Know-and-Gain AR Inspection: New Technology That Simplifies As-Built Verification

In recent years, a new technology called AR inspection has been attracting attention at construction sites. This revolutionary method combines AR (Augmented Reality) technology with high-precision positioning to allow real-time verification of the as-built shape and dimensions of completed structures on site. By digitizing and streamlining the as-built inspections that used to require manpower and time, it is expected to greatly contribute to improved productivity in construction management and ensured quality.

This article explains in an easy-to-understand way what AR inspection is, how it works, and how sites will change after adoption. At the end, we also introduce solutions to help you start AR inspection easily.

Table of contents

• What is AR inspection (as-built inspection)?

• Conventional as-built inspection and its challenges

• Real-time as-built verification with AR × GNSS

• Example AR inspection workflow on site

• Ministry of Land, Infrastructure, Transport and Tourism initiatives and future trends

• Benefit 1: Precise inspections that don’t miss millimeter-level errors

• Benefit 2: Dramatic improvement in inspection efficiency and consensus-building

• Benefit 3: Digital as-built records and reliable proof of quality

• Benefit 4: Labor reduction via simple surveying anyone can use

• Benefit 5: Promote site DX with remote presence and cloud sharing

• Closing: How to start AR inspection easily

• FAQ

What is AR inspection (as-built inspection)?

As-built inspection is the process of verifying and recording that completed civil engineering and construction works or developed land have been finished in the shapes and dimensions specified by the design drawings. It is an important inspection item to ensure construction quality, and especially in public works, completion is not recognized unless the as-built inspection is passed. Traditionally, this inspection was performed by manual measurements using tape measures, staffs (measuring rods), levels, and photography, with results summarized in drawings and tables for reporting.

The recently introduced AR inspection (as-built AR check) incorporates AR technology into this as-built inspection. Specifically, design drawings and 3D model information are overlaid on the camera feed of a tablet or smartphone, allowing on-site direct comparison between the actual work and the digital design data. The visual effects of AR make it revolutionary in that even non-experts can intuitively judge acceptability of the finish. Especially when combined with high-precision GNSS (satellite positioning), the models and lines displayed in AR can be accurately superimposed on the real object with errors within a few cm (a few in), enabling immediate verification of as-built deviations on site.

For example, if reference lines or horizontal planes from the design are projected in AR on a completed development site, you can instantly tell whether the finish matches the specifications. Subtle ground undulations that used to be inferred by measuring a few points can be intuitively grasped on the spot with AR. In this way, the combination of AR × GNSS makes it possible to directly perform as-built verification on site that used to be done on paper drawings or numerical data, and the digitalization of as-built management is accelerating rapidly.

Conventional as-built inspection and its challenges

Several issues have been pointed out with conventional as-built inspections.

• Time-consuming and labor-intensive: Measuring as-built dimensions usually requires a team of two or more people, and on large sites with many measurement points the work can take a whole day. With a labor shortage, securing experienced surveying personnel and efficiently completing the work within the schedule is not easy.

• Dependence on skilled workers: Accurate measurement and judgment require experienced surveyors, but chronic labor shortages and an aging workforce mean that it is increasingly difficult to deploy sufficient personnel on site.

• Expensive equipment required: Achieving millimeter-level precision requires specialized surveying equipment such as total stations and high-precision GNSS receivers, which have high initial investment costs and entail maintenance costs and theft risks.

• Lack of coverage leads to oversights: Manual methods limit the number of physical points that can be measured, making it difficult to cover the entire construction area. Relying on a limited number of representative points may miss locations that deviate from the design.

• Risk of human error: Human errors such as forgetting to take photos or writing down measurement values incorrectly are common. If the site is busy, omissions in records may go unnoticed and lead to quality issues.

• Delayed problem detection: Traditionally, measurements taken on site are later checked against drawings in the office, so defects may be discovered some time after construction. This can result in large-scale rework, such as removing and re-pouring hardened concrete.

• Burden of report preparation: Compiling measurement results into drawings and photo ledgers requires significant paperwork and time. Time spent preparing inspection submission materials reduces time available for actual construction management.

