AR Inspection vs Traditional Methods: How Does Efficiency in As-Built Inspections Change?

Table of Contents

• Introduction

• What Is an As-Built Inspection? A Review of Traditional Methods

• What Is an As-Built Inspection Using AR?

• Efficiency Benefits Brought by AR Inspections

• Challenges and the Future of AR Inspection Adoption

• Simple Surveying and AR Inspection Realized with LRTK

• Frequently Asked Questions

Introduction

In the construction industry, methods of construction management have been undergoing major changes in recent years with the promotion of ICT and DX (digital transformation). However, in actual field conditions, surveying and as-built inspections still require a great deal of time and effort, and labor shortages and the aging of technical staff remain major challenges. As the need to carry out work efficiently with limited personnel increases, AR (augmented reality) technology has attracted attention as a trump card to solve these problems.

By using AR technology, you can overlay digital information such as design drawings and 3D models onto real-world footage, enabling construction management tasks that previously relied on manual labor and experience to be performed intuitively and digitally. In particular, with recent improvements in the performance of smartphones and tablets, handheld devices have begun to act like “all-purpose surveying instruments.” By combining the latest devices equipped with high-performance cameras and LiDAR sensors with high-precision GNSS and RTK positioning (real-time kinematic) technology, even non-experts can increasingly perform highly accurate surveying and as-built checks on site.

This article compares AR inspections (as-built verification using AR) with traditional methods in as-built inspections and explains how efficiency changes. We comprehensively review the challenges of traditional methods, the benefits of introducing AR, key points for field implementation, and future prospects. At the end of the article, we also touch on LRTK, a new simple surveying solution that combines AR technology with RTK positioning, and offer tips for improving field efficiency.

What Is an As-Built Inspection? A Review of Traditional Methods

An as-built inspection is a quality control process in civil engineering and construction that verifies whether the completed structures or topography have been constructed according to the design drawings. Traditionally, this as-built verification commonly used surveying instruments such as total stations (TS) and levels to measure heights and thicknesses point by point on site, and the collected data was taken back to the office to be compared with drawings for pass/fail judgment.

However, with this method there is often a time lag between measuring on site and discovering discrepancies when comparing with drawings, which tends to lead to rework of already constructed areas if defects are found. Precise measurement and judgment require experienced survey technicians, and work often needs two people, so in the context of chronic labor shortages and an aging workforce this becomes an inefficient process. Verifying as-built conditions over a wide area requires measuring many points, and inspections can take several days. Furthermore, because measurements were recorded by hand and later transcribed to drawings, there was a risk of human error. Improving the efficiency of these traditional methods has been an ongoing challenge at construction sites.

What Is an As-Built Inspection Using AR?

An as-built inspection using AR (augmented reality) is a method that overlays 3D digital information such as design data and drawings onto the real-world site view to intuitively verify as-built conditions on the spot. Previously this was limited to advanced attempts using specialized equipment, but recently the improved performance of smartphones and tablets has made it practical for everyday site management. Modern phones and tablets are equipped with high-performance cameras and LiDAR sensors, and by using dedicated AR apps you can compare the design model on the drawing with the physical construction in real time.

For example, if you display a 3D model of the finished drawing in AR through a tablet’s camera, you can instantly tell whether the finished shape of an embankment or pavement thickness matches the design. Discrepancies between the real object and the digital model are displayed as color-coded heat maps on the spot, making areas of deficiency or excess immediately apparent. Without using surveying instruments to measure heights point by point, you can intuitively grasp as-built information simply by holding up a device, enabling you to check quality immediately after construction and take corrective action right away.

Such AR as-built inspections are gaining attention within the construction DX movement promoted by the Ministry of Land, Infrastructure, Transport and Tourism’s i-Construction initiative (https://www.mlit.go.jp/tec/i-construction/). They are expected to be a powerful solution that simultaneously improves site efficiency and quality, and proof-of-concept trials and deployments at actual sites are progressing.

Efficiency Benefits Brought by AR Inspections

Introducing AR technology into as-built inspections yields many benefits not available with traditional methods. The main efficiency points are summarized below.

• Real-time problem detection: AR allows defects and deviations from the design to be discovered immediately on site, enabling immediate corrective action. For example, if deficient areas in pavement thickness or slope are color-coded on AR right after construction, additional work or trimming can be performed that same day. Being able to run PDCA on site immediately minimizes rework and prevents quality defects from being left unaddressed.

• Reduced work time and labor savings: Traditional work of measuring and recording points with paper drawings and surveying instruments is replaced by an intuitive process of scanning the site with a tablet. Because wide-area as-built conditions can be “visualized” at once, inspections that used to take several days can be dramatically sped up. Also, one person can complete measurement and verification, reducing personnel coordination and saving labor.

• Addressing labor shortages: Site staff can evaluate as-built conditions on the spot without relying on specialized surveyors or veteran technicians. AR apps are simple to operate, and measurements are completed by following on-screen instructions, so special skills are unnecessary. This creates a system that does not depend on individual technicians’ experience, allowing younger staff to perform site inspections even when experienced personnel are lacking.

