Remote Supervision Made Possible: How AR As-built Inspection Expands Field Workstyles

Table of Contents

• What is AR as-built inspection?

• Challenges of traditional as-built inspection

• Benefits of AR as-built inspection - Precise inspection that doesn’t miss millimeter-level deviations - Improved inspection efficiency and smoother consensus building - Digitalization of as-built records and proof of quality - Labor saving through simple surveying anyone can do - On-site DX with remote supervision and cloud sharing

• AR as-built inspection enabled by simple surveying with LRTK

• FAQ

What is AR as-built inspection?

As-built inspection is a quality control process in civil engineering and construction whereby completed structures or formed terrain are measured and verified to confirm they were constructed according to the design drawings. Traditionally, survey instruments such as total stations (TS), levels, and tape measures were used to measure heights, thicknesses, and other points on site; the data would then be taken back to the office and compared with drawings to determine pass/fail. However, this method often introduces a time lag between measurement on site and discovery of problems, sometimes resulting in rework. Additionally, measurement and judgment in as-built inspection have relied heavily on the experience of skilled technicians; with labor shortages and an aging workforce, improving efficiency has become a major challenge.

Against this backdrop, AR as-built inspection has attracted attention in recent years. By using AR (Augmented Reality) technology to overlay 3D design models and measurement data on smartphone or tablet camera images, it enables a new method of directly verifying as-built conditions on site. Instead of squinting at paper drawings or numeric data, inspectors can compare the real object and digital information on the spot, allowing even less experienced technicians to intuitively judge whether finishes match the design.

Especially when combined with high-precision GNSS positioning, it becomes possible to align models and data displayed in AR with the actual structure within a few centimeters (within a few inches). Using a smartphone plus an RTK-GNSS receiver enables centimeter-level (half-inch-level) high-precision positioning, so AR displays can be overlaid precisely on the real object without drift. Furthermore, using LiDAR sensors found on the latest iPhones and iPads, you can scan the site to obtain point cloud data (the current shape made up of countless 3D points) and compare it with the design data on site, visualizing deviations with color coding for advanced checks. The Ministry of Land, Infrastructure, Transport and Tourism is also promoting 3D measurement and AR through initiatives such as “i-Construction,” and AR as-built inspection is highly anticipated as a solution that can simultaneously improve site efficiency and quality.

Challenges of traditional as-built inspection

To understand the benefits of AR as-built inspection, let’s first organize the main issues with conventional as-built inspection methods. The traditional approach had the following problems:

• Time-consuming and labor-intensive: Survey staff measured each point carefully using instruments and tape measures and recorded results on paper. Where construction areas are wide and measurement points are many, it can take days to complete all measurements and drawing comparisons.

• Dependence on skilled personnel: Accurately measuring and evaluating to millimeter precision requires experienced surveyors. Sometimes two-person teams were necessary. With chronic labor shortages and an aging technician pool, it has become difficult to assign enough skilled personnel to each site.

• Expensive equipment required: To strictly measure deviations from design values, specialized survey equipment such as high-precision TS or GNSS receivers are needed. These require very high initial investment and are a barrier for small and medium-sized enterprises. Maintenance costs and theft risk are also non-negligible.

• Risk of human error: Manual measurement often leads to mistakes such as incorrect notes or transcription errors. There are cases where a missed measurement is noticed later, requiring a return trip to remeasure.

• Delay in problem discovery: Because inspections were often performed back at the office, construction defects could not be detected on site and corrective action would be delayed. For example, if insufficient concrete thickness or incorrect pavement slope is discovered the next day or later, the material may already have hardened or been backfilled, making remediation extensive.

• Burden of document preparation: As-built management requires preparing drawings and reports based on measurement results and submitting them to the client. Traditionally, preparing these documents took considerable time and effort, posing a heavy burden on site supervisors.

Thus, traditional as-built inspection was inherently inefficient and carried the risk of overlooking quality issues. To check as-built conditions in real time and with high precision, the use of new digital technologies was inevitable.

Benefits of AR as-built inspection

AR-based as-built inspection using the latest AR technology offers a variety of benefits that can address the issues described above. Let’s look at the main points in order.

Precise inspection that doesn’t miss millimeter-level deviations

One of the biggest benefits of AR as-built inspection is its ability to detect construction errors and slight deviations in finishes that would otherwise be missed. By overlaying design data on camera images, subtle height differences and insufficient thickness that are hard to spot with the naked eye can be immediately visualized.

For example, in road embankment work, scanning the finished surface with a smartphone to generate point cloud data and comparing it with the design model in AR on site makes surface irregularities and slight slope defects obvious. If differences in elevation are displayed as a color-coded heat map, you can intuitively understand “which point is how many centimeters higher/lower than the design.” As a result, mistakes that even veterans might have overlooked under conventional methods can be reliably detected, enabling early correction of quality defects.

