i-Construction Ready! Greatly Boost Work Efficiency with AR As-Built Inspections

Table of Contents

• What is AR as-built inspection?

• Challenges of conventional as-built inspections

• Benefit 1: Millimeter-level checks that don’t miss mistakes

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

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

• Benefit 4: Labor savings with easy surveying anyone can use

• Benefit 5: On-site DX with remote use and cloud sharing

• Start AR as-built inspection with simple surveying using LRTK

• FAQ

What is AR as-built inspection?

As-built inspection (as-built management) is an important quality control process in civil engineering and construction that verifies whether completed structures or developed land conform to the design shapes and dimensions. Especially in public works, as-built inspection results often determine acceptance and handover, so reliable as-built management is required. Conventionally, measurements at key points such as heights and thicknesses were taken using instruments like total stations, levels, and tape measures, recorded on paper, and then brought back to the office to compare with drawings for pass/fail judgments. However, this approach tends to create time lags between on-site measurement and problem discovery, often causing rework. Surveying work also relies heavily on the experience and intuition of skilled technicians, and with chronic labor shortages and an aging workforce among technicians, improving efficiency has become a pressing issue.

Against this background, a new method attracting attention in recent years is the so-called “AR as-built inspection.” By leveraging AR (Augmented Reality) technology to overlay 3D design models and measurement data on the camera feed of a smartphone or tablet, you can verify as-built conditions directly on site. Because as-built checks that were previously done on paper drawings or numerical data can now be compared on the spot with the real object and digital information side by side, even less experienced technicians can intuitively judge whether the finish is acceptable.

In particular, when combined with high-precision GNSS positioning, it is possible to accurately align 3D models or measurement data in AR with actual structures to within a few centimeters (a few inches) of error. Smartphone + RTK-GNSS receivers make centimeter-level (half-inch accuracy) positioning possible, so AR displays can coincide with the real object without noticeable shifts. Furthermore, the latest iPhones and iPads include LiDAR scanners, which enable advanced use such as comparing point cloud data of the current condition captured with LiDAR to design data to visualize differences. The Ministry of Land, Infrastructure, Transport and Tourism is also promoting the use of 3D measurement and AR technologies as part of the i-Construction initiative, and AR as-built inspection is increasingly expected as a solution that simultaneously improves on-site productivity and quality.

Challenges of conventional as-built inspections

Conventional as-built inspection methods had the following problems:

• Time-consuming and labor-intensive: Measurements at each point had to be taken one by one with surveying instruments or tape measures, and results were recorded on paper. On sites with many measurement points, completion could take several days.

• Dependence on experienced personnel: Accurate measurement and judgment require experienced survey technicians, and work is often done in pairs. With worsening labor shortages and aging technicians, it has been difficult to secure sufficient personnel at all times.

• Expensive equipment required: Evaluating deviations from design values to the millimeter level requires high-performance total stations or GNSS surveying equipment, but initial investment is very high, creating a barrier for small and medium-sized companies. Maintenance costs and theft risk of equipment are also non-negligible.

• Risk of human error: Manual measurements are prone to human mistakes like incorrect note-taking or transcription errors later. There are also cases where omitted measurement points are noticed later, requiring a return trip to re-measure.

• Delayed problem discovery: Inspections are typically performed back at the office, so construction defects may not be detected on the spot and could become too late to correct. For example, if insufficient concrete thickness or improper roadbed slope is noticed the next day or later, the material may have already hardened, and corrections could become extensive.

• Paperwork burden: As-built management requires measurement results to be compiled into drawings and reports to submit to the client. Creating these documents takes time and effort, placing a heavy burden on responsible staff.

Because of these issues, conventional as-built inspection tends to be inefficient and risks overlooking quality problems. To perform precise, real-time as-built checks, it was essential to adopt new technologies that could solve these problems.

Benefit 1: Millimeter-level checks that don’t miss mistakes

One major advantage of AR as-built inspection is that it can detect construction mistakes and finish deviations down to the millimeter (≈0.04 in) so they won’t be missed. By overlaying design data on the camera image, subtle height differences or insufficient thicknesses that are hard to notice with the naked eye are immediately visualized. For example, in road embankment work, scanning the finished ground surface with a smartphone to obtain point cloud data and comparing it to the design reference model in AR makes surface irregularities and minor slope defects instantly obvious. If differences in elevation are displayed as a color-coded heat map, you can intuitively see “which points are how many centimeters higher (or lower) than the design.” As a result, errors that even experienced personnel might overlook can be reliably detected, enabling early correction of quality issues.