Because of these problems, a method to manage as-built verification more efficiently and reliably has long been sought. Given recent labor shortages and work-style reforms, there is high expectation for using new technologies to improve productivity on site.

Real-time as-built verification with AR × GNSS

Previously, high-precision positioning required expensive surveying instruments, but recently the emergence of compact RTK-GNSS receivers that attach to smartphones and dedicated apps has made centimeter-level position accuracy accessible to anyone. RTK (Real Time Kinematic) GNSS positioning uses satellite signals together with correction information distributed from base stations to reduce positioning errors to within a few cm (a few in). Whereas fixed base stations and expensive receivers were once necessary, today real-time high-precision positioning is possible with just a smartphone and a small antenna.

When your position is known accurately, spatial registration with digital design data becomes realistic. By loading a design 3D model or drawing onto the smartphone screen and aligning it with the site’s coordinate system (survey coordinates), the virtual model is displayed perfectly over the real structure. A major feature of AR × GNSS is that the virtual model remains fixed in place without drifting even as the user walks around, allowing one-to-one direct comparison of the real structure and digital design information. This enables a workflow where you can check as-built compliance on-site in real time without returning to the office.

Furthermore, by utilizing LiDAR scanners and high-resolution cameras built into the latest smartphones and tablets, you can perform 3D as-is measurement on the spot. For example, you can scan the area you want to check with a smartphone to obtain point cloud data (a collection of many 3D measurement points), and by comparing that data in the cloud with the design 3D model you can automatically generate a difference heat map that shows deviations in color. If you import this heat map image into your smartphone and display it as AR over the real scene, you can see at a glance which places are higher or lower than the design by how many cm (in). Previously, point cloud data would be processed to create color-coded maps for submission and then the site would have to be referenced to find the relevant spots; thanks to AR, you can now see it directly on site.

In short, the fusion of AR and high-precision GNSS is turning the traditional process of “measure, record, and later compare with drawings” into real-time on-site verification. Surveying, as-built confirmation, and photo documentation can be completed with a single smartphone, and the acquired data is instantly shareable via the cloud so stakeholders can review results on the spot and move immediately to the next action. This technological innovation can dramatically improve on-site productivity and quality control.

Example AR inspection workflow on site

So how is as-built inspection using AR actually performed on site? Taking civil engineering work as an example, let’s follow the typical flow.

• Preparation (prepare design data): First, prepare design drawings or 3D model data of the work target in digital form. BIM/CIM models or CAD data are ideal because they include information about the finished shape and reference lines/planes. Load these data into a dedicated app and pre-align them with the site’s survey coordinate system. The use of BIM/CIM has advanced in many projects, making digital design data increasingly available.

• Equipment setup: Next, attach an RTK-capable GNSS receiver to a smartphone or tablet on site to enable high-precision positioning. In Japan, the quasi-zenith satellite system “Michibiki” provides centimeter-level positioning augmentation services (CLAS), and network RTK base station services via the internet make it possible to obtain correction information without preparing your own base station. Once positioning stabilizes, launch the app’s AR display mode and, if necessary, calibrate the device’s orientation sensors (electronic compass).

• As-built verification: For instance, to check the height of a development site, display a virtual horizontal plane corresponding to the design finish height in AR. The smartphone screen overlays a transparent “design height reference plane” on the site imagery, allowing the operator to walk around and verify whether the actual ground is higher or lower than the virtual plane. Where the virtual plane appears to float above the ground, fill is insufficient; where it appears submerged into the ground, there is excess fill. Likewise in roadworks, you can project design longitudinal and cross-section profiles in AR to verify pavement thickness and slopes on the spot.

• Real-time corrective instructions: If AR reveals deviations in the finish, share the information with workers on site and immediately proceed to correction work. For example, if the AR screen shows “this point is 5 cm low,” you can add soil right away. Numerical guides displayed in AR (e.g., “+5 cm fill”) and color-coded displays are intuitively understood by workers and clearer than verbal instructions, minimizing rework while progressing construction.

