Labor savings with AR inspections: Efficiency techniques for as-built inspections that even veterans will accept

Table of contents

• What AR inspection is

• Traditional as-built inspections and their challenges

• Technologies that make AR inspection possible

• Benefits brought by AR inspection

• Field use cases of AR inspection

• Points for introduction that convince veterans

• Using LRTK to achieve simple surveying

• Frequently asked questions

What AR inspection is

In construction sites, "AR inspection" is a new inspection method that uses augmented reality (AR) technology to confirm and evaluate as-built conditions on the spot. Traditionally, as-built inspections were carried out using surveying instruments such as tape measures, levels, and total stations, but AR inspection overlays the information of design drawings and 3D models onto the real world through a smartphone or tablet camera to perform checks. For example, by displaying design lines or reference planes in AR on completed terrain or structures, you can judge at a glance whether the work matches the drawings. By overlaying digital information on the real-world video, confirmation tasks that used to require comparing drawings and the site can be performed intuitively and quickly. AR inspection is now attracting attention as a trump card to realize labor savings in as-built management, and its usefulness is being highly anticipated even by veteran technicians.

Traditional as-built inspections and their challenges

First, to understand why AR inspection is being sought, let us organize the challenges of traditional as-built inspection methods.

• Labor- and personnel-intensive: As-built inspections are usually performed by a team of multiple people, such as surveyors, and for wide construction areas, measuring each survey point can take a whole day. Especially for advanced surveying, skilled technicians are indispensable, and with labor shortages and an aging workforce progressing, securing the necessary personnel and efficiently conducting inspections is not easy. Also, a time lag often occurs between measuring on-site and comparing with drawings in the office to make pass/fail decisions, which delays discovery of nonconforming areas and causes rework.

• Risk of omissions and oversights: Manual sampling measurements limit the number of measurement points and cannot cover the entire construction area. Checking only a limited set of representative points may miss areas that differ from the design. The larger the structure, the harder it is to grasp subtle unevenness or dimensional variations, and in some cases, discrepancies are pointed out at the final inspection stage and rework is forced.

• Possibility of human error: In busy sites, human errors such as forgetting to take photos, miswriting measured values, or transcription mistakes in records tend to occur. For example, if photos are forgotten before backfilling buried objects, there is a risk of being unable to prove the as-built condition. Such human errors have led to quality troubles, and traditional methods imposed heavy burdens and anxiety on site personnel.

Because of these challenges, a new method that can perform as-built inspections more efficiently and reliably has long been sought. Recently, amid labor shortages and work-style reforms, there is strong expectation for the use of new technologies from the perspectives of labor reduction and productivity improvement. One of the promising solutions drawing attention is the application of AR technology.

Technologies that make AR inspection possible

The key that emerged to solve traditional challenges is the fusion of AR technology and high-precision positioning technology. In recent years, the combination of small GNSS receivers that attach to smartphones or tablets and dedicated apps has made it easy for anyone to achieve centimeter-level positioning. RTK (Real Time Kinematic) GNSS positioning can correct satellite positioning errors to within a few centimeters (within a few inches). Precision positioning that previously required expensive surveying equipment can now be obtained in real time with a handheld mobile device.

If you can accurately know your own position, spatial comparisons with design data become possible. By loading design 3D models or drawing data into an AR-capable app and aligning them with the site coordinate system, design information can be displayed over the camera image in the correct position. The combination of a smartphone’s camera and sensors with high-precision GNSS allows virtual lines and planes to be projected into the real world without noticeable offset, enabling detection of discrepancies between actual construction and design on the spot. The latest smartphones also feature high-performance cameras and LiDAR sensors, and AR apps that utilize these capabilities are creating an environment where you can intuitively check as-built conditions on site.

This use of AR is not an eccentric attempt but aligns with major industry trends. The Ministry of Land, Infrastructure, Transport and Tourism (MLIT) is promoting the introduction of BIM/CIM and 3D measurement technologies as part of the i-Construction initiative, and in 2022 revised the as-built management guidelines to formally recognize 3D as-built measurement by smartphones and other devices. Also, in Reiwa 6 (2024) a notice was issued that a new method will be trialed in direct-managed projects where 3D models created during construction are projected on site in AR to measure as-built conditions on the spot. The shift to digital inspections that do not rely on paper drawings and manual work has begun, and AR-based as-built inspection can be seen as a smart construction initiative that fits the trend of construction DX.

Benefits brought by AR inspection

Introducing AR technology to as-built inspection yields many benefits not available with traditional methods.

• Discover problems in real time: Because construction defects and differences from the design can be detected immediately on site, corrective measures can be taken right away. For example, if insufficient pavement thickness or embankment height is color-coded in AR immediately after construction, additional filling or trimming can be performed the same day. Because PDCA can be run on site instantly, rework can be minimized and leaving quality defects unaddressed can be prevented.

• Reduced work time and labor savings: Tasks that involved measuring point-by-point with surveying instruments while holding paper drawings are replaced in AR by intuitive checks where you simply hold up a tablet. Since a wide area can be visualized at once, inspections that used to take several days can be drastically sped up. Also, because measuring and checking can be completed by a single person, personnel arrangement becomes simpler, contributing to labor savings.

