AR revolution at infrastructure sites! Improve construction efficiency with AR visualization of buried pipes

Table of Contents

• The problem of buried underground utilities being “invisible”

• Technology to visualize buried pipes with AR

• Workflow for using AR to display buried pipes

• Benefits of improved construction efficiency through AR use for buried pipes

• Field cases and future developments

• Conclusion: Easy surveying and AR display enabled by LRTK

• FAQ

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

Recently, however, AR (augmented reality) has attracted attention as a technology to “make the invisible visible.” In particular, “buried pipe AR display” combined with high-precision positioning technology RTK-GNSS makes it possible to visualize underground pipelines on site as if looking through the ground. If workers can intuitively grasp the state of buried pipes on site, safety measures will dramatically improve, and unnecessary trial excavations and rework can be reduced, leading to improved construction efficiency.

This article explains the basic technologies and practical uses of buried pipe AR display at infrastructure sites. It also introduces how construction efficiency can be increased with the latest field cases and expected effects, and finally presents an easy surveying solution using LRTK.

The problem of buried underground utilities being “invisible”

What must be avoided most in roadworks and excavation is accidentally damaging existing underground infrastructure such as water pipes and cables. Damaging aging water mains can lead to large-scale leaks, gas pipes carry the risk of explosions, and cutting power lines can plunge surrounding areas into blackouts and communications outages, causing major impacts on social life. Indeed, many incidents of damage to buried utilities are reported domestically each year, and in many cases the cause is that those involved did not accurately know what was buried there.

Therefore, great care has traditionally been taken in managing buried pipes. In new piping work, measurements are taken before backfilling to record the pipe’s position and depth, and photos and drawings are kept for records. On site, the ground is marked based on those drawings, and experienced workers carefully excavate while guessing “the XX pipe should be around here.” As needed, ground-penetrating radar is used to confirm the positions of buried objects, or test excavations (actually digging holes to directly confirm) are carried out. However, methods that rely on paper drawings and craftsmen’s intuition have limits, and in urban areas with repeated renovations it is not uncommon for the information on drawings and the reality on site to differ. There are frequent incidents where an unexpected pipe appears from a place thought to be clear, causing a close call.

Ultimately, the fundamental problem in infrastructure construction and maintenance 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 inspection and replacement planning for aging pipes could also be dramatically improved. AR technology for visualizing buried pipes is now expected as a solution.

Technology to visualize buried pipes with AR

AR (augmented reality) is a technology that overlays digital information such as CG onto real-world images captured by a camera. This makes it possible to display pipes and cables buried underground in a visible form on site. For example, if you point a smartphone or tablet camera at the ground, underground gas or water pipes can be rendered on the screen as if you were seeing through the ground, allowing workers to intuitively understand “what is buried directly beneath this spot and how.” No longer relying on paper drawings or guesses, you can confirm underground structures on site as if viewing the actual objects.

However, accurate alignment technology is indispensable to display buried objects in AR at the correct positions. Relying solely on a smartphone’s built-in GPS or compass can produce planar position errors of several meters (several ft), causing virtual pipe models to be displayed far from the actual buried locations. This is far from the accuracy needed for true “see-through” visualization and could even lead to dangerous misidentification. Conventional AR systems also required placing markers (image markers, QR codes, etc.) at each site or manually calibrating model positions at the start. For managing roads and buried pipes across wide areas, placing markers or performing manual adjustments at each location is impractical.

The solution to these issues is “markerless high-precision AR” achieved by combining a smartphone + LiDAR + RTK-GNSS. Modern smartphones have advanced AR platforms that track device motion in space using camera images and IMU (inertial measurement unit) data. Higher-end models also include LiDAR, a laser scanner that can acquire the surrounding environment as real-time 3D point cloud data. Because LiDAR can capture the shape and distance of the ground and structures with high precision, virtual objects (for example, 3D models of underground pipes) can be stably overlaid onto the real world, and occlusion effects where objects are hidden behind others can be naturally represented. The smartphone itself can instantly construct a three-dimensional map of the surroundings in addition to the camera image, greatly strengthening the foundation for AR displays.

The final piece is to know exactly “where the device itself is.” High-precision positioning technology RTK-GNSS (real-time kinematic satellite positioning) plays a key role here. As mentioned, a normal smartphone GPS can have meter-level errors, but using RTK (applying base-station error corrections in real time) can reduce that error to a few centimeters. RTK-GNSS has long been used in surveying, and recent miniaturization of receivers has 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 approximately 165 g and is about 13 mm (0.51 in) thick; attaching it to the back of a smartphone enables centimeter-level positioning. It runs on an internal battery for about 6 hours and can be attached to a phone case with a single touch for ease of use. It also supports the quasi-zenith satellite system “Michibiki” in Japan’s centimeter-level augmentation service (CLAS) (cm level accuracy (half-inch accuracy)), so in mountainous areas outside communication coverage, it can maintain centimeter accuracy using augmentation signals from satellites alone. In urban areas, using RTK correction data via the Internet as before allows positioning errors to be kept within a few centimeters across Japan in real time. The combination of such high-precision GNSS devices and smartphones is making the era of “everyone carrying a high-precision positioning tool in their pocket” a reality.

