See Through the Ground with Your Smartphone Before Excavation! Safely Confirm Buried Pipes with AR Display

Table of Contents

• Challenges in Subsurface Infrastructure Maintenance and Management

• Technology for Seeing Buried Pipes with AR

• Centimeter-Level Positioning Enabled by RTK-GNSS

• Workflow for 3D Scanning Records of Buried Pipes and AR Visualization

• Expected Benefits for Infrastructure Inspection and Construction

• Field Cases and Future Developments

• Conclusion: Simple Surveying and AR Display Realized by LRTK

• FAQ

Challenges in Subsurface Infrastructure Maintenance and Management

The most frightening accidents during roadworks or site excavation are those in which buried water pipes, gas pipes, or power and communication cables are accidentally damaged. Breaking an aging water main can lead to a large-scale leak, a gas pipe can cause gas leaks or explosions, and cutting power or communication lines can trigger local outages or service disruptions that seriously affect daily life. In fact, many incidents of damage to buried facilities are reported every year domestically, and a large number of them are caused by not having an accurate understanding of what is buried where.

To prevent such accidents, meticulous care has long been taken in the management of buried pipes. During installation, positions and depths of piping are surveyed and recorded before backfilling, and photos and drawings are kept. On site, experienced workers rely on those drawings and surface markings to proceed with excavation, guessing “there should be a pipe around here.” As needed, ground-penetrating radar is used to check for buried objects, or trial excavations are performed for direct confirmation. However, management that depends on paper drawings and veterans’ intuition has its limits, and it is not easy to mentally track the precise relationships of pipes that intersect complexly underground. Especially in urban areas that have undergone many renovations, the information on drawings often diverges from the actual buried conditions on site, and cases where an unexpected pipe appears at a depth thought to be clear are not uncommon.

In short, the fundamental challenge in infrastructure maintenance is “how to make the invisible visible.” If underground structures could be intuitively visualized, troubles during excavation could be avoided and inspections and replacement planning for aging pipes would be dramatically more efficient. What is now attracting attention is the “visualization” of buried pipes using AR (augmented reality) technology.

Technology for Seeing 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. Using AR, buried pipes and cables can be displayed virtually in a form that is immediately visible on site. For example, if you point a smartphone or tablet camera at the ground, the screen can depict underground water or gas pipes as if you were seeing through the surface, allowing workers to intuitively understand “what is buried directly under these feet and how.” Rather than relying on drawings or guesswork, you can confirm underground structures on site as if visually inspecting the actual objects.

However, accurately “seeing through” buried objects with AR requires advanced alignment techniques. Relying on a phone’s built-in GPS or electronic compass can result in planar position errors of several meters, causing virtual pipe models to be displayed far from their actual buried positions. This is far from the accuracy required to call it “seeing through” and could lead to dangerous misidentifications. Conventional AR systems also often required placing markers (alignment targets) on site or manually adjusting model positions at the start. Placing markers or manually aligning across wide areas of roads and buried utilities is impractical.

To solve these issues, a new approach combining smartphone + LiDAR + RTK-GNSS has emerged: “markerless high-precision AR.” Modern smartphones include advanced AR platforms that track device motion in space from camera images and IMU (inertial measurement unit) data. Higher-end models also have small LiDAR sensors that can acquire the surrounding environment as 3D point clouds in real time. LiDAR enables high-precision capture of ground and object shapes and distances, allowing virtual objects (such as underground pipe models) to be stably overlaid onto the real world and naturally handle occlusion when objects hide behind others. In other words, smartphones can now instantly build a three-dimensional map of their surroundings in addition to camera imagery, greatly strengthening the foundation for AR displays.

The final piece is for the device to know exactly “where it is.” Here, high-precision positioning technology RTK-GNSS (Real-Time Kinematic satellite positioning) plays a crucial role. As noted earlier, standalone phone GPS can have meter-level errors, but by using RTK-type correction data, position errors can be reduced to a few centimeters. RTK positioning has long been used in surveying, and recently GNSS receivers have become smaller and lighter, with RTK-capable GNSS receivers that can be attached to smartphones becoming available. By combining such external high-precision GNSS with a smartphone, the device’s position in a public coordinate system can be known with centimeter-level accuracy, minimizing the mismatch between virtual models and the real world.

