Rescue Mission: Using reality capture to plan the re-development of a former convent
Author: André Azevedo
Next to the Carmo Church in Braga, Portugal, sits a former Carmelite Convent founded in 1653. No longer occupied and in need of significant repair, the convent compound was acquired by property developer and renovation experts, Fortera.
To decide on the best way to sympathetically develop the complex site, which includes vaults, attics, and water features, Fortera asked civil engineering company Buildgest to carry out a complete geometric survey. To capture the data needed to build a BIM model, André Azevedo, technical manager at Buildgest used a Leica Geosystems 3D laser scanning solution.
Visualising the environment as it is in 3D
The convent has a complicated interior and exterior made up of multiple buildings, levels and outdoor space. Before Buildgest was appointed, Fortera had already commissioned a 2D survey. Unfortunately, this didn’t capture sufficient detail for them to move into the design phase of the development confidently. Azevedo explains, “The classic 2D survey has some flaws, so we proposed a laser scanning survey and an accurate architectural model for the building. This Building Information Model (BIM) will help the client´s architect team to study different intervention scenarios.”
Faster scanning in the field with a streamlined reality capture solution
With a potential construction area of 5,000 square metres, complex geometry and a six-week deadline, Buildgest needed to carry out their fieldwork quickly. If they took too long, their modelling team would not have enough time to complete the work.
Already a Leica Geosystems users, Azevedo chose the Leica BLK360 imaging laser scanner, Cyclone REGISTER 360, Cyclone FIELD 360, 3DReshaper (Cyclone 3DR) and JetStream Viewer software elements.
“We needed equipment that can produce interior scanning quickly and accurately. The scanner is small and light compared to other equipment and that facilitated transportation to difficult zones of the buildings like attics and caves. The workflow between the products and software is smooth and quick. For example, Cyclone FIELD 360 pre-registers the scans automatically. That gives us faster scanning in the field,” explains Azevedo.
600 scans in seven days
Azevedo and his team used two BLK360 scanners in parallel for seven days to scan the convent buildings. The BLK360 - the smallest and lightest imaging laser scanner of its kind - captured the site with full-colour panoramic images overlaid on a high-accuracy point cloud. To make sure that the overall point cloud was accurate, Buildgest established a survey control network with laser scan targets around the building and in the interior.
A total of 600 detailed scans were taken. To improve efficiency, Azevedo used the Cyclone FIELD 360 mobile-device app to pre-register the point cloud while still on site. In his words, “Pre-registration of the collected information in the field saved time in post-processing tasks.”
Easy synchronisation, interoperability and processing
Back in the office, the Buildgest team used Cyclone REGISTER 360 to clean and register the scans, creating a unified point cloud. Azevedo says, “The synchronisation between Cyclone FIELD and Cyclone REGISTER is good and makes it easy to use.”
Processing included giving some shapes more definition. “Ornamental details, like the central water fountain that lies on the internal patio was modelled with the help of 3DReshaper,” Azevedo explains. The data was then processed further by a team of two modellers over a period of five weeks to create a complete architectural BIM model for the client. Azevedo explains the value of accurate scan data to this process, “Modelling the existing vaults of the convent was challenging and the use of point cloud helped us to have a complete understanding of the geometry of these elements.”
“It's helpful to review the model with the photographic record”
When the geometric survey was complete, Buildgest presented their findings to Fortera. As well as delivering the BIM model, and an LGS file of the data, Buildgest used a Cyclone Publisher Pro and JetStream Viewer to show the client how to explore and move the point cloud. They see this as the best way to communicate the results.
“We always recommend the JetStream Viewer to our clients, because it's more specific and helpful to review the model with the photographic record. Using the viewer, the client was able to see the 360 images that were captured in the scanning process. Besides, it gives them the option to navigate through the point cloud with a simple intuitive tool,” Explains Azevedo. JetStream Viewer Portable is a free, no-install version designed for easy visualisation, to let those without survey training experience point cloud data.
Buildgest was able to complete the project quickly without compromising on quality. Pedro Ferreira, chief engineer at Fortera, says, “Fortera was truly satisfied with the amount and quality of information that was delivered.” Now it’s over to the developer’s architects to plan a reinvention of the buildings, adding another chapter to the convent’s 350-year story.