AR visual checks also reduce human errors such as misreading numbers. Because you can compare drawings and the actual object visually, inspection accuracy is dramatically improved compared to relying on lists of numbers alone. Moreover, objects that become invisible after completion—such as buried pipes—can be made visible by AR if you have previously 3D-scanned and stored their point cloud model, allowing accurate location confirmation after backfilling. For instance, if a sewer pipe is recorded in 3D before installation, you can still confirm the pipe’s route and depth on a smartphone after paving is completed, reducing the risk of accidental damage in subsequent work. In short, AR as-built inspection captures even small on-site deviations and makes a major contribution to preventing quality troubles in advance.

Improved inspection efficiency and smoother consensus building

Using AR dramatically speeds up inspection work and consensus-building with clients and supervisors. Because wide areas can be measured in 3D at once, work time is greatly reduced compared to measuring points one by one, and software can automatically analyze measurement data and determine pass/fail.

For example, using drone photogrammetry or iPhone LiDAR scanning, slope as-built measurement that used to take half a day can in some cases be completed in tens of minutes. Acquired point cloud data is automatically compared with design data in the cloud, and any areas outside specifications are immediately highlighted. Inspectors can understand the results on a tablet screen on site, eliminating the need to use a calculator to compute deviations or mark up drawings with red pens.

Also, 3D AR displays make it easier for all stakeholders to understand the situation, so explanations and on-site inspections with clients and supervisors go smoothly. Clients who used to receive just numeric reports can now, via a tablet on site, see the discrepancy between the completed form and the actual object with their own eyes, increasing their sense of assurance. Even for remote attendance (remote inspections), sharing AR video from the site allows the office side to grasp the situation accurately and reduces communication loss. This kind of visualization enables high-trust consensus building between client and contractor and dramatically streamlines the process to inspection approval.

Digitalization of as-built records and proof of quality

AR as-built inspection also enables comprehensive digitalization of as-built records, which serves as reliable proof of quality. Once you obtain 3D scans and point cloud data, you can comprehensively record construction results without “missed measurements” or “missing photos.” Where traditional methods measured only a few critical points and inferred the rest, 3D data allows you to understand the entire structure down to every corner.

High-precision point clouds and geotagged photos become digital inspection evidence. If you automatically generate color-coded difference maps or cross-section comparisons, you can prove objectively later “whether it was really built according to the design.” Micro deviations that are difficult to convey on paper drawings become immediately understandable when shown on a 3D model, improving the explanatory power of as-built management.

Furthermore, these digital records can be securely stored and shared in the cloud, making electronic delivery to clients easy. Creation of inspection documents can be further automated, reducing the reporting burden on site supervisors. In future planning of similar projects, past as-built data can be used as reference material, enabling data-driven decision making. Digital quality proof provided by AR as-built inspection is expected to contribute to long-term reliability assurance and accumulation of know-how.

Labor saving through simple surveying anyone can do

Modern AR inspection tools run on smartphones and tablets, so they are designed so that even those unfamiliar with special equipment can perform simple surveying. For example, with a smartphone surveying system, you can follow app prompts without complex settings or difficult calculations to achieve high-precision positioning and scanning. Intuitive UIs and workflows let even novice technicians operate the system, so as-built data can be acquired and checked at a certain level of accuracy even on sites without a licensed surveyor.

Digital measurement also records wide areas at once, enabling substantial labor savings. If surveying tasks that used to require two-person teams can be done by one person, not only are labor costs reduced, but staffing coordination is easier. There is no need to carry heavy survey equipment across the site or spend time setting up and packing instruments. As a result, limited personnel can cover more tasks, and the physical and mental burden on workers is reduced.

This freed capacity can be redirected to other quality control or safety management tasks. AR as-built inspection realizes a smart construction that does not rely on specific people and can be a decisive tool to mitigate the worsening labor shortage.

On-site DX with remote supervision and cloud sharing

Combining AR as-built inspection with cloud technology promotes on-site digital transformation (site DX) that enables remote understanding of field conditions. 3D data and AR video captured on site can be shared instantly within and outside the organization via the cloud, allowing multiple sites to be remotely supervised and supported in real time from the office.

For example, when site staff upload scanned point cloud models or live AR video from a smartphone to the cloud, headquarters engineers or clients can check as-built conditions from their desks. They can easily add comments to the data or issue additional instructions remotely. If remote attendance is realized, inspections and meetings can be held without travel, reducing travel time and costs and speeding up decision making.

Also, as-built data accumulated in the cloud is always available to stakeholders as the latest information. By sharing drawing files and point cloud data online among all parties, time lags such as “we don’t have the latest data on hand so we can’t decide” are eliminated. Seamless information flow between site and office, and between client and contractor, will transform construction management workflows. Such remote supervision systems leveraging AR and data sharing are likely to become the new standard style of smart construction sites in the future.