By combining the ground-shape point cloud obtained by a phone’s LiDAR with global self-position information from RTK-GNSS, practical accuracy for on-site “AR see-through of buried pipes” can be achieved. For example, if a pre-acquired 3D model of buried pipes (or a 3D mesh generated from point clouds) is loaded onto the phone, visiting the site later and pointing the camera at the ground will display the underground model precisely where it lies under the real surface. Because the phone recognizes the ground itself as a mesh model via LiDAR scanning, virtual pipes appear properly occluded as if buried, and depth relationships can be intuitively understood. This markerless AR see-through technology, where models do not drift even when walking freely without special markers, is turning previously black-box underground infrastructure into on-site “visible information.”

Centimeter-Level Positioning Enabled by RTK-GNSS

High-precision positioning by RTK-GNSS is the core technology supporting AR visualization of buried pipes. RTK (Real-Time Kinematic) is a method that dramatically improves GNSS positioning accuracy by using real-time correction information from a reference station, allowing relative positioning against a fixed reference point to reduce position errors to within a few centimeters. While standalone GPS typically includes meter-level errors, RTK can achieve horizontal and vertical accuracy on the order of a few centimeters (cm level accuracy (half-inch accuracy)), which has long been valued in civil engineering and surveying.

Making RTK positioning easy to use on site is the emergence of ultra-compact RTK-GNSS receivers. For example, a device called “LRTK Phone,” developed by a startup spun out of Tokyo Institute of Technology, enables RTK positioning simply by attaching a small receiver weighing approximately 165 g and about 13 mm (0.51 in) thick to the back of a smartphone. It runs for about 6 hours on its internal battery and can be attached and removed with one touch like a smartphone case. It also supports the centimeter-class augmentation service provided by Japan’s quasi-zenith satellite system “Michibiki” (CLAS) (cm level accuracy (half-inch accuracy)), so it can maintain stable centimeter-level accuracy with satellite-borne correction signals even in mountainous areas without mobile communication. In urban areas, conventional network-based RTK correction services can be used, allowing positioning errors to be corrected to within a few cm in real time anywhere in Japan. In other words, the integration of such high-precision GNSS devices with smartphones has made the era in which “anyone can carry a high-precision positioning tool in their pocket” a realistic prospect.

A future in which each field technician carries a smartphone with a high-precision GPS device, taking it out to perform surveys or AR displays as needed, is already coming into view. In current systems, intuitive Japanese UIs display positioning results and navigation information on the phone screen, making them easy to use without specialized expertise. For example, stake-out (layout) tasks that once required two people can now be done by a single person using a lightweight monopod with a phone + RTK attached, following on-screen guidance to place points accurately. As high-precision GNSS positioning becomes easy for anyone to use, the productivity and accuracy of surveying and construction management tasks will dramatically improve.

Workflow for 3D Scanning Records of Buried Pipes and AR Visualization

• 3D recording of buried pipes (during construction): For example, when new pipes are buried under a road, the pipes and excavation area are scanned and recorded with a LiDAR-equipped smartphone before backfilling. A smartphone with an RTK-capable GNSS receiver automatically tags the acquired point cloud data with high-precision world coordinates and uploads it to the cloud. The system automatically generates a 3D mesh model of the pipe portions from the point cloud, digitally recording the route, depth, and shape of the buried pipes accurately. Traditionally, dimensions were measured after backfilling to create drawings, or pipe routes were sprayed on temporarily restored surfaces, but with this workflow a detailed 3D record is completed simply by scanning.

• Data sharing and management: The obtained point cloud and model data of buried pipes can be shared immediately via the cloud and accessed from office PCs or other devices. If incorporated into management ledgers or GIS as asset information, the data will be useful for future inspection planning and coordination with other works. Advanced processing, such as measuring diameters and depths on arbitrary cross-sections from the point cloud or automatically calculating excavation/backfill volumes, can also be executed with a single click on cloud services. This allows site supervisors to obtain required numerical information without creating CAD drawings or doing manual calculations. Real-time sharing of data between the field and the office means office staff can issue instructions while checking 3D models remotely, or advance tasks like spoil handling and material procurement even if not physically present.

