Improving Maintenance of Buried Underground Pipes: Boost Inspection Efficiency Threefold with Smartphone × AR

Underground buried pipes for water and sewage, gas, electricity, and communications are indispensable lifelines of social infrastructure, but because they are hidden underground, the persistent challenge in maintenance and management has been that they are “invisible.” Even if excavation is carried out based on drawings and experience, accidentally damaging pipes or cables can lead to serious accidents such as water leakage, gas leaks, or power outages. In fact, every year across the country there are many incidents of buried pipe damage caused by accidental excavation, and many of these are attributed to an inability to accurately grasp the locations of buried assets. So how can invisible buried pipes be accurately identified and inspected and managed safely and efficiently? A recently notable solution combines the use of the smartphone, AR (augmented reality) technology, and high-precision GNSS positioning (RTK). If the underground pipes can be visualized through a smartphone screen as if using X-ray vision, on-site work efficiency will dramatically improve. In some cases, inspection work efficiency is expected to increase to three times or more compared with conventional methods, contributing greatly to accident prevention. This article organizes the conventional challenges and background of underground buried pipe maintenance and management, then explains in detail the advantages, use cases, and specific technical points of inspection methods using smartphone × RTK × AR. Finally, as an easy-to-implement tool for this new technology, we introduce a simple surveying solution using LRTK.

Conventional challenges and background in maintaining and managing buried underground pipes

In maintaining and managing buried underground pipes, operators have long been troubled by uncertain information and invisible risks. During construction, measures are taken such as measuring and recording the positions and depths of installed pipes in drawings and photos, and marking pipe routes on road surfaces with spray paint. On site, workers typically rely on those drawings and ground markings, with experienced workers digging while applying past memory and intuition, thinking “a pipe for XX should run around here.” As needed, they also search for pipes with metal detectors, survey underground installations with ground-penetrating radar (GPR), or directly confirm with trial excavations. These analog management methods have somehow ensured safety, but their limitations are clear.

With conventional methods that rely on paper drawings and oral information, discrepancies between actual on-site conditions and drawing information tend to occur, especially in urban areas where buried pipes intersect complexly. In areas where renovations have been repeated over many years, pipes not listed in old ledgers may have been added later, and it is not uncommon for the positions on drawings to be offset from the actual positions. As a result, unexpected piping can appear at points excavated by heavy machinery under the assumption that “there should be nothing here,” causing near-miss incidents—such failure cases continue to occur. Even veteran workers find it difficult to accurately imagine in their heads the three-dimensional intersections of multiple pipes underground. Combined with insufficient upkeep of ledgers and fragmented information sharing on site, maintenance and management of buried pipes tends to become a person-dependent and uncertain task.

Site confusion from accidental excavation and ledger deficiencies, and the importance of inspection accuracy

Why do accidents related to buried underground pipes occur? Behind them lie a complex interplay of incomplete buried information and human error. Actual accident reports point to causes such as “insufficient instructions about buried objects in pre-work meetings,” “blindly trusting old drawings and neglecting safety measures,” and “ledger entry errors or failure to update buried pipe ledgers.” Especially in projects involving multiple operators, breakdowns in information sharing tend to cause on-site confusion. If water, gas, communications, and other infrastructure staff each bring only their own pipe maps to a job, the risk of accidentally damaging each other’s facilities increases.

Once an unexpected buried object is exposed, the site becomes greatly confused. Time is consumed by confirming “What on earth is this pipe?” and “Which operator manages it?” Work is suspended, and efforts are directed toward securing safety around the site and contacting related departments. If an avoidable accidental excavation occurs, enormous costs for restoration and compensation can arise. To prevent such on-site confusion and accident risks, accurate position confirmation and inspection prior to work are indispensable. If the positions and depths of buried pipes can be identified to within a few centimeters (a few in) and reliably communicated on site, the safety and efficiency of excavation work will improve dramatically. In other words, improving inspection accuracy in maintenance and management is the key to preventing accidental excavation and achieving smooth on-site operations.

Possibilities of smartphone positioning and GNSS/RTK technology

With recent advances in positioning technology, smartphones can now be used as high-precision positioning devices. Previously, obtaining centimeter-level positioning accuracy required expensive GPS surveying equipment and skilled technicians, but now the RTK-GNSS (real-time kinematic positioning) mechanism can be used easily on smartphones. RTK is a technology that uses correction information from a base station to correct GPS positioning errors in real time; compared to ordinary GPS with errors of several meters (several ft), RTK can achieve accuracy of a few centimeters (a few in) both horizontally and vertically. While standalone smartphone GPS accuracy was previously insufficient for locating buried pipes, attaching a compact RTK-capable GNSS receiver enables smartphones to perform position identification comparable to surveying instruments.