AR as-built inspection enabled by simple surveying with LRTK

To maximize the benefits of AR as-built inspection, it is essential to have supporting surveying technology and data processing mechanisms. Simple surveying with LRTK is an all-in-one solution that makes AR as-built inspection easy to implement.

LRTK is a high-precision positioning and measurement system that uses smartphones; with a commercially available iPhone and a pocket-sized GNSS receiver you can complete on-site surveying and as-built verification. RTK GNSS provides centimeter-level accuracy—horizontal ±1–2 cm (±0.4–0.8 in); vertical ±3 cm (±1.2 in)—allowing positions to be determined 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, so stable AR displays that don’t drift enable intuitive as-built checks that were difficult with paper drawings.

Moreover, LRTK also includes a point cloud scanning function that leverages the iPhone’s built-in LiDAR sensor and camera. Even complex-shaped structures can be scanned by simply waving the smartphone, generating high-precision 3D point cloud models. Because acquired point clouds are tagged with absolute coordinates from RTK-GNSS, they can be used immediately after capture to compare with design data or to calculate fill/excavation volumes. Also, if you save coordinates of measured points and later need to stake out or install equipment at the same location, LRTK’s coordinate navigation (coordinate guidance) feature is powerful: by following guides on the phone screen you can be guided to the specified coordinate point to within a few centimeters (a few inches), making solo stakeout tasks that were previously difficult much easier.

By realizing AR display, point cloud acquisition, coordinate guidance, and as-built inspection on a single platform, LRTK simple surveying seamlessly connects tasks that used to require disparate equipment and software. For example, you can scan a point cloud on site, upload it to the cloud immediately, and have a remote supervisor check differences in the AR view—completing the entire workflow within a single smartphone app. This accelerates on-site DX. LRTK has already been introduced at construction sites nationwide, contributing significantly to faster disaster recovery and more efficient construction management. Even those who “want to try AR as-built inspection but don’t know where to start” can begin onsite implementation in a relatively short time using LRTK. Combining cutting-edge technology with ease of use, LRTK simple surveying will become a reliable partner for future job sites.

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 high-precision GNSS receiver, and an application that supports AR as-built inspection. For example, solutions like LRTK make centimeter-level positioning possible by simply attaching a small GNSS antenna to a commercially available iPhone or iPad, and the dedicated app can handle 3D design data and point cloud data. As long as you have the digital design files (BIM/CIM models or electronic drawings) and the site control point coordinates, you can begin AR as-built inspection on site.

Q: Is the accuracy of AR-based as-built inspection reliable? A: Yes. If high-precision GNSS is used, inspection via AR can achieve sufficiently reliable accuracy. A smartphone’s built-in GPS typically has errors of several meters (several feet), but with RTK corrections those errors can be reduced to a few centimeters. LRTK simple surveying has demonstrated horizontal accuracy of about 1–2 cm (±0.4–0.8 in), which is comparable to conventional first-class survey instruments. Because the model displayed in AR aligns with the actual object without noticeable offset, steps or gaps of a few centimeters (a few inches) can be reliably detected. For critical parts, combining point cloud measurement data allows verification down to the millimeter level (hundredths of an inch).

Q: Can AR as-built inspection be used for supervision and inspection of public works? A: Currently, the Ministry of Land, Infrastructure, Transport and Tourism actively promotes ICT construction and 3D as-built management, and various demonstrations of AR utilization are underway. Trial projects have published case studies where inspections were conducted by overlaying design models with current conditions on a tablet AR screen. Although AR is not yet explicitly written into formal inspection procedures, cases are increasing where AR checks are incorporated into supervision and inspection processes in combination with surface management using point cloud data and remote attendance. If guidelines are developed in the future, AR as-built inspection could become part of official inspection methods.

Q: Is operating AR as-built inspection difficult? Can young or inexperienced staff use it? A: Operation is intuitive, and even young staff unfamiliar with digital devices can learn it in a short training session. Measurement and AR display work like taking pictures with a smartphone camera, so no special surveying skills are required. The data used on site are pre-prepared design models and drawings, so you simply select the files in the app and follow instructions. With tools like LRTK simple surveying, which feature thoughtfully designed UIs, following on-screen guidance enables anyone to perform accurate as-built checks. Visualized results are easy to understand, and information sharing within the team is also straightforward.

Q: For what kinds of construction or sites is AR as-built inspection effective? A: Regardless of civil or building construction, AR as-built inspection is useful in any situation where you want to verify construction results on the spot. For example, in large-scale earthworks such as road construction and site formation, AR heat maps are effective for wide-area elevation management; 3D model comparisons are useful for checking thickness and shape of structures like tunnels and dams. In building construction, you can compare column and wall positions with BIM models during structural work or use AR to pre-check interference of equipment piping. In short, AR is effective on any site where you want to confirm finishes immediately after construction. The benefits of introducing AR inspection are particularly large for processes where re-measurement or rework would be costly.