Moving Beyond Manpower-Intensive Methods: Supporting Small Crews with AR As-Built Inspections

Contents

• Limits and challenges of manpower-intensive field operations

• What is AR as-built inspection?

• High-precision as-built checks that don’t miss mistakes

• Dramatic improvement in inspection efficiency and smooth consensus building

• Reliable quality proof through digital as-built records

• Labor reduction through simple surveying anyone can do

• Remote supervision and cloud sharing for on-site DX

• AR as-built inspection realized with LRTK simple surveying

• FAQ

Limits and challenges of manpower-intensive field operations

Many construction sites still rely on manpower-intensive approaches, deploying large numbers of personnel for as-built inspections and surveying tasks. However, as labor shortages worsen and the need to improve productivity increases, the limits of this approach have become apparent. Conventional as-built inspection methods have posed the following issues:

• Time-consuming and labor-intensive: Measurements were taken carefully point by point using surveying instruments and tape measures, and the results were recorded on paper. When measurement points are numerous across a wide site, measurement and drawing reconciliation can take several days.

• Dependence on skilled technicians: Accurate measurement and evaluation require experienced surveyors, and work often requires two-person teams. Chronic labor shortages and an aging technical workforce make it difficult to secure sufficient personnel at each site.

• High cost of dedicated equipment: Verifying deviations from design values to millimeter levels requires high-precision total stations (TS) or GNSS receivers, whose initial investment is very high and poses a barrier for small and medium-sized firms. Equipment maintenance costs and theft risk are also non-negligible.

• Risk of human error: Manual measurements are prone to recording or transcription mistakes. Sometimes missed measurement points are discovered later, requiring re-visits for re-measurement.

• Delayed problem detection: Inspections are often taken back to the office for judgment, so construction defects may not be noticed in time on site. For example, if insufficient concrete thickness or road gradient is noticed the next day or later, materials may have already hardened and major rework may be required.

• Burden of documentation: As-built inspections require preparing drawings and reports based on measurement results for submission to the client. Preparing these documents also takes time and effort, imposing a significant burden on site personnel.

Because of these problems, conventional as-built inspections are inherently inefficient and carry the risk of overlooking quality defects. To check as-built conditions precisely in real time, it is essential to move away from manpower-intensive methods and leverage digital technologies.

What is AR as-built inspection?

Against this backdrop, AR as-built inspection has attracted attention. By leveraging AR (Augmented Reality) technology, this new method overlays 3D design models and measurement data on smartphone or tablet camera images, allowing direct on-site verification of as-built conditions. Traditionally, measured values were taken back to the office for pass/fail judgment on drawings, but with AR, the actual object and digital design information can be compared on site, enabling even less-experienced technicians to intuitively judge the quality of the finish.

Combining AR with high-precision GNSS (satellite positioning) allows design models and data on AR to be accurately aligned to actual structures within a few centimeters (a few in). Smartphone + RTK-GNSS enables centimeter-level positioning (half-inch accuracy), so AR displays can be confirmed to match the real object without offset. Moreover, advanced uses—such as comparing point cloud data (many 3D points representing the as-built condition) obtained by LiDAR sensors in the latest iPhone or iPad with the design data and visualizing differences with color—are also possible.

The government is promoting the use of such digital technologies. The Ministry of Land, Infrastructure, Transport and Tourism aims in its “i-Construction 2.0” initiative to increase construction site productivity 1.5 times (30% reduction in labor) by fiscal 2040. It has also indicated a policy of actively trialing new construction management and inspection methods using 3D models and AR. As a solution that can simultaneously improve on-site efficiency and quality, AR as-built inspection is attracting strong expectations.

High-precision as-built checks that don’t miss mistakes

One major advantage of AR as-built inspection is that it enables high-precision checks that do not miss construction errors or slight deviations in the finish. Because design data can be overlaid on the camera image, subtle differences in elevation or insufficient thickness that are hard to spot with the naked eye can be visualized instantly.

For example, in road or earthwork filling, scanning the finished surface with a smartphone to obtain point cloud data and comparing it on site in AR with the reference design model makes surface irregularities and slight slope deviations immediately apparent. Displaying height differences as a color-coded heatmap lets you intuitively see “which point is how many centimeters higher/lower than the design.” This allows detection of mistakes that even experienced personnel might have overlooked, enabling early correction of quality defects.

AR visual checks also reduce human errors such as misreading numbers. Because the drawing and the actual object can be compared directly, inspection accuracy improves dramatically compared with relying only on numerical lists. Objects that become hidden after completion, such as buried pipes, can be confirmed after backfilling by AR-transparently displaying a previously scanned point cloud model. For example, if you record a 3D model before burying a sewer pipe, you can still see the pipe’s alignment and depth on a smartphone screen after pavement is finished, reducing the risk of accidental damage in later stages. In this way, AR as-built inspection captures even small deviations on site and greatly contributes to preventing quality problems.

