BIMで紙の図面にサヨナラ！LRTKが実現するスマート施工革命

Large-format paper drawings spread across construction sites—until now they have been the centerpiece of construction management, but that norm is poised to change dramatically. The construction industry faces chronic labor shortages, rising infrastructure maintenance costs, and the need for rapid disaster response, making productivity improvements urgent. To break through these challenges, the Ministry of Land, Infrastructure, Transport and Tourism (MLIT) is promoting digitalization in construction through initiatives like “i-Construction” and construction DX (digital transformation), placing BIM at the core. In fact, BIM/CIM has been positioned by MLIT as the “engine of the productivity revolution,” and is being used to elevate every business process. Introducing BIM leads to reforms in on-site work styles as well as improvements in quality and safety, making its social significance considerable. Digital technologies for streamlining operations and reducing labor are now unavoidable, and BIM holds the key.

In line with this trend, from fiscal 2023 MLIT has made BIM/CIM use a principle for all directly managed design and construction projects (3D models are to be used unless there are special circumstances). Furthermore, full mandatory implementation of BIM/CIM for public works is scheduled for 2027, and BIM is already being introduced in projects totaling about ¥2.5 trillion annually. The construction industry is truly at a major turning point, and full-scale BIM adoption is imperative.

The spread of BIM is triggering a major shift from construction that relied on paper drawings to smart construction centered on digital data. This article unpacks what BIM is, its benefits, and on-site use cases, and explains next-generation construction methods that allow you to “say goodbye to paper drawings.” We also touch on LRTK, a high-precision positioning solution that links BIM and the field in real time, introducing the cutting edge of a smart construction revolution where anyone can perform high-precision surveying easily.

BIMとは何か？紙図面から3Dデータへの転換

BIM (Building Information Modeling) is a method that aggregates and utilizes project information into a digital 3D model. Though the concept developed in the building sector, it has been extended to civil infrastructure (CIM: Construction Information Modeling), and today it is commonly referred to as BIM across both architecture and civil engineering. The goal is to centrally manage and share 3D models and related information at every stage—from survey and design to construction and maintenance—to improve efficiency across the entire project.

A BIM model can store not only a 3D model that represents the shape, dimensions, and positional relationships of structures, but also attribute information such as material, strength, cost, and construction dates for each component, and reference information like drawings, photos, point cloud survey data, and reports. By digitally integrating information that used to be scattered across 2D drawings and paper documents, both clients and contractors can make effective use of the data, leading to productivity gains. Structural and dimensional relationships that were hard to grasp from paper drawings can be intuitively visualized with a 3D model, deepening common understanding among all stakeholders and reducing misalignments and communication errors. As a result, rework due to design mistakes and on-site corrections are reduced, contributing to improved quality and enhanced safety.

BIM is essentially the foundation of a digital twin—a virtual replica of real structures and sites. Advanced examples have emerged, such as building a “digital twin model” using BIM for projects like the reconstruction of Shuri Castle to facilitate information sharing among stakeholders. BIM is enabling the digitalization of real space at a scale that paper drawings could never achieve, allowing visualization and optimization of entire projects.

BIM活用によるメリット（合意形成・品質向上・省力化など）

• 3D visualization for consensus building and error reduction: Structures that are difficult to imagine from drawings can be intuitively understood with a 3D model. Sharing 3D models at local briefings or progress meetings helps all stakeholders form a common vision of the finished product, smoothing consensus building and decision making. Performing clash detection and other checks on the model during the design phase allows detection of design errors that drawings might miss, reducing rework during construction. Consequently, high-quality construction can be achieved with fewer people and shorter schedules, improving overall productivity.

• Progress sharing and improved safety: During construction, the 3D model created at the design stage can be used to simulate construction procedures and share them on site. Since all staff can visually grasp the finished form in advance, it becomes easier to organize tasks and improves safety management. For example, even with complex structures, verifying construction steps with 3D model animations helps inexperienced workers understand the workflow. In practice, many sites have found that using BIM models for sharing the finished image and confirming procedures is effective.

