Will AR As-built Inspection Be the Norm in Five Years? The Future of Construction DX Opened by AR As-built Inspection

Table of Contents

• What is AR as-built inspection

• Challenges of traditional as-built inspection

• How as-built inspection evolves with AR technology

• Promotion of construction DX and national trends

• Benefits of AR as-built inspection

• Will AR as-built inspection be the norm in five years?

• How to get started with AR as-built inspection

• FAQ

What is AR as-built inspection

As-built inspection in civil engineering and construction is an important process that verifies whether completed structures and terrain match the design in shape and dimensions. Especially for public works, the results of as-built inspections are essential for inspection approval and handover, making them indispensable for quality control. Traditionally, these inspections have been carried out by manual measurements using tape measures, leveling staffs, and levels, along with photographic documentation. However, manual methods make it difficult to measure an entire large site, require considerable time and manpower, and carry an unavoidable risk of overlooking areas that cannot be measured.

Against this backdrop, a new inspection method that has attracted attention in recent years is AR as-built inspection. By combining AR (Augmented Reality) technology with high-precision GNSS positioning, this system allows on-site, real-time checks of as-built conditions, significantly advancing as-built inspections through digital technology. Specifically, design drawings and 3D model information are overlaid onto the real construction site through the camera of a smartphone or tablet, enabling intuitive, on-the-spot visualization of discrepancies between the actual construction and design data. For example, if design lines or shapes are projected in AR over a newly paved road or embankment terrain, you can immediately judge whether the finish falls within the prescribed range. This is made possible by RTK-GNSS (real-time positioning) that offers centimeter-level positioning accuracy (cm level accuracy (half-inch accuracy)), and by the various sensors built into smartphones. By combining AR and GNSS, the digitalization of as-built inspections is beginning to be realized at the field level. Although this approach is still new, it may soon become commonplace on sites and become one of the technologies supporting construction DX.

Challenges of traditional as-built inspection

Many problems have been pointed out with the traditional, manual-centered as-built inspection. The main issues include:

• Manpower and time burden: Measuring finished dimensions typically requires a team of multiple people, and on large sites there can be so many measurement points that the work takes a whole day. Including office work to organize measurement data into drawings and tables, this creates a significant burden on site engineers.

• Oversights due to lack of coverage: Manual methods limit the number of physically measurable points, making it difficult to cover the entire construction area. Because only a small number of representative points can be checked, there is a risk of overlooking areas that differ from the design. The larger the structure, the harder it is to grasp fine deviations or irregularities, which can lead to sudden corrective work if a discrepancy is pointed out during inspection.

• Risk of human error: In busy sites, human mistakes such as forgetting to take photos or writing measurement values incorrectly can occur. If parts that will later be hidden, such as buried items, are not recorded, it may become impossible to prove them after completion. Such mistakes have led to quality issues, and the traditional methods always carried this concern.

How as-built inspection evolves with AR technology

The key to solving these issues is the fusion of AR technology and high-precision GNSS positioning. By attaching a dedicated compact RTK-GNSS receiver to a smartphone and using a compatible app, anyone can now obtain centimeter-level positioning information in real time. RTK (Real-Time Kinematic) GNSS is a technology that reduces positioning errors to a few centimeters or less through correction data from a reference station; previously it required expensive surveying equipment, but it is now available conveniently on smartphones.

If you can know your position with high accuracy, spatial matching with design data can be done instantly. By loading BIM/CIM 3D models or electronic drawing data into an app in advance and aligning them with the site coordinate system, those data can be overlaid at accurate positions on the smartphone camera view. For example, when you point your smartphone, the designed final shape or reference lines appear to align perfectly with the real scene ahead. Because GNSS keeps the display synchronized with real-world coordinates, the virtual model follows without shifting even as the user moves. As a result, you can directly compare digital design information with the actual object on site, and instantly confirm whether the as-built condition meets the standards.

Furthermore, by utilizing built-in LiDAR scanners or high-resolution cameras in smartphones, it is also possible to perform on-site 3D measurement of as-built conditions. For example, you can scan the area you want to check with a smartphone to acquire point cloud data (3D data composed of many measurement points), then automatically compare it with the design model in the cloud to generate a heat map (error distribution map). If the heat map showing areas of excess and deficiency in the as-built condition is sent back to the smartphone and displayed in AR over the site scene, you can immediately see which locations deviate from the design and by how much. Because nonconforming areas can be identified on the spot, corrective work such as additional filling or excavation can begin immediately. Traditionally, point cloud analysis produced difference maps on plan drawings which then required locating the relevant areas on site; AR has enabled a workflow of "direct on-site verification."

