Table of Contents

• Significance of visualizing underground utilities with AR

• Preventing construction mistakes with AR technology

• Improving inspection accuracy using AR

• Smoothing consensus-building in construction with AR

• Technical elements that support high-accuracy AR

• Simple surveying anyone can do with LRTK

• Summary

• FAQ

Significance of visualizing underground utilities with AR

In recent years, as social infrastructure ages, safely carrying out work without damaging existing underground utilities and enhancing infrastructure maintenance have become major challenges. On construction sites, it is extremely important to accurately grasp the positions of underground utilities such as buried pipes and cables. Accidentally damaging a gas pipe or power line can lead to serious incidents or project delays. Traditionally, workers had to estimate locations on site using drawings, mark the ground with stakes or spray paint, and otherwise rely on time-consuming experience to understand unseen underground conditions. These methods carry risks of markers shifting or being lost, requiring constant vigilance during work. In addition, preparatory test excavations to confirm the positions of utilities can be reduced with AR. If drawings and AR data are accurate, the positional relationships of buried utilities can be understood without digging up the ground, enabling rationalization from the planning stage of construction.

Using AR (augmented reality) technology, structures under the ground can be visualized as if you were seeing through the surface via a camera. By overlaying pre-prepared digital data of underground utilities onto a smartphone or tablet screen, the “visualization” of underground pipes and cables becomes possible. This allows workers to accurately understand subsurface conditions by direct visual reference on site and to proceed with tasks safely and efficiently. AR visualization of underground utilities is attracting attention as a new construction technique symbolizing digital transformation (DX) on construction sites. In short, efforts to make previously invisible things “visible” are becoming the new norm at job sites.

Preventing construction mistakes with AR technology

The most direct benefit of AR visualization of underground utilities is preventing mistakes during construction. Especially in excavation work, knowing at a glance what is buried underground can drastically reduce the risk of accidentally damaging pipes or cables. For example, simply pointing a tablet’s camera at the ground can display underground gas pipes and water/sewer pipes as color-coded lines on the screen. Workers can intuitively grasp what is buried beneath the ground in front of them, carefully adjust excavation locations, and prevent contact accidents with critical lifelines. Repairing damaged utilities can be very costly and have significant impacts on the surroundings, so preventing such incidents is crucial. By making hazardous locations visible in advance with AR, all workers can share the points to watch out for, which also helps raise overall safety awareness on site.

Furthermore, AR is effective not only for dealing with existing utilities but also for preventing installation errors of new structures. When a 3D design model is overlaid on the real site through AR, the “correct positions” where components should be installed are visually indicated. Workers can accurately verify onsite whether components are placed according to the design in AR and immediately detect and correct even small misalignments. For example, in bridge construction when installing columns or anchor bolts, overlaying the 3D model of the design position onto the real world allows even centimeter-scale deviations to be addressed without oversight. Detecting and correcting mistakes on the spot prevents rework later, improving overall construction quality and safety.

Improving inspection accuracy using AR

AR technology also contributes to improved accuracy in inspections of infrastructure and structures. Normally, inspecting and confirming the status of underground utilities requires comparing drawings with on-site conditions or, when necessary, excavating the ground for direct confirmation. With AR, the positions of underground pipes and structures can be accurately understood without such effort, greatly streamlining supervision and inspection tasks. In addition, if the AR-verified information is recorded as photos or videos, the inspection records become more intuitive and easier to understand than paper reports. For example, because you can check the clearance (distance) between excavation points and buried pipes on a tablet in real time during work, on-site marking tasks that used to rely on stakes or paint can be simplified, and inspectors need not repeatedly re-measure distances. Being constantly aware of the positional relationship between excavation machinery and underground utilities in AR improves safety and the reliability of construction, making AR useful for inspections.

AR also excels in the maintenance and management of existing infrastructure. For example, when inspecting aging bridges or tunnels, overlaying past design drawings and records of deterioration onto the current view via AR allows field personnel to accurately identify areas that need repair. Similarly, for maintenance of buried pipelines, previously collected survey data and records of burial positions can be visualized in AR so that the condition and layout of buried pipes can be understood from the surface. This makes it easier to intuitively discover overlooked deterioration or damage, dramatically improving inspection accuracy. AR-based inspections are transforming traditionally experience- and intuition-dependent tasks into data-driven, smart operations. Some sites have already begun using AR for as-built inspections by supervising authorities, improving the efficiency of matching drawings with constructed objects.