For example, if a dedicated small RTK receiver is attached to the back of a smartphone and connected to correction information services (such as base station data or QZSS CLAS signals), centimeter-level positioning can begin in about one minute (cm level accuracy (half-inch accuracy)). Even in mountainous areas without cellular reception, positioning accuracy can be maintained using satellite augmentation signals, enabling stable positioning anywhere in Japan. This makes the era in which each maintenance worker can “carry high-precision GNSS in their pocket” a realistic prospect. In practice, smartphone screens display current coordinates and positioning accuracy in a simple Japanese UI that anyone can operate without specialized knowledge. Tasks that previously required two people, such as setting batter boards or marking stake positions, can be done by one person: mount the smartphone on a pole and follow on-screen guidance to mark positions accurately by oneself. In short, the combination of smartphone + RTK has the potential to dramatically streamline on-site position identification tasks and greatly lower the barrier to locating buried pipes and performing surveys.

Advantages of visualization and work navigation using AR display

Once high-precision positioning information from RTK is obtained, that data can be used to visualize buried pipes on site with AR (augmented reality) displays. Looking at the ground through a smartphone or tablet camera, water pipes, gas pipes, and cables that should be buried underground are overlaid on the surface as CG models. Because the imagery is like viewing the pipes directly through the ground, workers can intuitively grasp “what runs directly beneath their feet and where.” For example, if the screen displays in color “one main water pipe with a diameter of 200 mm (7.87 in) is buried at a depth of 1.2 m (3.9 ft) directly below here” and parallel-running gas pipes further back, it becomes clear to anyone at a glance. There is no need to pore over drawings and guess—the greatest strength of AR is that it allows confirmation of invisible structures in a visible form while on site.

The benefits of this visual “seeing” are numerous. First, in terms of safety, heavy machinery operators and all workers can recognize hazardous locations in advance, helping to prevent accidental excavation. Because the areas to be excavated and buried objects to be avoided are clearly displayed, the risk of damage from excessive digging is greatly reduced. In terms of work efficiency, the effort to transcribe dimensions from drawings onto the field is eliminated, reducing wasteful excavation caused by misinterpretation or assumptions. Navigation features can be used to mark excavation locations by following AR guide lines, or to install new pipes while maintaining specified clearances from existing pipes. Even inexperienced workers can perform tasks at the correct position and depth simply by following AR-displayed instructions, removing the need to rely on the intuition of skilled workers. Furthermore, AR imagery shared on site serves as a common language, making it easy to align understanding among all stakeholders. Transmission errors such as “that’s not where I thought it was” or “what I heard was different” are also prevented. In these ways, visualization and navigation of buried pipes with AR bring unprecedented safety and efficiency benefits to the field.

Specific use cases

Inspection of buried pipes using smartphone × RTK × AR can be applied to maintenance and management across various infrastructures, from water and sewage to agricultural water, gas, electricity, and communications. Below are examples of expected use cases in each field.

Application to water and sewage infrastructure

Smartphone × AR technology is highly effective for the maintenance and management of water mains and sewer pipes. Water pipes pose concerns about leakage from aging, and seismic retrofitting and replacement works are proceeding in many places. On such sites, if the exact positions and depths of buried pipes can be visualized with AR, narrowing excavation areas and checking for interference with other buried objects becomes smooth. For example, when replacing an old main water pipe under a road, if the AR displays the existing water main route, branching positions, and even the parallel sewer pipe locations, it becomes easy to install new pipes while maintaining appropriate clearance. Sharing a “visible map” of buried objects on site enables more accurate selection of trial excavation points and reduces time spent on unnecessary digging or searching for pipes.

In the sewer sector, AR is useful for manhole inspections and pipeline rehabilitation works. If workers can perform tasks while understanding pipe diameters, slopes, and routes—information not visible from the surface—via AR, planning for excavation in narrow alleys and equipment transport becomes easier. Especially in urban areas where water and sewer pipes are buried alongside other lifelines, understanding positional relationships in advance with AR is effective in preventing damage at crossing points. Water bureaus and sewer departments are beginning to combine smartphone high-precision positioning with AR to digitize pipe ledgers. By recording and sharing buried pipe information in 3D rather than on paper or 2D drawings, future inspection planning and emergency response will be much more efficient.

Application to maintenance of agricultural watercourses and pipes

In rural areas, smartphone × AR technology also helps streamline management of agricultural water. Many agricultural watercourses include sections with buried pipelines, and older irrigation networks may lack precise pipe maps. If local water user associations or municipal staff can easily locate and record water pipe positions with smartphone surveying, future maintenance becomes substantially easier. For example, to avoid accidentally damaging existing supply pipes during field consolidation, operators can scan pipe routes with a smartphone and save them to the cloud beforehand; later, they can visualize them on site with AR and excavate safely.

