AR Inspection Q&A: Solve On-site Questions! A New Style for As-built Inspections

Contents

• What is AR inspection?

• What is as-built inspection? Problems with conventional methods

• How does AR technology change as-built inspection?

• Benefits and effects of AR inspection

• Is AR inspection accurate and reliable?

• What do you need to start AR inspection?

• Will AR inspection become commonplace?

• Conclusion: How to easily start AR inspection

• FAQ

AR inspection has attracted attention in recent years as a way to improve productivity on construction sites and address labor shortages. But when you hear “inspection with AR,” you may not have a concrete image and might wonder, “Is it really useful?” or “How do you use it?” This article explains in a Q&A format what AR inspection is, its benefits, and how to introduce it. Note that AR inspection is also aligned with the Ministry of Land, Infrastructure, Transport and Tourism’s *i-Construction* initiative, and it is gaining attention across the industry. We’ll answer the questions you’re likely to have on site and clearly introduce a new style of as-built inspection.

What is AR inspection?

AR inspection is a new method that uses AR (Augmented Reality) technology for inspection tasks on construction sites. By overlaying digital information such as design drawings or 3D models onto real-world images through a smartphone or tablet camera, you can intuitively check the as-built condition (the shape after construction) on the spot. For example, if you display design lines and dimensions in AR over a completed structure or terrain, you can immediately tell whether the actual object was finished according to the design. AR inspection’s feature is that inspections that used to require comparing drawings and measurement data can now be “confirmed visually on site.” This kind of AR inspection is made possible by improvements in smartphone sensor performance and advances in high-precision positioning technologies. It can be described as a completely new inspection style that fuses the real thing with digital information.

What is as-built inspection? Problems with conventional methods

First, as-built inspection is an important process in civil and construction work in which the completed structures and developed land are measured and recorded to confirm they match the design’s shape and dimensions. In public works, as-built inspection results are often a condition for inspection approval and handover, so they are indispensable for quality control. Traditionally, as-built confirmation has been carried out by direct measurement using tools such as tape measures, staffs (leveling rods), and levels, along with photography. However, the conventional methods have faced the following on-site issues:

• Labor- and time-intensive: Surveying and as-built measurement tasks usually require teams of several people, and for wide sites or projects with many measurement points, it can take a full day. Securing experienced workers is also difficult, and performing conventional methods amid labor shortages has been a heavy burden.

• Limited measurement points and risk of omission: The number of points that can be measured manually is limited, making it difficult to cover the entire site. Because only representative points are measured, there is a risk of missing areas that differ from the design. The larger the structure, the harder it is to grasp subtle unevenness, and inspections sometimes find “differences from the drawings,” forcing hurried rework.

• Difficult to measure in hazardous locations: Measurements are challenging for locations that are hard to access for safety reasons, such as high slopes, deep excavation trenches, or the undersides of bridges. Trying to measure these places forcibly can risk falls and other accidents, and there were often places that were “left unmeasured” out of necessity.

• Effort and errors in recordkeeping: Recording tasks like transcribing measurement results onto drawings or creating photo logs are time-consuming, and site managers were occupied with daily report preparation. Human errors such as forgetting to take photos or copying measurement values incorrectly are common, leaving doubts about quality assurance.

In this way, conventional as-built inspection has required significant time and effort amid labor shortages and has faced issues with coverage and safety. Recently, there has been strong expectation for using ICT and digital technologies to solve these problems, and the Ministry of Land, Infrastructure, Transport and Tourism’s *i-Construction* promotion has accelerated DX (digital transformation) on sites.

How does AR technology change as-built inspection?

So how does AR technology change as-built inspection? The key is real-time verification using a smartphone + high-precision positioning + 3D data. Specifically, attach a small high-precision GNSS receiver (RTK-capable device described later) to a smartphone or tablet and preload design 3D models or drawing data into a dedicated AR app. By positioning yourself with GNSS at centimeter-level accuracy (half-inch accuracy) while overlaying the design data on the camera image, you can superimpose the actual object and the design data on site and check them.

For example, when you point a smartphone, the screen will show the design’s completed shape or reference lines perfectly aligned with the actual structure. Thanks to GNSS-corrected positioning information, the virtual model does not drift away from reality even if the user walks around the site. This changes the inspection process from one where you had to return to the office to compare measurements with drawings to a process of comparing the actual object and data on the spot.

