Practical AR Inspection Examples: How to Improve Efficiency in As-built Inspections

Table of Contents

• Introduction

• What is an as-built inspection?

• Challenges of traditional as-built inspections

• What is AR inspection?

• Benefits of AR inspection

• Case studies of AR inspection

• Key points for introducing AR inspection

• Precautions when introducing AR inspection

• Conclusion

• FAQ

Introduction

In the construction industry, field construction management methods have been changing significantly in recent years due to ICT and DX (digital transformation). However, as-built inspections (the process of verifying shape and dimensions after construction) still require a great deal of time and effort, and combined with severe labor shortages and an aging workforce, they place a heavy burden on site personnel. With the 2024 overtime regulations (the so-called “2024 problem”) looming, the need to perform quality control efficiently with limited staff has become even more pressing.

One promising solution to these challenges is the on-site adoption of AR (augmented reality) technology using smartphones. In particular, initiatives that combine RTK positioning (real-time kinematic) using a high-precision GNSS receiver attached to a smartphone with AR are becoming more active, offering the potential to digitize inspection tasks that previously relied on manual labor and experience. Combining RTK’s centimeter-level positioning accuracy with AR’s intuitive visualization could turn a palm-sized smartphone into an “all-purpose surveying instrument,” enabling anyone—not just experts—to easily perform site surveying and as-built verification.

This article explains how to improve operational efficiency by incorporating AR technology into as-built inspections, using real-world examples. It organizes the challenges of traditional methods and the advantages of AR, and introduces concrete usage examples and points for implementation on site. Finally, we touch on the new concept of “simple surveying” brought by AR×RTK and hope this provides hints for future construction management.

What is an as-built inspection?

An as-built inspection is an important process in construction management that verifies and records whether the completed structure or terrain matches the shape and dimensions specified in the design documents. Especially for public works, it is required to prove—using measurement data—that the actual as-built conforms to the standards set by as-built management criteria. Typically, heights, widths, thicknesses, and other dimensions are measured after each construction phase, the differences from the design values are examined, and the findings are compiled into drawings and forms for submission to the client. In other words, as-built inspection is a critical test directly linked to quality assurance and the handover of the completed work, and it is an indispensable task for construction management personnel.

Challenges of traditional as-built inspections

• Limited measurement coverage: Traditional as-built inspections rely mainly on manual measurements using tape measures and staffs, so only one point can be measured at a time. It is difficult to cover the entire structure, and there is a risk of overlooking areas that differ from the drawings outside the main points.

• Possibility of human error: Because recording measurement results and taking photographs are done manually, omissions—such as forgetting to measure, failing to record, or missing photos—can occur. Incomplete records undermine the reliability of as-built inspections and can lead to quality issues.

• Labor and time burden: Manual as-built measurements require many workers and long hours. The larger the project, the greater the number of measurement points, and the work can take several days. It is difficult to handle this burden with limited staff, often leading to overtime and schedule delays.

• Dependence on skilled technicians: Accurate as-built management requires experienced surveying technicians. However, the construction industry faces an aging of skilled workers, raising concerns about future labor shortages. Methods that rely on veterans can produce results that are subjective and not easily reproducible.

• Safety issues: Traditional methods can pose safety risks, such as measurements in unsafe footing or surveying near operating heavy equipment. Long measurement sessions increase the chance of accidents and raise the burden and stress on site staff.

What is AR inspection?

AR (augmented reality) is a technology that overlays computer-generated information onto real-world imagery. By viewing the site through a smartphone or tablet camera and overlaying digital information such as design data or measurement results on that screen in real time, on-site intuitive verification and measurement become possible. AR applications in as-built inspections can project 3D design models or reference lines onto site imagery for comparison with constructed elements, or use device sensors to scan the local 3D shape and acquire point cloud data—among other uses. In short, AR inspection aims to replace drawing- and instrument-based verification work with camera-screen-based checks, closing the gap between the site and the drawings on the spot.

Benefits of AR inspection

• Dramatic time savings: Using AR can dramatically reduce the time required for as-built verification and surveying. Processes that used to take half a day to several days from data acquisition to drawing creation can now yield real-time results on site, significantly shortening the lead time to prepare inspection reports.

• Increased productivity through labor reduction: Implementing AR inspection allows tasks that previously required multiple people to be handled by fewer staff. A single person can confirm as-built conditions over a wide area, and tasks previously outsourced to surveying contractors can be handled by in-house staff, reducing labor and outsourcing costs.