• On-site use of AR visualization (during maintenance): Accumulated 3D data of buried pipes can be used for on-site display via AR during future inspections or rehabilitation work. For example, when a road must be reopened years later for other works, there is no need to rely on old drawings or perform trial excavations. With 3D record data, launching an AR app on a smartphone and pointing the camera at the ground instantly reveals the positions and routes of pipes buried beneath the surface. Information such as “a water pipe of diameter ○○ mm runs directly below here” or “a gas pipe runs parallel further in” will be displayed as colored virtual pipe models overlaid on the real scene, making it immediately obvious to anyone. Depth information can also be shown as labels, so vertical positions like “this water pipe is buried 1.2 m (3.9 ft) below the surface” can be shared on site. In this way, the task of locating buried objects that once relied on veteran intuition and legacy documents becomes a visible workflow anyone can perform based on digital data.

This end-to-end workflow digitally integrates surveying records, data sharing, and on-site AR confirmation. Detailed 3D information that could not be reproduced with paper drawings or photo ledgers can be preserved, preventing information degradation over time and enabling high-precision spatial coordinate management whenever needed. As a result, the accuracy of buried infrastructure maintenance improves, contributing to accident prevention and more efficient planning in the future.

Expected Benefits for Infrastructure Inspection and Construction

• Prevention of accidents involving buried utilities: By accurately confirming buried positions and depths with AR before excavation, the risk of damaging pipes with excavation machinery can be significantly reduced. Visualizing hidden danger spots such as gas pipes or power lines in advance greatly strengthens safety measures.

• Improved efficiency and labor savings: Eliminating the need to compare drawings with the site and guess positions reduces wasted effort, allowing excavation and investigation to be performed efficiently where needed. Multiple tasks such as surveying, stake-out, and pipe recording can be completed with a single smartphone, enabling reductions in personnel, shorter schedules, and cost savings.

• Improved recording accuracy: Digital records from point cloud scans can preserve the position and shape of buried objects with millimeter-level precision. These data are far more accurate than relying on paper drawings or verbal handovers and provide a reliable information base for future maintenance ledgers. With data stored in the cloud, concerns about loss or degradation are eliminated.

• Advanced maintenance and inspection planning: AR can innovate replacement planning and periodic inspections for aging pipes. By overlaying current 3D data with past repair histories on site, sections requiring replacement or reinforcement can be identified and evaluated quickly and accurately. For example, in sinkhole risk surveys, results from ground-penetrating radar indicating void locations and sewer deterioration data can be displayed in AR while marking the site, enabling comprehensive risk identification without omissions. Such data-driven inspection planning dramatically improves preventive maintenance efficiency.

• Improved information sharing and communication: AR visualization functions as a common language on site. In roadworks where multiple utility operators for water, gas, and communications are involved, integrating each party’s pipe data and displaying them together in AR lets everyone share the same “visible underground” information during joint on-site meetings. This reduces the need to reconcile paper drawings and prevents misunderstandings or miscommunications. When explaining works to clients or nearby residents, AR allows intuitive demonstration—“under this road run these utility routes”—facilitating smoother 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* initiative and is attracting attention as part of smart construction and infrastructure maintenance DX. With consistent, data-driven operations from surveying to construction and maintenance, overall process efficiency and sophistication improve. Aggressive adoption of digital technologies also helps address industry challenges such as labor shortages and skill transfer, and is expected to contribute to reduced life-cycle costs in the long term.

Field Cases and Future Developments

RTK×AR visualization of buried pipes is already being used in real construction sites. Domestically, a startup has developed a system that combines an RTK positioning unit with a tablet to display underground pipes in AR on site. Without spreading drawings or performing trial excavations, users can tridimensionally grasp the positions of buried utilities on the spot, contributing to improved safety and work efficiency. Field trials reported that records of buried pipe works were completed without photos or CAD drawings, and in later re-excavation the pipes could be immediately located via AR display—demonstrating significant benefits. Workers also reported that “searching for buried objects based on gut feeling has become something anyone can do” and “the operation was intuitive and usable without training,” indicating positive reception and traction on sites.

Abroad, outdoor high-precision AR systems are attracting attention as pioneering technologies in the construction industry. Systems combining high-performance GNSS receivers with AR can overlay 3D design models onto real scenes through a smartphone at centimeter-level accuracy, enabling intuitive on-site sharing and verification of complex BIM models and underground utility information. Both in Japan and overseas, efforts around RTK×AR-driven construction DX and smart maintenance are accelerating, with adoption expanding across projects from bridge construction to water and sewer maintenance.

