What Is AR Construction Verification in the Era of 3D Construction? Experience the Future of Site Management with LRTK

Introduction: On-site challenges in construction verification and the transition to the era of 3D construction

On construction and civil engineering sites, construction verification tasks have until now relied heavily on manual labor and experience. The conventional methods—repeatedly surveying with drawings in hand and relying on experienced workers' "intuition" to ensure quality—face numerous issues such as labor shortages and human error. In fact, Japan's construction industry is confronting a decline in the workforce due to an aging and shrinking population and the 3K problem of "kitsui, kitanai, kiken" (hard, dirty, dangerous), making productivity improvement a major theme. Against this backdrop, the Ministry of Land, Infrastructure, Transport and Tourism launched i-Construction in 2016, aiming to improve productivity at construction sites by 20% by fiscal 2025 through the use of ICT technologies and three-dimensional data.

These policies have also helped spur the rapid spread of construction methods based on three-dimensional data, also called 3D construction. The practice of consistently utilizing 3D design models represented by BIM/CIM from construction through to operation and maintenance has become established, and with BIM/CIM application being made the default for directly managed projects from fiscal 2023 onward, an era in which the use of 3D data in every project is commonplace has arrived. Because designers, contractors, and clients can now reference a shared 3D model, misreadings of drawings and failures to convey design intent are prevented, enabling quicker consensus building. The industry is truly undergoing a shift to the "3D construction era".

So, in this era of 3D construction, how will the crucial on-site construction verification evolve? Rather than relying on 2D drawings and visual estimation as before, a new approach that leverages AR (augmented reality) technology is attracting attention. This article explains what AR construction verification is, its core technologies and on-site applications, the benefits it can deliver, and the challenges of implementation. Let’s look at the real picture of the latest technologies that will support the future of construction management.

What is AR construction verification? Relationship with 3D construction and basic technologies

AR construction verification is a method of holding a smartphone or tablet on-site and overlaying 3D design data and construction information onto the real-world view seen through the camera to check the state of construction. In short, rather than paper drawings or 2D photos, it projects a digital 3D model onto the actual object on site so you can intuitively understand “what should be built here and how” and “whether the finished work matches the design.” This AR-based construction verification serves as a bridge to maximize on-site use of BIM/CIM and other data, which have become more prevalent in the era of 3D construction.

For example, if you display the finished 3D model in AR on-site for a structure under construction, you can verify construction accuracy by directly comparing the physical structure with the virtual model. Even aspects that were previously left to the imagination based on plans or cross-sections become immediately obvious with AR because a three-dimensional design model appears in the real scene. Elements such as rebar spacing and the positions of buried pipes, which were difficult to inspect using only the naked eye or a tape measure, can also be checked against the digital model to prevent oversights.

Basic technologies for realizing AR construction verification are positioning technologies that determine a device’s position and orientation with high accuracy, and alignment technologies that match a digital model to real space. Using built-in sensors in smartphones and tablets (cameras, gyros, LiDAR, etc.) and AR apps, it is possible to overlay virtual objects onto the real world itself, but placing models accurately to within several centimeters (a few inches) requires special measures. Traditionally, cumbersome initial calibration was required, such as placing markers (reference marks) on-site for camera recognition or having an operator manually position the model to reference points. However, recently systems have emerged that combine RTK-GNSS (high-precision GPS) to measure the device’s position coordinates with centimeter accuracy (cm level accuracy (half-inch accuracy)) and automatically correct model positioning. These technologies allow digital models to line up exactly with real objects without troublesome on-site alignment work, bringing AR construction verification closer to practical use.

Use Cases of AR Construction Verification on 3D Construction Sites

How is AR construction verification actually being utilized on real construction and civil engineering sites? Here we introduce representative use scenarios at sites advancing 3D construction.

• Civil engineering works (heavy equipment operation / foundation installation): On large-scale land development and road construction sites, heavy equipment operators and construction managers have begun using AR while holding tablets. For example, during excavation and embankment work, operators can display the design's final terrain model in AR in front of the equipment through the tablet, allowing them to constantly compare the current ground surface with the target elevations and slopes as they work. Even inexperienced operators can, without relying on intuition, perform excavation along the design lines, reducing variability in as-built results. In addition, construction managers can visualize layout markings for foundations and the installation positions of structures in AR, enabling accurate layout and installation even without the intuition of experienced workers. There are also reported cases where work proceeded with the accuracy of the design drawings in road and bridge construction by overlaying 3D models on the site during execution.