Moreover, by utilizing a LiDAR scanner included in the latest iPhones, you can scan the surroundings on site to obtain high-density point cloud data (a collection of 3D measurement points) and automatically analyze differences from the design 3D model. For example, for a paved road, scanning the pavement with a smartphone to check height variations of the as-built surface can immediately display a color-coded heat map of surface irregularities. If you overlay the generated heat map onto the road in AR, you can intuitively see on site which parts are higher or lower than the design, and immediately proceed to corrective work such as adding or removing fill. What used to be taken back to the office for analysis and reporting can increasingly be verified in real time on site with AR technology.

Benefits and effects of AR inspection

AR-based inspection methods offer various advantages compared to conventional approaches. The main effects are summarized below.

• Significant efficiency gains: Measurement and inspection can be performed by one person in a short time, greatly reducing personnel and work hours. Multiple processes (surveying, as-built confirmation, photography, etc.) can be handled simultaneously with a single smartphone, improving overall site productivity.

• Elimination of missed measurements: Point cloud scanning enables high-density measurement over wide areas and does not miss fine errors that manual methods might overlook. Deviations in as-built conditions can be visualized with heat maps, ensuring detection of quality variations.

• Improved safety: Measurements can be done non-contact even in hazardous locations. By designating a target from a safe, remote position through the camera, you can obtain the 3D coordinates of that point, allowing surveying without forcibly placing equipment in high or narrow areas. This reduces fall risks and the risk of contact with heavy machinery.

• Immediate pass/fail judgment and correction: Measurement data can be analyzed and shared instantly via the cloud, allowing pass/fail judgments on the spot. Site stakeholders can review results together and decide on additional works or corrections immediately if problems are found, minimizing rework and contributing to quality assurance and shorter schedules.

• Digitalization of records: Measurement results and inspection records are automatically saved as digital data, eliminating the effort of transcribing onto drawings or organizing photo ledgers later. If you take AR photos with location information, you can keep chronological evidence of “where and what was constructed.” Report preparation becomes smoother and helps reduce human errors.

• Easy remote sharing: Site visualizations in AR can be shared in real time with remote stakeholders via tablet screen sharing or similar features. This allows understanding of site conditions and issuing instructions without traveling to the site, reducing travel and movement. It also facilitates quicker decision-making.

Is AR inspection accurate and reliable?

When you hear “AR inspection,” you might wonder, “Can it really measure that accurately?” In short, AR combined with high-precision GNSS (RTK-GNSS method) provides sufficiently reliable accuracy. Standard smartphone GPS has meter-level errors, but by using an RTK-GNSS receiver to apply corrections to satellite positioning information, position deviations can be reduced to within a few centimeters (within a few in). In practice, you can obtain a self-position at nearly the same level of accuracy as conventional surveying using dedicated equipment, and the AR display will align precisely with the real object. For example, planar position errors can be within ±2 cm (±0.8 in) and height errors within ±3 cm (±1.2 in). Furthermore, if you properly calibrate the smartphone’s gyro sensor and compass (electronic compass), orientation and angle accuracy will be within a range that does not impede on-site inspection.

What matters is using it in outdoor environments where GNSS reception is stable and ensuring consistency with survey control points. Nowadays, Japan’s QZSS “Michibiki” satellite augmentation signals (centimeter-level positioning augmentation service = CLAS) are also available, making high-precision positioning possible even at sites without internet access. With such technical backing, AR inspection is sufficiently robust in terms of accuracy and reliability for on-site work.

What do you need to start AR inspection?

You may be surprised at how simple the requirements are to practice AR inspection. Basically, all you need is a smartphone or tablet, an RTK-capable small GNSS receiver that attaches to it, and a dedicated app that supports AR functionality. It is preferable to use a smartphone with a LiDAR scanner (e.g., iPhone Pro models), but if not available, photogrammetry can also acquire 3D data. If you use a GNSS receiver that can receive correction information (RTK services) via the internet, you don’t need to set up your own base station. Recently, business-card-sized RTK-GNSS receivers that attach to smartphones have appeared; they connect by Bluetooth and have built-in batteries for cable-free long operation, improving on-site usability. It is also important to prepare the design data to compare in advance and load it into the app. BIM/CIM 3D models or digitized drawing data are best, but for simple cases, inputting coordinate information of design drawings as point data is sufficient for coordinate guidance (AR navigation).

Once prepared, simply take the smartphone + GNSS receiver to the site, launch the app, and perform measurements and AR displays. If positioning accuracy is ensured, the design model will appear aligned with reality on the camera view. Surveying and inspection work that once required bulky equipment and advanced expertise can now be completed with the operation of a smartphone app that anyone can use.

