6 Steps to Visualize Buried Pipes with AR｜Comprehensive Guide from Ledger Preparation to On-site Display

Infrastructure buried underground—water and sewer pipes, gas pipes, power cables, and communication cables—are lifelines that support our lives. However, because these buried pipes are hidden beneath the ground and cannot be directly seen during on-site work, their invisibility itself has become a major challenge for maintenance and construction. For example, if an old water pipe is accidentally damaged during roadworks, it can lead to a large-scale leak; if it is a gas pipe, there is a risk of gas leakage or explosion. Cutting power or communication cables can cause power outages or communication failures in the surrounding area, potentially causing serious disruption to social life. One of the reasons why incidents of damage to underground buried objects continue to occur nationwide every year is that "what exactly is buried there" was not accurately known.

Traditionally, meticulous care has been taken in the maintenance and management of buried pipes to prevent such accidents. During burial work, before backfilling, measurements are taken to record the position and depth of the pipes, photographs are taken, and the information is documented on drawings. On site, relying on construction drawings and markings on the ground, experienced workers have excavated while estimating, "there should probably be some kind of pipe around here." When necessary, subsurface radar surveys or trial excavations are also used to directly confirm the location of buried objects. However, there are limits to management that depends on paper drawings and the intuition of veteran workers, and especially in locations with complex histories of past renovations, such as urban areas, it is not uncommon for the information shown on drawings to differ from the actual buried conditions on site. As a result, there are often reports of cases in which an unexpected pipe has appeared from a place that had been assumed to be clear, giving workers a fright.

In short, the fundamental theme of underground infrastructure management is how to make the invisible visible. If subterranean structures could be visualized intuitively, not only would accidental damage during excavation be prevented, but planning inspections and replacements of aging pipes would also become dramatically more efficient. A promising new solution to this challenge is the “visualization” of buried pipelines using AR (Augmented Reality) technology. AR is a technology that overlays digital information such as CG onto real-world footage seen through a camera, and by simply pointing a smartphone or tablet camera at the ground, virtual models of underground pipes and cables can be displayed in situ. If the positions and routes of buried objects are rendered on the screen as if you were looking through the ground, you can instantly and intuitively grasp what is buried directly beneath your feet and at what depth.

However, to accurately "see through" buried assets with AR displays, advanced alignment technology is indispensable. The accuracy of a smartphone's built-in GPS and electronic compass can result in errors of several meters (several ft), causing the displayed position of the virtual piping model to be significantly offset from the actual buried location. This cannot be used for safety checks and may instead create hazards due to misidentification. Moreover, conventional AR systems required placing markers (alignment marks) at each site or performing an initial calibration by manually adjusting the model position. For roadways and pipe networks that extend over wide areas, placing markers at every location or making manual adjustments each time is impractical.

In recent years, a "markerless high-precision AR" approach combining the latest technologies—smartphone + LiDAR + RTK-GNSS—has emerged to solve this challenge. Modern smartphones come standard with AR platforms that can track device movement in real time using camera imagery and IMU (inertial measurement unit) data. Higher-end models also include a compact LiDAR (light detection and ranging) sensor that can instantly capture the surrounding environment as 3D point cloud data. Because LiDAR can capture distances and shapes to the ground and structures with high precision, virtual objects (such as models of buried pipes) can be stably overlaid onto real space, and occlusion effects where objects are hidden behind others can be represented naturally. In other words, modern smartphones have evolved to the point where, in addition to camera imagery, they can instantly build a 3D map of their surroundings, greatly improving environmental awareness—the foundation for AR display. The remaining final piece is knowing exactly "where the device is" right now. What proves powerful here is RTK-GNSS (real-time kinematic satellite positioning), a centimeter-class high-precision positioning technology (cm-level accuracy; half-inch accuracy). By combining a dedicated high-precision GNSS receiver with the smartphone and using RTK correction data, the device's position can be reduced to errors within a few centimeters (a few inches) in the public coordinate system. The fusion of advanced spatial awareness from smartphone AR and precise self-positioning via high-precision GNSS finally makes possible the "visualization of buried pipes" that eliminates any perceptible discrepancy between real underground structures and virtual models.