• Infrastructure maintenance and management (inspection and repair): AR is also being used in inspection work for infrastructure facilities such as railways, expressways, and bridges. Traditionally, maintenance sites had to search for the actual assets while holding drawings and past records, but with AR you can overlay design drawings and inspection information on the structure in front of you. For example, in bridge inspections, AR can overlay bridge drawings and repair histories onto the actual structure so that workers can immediately identify locations that require repair. If previously repaired crack locations are marked in AR, on the next inspection it will be immediately clear "whether it is the same location as last time", helping to prevent oversights. Furthermore, by displaying warning signs and procedural instructions in workers' field of view via AR, it also helps prevent entry into hazardous areas and reduce human errors. In this way, the use of AR in infrastructure maintenance significantly contributes to achieving both inspection efficiency and improved safety.

• Surveying and Pre-construction Checks (Staking and As-built Verification): AR is a powerful tool even in the world of surveying technicians. For example, traditionally staking required measuring control points with a total station and driving stakes to mark locations on site, but with AR you can display virtual stakes and batter boards in place without surveying instruments. A person simply walking the site with a tablet can place AR markers at arbitrary points to indicate “drive a stake here,” dramatically reducing labor. Even on sloped terrain or where obstacles exist, virtual stakes can be projected onto targeted points from a distance, so accurate staking of hazardous areas that cannot be physically accessed is possible. Furthermore, by overlaying point cloud data of the existing terrain (3D-scanned survey data) with the 3D design model in AR, it is possible to verify in advance whether the planned structure will properly fit the site terrain. For example, some cloud services automatically align the existing point cloud and design data, offering a system that allows designers to easily check whether construction can be carried out “as envisioned.” In this way, leveraging AR plus survey data can be expected to improve construction planning accuracy and prevent rework, achieving improved construction planning accuracy and rework prevention.

As described above, on construction sites in the era of 3D construction, AR-based construction verification has begun to be used in a variety of situations. From large-scale general contractor projects to municipal infrastructure maintenance and surveying companies’ as-built inspections, its applications are diverse. In fact, there are reports that Fukui City in Fukui Prefecture introduced a smartphone AR system for on-site surveying during disaster recovery and achieved early surveying of damaged areas and shortened recovery processes, so it can be said that momentum for AR utilization is rising across the industry.

Benefits of AR construction verification: labor reduction, error prevention, explanations to clients, etc.

The growing adoption of AR construction verification is because it brings very significant benefits to construction sites. Here we summarize the main benefits.

• Business efficiency and addressing labor shortages: By utilizing AR, construction inspection and surveying can achieve labor-saving. Positioning tasks that previously required multiple people can be checked by one person holding a tablet, leading to personnel reductions. If the site can be checked and instructed remotely through AR, the number of business trips can also be reduced, and travel time savings can be expected. In fact, there are reports that visualizing progress in real time with AR enabled early detection of schedule delays and optimization of personnel allocation. At worksites facing severe labor shortages, AR is a valuable asset and is driving an era in which "one smartphone per person" enables anyone to become a surveyor or supervisor.

• Error prevention and quality improvement: By proceeding with construction while cross-checking against digital design models, it helps prevent human error. By comparing the AR 3D model with the actual work, slight misalignments or omissions that would previously have been overlooked can be easily detected. For example, during rebar placement checks, the number and spacing can be instantly verified on site, and if defects are found they can be corrected before concrete pouring. On one site, overlaying the drawing model during construction enabled early correction of construction defects, and it was reported that this led to a large reduction in rework and material waste. In this way, AR makes a major contribution to streamlining quality inspections and preventing rework, ultimately improving productivity across the entire project.

