Taisei Corporation, one of Japan's leading general construction companies, is promoting the use of 3D laser scanning and 3D data utilization through its headquarters' Architectural Department Digital Product Center. In the extensive renovation project of the Sonic City Hall building completed in September 2022, they utilized the Leica Geosystems' imaging laser scanner Leica BLK360 G1 to conduct 3D laser scanning to quickly and accurately understand the shape of the spiral staircase section. They completed the high-precision grasping of the spatial shape composed of complex curves in just "half a day with two people," achieving significant results such as improving construction drawing accuracy and advancing the start date of construction. In the future, they plan to expand the nationwide deployment of 3D data utilization bases, such as by training personnel capable of 3D laser scanning tasks at the branch level, in order to further enhance the productivity improvement effects at work sites.
Renovation projects start with "an accurate grasping of the current condition shape."
A 3-minute walk from JR Omiya Station, Sonic City is a comprehensive convention facility consisting of three parts: Hall building, Office building, and Hotel building. At the time of its completion in 1988, the Office building attracted attention as the tallest building in Saitama Prefecture.
After more than 30 years since its construction, the Hall building required updates to its core facility equipment and renovations to the ceiling structure to enhance safety. As a result, it was necessary to suspend operations from 2021 to 2022 and conduct extensive renovation work.
The extensive renovation of the Sonic City Hall building involved a total of 12 specialized companies undertaking various tasks such as electrical, HVAC, sanitation, machinery, and exterior wall works. Taisei Corporation was responsible for the internal renovations related to construction.
In addition to the renovation of the ceiling and seating in the main hall and the ceiling and seating in the small hall, we decided to install additional handrails and indirect lighting on the spiral staircase that runs through the hall building. If it were a new building, we would be able to build it exactly according to the drawings, but in order to install the same looking exterior handrail while maintaining the existing walls and interior handrail, it is essential to first understand the current shape as accurately as possible," explained Toshiyuki Wada, Manager of the Sonic City Hall Building Major Renovation Work Station (hereinafter "Work Station"), Kanto Branch, Taisei Corporation. Toshiyuki Wada, Manager of the Kanto Branch Office's Sonic City Hall Building Large-Scale Renovation Work Station (hereinafter referred to as the "Work Station"), Taisei Corporation, explains.
The spiral staircase has a complicated design, with the elliptical shape gradually broken up, and the landings on each floor are also slightly different in shape. Although drawings were available, it was more than 30 years ago, when even 2DCAD was not widely used, and after only one measurement, it was found to be inconsistent with the real thing. Therefore, it was decided that measuring the existing conditions was essential in order to create a handrail and indirect lighting to match the irregularly curved staircase walls.
At the end of January 2022, the work site requested in-house measurements of the existing conditions from the Digital Product Center of the Building Division at TAISEI's headquarters. The Digital Product Center made a preliminary inspection of the site and immediately decided on a 3D laser scan using the latest equipment. The Leica BLK360 G1 imaging laser scanner (BLK360) from Leica Geosystems was used to take measurements in early February.
When completed in 1988, Sonic City received the "BCS Award" for outstanding architectural works in Japan from the Japan Federation of Construction Contractors Associations. The hall building has a large hall that can accommodate 2,500 people, as well as a small hall and international conference rooms.
The work is fast and the quality deliverables are high.
3D Laser Scanning
There are many projects where the drawings do not match the actual building. These renovation projects require a lot of time and effort to survey the existing conditions first, which delays the timing for establishing a reliable construction plan," said Daisuke Naganuma, Manager of the Facilities & Renewal BIM Office, Digital Product Center, Building Division, Taisei Corporation.
Conventional measurements using total stations, tape measures, and laser rangefinders require too much manpower and time. Moreover, if there is ceiling measurement, scaffolding and safety equipment must be set up and removed, and working at height is hazardous.
To overcome these challenges, the Digital Product Center turned its attention early on to 3D laser scanning.
