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  • Writer's pictureVirve Juhola

As-built measurement of a mechanical room by laser scanning on site

Trimble X7 scanner is used on the construction site of Trimble’s new Finland offices to document as-built dimensions. This modern method supports space-efficient solutions and produces initial data for facility management and alterations.

Trimble X7 laser scanning device has been used on the construction site of the Oasis of Professionals business campus to document the as-built dimensions of an HVAC mechanicalt room and to compare them with the original MEP design.

“For a long time, redline markup has been the way to document as-built information if the design has changed during construction,” says Training and Support Manager Kari Immonen of Geotrim, the reseller of Trimble’s devices in Finland.

“By laser scanning, we are able to produce a point cloud of the installed structures and building services engineering and use it to produce an as-built model with which to compare the design with reality extremely accurately. This building information model is accurate because it repeats the conditions exactly like they are in reality. With redline markup, you can always adapt a bit, but this method is absolutely realistic.”

“A 3D object matched with a point cloud depicts the shape and dimensions of the object, including information about features, and thereby information about changes is forwarded to the designer to support the actual locations of the strcutures and documentation. This material is always available for comparision after the building has been commissioned and if any changes are made in the premises,” Immonen points out.

“The IFC model and the point cloud laser-scanned on site are opened in the Trimble RealWorks software and adjusted with the as-built geometric objects, in this case the cylinders and curves that depict the piping elements. The software includes tools to model other elements, too. By using the models it is easy to understand which parts of the space have changed compared to the design and where space has been saved, for example. The software is able to recognize different types of pipes and connections based on their shapes,” Immonen explains.

“For office buildings, the objective is to design as many round ventilation ducts as possible because they are off-the-shelf goods and therefore more affordable,” says HVAC engineer and design manager Henri Jurvelin of Ramboll.

“Square ducts are sometimes custom designed for tight spots to create a smarter solution. By using round ducts, AC equipment can be dimensioned to fit in less space. There is some variation is manufacturers’ dimensions, and a mechanical room is designed to keep the installation order despite a change in equipment size.”

“In this project, the selected equipment is a bit smaller than originally designed, and this can be seen in the laser scanning results,” Jurvelin says. “The idea is to model the objects taking into account the room for installation and maneuver, and in this location, we succeeded well with the mechanical rooms’ space reservations. Laser scanning was a sample of the method to replace redline markup in the future. The laser-scanned model shows all the profiles realistically and highlights changes reliably. When changes are made later, initial information includes the as-installed conditions. It is easier to schedule changes when the real-time status of the installations is updated in the model.

“The laser-scanned documentation is indeed very good initial information for future renovation projects,” says digital engineer at NCC Eero-Pekka Piipponen.

“Design and reality are shown in green and red respectively in the Trimble Connect software. This view is easy to study and share on the construction site, and the client, too, can see what they are getting in terms of design. This information can also be shared through Trimble RealWorks. From a builder’s point of view, its is interesting to utilize any data refined from a point cloud in as-built monitoring. The OOPS site was recentely visited by robot dog Spot with an X7 installed on its back, and by using a robot, we can obtain accurate as-built data automatically at the end of each work day to help with next day’s task planning. Once we have up-to-date data about installation locations, it is easier for the designer, too, to perceive the space and make design changes accordingly."

From the left: Immonen, Piipponen, Jurvelin

The most advanced laser-scanning technology in the world

“In practice, robot dog Spot is given the route check points and scanning points,” says Immonen. “Once the scanner is done, it sends a message to Spot who then continues to the next point. The point cloud is saved from the scanning station to the device memory and to the Trimble Connect cloud. Equipped with a scanner, the robot can scan any room and publish the results in the cloud, from where project management can obtain ready-to-use documentation for task planning.”

“Trimble X7 laser scanner attached on the robot dog Spot collects a point cloud from each stopover automatically,” Immonen explains. “Since the robot moves on all fours, it is of utmost importance to have built-in calibration in the scanner. Once the robot stops, the scanner performs internal calibration and collects a dome-shaped points cloud with the given parameters. The scanner indicates by blinking how each work phase is proceeding, and once the scanning is done, commands the robot to move on to the next place.”

“Trimble X7 is a highly advanced laser scanner with a special calibration feature,” Immonen continues. “With X7, Trimble has invested in the development of scanning methods instead of focusing on measuring speed. Digital photo mosaics bring in color in the point cloud and make further manipulation of the material easier. The device also includes inertia technology which makes the registration of the point cloud significantly faster. With Trimble Connect, the differences between the point cloud and the design can be compared browser-based without any dedicated software.”

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