• Facilitating explanations to clients and stakeholders: AR construction verification is also powerful as a communication tool. Clients, designers, site workers, and even neighboring residents — stakeholders with different perspectives — can all share the same image of the finished product, making it easier to resolve misunderstandings. For example, if you display a pre-completion structural model on site in AR, clients and local residents can intuitively understand the finished appearance within the actual landscape, preventing mismatches like "it’s different from what I expected." In on-site meetings using AR, clients can make concrete suggestions on the spot, such as "could this be a little lower here?", and the construction side can immediately modify the model — enabling two-way interaction. This shortens the time required to reach consensus, and reduces rework. Information that is difficult to convey with drawings or text can be grasped at a glance with full-scale AR visuals, helping to reduce the burden of explanatory work.

• Safety and risk reduction: AR also contributes to on-site safety management. By highlighting hazardous areas in camera feeds and displaying guided work procedures, it helps with raising awareness and preventing human error. In addition, displaying the locations of pipes and cables buried underground in AR before construction can reduce the risk of accidental damage during excavation. Because anyone can accurately know "what is buried where" for future works, it contributes to preventing unforeseen accidents and improving safety. As a result, AR also plays a role in realizing a secure and safe working environment.

As described above, AR-based construction verification can be called the "trump card" of on-site DX that boosts every aspect of construction management. It offers multifaceted benefits — addressing labor shortages, ensuring quality, smoothing communication, and strengthening safety — so its adoption is likely to accelerate going forward.

Challenges and Countermeasures for AR Implementation in 3D Construction

AR construction verification offers many benefits, but there are several challenges when actually implementing and operating it. Here we explain the potential challenges and practical countermeasures.

• ① Accuracy and alignment challenges: For accurate construction verification with AR, the alignment accuracy between the digital model and the actual site is critically important. On typical smartphone AR, GPS errors and sensor drift can cause the model to shift. To address this issue, the use of high-precision positioning technologies (RTK-GNSS, etc.) is effective. With recently introduced L1/L5-compatible GNSS receivers and augmentation signals from quasi-zenith satellites, even smartphones can achieve centimeter-level positioning (half-inch-level positioning), allowing the model to consistently match real-world coordinates. In fact, by combining dedicated RTK devices with smartphones, systems have been put into practical use where, simply by launching an app, the design model is projected exactly onto the real terrain. Using such technologies enables stable AR projections without positional shifts or drifting, greatly alleviating concerns about accuracy.

• ② Implementation Cost and Equipment Challenges: When people think of using AR, they may picture expensive AR glasses or specialized equipment. However, today it is possible to carry out AR construction verification with just a smartphone or tablet. The latest iPhone/iPad are equipped with high-performance cameras and LiDAR and have strong processing power, making them fully practical as on-site AR platforms. In addition, solutions that combine small GNSS antennas and dedicated apps are offered by various companies, enabling the introduction of AR on site with an investment of around several hundred thousand yen. Compared with traditional surveying instruments, 3D scanners, AR glasses, etc., this is significantly lower cost and far more versatile. Since many field staff can use the smartphones they are already familiar with, education and training costs can also be reduced. In short, AR construction verification can be started simply by "smartly using the smartphones you already have."

• ③ Data organization and operational challenges: AR construction verification requires, as a prerequisite, the organization of digital information such as 3D design data and point cloud data. On small to medium-sized sites, there may be cases where there is no 3D model in the first place. On this point, national policies promoting the adoption of BIM/CIM have made it increasingly possible to obtain 3D models for major infrastructure projects. Also, it has become possible to easily acquire 3D point clouds of existing structures using an iPhone’s LiDAR or drone surveys. For example, using LRTK you can record point clouds with global coordinates simply by walking the site with an iPhone, and then compare them with the design model in the cloud. On the data operation side, systems that integrate with cloud services are increasing, enabling workflows in which point clouds and photos captured on site are automatically uploaded and shared with the office. This gradually reduces barriers such as "data is difficult to handle" and "sharing is a hassle".

• ④ Challenges of on-site adoption and human resource development: When introducing new digital technologies, resistance from on-site staff and varying levels of proficiency become issues. Older technicians in particular may feel confused at first. However, if an AR app runs on familiar devices such as smartphones and tablets and can be used with intuitive操作, it tends to be more readily accepted. In fact, once an AR construction check is tried on-site, many people, because of its clarity, say "I can use this" or "I want to incorporate this more on-site." For younger staff, being able to handle 3D models in a game-like way can also contribute to making new hires productive and to digital human resource development. Furthermore, if using AR enables standardized construction that does not rely on the instincts and experience of veterans, it becomes easier to share person-dependent know-how across the organization. If craftsmen's tacit skills are accumulated as data and AR manuals, skill transfer will proceed smoothly even as generations change. In the early stages of introduction, it is realistic to start with small-scale demonstrations and gradually permeate the whole site by feeding back successful experiences to the field.