In the future, this high-precision AR technology is likely to become more generalized and simplified, potentially becoming the new industry norm. A future in which every worker casually points a smartphone at the site to check designs and underground utilities via AR is approaching. By enabling anyone to access accurate, real-time spatial information without expensive equipment or specialized skills, productivity revolutions in construction and infrastructure are expected to accelerate.

Conclusion: Simple Surveying and AR Display Realized by LRTK

The visualization of buried pipes via RTK×AR has the potential to dramatically change infrastructure maintenance and civil engineering practices. By overlaying digital data onto real space with centimeter-level accuracy, tasks that once relied on experienced personnel are beginning to shift toward data-driven smart construction. One notable solution making this cutting-edge technology easy to use on site is LRTK.

LRTK is an integrated system that delivers centimeter-level positioning and AR visualization to anyone via a small RTK-GNSS receiver attached to a smartphone and a dedicated app. Many AR surveying tools require pre-placed markers or complicated initial calibration, but with LRTK the RTK typically fixes in tens of seconds after powering on the device, allowing immediate start of high-precision AR. No special calibration work is required, and its ease of use on site is a major feature. Cloud integration allows seamless downloading of design data and point cloud survey data for AR display, and measured data taken on site can be uploaded and shared instantly. The system is designed to be intuitive for non-experts, and there have been reports that one smartphone per person could cover surveying, stake-out, inspection, photo recording, and AR simulation.

By using LRTK, sites can dramatically improve productivity and safety without costly equipment or large teams. Beyond see-through display of buried pipes, LRTK can be applied to as-built verification of structures and construction navigation, and it stands to become a true “universal surveying instrument” and a trump card for on-site DX. Surveying companies, municipal civil engineering departments, and construction contractors are encouraged to adopt this advanced RTK×AR technology 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/). If interested, please take a look. Let LRTK evolve your sites to the next stage.

FAQ

Q: What equipment and preparations are needed to display buried pipes in AR on site? A: You need a smartphone or tablet and an AR app. Latest iPhones and iPads have AR functionality (ARKit) built in and can be used without extra hardware, but to improve alignment accuracy it is recommended to use a high-precision GNSS receiver such as the LRTK Phone. Also, pre-uploading the design data you will use (3D models or drawing files of buried pipes) to the cloud so it can be selected from the device, and performing coordinate-system adjustments in advance as needed, will allow a smoother start.

Q: Can AR be displayed with only 2D drawing data, or is a 3D model necessary? A: AR display is possible even with only 2D plans. Even without a 3D model, you can project route lines from a plan onto the ground or display virtual markers and symbols at important points. For example, you can place a CAD plan (DXF) or an image of a plan as a background in AR to check for discrepancies with the site. However, 3D models include height information and allow three-dimensional clash checks, so it is preferable to prepare 3D data if possible.

Q: How accurate is AR display of buried pipes? A: Standalone phone GPS or basic AR can have offsets from several tens of centimeters to several meters. That may be acceptable for rough checks but is insufficient for precisely locating excavation points. Using high-precision positioning like LRTK can reduce horizontal and vertical errors to within a few cm, enabling AR overlays that largely coincide with buried pipes. The ability to ensure centimeter-level accuracy suitable for real construction is the major differentiator.

Q: Is specialized knowledge or training required? Can site staff use it? A: No advanced CG software skills are required; generally, anyone can use the app by following on-screen instructions. LRTK’s UI is designed for users with little surveying experience, enabling positioning and AR display via button operations. With a short training session for site staff, it can be immediately useful in everyday construction management.

Q: Is it necessary to place markers or reference points in advance for AR display? A: When using LRTK, special marker placement is basically unnecessary. The device itself becomes the reference point via GNSS, and models are automatically placed at prescribed coordinates. However, in indoor locations where GPS is unavailable, you will need to rely on ARKit plane detection or visual markers. In such cases, placing clear visual references (for example, a corner of a wall or a distinctive floor pattern) to align models will improve accuracy. For outdoor and wide sites, coordinate alignment via LRTK is the most efficient.