Toward Zero Excavation Accidents! Achieving Safe Construction with AR Display of Buried Pipes

Table of Contents

• Excavation-site concerns about buried-pipe accidents

• What is the technology for seeing through the ground with AR?

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

• Workflow for AR display of buried pipes

• Benefits of AR display for buried pipes

• Field cases and future prospects

• Conclusion: Simple surveying and AR display realized by LRTK

• FAQ

Excavation-site concerns about buried-pipe accidents

The greatest concern at roadworks and residential excavation sites is accidentally damaging existing underground pipes or cables. For example, damaging an old water main can lead to a major leak, and a gas pipe could cause gas leaks or explosions. Cutting power lines or communication cables can cause local blackouts or communication outages, seriously disrupting social activities. In fact, many damage incidents to buried utilities are reported nationwide almost every year, and a large proportion of them are caused by not knowing exactly “what is buried there.”

To prevent such accidents, the maintenance and management of buried pipes have long been handled with the utmost care. In piping work, locations and depths are surveyed and recorded before backfilling, and photos or drawings are kept. On-site, workers rely on those drawings and ground markings, and experienced operators proceed with cautious excavation guided by intuition such as “there should be a pipe around here.” As needed, subsurface radar surveys may be used to search for buried objects, or trial excavations (digging small holes to check directly) may be conducted.

However, the conventional management methods that rely on paper drawings and experience have their limits. It’s not easy to mentally keep track of the exact positional relationships of complex, intersecting underground utilities. Especially in urban areas that have undergone repeated renovations, site reality often diverges from the drawings, and unexpected pipes can appear where “there shouldn’t be any,” causing many close-call incidents.

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

What is the technology for seeing through the ground with AR?

AR (Augmented Reality) overlays digital information onto real-world images captured through a camera. By using this technology, buried pipes and cables can be virtually displayed on site in a visible form. For example, by pointing a smartphone or tablet camera at the ground, underground gas mains or water pipes can be rendered on the screen as if the surface were transparent, allowing workers to intuitively understand “what is buried directly beneath their feet” without relying on drawings or conjecture.

However, accurately seeing through the ground with AR requires advanced alignment technology. If one relies on a smartphone’s built-in GPS or electronic compass, horizontal positioning errors of several meters can occur, causing virtual pipe models to be displayed significantly offset from their actual buried positions. This is far from the accuracy required for “seeing through” and could even create danger through misidentification. Traditional outdoor AR systems also typically require placing markers (registration marks) at each site or manually calibrating model positions at the start. For managing extensive roads and buried utilities, placing markers at each location or manually aligning every time is impractical.

To solve these problems, a recent approach combines smartphone + LiDAR + RTK-GNSS to realize “markerless high-precision AR.” Modern smartphones include advanced AR platforms that use camera images and IMU (inertial measurement unit) data to track device movement and position in space. Higher-end models incorporate compact LiDAR (light-based distance sensors) that can acquire the surrounding environment as real-time 3D point clouds. Because LiDAR can accurately capture the shape and distance of the ground and structures, virtual objects (such as 3D models of underground pipes) can be stably overlaid on the real world, and occlusion effects—where virtual objects are naturally hidden behind real objects—can be rendered realistically. In other words, smartphones can now instantly build a 3D map of their surroundings in addition to camera imagery, dramatically strengthening the foundation for AR display.

The final piece is for the device itself to know “where it is” precisely. This is where high-precision positioning technology RTK-GNSS (Real-Time Kinematic satellite positioning) shines. Standalone smartphone GPS can suffer the aforementioned meter-level errors, but using RTK correction data can reduce positioning error to within a few centimeters. RTK positioning has long been used in surveying, and recent miniaturization and lightening of receivers have produced RTK-capable GNSS receivers that can be attached to smartphones. Combining such high-precision GNSS with a smartphone allows the device’s position to be determined in a public coordinate system with centimeter-level accuracy (half-inch accuracy), minimizing the discrepancy between virtual models and the real world.