• Maintenance efficiency: BIM data is also powerful in the post-completion maintenance phase. Recording inspection results on a 3D model for bridge or tunnel inspections allows centralized management of crack locations and repair histories. If anomalies are marked on the model with linked coordinates, photos, and inspection dates, the same spots can be accurately identified in subsequent inspections, aiding deterioration monitoring and repair planning. Because a BIM model can hold comprehensive attribute information (dimensions, materials, construction date, management numbers, etc.), the traditional work of cross-referencing ledgers and drawings is no longer necessary, dramatically improving maintenance efficiency. This contributes to reduced life-cycle costs and extended infrastructure lifespans.

• Shorter schedules and cost reduction: As noted above, thorough consideration during the design phase (front-loading) and concurrent engineering make schedule shortening and cost reduction more attainable across the project. MLIT surveys show many BIM-adopting companies feel operational efficiencies, rapid consensus building, error reduction, and safety improvements—multi-faceted benefits are being confirmed. Only a very small portion of firms reported no noticeable benefits; in most sites BIM advantages are being realized.

BIMの活用事例：現場で進むデジタル施工

• Large-scale civil works (land development, roads, etc.): In land development, it has become common to overlay a 3D point cloud (scan data) of the initial ground acquired by drone survey with the designed finished-ground model to accurately grasp differences in excavation and fill volumes. This enhances accuracy control for the final shape and contributes to quality assurance. In road and tunnel works, automated generation of longitudinal and cross-sectional drawings from acquired terrain point clouds and comparison of the design model with as-built results for quality control are increasingly used. Introducing drone + CIM has enabled wide-area terrain understanding and instantaneous earthwork volume calculations that were previously difficult, greatly optimizing construction planning and progress management.

• Bridge sector: BIM is also used in bridge construction. 3D models of piers and girders are used to check for clashes with surrounding terrain and existing structures in advance, and to animate construction procedures for review. Recently, 3D technology has been applied to bridge maintenance as well: drones scan entire bridges to create detailed point cloud models for identifying and recording degradation. Inspections of underside of girders, which previously required work at height with specialized vehicles, can now detect fine cracks on point cloud data, making maintenance more efficient and comprehensive.

• ICT earthworks (smart construction): In ICT construction (so-called smart construction) promoted by MLIT, ICT technologies are introduced into surveying, design, and construction to advance civil engineering works. Specifically, 3D design data is loaded into construction equipment, and machine control (MC)/machine guidance (MG) enables automatic or semi-automatic operation of bulldozers and excavators for precise grading or excavation according to the design model. This allows non-expert operators to achieve consistent quality, and a single supervisor can remotely operate multiple machines. Using point clouds acquired by drones or 3D laser scanners to compare pre- and post-construction terrain changes for as-built management has become commonplace. In one site, drone surveys shortened surveying time to less than one-fifth of the conventional time and eliminated the need for work at height, improving safety. ICT construction is being promoted in tandem with BIM-based 3D data use and has become a core technology supporting construction DX.

From these examples it is clear that a productivity revolution at sites is being realized through the combination of BIM and cutting-edge technologies. Combining 3D models with drones and automated machinery can reduce surveying and construction management tasks that used to take days to mere hours, and enable precise work that was difficult by manual labor to be performed accurately and safely. In practice, the 3D models created with BIM themselves are becoming the digital instructions for construction sites, and measurement → design → construction → inspection processes are beginning to connect seamlessly. Data-driven smart construction is becoming the new standard.

データ連携で実現するペーパーレス施工管理

To make the most of BIM, it is important to closely link on-site data acquisition with design and construction processes. The true value of BIM is realized when surveying → design → construction → inspection are seamlessly connected by digital data rather than being fragmented.

Specifically, in the initial stage obtain detailed 3D survey data (point clouds and orthoimages) of the site by drone surveys or ground LiDAR, and integrate this as the base terrain and structure information for the design BIM model. The high-precision design 3D model thus created can be used directly as machine guidance data and construction management materials during construction. Moreover, conducting as-built surveys during construction allows current point cloud data and survey coordinates to be immediately reflected in the BIM model for visualizing and verifying progress. Linking this flow continuously with digital data enables paperless construction management without relying on paper drawings or manual information transmission.