In this way, AR×GNSS technology is transforming the as-built inspection process from a retrospective model of "measure, then organize and report at the office" into a process that can be completed in real time on site. Surveying, as-built confirmation, and recording can be done with a single smartphone, and the data obtained are immediately shared in the cloud, allowing stakeholders to confirm the finish on the spot and proceed with decisions for subsequent work. This can be seen as a technological innovation that dramatically improves productivity and quality control on site.

Promotion of construction DX and national trends

Even though it is cutting-edge technology, AR as-built inspection is not an outlandishly unconventional method. The Ministry of Land, Infrastructure, Transport and Tourism (MLIT) has been actively promoting the use of ICT in construction management and officially supports the digitalization of as-built management. In fact, as part of the *i-Construction* policy, MLIT has promoted the introduction of BIM/CIM and 3D measurement technologies. In particular, it has formulated the "Guidelines for As-built Management Using 3D Measurement Technologies (draft)" and organized as-built measurement methods using drone photogrammetry and terrestrial laser scanners. Furthermore, in 2022 the as-built management guidelines were revised to officially permit the use of simple mobile devices such as smartphones as as-built measurement instruments for public works. This change makes smartphone-based 3D as-built management increasingly feasible even on small- to medium-sized sites without expensive dedicated equipment.

In addition, in 2024 trials began in MLIT-managed construction projects to use digital data for supervision and inspection, and among those trials a new method was presented: "projecting the 3D models created during the construction stage onto the site using AR technology and conducting on-the-spot as-built measurements." The aim is to replace the previous process—creating heat maps from point cloud data and submitting them, then re-measuring on site during inspections—with AR-based on-site verification to improve efficiency. Such public- and private-sector-driven digital transformation (DX) of construction sites is underway, and as-built inspection using AR×GNSS aligns well with that trend.

More recently, the principle application of BIM/CIM has begun for almost all MLIT-managed projects. As 3D design data are prepared in many projects, the digital information available for AR use will increase dramatically. As data linkage automation becomes widespread, smart construction that does not rely on paper and manual work will begin to penetrate as-built management sites.

Benefits of AR as-built inspection

Introducing AR as-built inspection brings various advantages to the field. The main benefits are as follows:

• Significant efficiency improvements and labor reduction: Surveying and inspection work that previously required two or more people can be completed by one person, boosting productivity even on sites with labor shortages. Waiting for surveying that halts construction is reduced, and because measurements and confirmations can be made when needed, construction progress is smoother.

• Quality improvement through high-density measurement: Point cloud scanning and continuous measurement enable high-density measurement over wide areas, providing areal as-built awareness. Small irregularities or dimensional variations are less likely to be overlooked, reducing variability in construction quality. The reassurance of covering the entire site with data is a major quality-management benefit for both owners and contractors.

• Real-time correction and reduced rework: Because inspections can be performed immediately after construction on site, situations where nonconformance is discovered only during later inspections can be prevented. "Check on site, correct on site" becomes possible, and early detection and immediate response to mistakes greatly reduce rework and schedule delays. This also contributes to suppressing unnecessary costs.

• Intuitive and easy-to-understand communication: AR-visualized information is more intuitive than reports that rely solely on numbers and documents. If all stakeholders on site share the same AR view through their smartphone screens, it becomes immediately clear "which areas and to what extent need correction." Recognition sharing and consensus-building among workers and supervisors become smoother without relying on veteran intuition and experience.

• Easier data recording, sharing, and knowledge transfer: Because measurement data and photos are all digitally stored and shared, the workload for creating forms and reports is reduced. As-built data centrally managed in the cloud can be used for future maintenance and repair work. Also, the skills and site knowledge of experts can be preserved as data, helping to transfer know-how that tends to be person-dependent.

• Improved safety: AR-enabled remote measurement can reduce work in dangerous locations. On slopes or at heights, AR markers can be set up and guided from a safe distance, reducing the need for workers to adopt dangerous postures for surveying. AR guidance can also reduce contact risks during piling or marking in areas with operating heavy machinery, contributing to overall site safety improvement.

As described above, AR as-built inspection is not merely a novelty of a new technology but has practical benefits that directly address site issues. With the construction industry facing increasing aging and labor shortages, AR as-built inspection is expected to spread widely as a trump card that balances efficiency and quality.

Will AR as-built inspection be the norm in five years?