3D laser scanning is fast. The data obtained by 3D laser scanning has a large amount of information, The data obtained from 3D laser scanning is of high quality in the sense that it can be linked to BIM/CIM software, which can be expected to accelerate construction DX.
With these goals in mind, BLK360 was introduced in April 2019. The company highly valued BLK360's unique features: lightweight, fast, tablet PC integration, good software, and reasonable price.
Existing buildings in urban areas are located in places with good access to transportation, so the majority of the time we go to the site by train, so we focused on the feature of being easy to carry around. Also, if it is compact and lightweight, we can take more and more measurements even in cramped small rooms or in the back of ceilings where many devices are placed," says Tomoyuki Sakaki, Assistant Manager of the Facilities and Renewal BIM Office, Digital Product Center. The evaluation of 'fast' includes two elements: the unprecedented measurement speed of approximately three minutes per scan, and the ability to reduce the total number of measurement days, for example, from three days to three hours," he adds.
Another feature of the BLK360 is its ability to work with tablet PCs; at the time of the 2019 study, the Leica Geosystems product was the only 3D scanner that could be controlled by a tablet PC.
The time required for one scan is about three minutes, which is the time required not only to acquire point cloud data but also to complete streaming the data to the iPad Pro. Thanks to this speed and ease of use, it has become commonplace for us to work while viewing and checking the iPad Pro screen at the measurement site," said Yuji Suzuki, Senior Manager of the Facilities and Renewal BIM Office, Digital Product Center. We no longer have to worry about finding out that we didn't get a good shade on a pillar after we return to the office.
The software is also well developed. For example, the high accuracy of merging point cloud data reduces post-processing time. The menu display is also in Japanese, making it easy to familiarize yourself with the software.
An even more important point is that Leica Geosystems' software alone can import data into CAD and BIM/CIM software without the need for specialized point cloud software from other companies. If we can complete the process with one company, including both hardware and software, data linkage becomes simpler and support is more reliable," Sakaki points out.
Mr. Naganuma added, "Autodesk and Leica Geosystems' headquarters are strengthening their collaboration through technical cooperation and business alliances on various projects. We also appreciate that this will lead to reliable data collaboration in the future," he added.
The point cloud data and panoramic image were combined to reproduce the overall shape of an eight-level spiral staircase. Displayed with Leica TruView point cloud data management software
BLK360 inverted measurement for spiral staircase measurement
The spiral staircase in the Sonic City Hall building is connected to a total of eight levels from the second basement to the top floor of the Main Hall by a stairwell. Rather than taking the dimensions of the staircase and walls, it was necessary to grasp the shape of the entire high columnar space with an area of approximately 50 ㎡.
The measurement members set up targets on the reference ink marks on the staircase landings and acquired point cloud data with BLK360. A total of 34 machine points were scanned on 8 floors. The field work was completed in "half a day by two people.
The BLK360 was also very powerful in measuring the inner circumference of the spiral staircase.
In this area, the inner railings form a triangular shape and are connected vertically. With a total station, the sharp corners of the triangle are shaded and difficult to measure. However, when BLK360 was suspended from the railing using a hanging clamp to perform inverted measurement, point cloud data for two floors could be acquired with a single scan, which was extremely efficient.
I like the inverted measurement function so much that I often use it on other sites as well. For example, when I want to get an accurate 3D view of the boundary between the outside wall of a building and the ground, I hang the BLK360 and take an inverted measurement," said Sakaki.
For the inner perimeter of the spiral staircase, BLK360 was suspended from the handrail using a bracket (clamp) to conduct inverted measurements. Even in areas prone to shadows, such as the acute angles of triangles, point cloud data was accurately captured.
By acquiring and synthesizing point cloud data in this manner, various applications become possible. In this case, we converted the data into ortho images and added coordinates, as well as overlaid them with existing drawings.