By combining the ground-shape point-cloud data obtained by a smartphone’s LiDAR with the global self-positioning information from RTK-GNSS, “AR visualization of buried pipes” at the site becomes practically achievable with useful accuracy. For example, if a 3D model of buried pipes (such as a mesh generated from point clouds) has been acquired in advance and loaded onto the smartphone, then later visiting the site and pointing the camera will display the underground model precisely overlapped with the real position beneath the ground. Because the ground itself is recognized by the smartphone as a mesh model from LiDAR measurement, the virtual pipe will be properly occluded as if buried in the soil, allowing intuitive understanding of depth relationships. This marker-free AR visualization, which does not shift even when moving freely around the site, is turning previously opaque underground infrastructure into visible on-site information.

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

RTK (Real-Time Kinematic) is a method that improves GNSS positioning accuracy by using real-time correction information from a reference station. Through relative positioning with a fixed reference point, positioning errors that are usually several meters can be reduced to within a few centimeters. Because it provides centimeter-level accuracy both horizontally and vertically, RTK has long been used in civil engineering surveying.

What has made RTK positioning easily available on-site for anyone is the recent emergence of ultra-compact RTK-GNSS receivers. For example, a startup originating from Tokyo Institute of Technology developed a device called the “LRTK Phone,” which enables RTK positioning simply by attaching a small receiver of about 165 g and 13 mm (0.51 in) thickness to the back of a smartphone. It runs on an internal battery for about 6 hours and can be attached with a one-touch operation like a phone case. It also supports the centimeter-class positioning augmentation service (CLAS) provided by Japan’s quasi-zenith satellite system “Michibiki,” allowing centimeter stability to be maintained in mountainous areas where cellular signals do not reach using only satellite augmentation signals. In urban areas, traditional network-based RTK correction services can be used, enabling real-time correction of positioning errors to within a few centimeters 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.

A future is already visible 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. In current systems, intuitive Japanese UIs display positioning results and navigation on the smartphone screen, so they are designed to be usable without specialized knowledge. For example, layout marking work that previously required a two-person team can now be done by one person holding a lightweight pole with an RTK receiver attached to the smartphone and following on-screen guidance to set out accurate positions. The availability of easy-to-use high-precision GNSS positioning dramatically improves the productivity and accuracy of surveying and construction management work.

Workflow for AR display of buried pipes

The combination of centimeter-level positioning via RTK and smartphone AR enables end-to-end digitization from construction records to maintenance management of buried pipes. Below is the workflow showing how AR visualization of buried pipes is realized, from 3D recording to on-site utilization.

1. 3D recording of buried pipes (during construction): For example, when installing new pipes under a road, scan the pipes and the surrounding excavation area with a smartphone (equipped with LiDAR) before backfilling. If an RTK-GNSS receiver is attached to the smartphone, the acquired point-cloud data are automatically tagged with high-precision absolute coordinates (a global geodetic system), and the data are saved to the cloud as-is. The system automatically generates 3D mesh models of the pipe sections from the point cloud, creating digital records of the exact positions (routes and depths) and shapes of the buried pipes. Traditionally, after backfilling one would survey and draft drawings or mark pipe routes on temporarily restored road surfaces 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 obtained on-site can be shared immediately via the cloud and accessed from office PCs or other devices. If stored in maintenance ledgers or GIS as asset information, the data will help future inspection planning and coordination with other works. On the cloud, point-cloud data can be analyzed to measure diameters or burial depths on arbitrary cross-sections or automatically calculate excavation and backfill volumes with a single click. This allows site supervisors and construction managers to grasp the necessary numeric information immediately without having to create CAD drawings or perform manual calculations. Real-time sharing between site and office also enables office staff to give instructions while viewing the point-cloud model remotely, or to advance decisions about spoil handling and material procurement without being on site.

3. On-site utilization via AR visualization (for maintenance): Accumulated 3D data of buried pipes can be displayed on-site with AR during inspections or renovation work. For example, when the same road is excavated years later by another project, traditionally workers would pull out the old drawings to estimate the burial positions and verify them by trial excavations, which is time-consuming. With 3D record data, however, launching an AR app on a smartphone and pointing the camera at the ground immediately visualizes the positions and routes of pipes beneath the road surface. Information such as “a single water pipe of diameter ○○ mm runs 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 scene, making the situation obvious at a glance. Depth information is also labeled, so vertical relationships can be shared on-site, such as “this water pipe is buried 1.2 m (3.9 ft) below the surface.” What used to rely on veteran intuition and documents becomes a visible process anyone can perform, based on digital data.