• Anyone can measure without relying on skills: AR app operations are simple, and following on-screen instructions completes the inspection. Site personnel can evaluate as-built conditions themselves without relying on specialized surveyors or veteran staff. Because it can be handled without special expertise, it prevents knowledge becoming person-dependent, and even less experienced staff can measure and check. This contributes to solving labor shortages and transferring skills.

• Cost reduction: AR using smartphones or tablets eliminates the need to newly purchase total stations or high-performance GNSS surveying instruments. Dedicated surveying instruments used to require initial investments on the order of several million yen, but nowadays a high-precision positioning environment can be built at low cost using handheld mobile devices and relatively inexpensive GNSS receivers. Maintenance and transportation costs of equipment can also be reduced.

• Improved measurement accuracy and reliability: Using digital technology reduces errors and recording mistakes associated with manual measurements. Since there is no need to copy numbers by hand on site, measurement data can be compared directly, eliminating human error. Moreover, when combined with high-precision positioning such as RTK-GNSS, results consistently match public coordinate systems with centimeter-level accuracy (cm-level accuracy (half-inch accuracy)), enabling more reliable as-built verification than before.

• Streamlined record-keeping and reporting: AR inspection results can be saved as visual materials such as screenshots and difference heat maps. Attaching these to inspection reports makes them easier to understand than traditional reports that list only numbers. In MLIT field demonstrations, it was also confirmed that AR use can simplify required submission documents like as-built drawings. Since all records are stored as digital data, retrospective checks are easy and reporting workload is reduced.

• Improved consensus-building and communication: AR visualization is powerful for information sharing both inside and outside the site. For example, by holding up a tablet during construction to show completion imagery or inspection results, you can intuitively convey the situation to clients and inspectors. Content that was difficult to communicate with drawings and numbers alone becomes easier to understand when visualized on site, making it easier to gain stakeholder understanding. This can enable smooth consensus-building across site and office, and between general contractors and subcontractors.

Field use cases of AR inspection

So how is AR inspection actually conducted in the field? As an example, let us look at checking ground elevation in a land development project.

To confirm whether the finished ground elevation matches the design, the dedicated app displays a virtual finished elevation reference plane. On the tablet screen, the camera image is overlaid with the “design elevation reference plane” shown as a translucent plate. As the operator walks the development site watching that screen, it becomes immediately obvious whether the actual ground is higher or lower than the virtual plane. Where the virtual plane appears to float above the ground indicates insufficient filling, while where it appears to sink into the ground indicates excess filling (height exceedance).

For example, if the virtual plane is floating 5 cm (2.0 in) above the ground at a certain point, you can judge that “+5 cm more fill is needed.” Some AR apps display that difference value as guidance, allowing workers to be instructed with numbers such as “add +5 cm (+2.0 in)” at that point. Since visible discrepancies can be shared immediately on site, earthwork operators can understand intuitively and promptly add soil. As a result, the target elevation was achieved without rework.

By using AR inspection in this way, you can ensure construction quality by repeatedly performing on-site verification and correction in real time. After inspection, the status of each checked point can be saved from the app to the cloud as geotagged photos, allowing you to review in the office later exactly where and how much rework was done. Also, if you obtain point cloud data of the ground surface with LiDAR scanning, you can automatically generate a heat map (a color map showing elevation differences) from it and easily compile it into reporting materials.

This AR-based as-built verification method can be applied to various cases, such as verifying pavement thickness and slope in paving work, or confirming position and elevation when installing structures. In all cases, the major advantage is that problems are identified and addressed on the spot rather than being discovered later.

Points for introduction that convince veterans

When introducing new technology to the site, experienced veterans in particular may initially be skeptical. However, if they see the effectiveness of AR inspection firsthand, they are likely to be convinced of its convenience. The key is to demonstrate actual results on site and share them.

It is effective to have interested staff such as younger personnel try AR inspection first and let other members observe. Sharing concrete success stories like “I could see the unevenness at a glance” and “the inspection finished so quickly” can significantly change attitudes. People tend to take a positive approach once they confirm the benefits with their own eyes. If veterans actually feel “indeed it’s faster” or “it’s easier to understand,” resistance will fade.

Fortunately, recent AR surveying apps support Japanese and have robust support, and operation is intuitive and not difficult. Many adopting companies report that staff from young to veteran can master the apps with short training. If concerns remain, start with a trial operation on site where experienced users support others, and gradually expand users. The important thing is to share the new technology across the site and make it their ally. AR inspection does not deny human intuition or experience; rather, it is a tool that enhances site capabilities by combining craftsmanship and digital technology. By leveraging veterans’ knowledge while flexibly adopting new methods, both labor savings and quality improvement can be achieved.

Using LRTK to achieve simple surveying

One solution gaining attention for enabling this kind of AR as-built checking to be both easy and highly accurate is “LRTK.” LRTK is a cutting-edge tool that enables centimeter-level positioning by the RTK method simply by attaching a small GNSS receiver to a smartphone, allowing surveying work that previously required specialized equipment and skilled operators to be completed by one person.

