AR Revolution at Infrastructure Sites! Improve Construction Efficiency with Buried-Pipe AR Display

Table of Contents

• The problem of underground utilities being "invisible"

• Technology to visualize buried pipes with AR

• Workflow for using buried-pipe AR displays

• Benefits of improved construction efficiency through buried-pipe AR use

• Field cases and future developments

• Conclusion: Simple surveying and AR display enabled by LRTK

• FAQ

Underground utilities that support social infrastructure—such as water supply pipes, gas pipes, and power cables—are hidden beneath the ground and are not normally visible, making the presence of buried objects a major issue at construction sites. If pipes are accidentally damaged, it can lead to serious accidents such as water leakage, gas leaks, or power outages. Traditionally, buried utilities have been managed with as-built drawings, markings on the ground, and the experience of veteran workers, but it is not easy to fully grasp the locations of complexly intersecting underground structures, and unexpected excavation accidents continue to occur.

However, in recent years AR (augmented reality) has attracted attention as a technology that “makes the invisible visible.” In particular, “buried-pipe AR display” combined with high-precision positioning technology RTK-GNSS enables visualization of pipelines deep underground as if seeing through the ground on site. If workers can intuitively grasp the status of buried pipes at the site, safety measures will improve dramatically, and unnecessary test excavations and rework can be reduced, leading to improved construction efficiency.

This article explains the basic technologies and use methods of buried-pipe AR displays at infrastructure sites. It also introduces how construction efficiency can be improved with the latest field cases and expected effects, and finally provides information on a simple surveying solution using LRTK.

The problem of underground utilities being "invisible"

The thing to avoid most in road works and excavation is accidentally damaging existing underground infrastructure such as water pipes and cables. Damaging aged water supply pipes can lead to large-scale leakage accidents; with gas pipes there is a risk of explosion. Cutting a power line can plunge surrounding areas into blackouts or cause communication failures, severely affecting social life. In fact, many underground-utility damage incidents are reported domestically every year, and in many cases the cause is that people did not accurately understand what was buried there.

Therefore, careful management of buried utilities has long been practiced. In new piping work, measurements are taken and the pipe’s position and depth are recorded before backfilling, and information is preserved through photographs and drawings. On site, workers mark the ground based on those drawings, and experienced workers carefully excavate while estimating “there should be such-and-such pipe around here.” As needed, ground-penetrating radar is used to confirm the location of buried objects, or test excavations (physically digging holes to check) are carried out. But relying on paper drawings and workers’ intuition has limits, and especially in urban areas where renovations have been repeated, discrepancies between drawings and actual site conditions are not uncommon. There are frequent cases where unexpected pipes appear from places thought to be clear, causing close calls.

Ultimately, the fundamental problem in infrastructure construction and maintenance management is “how to make invisible things visible.” If the underground piping structure could be intuitively understood on site, not only could excavation troubles be avoided, but inspections of aged pipes and planning of replacements could be greatly streamlined. As a solution, AR technology for visualizing buried utilities is now attracting attention.

Technology to visualize buried pipes with AR

AR (Augmented Reality) overlays digital information such as CG onto real-world images captured by a camera. This makes it possible to display buried pipes and cables in a visible form on site. For example, if you point a smartphone or tablet camera at the ground, the screen can render underground gas pipes or water pipes as if you were looking through the surface, allowing workers to intuitively understand “what is buried directly beneath their feet and how.” There is no longer a need to rely on paper drawings or conjecture; you can check underground structures on site as if you were seeing the real thing.

However, advanced alignment technology is essential to display buried objects at accurate positions in AR. Relying solely on the smartphone’s built-in GPS or compass can produce position errors of several meters on the horizontal plane, causing virtual pipe models to be displayed far off from their actual buried locations. This is far from the level of precision needed for “see-through” visualization and could instead lead to dangerous misidentification. Traditional AR systems also required placing markers (image markers or QR codes) at each site or manually calibrating the model position initially. For wide-area roads and buried-utility management, placing markers or performing manual adjustments at every location is impractical.