Because GPS environments in rural areas tend to be favorable, RTK centimeter-level positioning (cm level accuracy (half-inch accuracy)) can be stably used. Patrol inspections across extensive rice fields and farms while displaying the route of buried water pipes on a smartphone prevent overlooking buried valves or supply inlets. Even where suspected subsurface leakage exists, reproducing the pipe route in AR allows pinpoint excavation for confirmation. The advantage is that site staff themselves can digitize asset information with simple surveying without calling specialized surveying teams. Without introducing expensive equipment, smartphones and small GNSS receivers can realize visualization of agricultural water infrastructure, enabling efficient management even with limited personnel.

Application to gas pipeline facilities

Gas pipelines require especially cautious handling among buried infrastructures. Damaging a gas pipe can cause leaks or explosions, so avoiding damage at construction sites is imperative. Visualization of buried pipes using smartphone AR significantly contributes to safety measures in gas pipeline work. Before road excavation or building construction, if gas companies import pipe route data into smartphones and share it via AR so all workers can see it, they can plan excavation procedures with an accurate understanding of buried gas pipe locations and depths. Heavy machinery operators can visually confirm gas pipe routes and clearly determine when to switch to hand digging.

Gas operators can also scan and record burial depth and routes with a smartphone before backfilling, preparing for future maintenance. Even after backfilling, AR displays will show accurate burial depths on site, useful as materials for cautioning other contractors during periodic inspections. Plastic gas pipes are hard to detect with metal detectors, but AR displays colored virtual models clearly, preventing oversight. In emergency responses to gas leak reports, field crews can instantly display the buried pipe network by holding up a smartphone, enabling rapid valve shutoff and leak location identification. For gas pipeline maintenance, smartphone × RTK × AR can become a new infrastructure management tool supporting safe and rapid responses.

Application to power and communication cables

In urban areas, power lines and communication cables are increasingly buried underground. Cutting a power cable during construction can cause widespread blackouts, and severing a fiber-optic cable can disrupt communications, both with huge social impact. With smartphone AR, operators can visualize underground power and communication networks in advance, greatly reducing the risk of damage during excavation. Underground power transmission lines are usually protected by strong warning sheets, but showing accurate position and depth in AR helps backhoe operators pay close attention to excavation depth control.

Communications cables often reside in nonmetallic ducts, making position detection with traditional detectors difficult. But if cable routes are pre-registered in the AR system, accurate routes can be identified from the surface. In roadworks where multiple communications operators’ cables are intertwined, displaying each company’s buried positions in different colors in AR enables smooth joint field coordination. For power and communications companies, recording 3D data of pipelines with a smartphone and reflecting them in ledgers offers significant benefits and leads to DX (digital transformation) in future asset management. For example, when laying new communication ducts, confirming clearance from existing power and water pipes on AR during route planning can prevent design errors and construction troubles. In underground installations of power and communications infrastructure, smartphone AR technology becomes a powerful support tool for safety confirmation and collaborative work.

Methods and precautions for point-cloud recording, depth management, and overlay verification

To fully utilize smartphone × RTK × AR, it is important to follow procedures for accurate 3D recording and appropriate data utilization. Ideally, newly buried pipelines and exposed existing pipes should be recorded in detail by point-cloud scanning. Using a LiDAR-equipped smartphone to scan the pipe and surrounding excavation area yields high-density point-cloud data showing pipe positions and shapes in seconds. If positioning is done with RTK-GNSS at the same time, the point cloud is automatically assigned absolute world coordinates (latitude, longitude, height). The acquired point-cloud data are uploaded to the cloud for storage, and the system automatically generates a 3D model (mesh) of the piping portions. In this way, the exact route and depth of buried pipes are digitally and permanently recorded.

The recorded 3D data are incorporated into maintenance ledgers and GIS for asset management. From the perspective of depth management, the point-cloud model allows cross-sections at arbitrary locations to measure burial depth and pipe diameter. If surrounding terrain and the road surface are also scanned, the depth from the ground surface to the top of the pipe can be accurately determined. Displaying this data later in AR enables on-site sharing of depth information labeled like “a pipe is located at ○ m (○ ft) below the ground.” While conventional paper ledgers are prone to missing depth records and measurement errors, digital point clouds can be stored without mistakes, ensuring robust vertical management.

