Table of Contents

• What is AR as-built checking

• Benefits of AR implementation

• Key implementation points for achieving results on-site

• Use cases for AR as-built checking

• Challenges and countermeasures to consider when implementing AR

• Simplified surveying and AR checks enabled by LRTK

• Frequently Asked Questions

What is an as-built AR check?

As-built management is a quality control process in civil engineering and construction that verifies whether completed structures and terrain have been constructed according to the design drawings. Traditionally, this as-built verification was commonly performed using surveying instruments such as total stations (TS) and levels, measuring heights and thicknesses point by point on site, and then returning to the office to compare the drawings with the measured values to make a pass/fail judgment. However, this method tended to create a time lag between measuring on site and discovering problems, causing rework. In addition, accurate measurement and judgment require experienced surveyors, and because work is often performed by teams of two, it has become an inefficient process amid labor shortages and an aging workforce, and sites have increasingly demanded further efficiency improvements.

Recently, what has been attracting attention as a trump card to solve these issues is AR (Augmented Reality) technology. AR is a technology that overlays three-dimensional digital information (models, drawings, etc.) onto real-world images; it used to be an advanced experiment, but improvements in the performance of smartphones and tablet devices have made it an era in which it can be used in everyday construction management. In particular, the latest smartphones and tablets are equipped with high-performance cameras and LiDAR sensors, and by using dedicated AR apps that leverage these, it has become possible to intuitively check as-built conditions on site. With industry-wide DX being promoted through measures such as the Ministry of Land, Infrastructure, Transport and Tourism-led [i-Construction](https://www.mlit.go.jp/tec/i-construction/) initiative, the introduction of AR for as-built checks is increasingly expected as a powerful solution that simultaneously enhances on-site efficiency and quality.

Benefits of Adopting AR

Using AR technology for as-built inspections offers many advantages not available with conventional methods.

• Real-time problem detection: Because construction defects and deviations from the design can be detected immediately on site, corrective measures can be taken at once. For example, areas with insufficient pavement thickness or slope can be color-coded in AR immediately after construction, allowing additional work or trimming to be done the same day. Being able to run PDCA on site immediately minimizes rework and prevents quality defects from being left unaddressed.

• Reduced work time and labor savings: Tasks that were measured point-by-point using paper drawings and surveying instruments are replaced in AR by intuitive checks that simply involve holding up a digital model. Because the as-built condition over a wide area can be "visualized" at once, inspections that previously took several days are greatly sped up. Also, since measurement and verification can be performed by a single person, the effort to arrange personnel is reduced, leading to labor savings.

• Addressing labor shortages: On-site personnel can evaluate as-built conditions on the spot without relying on specialized surveyors or veteran technicians. The AR app is simple to operate, and inspection work is completed simply by following the on-screen instructions. Because it can be used without special skills, it prevents dependence on specific individuals, and even inexperienced workers can perform measurements and checks.

• Cost reduction: With AR that uses smartphones and tablets, there is no need to purchase additional expensive TS or GNSS surveying instruments. Dedicated surveying equipment can require an initial investment on the order of several million yen, but recently it has become possible to build a low-cost centimeter-level measurement environment (cm level accuracy (half-inch accuracy)) by combining handheld mobile devices with relatively inexpensive GNSS receivers. Equipment maintenance and transport costs to the site can also be reduced.

• Improved measurement accuracy and reliability: AR reduces the risk of manual measurement errors and recording mistakes. There is no need to transcribe numbers noted on-site, and because digital data can be compared directly, human error can be eliminated. Furthermore, when combined with high-precision positioning technologies such as RTK-GNSS, measurement results will always conform to public coordinate systems with cm level accuracy (half-inch accuracy), enabling more reliable as-built verification than before.

• Efficiency of recording and reporting: Using AR allows results from as-built inspections to be captured as intuitive visuals, making it easier to prepare reporting materials. For example, by attaching AR screen screenshots or difference heatmap images directly to inspection reports, the materials become easier to understand than conventional reports that contain only numbers. In fact, on-site demonstrations by the Ministry of Land, Infrastructure, Transport and Tourism have confirmed that the use of AR technology can simplify submission documents such as as-built drawings. Because records are kept digitally in this way, follow-up verification is also easy, reducing the burden of reporting tasks.