This challenge is addressed by markerless high-precision AR using the modern combination of smartphone + LiDAR + RTK-GNSS. Recent smartphones include advanced AR platforms that track device movement in space from camera images and IMU (inertial measurement unit) data. Higher-end models have built-in laser scanners called LiDAR, which can capture the surrounding environment as 3D point-cloud data in real time. Because LiDAR can capture the shape and distance of the ground and structures with high accuracy, virtual objects (for example, a 3D model of an underground pipe) can be stably overlaid on the real world and occlusion effects—where virtual objects are properly hidden behind real ones—can be naturally represented. Smartphones can now instantly construct a 3D map of the surroundings in addition to the camera image, dramatically strengthening the foundation for AR displays.

The last remaining piece is knowing exactly “where the device itself is.” This is where high-precision positioning technology RTK-GNSS (real-time kinematic satellite positioning) becomes powerful. As mentioned, standard smartphone GPS can have meter-scale errors, but the RTK method—applying real-time error corrections from a base station—can reduce that error to a few centimeters. RTK-GNSS has long been used in surveying, and recent miniaturization and weight reduction of receivers have produced ultra-compact RTK-capable GNSS receivers that can be attached to smartphones. For example, a startup developed a device called the “LRTK Phone” that weighs about 165 g and has a thickness of about 13 mm (0.51 in); attaching it to the back of a smartphone enables centimeter-level positioning. It runs for about 6 hours on an internal battery and can be attached to a phone case with a one-touch mechanism, making it very convenient. It also supports the centimeter-level augmentation service (CLAS) provided by Japan’s Quasi-Zenith Satellite System “Michibiki,” allowing the device to maintain centimeter-level accuracy even in mountainous areas outside cellular coverage by using augmentation signals from satellites alone. In urban areas, using RTK correction information via the internet as before can keep real-time positioning errors within a few centimeters anywhere in Japan. With such high-precision GNSS devices combined with smartphones, the era in which “anyone can carry a high-precision positioning tool in their pocket” is becoming a reality.

By combining the terrain point-cloud data obtained from a smartphone’s LiDAR with absolute positioning information from RTK-GNSS, practical-precision “AR see-through of buried pipes” on site has finally become achievable. If a 3D model of the buried pipes (or a mesh generated from point clouds) is preloaded into the smartphone, simply pointing the camera at the site later will display the underground pipe model perfectly overlaid beneath the real ground. Because the ground surface itself is recognized by the device as a mesh model measured with LiDAR, the virtual pipes will be appropriately hidden as if buried (partially visible through the ground surface), and depth relationships can be intuitively understood. This AR see-through technology, which does not require special markers and remains stable even while freely walking around, is turning previously black-box underground infrastructure into “visible information” at the site.

Workflow for using buried-pipe AR displays

• 3D recording of buried pipes (during construction): For example, when burying new piping under a road, scan the pipe and excavation area with a LiDAR-equipped smartphone before backfilling. If an RTK-GNSS receiver is attached to the smartphone, the captured point-cloud data will automatically include high-precision position coordinates (public coordinates) and can be uploaded to the cloud as is. On a dedicated system, a 3D mesh model of the pipe section is automatically generated from the point cloud, producing a digital record of the exact route, depth, and shape of the buried pipe. Traditionally, measuring dimensions and creating drawings after backfilling or marking the temporary restored road surface with spray to indicate pipe routes required extra work, but with this workflow a detailed 3D record is completed simply by scanning.

• Data sharing and management: Point-cloud and model data of buried pipes acquired on site can be shared immediately via the cloud and viewed and used from office PCs or other devices. If incorporated into asset management ledgers or GIS, the data can be accumulated as asset information to assist future inspection planning and coordination with other works. Cloud-based analysis tools can also perform one-click operations such as measuring pipe diameter or burial depth from arbitrary cross-sections in the point cloud, or automatically calculating the volume of soil excavated and backfilled. Site supervisors and construction managers can obtain necessary numerical information instantly without drafting CAD drawings from field notebooks or performing manual calculations. Because site and office can share data in real time, supervisors who are not physically present at the site can still give accurate instructions while viewing point-cloud models, and arrangements such as earth disposal or equipment procurement can be advanced in advance.