Dramatic improvement in inspection efficiency and smooth consensus building

Introducing AR technology dramatically improves inspection efficiency. Because large areas can be measured in 3D at once, it is far quicker than conventional methods that measure one point at a time. Software automatically analyzes measurement results and makes pass/fail judgments, eliminating the need to do error calculations with a calculator or mark drawings with red pens on site. For example, using drone photogrammetry or an iPhone LiDAR scan, an as-built measurement of a slope that used to take half a day can sometimes be completed in tens of minutes. When acquired data is compared immediately in the cloud with the design model and deviations from standards are automatically highlighted, the inspector can understand the results on a tablet screen right there on site.

Furthermore, AR’s 3D visuals make the site situation clear to anyone, facilitating smooth consensus building (explanation and attendance) with clients and supervisors. Clients who previously only received numerical reports from the person in charge will have far greater satisfaction when they can see the difference between the completed form and the actual object through a tablet on site. Even for remote witnessing (remote inspections), sharing on-site AR images allows office staff to accurately grasp the situation, reducing communication loss. The visualization effect enables reliable consensus building with clients and dramatically streamlines the process to inspection approval.

Reliable quality proof through digital as-built records

Another key advantage of AR as-built inspection is that it enables comprehensive digitalization of on-site as-built records. Once point cloud data is acquired by 3D scanning, there is no “missed measurement” or “missed photo,” and construction results can be recorded comprehensively down to the smallest detail. While conventional as-built assessments often estimated results by measuring only a few key points, 3D data allows you to grasp the entire structure without omission.

The obtained high-precision point clouds and geotagged photos themselves become digital inspection evidence. If you automatically generate color-coded difference heatmaps and cross-section comparison diagrams, you can objectively prove compliance with standards later if questioned. Micro-level deviations that were hard to convey on paper drawings become obvious on a 3D model, improving the explainability of as-built management.

In addition, these digital records can be securely stored and shared in the cloud, making electronic delivery to clients easier. Automated generation of inspection reports reduces the clerical burden on site supervisors. When planning similar future projects, past as-built data can be used as reference material, enabling data-driven decision-making. Thus, digital quality proof through AR as-built inspection helps ensure long-term reliability and accumulation of technical know-how.

Labor reduction through simple surveying anyone can do

Modern AR as-built inspection tools run on smartphones and tablets, enabling simple surveying even by those unfamiliar with specialized equipment. Solutions like LRTK, a smartphone-based surveying system, allow high-precision positioning and 3D scanning simply by following app prompts, without complex setup or difficult calculations. New technicians can handle intuitive UIs and workflows, enabling as-built data acquisition and verification with consistent accuracy even when a licensed surveyor is not on site.

Because digital measurement records wide areas at once, it greatly reduces manual labor and staffing needs. If surveying that traditionally required two-person teams can be done by one person, labor costs and staffing logistics are reduced. There is no need to carry heavy equipment around the site, and time spent installing and dismantling equipment is also cut. As a result, limited personnel can manage multiple sites, and the physical and mental burdens on workers are reduced.

The time saved through labor reduction can be redirected to other quality control or safety management tasks. AR as-built inspection enables smart construction that does not rely on large crews or highly experienced personnel, making it a trump card for addressing worsening labor shortages.

Remote supervision and cloud sharing for on-site DX

Combining AR as-built inspection with cloud technology enables on-site DX (digital transformation) that allows remote understanding and support of construction sites. 3D point cloud data and AR footage acquired on site can be shared immediately with stakeholders inside and outside the company via the cloud, allowing supervision and verification of multiple sites in real time from the office.

For example, if site staff upload scanned point cloud models or live AR footage from a smartphone to the cloud, headquarters engineers or clients can check as-built conditions from the office. They can add comments to cloud data as needed or give remote instructions. With remote witnessing, inspections and meetings can be conducted without travel, reducing travel time and costs and speeding up decision-making.

Furthermore, as-built data accumulated in the cloud is always available as the latest information to all stakeholders. Sharing drawing files and point cloud models online eliminates time lags caused by “not having the latest data on hand” when making judgments. Information transfer between site and office, and between clients and contractors, becomes seamless, transforming construction management workflows. AR + cloud-based remote supervision will likely become the new standard for future smart construction sites.

AR as-built inspection realized with LRTK simple surveying

To maximize the benefits of AR as-built inspection, the underlying surveying and data-processing workflow is important. LRTK simple surveying is an all-in-one solution designed to make AR as-built inspection easy to practice.