By combining terrain point-cloud data acquired by a smartphone’s LiDAR with absolute position information from RTK-GNSS, on-site “AR see-through of buried pipes” has finally become practical with sufficient accuracy. If a 3D model of buried pipes (or a mesh generated from point clouds) is preloaded on the smartphone, simply pointing the camera at the site on a later visit will display the underground pipe model perfectly aligned under the real ground. Since the device recognizes the ground itself as a mesh model measured by LiDAR, the virtual pipe will be appropriately hidden as if buried (partially visible from the surface), and the vertical position relationship can also be intuitively understood. This AR see-through technology that does not drift even when freely walking around without special markers is turning previously black-box underground infrastructure into “visible information” on site.

Workflow for using AR to display buried pipes

• 3D recording of buried pipes (during construction): For example, when newly installing pipes under a road, scan the pipes and excavation area with a smartphone (equipped with LiDAR) before backfilling. If an RTK-GNSS receiver is attached to the smartphone, high-precision position coordinates (public coordinates) are automatically assigned to the acquired point cloud data and can be uploaded to the cloud as is. A dedicated system automatically generates 3D mesh models of the pipe sections from the point cloud, digitally recording the exact route, depth, and shape of the buried pipes. Previously, work such as measuring dimensions after burial to create drawings or spraying pipe routes on temporarily restored road surfaces was required, but with this workflow, simply scanning completes detailed 3D records.

• 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 and used for future inspection planning or coordination with other works. Cloud-based analysis tools can also perform tasks such as measuring pipe diameters and burial depths from arbitrary cross-sections of point cloud data, or automatically calculating the volume of excavated/backfilled soil, with a single click. Site supervisors and construction managers can instantly obtain required numeric information without drafting CAD drawings or doing manual calculations based on field notes. Because data can be shared between the field and the office in real time, supervisors not present on site can still give accurate instructions while viewing the point cloud model, and arrangements such as advance scheduling for spoil disposal or equipment can be made earlier.

• On-site use via AR display (during maintenance): The accumulated 3D data of buried pipes can be used on-site with AR for future inspections or repair works. Even years later when the same road is excavated for another project, the hassle of pulling out old drawings and guessing the buried objects’ positions and confirming them with trial excavations is unnecessary. Just launch an AR app on a smartphone and point the camera to visually display the positions and routes of pipes buried under the road surface on site. For example, information such as “a single water pipe with a diameter of ○○ mm is located directly beneath here” or “a gas pipe runs parallel further back” can be shown as colored virtual pipe models overlaid on the real view, making it obvious to anyone. Depth information can also be shown as labels, enabling on-site sharing of vertical position relationships such as “this water pipe is buried 1.2 m (3.9 ft) below the surface.” Searching for buried objects, which used to rely on experienced veterans and past records, is transformed into a visible process anyone can perform using digital data.

Benefits of improved construction efficiency through AR use for buried pipes

• Preventing excavation accidents: By accurately grasping buried positions and depths in advance with AR, the risk of pipe damage due to mistaken excavations by heavy machinery is greatly reduced. Visualizing hidden hazards such as gas pipes and power lines before excavation significantly enhances safety measures.

• Improved efficiency and labor savings: Time spent comparing drawings with site conditions and estimating positions is eliminated, allowing excavation and investigation to be performed only where necessary, which shortens work time. Multiple processes such as surveying, stake setting, and recording pipe locations can be completed with a single smartphone, enabling reductions in personnel, construction period, and costs.

• Improved record accuracy: Digital records using LiDAR scans can save the locations and shapes of buried objects to millimeter-level precision. This yields far more accurate data than relying on paper drawings or oral transmission, providing a highly reliable information base for future asset ledgers. Data stored in the cloud eliminates concerns about loss or deterioration.

• Advanced inspection planning: AR enables innovation in planning updates and regular inspections of aging pipes. By overlaying current 3D data with past repair histories on site, you can quickly and accurately identify sections that need replacement or consider reinforcement measures. For example, when investigating areas at risk of road collapse, showing cavity locations found by ground-penetrating radar and degradation data of sewer pipes in AR while marking the site ensures no risk areas are overlooked. Such data-driven inspection planning dramatically improves preventive maintenance efficiency.

• Smoother information sharing and consensus building: AR-visualized information serves as a common language on site. For example, roadworks involve multiple operators such as water, gas, and telecommunications providers; by integrating each party’s pipe data and displaying them together in AR, all participants can share the same “underground visualization” information during joint on-site meetings. This reduces the need to compare paper drawings and prevents misunderstandings or miscommunication-related troubles. When explaining to clients or nearby residents, AR allows intuitive demonstrations such as “this road has this many pipes underneath,” facilitating smoother understanding and consensus.