• Consensus building and communication improvement: The "visualization" provided by AR is also effective for sharing information with on-site personnel and the client. If you hold a tablet at the construction site and overlay the completed image onto the actual object, explanations go smoothly even during the client's inspection. For example, by showing the as-built condition on AR, misunderstandings with the client are reduced, and agreement on corrective locations can be reached on the spot. A survey by the Ministry of Land, Infrastructure, Transport and Tourism also reports that AR is beginning to be used not only for construction management but also for pre-construction briefings to residents and information sharing with subcontractors. In this way, AR contributes to smoother communication both inside and outside the site.

Key Points for Achieving Results On-site

There are a few key points for effectively embedding AR-based as-built checks at the worksite. By keeping the following points in mind during implementation, you can achieve smooth results.

• Ensuring high-precision alignment: To correctly overlay digital information in AR, accurate alignment with the real-world coordinate system is essential. Especially on large sites or with long objects, even slight positional offsets can lead to large errors, so leverage GNSS RTK positioning and calibration at known points to always align with centimeter-level accuracy (cm level accuracy, half-inch accuracy). With an RTK-enabled AR system, you can project models without the hassle of placing markers on site, enabling stable AR displays that do not drift as you walk around.

• Preparing 3D design data: For AR as-built checks, 3D models of design drawings (such as BIM/CIM data) form the basis. If 3D data is not yet available, create a simple model from 2D drawings or digitize the current conditions by point-cloud scanning, etc., to prepare reference data. Because the Ministry of Land, Infrastructure, Transport and Tourism is promoting CIM initiatives, the practice of creating 3D data from the design stage is advancing, so in the future models should be easier to obtain for any construction work. It is important to become familiar with handling 3D data within your company as early as possible.

• Integration into operational workflows: To make AR checks part of routine on-site work rather than a one-time demonstration, clarify when, who, and at what timing will use them. For example, incorporate steps such as "use AR for rebar inspection before concrete placement" and "use AR to check the finish after completion of each embankment" into construction plans and checklists in advance. Also decide how to record the results confirmed by AR and reflect them in reports. If you use a system that automatically attaches date/time and location information to screenshots and saves them to the cloud, those images can be used directly as evidence in inspection forms, which is convenient. By incorporating AR into existing quality control workflows, it will become a tool that everyone on site uses as a matter of course.

• Training for on-site staff: To reduce resistance to new technology, it is important that on-site staff understand how to use AR and the benefits it brings. Initially, tech-savvy staff should take the lead and pilot AR checks on small-scale tasks. It is essential to demonstrate the tool in practice so they can experience firsthand that "anyone can perform measurements just by following the on-screen prompts." Recent AR apps are intuitive and easy to use, and can be learned with a short training even without specialist knowledge. By sharing operating procedures through in-house training and on-the-job training (OJT) and presenting real examples that convey the benefits to veteran staff, smooth acceptance can be achieved.

• Staged implementation and validation: Rather than deploying AR checks across all sites and processes at once, first introduce them experimentally at a subset of sites or processes and verify their effects and issues. For example, try using AR measurement in a specific work section only, and present data on the degree of efficiency improvement and error reduction compared with conventional methods—this makes it easier to gain understanding both inside and outside the company. Start small to accumulate know-how, and if problems arise (such as how to handle equipment or methods for accuracy verification), improve them before rolling out company-wide. If you prepare internal manuals and checklists based on the demonstration results, subsequent rollouts to other sites will proceed smoothly.

• Use of cloud services: By using cloud services linked with the AR app, measurement data, point-cloud models, site photos, and other items can be automatically saved and shared in the cloud. This enables real-time sharing of information between the field and the office, allowing you to check as-built conditions on the AR screen even from remote locations. Because the entire team can view and comment on the latest data in the cloud, instructions for corrective actions and requests for additional investigations can be carried out quickly. Furthermore, data is accumulated on the cloud as a history, so it can be referenced in future construction projects or used as evidence if a problem occurs. When introducing AR, enable cloud integration functions as much as possible to achieve centralized data management and smooth information sharing.

Use Cases of AR As-Built Inspections

In real-world sites, AR-based as-built checks are beginning to be used in a variety of applications. Here are some representative use cases.

• Confirmation of rebar and structural positions: AR is effective for inspecting rebar placement before concrete pouring and for checking positional shifts of structures during construction. For example, when confirming whether the reinforcement placement of a column is offset, if you display the rebar placement drawing in AR on site and check the number of bars and their spacing, work that previously required measuring with a tape measure can be done at a glance. By overlaying the design 3D model on the actual object to detect minute deviations, construction can proceed while maintaining accuracy. There have even been reports that on-site AR verification made early correction of defects possible, reducing rework and material waste.

