Table of Contents

• Excavation accidents involving buried utilities of concern

• What is the technology for seeing buried pipes with AR

• Centimeter accuracy enabled by RTK-GNSS (cm level accuracy (half-inch accuracy))

• Workflow for AR display of buried pipes

• Benefits of AR display for buried pipes

• Field cases and future outlook

• Conclusion: Simple surveying and AR display enabled by LRTK

• FAQ

Excavation accidents involving buried utilities of concern

The biggest concern at roadworks and residential excavation sites is accidentally damaging existing underground pipes or cables. For example, damaging an old water main can cause a large-scale leak; a gas pipe breach can cause gas leaks or explosions. Cutting power lines or communication cables can cause area-wide blackouts or communications failures, seriously disrupting social life. In fact, many buried-utility damage incidents are reported across the country almost every year, and in many cases the root cause is not having an accurate understanding of “what is buried there.”

To prevent such accidents, careful maintenance and management of buried pipes has long been practiced. In piping work, positions and depths are surveyed and recorded before backfilling, and photos and drawings are kept. On site, experienced workers rely on those drawings and ground markings and proceed with excavation cautiously, using intuition like “there should be a pipe around here.” As needed, ground-penetrating radar surveys may be used to search for buried objects, or trial excavations (small test holes) are dug to confirm them directly.

However, conventional management methods that rely on paper drawings and experience have limits. Accurately visualizing the complex positional relationships of intersecting underground utilities in one’s head is not easy. Especially in urban areas that have undergone repeated renovations, it is common for the drawings to differ from reality, and there are repeated close calls where unexpected pipes appear in places believed to be clear.

Ultimately, the fundamental challenge in infrastructure management is “how to make the invisible visible.” If subsurface structures could be understood intuitively, not only could excavation troubles be avoided, but inspection and replacement planning for aging pipes would also become far more efficient. What is drawing attention is the visualization of buried pipes using AR (augmented reality) technology.

What is the technology for seeing buried pipes with AR

AR (Augmented Reality) overlays digital information onto real-world images seen through a camera. Using this, pipes and cables buried underground can be virtually displayed in a visible form on site. For example, when a worker points a smartphone or tablet camera at the ground, the screen can depict underground gas lines or water mains as if the surface were transparent, allowing the worker to intuitively grasp “what is buried directly beneath these feet and how.” This lets them confirm subsurface structures on site as if seeing the actual objects, without relying on drawings or guesswork.

However, accurate AR visualization of buried utilities requires advanced alignment technology. If you rely on a smartphone’s built-in GPS or electronic compass, horizontal position errors of several meters can occur, causing the virtual pipe models to appear significantly shifted from the actual buried positions. That level of error is far from what can be called true “see-through” accuracy and could even create danger through misidentification. Conventional outdoor AR systems often required placing markers (alignment targets) at each site or manually adjusting model positions (calibration) initially. For extensive roads and utility networks, placing markers at every location or manually aligning each time is not practical.

To solve these problems, a recent solution is “markerless high-precision AR” that combines a smartphone + LiDAR + RTK-GNSS. Modern smartphones include advanced AR platforms that track device motion within space using camera images and IMU (inertial measurement unit) data. Higher-end models even include small LiDAR (light-based ranging sensors) that can capture the surrounding environment as real-time 3D point clouds. LiDAR enables high-precision sensing of ground and structure shape and distance, allowing virtual objects (for example, 3D models of underground pipes) to be stably overlaid on the real world and enabling natural occlusion effects where virtual objects are hidden behind real ones. In other words, in addition to camera images, smartphones can instantly build a 3D map of their surroundings, greatly strengthening the foundation for AR display.

The last remaining piece is for the device itself to know “exactly where it is.” This is where the high-precision positioning technology RTK-GNSS (Real-Time Kinematic satellite positioning) shines. As mentioned, standalone smartphone GPS can have meter-level errors, but by using RTK correction data the position error can be reduced to a few centimeters. RTK positioning has long been used in surveying, and recently receivers have become smaller and lighter; RTK-capable GNSS receivers that can be attached to smartphones have appeared. Combining such high-precision GNSS with a smartphone makes it possible to capture the device’s position in a public coordinate system with centimeter-level accuracy (cm level accuracy (half-inch accuracy)), minimizing the misalignment between virtual models and the real world.

