What is AR Inspection? The Latest Technology That Transforms As-Built Inspection

Table of Contents

• What is AR inspection?

• Challenges of traditional as-built inspection

• How AR technology enables as-built inspection

• AR inspection procedure and use cases

• Ministry of Land, Infrastructure, Transport and Tourism initiatives and digitalization trends

• Benefits of AR inspection

• Conclusion: How to get started with AR inspection easily

• FAQ

What is AR inspection?

AR inspection is a new on-site method for verifying whether the shapes and dimensions of completed structures or developed land in construction and civil engineering match the design drawings. Traditional as-built inspection (as-built control) involved measuring heights and thicknesses at each point using tape measures, staffs (leveling rods), spirit levels, total stations, etc., and checking the differences against the drawings. However, these conventional methods can only measure a limited number of points, which may allow small deviations to be missed, and result verification and reporting were done back in the office after returning, causing time lags.

As-built inspection using AR (Augmented Reality) overlays design drawings or 3D model information on the camera feed of a smartphone or tablet. By projecting design lines and reference planes onto the real-world image, it becomes possible to intuitively grasp discrepancies between the physical object and the digital design on the spot. For example, if you AR-display a design reference plane of elevation over the finished ground surface, you can immediately tell whether embankment or cut-and-fill heights match the design. In this way, AR inspection is attracting attention as a cutting‑edge technique that enables real-time on-site verification of as-built conditions and quality assurance.

Challenges of traditional as-built inspection

First, let’s summarize the main issues that traditional as-built inspection (as-built control) has faced. Conventional practice relied on manual labor and analog instruments for measurement and recording, and the following problems have been pointed out.

• Labor- and time-intensive: Large sites have many measurement points, and it is not uncommon for a multi-person team to spend an entire day on measurements. Securing experienced surveying technicians is difficult, and it is hard to proceed efficiently amid labor shortages.

• Risk of oversight: There is a limit to how many points people can measure manually. Measuring only representative points may not capture subtle unevenness or dimensional variations across the whole area, so sections that differ from the design may be missed. Cases where it is discovered later that “it differs from the drawings” and rework is required have occurred.

• Human error: Busy sites are prone to forgotten photos and recording mistakes. Writing measurement values incorrectly or making transcription errors can lead to incorrect inspection results. If photos of buried objects are not recorded, it may become impossible to prove the construction situation later. Such human errors cause quality problems and additional work.

• Lack of real-time capability: Pass/fail judgments could not be made on the spot; data were measured and taken back to the office for review before problems were discovered. For example, if concrete thickness was insufficient, it might be noticed the next day or later, requiring rework that could be extensive if curing had progressed. This inefficiency comes from not being able to detect and correct issues immediately on site.

• Burden of record-keeping: As-built control requires organizing measurement results into tables and photo logs and submitting them as reports to the client. Manual document preparation takes time and effort and is a heavy burden on staff. These administrative tasks are one factor that has hindered improvements in site productivity.

Because of these issues, a more efficient and reliable as-built inspection method has long been desired. Recently, with labor shortages and work-style reforms, expectations for digital technologies that can achieve both labor saving and quality improvement have increased. One solution that has emerged in this context is as-built verification using AR.

How AR technology enables as-built inspection

A key solution attracting attention to address the limitations of conventional methods is the fusion of AR technology and high-precision positioning. By attaching a compact RTK‑GNSS receiver (high-precision GPS antenna) to a smartphone or tablet and using a dedicated app, anyone can easily obtain centimeter-level position information (a few centimeters (a few in)) on site. RTK‑GNSS (Real Time Kinematic GNSS) uses correction information from a base station to reduce GPS positioning error to within a few centimeters; while this once required expensive specialized equipment, compact devices with smartphone connectivity now provide comparable real-time accuracy.

When high-precision self-positioning is available, spatial registration with digital design data becomes possible. By loading design drawings or BIM/CIM 3D model data into a dedicated app and aligning them with the site coordinate system, those models can be accurately overlaid on the smartphone camera view. For example, the planned finished-line or reference plane can be projected directly into the view. Because the GNSS aligns the position with the world coordinate system, the virtual model does not drift relative to reality as the user walks around the site. As a result, the physical structure and the digital design model can be compared one-to-one, allowing real-time on-site checks of as-built conformance.

Furthermore, modern smartphones often include LiDAR scanners and high-performance cameras, making on-site 3D measurement easy. For example, you can scan the inspection area with a smartphone to acquire a high-density point cloud (3D measurement data of as‑is conditions), and if you compare that in the cloud with the design model you can automatically generate an error heat map. Downloading a color-coded heat map of height or thickness differences to the smartphone and displaying it in AR overlays the error distribution onto the real landscape. You can instantly see which points are higher or lower than the design by how many centimeters, enabling immediate corrective actions such as adding fill or excavating excess material. Previously, point-cloud data had to be processed into color-coded maps (heat maps) on plan views and then used to locate problem areas on site, but AR technology now makes it possible to “see it directly on site.”