Given the technical background described above, AR visualization of buried pipes is no longer a pipe dream. However, bringing this technology into practical use on-site requires thorough preparation and a phased implementation process. In particular, when municipalities and infrastructure operators introduce AR into existing buried-pipe management, it is important to proceed through several steps—from organizing registers and unifying coordinate systems to enabling on-site AR display. In this article, covering underground infrastructure in general—construction, civil engineering, water and sewer, gas, electricity, and telecommunications—we provide a thorough explanation of the practical workflow to visualize buried pipes with AR, laid out in six steps. We hope this will serve as a reference for practitioners at construction consultants, surveying companies, local governments, and infrastructure management companies as they move from the consideration stage of AR adoption to trial operation and then full-scale field utilization.

Step 1: Assessing the Current State of the Buried Pipe Ledger and Digitization

The first step is to organize the ledger records of the buried pipes you have on hand and compile accurate data.

In departments responsible for managing underground infrastructure, drawings and records for various pipelines, such as water and gas, are stored, but their formats and levels of accuracy vary. Information scattered across paper drawings, old CAD data, photo albums, and so on will be reviewed and organized into digital data that can be utilized in AR.

Begin by assessing the current state of buried pipelines. Collect plan views, longitudinal profiles, routing diagrams, records of burial depths, and other relevant documents for the buried pipelines held within the department, and comprehensively identify them, including the most recent updates. If multiple divisions (e.g., water and sewerage departments and gas operators) manage assets separately, it is advisable to obtain data from the relevant parties with a view to future integrated display. In particular, in local governments water and sewerage are often managed within the municipality while gas and communications fall under operators' jurisdiction, so hold consultations for information sharing as needed.

Next, we will proceed with digitizing those materials. If only paper drawings are available, rather than merely scanning them into images, we will, where possible, trace them into CAD or GIS formats to create vector data. We will extract pipe centerlines and buried locations as line data with coordinates, and register attribute information such as diameter, material, and installation year in the digital ledger. This work will turn piping routes that were ambiguous in paper field photos or hand-drawn sketches into clearly defined forms in electronic data. We will also review past construction histories and repair records to check for inconsistencies with older drawings. For example, if there is a record of a pipe found in the field that does not exist on the drawings, we will add it to the data; conversely, if a pipe that has already been removed remains on the drawings, we will delete it—such data cleansing is important. Any latest information obtained through inspection work (for example, measured positions of buried markers or records of deterioration) will also be reflected and used to update the ledger information.

The buried-pipe ledger data prepared in this way forms the foundation for AR implementation. If information is lacking, consider supplementing it with the 3D scanning technologies and on-site surveying described later. The more up-to-date and accurate the ledger is, the greater the benefits achieved from AR display in subsequent processes. First, take inventory of materials lying dormant within the company and clearly grasp the asset information that should be 'visualized'—this is the first step toward success.

Step 2: Unifying Coordinate Systems and Setting Reference Points

Once ledger data have been digitized, the coordinate system is adjusted. This involves aligning buried pipe data with real-world geodetic coordinates. To accurately overlay a virtual model in AR, the pipeline positions in the data must match the actual geographic coordinates. However, older drawings and CAD data created independently do not always conform to public survey coordinate systems. For example, old water main drawings may have been drawn to local references such as “east from the XX intersection by ○ m (○ ft),” or recorded in region-specific coordinate systems (such as the old Japanese geodetic system). Therefore, it is necessary to transfer the data onto a unified spatial coordinate framework.

First, check which coordinate system your own buried pipe data is managed in. In recent municipal GIS and private management systems, it may be standardized to a plane rectangular coordinate system or latitude/longitude based on a geodetic datum (such as JGD2011), but be cautious with older data. If the data are recorded in a different geodetic datum, convert them to the latest coordinate system using transformation parameters provided by the Geospatial Information Authority of Japan. Also, if CAD drawings, etc., use arbitrary local coordinates (an arbitrary origin or orientation), perform georeferencing to real-world space by using known points on site.

Specifically, if reference marks shown on the buried pipe drawings (for example, manhole covers or fire hydrant locations) exist on site, measure their positions with high-precision GNSS or a total station, and compare the obtained actual coordinates with the coordinates on the drawings. By aligning using multiple control points, you can fit the entire drawing to the real-world coordinate system by translating, rotating, and scaling it. If point correspondences are difficult, you can also overlay shapes such as curb lines or building outlines. The important thing is to provide the buried pipe location information in a public coordinate system (global coordinates).