• On-site use via AR display (for maintenance and management): The accumulated 3D data of buried pipes can be displayed on site with AR for future inspections and renovation works. Even if the same road is excavated years later for different work, the hassle of digging up old drawings and guessing buried-object locations or performing test excavations is unnecessary. Simply launch the smartphone AR app on site and point the camera, and the locations and routes of pipes under the road surface will be visually displayed. For example, information such as “there is a single water pipe with a diameter of ○○ mm directly beneath here” or “a gas pipe runs parallel on the far side” can be shown as colored virtual pipe models overlaid on the real view, immediately understandable to anyone. Depth information can also be confirmed with labels, allowing vertical relationships such as “this water pipe is buried 1.2 m (3.9 ft) below the surface” to be shared on site. Searching for buried utilities, which once relied on experienced veterans and past records, becomes a visible process anyone can perform based on digital data.

Benefits of improved construction efficiency through buried-pipe AR use

• Preventing excavation accidents: By accurately understanding the buried locations and depths with AR beforehand, the risk of pipe damage caused by erroneous excavations using heavy machinery is greatly reduced. Making invisible hazardous points such as gas pipes and power lines visible before excavation significantly enhances safety measures.

• Efficiency and labor savings: The time spent comparing drawings and estimating positions is eliminated, and excavations and investigations can be carried out only where necessary, shortening work time. Multiple processes such as surveying, stake setting, and pipe recording can be completed with a single smartphone, enabling personnel reductions, shorter construction periods, and cost savings.

• Improved recording accuracy: Digital records from LiDAR scanning can store the position and shape of buried objects to millimeter-level accuracy. These data are far more accurate than paper drawings or oral transmission, providing a highly reliable information base for future asset ledgers. Data accumulated in the cloud is not subject to loss or deterioration.

• Advanced inspection planning: AR brings innovation to renewal plans and regular inspections of aged pipes. By overlaying current 3D data with past repair histories on site, sections that need replacement can be identified and reinforcement measures considered quickly and accurately. For example, in surveys for road sinkhole risk areas, displaying cavities detected by ground-penetrating radar or deterioration data of sewer pipes in AR while marking the site helps comprehensively identify risk locations without omissions. Such data-driven inspection planning greatly improves preventive maintenance efficiency.

• Smooth information sharing and consensus building: Visualized AR information functions as a common language on site. In road construction, multiple stakeholders such as water, gas, and communications providers are involved; if each party’s pipe data are integrated and displayed in AR, everyone can share the same “underground visualization” information during joint site meetings. The need to compare paper drawings is reduced, preventing misunderstandings and communication errors. When explaining to clients or nearby residents, showing “this many pipes run under this road” through a smartphone makes comprehension and consensus-building much smoother.

• Promoting on-site DX: Introducing RTK × AR strongly supports digital transformation (DX) of construction sites. This initiative aligns with the Ministry of Land, Infrastructure, Transport and Tourism’s *i-Construction* efforts, and the use of ICT and 3D data contributes to productivity improvement and advanced safety management. Tasks that previously relied on experience and intuition become data-driven, and “visualization” enables anyone to make accurate decisions and perform work on site. As a result, defects and rework are reduced, contributing to lower life-cycle costs for infrastructure maintenance and management.

Field cases and future developments

The visualization technology for buried pipes using RTK × AR is already being utilized at actual construction sites. Domestically, a startup has developed a system that combines an RTK positioning unit with a tablet to display underground buried pipes in AR on site. Without spreading drawings or conducting test excavations, the positions of buried objects can be grasped three-dimensionally on the spot, contributing to improved safety and work efficiency. Trials at actual construction sites reported that records of buried-pipe work could be completed without photographing or creating CAD drawings, and subsequent re-excavation work quickly located pipes using AR display, demonstrating significant effects. Site workers have given positive feedback such as “searching for buried utilities, which used to rely on intuition, can now be done by anyone” and “the operation is intuitive and could be used without training,” indicating encouraging signs of field adoption.

Looking overseas, outdoor high-precision AR systems are beginning to attract attention as pioneering technology in the construction industry. Systems combining high-performance GNSS receivers and AR can overlay 3D design models onto real-world views through smartphones with centimeter-level precision, enabling intuitive on-site sharing and verification of complex BIM models and underground utility information. Both in Japan and abroad, initiatives for construction DX and smart maintenance using RTK × AR are becoming more active, and adoption is progressing across a wide range of projects from bridge construction to water and sewer maintenance.