In short, the combination of AR and high-precision positioning is transforming the prior “measure, take it back, inspect and report in the office” process into real-time verification that is completed on the spot. Surveying, as-built verification, and photo documentation can be done with a single smartphone, and the necessary data can be shared instantly to the cloud so stakeholders can confirm and decide on the next steps immediately. This is a technological innovation that can dramatically improve site productivity and quality control.

AR inspection procedure and use cases

How is as‑built inspection using AR actually carried out on site? Let’s look at a typical workflow using AR × GNSS for civil engineering works.

• Preparation (prepare design data): First, prepare digital design drawings and 3D models of the structures or developed land to be inspected. It is ideal if BIM/CIM models or CAD drawings include the finished shape and reference line information. Load these data into the dedicated app and align them with the site surveying coordinate system. The use of 3D data in many public works has been progressing in recent years, making digital design information easier to obtain.

• Equipment setup: On site, attach an RTK‑GNSS receiver to a smartphone or tablet and set it up for high‑precision positioning. In Japan, centimeter-class augmentation services (CLAS) provided by the positioning satellite “Michibiki” and network RTK correction information available via the internet make it easy to improve positioning accuracy. Once the equipment is powered on and positioning stabilizes, start the app’s AR display mode and, if necessary, calibrate the orientation sensor (digital compass).

• As-built verification: When the overlay display of the design data is ready, begin actual as-built checking. For example, when inspecting the height of developed land, project the design finished elevation as a virtual horizontal plane onto the ground with AR. The smartphone screen will show the “design height reference plane” overlaid on the real scene, so by walking and observing the gap between that plane and the ground you can intuitively find areas with insufficient or excessive fill. Similarly, for roadworks you can AR-display the design longitudinal and cross-sections to instantly verify whether pavement thickness and slopes are within specifications.

• Real-time guidance and correction: When discrepancies from the design are identified via AR, share the information with workers on the spot and carry out corrective work immediately. For example, if you find “this point is 5 cm low,” you can add fill to that point right away. Numeric guides and color hints displayed in AR are more visually intuitive than verbal instructions, reducing communication loss between workers and supervisors. This minimizes rework during construction and enables smooth quality assurance.

• Data recording and reporting: After inspection, save the results as digital data. Geotagged site photos taken with the smartphone are automatically saved to the cloud along with capture locations and orientations, so stakeholders in the office can review them later. If point-cloud scanning was performed, some systems can generate as-built heat maps and as-built control charts with a single click from the acquired data. Such digital records can be used directly as reporting materials for clients, greatly reducing the burden of document preparation.

Through this workflow, AR and GNSS‑based as-built inspection make it possible to digitally complete verification, correction, and recording on site in real time. Compared with traditional methods that relied on paper drawings and tape measures, this is a dramatically more efficient workflow.

Ministry of Land, Infrastructure, Transport and Tourism initiatives and digitalization trends

Although AR-based as-built inspection is cutting-edge, it is by no means a fringe idea. The Ministry of Land, Infrastructure, Transport and Tourism (MLIT) promotes ICT use in construction management and officially supports the digitalization of as-built control. As part of its *i‑Construction* initiative, MLIT has encouraged the adoption of BIM/CIM and 3D surveying technologies. It has also developed the “Guidelines for As-Built Control Using 3D Measurement Technology (draft)” and standardized as-built measurement methods using drone photogrammetry and terrestrial laser scanners.

Notably, in Reiwa 4 (2022), MLIT revised the as-built control guidelines to formally allow the use of smartphones and other simple mobile devices as public-construction as-built measurement equipment. This change makes it possible for small and medium-sized contractors to implement 3D as-built control using smartphones without expensive specialized instruments. From Reiwa 6 (2024), trials of supervision and inspection using digital data in MLIT-managed projects have progressed, and a new method has been proposed to project 3D models created during construction onto the site using AR and perform as-built verification on the spot. This aims to omit and streamline the previous process of creating and submitting point-cloud heat maps and then remeasuring on site by enabling on-site confirmation with AR.

As public and private sectors pursue digital transformation (DX) in construction sites, AR-based as-built inspection fits naturally into this trend. With the full-scale application of BIM/CIM principles from FY2023, many projects will develop 3D design data, dramatically increasing the digital information available for AR use. Smart construction that does not rely on paper and manual labor is steadily spreading on sites, and AR inspection is expected to become increasingly widespread as a powerful method for balancing quality and efficiency.

Benefits of AR inspection

The AR and high-precision positioning approach to as-built inspection brings substantial benefits to construction sites. Key advantages include:

• Labor saving and efficiency gains: Surveying and inspection tasks that previously required two or more people can be completed by one person, making it easier to cope with labor shortages on site. Delays due to waiting for surveying are reduced, and immediate measurement and verification facilitate smoother overall project progress. This results in shorter working hours and higher productivity.

• Quality improvement through high-density measurement: Using smartphone LiDAR and continuous measurement, large areas can be measured at high density to grasp as-built conditions across entire surfaces. Covering the whole area with data rather than isolated points reduces the chance of overlooking small unevenness or dimensional variations, lowering variability in construction quality. This is a significant advantage in quality control for both clients and contractors.