By combining the ground-shape point cloud data captured by a smartphone’s LiDAR with the global position information from RTK-GNSS, “AR see-through” of buried pipes becomes practically feasible. For example, if you preload a 3D model of buried pipes (mesh data created from point clouds) into the smartphone, visiting the site later and pointing the camera at the ground will display the underground model precisely overlaid at that exact spot. Because the ground itself is recognized by the smartphone as a mesh model from LiDAR measurements, the virtual pipes appear correctly buried—occluded by the ground—and depth relationships are intuitively understood. This marker-free AR see-through technology, which does not drift even when freely walking around, is transforming previously black-box underground infrastructure into visible on-site information.

Centimeter accuracy enabled by RTK-GNSS (cm level accuracy (half-inch accuracy))

RTK (Real-Time Kinematic) is a method that uses correction information from a reference station in real time to improve GNSS positioning accuracy. By relative positioning with a fixed reference point, it can reduce typical meter-level errors to within a few centimeters. Because centimeter-level accuracy can be obtained in both horizontal and vertical dimensions, RTK has long been used in civil engineering surveying.

What has made RTK positioning easily usable by everyone on site is the recent appearance of ultra-compact RTK-GNSS receivers. For example, a startup originating from Tokyo Institute of Technology developed a device called the “LRTK Phone,” a small receiver weighing about 165 g and about 13 mm (0.51 in) thick that can be attached to the back of a smartphone to enable RTK positioning. It runs on a built-in battery for about 6 hours and can be attached with a one-touch operation like a smartphone case. It also supports the centimeter-class positioning augmentation service (CLAS) provided by Japan’s Quasi-Zenith Satellite System (QZSS), allowing stable centimeter-level accuracy (cm level accuracy (half-inch accuracy)) in mountainous areas where mobile signals do not reach, relying solely on satellite augmentation signals. In urban areas, conventional network-based RTK correction services can be used so that positioning errors can be corrected to within a few centimeters in real time anywhere in Japan. In other words, by integrating such high-precision GNSS devices with smartphones, the era in which “anyone can carry a high-precision positioning tool in their pocket” is becoming a reality.

Envision a future in which each field technician carries a smartphone with a high-precision GPS device, quickly takes it out when needed, and uses it for surveying and AR display—this future is already beginning to appear. In fact, the latest systems display positioning results and navigation information on the smartphone screen with intuitive Japanese UIs, so they are easy to use without specialized knowledge. For example, tasks that used to require two people for stake-out can now be done by one person holding a lightweight pole with an RTK receiver attached to a smartphone and following on-screen guidance to position stakes accurately. Easy-to-use high-precision GNSS positioning will dramatically improve the productivity and accuracy of surveying and construction management work.

Workflow for AR display of buried pipes

Combining centimeter-level RTK positioning with smartphone AR enables end-to-end digitization from construction records to maintenance. Below is the workflow for realizing AR visualization of buried pipes, from 3D recording to on-site use.

1. 3D recording of buried pipes (during construction): For example, when installing new pipes under a road, scan the pipe and the surrounding excavation area with a LiDAR-equipped smartphone before backfilling. If an RTK-GNSS receiver is attached to the smartphone, the acquired point cloud data will automatically include high-precision absolute coordinates (in a global geodetic system) and the data will be saved to the cloud. The system automatically generates a 3D mesh model of the pipe portion from the point cloud, digitally recording the exact position (route and depth) and shape of the buried pipe. Traditionally, after backfilling you would survey and create drawings or mark the pipe route on temporarily restored pavement with spray paint, but with this workflow a detailed 3D record is completed simply by scanning.

2. Data sharing and management: Point cloud and model data of buried pipes obtained on site can be shared immediately via the cloud and viewed or used from office PCs or other devices. If incorporated into maintenance ledgers or GIS as asset information, they help with future inspection planning and coordination with other works. The cloud also enables advanced processing such as analyzing point clouds to measure diameters and burial depth on arbitrary cross-sections or automatically calculating excavation/backfill volumes with one click. This allows site supervisors and construction managers to obtain necessary numerical information instantly without having to create CAD drawings or perform manual calculations. Because data can be shared in real time between the site and the office, office staff can give instructions while reviewing the point cloud model remotely, or prearrange disposal of excavated soil and materials without being on site.