LRTK is a smartphone-based high-precision positioning and measurement system; with a commercially available iPhone and a small GNSS receiver, surveying and as-built verification can be completed on site. RTK-GNSS enables centimeter-level positioning accuracy—horizontal ±1–2 cm (±0.4–0.8 in) and vertical ±3 cm (±1.2 in)—allowing locations to be identified with precision comparable to dedicated surveying equipment. Based on those high-precision coordinates, AR projection of design models and comparison with point cloud data can be performed on site. Stable AR displays without offset enable intuitive as-built checks that paper drawings cannot provide.

LRTK also includes a point cloud acquisition function that uses the iPhone’s built-in LiDAR sensor and camera. Even complex-shaped structures can be scanned with a smartphone to generate high-precision 3D point cloud models. Because the acquired point clouds are tagged with absolute coordinates derived from RTK-GNSS, they can be used on site immediately for comparisons with design data or for volume calculations. Also, if you record the coordinates of measured points, LRTK’s coordinate navigation (coordinate guidance) function becomes powerful: by following guidance on the smartphone screen, you can be guided to specified coordinate points within a few centimeters of error, making one-person staking that was previously difficult quite simple.

By providing AR display, point cloud acquisition, coordinate guidance, and as-built inspection on a single platform, LRTK simple surveying seamlessly connects tasks that previously required separate equipment and software. You can scan a point cloud on site, upload it to the cloud, and immediately check differences in AR—all within a single smartphone app—accelerating on-site DX. LRTK is already being adopted at construction sites across the country, contributing to faster disaster recovery and more efficient construction management. For those who want to try AR as-built inspection but don’t know where to start, LRTK makes it possible to start operations in a relatively short time. LRTK simple surveying, which balances the latest technology with ease of use, will be a strong ally for the small-crew sites of the future.

FAQ

Q: What do I need to introduce AR as-built inspection on site? A: Basically, you can get started with a tablet or smartphone, a high-precision GNSS receiver, and an application that supports AR as-built inspection. For example, solutions like LRTK enable centimeter-level positioning by attaching a small GNSS antenna to a commercially available iPhone or iPad, and you can handle 3D design data and point cloud data on a dedicated app. With design drawing data (BIM/CIM models or electronic drawings) and coordinates for site reference points prepared, you can start AR as-built inspection on site.

Q: Is the accuracy of AR-based as-built verification reliable? A: Yes—when used with high-precision GNSS, AR can achieve sufficiently reliable accuracy. Ordinary smartphone GPS has errors of several meters, but RTK corrections reduce errors to the level of a few centimeters. LRTK simple surveying has confirmed horizontal accuracy of about 1–2 cm, which is comparable to conventional Class-1 surveying instruments. Because the design model on AR aligns with the real object, step differences and gaps of a few centimeters (a few in) can be reliably detected. For critical parts, combining AR with point cloud measurement data enables millimeter-level precision verification (millimeter-level precision).

Q: Can AR as-built inspection be used for public works inspections? A: Currently, the Ministry of Land, Infrastructure, Transport and Tourism is actively promoting ICT construction and 3D as-built management, and AR technology use is being demonstrated in various locations. Trial projects have published examples where design models and as-built conditions are overlaid on a tablet AR screen for inspection. Although AR is not yet explicitly stipulated in formal inspection procedures, the combination of area management using point cloud data and remote witnessing has led to increasing cases where AR inspections are incorporated into site supervision and inspections. The ministry has indicated a policy of actively trialing new inspection methods that use 3D models and AR when proposed by contractors, and if guidelines are developed in the future, AR as-built inspection may become established as part of official inspection methods.

Q: Is operating AR as-built inspection difficult? Can young or inexperienced personnel handle it? A: Operation is intuitive, and young or digitally inexperienced personnel can usually handle it after a short training period. Measurements and AR displays can be done with the same feel as taking photos with a smartphone, so special surveying skills are not required. On-site data are preprepared design models and drawing files, so you simply select the file in the app and follow the instructions. Tools with thoughtfully designed UIs like LRTK simple surveying guide you through the process on-screen, enabling anyone to perform accurate as-built checks. Results are displayed visually, making them easy to understand and easy to share within the team.

Q: For what types of construction or sites is AR as-built inspection effective? A: It is effective wherever you want to verify discrepancies between design and construction results on site, in both civil engineering and building works. For large-scale earthworks such as roads and land development, AR heatmaps (color-coded as-built difference maps) are effective for managing heights over wide areas, and 3D model comparisons help check thickness and shape for large structures like tunnels and dams. In building construction, it can be used to compare the positions of columns and walls with BIM models during frame work or to check for piping clashes in advance with AR. In short, AR is effective at any site where you want to verify construction results on the spot. The greater the cost of re-measurement or rework, the larger the benefits of introducing AR inspection.