• Reduced rework through real-time correction: Because inspections can be done immediately after construction, problems that would otherwise be found only during later inspections can be prevented. The ability to “confirm and correct on the spot” enables early detection and immediate response, greatly reducing the risk of rework and schedule delays. This ultimately helps control unnecessary costs.

• Intuitive and easy information sharing: AR visualizations are more intuitively understandable than numeric-only reports. If everyone on site sees the same AR view on their smartphone, “where and by how much something needs to be corrected” becomes immediately clear. This allows anyone, regardless of experience or intuition, to understand the situation and smooths alignment and consensus among craftsmen and supervisors.

• Digital records and knowledge transfer: Measurement results and site photos are saved and shared as digital data, reducing the effort required to create forms and reports. Centrally managed as-built data can be used for future maintenance and renovation work. In addition, insights and observations from experienced personnel can be preserved as data, enabling accumulation and transfer of knowledge beyond individual expertise.

• Improved safety: AR-based remote measurement and guidance can reduce the need to enter hazardous areas. For steep slopes or high places, markers can be placed and guided from a safe distance, reducing the need for risky postures during surveying. During pile driving or staking in areas with operating heavy equipment, AR guidance displays help the operator and the surveyor maintain distance, contributing to lower collision risk.

As shown above, AR inspection is not merely a novelty gadget but provides practical benefits that directly address site challenges. With the construction industry facing aging and labor shortages, AR inspection is likely to spread widely as a trump card that balances efficiency and quality.

Conclusion: How to get started with AR inspection easily

Once, AR-based as-built inspection was a cutting-edge endeavor requiring specialized equipment. Today, however, easy solutions are available that anyone can use by combining a smartphone with a compact GNSS receiver. For example, LRTK, a venture originating from the Tokyo Institute of Technology, is a system consisting of a pocket-sized RTK‑GNSS device attachable to an iPhone and a dedicated app that transforms the site into an environment where “surveying and inspection can be completed with just a smartphone.” Even technicians without special training can operate it intuitively, and it provides functions for simple surveying such as centimeter-level positioning and point-cloud scanning and AR-based as-built checking (cm level accuracy (half-inch accuracy)).

With tools like these, the barrier to adopting AR inspection drops and anyone can practice it in daily 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 it on site first. You will notice how easily the traditional methods that relied on paper drawings and tape measures can be digitized. AR inspection is not some distant futuristic technology but a familiar tool already usable on today’s sites. Why not take this opportunity to adopt AR technology and start simple smart construction at your site?

FAQ

Q: Can AR-based as-built inspection be trusted for accuracy? A: Yes. AR inspection combined with high-precision GNSS (RTK-type GPS) can reduce positional error to the order of several centimeters (a few centimeters (a few in)), making it sufficiently reliable. Built-in smartphone GPS typically has errors of several meters (several ft), but using RTK corrections allows self-positioning at a level comparable to survey control points. With proper calibration of the smartphone’s gyroscope and digital compass, the discrepancy between the displayed digital model and the real object will be hardly noticeable.

Q: What preparations and equipment are needed to perform AR inspection on site? A: Basically, “smartphone/tablet + RTK-capable GNSS receiver + dedicated app” is sufficient to perform AR as-built inspection. Prepare the design data to be inspected (3D models or digital drawings) and load them into the app in advance, then perform GNSS positioning on site while displaying AR. GNSS receivers that can receive correction data over the internet (network RTK) are convenient. In outdoor areas with radio access, national satellite augmentation services or private reference-station networks can be used to achieve high-precision positioning without installing your own base station.

Q: Can AR inspection be done in places where GNSS is not available, such as inside tunnels or buildings? A: Pure GNSS positioning does not work where there is no sky view. However, alternative methods exist, such as installing AR markers (known points) for alignment. For tunnels, for example, you can use a reference point positioned with GNSS near the entrance and perform relative positioning to known points inside the tunnel, using that reference for AR display. Indoors, QR codes or markers placed on floors or walls can be recognized by the smartphone camera to align positions. By using these methods, AR inspection can be applied to locations where GNSS is unavailable to some extent.

Q: Is the cost of introducing AR inspection high? A: In many cases it is much lower cost than purchasing new specialized surveying equipment. You can use existing smartphones or tablets, and compact high-precision GNSS receivers are relatively inexpensive compared to total stations, etc. Software is often offered as cloud services, allowing flexible use with short-term licenses. Moreover, the time savings and reduced personnel requirements produce cost reductions, so overall the benefits can outweigh the investment.

Q: Can people without specialized knowledge use AR technology effectively on site? A: Basic operations are not difficult if you follow the guided procedures. For example, systems like LRTK let you point an antenna-equipped smartphone at a point to record coordinates by pressing a button, and AR display is achieved by selecting model data from a menu and overlaying it. However, when first introducing the system you will need to become familiar with equipment handling and calibration procedures, so brief training is recommended. With repeated use on site you will pick up the techniques and be able to utilize it effectively without specialized skills.