Ortho images are a commonly used technique in post-processing aerial photographs. Aerial photographs inevitably contain portions captured from directly above and portions captured from oblique angles, causing subtle distortions in dimensions and positions in the oblique parts. Ortho transformation (orthorectification) eliminates the positional discrepancies in the image, resulting in an image where all parts are displayed with correct sizes and positions as seen from directly above, similar to a map.
By converting point cloud data into ortho images, we can obtain current images that accurately represent the correct size and position. When overlaid with existing drawings, any discrepancies between the drawings and the actual conditions can be accurately displayed for anyone to see at a glance.
Simply acquiring point cloud data through 3D laser scanning doesn't automatically guarantee improved quality and solve all problems. The ability to easily generate ortho images for sharing the measured information among stakeholders holds significant importance," emphasized Mr. Nagasuna. While point cloud data can be compared with drawings, it is often bulky and difficult to handle without a high-spec PC. Converting it into ortho images compresses the data, making it easier to manage.
Mr. Wada stated, "We had the point cloud data converted into ortho images and delivered internally, allowing all personnel at the project site to utilize them according to their respective roles."
He further explained, "We were able to conduct meetings while viewing the images, create 2D CAD data by tracing the ortho images, and promptly prepare documents for discussions with collaborating contractors responsible for installing handrails and indirect lighting. As a result, construction drawings were produced more quickly than usual, allowing us to advance the start date of the construction project."
The measured point cloud data typically follows a standard workflow, where it is imported from the point cloud processing software 「Cyclone REGISTER 360」into the CAD plugin「Leica CloudWorx」From there, various data such as 2D drawings and 3D models are generated and utilized in CAD or BIM/CIM software. However, in this case, as there was no need to create a BIM model, only ortho image generation using Cyclone REGISTER 360 was performed, and Leica CloudWorx was not used. Additionally, for viewing and real-time sharing of point cloud data, the Digital Product Center utilizes the point cloud data sharing software「Leica TruView」.
In this way, all tasks are completed using only Leica Geosystems' hardware and software, making operations straightforward and easy to understand. Additionally, data export/import processes are smooth due to the compatibility within the Leica Geosystems ecosystem.
In Cyclone REGISTER 360, the point cloud data was converted into ortho images. After adding coordinate information, floor plans were created in AutoCAD.
In this project, the size of the ortho image files was compressed to a level that could be handled even by standard-spec PCs. These compressed ortho images were then overlaid with existing drawings. After clearly identifying the discrepancies, each individual creatively crafted PowerPoint documents and other materials to effectively communicate the information.
Smooth surfaces were accurately captured with high precision in just "half a day with two people" of work.
The extensive renovation project of the Sonic City Hall building was completed in September 2022. The construction process for the spiral staircase section, which was the first step of the project involving "current condition assessment," saw a significant change in workflow with the adoption of 3D laser scanning using the BLK360.
Firstly, the time required for current condition assessment was significantly reduced.
"Unlike total stations, it's a whole different ball game. The speed difference is overwhelming, it's just night and day," Mr. Wada emphasized. "With total stations, increasing the accuracy of curved surfaces requires continually adding more measurement points. To grasp the 'complex smoothness' of those staircase walls, it would have taken at least a week, wouldn't you agree? With 3D laser scanning, it was done in an instant, or rather, in just three minutes," he said with a smile.
At the workshop, conventionally, CAD drawings were created by inputting measurements from total station surveys.
However, it was challenging to improve accuracy for irregular complex curves or ellipses that changed in shape. In this project, using point cloud data from orthoimages increased the precision of construction drawings and enhanced the accuracy of handrail and indirect lighting installation work.
In recent years, clients (owners) and design firms have also been actively engaged in Construction DX (Digital Transformation). In the performance evaluation of the Sonic City Hall construction project, the client, Saitama Prefecture, showed keen interest in the process from 3D laser scanning to construction drawing creation and appreciated the innovative approaches implemented throughout the project.
For existing buildings, the speed of current condition surveys is crucial.
