AR Inspections for Everyone: A Revolution in As-Built Inspections Starting from Zero Expertise

Table of Contents

• What is as-built inspection? Background on why AR is gaining attention

• Challenges of traditional as-built inspections

• Benefits of as-built inspections using AR

• Main application scenarios for AR inspections

• AR inspections you can start with zero specialist knowledge

• What is simplified surveying using LRTK

• FAQ

What is As-Built Inspection? Background for AR's Growing Attention

As-built inspection is a quality-control process in civil engineering and construction in which the shape and dimensions of structures and terrain after construction are measured to confirm whether they have been built according to the design drawings. After completion of the work, heights, thicknesses, slopes, and other specified points are measured, and the deviations from the design values are checked to determine pass or fail. This task is essential to ensure on-site quality, but traditionally it has been time-consuming and labor-intensive and has required skilled technicians.

In recent years, AR (Augmented Reality) technology has attracted significant attention in the field of as-built inspection. AR is a technology that overlays digital information such as 3D models and text onto real-world images. Once used only with specialized equipment in limited applications, AR has, thanks to the improved performance of smartphones and tablets, reached a point where it can now be used routinely without special professional gear. In particular, the latest iPhones and iPads are equipped with high-resolution cameras and LiDAR sensors, and by using AR apps that leverage these features it has become possible to intuitively verify as-built conditions on-site.

So why is AR inspection attracting so much attention now? Behind this lies the set of challenges facing the entire construction industry. Traditional as-built inspections rely heavily on experienced surveying technicians, and with chronic labor shortages and the aging of technicians progressing, labor-saving and efficiency improvements have become urgent. Also, with conventional methods that use paper drawings and record forms, even data measured on site must be taken back to the office to be drafted into drawings and checked, which tends to create time lags in detecting problems and issuing corrective instructions. To overcome these circumstances, construction DX (digital transformation), represented by the Ministry of Land, Infrastructure, Transport and Tourism-led i-Construction (Ai-Construction), has been promoted to improve productivity through the adoption of cutting-edge technologies. AR is expected to be one of the powerful solutions and could bring an unprecedented revolution to on-site as-built inspections.

Challenges of Conventional As-Built Inspections

Conventional as-built inspection methods have presented a number of challenges. Let’s look back at the surveying and inspection practices that have been commonly used to date and summarize their shortcomings.

• Work is time-consuming: Because workers painstakingly measure each survey point using surveying instruments such as levels and total stations, it could take a very long time when the site is large or there are many measurement points. Including the task of checking measurement results against drawings, it is not uncommon for completion of as-built inspections to take several days.

• Dependence on skilled technicians: Accurate measurement and evaluation rely on experienced personnel such as surveyors, and with labor shortages and an aging workforce, deploying enough experienced staff to each site is itself a major challenge. Surveying is often done in two-person teams, which is inefficient in terms of labor costs and logistics.

• High cost of specialized equipment: High-precision as-built measurements required expensive specialized equipment such as total stations and RTK-GNSS receivers. These entail initial acquisition costs on the order of several million yen and incur maintenance and management expenses. For small and medium-sized contractors and sole proprietors, this was a significant burden.

• Risk of human error: Manual measurements are prone to human errors such as misreads and transcription mistakes in notes. There were cases where numbers recorded on site were copied incorrectly onto drawings later, resulting in re-measurement or rework.

• Effort required to prepare reports: Creating drawings and reports that summarize inspection results also took time and effort. Organizing measurement data, drafting inspection drawings, and preparing and submitting reports in the required format was a heavy burden for site personnel.

• Delayed detection of defects: Even if there were defects after construction, such as insufficient thickness or incorrect slopes, traditional methods often failed to detect them on the spot and they were only discovered later when drawings were produced. If a problem was found after concrete had already hardened or heavy equipment had been removed, rework or repairs could incur additional costs.

As described above, traditional as-built inspections had many challenges in every respect — time, personnel, cost, accuracy, and immediacy. For example, in buried-pipe construction, it was necessary to survey the pipe location and record photographs before backfilling, then draft drawings in the office and only then confirm them. With such methods, it was difficult to grasp problems on site immediately, and the data tended to be reduced to mere retrospective reporting documents. It was clear that a new method was needed to enable real-time, accurate on-site understanding of as-built conditions.

Benefits of As-Built Inspections with AR

So, how can the above issues be resolved by leveraging AR technology? Here are the main benefits brought about by the as-built inspection revolution using AR.

• Verify intuitively on site: Because design data can be overlaid on site footage, you can visually check construction results on the spot without having to record measurements and compare them with drawings later. Measurement and verification can be performed simultaneously, greatly reducing the time required for inspection.

• Usable without specialist knowledge: AR displays are intuitive and allow you to judge misalignments by sight, so inspections can be carried out without the conventional need for experienced surveying technicians. Even less experienced personnel can accurately grasp the as-built condition while working, because AR helps with 'answer checking'. As a result, this also leads to labor savings.