Next is overlay verification of recorded data. By displaying the acquired 3D model in AR on site and comparing it with real-world features, data reliability can be verified. For example, confirm that the virtual model of the scanned pipe correctly corresponds to known ground markers (manhole covers, valve handles, etc.). If there is an offset, correct the positioning coordinate system or finely adjust the model’s position. This calibration process improves AR display accuracy and reliability. During construction, it is also possible to overlay the design-route model from drawings with the scanned on-site pipe model to check differences; if offsets exist, immediate corrective action can be taken, aiding as-built inspection.

Finally, pay attention to equipment and environment. To stabilize RTK positioning, receive GNSS signals in as open a sky as possible; in tunnels or under viaducts where signals are blocked, combine measurements with surveying control points or other auxiliary methods. AR apps on smartphones are resource-intensive, so monitor battery levels and device heating and allow rest during prolonged use. Point-cloud data can grow large; use cloud synchronization to avoid filling device storage. When 3D scanning, ensure a sufficient scan range so the entire circumference of the pipe is captured. In narrow trenches, step back and shoot from multiple directions to obtain continuous point clouds. By observing these precautions, you can maximize the effectiveness of smartphone × AR inspections.

Integration with maintenance databases and benefits of cloud sharing

A major appeal of collecting buried pipe data with a smartphone is that it can be instantly shared and accumulated via a cloud platform. When point-cloud scans and positioning are performed on site, the results (coordinate values, 3D models, site photos, etc.) are uploaded in real time to the cloud-based maintenance database. There is no need to transfer data later via USB; the field and office can always synchronize the latest information. Managers can view cloud data from office PCs and issue instructions as needed. For example, if a water main is relocated during a road project, the new pipe’s position coordinates and point cloud can be recorded in the cloud ledger on the same day, so other staff can work with updated drawings the following day.

Cloud sharing also facilitates interdepartmental and intercompany information coordination. If a platform centrally manages water, gas, communications, and other infrastructure data, each company need not bring separate drawings to joint worksites. Everyone can refer to the same 3D map on the cloud and confirm it in AR, reducing the time and effort required for coordination. The cloud also accumulates past inspection and repair histories, aiding analysis of aging trends and planning. Digital data do not degrade, so the site can be reproduced with the same accuracy even ten years later, preventing knowledge gaps due to generational changes.

Moreover, cloud services allow permission management for external sharing. By issuing a shared link, you can easily share large point-cloud datasets with contractors and consultants, who can view and measure them in a browser even without high-end dedicated software. This eliminates the hassle of mailing paper drawings or handing over USB drives and enables fast, data-driven communication. In these ways, linking smartphone-acquired field information with a cloud maintenance database dramatically improves the quality and speed of organizational information sharing, directly contributing to more efficient infrastructure maintenance and management.

Accelerating field DX with the introduction of simple surveying using LRTK

When considering implementing the smartphone × RTK × AR buried pipe inspection approach introduced so far at your own sites, choosing the right tools becomes a challenge. Even the latest technologies will not spread on the ground if they require advanced expertise or complex preparation. One solution drawing attention is LRTK, developed by a startup originating from Tokyo Institute of Technology. LRTK consists of a small RTK-GNSS receiver that attaches to a smartphone and a dedicated app, and it enables anyone to perform centimeter-level positioning, point-cloud measurement, and on-site confirmation via AR with ease.

For example, the LRTK receiver “LRTK Phone” weighs only about 150 g and, when magnetically attached to the back of a smartphone, immediately starts high-precision positioning. Leveraging the smartphone’s built-in LiDAR and camera, simply scanning the surroundings generates high-precision 3D point clouds in the cloud, and acquired data can be shared and viewed with one tap. No complex settings or specialized software are required; even users without surveying or AR experience can operate it intuitively. From marking buried pipe positions and recording as-built conditions to AR-based construction navigation, LRTK alone can complete the entire workflow of smart construction.

Such data-driven smart construction aligns with the Ministry of Land, Infrastructure, Transport and Tourism’s *i-Construction* and the broader trend of infrastructure DX. As on-site work shifts from reliance on experience and intuition to data-driven processes, quality defects and rework will be reduced, contributing to lower life-cycle costs for infrastructure maintenance. Adoption is already progressing in the construction industry and municipal civil engineering departments, and LRTK is attracting attention as a “versatile surveying tool that promotes on-site DX.” Those involved in infrastructure maintenance and management are encouraged to use this cutting-edge tool to “visualize the invisible” and take steps toward safer and more efficient site management. If you are interested in simple surveying with LRTK, please visit the [LRTK official site](https://www.lrtk.lefixea.com/) for detailed information and case studies. With a smartphone in hand, this new era of infrastructure inspection methods could greatly advance your field operations.