• Data recording and reporting: After inspection, record and save the check results as data. Photos with coordinates taken by the smartphone are uploaded to the cloud along with shooting position and orientation information, allowing office staff to review site conditions remotely. If point cloud scanning was performed, some systems can generate as-built heat maps and as-built management charts with one click. These digital deliverables can be organized and submitted as reports to the client.

Through the flow above, AR × GNSS as-built inspection enables an integrated digital process from on-site verification and correction through to final record creation. Compared with conventional methods using field notebooks and tape measures, this is a dramatically streamlined workflow.

Ministry of Land, Infrastructure, Transport and Tourism initiatives and future trends

Even though AR-based as-built inspection is a cutting-edge technology, it is not just an ad-hoc idea from sites. The Ministry of Land, Infrastructure, Transport and Tourism (MLIT) is proactively promoting ICT utilization in construction management and officially supports digitalization of as-built management.

As part of the *i-Construction* initiative, MLIT has developed the “as-built management guidelines (draft)” using 3D measurement technologies such as BIM/CIM, drone photogrammetry, and terrestrial laser scanners, and has been improving new as-built measurement methods. In April 2022 the “As-Built Management Guidelines” were revised to formally allow the use of simple mobile devices such as smartphones for as-built measurement in public works. This made smartphone-based 3D as-built management possible even without expensive dedicated equipment, lowering the barrier for introducing ICT construction at small- to medium-sized sites.

Furthermore, in 2024 MLIT began trials on MLIT-managed projects of supervision and inspection methods that utilize digital data, in which a new inspection flow is shown: “project-created 3D models are projected on site with AR technology and on-site as-built measurement is conducted.” This officially adopts the AR as-built inspection concept, and if standards are developed based on trial results, AR as-built inspection may become established as one of the formal inspection methods.

With administrative support like this, AR inspection is gaining recognition not as a gadget-like experiment but as a technology that could become a construction site standard.

Benefit 1: Precise inspections that don’t miss millimeter-level errors

One of the biggest benefits of AR as-built inspection is that it can detect construction errors and slight deviations in finish at the millimeter level (≈0.04 in). By overlaying design data on camera imagery, subtle height differences or insufficient thickness that are hard to notice with the naked eye are immediately visualized. Small undulations or unevenness that even experienced workers might miss are revealed by AR color-coding and comparison with reference lines, enabling early correction. As a result, the risk of being later pointed out for construction defects is greatly reduced, helping prevent quality problems.

Also, unlike checking numbers on drawings against the actual object, AR’s visual checks reduce mistakes caused by human misreading or misinterpretation. Because you can view the real object and digital information side by side, AR inspections are far more reliable than number-only checks. Moreover, buried structures that will be invisible after completion can be confirmed by AR showing pre-scanned point cloud models. For example, if you scan and record the location of sewer pipes before backfilling, you can later visualize the pipe alignment and depth on a smartphone even after paving is complete, reducing the risk of accidental damage in subsequent work. In this way, AR as-built inspection captures minute irregularities on site and greatly contributes to preventing quality issues.

Benefit 2: Dramatic improvement in inspection efficiency and consensus-building

Using AR dramatically improves the efficiency of as-built inspections. Because wide areas can be measured in 3D at once, it is vastly faster than measuring point by point. Software automatically analyzes measurement results and can even make pass/fail determinations, significantly reducing inspection time. For example, using drone photogrammetry or iPhone LiDAR scanning, tasks such as slope as-built measurement that used to take half a day can sometimes be completed in tens of minutes. Even on large-scale projects with many measurement points, AR inspection can cover the entire site in a short time.

Furthermore, AR’s intuitive 3D display dramatically smooths consensus-building on site. Contractors and clients can look at the tablet’s AR screen together and confirm the finish on the spot, sharing recognition in real time without waiting for later written reports. For example, showing as-built deviations in AR makes “which spots need how much correction” instantly understandable to both parties, allowing immediate agreement on corrective actions. Things that are hard to convey with drawings or numbers alone become easy to explain by sharing AR imagery, streamlining communication with clients and supervisors and reducing the effort needed for explanations and deliberations. This efficiency and smoother communication greatly shorten the total time required for inspections and site attendances.