• No heavy equipment required — convenient: You can perform measurements and inspections on the spot with a smartphone or tablet and a compatible app, without carrying special expensive equipment. Because you can use mobile devices you already own, you can avoid new capital expenditure and reduce the burden of carrying equipment around the site.

• Data is saved automatically: In AR inspections, measurement results and the verification process can be stored directly as digital data. This prevents reading errors and omissions, and streamlines the creation of report drawings after inspection. By sharing photos and point cloud data via the cloud, information can be shared between the site and the office in real time without returning to the office.

• Correct defects immediately: Because defects can be found during inspection, you can decide on repairs or rework on the spot. Cases where problems are discovered later and require rework are reduced, minimizing loss and rework caused by mistakes. In other words, AR inspection transforms the process from "pointing out defects afterwards" to "preventing them on the spot."

By introducing AR in this way, you can greatly reduce the various wastes and risks associated with as-built inspections. In fact, the number of on-site case studies where AR has been used successfully to streamline inspection work and prevent human error is growing. Next, let’s look at the main application scenarios to see exactly how AR inspections are carried out.

Main Use Cases for AR Inspection

So how is AR technology specifically being used on site? There is a growing number of cases where verification tasks that were traditionally carried out on drawings are being made directly visible on site using AR. Here are some representative use cases.

• AR overlay of design models: This is a method of overlaying 3D design models of buildings and civil structures (BIM/CIM models, etc.) onto the real site view to check as-built conditions on site. For example, at a construction site in progress you can use an AR display to compare whether columns and walls are built in the design positions, or use AR for correct foundation layout. Deviations in the final form that are difficult to grasp from paper drawings or surveying instruments alone can be intuitively discovered in real space with AR.

• Heatmap display of as-built deviations: An example use case where 3D as-built data obtained after construction (point cloud scans, etc.) are compared with the design model and errors are color-coded. If you display on-site devices a heatmap automatically generated in the cloud by comparing design data and as-built point clouds, you can immediately see which parts are higher or lower than the design. This helps accelerate the PDCA cycle by evaluating the finish of embankments across surfaces and instantly reworking defective areas.

• AR visualization of buried objects: An example of confirming the positions of structures and pipes buried underground by visualizing them with AR even after paving. In buried works such as sewer piping, by scanning pipes and saving high-precision position data to the cloud before backfilling, anyone can check the location and depth of the pipes through a smartphone even after they are buried. Even inexperienced workers can accurately understand buried objects without drawings, preventing mistakes such as excavating the wrong place and contributing to safety.

• Rebar placement inspection: AR use is also progressing in rebar placement work for concrete structures. By overlaying rebar layout drawings (rebar drawings) onto a smartphone or tablet camera view, you can inspect on site whether the number and spacing of rebars match the design. Traditionally, checks were mainly visual and with a scale, but AR makes it easy to confirm reinforcement in hard-to-see areas, enabling early detection and correction of missing rebars or incorrect pitch.

In addition, applications such as displaying construction areas and height benchmarks in AR to guide heavy equipment operations, and virtually marking concrete pouring locations in advance, are being considered. Initiatives have also begun to recreate on-site environments in AR for safety education and training in construction procedures. AR is expected to permeate an increasingly diverse range of on-site operations, and among these, as-built inspection×AR is attracting particular attention as a use case that delivers immediate results.

AR Inspections You Can Start with Zero Expertise

The biggest appeal of AR inspections is the ease with which they can be started even without specialized knowledge. Traditionally, it was necessary to learn how to operate a total station and acquire basic surveying knowledge, but with AR inspections can be carried out through the simple procedure of just pointing a smartphone and looking at the screen. Even newcomers who are not used to reading drawings can intuitively understand the necessary checkpoints by comparing the 3D model displayed in the real space with the actual object. Parts that used to rely on veterans' intuition and experience can also be shared without going through numbers or drawings with AR, helping to bridge gaps in knowledge and experience.

実際にAR検査を導入する際に必要なのは、基本的にはスマートフォン（またはタブレット）とデジタル化された設計データだけです。最近のiPhoneやAndroid端末であれば標準でAR機能が備わっており、対応アプリをインストールすればすぐに現場で3Dモデルの表示や簡易な計測を試すことができます。例えば、無料で使えるARアプリで柱位置を投影してみる、スマホのAR計測機能で簡単な寸法を測ってみる、といったところから誰でも始められるのです。もちろん現場で実用的な精度を得るには、さらに高精度な測位システムや専用アプリの活用が有効ですが、そのハードルも決して高くありません。次に紹介するような最新ソリューションを利用すれば、専門の測量技術がなくてもすぐにプロ並みの精度でAR検査を実践できます。

What is simplified surveying with LRTK

One of the key technologies that makes this kind of "AR inspection anyone can perform" a reality is simplified surveying using LRTK (Eru Aru Tii Kē). LRTK is an innovative solution that turns a smartphone into a surveying instrument capable of centimeter-level positioning by attaching a compact, high-precision GNSS receiver (antenna) to the phone. For example, by attaching a dedicated RTK-GNSS antenna to an iPhone and launching the [LRTK Phone](https://www.lrtk.lefixea.com/lrtk-phone) app, anyone can immediately start surveying using the RTK method, and the smartphone itself functions as an "all-purpose surveying instrument."

