Beginner's AR Inspection Guide: Key Points for Using AR in As-built Inspections

Table of Contents

• What is as-built inspection?

• Traditional as-built inspections and their challenges

• Benefits of introducing AR

• Key points to establish AR inspections on site

• Use cases of AR inspections

• Closing: Anyone can start AR inspections with easy surveying using LRTK

• Frequently Asked Questions

What is as-built inspection?

In civil engineering and construction, as-built inspection is an important quality-control process that verifies and records whether completed structures, developed land, and so on match the shape and dimensions shown on the design drawings. Especially for public works, the results of these as-built confirmations often determine whether an inspection is passed or whether the project can be handed over, so reliable as-built management is required. Traditionally on site, workers used tools such as tape measures, leveling staffs, and levels to manually measure key post-construction dimensions, took site photos, then returned to the office to compare and report against the design values. However, this method requires a lot of manpower and time and can only measure limited points, so there is an unavoidable risk of oversights.

Against this backdrop, a solution that has attracted attention in recent years is the use of AR (Augmented Reality) technology. AR overlays digital information (such as design drawings or 3D models) onto live images of the real world. By viewing the site through a smartphone or tablet camera and projecting design data onto that screen, you can intuitively understand discrepancies between the actual construction and the design in real time. For example, if you display the design finish elevations and slope lines on a newly paved road in AR, you can immediately judge whether the as-built falls within the allowable range. What makes AR-based as-built inspection (AR inspection) possible is high-precision positioning from GNSS and the sensors in smartphones. By attaching a compact GNSS receiver to a smartphone and performing positioning using the RTK (Real Time Kinematic) method, you can determine your position within an error range of a few centimeters (a few in). Based on that information, a digital design model can be overlaid at the correct position in space, so the virtual model remains aligned with the real object even as the user walks around the site. In other words, AR × GNSS is enabling the digital evolution of as-built management processes, allowing as-built verification on site in real time.

Furthermore, as industry-wide construction DX is being promoted through initiatives such as the Ministry of Land, Infrastructure, Transport and Tourism-led [i-Construction](https://www.mlit.go.jp/tec/i-construction/), AR-based as-built inspection is expected to be a powerful means to simultaneously improve site efficiency and quality.

Traditional as-built inspections and their challenges

Several challenges are pointed out with traditional as-built inspection methods.

• Labor- and time-intensive: Measurement work typically requires a team of multiple people. The larger the site, the more measuring points there are, and it can take a full day. With a shortage of experienced survey technicians, finishing the work within project timelines with limited personnel has been a major burden.

• Lack of coverage and risk of oversights: Manual measurement has physical limits, making it impossible to measure every point in the construction area. Even if representative points are measured, other areas may still differ from the design. The larger the structure, the easier it is to miss minor distortions or irregularities, and during inspection there are frequent cases of frantic rework when discrepancies with the drawings are pointed out.

• Risk of human error: On busy sites, people often forget to take photos or make mistakes when jotting down or transcribing measurements. For example, if photos of buried pipes are not taken before backfilling, it may become impossible to prove later that the work was properly carried out. There have been cases where such human errors led to quality problems, placing heavy burdens and anxiety on site personnel.

Because of these issues, a more efficient and reliable method for as-built management has long been sought. With recent labor shortages and work-style reforms, expectations for using new technologies to reduce manpower and improve productivity are increasing on sites.

Benefits of introducing AR

Incorporating AR technology into as-built inspections yields many benefits that traditional methods do not offer.

• Detect and correct issues on the spot: AR allows you to immediately detect construction defects or discrepancies with the design and take corrective action on site. For example, in paving work you can immediately display surface elevations on AR with color coding after paving, and correct thin spots the same day by adding pavement. Being able to run PDCA on site minimizes rework and prevents long-term neglect of quality defects.

• Time savings and labor reduction for inspection tasks: The traditional work of holding paper drawings and measuring each point with survey equipment is transformed into visualizing a wide area at once by pointing a tablet with AR. Inspections that used to take days can be greatly accelerated, and one person can complete measurement and verification, reducing the effort required to arrange personnel.

• Addressing labor shortages: AR apps are simple to operate, and following on-screen instructions completes measurement and verification. Because no special skills are required, site personnel can evaluate as-built conditions without relying on veteran surveyors. Even less experienced workers can perform measurements and checks, helping to prevent knowledge concentration in specific individuals.