Benefit 3: Digital as-built records and reliable proof of quality

Introducing AR inspection means as-built management records are stored as digital data from the outset. Information that used to be organized in paper forms and photo ledgers is now automatically saved as coordinate-tagged measurement points, point cloud models, AR overlay screenshots, and so on, greatly reducing the risk of missing or losing records. 3D as-built data uploaded to the cloud can be shared by all stakeholders and accessed whenever needed. The labor of filing large numbers of photos and measurement results at project completion is also reduced, making data management smarter.

Digital as-built records also serve as reliable proof of quality. High-precision point clouds and AR overlay images acquired on site are objective evidence that “the as-built meets the design standards.” For example, providing images that overlay the design model on the completed structure or AR screens that show numeric errors at each measurement point makes it easy to demonstrate construction accuracy. Such data are persuasive as reports to clients and provide assurance as proof of passing inspections. Many AR-capable apps can automatically generate as-built management charts and reports from measurement data, further reducing paperwork. Human entry errors decrease and content reliability improves. In short, AR inspection digitally secures and reliably proves the site’s “visible quality.”

Benefit 4: Labor reduction via simple surveying anyone can use

The main equipment needed for AR as-built inspection is a smartphone and a small GNSS receiver, and because operation follows on-screen instructions in a dedicated app, it is easy to use without special skills. Even young engineers unfamiliar with surveying or ICT can perform measurements and AR displays with the same ease as taking photos on a smartphone. The actual steps are simple: point the antenna-equipped smartphone at the location to measure and press a button, or select the model data from the menu and overlay it. While some familiarity with mounting equipment and calibration is required at first, short training enables anyone to use the system intuitively. Because advanced surveying knowledge is not required, this approach effectively addresses on-site staff shortages and skill transfer challenges.

Another major advantage is that surveying and as-built verification work that previously required 2–3 people can be completed by one person. There is no need to carry heavy equipment or coordinate with assistants—site personnel can quickly measure as-built conditions with a smartphone in hand. This enables labor and manpower savings, allowing efficient site management even with limited personnel. In severe labor shortage conditions, a system that allows “anyone, alone” to perform as-built checks becomes a trump card for productivity. It raises the whole organization’s baseline by enabling everyone on site to participate in quality control without relying solely on experts.

Benefit 5: Promote site DX with remote presence and cloud sharing

Combining AR as-built inspection with cloud services enables real-time information sharing between site and office. Point cloud data, photos, and inspection results obtained with a smartphone are uploaded to the cloud on the spot and can be shared immediately with remote stakeholders. The time lag caused by “taking data back to the office because the latest data is not available on site” disappears, making information flow between site and headquarters, and between contractors and clients, seamless. This digitally transforms construction management workflows and contributes to site DX (digital transformation).

AR-visualized as-built information can also be used for remote presence. Without traveling to the site, supervisors and engineers can review AR imagery and analysis data from the office to provide instructions or confirmations, enabling efficient management where one supervisor can oversee multiple sites. For example, a client or manager could check the AR screen shared by a site operator during an online meeting. MLIT actively promotes remote presence, and AR inspection can be a powerful tool for that purpose. By enabling stakeholders to experience site conditions as they are regardless of distance, AR-based remote inspections may become the standard for smart construction sites in the future. In this way, AR and cloud utilization remove site boundaries and greatly contribute to improving productivity in the construction industry.

Closing: How to start AR inspection easily

The use of AR technology for as-built inspection is currently revolutionizing on-site productivity and quality. Those who think “I’m interested, but implementation seems difficult…” may be reassured to know that recently all-in-one surveying systems that make AR as-built inspection easy to start have appeared. A representative example is LRTK.

LRTK is a solution developed by a venture originating from Tokyo Institute of Technology and consists of a pocket-sized RTK-GNSS receiver that can be attached to an iPhone and a dedicated app. It is designed so that surveying and verification can be completed with just a smartphone, and technicians without special training can operate it intuitively. With LRTK, simply pointing an antenna-equipped smartphone at the point to measure and tapping a button records high-precision coordinates, and selecting and overlaying design data from the menu performs AR as-built checks on the spot. Its simple surveying features are devised so anyone can quickly use centimeter-level (half-inch-level) positioning, point cloud scanning, and AR as-built verification.