AR visual checks also reduce human errors such as misreading numbers. Because drawings and the real object can be overlapped and checked, inspection accuracy improves dramatically compared to inspections that relied only on numerical values. Objects that cannot be visually confirmed after completion, such as buried pipes, can be confirmed even after backfilling by previously 3D-scanning a point cloud model and displaying it transparently in AR. For instance, if the position of sewer piping is recorded before burying, you can see the pipe alignment and depth on the smartphone screen even after paving, reducing the risk of accidental damage in later processes. In this way, AR as-built inspection captures even minor deviations and contributes significantly to preventing quality troubles.

Benefit 2: Dramatic improvement in inspection efficiency and consensus building

Using AR dramatically improves the work efficiency of as-built inspections and speeds up consensus building with clients and supervisors. Because it is possible to perform wide-area 3D measurement at once, it can save considerable time compared with the conventional point-by-point approach. In addition, software can automatically analyze measurement results and determine deviations from the design, reducing the effort required for data organization and pass/fail judgments.

Moreover, the visualization effect of AR allows all stakeholders to understand the results on the spot. Without waiting to return to the office to submit reports, you can confirm the AR overlay of the design model and the current condition together with the client or inspector at the site, achieving immediate common understanding about quality. If issues are found, they can be pointed out and corrected on the spot; if acceptable, the inspection can be passed right away. This ability to form consensus while viewing the real object makes the process much smoother than before. Such real-time information sharing simplifies the inspection process and improves communication with clients.

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

AR as-built inspection also stands out for digitizing on-site as-built records entirely and serving as reliable proof of quality. Once 3D point cloud data is captured, there is no “forgotten measurement” or “missed photo”; the construction results can be recorded comprehensively down to every detail. Whereas conventional practice extracted and measured only important locations, 3D data enables a complete understanding of the entire structure and prevents oversights due to partial measurements. Measurement date/time and location information can be associated with the data, making it clear who measured where and when.

Digitized as-built data itself becomes solid evidence. If measurement results and site conditions are stored in the cloud with photos, you can explain the situation later based on the data if quality is questioned, and the data can be used as inspection material. Also, because records can be stored and shared electronically, the time and effort of producing paper drawings and reports are greatly reduced. In fact, trials have begun where the submission of traditional as-built management charts (as-built deliverables) can be omitted when on-site pass/fail judgments are made using AR. Digitizing records streamlines reporting work, enabling reliable quality assurance and paperless processes simultaneously.

Benefit 4: Labor savings with easy surveying anyone can use

The latest AR as-built inspection tools run on smartphones and tablets, enabling easy surveying that even people unfamiliar with specialized surveying instruments can use. For example, solutions like the smartphone-based positioning system LRTK allow high-precision positioning and scanning simply by following the app’s instructions without worrying about complex settings or calculations. They feature intuitive UIs that even novice technicians can use, enabling data acquisition without relying on veteran surveyors.

When anyone can perform precise surveying and measurement, required personnel can be greatly reduced. Tasks that traditionally required two people—such as stake setting and as-built confirmation—can increasingly be handled by one person carrying a tablet, directly translating to labor savings. This makes it feasible to maintain high-quality construction management even on sites with personnel shortages, contributing to work-style reforms and skill succession. Easy surveying tools that do not require specialized knowledge enable everyone to use digital measurement on site.

Benefit 5: On-site DX with remote use and cloud sharing

Data obtained from AR as-built inspections can be shared instantly via the cloud, allowing remote monitoring of site conditions. If point cloud data scanned on site or AR comparison results are uploaded to the cloud, supervisors and stakeholders in the office can check the situation in real time. For example, sharing the tablet’s AR screen in an online meeting makes it possible for a remote client to check the as-built conditions via the screen. Because appropriate instructions and approvals can be given without physically visiting the site, travel time is reduced and efficient remote supervision inspections (remote presence) become possible.

This kind of data linkage and remote use seamlessly connects the previously separated site and office, accelerating DX (digital transformation) of construction management. By sequentially sharing surveying data and inspection results in the cloud, team information sharing becomes easier and decision-making speeds up. AR as-built inspection is not only about making the site more efficient; it enables a new way of working regardless of location and is attracting attention as a contributor to a productivity revolution in the construction industry.

Start AR as-built inspection with simple surveying using LRTK

To maximize the benefits of AR as-built inspection, a supporting framework for surveying and data processing is indispensable. LRTK simple surveying is exactly an all-in-one solution for easily practicing AR as-built inspection. LRTK is a smartphone-based high-precision positioning and measurement system: with a single iPhone or iPad and a pocket-sized GNSS receiver, surveying and as-built confirmation on site can be completed. Using RTK GNSS, positioning can be achieved with centimeter-level (half-inch accuracy) precision of approximately horizontal ±1–2 cm (±0.4–0.8 in) and vertical ±3 cm (±1.2 in), enabling location identification with accuracy comparable to dedicated surveying equipment. Based on those precise coordinates, projecting the design model in AR or comparing point cloud data on site will not cause the display to shift away from the real object. Stable AR displays without positional shifts allow anyone to perform intuitive as-built checks that paper drawings cannot provide.