• Cost reduction: AR inspections using smartphones or tablets eliminate the need to purchase expensive TS or GNSS surveying equipment. Dedicated surveying instruments can require initial investments in the millions of yen, but nowadays a centimeter-level measurement environment (half-inch accuracy) can be built by combining existing mobile devices with relatively inexpensive GNSS receivers. Maintenance and transport costs for equipment can also be reduced, enabling low-cost deployment.

• Improved measurement accuracy and reliability: Using AR reduces reading and recording mistakes caused by manual work. There is no need to transcribe measurements on site, and digital data can be directly compared to eliminate human error. Furthermore, combining AR with high-precision positioning technologies such as RTK-GNSS ensures measurement results are consistently in the centimeter range (centimeter-level accuracy (half-inch accuracy)). This enables more reliable as-built verification than traditional methods.

• Streamlined recording and reporting: AR inspection results can be recorded visually, making report creation easier. For example, attaching screenshots of the AR screen or differential heat map images to reports produces much clearer documentation than conventional lists of numbers. In fact, Ministry of Land, Infrastructure, Transport and Tourism proof-of-concept trials confirmed that AR use can simplify submitted as-built documentation. Because records are retained as digital data, later verification is easy and reporting burdens are reduced.

• Improved consensus building and communication: The “visualization” of the site via AR also helps share information with clients and site stakeholders. Showing the design model overlaid with the construction via tablet during inspections makes explanations smoother. Displaying as-built conditions on AR reduces misunderstandings and enables immediate agreement on corrective areas. The ministry’s survey reports note that AR is beginning to be used not only for construction management but also for pre-construction briefings for residents and information sharing with subcontractors. Such improved communication contributes to efficiency and quality improvement across operations.

Note: In actual sites where smartphone AR surveying was introduced, cases have been reported where as-built measurements that used to take more than half a day were completed in 30 minutes. The amount of information and speed obtainable by a single worker increases dramatically, prompting remarks that it is “as if manpower has doubled.”

Challenges and the Future of AR Inspection Adoption

At present, there are some points to note when applying AR-based as-built inspections to official inspection procedures. Traditional as-built management guidelines may require parallel measurements and drawing creation using conventional methods as well as AR, and some supervising officers (inspectors) are cautious about accepting pass judgments based solely on digital checks on a tablet. However, the Ministry of Land, Infrastructure, Transport and Tourism confirmed in fiscal 2023 field trials that AR technology can allow omission of certain as-built documents, and AR-based labor-saving methods are expected to be incorporated into official guidelines going forward.

In practice, even now, software that can automatically create as-built documentation (drawings and reports) from point cloud data or photos obtained by AR can produce deliverables comparable to manual drawing creation. In other words, with some ingenuity it is becoming possible to complete as-built inspections using AR measurements alone. The important thing is to properly explain AR-derived results to clients and inspectors and gain their understanding. For example, showing the as-built heat map directly on a tablet during an inspection will prove quality more convincingly than paper drawings. With both public and private sectors deepening their understanding of AR use, accumulating on-site AR know-how ahead of others is likely to become a major advantage in the future.

Simple Surveying and AR Inspection Realized with LRTK

One solution attracting attention for realizing AR as-built checks more easily and with higher accuracy is LRTK. LRTK is a cutting-edge tool that enables centimeter-class high-precision positioning (half-inch accuracy) via RTK simply by attaching a small GNSS receiver to a smartphone. It is a next-generation system that allows surveying work that traditionally required specialized equipment and experienced operators to be completed by one person, and it supports Japan’s quasi-zenith satellite “Michibiki” CLAS corrections and network RTK. Therefore, stable high-precision positioning is possible even in mountainous areas outside of communication zones. In short, even without a veteran surveyor, LRTK’s great strength is that you can perform everything from control point surveying to as-built measurement (inspection) with just a smartphone.

Moreover, LRTK integrates seamlessly with AR functions. Because accurate position information obtained from high-precision GNSS can be used, 2D and 3D design data can be overlaid on site images without shifting, eliminating troublesome alignment tasks and worry about objects drifting. For example, simply walking the site with a tablet can accurately indicate the virtual staking positions from the design model on the actual ground. You can confirm target coordinates at a glance even for distant points and efficiently give staking instructions for multiple locations. It is also possible to automatically overlay the acquired point cloud data of the current condition with the design model on the LRTK cloud and perform differential comparisons to instantly check whether construction matches the plan.