LRTK also seamlessly integrates with AR functions. Based on the position information from high-precision GNSS, 2D/3D design data can be precisely overlaid on site, eliminating the cumbersome alignment work and concerns about virtual object offsets. For example, simply walking the site with a tablet can accurately indicate the virtual pile-driving positions from the design model on the ground, allowing target coordinates to be visually confirmed even at distant points. It is also possible to automatically overlay acquired point cloud data of the current conditions and the design model on LRTK’s cloud for difference comparison, enabling an immediate check of whether construction is proceeding as planned.

LRTK also provides a cloud platform where field-measured or scanned data is synchronized to the cloud on the spot. Team members can view the site’s 3D point cloud and measured point information from office PCs in real time and proceed with verification while sharing data among stakeholders. On the cloud you can measure distances, areas, and volumes, and link photos with location information for list display with one click. This enables collaboration across site and office boundaries and dramatically improves the efficiency of as-built inspections.

In addition, LRTK offers a variety of features beyond as-built management, such as a “coordinate navigation” function that guides a pile-driving position for one person, a function to calculate embankment volumes from LiDAR-acquired point clouds, and high-precision geotagged photo sharing. In other words, it is designed so that surveying, inspection, recording, and as-built inspection—tasks that previously required multiple instruments—can be completed with a single smartphone. The data acquired on site can also be used and delivered in formats compliant with MLIT’s as-built management guidelines, and many construction companies have begun adopting LRTK to achieve both labor savings and quality improvement.

By using such smartphone surveying + AR systems, anyone can easily perform highly accurate as-built checks and overcome various constraints related to surveying and inspection. Even sites struggling with labor shortages can shorten work time, suppress human errors, and improve communication through one-person-per-device smart surveying tools and AR usage. These technological innovations strongly support construction site DX and are fundamentally changing the way as-built management is done. The key to succeeding with AR inspection is to incorporate such advanced tools well and link them to overall site productivity improvements. Please make the latest technologies your ally and let “AR inspection” demonstrate its true value at your sites.

※ For more details about LRTK, please also visit the [LRTK official site](https://www.lrtk.lefixea.com).

Frequently asked questions

Q: What do I need to start AR inspection? A: Basically, you need a smartphone or tablet capable of AR display, a GNSS receiver to improve measurement accuracy, and a compatible AR surveying app. Modern iOS/Android devices have high-performance cameras and sensors suitable for AR use. When centimeter accuracy is required, combine with a small Bluetooth-connected RTK-GNSS receiver to improve positioning accuracy (examples include smartphone-mounted LRTK devices). Also prepare digital design data for comparison (3D models from BIM/CIM or 2D drawings). With these set up, you can immediately try AR inspection on site.

Q: Is AR inspection accuracy reliable? A: Yes, with proper operation it can provide high reliability. Systems using RTK-GNSS positioning corrections can achieve positioning accuracy of a few centimeters in both horizontal and vertical directions, which falls within the accuracy required for typical as-built inspections. When checking differences in AR, heat map displays and the like allow you to obtain quantitative information such as “which point is how many cm high/low.” The important points are to align site control points and data beforehand and, if necessary, use traditional methods for verification in parallel. Doing so will provide sufficient basis to trust AR inspection results.

Q: Can AR inspection results be used in official inspections? A: Currently, using AR alone as the sole basis for official inspection is just beginning, but its use is expected to be gradually accepted. MLIT conducted field demonstrations in FY2023 and confirmed that AR use can make it possible to simplify as-built documentation. Today, many cases still require submission of records via traditional drawings and photo logs, but submitting AR confirmation results as supplementary materials can help inspectors understand the situation more easily. For example, showing on an AR heat map that “this point is ◯ cm higher/lower than the design” is more intuitive than presenting only a numeric table. While there is a significant possibility that AR-acquired data itself will be accepted as official deliverables in the future, at this stage it is recommended to use AR in combination with traditional measurements to be safe.

Q: I’m worried whether everyone on site can master this technology. A: AR construction support tools are becoming more user-friendly year by year, and basic operations are not difficult. In practice, many adopting companies have staff from young to veteran able to use them after short training. If concerns remain, start with a skilled operator demonstrating on site while others observe. People tend to be positive once they see the benefits for themselves. If they can feel “indeed it’s faster” or “it’s easier to understand,” resistance will fade. Recent AR apps also support Japanese and have good support services, so you can get help when needed. Digitalization at sites will continue to progress, so proceed calmly and step-by-step with environment setup.

Q: Do we need dedicated AR glasses? A: At present, smartphones and tablets are sufficiently practical. See-through AR glasses (smart glasses) have emerged, but they are very expensive and have issues such as difficulty using them with safety helmets. Smartphones and tablets, on the other hand, can be used on site easily in dust- and water-resistant cases, and operations are simple via touchscreens. Device screen resolution and processing performance are improving year by year, and handheld devices offer adequate visibility and performance for business use. In the future, if glass-type devices become lightweight and affordable, they may become widespread, but currently handheld device AR is the most realistic and cost-effective option. We recommend starting with familiar smartphone AR and considering future device expansion as needed.