3. On-site use through AR visualization (for maintenance): Accumulated 3D data of buried pipes can be displayed on-site with AR for inspections or repair work. For example, when the same road is dug up again years later, the old process involved digging out drawings and making trial excavations to confirm burial positions. With 3D record data, launching an AR app on a smartphone and pointing the camera at the ground instantly displays the positions and routes of pipes buried beneath the road surface. Information such as “a water pipe of diameter ○○ mm runs directly below here” or “a gas pipe runs parallel further in” is shown as colored virtual pipe models overlaid on the real scene, making it immediately clear. Depth information can also be labeled, so you can share vertical position relationships on site, such as “this water pipe is buried 1.2 m (3.9 ft) below the surface.” The task of finding buried utilities, which used to rely on veteran intuition and documents, becomes a visible digital task that anyone can perform.

This whole process digitally integrates the cycle of surveying, recording, data sharing, and on-site confirmation via AR. Because it preserves detailed 3D information that paper drawings and photo ledgers could not reproduce, the information does not degrade over time and can always be managed with high-precision spatial coordinates. As a result, maintenance accuracy for buried infrastructure improves, contributing to future accident prevention and more efficient planning.

Benefits of AR display for buried pipes

Using the RTK×AR technology described above brings various benefits to infrastructure inspection and civil engineering sites. The main effects are summarized below.

• Prevention of underground utility accidents: By accurately determining burial positions and depths with AR before excavation, the risk of damaging pipes with heavy machinery due to erroneous digging is greatly reduced. Visualizing invisible hazards such as gas pipes and electrical lines in advance significantly strengthens safety measures.

• Work efficiency and labor savings: The need to compare drawings with the site and guess positions is eliminated, so excavation and investigations can be limited to where they are needed, shortening work time. Multiple processes such as surveying, staking, and pipe recording can be completed with a single smartphone, enabling staff reduction, shorter schedules, and cost savings.

• Improved recording accuracy: Digital records from point cloud scans can preserve the position and shape of buried objects to the millimeter. This produces much more accurate data than relying on paper drawings or oral handoffs, creating a reliable information base for future maintenance ledgers. Because data is stored in the cloud, there is no worry about loss or degradation.

• Advanced maintenance and inspection planning: AR enables innovation in planning for replacement of aging pipes and periodic inspections. By overlaying current 3D data with past repair histories on site, sections requiring replacement or reinforcement measures can be identified and assessed quickly and accurately. For example, in investigating road subsidence risk areas, AR display of void locations found by ground-penetrating radar and deterioration data for sewer pipes, combined with on-site marking, ensures no risk areas are overlooked. Data-driven inspection planning like this dramatically improves preventive maintenance efficiency.

• Improved information sharing and communication: AR visualizations serve as a common language on site. For example, roadworks often involve multiple utility operators such as water, gas, and communications; if each party’s pipe data is integrated and displayed with AR, everyone can share the same view of the underground conditions during joint on-site meetings. This reduces the need to compare paper drawings and prevents misunderstandings or communication errors. It also makes explanations to clients and nearby residents smoother, as you can intuitively show via smartphone what pipes run under the road.

• Promotion of on-site DX: The introduction of RTK×AR strongly accelerates digital transformation (DX) on construction sites. It aligns with initiatives such as the Ministry of Land, Infrastructure, Transport and Tourism’s *i-Construction*, and by utilizing ICT and 3D data it contributes to productivity improvements and advanced safety management. Work that used to rely on experience and intuition becomes data-driven, enabling everyone to make accurate judgments and perform tasks reliably through visualization. This reduces defects and rework, and is expected to contribute to lowering life-cycle costs associated with infrastructure maintenance.

Field cases and future outlook

This RTK×AR buried-pipe visualization technology is already being used in actual field settings. In Japan, one startup combined an RTK positioning unit with a tablet to develop a system that displays buried pipes on site with AR. Without unfolding drawings or doing trial excavations, users can grasp the positions of buried objects three-dimensionally on the spot, contributing to improved safety and work efficiency. Trials at actual construction sites reported major benefits such as completing records of buried-pipe work without photography or CAD drawing creation, and quickly locating pipes later during re-excavation using AR. Workers have also reported favorable feedback like “Searching for buried utilities, which used to rely on intuition, can now be done by anyone” and “Operation was so intuitive we could use it without training,” indicating good traction for on-site adoption.