• Improved accuracy and coverage: Detailed point cloud data acquired by smartphone or tablet 3D scanning (LiDAR) enables a comprehensive understanding of as-built conditions, including fine details that were previously overlooked. Since the acquired point clouds can be tagged with high-precision coordinates from RTK, deviations from the design model can be checked to within a few centimeters. Data-driven inspections reduce human error and improve quality-control accuracy.

• Improved safety: AR reduces the need for work in hazardous locations, enhancing safety. For example, slope or high-elevation surveying can be remotely confirmed via AR displays, eliminating the need for workers to assume unsafe postures. Shorter measurement times also reduce exposure on site, lowering accident risk.

• Smoother communication: Visualizing design data on site with AR makes information sharing among stakeholders easier. Clients, site supervisors, and workers can view the same AR imagery to confirm conditions, making it easier to align understanding of as-built status and instantly identify areas that need correction. Content that was difficult to convey with paper drawings or verbal descriptions becomes intuitively understood when overlaid on the actual object, accelerating consensus building.

Case studies of AR inspection

• Case 1: Rapid earthwork as-built measurement with smartphone AR surveying: On one earthwork site, as-built measurement that previously required more than half a day with drone photogrammetry was replaced by an on-site scan using an iPad equipped with an LRTK device. As a result, surveying for an excavation area of approximately 150 m² was completed in about 30 minutes in total. The traditional method required multiple steps—“drone flight planning → aerial photography → generation of point cloud from photos → drawing creation”—taking more than five hours. In contrast, the inspector walked the site with an iPad and scanned the terrain with LiDAR to acquire detailed point cloud data in about 15 minutes. Immediately afterward, the point cloud was uploaded to the cloud and automatically converted into drawings and shared. Smartphone AR surveying, which provides high-resolution as-built data on site, has dramatically reduced the number of days required for as-built inspections.

• Case 2: On-the-spot rebar placement checks with AR: AR can also be used for rebar placement inspections of structures. For example, when verifying whether rebar in columns or walls is placed according to the design, overlaying a rebar layout on the smartphone screen allows instant comparison of the number and spacing of rebar on site. Tasks that used to require measuring each bar with a tape can be completed by simply looking at the screen, ensuring that small deviations are not overlooked. The time to cross-check drawings and the actual object is greatly reduced, helping prevent inspection errors such as missing rebar.

Key points for introducing AR inspection

• Preparation of 3D design data: AR inspection requires digital design information to overlay. While BIM/CIM 3D models are ideal, if only 2D drawings are available, coordinate information can be entered to create simple 3D models or reference lines. Organize the design value data required for as-built management in advance.

• Selection of required equipment: Basically, prepare mobile devices capable of AR display such as smartphones and tablets. In addition, combining a compact RTK-GNSS-compatible GPS receiver for outdoor high-precision alignment (for example, smartphone-mounted GNSS devices) is effective. Selecting a device model equipped with a LiDAR sensor allows high-density 3D scanning. Consider the optimal device configuration according to site use and budget.

• Operator training and pilot deployment: To ensure site staff can smoothly use AR inspection, conduct device operation training and pilot deployments before full implementation. Recent AR solutions are often intuitive and can be mastered with short training. Start with a small area to verify effectiveness and accuracy, and transition to full operation while incorporating site feedback.

• Integration into existing workflows: Plan in advance how to record and share point cloud data and photo captures obtained with AR and how to incorporate them into existing inspection documents and reporting flows. It is also important to combine AR with traditional measurement results and compile submission documents in formats required by clients. Establish a system to integrate AR inspection into daily operations without strain, tailored to the realities of the site.

Precautions when introducing AR inspection

• Dependence on satellite positioning environment: High-precision alignment with RTK-GNSS requires an environment where GPS satellite signals can be received reliably. Under elevated structures, in urban canyons, or in heavily treed areas, positioning accuracy may temporarily degrade and communications may become unstable. If positioning is disturbed, AR displays based only on device internal sensors will gradually drift, so measures such as re-calibrating in open areas are necessary.

• Limitations for indoor and underground use: With current technology, achieving centimeter-level AR positioning in indoor or underground spaces where GNSS signals are completely unavailable is difficult. In such environments, AR-based as-built verification is hard to apply and requires relying on other measurement methods such as total stations. Improvements are expected with advances in indoor mapping technology and high-precision location services, but for now the primary application is outdoors.