Although there are the above challenges, advances in technology and growing on-site demand mean that solutions are becoming clearer. In particular, the combination of high-precision GNSS and smartphones has transformed AR construction verification into something anyone can use by balancing accuracy and ease of use. The important thing is to start small, confirm the effects, and scale up while gaining understanding both inside and outside the company. Worksite DX won't happen overnight, but since it clearly delivers value to the field, it can be regarded as a challenge that can be steadily overcome.

Summary: The future of construction management made possible by 3D construction is here now

From an era that relied on drawings and intuition to an era that leverages data and technology—the construction management of the 3D construction era is steadily evolving. A symbol of this is the new method introduced in this article: AR construction verification. Using AR allows site information to be visualized in real time and shared in a form that anyone can intuitively understand. This is a boon for construction sites struggling with labor shortages and dependence on skilled workers, and it will be the key to simultaneously achieving quality assurance, efficiency, and safety.

The important point is that this future construction management is already right in front of us. AR construction verification is by no means something out of science fiction; it is already being introduced at actual sites across the country. In the i-Construction initiative promoted by the Ministry of Land, Infrastructure, Transport and Tourism, the technology of projecting 3D models and as-built data created during the construction phase onto the site via AR and using them to judge pass/fail has been listed as a priority initiative for fiscal year 2025. In other words, AR-based construction management is highly likely to become the new norm in the construction industry going forward. Adopting AR construction verification on-site at this time can also contribute to strengthening competitiveness for the future.

Finally: With **LRTK**, AR construction checks and surveying can be completed on a smartphone

I have outlined a future vision for AR construction checks, and as a concrete solution to make that future a reality, I introduce LRTK. LRTK is a positioning device & cloud service developed by Refixia, a venture originating from Tokyo Institute of Technology, that attaches a compact RTK-GNSS antenna to a smartphone. When combined with the latest iPhone, a palm-sized smartphone transforms into an "all-in-one surveying instrument" capable of centimeter-level positioning (cm-level, half-inch accuracy) and 3D scanning. By utilizing LRTK, precise surveying and point cloud acquisition that previously required expensive, specialized equipment become accessible to anyone, and the acquired data can be uploaded to the cloud and shared instantly.

Especially in AR construction verification, LRTK demonstrates its true value in simply realizing the aforementioned "high-precision alignment." Because LRTK continuously and accurately tracks the smartphone’s position and orientation, simply launching the app causes the 3D design model to snap perfectly onto the actual terrain. Even as users walk around the site, the model neither shifts nor floats, and the way it remains stably displayed as if the structure were actually standing right in front of them is impressive. Enabling "positionally stable AR projection" without cumbersome initial calibration can be regarded as a revolutionary advance for using AR on-site.

Furthermore, LRTK provides an all-in-one suite of diverse functions that leverage high-precision positioning, ranging from point-cloud scans of existing terrain to AR display of as-built heatmaps, overlaying design CAD drawings, coordinate-based stake placement navigation, indoor positioning, and recording of movement trajectories. All 11 of these functions can be completed with just a single iPhone and LRTK, requiring no special equipment or large-scale systems. It is truly a solution that enables “AR construction verification and surveying to be completed on a smartphone,” powerfully supporting on-site DX.

LRTK has already begun to be adopted at many civil engineering construction sites, and its ease of use—"with one smartphone per person, anyone can handle everything from surveying to AR verification"—is being embraced. As the latest i-Construction-compatible technology, it has been attracting attention at exhibitions and technical proposals hosted by the Ministry of Land, Infrastructure, Transport and Tourism, increasing its presence. If you are interested in AR construction verification or smartphone surveying, please take a look at LRTK's official website or materials. The future of construction management is already in your hands. Harness LRTK and smartphones, and why not take a new step on site starting tomorrow?