LRTK also provides a cloud platform, allowing site measurements and scans to be synchronized to the cloud immediately. Team members can view the site’s 3D point cloud and measurement point information in real time from office PCs, enabling collaborative verification with all stakeholders sharing data. On the cloud, you can perform distance, area, and volume measurements, or link photos with location information and display them as a list with a single click. This enables real-time collaboration across site and office boundaries, dramatically improving 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 single user to staking positions, a function to calculate embankment volumes from LiDAR-scanned point clouds, and a function to share highly accurate geotagged photos in the cloud. In other words, it is designed so that surveying, as-built measurement, recording, and inspection—processes that used to require multiple devices—can be completed with an iPhone alone. Data acquired on site can also be used and delivered in formats that comply with the Ministry of Land, Infrastructure, Transport and Tourism’s as-built management guidelines, and many construction companies have already started adopting LRTK to achieve both labor savings and quality improvement.

By using LRTK, a smartphone surveying + AR system, anyone can easily conduct high-precision as-built checks and overcome various constraints related to surveying and inspection. Even on sites struggling with labor shortages, combining a “one-per-person” smart surveying tool with AR can shorten work time, suppress human error, and improve communication. These technological innovations strongly support construction site DX and are fundamentally changing as-built management. To maximize the effects of AR inspection, it is crucial to proactively adopt such advanced tools and connect them to overall productivity improvements on site. Embrace the latest technologies and let AR inspections demonstrate their true value at your sites.

Frequently Asked Questions

Q: What do I need to start as-built AR inspections? A: Basically, you need a smartphone or tablet capable of AR display, a GNSS receiver to improve measurement accuracy, and an AR surveying app that supports them. Recent iPhone and Android devices have high-performance cameras and sensors suitable for AR use. If centimeter-level accuracy (half-inch accuracy) is required, combine a small Bluetooth-connected GNSS rover for RTK positioning (examples include LRTK devices that can be attached to a smartphone). In addition, prepare digital information to use for comparison, such as the design-side 3D model data or as-built point cloud data. With these set up, you can immediately try AR inspections on site.

Q: Can the accuracy of AR as-built inspections be trusted? A: Yes—if properly operated, high accuracy and reliability can be ensured. Systems using GNSS RTK corrections can achieve positioning accuracy with errors on the order of a few centimeters (a few inches) in both horizontal and vertical directions. This is within the accuracy range typically required for as-built inspections. When confirming differences on AR, you can obtain quantitative information such as “this point is X cm higher/lower” via heat map displays. The important thing is to align site control points with AR coordinates in advance and, when necessary, supplement with conventional methods at key points for verification. Doing so will provide sufficient backing to trust AR inspection results.

Q: Can AR be used at sites that don’t have a 3D design model? A: Even without a 3D model, AR can be used with some creativity. For example, there are apps that overlay 2D drawing data (DXF, etc.) in AR space so key lines and positions can be visualized on site. If the finished shape is relatively simple, a simple method is to mark key dimensions on site before construction and then compare those marks with AR-captured images. However, AR’s true value is best realized when a 3D model is available. Recently, 3D design data such as CIM is increasingly being prepared for public works, so consider asking the client to provide 3D data or create a simple model in-house. On the other hand, if you only need to compare measured as-built data with design drawings, you can detect differences using point-cloud-processing software without forcing AR. The goal is to enable intuitive on-site confirmation, so choose the optimal approach depending on whether a model is available.

Q: Can AR inspection results be used for official inspections? A: At present, operations that rely solely on AR as the only basis for official inspection are just getting started, but recognition is gradually increasing. The Ministry of Land, Infrastructure, Transport and Tourism conducted field trials in fiscal 2023 and confirmed that AR technology can allow omission of certain as-built documents. Currently, parallel records using conventional methods (inspection drawings and photo logs) are often requested, but submitting AR verification results as supplementary material can help inspectors understand the situation more easily. For example, showing on an AR heat map that “this point is X cm higher/lower than the design” conveys the information more intuitively than a conventional numerical table. In the future AR data itself may be accepted as an official deliverable, but at this stage it is safer to use AR as supporting evidence and combine it with conventional measurements as needed.

Q: I’m worried that not everyone on site will be able to use this technology. A: AR construction support tools are becoming more user-friendly every year, and basic operations are not difficult. In fact, many companies that have introduced them report that staff from juniors to veterans can use them after short training. If concerns remain, start by having an experienced operator demonstrate on site while other staff observe and get a feel for it. People are more likely to adopt a technology when they see its benefits firsthand. If they can say “it’s really faster” or “it’s easy to understand,” resistance will fade. Many recent AR apps support Japanese interfaces and have solid support systems, making it easy to get help when needed. As site DX continues to advance, aim to gradually create an environment where everyone can use the tools without rushing.

Q: Do I need to use dedicated AR glasses? A: Currently, smartphones and tablets are sufficient and practical in most cases. See-through AR smart glasses have emerged, but they tend to be very expensive and may be difficult to use with hard hats (helmets). Smartphones and tablets, on the other hand, can be used on site in dustproof/waterproof cases and are easy to operate via touch. Screen resolution and processing performance continue to improve, and handheld devices are already suitable for business use. If glasses become lightweight and affordable in the future, their use may expand, but for now AR with handheld devices is the most realistic and cost-effective approach. We recommend starting with familiar smartphone AR and considering glasses later if needed.