LRTK series products have already been introduced at construction sites nationwide and have contributed to speeding up disaster recovery work and improving construction management efficiency. They are the latest tools compatible with MLIT’s i-Construction initiative and can be powerful allies for promoting DX at your sites. Even those who don’t know where to start with AR inspection can relatively quickly adopt and operate products like LRTK. Consider actively embracing these latest technologies and stepping into new site management through smart construction.

FAQ

Q: What do I need to introduce AR as-built inspection on site? A: Basically, you can perform AR as-built inspection with a tablet/smartphone, a high-precision GNSS receiver, and a dedicated app that supports AR as-built inspection. Prepare digital design data such as drawings or BIM/CIM models in advance and load them into the app. It is convenient if the GNSS receiver can receive correction information (RTK) via the internet. For example, solutions like LRTK achieve centimeter-level positioning by attaching a small antenna to a commercial iPhone and allow handling of 3D design data and point clouds in a dedicated app. If you prepare site reference point coordinates, anyone can start AR inspection directly with a smartphone.

Q: What level of measurement accuracy can be achieved? A: With AR systems combined with high-precision GNSS, you can obtain reliably accurate measurements within a few cm (a few in). Built-in GPS on ordinary smartphones has errors on the order of meters, but RTK corrections can reduce errors to a few cm (a few in). In actual LRTK simple surveying, horizontal positioning accuracy of approximately 1–2 cm (0.4–0.8 in) and vertical accuracy of about 3 cm (1.2 in) have been confirmed, reaching levels comparable to traditional first-class surveying instruments. Because AR displays align precisely with the real object, differences and gaps on the order of a few cm (a few in) can be reliably detected. For critical areas, combining AR display with point cloud measurement data enables strict millimeter-level (≈0.04 in) verification.

Q: Can AR be used in public works inspections? A: At present, AR use is not explicitly specified in the as-built management guidelines, but MLIT actively promotes ICT construction and 3D as-built management, and AR as-built inspection is being trialed in various locations. There have been trial implementations in MLIT-managed projects where design models are overlaid on tablet AR screens to check as-built conditions. If guidelines are developed in the future, AR inspection could be recognized as one of the formal inspection methods. Even now, AR can be used as an auxiliary tool for voluntary on-site inspections and for supervision/attendance to pre-check as-built compliance, which is expected to facilitate smoother inspections.

Q: Is the introduction cost high? A: It is considerably lower cost than purchasing dedicated large surveying instruments. Many people already own smartphones or tablets, and small GNSS receivers are less expensive than total stations. Software is often provided as a cloud service with flexible licensing for the required period. More importantly, the cost benefits from reduced working time and personnel requirements are significant, and the total return often exceeds the investment. With lower initial investment and productivity gains, the cost-effectiveness is attractive.

Q: Can people without special skills use it? A: Yes. Basic operations are not difficult if you follow the on-screen guidance in the app. For example, with systems like LRTK, just point the antenna-equipped smartphone at the point to measure and press a button to record coordinates, and overlay models from the menu to display AR. Some familiarity with equipment handling is needed, but after short training or trial use it can be mastered. Repeated use on site helps build intuition. Even IT-averse veteran workers can operate it with a smartphone-app feel, and because results are visually displayed, acceptance and shared learning within the team are easy.

Q: What if GNSS cannot be used at the site? A: Unfortunately, pure GNSS-based AR cannot be used as-is in locations without sky view, such as tunnels or indoor spaces. In such cases, you can use alternative references for AR registration. For example, in tunnels you can perform GNSS positioning at a known point near the entrance and then align the underground positions relative to that reference, or use markers installed inside the tunnel to correct the AR model. Indoors, QR code markers or distinctive wall features can be used to estimate site coordinates and overlay AR. In this way, even where GNSS does not reach, AR-based as-built verification can be implemented using known points or markers.