• Model-to-site alignment: Accurate comparison with AR requires initial alignment of the design data with the site coordinate system. Perform AR adjustment at a known reference point to confirm the model matches the actual object before conducting full inspections. Incorrect coordinate offset settings can cause AR display misalignment and lead to incorrect judgments, so be careful.

• Operational considerations for devices: Prolonged use of AR on smartphones or tablets consumes battery rapidly. Prepare spare batteries and charge during breaks to manage power. In direct sunlight, screen visibility may be reduced and devices can overheat. To comfortably perform AR inspections outdoors, use sunshades or screen protectors and monitor device heating.

Conclusion

AR-based as-built inspections are a revolutionary approach that can drastically reduce conventional labor and errors while raising site productivity and quality-control standards. With just a smartphone and small devices, anyone can perform high-precision surveying and inspection, making AR a viable countermeasure to labor shortages. As the industry accelerates digital technology use through initiatives like the Ministry of Land, Infrastructure, Transport and Tourism’s *i-Construction*, AR inspection is expected to become increasingly widespread and a new norm on construction sites.

In particular, the approach known as “simple surveying,” which combines AR and RTK, is overturning conventional wisdom in site surveying. For example, using a smartphone RTK-integrated solution such as LRTK allows centimeter-level position information to be obtained with palm-sized equipment, enabling on-the-spot comparison with design data and point cloud measurement. Tasks that used to rely on specialized equipment and skilled personnel can now be performed accurately in a short time by anyone, directly contributing to shorter schedules and improved quality. Introducing simple surveying using AR technology is expected to bring major innovation to as-built management on site.

FAQ

Q1. Do I need special equipment or advanced expertise to introduce AR technology on site? A. No. You can introduce it without expensive dedicated equipment or specialist knowledge. For example, smartphone-based solutions like LRTK allow anyone to intuitively use AR simply by attaching a small GNSS receiver to a smartphone and launching a dedicated app. Operation is simple and training burdens for site staff are small—most cases can be mastered with a few hours of training. Compared to conventional surveying instruments, these solutions are more portable and can be easily used in various on-site situations.

Q2. Can a smartphone AR display really align design data and the site accurately? A. By using a system that corrects smartphone positioning with RTK-GNSS (such as LRTK), virtual models can be overlaid on the real object with errors of only a few centimeters. Typically, smartphone built-in GPS has errors of about 5–10 m, but RTK dramatically improves positioning accuracy, bringing the design positions on drawings and the site into almost indistinguishable alignment. On actual construction sites, AR-displayed models have been confirmed to match as-built conditions closely, providing sufficiently practical accuracy.

Q3. Is AR-based position verification possible in areas with poor GNSS reception or indoors? A. Unfortunately, high-precision RTK positioning becomes difficult in environments where GPS satellite signals are hard to receive. In urban canyons or under trees, accuracy may temporarily degrade or positioning may be interrupted. In such cases, it is possible to perform short tasks by performing calibration in an open area and supplementing with phone inertial sensors or camera markers. However, AR positioning is currently difficult in indoor or underground spaces where GNSS signals are completely blocked. In those cases, you must rely on traditional total station measurements or wait for future technological advances. Note that LRTK supports Japan’s Quasi-Zenith Satellite System Michibiki (CLAS signals), so if satellites are visible, positioning is possible even in mountainous areas outside communication coverage, making it adaptable to a relatively wide range of environments.

Q4. Is there any benefit to introducing AR for small sites or short-term projects? A. Yes. In fact, the benefits are often greater for small projects with limited personnel, because AR solutions that allow one person to handle surveying and as-built management are especially advantageous. Tasks that previously required external surveying contractors can be completed quickly by in-house staff, reducing outsourcing costs and wait times. Even for short-duration works, using AR for daily progress checks and as-built inspections enables rapid situation assessment and recording, smoothing coordination with subsequent tasks. From small sites to large projects, AR technology contributes to efficiency and quality improvement regardless of scale.

Q5. Is it possible to use AR glasses (smart glasses) instead of a smartphone? A. There are some examples of using see-through AR glasses or helmet-mounted displays. However, dedicated glasses are expensive, have narrow fields of view, and often require skill to operate, making wide adoption on sites challenging. In contrast, using smartphones or tablets leverages devices that people are already familiar with and keeps introduction costs relatively low. In fact, LRTK is designed as a smartphone-based solution that balances GNSS-based accuracy with the convenience of smartphone AR. It is realistic to start with familiar smartphone AR and consider other devices as needed.