Furthermore, LRTK includes a point cloud scanning function that utilizes the smartphone’s built-in LiDAR sensor and camera. Even complex-shaped structures can be quickly turned into high-precision 3D point cloud models simply by scanning with a smartphone. The acquired point cloud data is tagged with absolute coordinates derived from RTK-GNSS, enabling immediate use for comparisons with design data or for calculating embankment/excavation volumes. Also, by recording the coordinates of measured points, LRTK’s coordinate guidance (navigation) function proves powerful when you want to drive stakes or install equipment at the same location later. Just follow the guide displayed on the smartphone screen to walk to the specified coordinate point within a few centimeters of error, making accurate single-person stake positioning possible where it was previously difficult.

By using LRTK simple surveying, which realizes AR display, point cloud acquisition, coordinate guidance, and as-built confirmation on a single platform, tasks that were previously performed with separate equipment and software are seamlessly connected. For example, the workflow of uploading scanned point cloud data to the cloud on site and immediately performing AR checks against the design model can be completed within a single smartphone app. This dramatically accelerates on-site DX and makes efficient construction management possible even in labor-short projects. LRTK is already being introduced at construction sites across the country, contributing to speeding up disaster recovery work and improving productivity in general civil engineering projects. Even those who feel “I want to try AR as-built inspection but don’t know what to prepare” can start operating in a relatively short time with LRTK. Combining cutting-edge technology with ease of use, LRTK simple surveying should become a reliable ally for future sites. AR and GNSS-based as-built checks are not some special future technology but familiar tools already usable on-site. Why not consider introducing them as a smart step toward i-Construction at your site?

FAQ

Q: What do I need to introduce AR as-built inspection on site? A: Basically, you can start with a tablet or smartphone, a GNSS receiver that can provide high-precision positioning, and an application that supports AR as-built inspection. For example, with solutions like LRTK, attaching a small RTK-GNSS antenna to a commercial iPhone or iPad enables centimeter-level positioning, and the dedicated app can handle 3D design data and point cloud data. Once you have the design drawings (BIM/CIM models or electronic drawings) and reference point coordinates on site, you can begin AR as-built inspection immediately.

Q: Is the accuracy of AR-based as-built inspection reliable? A: Yes. When used with high-precision GNSS, AR provides sufficiently reliable accuracy. Ordinary smartphone GPS can have errors of several meters, but with RTK correction, errors can be reduced to a few centimeters. LRTK simple surveying has confirmed horizontal accuracy of about 1–2 cm and comparable accuracy to conventional first-class surveying instruments, so 3D model displays in AR can overlap the real object without noticeable shift, allowing detection of differences or gaps of a few centimeters (a few inches). For critical parts, combining the AR display with acquired point cloud data enables millimeter-level (≈0.04 in) verification.

Q: Can AR as-built inspection be used for supervision and inspection of public works? A: 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 places. Trial projects have shown on-tablet AR overlays of design models and the current condition for as-built inspection. Although AR has not yet been explicitly specified in formal inspection procedures, cases combining point cloud-based as-built evaluation and remote presence with AR checks are increasing. In fact, trial procedures allow omitting the submission of traditional as-built management charts when on-site confirmation is performed with AR. If guidelines are developed in the future, AR as-built inspection may well become established as an official inspection method.

Q: Is operating AR as-built inspection difficult? Can young or inexperienced staff use it? A: Operation is very intuitive, and young employees or those unfamiliar with digital devices can handle it with short training. Measurements and AR displays can be performed with the same ease as taking a photo with a smartphone, so no special surveying skills are required. The data used on site are pre-prepared design models and drawing files, so you only need to select files in the app and follow instructions. With tools like LRTK simple surveying that have well-designed UIs, anyone can perform accurate as-built checks by following on-screen guides. Visual presentation of results also makes them easy to understand and facilitates information sharing within the team.

Q: What kinds of works or sites are suitable for AR as-built inspection? A: It is effective in any situation where you want to check discrepancies between design and reality on site, whether in civil engineering or building construction. Examples include:

• In large-scale earthworks such as road construction or land development, AR heat maps are effective for managing elevations across wide areas, allowing an at-a-glance understanding of embankment and cut/fill conditions across the entire construction area.

• For structures such as tunnels or dams, point cloud data from as-built measurements can be overlaid with 3D design models in AR to check concrete thickness and shape deviations.

• In building construction, you can compare the positions of columns and walls with BIM models or pre-check equipment piping interferences in AR.

In short, AR as-built inspection is useful in any scenario where you want to verify workmanship on the spot. It is particularly beneficial in processes where re-measurement or rework costs are high.