• Cost reduction: Using AR with a smartphone or tablet combined with a relatively inexpensive GNSS receiver eliminates the need to purchase expensive total stations or dedicated GNSS survey instruments. You can build a centimeter-level measurement environment while significantly reducing initial investment, maintenance costs, and transport costs to sites. Time savings and reduced staffing also offer large cost benefits, so overall the effect often exceeds the investment.

• Improved accuracy and reliability: AR reduces the variability and recording mistakes of manual measurement. There is no need to rewrite handwritten numbers, and digital data can be compared directly, eliminating human error. Combined with RTK-GNSS high-precision positioning, coordinate alignment can be performed with centimeter-level accuracy (half-inch accuracy) that matches public coordinate systems, enabling more reliable as-built inspections than before.

• Streamlined recording and reporting: Because inspection results displayed in AR can be saved directly as screenshots or differential heatmap images, creating reports becomes easy. Information that was hard to convey in numeric tables becomes obvious to the client when recorded as color 3D visuals. In fact, field demonstrations by the Ministry of Land, Infrastructure, Transport and Tourism confirmed that AR use can simplify some required as-built documentation. If digital data is stored in the cloud, it is easy to review later, reducing the burden of preparing inspection reports.

• Better consensus-building and communication: AR visualization is powerful for sharing information with stakeholders inside and outside the site. For example, during an inspection, overlaying the completed image onto the real object on a tablet reduces mismatched expectations with the client and makes it easier to agree on corrective actions on the spot. Ministry reports show AR is beginning to be used not only for construction management but also for explaining projects to nearby residents before construction and for meetings with subcontractors. Because anyone can intuitively understand the situation by viewing the real object, AR greatly facilitates smoother communication and consensus-building.

Key points to establish AR inspections on site

Here are key points to keep in mind to effectively introduce AR-based as-built inspections and make them standard on site.

• Ensure high-precision alignment: Accurate alignment with the real space is critical to overlay digital design information correctly in AR. Especially on large sites or long structures, a displacement of a few centimeters (a few in) can lead to significant errors. Use RTK-capable GNSS or calibration with known points to always align coordinates to centimeter-level accuracy (half-inch accuracy). An AR system integrated with RTK-GNSS can project models in their designated positions without pre-installing reference stakes or targets, enabling stable AR displays that do not shift when moving.

• Prepare 3D design data: The foundation of AR inspection is a 3D model (BIM/CIM model, etc.) created from design drawings. If only 2D design data is available, consider creating a simple 3D model or obtaining point cloud data by LiDAR scanning the existing conditions so you have digital data for comparison. The Ministry-promoted CIM (Construction Information Modeling) initiative is expected to accelerate the preparation of 3D data across projects. It is important to develop in-house skills and environments for handling 3D data early.

• Integrate into operational workflows: To make AR checks part of routine operations rather than a one-off demo, clearly define when, who, and at what timing AR will be used. For example, include steps in construction plans and checklists such as “use AR for rebar inspection before concrete placement” or “verify finish after each embankment completion using AR.” Also standardize how AR-confirmed results are recorded and reflected in reports. For instance, use a system that automatically adds date/time and position information to AR screenshots and saves them to the cloud so those images can be used directly as evidence in inspection logs. Embedding AR into existing quality-management flows will make it a natural tool for everyone on site.

• Train site staff: To remove resistance to new technology, ensure site staff understand how to use AR and its benefits. Start with a digital-savvy person trialing AR inspection on a small scope. Demonstrate on the screen that “anyone can measure by following the instructions,” so people can experience it firsthand. Modern AR apps are intuitive and easy to learn, so short training is often sufficient. Share operation procedures through in-house training and on-the-job training so even veterans see the benefits—this helps smooth adoption.

• Phased introduction and validation: Rather than deploying AR across all sites and processes at once, begin by piloting it on a few sites or processes to verify its benefits and challenges. For example, run AR measurements in parallel with traditional measurements on a specific section and compare time savings and error reduction with data. Sharing quantitative results internally helps gain understanding from other departments and management. Start small to accumulate know-how, identify issues (such as handling equipment and verifying accuracy), and address them before full-scale rollout. Developing internal manuals and checklists based on pilot results will facilitate broader deployment.