Looking abroad, outdoor high-precision AR systems are attracting attention as world-first technologies in the construction industry. Systems combining high-performance GNSS receivers and AR can overlay 3D design models on real scenes through a smartphone with centimeter accuracy, enabling intuitive on-site sharing and verification of complex BIM models and underground utility information. Both in Japan and overseas, RTK×AR initiatives for construction DX and smart maintenance are gaining momentum, and adoption is expanding across a wide range of projects from bridge construction to water and sewer maintenance.

Going forward, it is highly likely that high-precision AR technology will become more generalized and simplified, becoming a new industry norm. A future where every worker casually points a smartphone at the site to confirm design drawings and underground utility conditions via AR is approaching. When anyone can handle accurate, real-time spatial information without expensive equipment or special skills, a productivity revolution in construction and infrastructure sectors is expected to accelerate further.

Conclusion: Simple surveying and AR display enabled by LRTK

Visualization of buried pipes using RTK×AR holds great potential to transform infrastructure maintenance and civil engineering sites. By overlaying digital data onto the real world with centimeter-level positioning accuracy (cm level accuracy (half-inch accuracy)), work that once relied on skilled experience is beginning to shift to data-driven smart construction. One solution gaining attention for easy on-site use of this advanced technology is LRTK.

LRTK is an integrated system that enables anyone to achieve centimeter-level positioning and AR visualization easily through a small RTK-GNSS receiver that attaches to a smartphone and a dedicated app. Many common AR surveying tools require pre-placed markers or complex initial calibration, but with LRTK you can power on the device, RTK gets a fix within tens of seconds, and you can start high-precision AR right away. No special calibration work is required—its immediate usability on site is a major feature. 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 for instant sharing. The system is designed to be intuitive for non-expert workers, and there are reports that one smartphone per person handled surveying, staking, inspection, photo records, and AR simulation.

Using LRTK makes it possible to dramatically improve on-site productivity and safety without expensive equipment or large teams. It applies not only to see-through display of buried pipes but also to as-built verification of structures and construction navigation, serving as a versatile surveying tool and a trump card for on-site DX. Surveying firms, municipal civil departments, and construction companies can adopt this cutting-edge RTK×AR technology in their operations to step into a new stage of smart infrastructure inspection. For product information and case studies, please see the [LRTK official site](https://www.lrtk.lefixea.com/). Let LRTK take your sites to the next stage.

FAQ

Q: What is AR display of buried pipes? A: It is the use of AR (augmented reality) technology to make the positions of pipes and cables buried underground visible through a camera. When you point a smartphone at the ground, a virtual pipe model is overlaid on the real image, allowing you to check the underground piping as if you were looking through the ground.

Q: Why is high-precision positioning required to display buried pipes with AR? A: To accurately align a virtual model with the actual buried position, the smartphone’s position and orientation must be known to centimeter accuracy. Ordinary GPS has meter-level errors, which would cause the AR pipe display to shift and fail to provide true “see-through” accuracy. By using high-precision RTK-GNSS positioning, the smartphone’s position can be determined within a few centimeters, allowing virtual pipes to be matched precisely to their real locations.

Q: How is the location data for buried pipes obtained? A: AR display requires prior acquisition of 3D data of pipe positions. For new pipes, record their 3D positions before backfilling using a smartphone LiDAR scan combined with RTK positioning. For existing buried pipes, you can create 3D models by overlaying past drawing information with current coordinates obtained via RTK, or by importing point cloud data from ground-penetrating radar surveys for AR display.

Q: Can you see through buried pipes with just a smartphone? A: Yes. By combining a modern smartphone’s camera, IMU, and LiDAR-based AR functions with an external small RTK-GNSS receiver, you can obtain centimeter-accurate position information and accurately display buried pipes on the smartphone screen without special goggles or large equipment.

Q: What is LRTK? A: LRTK is a solution that enables anyone to easily perform high-precision positioning and AR visualization of buried pipes using a smartphone. It consists of a lightweight RTK-GNSS module that attaches to a phone and a dedicated app, allowing immediate display of 3D buried-pipe data and surveying without complicated setup or special markers. For details, see the [LRTK official site](https://www.lrtk.lefixea.com/).