• As-built inspection of pavement thickness and slopes: On road paving projects, combining AR and point-cloud measurement enables areal evaluation of as-built conditions over wide areas. Immediately after paving, scan the road surface with a smartphone-mounted LiDAR to obtain a high-density surface point cloud. By overlaying the design 3D model on this, an on-site as-built heatmap with elevation differences color-coded can be generated. You can determine at a glance whether pavement thickness across the entire section is within design tolerances, and thoroughly detect surface irregularities and insufficient thickness. Because longitudinal gradient and width can be measured directly on the point-cloud data, inspections can be completed safely and quickly, and some sites have achieved zero rework afterward.

• Checking buried pipes and other hidden items: With AR, objects buried underground such as pipes and cables that become impossible to directly visually inspect after construction can be "see-through" checked. For example, in sewer pipe work, pipes are 3D-scanned before burial and the point-cloud data of their exact positions and depths are saved to the cloud, and after backfilling there are cases where simply holding a smartphone over the area allows anyone to grasp the alignment and depth of the underground pipes. This eliminates the need for marking immediately after burial, and during future maintenance AR displays make it easy to excavate while avoiding buried items. The ability to visualize invisible things is also a major advantage of AR as-built inspection.

• Use of slope and terrain models: In steep-slope works and large-scale land development, combining 3D scanning and AR for as-built management can improve safety and efficiency. For example, if a slope is scanned once before construction to obtain baseline data, and then re-scanned after construction or after a disaster and the two scans are compared, the extent of collapse and increases or decreases in fill volume can be calculated immediately. What used to take several days to calculate earthwork volumes can now be completed in minutes, and the results can be used for recovery planning and as-built evaluation. Furthermore, overlaying the resulting slope point-cloud model onto the actual site view with AR lets all workers intuitively share hazardous areas and the locations of reinforcement anchors. In this way, by combining 3D data of terrain and structures with AR visualization, as-built management and deformation detection over wide areas and at height—which was previously difficult—can be carried out safely and reliably.

Challenges and Countermeasures to Consider When Implementing AR

AR-based as-built verification offers many advantages, but there are also several points to be aware of when introducing and operating it. Below is a summary of the main challenges and their countermeasures.

• Concerns about accuracy: The worry "Can AR really measure accurately?" is often heard. Indeed, accuracy management is important because incorrect alignment prevents correct judgments. As countermeasures, removing the offset between the digital model and physical space through RTK corrections using GNSS and precise calibration at known points is recommended. By fusing a GNSS rover with AR, it is possible to spatially align design data and the as-built in front of you exactly, and it has been demonstrated that, when operated properly, checks can be performed at a level of accuracy comparable to conventional surveying (both plan and elevation within a few centimeters (a few inches)). In the initial stages, be careful to ensure accuracy by, for example, using conventional measurements at key points to verify errors.

• Digital data preparation burden: AR use requires digital 3D models or point cloud data, and there are concerns that preparing these takes time. Although BIM/CIM design data is gradually becoming more common, some small- to medium-sized projects still lack 3D data. Even in those cases, LiDAR-scanning the site to obtain as-built point clouds allows them to be used as an improvised 3D model. There are also apps that can create and display simple reference lines or surfaces in AR when only 2D drawings are available. The Ministry of Land, Infrastructure, Transport and Tourism’s guidelines are also advancing the shift to as-built management using three-dimensional measurement technology, and digital data will become increasingly easy to obtain. While it may feel burdensome at first, once data is organized it will aid subsequent process management and future maintenance, so it is important to approach it as an investment in digitization.

• Device and on-site environment considerations: Physical challenges when using smart devices on site must also be taken into account. For example, under direct sunlight in midsummer, screens can become hard to see and battery consumption can increase significantly. Outdoors, these issues can be mitigated by using sun hoods for tablets or carrying portable power banks. Also, for use in rainy conditions, prepare waterproof cases or splash-resistant covers for tablets. In dusty environments, it is also important to clean camera and sensor areas frequently. Furthermore, if it is difficult to work for long periods holding a tablet in one hand, measures such as using a neck-mounted holder can be effective. By adopting accessories and operational methods suited to the on-site environment and creating conditions that make devices easier to operate, you can maximize the effectiveness of AR.