Going forward, such high-precision AR technology is likely to become more generalized and simplified, potentially becoming the industry standard. A future in which each worker habitually points a smartphone at the site to check design drawings and underground utility status in AR while working is approaching. Without relying on expensive surveying instruments or special skills, everyone will be able to handle accurate, real-time information based on spatial coordinates, further accelerating a productivity revolution in the construction and infrastructure sectors.

Conclusion: Simple surveying and AR display enabled by LRTK

The visualization of buried pipes using RTK × AR has the potential to greatly transform infrastructure maintenance and civil engineering work sites. By overlaying digital data onto the real world with centimeter-level position accuracy, work that depended on skilled experience is beginning to shift toward data-driven smart construction. One solution attracting attention for easy on-site use of this cutting-edge technology is LRTK.

LRTK is an integrated system that enables anyone to achieve centimeter-level positioning and AR visualization easily via a compact RTK-GNSS receiver that attaches to a smartphone and a dedicated app. Many common AR surveying tools require pre-installed markers or complex initial calibration, but with LRTK RTK can fix within several tens of seconds after powering the device, allowing high-precision AR to start immediately. No special calibration is required, making it exceptionally easy to use on site. Cloud integration also allows seamless operations such as downloading design data or point-cloud survey data for AR display on site, or uploading measured data immediately for sharing. Designed for intuitive use by non-experts, there are reports that a single smartphone per person enabled surveying, stake-out, inspection, photo recording, and AR simulation.

By using LRTK, sites can dramatically improve productivity and safety without expensive equipment or large surveying teams. Beyond buried-pipe see-through displays, it can be applied to a wide range of uses such as verification of as-built shapes of structures and construction navigation, making it a true “all-purpose surveying tool” and a trump card for on-site DX. Surveying companies, municipal civil departments, and construction firms—by adopting this cutting-edge RTK × AR technology at your sites, why not step into a new stage of smart infrastructure management? For product information and case studies, please see the [LRTK official site](https://www.lrtk.lefixea.com/). Take your site to the next stage with LRTK.

FAQ

Q: What is needed to display buried pipes in AR? A: Basically, you need digital data that includes the position information of buried pipes (for example, 3D models or point-cloud data) and an AR-capable device that can display that data on site. Specifically, prepare design drawings or scan data obtained during construction, and use a system that combines a smartphone or tablet with a high-precision GNSS receiver (RTK-capable). This allows virtual pipe models to be accurately overlaid on camera images at the site.

Q: How accurate is buried-pipe AR display? A: When using RTK-GNSS, the display of buried pipes can achieve accuracy on the order of a few centimeters for both horizontal and vertical directions. Conventional GPS-only AR produced meter-scale discrepancies, but high-precision positioning can reduce the offset between virtual models and actual pipe locations to a level barely noticeable to the human eye. Therefore, it is reasonable to consider the pipes shown in AR to be essentially coincident with the real objects.

Q: If AR is available, are drawings and ground markings unnecessary? A: AR allows direct confirmation of buried pipe locations on site, so the effort of comparing paper drawings or spraying the pavement for markings is greatly reduced. There have been cases where introduction of AR eliminated the need for photo documentation and CAD drawing creation for buried-pipe work. However, drawings and the data themselves should still be retained as management records, and AR is a tool to support on-site work. For final construction confirmation, please cross-check digital data and ensure safety.

Q: Can workers who are not familiar with IT use it? A: Yes. Recent AR apps are designed for intuitive operation. With a simple UI that displays buried pipes just by pointing the smartphone camera, special skills are not required. Reports from sites indicate “it was intuitive to use without training,” and as long as workers are familiar with smartphones, even older workers can use it without problems. With basic operational instruction during introduction, many people adopt AR on site without resistance.

Q: Besides buried pipes, what else can be visualized with AR? A: Of course. AR can be applied to many targets beyond underground pipes. For example, you can display a full-size 3D model of a concrete structure on site for construction checks and navigation, or highlight target bolts in AR during equipment maintenance to prevent missed tightening. As long as positional information is digitized, AR can make “things that are difficult to see” visible on site, not limited to underground utilities.