A key point in data linkage is to use a common coordinate system and data formats so that “measured data can be used directly in the model, and model data can be used directly in the field.” MLIT also recommends adopting open data formats such as LandXML, J-LandXML, and IFC when applying BIM to public works. This allows surveying instruments, design CAD, and construction machines to handle the same data, reducing double entry and rework. For example, where workers used to read paper drawings on site and manually input coordinate values into surveying instruments, now they can simply load electronic data into the equipment. For as-built inspection after construction, overlaying the design model and measured point clouds to automatically display differences with color-coding makes it easy to identify areas requiring additional work at a glance.

Recent advances in cloud technology have further enabled real-time data sharing between sites and offices. For example, if surveyed point coordinates or photos are synced to the cloud on site, headquarters or designers can view the data immediately and provide instructions in real time. Previously there was a time lag—survey crew returning to the office to digitize drawings → reporting → review—but cloud linkage is making “measure, show, convey, and decide immediately” a reality. This accelerates overall site scheduling and contributes to shorter schedules and cost savings. Remote construction management where specialists monitor from far away is also becoming practical, reducing travel time and risky work and improving safety.

Thus, building an environment where surveying → design → construction → inspection data flow smoothly is the key to operational efficiency with BIM. Conversely, no matter how sophisticated the 3D model, its true value cannot be realized if data exchange with the field is fragmented. The next section focuses on LRTK, a technology that connects the field and models, and delves deeper into the specifics of smart construction.

LRTKとは何か：スマホで使える超高精度測位ツール

One foundational technology supporting advanced BIM use is positioning based on the RTK (real-time kinematic) method. RTK exchanges GNSS (satellite positioning) data received at both a base station and a rover via communication and cancels error factors to achieve centimeter-level positioning accuracy. While standard GPS positioning errors are around 5–10 m, RTK makes immediate high-precision surveying within a few centimeters possible. Since the 1990s RTK has gradually been applied to civil surveying and machine positioning, but traditional RTK survey equipment has been large, expensive, and required specialized knowledge. Fixed receivers and radio equipment had to be set up as a complete kit, often with two people carrying tripods to install them—making it a high hurdle for small contractors and local governments. Additionally, RTK struggled in areas with poor communications; in forests or urban canyons satellite signals are blocked and high accuracy is difficult to achieve.

A groundbreaking device that solves these issues and makes RTK surveying easy for anyone is LRTK (Local RTK). LRTK refers to a positioning solution centered on an ultra-compact RTK-GNSS receiver that can be attached to a smartphone or tablet. For example, the LRTK Phone is a product used by attaching it to an iPhone; the compact device weighs about 165 g and has a thickness of about 1 cm (0.4 in), and by simply sticking it to the back of your phone, your everyday smartphone instantly becomes a surveying instrument with centimeter-level accuracy (cm level accuracy (half-inch accuracy)). Tasks that used to require two people and a tripod can now be completed single-handedly with just a smartphone, ushering in a true “surveying with a smartphone” era.

Operating LRTK is highly intuitive. Launch the dedicated app and the device connects automatically; within seconds high-precision positioning begins. No complicated initial setup or special controller is required, and anyone familiar with using a smartphone can quickly get the hang of it. The interface lets you record desired points with touch input or guide you to a target point according to on-screen instructions—so it can feel like a game and requires little training. This is a major advancement compared to traditional surveying equipment that only trained technicians could operate.

LRTK leverages state-of-the-art hardware and software. The device contains an internal battery that operates for about 6 hours and can be powered by an external mobile battery for extended use. For communication-limited areas, such as mountainous regions where cellular reception is poor, it can directly receive the centimeter-class augmentation service (CLAS) provided by Japan’s Quasi-Zenith Satellite System Michibiki (QZSS) and apply corrections, enabling centimeter-class positioning even outside cellular coverage; when within coverage it also supports network RTK via the Internet. This significantly improves on conventional RTK equipment that required Internet connectivity.

The biggest feature is the wide range of functions enabled by leveraging the smartphone platform. The LRTK app integrates with built-in LiDAR sensors and cameras to enable high-precision 3D scanning on site. Point cloud data acquired on the spot are automatically tagged with global geodetic coordinates, eliminating the post-scan alignment that used to be necessary. You can also AR-display the design 3D model over the smartphone camera view to overlay the model on real scenery without offset. The positioned photo feature automatically tags site photos with precise latitude/longitude of the shooting location and camera heading (bearing), making it easy to locate the exact same crack or repair spot later. Other functions include “coordinate navigation” (guide to stakeout positions) that navigates to specified coordinates with an on-screen arrow, and tools to measure length and volume on acquired point clouds—tasks that previously required multiple specialized devices and software are now all-in-one with LRTK + smartphone. It is astonishing to achieve this level of capability without expensive specialized equipment, and it has the potential to be used by anyone on site.