• Resistance among onsite staff: The psychological hurdle toward new technologies cannot be ignored. In particular, veteran workers sometimes say, "I'm more comfortable with the traditional manual methods." The best solution to this issue is to actually demonstrate AR and let them experience its effects firsthand. For example, sharing concrete results — such as inspections that previously took half a day being completed in 30 minutes with AR, or rebar errors that had been missed being discovered on the spot — will greatly change attitudes. Also, tools like LRTK, which allow "anyone to easily perform surveying alone," often receive praise on site because tasks that used to require two people can be completed by one. If you first have younger employees use it and roll it out in a way that lets its convenience spread across the entire site, the resistance will gradually fade.

• Introduction costs and ROI: Introducing new equipment or software involves costs, but in the case of AR the upfront investment hurdle is greatly reduced because existing smartphones and tablets can be repurposed. As mentioned above, instead of purchasing expensive dedicated surveying instruments, you can begin with costs such as GNSS receivers and software usage fees. In addition, considering quantifiable effects like reduced rework and labor savings, investment recovery can be expected relatively early. For those worried about cost-effectiveness, it is effective to introduce it on a limited basis first and demonstrate visible results (e.g., X% reduction in labor hours, Y fewer defect-correction cases) internally. Calculating ROI based on actual performance data will provide material for explanations to management and clients, making it easier to secure further investment decisions.

• Application to official inspections: Currently, as-built management procedures may require traditional measurements and drawing production to be carried out in parallel. Some supervisors (inspectors) may be cautious about accepting approval based solely on checks on digital devices. However, the Ministry of Land, Infrastructure, Transport and Tourism has confirmed the effectiveness of on-site as-built inspections using AR and similar technologies, and AR-based labor-saving methods are expected to be incorporated into guidelines going forward. Even now, using software that automatically generates as-built documentation from point clouds and photos obtained with AR can yield deliverables equivalent to manual work, so in practice the process can be completed using AR measurements alone. The important thing is to appropriately explain AR results to clients and supervisors and obtain their understanding. For example, showing an as-built heat map directly on a tablet screen during an inspection can prove quality more convincingly than paper drawings. With understanding of AR use gradually deepening in both the public and private sectors, early adoption and accumulation of know-how will lead to a future advantage.

Simple Surveying and AR Checks Enabled by LRTK

One solution attracting attention for enabling these AR-based as-built checks more easily and with higher accuracy is LRTK. LRTK is a cutting-edge tool that, by attaching a small GNSS receiver to a smartphone, enables centimeter-level high-precision positioning via RTK and is a next-generation system that allows surveying tasks that previously required specialized equipment and experienced operators to be completed by a single person. It supports CLAS corrections from Japan’s GPS “Michibiki” and network RTK, maintaining stable high accuracy even in mountainous areas outside of communication coverage. In other words, its major strength is that even without a veteran surveyor you can handle everything from control point surveying to as-built inspection with just a smartphone.

LRTK also integrates seamlessly with AR functionality. By using high-precision GNSS positioning to precisely overlay 2D/3D design data on-site, the cumbersome task of alignment is unnecessary and you don't have to worry about objects shifting.

For example, simply walking the site with a tablet lets you accurately indicate virtual pile locations from the design model on the actual ground, and instantly identify target coordinates even at distant points. You can also automatically overlay the acquired as-built point cloud data with the design model on the LRTK cloud for difference comparison, allowing you to immediately check whether construction is being carried out according to plan.

LRTK also provides a cloud platform, and data measured or scanned on site is synchronized to the cloud on the spot. Team members can view the site’s 3D point clouds and survey point information in real time from office PCs, and proceed with verification while sharing data among stakeholders. On the cloud, distance, area, and volume measurements can be performed, and photos can be linked to location information and displayed in a list with a single click. This enables collaboration that transcends the boundaries between site and office, dramatically improving the efficiency of as-built inspections.

Additionally, LRTK offers a variety of features beyond as-built management, such as a "Coordinate Navi" function that allows a single person to guide pile-driving locations, a function to calculate embankment volumes from point clouds acquired by a LiDAR scanner, and a cloud-sharing function for high-precision geotagged photos. In other words, it is designed so that surveying, verification measurements, recording, and as-built inspection — processes that previously required multiple devices — can be completed with a single iPhone. Data obtained on site can also be used and delivered in a format compliant with the Ministry of Land, Infrastructure, Transport and Tourism's guidelines for as-built management, and in fact many construction companies have begun adopting LRTK to achieve both labor savings and improved quality.