Will AR inspection become commonplace?

Inspections and surveying using AR are still a new initiative, but they are expected to become a site standard in the future. In fact, the Ministry of Land, Infrastructure, Transport and Tourism is promoting ICT utilization in as-built management as part of *i-Construction*, and trials of as-built management using 3D data and remote witnessing (attending inspections online without going to the site) are expanding. Major construction firms have started trials combining BIM models and AR for dimensional inspection of steel frames, demonstrating AR inspection’s usefulness.

In the future, AR and remote inspections will become routine methods, and real-time quality control that transcends the boundary between the site and the office will become commonplace. Parts of the work that relied on the intuition and experience of veteran craftsmen will be objectified by AR’s data displays, reducing dependence on individual skill and allowing anyone to perform inspections at a consistent standard. Currently, AR use mainly involves smartphones and tablets, but wearable devices such as AR glasses are expected to enable inspections without using hands in the future. Of course, high-precision tasks will still use conventional precision instruments in tandem, but for everyday as-built confirmation, a time when it can be completed with a single smartphone is just around the corner.

Conclusion: How to easily start AR inspection

As described above, AR inspection has the potential to dramatically improve on-site productivity and quality assurance. You may still wonder, “What should I start with specifically?” As a first step, we recommend trying simple surveying using a smartphone.

For example, there is a solution called LRTK developed by a startup originating from Tokyo Institute of Technology. By attaching a business-card-sized small RTK-GNSS unit to a smartphone and using a dedicated app, anyone can easily perform centimeter-level positioning and AR verification. An iPhone essentially becomes a high-precision surveying instrument, handling everything from point cloud scanning to AR-based as-built checks with a single device. Even without special skills, you can take it to the site, point the smartphone at the target point, press a button to record coordinates, and immediately check the comparison results with the design data.

Using such tools lets you experience AR inspection on site without large investments. Start with small-scale trials to feel the efficiency and accuracy. Adopt this new AR inspection style and upgrade your site operations to the next stage. Don’t miss the wave of site DX—why not take the first step into AR inspection now?

FAQ

Q: Can the accuracy of as-built inspection using AR really be trusted? A: If combined with high-precision GNSS (RTK method), AR systems can typically achieve position accuracy on the order of a few centimeters (within a few in). For example, planar position errors can be within ±2 cm (±0.8 in) and height errors within ±3 cm (±1.2 in). Standard smartphone GPS has errors of several meters (several ft), but RTK corrections provide survey-grade accuracy comparable to survey control points, so the design data overlaid in AR will match with minimal drift. Proper equipment calibration will also yield sufficiently practical accuracy for orientation and posture.

Q: What preparations and equipment are needed to display AR on site? A: Essentially, a smartphone or tablet, an RTK-capable GNSS receiver that attaches to it, and a dedicated AR app are sufficient. Prepare design 3D models or drawing data in advance and load them into the app. If you use a GNSS receiver that receives correction information via the internet, centimeter-level positioning is possible without setting up a separate base station.

Q: Can AR inspection be used in environments where GNSS cannot be received, such as inside tunnels or indoors? A: Pure GNSS positioning unfortunately does not work where there is no sky view. In such cases, you can perform alignment by referencing pre-installed known points (marker points that serve as references) in AR. For example, in tunnel work you could use coordinates obtained near the entrance to perform relative positioning correction to reference points inside the tunnel and then use that reference for AR displays. Indoors, QR code markers or feature-point markers can be used to correct camera position and enable AR displays.

Q: I’m worried about the cost of introducing AR inspection. Don’t you need expensive equipment? A: It can be started at a much lower cost than purchasing dedicated large surveying instruments. Many people already own smartphones, and small GNSS receivers are relatively inexpensive compared to total stations. Software is often offered as cloud services with flexible licensing for only the required period. Moreover, time savings and personnel reductions bring significant cost benefits, so overall you can expect returns exceeding the investment.

Q: Can people who are not good with machines handle it? Do you need special skills or qualifications? A: No special qualifications or advanced skills are required. Basic operations are not difficult if you follow the app’s guidance. For example, systems like the LRTK mentioned earlier allow you to simply point an antenna-equipped smartphone at the measurement point and press a button to record coordinates, and AR displays are performed by selecting model data from the app menu. However, beginners need to become familiar with equipment handling and calibration procedures, so simple training at introduction is recommended. After using it a few times on site, users will get the hang of it and anyone will be able to use it smoothly.