In short, LRTK is a ultra-high-precision GNSS positioning device usable with a smartphone. This dramatically simplifies surveying tasks on site and enables smart construction that links BIM models and the field in real time.

LRTKが実現するスマート施工革命

Introducing LRTK to a site changes how construction management and surveying are performed. The key point is that it can directly link the digital BIM model with the real site.

With LRTK, you can reference the 3D model created at the design stage directly on site during construction. By AR-projecting the design model onto the actual scene via a smartphone screen, you can share on-the-spot the finished image that was hard to understand with paper drawings, intuitively grasping “what is being built here.” Because all stakeholders can view the same finished image simultaneously, recognition gaps are reduced and communication smooths. AR guidance allows accurate placement of structures at specified positions and heights and pinpoints stake positions, drastically streamlining layout (staking) work and reducing human error. In one site, using LRTK’s AR navigation for staking reduced a half-day task to a short period and dramatically reduced mistakes. By linking the digital model to real space, LRTK can directly provide on-site guidance like “construct this here exactly as shown.”

Feedback from the field to the digital model also occurs in real time. Coordinates of measured points and acquired point clouds from LRTK can be shared immediately via the cloud, so the latest on-site measurements are instantly incorporated into the BIM model and can be reviewed and analyzed at the office. For example, scanning the post-excavation terrain with LRTK and comparing it to the design model allows immediate validation of as-built conditions on the model and quick judgment on excesses or deficits. Previously, earthwork volume calculations and as-built checks required taking survey data back to the office; now quantities and evaluations can be performed on site. On the LRTK cloud, shared point cloud data can automatically generate cross sections, and stakeholders can be given a URL to view 3D models in a browser. Even without specialized software, results can be reviewed, making site-office information linkage dramatically smoother and enabling real-time construction management: “measure, show, convey, and make the next decision.”

Because LRTK combines GNSS positioning with smartphone sensor technology, it supports seamless positioning both outdoors and indoors, further promoting smart construction. Other GNSS devices lose positioning when satellite signals are interrupted, but LRTK supplements this with iPhone AR technology—estimating and maintaining position for short periods under bridges or in forests so that positioning can continue. Even where satellites cannot be received at all, camera imagery and inertial sensors can maintain position, filling the gaps in surveying such as “tunnel interiors cannot be measured until exiting,” and making it a tool that can measure anywhere in a practical sense. This feature is effective for tunnel construction, indoor work, and urban surveys.

By introducing LRTK on site, BIM models and the field link bidirectionally in real time, making surveying and construction management smart. Presenting high-precision digital models on site to eliminate mistakes and immediately measuring as-built conditions to update models keeps data current and consistent throughout construction. This is the ideal of smart construction, and LRTK makes it a reality.

さらなる展望：BIMが拓く建設DXの未来

Digital transformation (DX) in construction will likely accelerate further. In the context of infrastructure DX, BIM will serve as the core that integrates IoT, AI, and robotics, leading to more advanced integration of design, construction, and maintenance processes. Building a constant “digital twin” of the site for real-time monitoring and control of construction is also within sight.

Several advanced examples of automation and labor reduction are already appearing. In building construction, painting robots for interior finishing and rebar-assembly robots for automatic reinforcement assembly are being commercialized, reporting 30–50% reductions in work time. In civil engineering, automated control and remote operation of heavy machinery are spreading, and attempts are increasing where one operator oversees multiple machines. Stable quality can be ensured without relying on experienced operators’ intuition, enabling newcomers to perform at a consistent level and reducing the burden of training. Autonomous patrol robots and AI surveillance cameras for site rounds are beginning to enable unmanned night security and real-time safety checks of the work environment. Drones have become indispensable for surveying and progress management, with aerial photos automatically generating 3D models to compute volumes and distances or monitor progress at fixed points. Drone adoption has eliminated the need for scaffolding-based high-altitude surveys in some cases, improving safety and reducing work time substantially (to less than one-fifth in some examples).