Given these trends, it would not be surprising if AR as-built inspection becomes the "norm" on sites in just a few years. From a technical standpoint, advances in devices and communication environments will lead to the widespread adoption of even easier-to-use and higher-performance AR solutions. For example, if lightweight smart glasses–type AR devices become practical, workers may be able to continually check AR information while using both hands during tasks.

In fact, there are already increasing on-site examples such as AR systems that enable a single person to perform rebar placement inspection and software that projects point cloud heat maps onto the site to check as-built conditions. As these success cases accumulate, the reliability and usefulness of AR as-built inspection will become better known and accelerate adoption.

Also, by the late 2020s it is expected that most construction projects will have 3D design and construction data in place, and that digital twins and AI-based quality control will be widespread. In such an environment, AR as-built inspection will be a natural means as part of data linkage. The retirement of veteran generations combined with the rise of digitally native younger workers will further accelerate on-site digital transformation. Because AR as-built inspection can achieve both excellent efficiency and reliable quality assurance, it is highly likely to be commonly used at sites in five years.

How to get started with AR as-built inspection

AR-based as-built inspection used to require specialized, expensive equipment and was a leading-edge experiment, but today simple solutions combining a smartphone and a compact GNSS receiver are emerging. For example, in a system called LRTK, a pocket-sized RTK-GNSS antenna that can be attached to a smartphone and a dedicated app can transform the site environment so that "surveying and inspection can be completed with just a smartphone." Even general technicians without special training can operate it intuitively and immediately utilize high-precision positioning, point cloud scanning, and AR-based as-built confirmation with simple surveying functions.

By leveraging such tools, AR as-built inspection—previously difficult to introduce—becomes something anyone can practice in routine work. With a single smartphone you can seamlessly measure, record, compare, and share, enabling digital construction management even on small sites or with limited personnel. The important thing is to try using it on site first. You will realize how surprisingly easy it is to digitize tasks that relied on paper drawings and tape measures. AR×GNSS as-built inspection is not some distant future technology but a familiar tool already usable on site. Why not take this opportunity to start simple smart construction at your site?

FAQ

Q: Can the accuracy of AR as-built inspection on site be relied upon? A: With AR combined with high-precision GNSS (RTK-GNSS), positional accuracy can be secured to a few centimeters. Standard smartphone GPS has errors on the order of meters, but with RTK corrections you can measure your position at a level comparable to surveying reference points, so AR overlays align with minimal offset. In addition, if the smartphone’s gyroscope and electronic compass are properly calibrated, heading accuracy is sufficient for practical use.

Q: What preparations and equipment are needed to display AR on site? A: Basically, a smartphone (or tablet), an RTK-capable GNSS receiver, and a dedicated AR app are sufficient. Prepare design data in advance (BIM/CIM 3D models or digital drawing data) and load them into the app. It is convenient if the GNSS receiver can receive correction information (RTK data) via the internet. Outdoors with radio coverage, you can use existing correction services without having to install your own base station.

Q: How do you perform AR as-built inspection in environments where GNSS cannot be received, such as inside tunnels or indoors? A: Unfortunately, pure GNSS positioning cannot be used where there is no sky view. In such cases, you can install known points (reference markers) as AR markers or perform position alignment using pre-measured reference points. For example, in a tunnel you can use coordinates obtained from GNSS positioning near the entrance as a basis to relatively correct positions against interior reference points, and then display AR accordingly. Indoors, QR codes or feature-point markers are sometimes used for AR alignment.

Q: Doesn’t introducing AR as-built inspection incur costs? A: It can be started at a significantly lower cost than purchasing dedicated large equipment. Many people already have smartphones, and the cost of introducing small GNSS receivers and software is lower than traditional surveying equipment. Above all, the time savings and labor reductions bring significant cost benefits, and overall the expected effect often exceeds the investment.

Q: Can AR as-built inspection alone be used to complete final inspections and document submission? A: At present, AR is primarily a tool to streamline on-site verification. For public works, traditional deliverables such as as-built drawings and photo logs are still required, so you will need to prepare records that compile measurement data. However, some AR tools can automatically generate heat maps and reports from point cloud data, greatly reducing the burden of document preparation. In national trial initiatives, proposals have been made to substitute AR on-site verification for some inspection processes, and in the future it is expected that AR screen records might be accepted directly as inspection records.

Q: Can anyone quickly master AR as-built inspection? Is special skill not required? A: Basic operations are not difficult if you follow the app guidance. For example, in systems like LRTK, you can record coordinates simply by holding the antenna-equipped smartphone over the point you want to measure and pressing a button, and AR displays are overlaid by selecting model data from the menu. Even those without specific surveying qualifications can handle it intuitively, and with a little practice they can make full use of it on site.