Through this series of steps, the cycle of buried-pipe management—from surveying to recording, data sharing, and on-site confirmation via AR—is digitally integrated. Detailed 3D information that paper drawings and photo ledgers could not reproduce can be preserved, so information does not degrade over time and can always be managed with high-precision spatial coordinates. As a result, accuracy in maintaining buried infrastructure improves, leading to accident prevention and more efficient planning in the future.

Benefits of AR display for buried pipes

By utilizing the RTK × AR technologies described above, various benefits accrue to infrastructure inspection and civil engineering sites. The main effects are summarized below.

• Prevention of underground utility accidents: By accurately identifying the buried locations and depths via AR before excavation, the risk of damaging pipes due to incorrect digging by heavy machinery can be greatly reduced. Visualizing *hidden danger zones* such as gas pipes and power lines in advance significantly strengthens safety measures.

• Improved efficiency and reduced labor: The need to compare drawings with the site and guess positions is eliminated, allowing excavation and investigation to be performed only where necessary, shortening work times. Multiple processes such as surveying, layout marking, and pipe recording can be completed with a single smartphone, enabling reductions in personnel, shortened schedules, and cost savings.

• Improved recording accuracy: Digital records from point-cloud scans can save the position and shape of buried objects in millimeter-level detail. These data are far more accurate than paper drawings or verbal handovers and serve as a reliable information base for future maintenance ledgers. Data accumulated in the cloud are not subject to loss or degradation.

• Advanced maintenance and inspection planning: AR enables innovations in renewal planning and periodic inspections of aging pipes. By overlaying current 3D data with past repair histories on-site, it becomes quick and precise to identify sections that need replacement and to consider reinforcement measures. For example, in surveys for potential road collapse, displaying void positions found by subsurface radar and sewer deterioration data in AR while marking the site reduces the chance of overlooking risk areas. This data-driven approach allows much more efficient preventive maintenance planning.

• Improved information sharing and communication: AR visualization serves as a common language on site. For roadworks involving multiple utility owners—water, gas, communications, etc.—integrating each party’s pipe data and displaying them together in AR allows everyone in a joint site inspection to share the same underground view. This reduces the need to compare paper drawings manually and prevents misunderstandings and transmission errors. It also facilitates explanations to clients and nearby residents, as one can intuitively show “these are the pipelines running under this road” through a smartphone, smoothing understanding and consensus-building.

• Promotion of on-site DX: Introducing RTK × AR strongly promotes digital transformation (DX) at construction sites. It aligns with the Ministry of Land, Infrastructure, Transport and Tourism’s *i-Construction* initiatives, contributing to productivity gains and advanced safety management through ICT and 3D data. Tasks that once relied on experience and intuition become data-driven, and visualization enables anyone to make accurate judgments and perform work correctly. Consequently, defects and rework are reduced, contributing to lower life-cycle costs for infrastructure maintenance and management.

Field cases and future prospects

This RTK × AR buried-pipe visualization technology is already being used in actual field sites. Domestically, a startup has developed a system that combines a tablet with an RTK positioning unit to display buried pipes on-site in AR. Without spreading drawings or performing trial excavation, workers can spatially grasp buried objects on-site, contributing to improved safety and work efficiency. Field trials reported that pipe installation records could be completed without photography or CAD drawing creation, and that later re-excavation works could immediately locate pipes using AR display, demonstrating significant effects. Workers have praised the system, saying, “Exploration of buried objects that used to rely on intuition can now be done by anyone,” and “the operation was intuitive and could be used without training,” indicating promising adoption on sites.

Looking abroad, outdoor high-precision AR systems are gaining attention as pioneering technologies in the construction industry. Systems that combine high-performance GNSS receivers and AR are emerging, enabling centimeter-accurate overlaying of 3D design models onto real-world scenes through a smartphone, making it possible to share and validate complex BIM models and underground utility information on-site. Both in Japan and overseas, initiatives for construction DX and smart maintenance using RTK × AR are accelerating, with adoption expanding across a wide range of projects from bridge construction to water and sewage maintenance.