Normally, the accuracy of a smartphone’s built-in GPS is on the order of several meters (several ft), but by using an LRTK device you can achieve dramatically higher positioning accuracy — errors within a few centimeters (a few in). This is a method called RTK (real-time kinematic), which is achieved by applying correction information from a base station in real time to cancel out positioning errors. It may sound complicated, but in LRTK those settings are fully automated, and the user only needs to attach the antenna and follow the app’s instructions to obtain high-precision location information. It also supports Japan’s “Michibiki” satellite centimeter-level positioning augmentation service (CLAS), offering cm level accuracy (half-inch accuracy), and a notable feature is that it can maintain high-precision positioning even in mountainous areas or other locations without network connectivity, as long as satellite signals can be received.

By enabling precise positioning with LRTK, AR inspections become even more convenient. Traditionally, displaying a 3D model on-site in the correct position and scale for AR required initial calibration to track equipment to reference points. However, with LRTK, simply pointing a smartphone at the site automatically projects the design model aligned to world coordinates. Even when walking around a large site, the model won’t shift or float, providing a stable AR display that is always perfectly aligned with the real object. In short, without being bothered by complicated alignment tasks, anyone can easily perform accurate AR inspections.

Furthermore, LRTK not only measures positions but also streamlines the collection and sharing of field data. Coordinate values of points measured with a smartphone and photos taken can be uploaded to the cloud instantly with the push of a button. Office personnel can immediately view that data on the web, enabling real-time information sharing between the field and remote locations. In addition, by simply walking while holding a smartphone you can 3D-scan large areas of terrain and obtain high-precision point cloud data with absolute coordinates. Using that point cloud, it is also possible to automatically generate color-coded as-built heatmaps and calculate embankment volumes. Processes that were traditionally outsourced to specialists—surveying, 3D measurement, and report preparation—can be completed with a single smartphone and cloud service when using LRTK, truly embodying "simplified surveying".

Thus, LRTK is a groundbreaking technology that dramatically lowers the barriers to AR inspections. Even without expensive surveying equipment or years of experience, anyone can immediately carry out highly accurate as-built inspections with just a smartphone and LRTK. For those considering introducing AR inspections, LRTK will be a reliable ally. Be sure to experience this as-built inspection revolution that will transform on-site inspection practices.

FAQ

Q. What do I need to start AR inspections? A. Basically, you can get started with a smartphone (or tablet) capable of AR display and the design data of the object to be inspected. On modern smartphones, AR functionality is built in by default, so prepare the corresponding app or software. For example, if you load drawing data or 3D models into construction AR software, you can then simply hold up the smartphone on site to display the model. If you want to operate with higher accuracy, it is recommended to use a high-precision GNSS device (e.g., LRTK) attached to the smartphone, as this can eliminate alignment work and enable centimeter-level positioning (half-inch accuracy).

Q. Can you really perform as-built inspections without specialized knowledge or experience? A. Yes, it is possible. AR inspections are designed to be intuitive so that no specialized surveying skills are required. By moving your smartphone following the on-screen guides, anyone can easily capture the data needed for inspections. Misalignments that previously only experienced personnel could notice are visualized with AR, making them easier for beginners to detect. Of course, you will need to get used to the operation at first, but anyone who can use smartphone apps should be able to master it with a short practice session.

Q. Can the accuracy of AR inspections be trusted? A. If operated properly, they can be relied on for high accuracy. Using only a smartphone’s built-in AR functions can produce errors on the order of a few centimeters to tens of centimeters (a few inches to several dozen inches), but by combining with high-precision positioning technologies like LRTK it is possible to reduce errors to within a few centimeters (within a few inches). On actual construction sites, AR inspections using LRTK have already been confirmed to achieve accuracy comparable to conventional total station surveying. However, achieving that level of accuracy requires attention to calibration and radio signal conditions. When used according to correct procedures, AR inspections deliver accuracy that is sufficiently practical for real-world use.

Q. What kinds of sites can AR inspections be used on? A. They can be used at a wide range of sites across both civil engineering and building construction. For example, in roadworks and land development, AR helps verify finished heights and slopes on the spot. On building sites, it can be used to check locations for columns, walls, and equipment piping, or to share a completed-image before concrete is poured. AR inspections are also useful across many processes, such as verifying the position of buried pipes before and after backfilling, as-built control in bridge and tunnel works, and rebar placement inspections. In recent years, AR-based inspection methods have also been expanding into non-construction fields, such as infrastructure inspections and manufacturing quality checks. In short, AR inspections are effective in any situation where you need to confirm differences between the actual object and the design.