The Digital Product Center has been using the BLK360 for three years now. While there was a lot of experimentation in the first year, the frequency of use has increased recently, and the cumulative scan count has reached 4,000 scans.
"When you get used to it, we're naturally taking around 70 machine points per day. It's almost a 'second-by-second' operation," says Mr. Naganuma. That's an impressive speed.
The context is, for example, a specific ceiling work to enhance seismic resistance by installing steel frames in the suspended ceilings of halls. The accurately designed curves, calculated for acoustic effects and such, must be maintained precisely. Therefore, it is necessary to accurately measure the current curvature of the suspended ceiling while keeping it in place.
Traditional architecture, especially shrines and temples, often have a high probability of inconsistency between the current state and the drawings. Moreover, since it's not permissible to touch the actual structures, 3D laser scanning plays a crucial role.
It's not uncommon to use 3D laser scanning not only for measuring the interior of buildings but also for surveying exteriors and planning earthworks.
BLK360 proved useful in surveys to calculate the amount of soil to be brought in to create slopes within the site, as well as the amount of soil to be removed. When planning road reinforcement or widening to access construction sites, scanning the surrounding roads with 3D laser scanning can be effective, especially if the roads are narrow or steep.
There have been instances where specialist contractors, coincidentally equipped with both BLK360 and its higher-end model, the Leica RTC360, collaborated on measurements. By sharing targets and dividing tasks to survey the interior, rooftop, and exterior of buildings, they were able to efficiently survey a wide area in a short amount of time.
Focusing so much on "speed" isn't just about efficiency and productivity.
"Shortening the time is a very important requirement. When it comes to surveying existing buildings, there's often a need to complete on-site work quickly and efficiently, whether it's while the client is present or to avoid interrupting concurrent construction projects," Mr. Naganuma explains. "When we surveyed a station building, for example, we used BLK360 to ensure accurate measurements in a short amount of time without disrupting pedestrian traffic."
Expanding the productivity-enhancing effects of 3D laser scanning to all of our nationwide workplaces.
The Digital Product Center, where the power of 3D laser scanning becomes more apparent with each use, is considering the introduction of other products in addition to the BLK360 currently in possession. By combining these products, they aim to generate even more innovative effects.
The leading product currently under consideration for introduction is the newly released 「Leica BLK360 G2」from the BLK360 series.
"BLK360 G1 has become smaller, faster, and more accurate. This is something we want to use," Mr. Sakaki emphasizes.
Mr. Sakaki is also paying attention to the RTC360, the higher-end model of the BLK360. This is because it offers a high scan density and a maximum measurement distance of over 130 meters, more than double that of the BLK360. "For architectural designs and traditional buildings designed by architects, I would like to use the RTC360 for measurement," says Mr. Sakaki.
The handheld laser scanner「Leica BLK2GO」is currently under testing. It allows measurement while moving manually, so there are expectations that it can further enhance "measurement without stopping the site."
In terms of software, we are paying close attention to the all-in-one point cloud utilization solution 「Leica Cyclone 3DR」. This time, we created 2D CAD data by tracing orthographed images at the workshop, but it seems like a more efficient method can be used with the Leica Cyclone 3DR.
“I had some knowledge of what 3D laser scanning was, but when I actually used it, the effects were even greater than I had imagined, so this project was really meaningful. I want to spread this awareness to all of our employees. ``When renovating an existing building, I want to make 3D laser scanning the first process'' the standard,'' Mr. Wada says enthusiastically.
As a digital product center, we have just begun various plans and initiatives, such as training key personnel capable of 3D laser scanning at branches and on-site.
"We want to create a system where not only people within the company, but also specialists and partner companies who already own Leica products, can unite their efforts.
The important thing is to develop the system in a way that greatly improves productivity at work sites across the country," says Naganuma.
Weighing only 1 kg, the compact BLK360 has great potential to transform the work processes of large general contractors and even promote collaboration beyond corporate walls.
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