Going forward, it is highly likely that such high-precision AR technologies will become more generalized and simplified, becoming a new industry standard. A future in which each worker casually points a smartphone on-site to check design drawings and the status of underground utilities via AR is approaching. Without relying on expensive surveying instruments or specialized skills, everyone will be able to handle accurate, real-time information based on spatial coordinates, further accelerating a productivity revolution in construction and infrastructure sectors.

Conclusion: Simple surveying and AR display realized by LRTK

The visualization of buried pipes using RTK × AR has the potential to dramatically change infrastructure maintenance and civil engineering sites. Overlaying digital data onto the real world with centimeter-level accuracy (half-inch accuracy) is shifting tasks that used to depend on skilled experience toward smart, data-driven construction. One solution drawing attention as an easy-to-use on-site implementation of this cutting-edge technology is LRTK.

LRTK is an integrated system that enables anyone to achieve centimeter-level positioning and AR visualization using a smartphone with an attachable small RTK-GNSS receiver and a dedicated app. Many conventional AR surveying tools require pre-placed markers or complex initial calibration, but with LRTK, RTK often achieves a fix within tens of seconds after powering on the device, allowing high-precision AR to start immediately. No special calibration work is required, and it is ready for immediate use on site. Cloud integration enables seamless operations such as downloading design data or point-cloud survey data for AR display on the spot, or instantly uploading and sharing data measured on-site. The system is designed for intuitive use by non-experts, and there have even been reports that a single smartphone per person was sufficient for surveying, layout marking, inspection, photo recording, and AR simulation.

By utilizing LRTK, sites can dramatically improve productivity and safety without expensive equipment or large teams. Beyond visualizing buried pipes, it can be applied to verifying as-built conditions of structures, construction navigation, and a wide range of other uses—truly a “versatile surveying tool” and a trump card for on-site DX. Surveying companies, municipal public works departments, and construction contractors: by introducing this advanced RTK × AR technology into your operations, why not step into a new stage of smart infrastructure inspection? For more information about products and case studies, please visit the [LRTK official site](https://www.lrtk.lefixea.com/). Use LRTK to evolve your sites to the next level.

FAQ

Q: What is AR display of buried pipes? A: It is the use of AR (augmented reality) technology to make the positions of underground pipes and cables visible through a camera. By pointing a smartphone at the ground, virtual pipe models are overlaid on the real-time video, allowing you to check the underground pipes as if you were seeing through the surface.

Q: Why is high-precision positioning necessary for AR display of buried pipes? A: To accurately overlay virtual models onto the actual buried positions, the smartphone’s position and orientation must be known to centimeter-level accuracy. Ordinary GPS has meter-level errors, which would cause pipes to be misaligned in AR and prevent accurate “see-through.” Using high-precision positioning technology such as RTK-GNSS allows the smartphone’s position to be determined within a few centimeters, so virtual pipes can be matched precisely to real locations.

Q: How is the positional data of buried pipes obtained? A: AR display of buried pipes requires pre-acquired 3D data of pipe positions. For new piping, the pipes are 3D-recorded with a smartphone LiDAR scan + RTK positioning before backfilling. For existing buried pipes, you can create AR-ready underground data by combining past drawings with currently RTK-measured coordinates, or by importing point-cloud data derived from subsurface radar surveys.

Q: Can buried pipes be seen through with only a smartphone? A: Yes. By combining a modern smartphone with a small RTK-GNSS receiver, it is possible. The smartphone’s built-in camera, IMU, and LiDAR provide AR functionality, and external RTK positioning delivers centimeter-level location information, allowing accurate display of 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-based visualization of buried pipes using a smartphone. It consists of a lightweight RTK-GNSS module that attaches to a smartphone and a dedicated app, allowing on-site display and surveying of buried-pipe 3D data without complicated settings or special markers. For details, see the [LRTK official site](https://www.lrtk.lefixea.com/).