• Use cloud services: Using cloud services integrated with AR apps lets you automatically store and share measurement data, point clouds, and site photos. This enables real-time information sharing between site and office and allows remote personnel to check the 3D site situation while giving instructions. With the team accessing the latest data and commenting on the cloud, sharing correction points or requesting additional surveys is fast. Data stored as a history in the cloud is also useful as reference material for future projects or as evidence if problems arise. When introducing AR, actively leverage cloud integration for centralized data management and smooth information sharing.

Use cases of AR inspections

On actual sites, AR-based as-built inspections are starting to be used in a variety of ways. Here are some representative use scenarios.

• Verifying positions of rebar and structures: AR is effective for checking rebar placement before concrete placement and for verifying positional offsets of structures during construction. For example, when checking whether column rebar positions are correct, displaying the rebar layout in AR on site allows what used to be checked by scale or eye to be done at a glance. Overlaying the design 3D model onto the real object lets you detect minute errors and proceed with construction while ensuring accuracy. There are reported cases where early defects were found through AR field verification, reducing rework and material waste.

• Inspecting pavement thickness and slope as-built: For road paving, combining AR with point-cloud measurement enables areal evaluation of as-built over wide areas. Right after paving, scan the road surface with a smartphone LiDAR scanner to acquire a high-density surface point cloud. Overlaying the design finished model generates an as-built heatmap on site with color-coded elevation differences. You can instantly determine whether pavement thickness and slope across the entire section are within design limits and detect unevenness or insufficient thickness without omission. Some sites have confirmed zero repairs afterward by verifying pavement as-built with AR + point clouds.

• Verifying buried utilities and other hidden objects: AR can “see through” things that become invisible after construction, like buried pipes and cables. For example, in a sewer project, pipes can be 3D scanned before backfilling and their exact positions and depths saved in the cloud; after backfilling, anyone can point a smartphone at the area and verify the pipe routes and depths. This eliminates the need for immediate surface marking after burial and enables accurate excavation that avoids buried items during future maintenance. Visualizing the invisible is a major advantage of AR inspections.

• Using slope and terrain models: For steep slope works or large-scale land development, combining 3D scans with AR improves safety and efficiency. Scan the slope once before construction to obtain baseline data, then re-scan after construction or after a disaster and compare to instantly calculate collapsed areas or changes in fill volume. What used to take days to compute can now be done in minutes, aiding restoration planning and as-built evaluation. Overlaying the slope point cloud model onto the site via AR lets all workers intuitively share dangerous areas or anchor locations needing reinforcement. Using AR makes as-built management and deformation detection over wide or high areas safe and reliable.

Closing: Anyone can start AR inspections with easy surveying using LRTK

As introduced above, AR-based as-built inspection brings major advances in site productivity and quality control. The tools that support this are also steadily evolving. For example, LRTK, developed by a venture from Tokyo Institute of Technology, is a cutting-edge system that enables centimeter-level high-precision positioning simply by attaching a compact RTK-GNSS receiver to a smartphone. Used with a dedicated app, surveying and inspection tasks that previously required specialized equipment and skilled operators can now be completed as easy surveying using just a smartphone. LRTK supports CLAS corrections from the Japanese GPS system “Michibiki” and network RTK, enabling stable high precision even in mountainous areas where base stations are not nearby. In short, LRTK’s major strength is that even without veteran surveyors, one person can handle everything from reference-point surveying to as-built inspection.

LRTK also integrates seamlessly with AR functions. Based on the high-precision GNSS-determined position, 2D/3D design data can be overlaid exactly on site, eliminating troublesome alignment work and preventing model drift. For example, simply walking the site with a tablet can accurately indicate the virtual stake locations from the design on the actual ground, making target coordinates visible even at distant points. You can also automatically overlay acquired point-cloud data of current conditions and the design model in LRTK’s cloud for differential comparisons, allowing you to instantly check on site whether the work is being built according to the design.

By utilizing smartphone surveying + AR systems like LRTK, anyone can easily perform high-precision as-built inspections, overcoming many constraints related to surveying and inspection. Even in sites suffering from labor shortages, a “one person, one device” smart surveying tool plus AR can shorten work time, reduce human errors, and enable information sharing with remote locations. These technological innovations strongly support construction-site DX and are fundamentally changing how as-built management is done. Take this opportunity to adopt the latest digital technologies and make full use of the benefits of AR inspection at your site.