• Promoting on-site DX: Introducing RTK×AR strongly supports digital transformation (DX) at construction sites. This initiative aligns with the Ministry of Land, Infrastructure, Transport and Tourism’s i-Construction and, through the use of ICT and 3D data, contributes to productivity improvements and enhanced safety management. Procedures that relied on experience and intuition are shifting to data-driven operations, and “visualization” enables anyone to make accurate judgments and perform tasks on site. As a result, defects and rework are reduced, which is expected to contribute to lowering life-cycle costs for infrastructure maintenance.

Field cases and future developments

The RTK×AR technology for visualizing buried pipes is already being used in actual construction sites. In Japan, a startup combined an RTK positioning unit with a tablet to develop a system that displays underground buried pipes on site in AR. Without spreading out drawings or performing test excavations, workers can spatially grasp the positions of buried objects on the spot, contributing to greater safety and work efficiency. In trials at actual sites, records of buried pipe work were completed without photo documentation or CAD drawing creation, and later re-excavation work immediately identified pipe locations via AR display, producing significant effects. Workers at the sites reported positive feedback such as “searching for buried objects that used to rely on intuition is now something anyone can do” and “the operation is intuitive enough to use without training,” indicating promising adoption on the ground.

Looking abroad, outdoor high-precision AR systems are beginning to attract attention as world-first technologies in the construction industry. Systems combining high-performance GNSS receivers and AR allow 3D design models and real-world views to be overlaid with centimeter accuracy through a smartphone, enabling on-site sharing and verification of complex BIM models and underground utility information. Both in Japan and overseas, efforts to implement construction DX and smart maintenance using RTK×AR are accelerating, and adoption is expanding across a wide range of projects from bridge construction to water and sewer maintenance.

Going forward, this high-precision AR technology is likely to become more generalized and simplified, potentially becoming the new industry standard. The future in which workers routinely point their smartphones on site to check designs and underground utilities in AR is approaching. Without relying on expensive surveying equipment or special skills, everyone will be able to handle accurate information based on spatial coordinates in real time, further promoting a productivity revolution in the construction and infrastructure fields.

Conclusion: Easy surveying and AR display enabled by LRTK

The visualization of buried pipes using RTK×AR has the potential to drastically transform infrastructure maintenance and civil engineering sites. Overlaying digital data onto real space with centimeter-level positioning enables work that once depended on skilled experience to shift to smart, data-driven construction. Among the solutions attracting attention for easily applying this advanced technology on site is LRTK.

LRTK is an integrated system that enables anyone to achieve centimeter-accurate positioning and AR visualization by attaching a small RTK-GNSS receiver to a smartphone and using a dedicated app. While many conventional AR surveying tools require pre-placed markers and complicated initial calibrations, LRTK can obtain an RTK fix within tens of seconds after powering on the device, allowing immediate start of high-precision AR. No special calibration work is required, making it extremely 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, and instantly uploading and sharing measured data collected in the field. The system is designed for intuitive use by non-experts, and there are reports that one smartphone per person enabled surveying, stake-out, inspection, photo documentation, and AR simulation.

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

FAQ

Q: What is required to display buried pipes in AR? A: Basically, you need digital data that includes the positions of buried pipes (e.g., 3D models or point cloud data) and an AR-capable device to display the data on site. Specifically, you prepare design drawings or scan data acquired during construction, and use a system that combines a smartphone or tablet with a high-precision GNSS receiver (RTK-capable). This allows you to accurately overlay virtual pipe models onto the camera view on site.

Q: How accurate is AR display of buried pipes? A: Using RTK-GNSS, buried pipes can be displayed with planar and vertical errors on the order of a few centimeters (a few in). Conventional GPS-only AR had meter-level errors, but high-precision positioning can reduce the discrepancy between virtual models and actual pipe locations to a level that is almost imperceptible to the human eye. Therefore, you can consider AR-displayed pipe positions to be practically consistent with the real objects.

Q: Will AR make drawings and ground markings unnecessary? A: AR allows direct on-site confirmation of buried pipe positions, greatly reducing the need to compare paper drawings or spray-mark routes on the pavement. In practice, introduced AR has enabled omission of photo records and CAD drawing creation for buried pipe works in some cases. However, drawings and the underlying data must still be retained as management records, and AR should be treated as a tool that supports on-site work. For final construction verification, always cross-check with 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 when you point the smartphone camera, special skills are not required. Sites report that “it was intuitive enough to use without training,” and older workers who are accustomed to smartphones can use it without issue. With basic operational guidance at introduction, many people quickly 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, full-size 3D models of concrete structures can be displayed on site for construction checks and navigation, or bolts to be tightened can be highlighted in AR for equipment maintenance to prevent omissions. In short, as long as positional information is digitized, AR can make “hard-to-see things” visible on site, not limited to underground utilities.