Smoothing consensus-building in construction with AR

AR visualization not only enhances safety and quality but also helps smooth consensus-building among stakeholders. For clients, nearby residents, and infrastructure managers who may lack technical knowledge, it can be difficult to understand underground conditions or the post-construction image from drawings alone. However, by pointing a tablet at the site and displaying the arrangement of buried utilities or planned structures in AR, anyone can intuitively grasp the current situation and plans. There is no need to spread multiple paper drawings; showing overlayed images on site makes it easier to gain understanding.

For example, on a site where buried pipes are densely concentrated, explaining the construction status using AR displays during a client walkthrough helps them instantly understand what countermeasures are being implemented underground. Content that previously had to be explained verbally or with drawings can be shown in AR at the site to avoid misunderstandings and secure agreement. Walking through the site while projecting the finished image in AR also makes it easier to obtain consensus at public briefings or meetings with owners. Because information is shared in a visible form, stakeholders’ anxieties and questions can be resolved more readily, which ultimately smooths project-wide communication. AR becomes a powerful on-site communication tool and speeds up consensus-building. During joint inspections with facility managers of buried utilities (such as gas companies or water utilities), confirming burial conditions together with AR allows accurate communication of the area impacted by construction and provides reassurance.

Technical elements that support high-accuracy AR

There are several technical points to accurately visualize underground utilities with AR on construction sites. The most important is registration accuracy. AR displays that rely only on a smartphone’s built-in GPS or compass can show errors of several meters, which is insufficient for precision-demanding civil engineering management. This is where satellite positioning RTK (Real-Time Kinematic) technology comes in. By combining an RTK-capable high-precision GNSS receiver with an AR device, self-positioning can be determined with centimeter-level positioning accuracy of a few centimeters (cm level accuracy (half-inch accuracy)), allowing digital data to be overlaid with almost no offset. In practice, systems have been commercialized where a small RTK-GNSS antenna is attached to a tablet and simply walking the site displays design drawings and utility data perfectly aligned with the real world. Dramatically improving positioning accuracy in this way has made previously difficult ultra-precise AR displays possible. Note that in environments where GNSS signals cannot be received, such as inside tunnels or under elevated structures, SLAM (Simultaneous Localization and Mapping) techniques that use camera images or LiDAR sensors to capture surrounding feature points are sometimes combined to complement AR display accuracy.

Equally essential is preparing the digital data of the underground utilities to be shown in AR. It is necessary to prepare 3D models from original design drawings, CAD data, and GIS geographic information and align them for AR use. With the spread of BIM/CIM in recent years, three-dimensional design and construction data are being organized, and the trend of bringing these to the field for AR use is accelerating. However, if positional information of buried utilities is inaccurate or models are outdated, what AR displays will not match reality. Therefore, it is important to grasp the actual positions of buried utilities through high-accuracy surveys and update the data to the latest versions. Recently, tools have emerged that enable easy high-precision point cloud surveying or photogrammetry on site and immediately reflect that data in AR displays. Combining these technical elements is making it increasingly possible for anyone to perform high-accuracy AR visualization easily. The Ministry of Land, Infrastructure, Transport and Tourism’s i-Construction initiative also recommends the use of ICT and 3D data, and AR-driven construction DX is expected to spread further.

Simple surveying anyone can do with LRTK

LRTK has emerged as a solution to easily realize such high-accuracy AR visualization on site. LRTK is a system consisting of an ultra-compact RTK-GNSS receiver that attaches to the back of a smartphone and a dedicated app, and it is characterized by delivering centimeter-level positioning accuracy the moment you power on the device. Unlike other AR surveying tools, there is no need to place markers in advance or perform complicated manual coordinate alignment. By snapping on a smartphone case that contains the small receiver (weighing about 125 g, thickness 13 mm (0.51 in)), your everyday smartphone instantly becomes a high-precision positioning device. Because high-accuracy AR can be used without difficult initial setup, it can be operated on site even by non-specialist surveyors.

With LRTK, acquired data is reflected in the device app via the cloud in real time, allowing design models and survey data to be shared on site instantly. Allowing anyone to easily acquire centimeter-accurate point cloud data and display AR directly leads to reduced construction mistakes and faster surveying tasks. In practice, by using LRTK, single smart devices per person can handle tasks from simple surveying to layout marking, inspection, photo recording, and even AR simulation of as-built conditions, and reports indicate dramatic improvements in site productivity. Also, sharing the finished image in AR while walking the site with clients and stakeholders facilitates immediate discussion and confirmation, smoothing consensus-building. LRTK is making high-accuracy surveying and AR technology that once required specialists accessible to anyone in the form of simple surveying.