The essence of labor reduction is automating and assisting tasks previously done by humans with digital technology. This does not merely reduce headcount; machines take on precision and dangerous tasks that humans struggle with, allowing people to focus on more creative work. Introducing labor-saving technologies is expected to deliver social benefits in productivity, safety, and quality management.

The future of BIM and smart construction envisions fully feedback-controlled construction based on data—autonomously progressing work while continuously visualizing the site digitally. AI-based automatic terrain recognition, automatic generation of 3D models from point clouds, and high-speed cloud communications for remote collaborative work will advance, further improving operational convenience and efficiency. MLIT’s “i-Construction 2.0” advocates automation at construction sites, aiming for radical labor reduction such as one person controlling multiple machines and automating from design to construction. In the future, one site manager might monitor and control multiple robots and heavy machines, concentrating human effort on critical judgments and creative tasks.

A prerequisite for this future is the availability of highly accurate digital data. No matter how advanced AI and robots become, they cannot operate correctly without accurate base drawings and survey data. Therefore, the fusion of BIM models and on-site measurement technology is crucial, and easy high-precision positioning tools like LRTK will play an important role. If an environment where “anyone can measure accurately” is established, digital management can pervade every corner of a site and maximize the effect of DX. The spread of smartphone surveying with LRTK could be a solution to chronic technician shortages: intuitive operation lowers training costs, and newcomers can handle tasks quickly without relying on veterans, alleviating issues of skill succession. In this way, easy high-precision positioning provided by LRTK strongly supports MLIT-promoted initiatives like i-Construction and construction DX. Smartphone-based surveying methods are expected to continue expanding, transforming surveying, construction practices, and on-site workstyles.

結び：LRTKで誰でも簡単測量を体感しよう

We hope you can sense the value LRTK brings to sites amid the BIM and smart construction trends. Finally, let’s review the basic steps showing how simple smartphone surveying with LRTK is.

• Setup: Attach the LRTK device to the back of your smartphone (e.g., iPhone) and launch the dedicated app. There is one-time user registration, but once connection settings are completed, subsequent launches automatically connect to the device and positioning starts within seconds.

• Prepare for positioning: The app captures satellites and begins receiving correction information. After about 30 seconds a fixed solution (Fix) stabilizes and the screen shows a high-precision mode status such as “measurements available with centimeter-level accuracy (cm level accuracy (half-inch accuracy)).” You are then ready to survey.

• Measure points: At the point you want to measure, hold the smartphone steady and tap the app’s “point positioning” button. Averaged coordinates calculated from a few seconds of observation produce high-precision latitude, longitude, and height displayed on the screen. Enter a point name or notes as needed and save to complete the record. It’s truly one tap to obtain an accurate position.

• Photo recording (optional): To document site conditions with photos, use “positioned photo” mode. Each photo file is automatically tagged with high-precision latitude/longitude and camera bearing, allowing exact location confirmation later against cloud maps and aiding report creation and temporal comparisons.

• Stakeout and guidance (optional): For staking to coordinates specified in drawings, use the “coordinate navigation” function. Enter the target coordinates and an on-screen arrow indicates the direction to move while distance updates in real time. Follow the guidance and when the arrow turns green you’ve reached the target. Placing a stake or marking completes the layout to drawing specifications. Even without surveying expertise, anyone can reach designated points without confusion, making work very smooth.

• Data sharing: After surveying, press the app’s “sync” button to upload data to the cloud. Measured coordinates, photos, and point clouds are saved to the cloud and can be immediately reviewed from an office PC. Issuing a sharing URL lets stakeholders view 3D data in a browser, measuring distances and areas. This realizes a one-stop flow: measure on site, instantly share accurate results, and apply them to follow-up tasks.

With LRTK, centimeter-precision surveying that once relied on skilled technicians becomes possible through remarkably simple steps. An era has arrived where anyone with a smartphone can perform surveying with cm level accuracy (half-inch accuracy). LRTK’s combination of ease and precision makes it a very powerful tool for advancing BIM-based smart construction. Try LRTK surveying on your next site visit—you’ll likely experience efficiency and peace of mind that overturn previous conventions. Embrace the new form of construction enabled by LRTK and take your site to the next stage.