to internalize this competence. Additionally, laser scanner technologies are capable of capturing only what’s visible. To digitize networks (such as electrical, HVAC or infrastructure), the drop ceiling, for example, must be removed. The result of the scan is represented by a point cloud, which contains thousands or even millions of data points. Given the large amount of information it contains, the file is often very large. This makes sharing and storage difficult. The type of building heavily influences the file size. For example, the point cloud for a 12,000 square meter high school building can be 120 GB. Additionally, processing a 120 GB point cloud on CAD software can be very slow and requires a computer with high processing capabilities. But solutions do exist! This is the case with Snapsend, a software package developed by the startup, Snapkin. Snapsend automatically reduces the size of the point cloud by 90% with no loss of accuracy. Try it free for a week by registering on MySnapkin, and enjoy all the power of this tool in a trial version. 

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