Summary

The AR technique for visualizing buried utilities reveals significant benefits for construction sites. From preventing human error during excavation to improving construction quality and smoothing stakeholder communication, it offers advantages across the board. Environmental benefits are also expected, such as reducing waste from fewer construction mistakes and achieving paperless workflows through digital drawings. By overlaying digital data onto the real world, site management that once relied on the intuition and experience of skilled workers is shifting toward smart construction where anyone can make objective, data-based decisions. With simple, high-accuracy tools like LRTK that have appeared in recent years, the barriers to using AR technology are lowering, and the era when AR is commonplace on site is near. Future construction sites in which underground utilities are visualized in AR while work proceeds will see dramatic improvements in safety and productivity and may become a new standard in the construction industry. In the future, using AR glasses (spectacle-type devices) so that workers always have the positions of buried utilities displayed in their field of view while working may become commonplace.

FAQ

Q: What do I need to prepare to visualize underground utilities with AR? A: Basically, you need digital data that includes the positions of buried utilities and an AR-capable device to display that data on site. For example, if you have drawing data of buried pipes or cables (CAD or GIS data), you can import it into an AR app on a tablet or smartphone and display it on site. To align overlays accurately, it is ideal to use a receiver that supports high-precision GNSS (RTK). Recently, small GNSS receivers that attach to smartphones (such as LRTK) have appeared, making it easy to achieve high-precision AR visualization without specialized surveying equipment.

Q: How accurate is AR display of underground utilities? A: When combined with high-precision GNSS positioning, AR displays can show underground utilities with errors on the order of a few centimeters. Positioning that relies only on standard GPS could be off by several meters, but using RTK allows models to be overlaid almost exactly as shown on drawings. However, in locations where positioning satellites cannot be received (such as inside tunnels or under elevated structures), errors may increase. In such cases, combining SLAM (self-positioning using cameras or LiDAR) helps correct positions as accurately as possible. The precision required for construction management can be sufficiently secured.

Q: Can it be used on site without specialized knowledge or expensive equipment? A: Yes, with modern solutions it is possible. For example, combinations of a small device that attaches to a smartphone and an app—such as LRTK—allow intuitive operation by anyone. Previously, high-cost equipment like total stations or dedicated AR glasses and specialized skills were required, but now AR visualization can be performed easily using everyday smartphones or tablets. Systems are becoming so simple that site workers can begin using them after brief instruction. User interfaces are also designed to be intuitive for workers, and there are increasing cases where short training is sufficient for on-site use.

Q: What kinds of underground utilities can be visualized with AR? A: There is no limitation on the types of utilities. All buried lifelines such as gas pipes, water pipes, sewers, power cables, and communication cables can be visualized. As long as their positional information exists as digital data, they can be displayed in AR. New installations can provide data from construction drawings, and for existing utilities without drawings, methods such as magnetic detection or test excavations can confirm positions and then convert them into data using point cloud scans with LRTK. Once digitized, the information can be reused repeatedly in AR displays.

Q: Is this AR technology already widely used? A: In Japan, some major construction companies have begun trialing AR displays of buried utilities on sites and have reported results. Overseas, high-precision outdoor AR systems are also attracting attention. Products like LRTK that anyone can use are being commercialized, and usage is expanding beyond specially conditioned sites to general construction sites. With support from national and industry organizations, AR-based construction management is expected to become even more widespread and may become a standard tool on sites. Government initiatives such as the Ministry of Land, Infrastructure, Transport and Tourism’s i-Construction promotion are helping AR adoption become established as a new norm on construction sites.

Q: Is it cost-effective to introduce AR technology? A: Initial investment is required for equipment and data preparation, but the benefits can outweigh those costs. Preventing damage to buried utilities reduces the risk of large compensation costs and schedule delays, and efficiency gains can reduce labor costs and shorten project durations. There are reports of substantial time savings from automating tasks like piling guidance and as-built inspections using AR. Furthermore, smartphone-based solutions reduce the cost burden compared to specialized equipment, and from a mid- to long-term perspective, cost-effectiveness is achievable. AR can also prevent rework and claims caused by misunderstandings among stakeholders, so the introduction has significant benefits in that regard as well. Considering these effects, adopting AR is well worth consideration.