Also confirm the vertical reference. If there are data on buried depth, clarify and standardize the reference elevation (for example, whether it is described as a depth of ○ m (○ ft) from the road surface, or an elevation above the Tokyo Bay mean sea level). For example, even if you only have depth information from the ground surface, if you know the ground surface elevation you can convert it to the elevation of the pipe. If possible, it is good to measure the elevations of major manhole tops based on public survey benchmarks. By managing both horizontal and vertical directions in a unified coordinate system in this way, subsequent AR displays will be able to accurately indicate information such as "buried ○ m (○ ft) below the ground surface."

The process of unifying coordinate systems is unglamorous but critically important. If you neglect it, data loaded into AR can become misaligned with actual positions, undermining reliability. Conversely, when data are properly coordinate-aligned, you no longer need to rely on alignment markers in later steps, enabling smooth use of AR on site. If a municipality has already implemented a GIS based on the public coordinate system, this step is relatively straightforward, but even if not, it is worthwhile to review coordinates now as part of preparing future asset information.

Step 3: Selecting an AR System and Preparing Equipment

Once the data preparation is complete, you can finally begin preparing the AR system and the equipment to be used. There are several options for AR platforms used to visualize buried pipes, but in recent years methods that make use of smartphones and tablets without special dedicated equipment have attracted attention. Traditional solutions using AR glasses or dedicated surveying instruments have existed, but they were often expensive and difficult to operate. In that respect, using smart devices is simple and highly versatile, making it easier for field personnel to use on a day-to-day basis.

First, you should decide which device to use. The latest iPhones and iPads are equipped with AR display functions (camera, IMU, LiDAR) and have high processing power, making them strong candidates. On the other hand, there are AR-capable Android devices, but particularly in terms of 3D scanning accuracy, iOS devices (LiDAR-equipped models) are often superior at present. In any case, for on-site use a reasonably large screen with a bright display is easier to view, so having a tablet-sized device is advisable. However, because holding it in one hand while working can be burdensome, using a smartphone and a tablet interchangeably depending on the task is also an option.

Next, prepare a high-precision GNSS receiver. Up to Step 2 you aligned the data with the real-world coordinate system, but to make use of that result, the device used in the field must be able to determine its position with high accuracy. Because a smartphone’s built-in GPS alone only provides coarse accuracy on the order of several meters (several ft), it is insufficient for aligning buried pipes. Therefore, use a smartphone-mounted RTK-GNSS receiver that has appeared in recent years. This is a small, lightweight external GPS antenna that attaches to the back of a smartphone and enables centimeter-level positioning (inch-level positioning) using RTK. For example, if you attach a slim receiver to a smartphone like a case and receive correction information (network RTK services, etc.) via a dedicated app, high-precision positioning that previously required specialized equipment can be realized in the palm of your hand.

When selecting a GNSS receiver, verify the supported positioning methods and augmentation signals. For domestic use, consider connection to network RTK services such as VRS, and, to prepare for cases where mobile communications do not reach mountainous areas, also consider the use of satellite-delivered augmentation signals. Recent high-precision GNSS devices support multiple frequencies and have advanced multipath mitigation in urban areas, with design features to enable stable positioning according to the environment. Battery runtime and dust- and water-resistance are also important points for field use. In any case, securing a means to measure device position with centimeter-level accuracy (half-inch accuracy) is the key to this step.

Finally, prepare an application environment for AR display. Hardware-wise, a smartphone + GNSS is sufficient, but software to actually display buried pipe data is required. Options include using commercial AR-capable surveying apps or GIS viewers, or developing a custom app tailored to your company’s needs. The former enables faster deployment, while the latter allows for finer-grained feature implementation. What’s important is that the system can load the pre-prepared buried pipe data and reflect positioning information obtained from an external GNSS in the AR. For example, check whether you can import a pre-created pipe model into the app and place it with coordinates, and whether you can anchor the virtual model based on the GNSS-derived current position and orientation. Prepare both the hardware and the software, and it’s a good idea to try a small-scale demo display at this stage.