Frequently Asked Questions

Q: What do I need to start as-built inspection using AR? A: Essentially, you need a smartphone or tablet capable of AR display, an RTK-capable GNSS receiver for high-precision positioning, and an AR surveying app that supports those devices. Prepare design data (3D models or electronic drawings) in advance and load them into the app. Modern iOS/Android devices have high-performance cameras and sensors suitable for AR. If centimeter-level accuracy (half-inch accuracy) is required, combine the device with a Bluetooth-connected compact GNSS rover (a smartphone-mounted GNSS, etc.) for RTK positioning. With this equipment and data set up, you can immediately try AR-based as-built inspection on site.

Q: Can the accuracy of AR inspections be trusted? A: Yes—when operated properly, AR inspection accuracy can be trustworthy. Systems corrected by RTK-GNSS can achieve positioning accuracy of several centimeters (a few in) in both horizontal and vertical directions. This falls well within the accuracy range typically required for as-built inspections. When checking differences in AR, color-coded heatmaps enable you to see quantitatively which points are a few centimeters high or low. The important points are to align site control points and AR display carefully beforehand and to perform traditional double-checks at key locations as needed. If these precautions are followed, the AR results can be trusted as robust evidence.

Q: Can I use AR even if there is no 3D design model for the project? A: Even without 3D design data, AR can be used with some ingenuity. Some apps can overlay 2D CAD drawings in AR space to visualize key lines and positions on site. Alternatively, for simple finished shapes, you can mark main dimensions on site before construction and overlay those markings onto AR-captured images for a simple check. However, AR’s full potential is realized with 3D models. As CIM models (3D design data) are increasingly used in public works, consider requesting data from the client or creating a simple model in-house. If you are comparing measured point clouds to design drawings, you can also use point-cloud processing software to detect differences without forcing AR. The goal is to enable intuitive on-site confirmation, so choose the method appropriate for whether a model is available.

Q: Are AR inspection results accepted as official inspection records? A: Currently, operations that rely solely on AR for as-built management are just getting started, and some inspectors may not accept checks on digital devices alone. However, the Ministry of Land, Infrastructure, Transport and Tourism conducted field demonstrations in FY2023 and confirmed that AR use can allow partial omission of submitted as-built documents. Even now, if you use software that automatically creates as-built drawings from point-cloud data or heatmap images obtained by AR, you can produce deliverables comparable to manual methods, so it is practically possible to complete inspections using only AR measurements. The key is to carefully explain and gain understanding of AR results from the client and inspectors. For example, showing an as-built heatmap on a tablet during an on-site inspection is more persuasive than paper drawings in demonstrating quality. As public and private understanding of AR grows, early adopters who accumulate know-how will gain future advantages.

Q: I'm worried whether all site staff will be able to use this technology. A: AR construction support tools are becoming more user-friendly year by year, and basic operations are not very difficult. In fact, many adopting companies report that staff from young to veteran learn operations in a short training period. If concerns remain, start by having a digitally proficient person demonstrate on site while others observe. People are more willing to adopt technology when they see benefits firsthand—if they experience that it is “indeed faster” and “easy to understand,” resistance fades. Many recent AR apps support Japanese and have vendor support, so you can contact developers if issues arise. Proceed gradually to create an environment where everyone can use the tools comfortably.

Q: Do I need expensive dedicated equipment like AR glasses? A: At present, smartphones and tablets are sufficient for practical AR inspections. While AR-capable smart glasses (transparent goggle-type devices) are available, they are often very expensive and may be difficult to use with safety helmets. Smartphones and tablets can be used on site in dustproof/waterproof cases and are operated intuitively by touch. Device screen resolution and processing performance improve yearly, and mobile devices now meet visibility and performance requirements for work use. If glasses become lighter and cheaper in the future, their adoption may expand, but currently starting with smartphone AR is the most realistic and cost-effective approach. Begin AR inspections with familiar devices and consider glasses later if needed.

Q: Can AR inspections be done in tunnels or indoors where GNSS cannot be received? A: Unfortunately, environments where satellites cannot be directly received cannot use RTK-GNSS positioning. However, as an alternative, AR displays can be aligned using known points or markers for tunnels and indoor environments. For example, in tunnel construction you can use a reference coordinate determined by GNSS near the entrance to calculate relative positions to known points inside the tunnel and place the AR model based on those reference points. Indoors, QR-code markers or feature-based (markerless) tracking technologies can also align models with the real space. In short, even without GPS you can perform AR inspections by tying the digital model to the real world using other references. Choose the appropriate alignment method for the site environment to enable AR-based inspection in tunnels and buildings.