Case study
Achieving speed and sustainability with Leica iCON solutions
Headquartered in Kobe, Japan, Prex Co., Ltd. (Prex) is dedicated to low-cost, fast construction and environmentally friendly housing. To that end, the company developed a unique precast foundation that reduces foundation installation to just two hours.
Chieko Yasukawa
Marketing manager for Leica Geosystems, part of Hexagon, in Japan.
The Leica iCR70 robotic total station and Leica iCON build software for construction are integral components of the high-precision process that enables Prex to achieve remarkably short construction times: only three days from the start of construction to topping out of the building and total projects completed in less than 30 days.
Prex is dedicated to attaining the Sustainable Development Goals. For instance, they provide houses that achieve zero carbon dioxide emissions throughout their lifecycle. They also build compact, inexpensive accommodations, and even off-grid housing that includes solar power generation and storage batteries for self-sufficiency.
With its innovations, Prex responds to pressing societal challenges. Due to Japan’s declining population, a decrease in working-age individuals has led to labour shortages in the construction industry. Simultaneously, there’s a need for more accessible and sustainable housing, particularly for families. Prex’s precast foundations, developed to address these issues, can be constructed quickly with fewer workers at a low cost.
“Until now, building a foundation for a house required the skills of craftsmen, for earth workers, rebar and formwork stages, and the construction period took about two weeks,” explains Prex’s Chairman, Shogo Arai. “However, with our originally developed precast foundation, it can be installed in just two hours without the need for specialists on site.”
The precast foundation developed by the company in 2019 is made in a factory and features high strength and quality, fabricated to millimetre precision. The precast foundation has a lifespan of about 150 years and can be used repeatedly. For a building of about 70 square metres, the foundation work can be completed simply by installing the precast foundation at the four corners of the building and then stacking the factory-produced housing materials.
HIGH ACCURACY AND EASY OPERATION WITH A ROBOTIC TOTAL STATION
All layout work must accurately meet the design tolerances to ensure a perfect fit. For this reason, Prex carefully selected the construction equipment used for marking out sites. “The position of the precast foundation and the bolts installed in the foundation affect the accuracy of the entire house, so high accuracy within a tolerance of one millimetre is often required,” says Arai. To achieve this high accuracy, Prex chose the Leica iCON iCR70 robotic total station with iCON build software — both designed especially for construction.
“We tested and compared many different types of total stations,” reflects Arai on Prex’s decision to invest in the iCR70. “The iCR70 is very accurate, and even when a vehicle or worker crosses the road during the layout process, and the total station loses sight of the prism, it recovers quickly. Our working environment is very dynamic, and therefore, we had to evaluate the ability of the total station to quickly recover from possible line-of-sight interruptions, keeping downtime to a minimum. We are very pleased with the performance of the iCR70 in this regard.”
“We also chose the iCR70 because it can be used both with and without a prism. We can use a prism when we need one mm level accuracy and continue working efficiently with a nonreflective target when it is difficult to use a prism,” says Arai. Both local grid and national coordinate systems are available for marking out coordinates, allowing for flexibility in choosing the most appropriate system based on the scale and purpose of the site. The iCR70 also allows a single person to perform layout work, which was important for Prex’s goal of fast and inexpensive construction. Arai explains, “Before, we used to measure the distance between precast foundations with a measuring tape and check the height with a level, which required two or three workers to layout. However, with the iCR70, we only need one person to do the layout.”
SMOOTH GUIDANCE WITH CONSTRUCTION-TAILORED SOFTWARE
Prex also uses Leica iCON build construction software on the Leica iCON CC80 controller tablet to digitise and streamline the layout process. Working with a 3D model of the building created in AutoCAD and saved in DXF format, the first step is to load the DXF file and the points to be laid out into the field controller. The screen will then display a 3D model of the foundation, other building parts, the points to be laid out and the current position.
iCON build provides easy-to-follow navigation to the desired point, so anyone can reach points quickly without making mistakes. Additionally, with the CC80’s 7-inch touchscreen, Prex crews can easily see the layout points and navigation even in direct sunlight. With clear visuals and intuitive features, one-person layout is easily and quickly completed, allowing the rest of the installation process to proceed.