Using smartphone surveying + AR systems like LRTK makes it possible for anyone to easily perform high-precision as-built checks, overcoming many of the constraints associated with surveying and inspection. Even on sites struggling with labor shortages, by adopting a "one device per person" approach—providing each worker with a smart surveying tool and leveraging AR—you can shorten work time, reduce human error, and improve communication. These technological innovations strongly accelerate DX (digital transformation) in construction and are fundamentally changing the way as-built management is conducted. The key to successful AR-based as-built checks is to effectively incorporate these advanced tools and link them to productivity improvements across the entire site. Make the latest technologies your ally and let your company's on-site "as-built AR checks" demonstrate their true value.

Frequently Asked Questions

Q: What do you need to start as-built AR checks? A: Basically, you need a smartphone or tablet capable of AR display, a GNSS receiver to improve measurement accuracy, and an AR surveying app that supports them. The latest iOS/Android devices are well equipped with cameras and sensors, making them suitable for AR use. If centimeter-level accuracy (half-inch accuracy) is required, combine a small Bluetooth-connected GNSS rover for RTK positioning (for example, there are LRTK devices that can be mounted on a smartphone). In addition, prepare digital data for comparison such as design 3D model data and point clouds. Once these are set up, you can immediately try as-built AR checks on site.

Q: Can the accuracy of as-built checks using AR be trusted? A: Yes — if operated properly, high reliability can be ensured. Systems using GNSS RTK corrections can achieve positioning accuracy on the order of several centimeters (a few inches) in both horizontal and vertical dimensions. This falls within the accuracy range typically required for standard as-built checks. Also, when verifying differences in AR, heatmap displays and the like can provide quantitative information, such as which points are how many centimeters higher or lower (how many inches). The important things are to align with on-site control points beforehand and to perform spot verifications using conventional methods as needed. Doing so will allow you to trust the results of AR checks with sufficient justification.

Q: Can AR be used on sites that don't have a 3D design model? A: AR can be used with some ingenuity even when a 3D model is not available. For example, there are apps that overlay 2D drawing data (DXF, etc.) in AR space so that key lines and positions can be visualized on site. Also, if the finished form is not complex, a simple approach is to mark key dimensions on site before construction and superimpose them on images captured with AR. However, AR really shows its value when a 3D model is available. Recently, the creation of CIM models has been increasing, especially for public works, so consider asking the client to provide 3D data or creating a simple model in-house. On the other hand, if the purpose is to compare as-built measured data (point clouds) with the design drawings, you can detect differences using point cloud processing software instead of relying on AR. The point is that the goal is intuitively verifying things on site, so choose the method that best fits whether or not you have a model.

Q: Can AR check results be used for official inspections? A: At present, operations that treat AR as the sole basis for official inspections have only just begun, but the trend is toward gradually recognizing its use. The Ministry of Land, Infrastructure, Transport and Tourism also conducted on-site demonstrations in fiscal year 2023 and confirmed that AR technology can allow omission of as-built documentation. Currently, traditional records (survey drawings and photo logs) are often still required in parallel, but submitting AR-based confirmations as supplementary materials has the advantage of making it easier for inspectors to understand. For example, during an inspection, if you display on an AR heat map information such as "this location is ◯ cm (◯ in) higher/lower than the design," it communicates more intuitively than a conventional numerical table. In the future, the AR data itself is increasingly likely to be recognized as an official deliverable, but at this stage it is safer to treat it as "use as supporting evidence" and to combine it with conventional measurements as needed.

Q: I'm worried whether everyone on site will be able to master this technology. A: AR construction support tools have become increasingly user-friendly, and their basic operations are not difficult. In fact, at many companies that have implemented them, staff from young workers to veterans can use them after brief training. If you remain uneasy, start by having a person familiar with the operation demonstrate it on site while other staff observe. People tend to become more positive when they see the benefits with their own eyes; once they realize "it's certainly faster" and "it's easy to understand," their resistance usually fades. Also, recent AR apps offer Japanese-language interfaces and robust support, making it easy and reassuring to get help when needed. As on-site ICT use is becoming increasingly essential, take your time and work step by step to create an environment where everyone can use it.

Q: Do you need dedicated AR glasses? A: At present, smartphones and tablets are sufficient for practical use in most cases. AR-capable smart glasses (see-through goggles) are available, but they are very expensive and have challenges such as being difficult to use together with safety helmets. In contrast, smartphones and tablets can be used on-site simply by placing them in dust- and waterproof cases, and operation is easy via touchscreen. Since resolution and processing power are improving every year, both visibility and performance are sufficient for business use on mobile devices. In the future, if glasses become lightweight and inexpensive their use may expand, but at present, AR use via handheld devices is the most realistic and cost-effective. We recommend starting with familiar smartphone AR and, as needed, considering future device rollouts.