Step 4: 3D Modeling of Buried Pipe Data and Integration with AR Content

Next is the step of finalizing the prepared buried pipe data as AR display content. You can display information at hand—such as plan-view line data or point-cloud data—directly in AR, but to make it easier to grasp intuitively on site, we apply 3D modeling and visualization techniques.

The first thing to consider is 3D modeling of buried pipes. If the pipeline route and depth information have already been digitized in steps 1 and 2, you can use them to create simple cylindrical models or band-shaped 3D lines. By drawing a virtual pipe sized to the pipe’s diameter, you can better visualize its presence underground. For the vertical direction as well, if you have coordinate values, position the model underground using those values. For example, if the water main is at a depth of 1.2 m (3.9 ft) below the road surface, set the model so it runs beneath the road surface at that depth. If depth information is scattered, interpolate between the points to create a smooth 3D line.

On the other hand, in cases where point cloud data is acquired during new construction, you can also generate a model from the point cloud. For example, if you scan pipelines with a smartphone + LiDAR during construction, you can extract only the piping sections from that point cloud and convert them into polygon meshes. This produces a realistic 3D model that captures the bends and the shapes of connection parts, allowing you to confirm shapes virtually identical to the real object when displayed in AR in the future.

Next, set attribute information and display styles. Make sure that by simply looking at the virtual piping displayed in AR, users can determine what kind of pipe it is and its scale. Color-coding by industry is an effective method. For example, color potable water (drinking water) light blue, sewage brown, gas yellow, power red, and communications green, following the colors used in typical piping diagrams. This allows pipes belonging to different operators running in parallel to be distinguished at a glance. Additionally, add labels and annotations as needed. Some AR apps can display information tags at specific points, so you can display text such as "burial depth 1.2 m (3.9 ft)" and "200 mm (7.87 in) ductile iron pipe (laid 1975)" on the pipes. Because too much information can become hard to view on site, make it possible to toggle display on and off or to limit tagging to high-priority information.

We will also establish the data-sharing mechanism at this stage. We will create a system to store and share data in the cloud so that multiple personnel can view the same buried pipe model on their respective devices. For example, 3D model data will be uploaded to a dedicated cloud or an internal server, and on site the workflow will be to download it to devices and display it in AR. This will enable the latest data obtained in the field to be checked immediately on office PCs, and conversely allow models prepared at the desk in advance to be called up on site. Data will be centrally managed to remain up to date at all times, and change histories and metadata (creation date, creator, data source, etc.) will also be recorded.

Once this step is completed, the "content to be shown in AR" will be almost finished. In other words, you will have the digital 3D model that represents what is buried where underground, along with its display style and associated information. All that remains is to display this correctly at the actual site, but before that it is reassuring to perform a small-scale verification to check for any issues in the integration between the model data and the app.

Step 5: On-site AR Display Testing and Operational Training

Before full-scale deployment, conduct on-site AR display configuration and testing. This is the stage to actually use the AR system within a limited area to verify accuracy and usability. When using it on-site for the first time, it is essential not to begin large-scale operations immediately but to run a trial in a small area to identify any issues.

First, select the test field. Ideally, testing in a relatively complex location where multiple buried utilities intersect makes the effects easier to see, but at the outset, choose a calm location where major construction is not taking place for safety reasons. For example, an area within premises that site managers can easily access, or a roadside space with low traffic. If you can reasonably identify known buried utilities at the site, it will be easier to compare and verify the AR display results.

When you arrive on site, first check the GNSS positioning environment. High-precision positioning via RTK tends to be more stable in locations with an open view of the sky, but in areas such as streets lined with tall buildings or under trees, satellite signals may be blocked or multipath may occur. If necessary, re-acquire correction information or move slightly to perform positioning at a spot where satellites can be more easily acquired. Within tens of seconds to a few minutes, a "FIX solution (fixed solution)" will be obtained on the device, and when cm level accuracy (half-inch accuracy) is secured, preparation is complete.

Next, launch the AR app and perform the initial adjustment of the model display. The high-precision GNSS should have the position and elevation roughly correct, but as a precaution compare the site’s landmarks with the virtual model’s position. For example, check whether the virtual piping corresponding to manhole covers exposed on the ground appears directly beneath them, and whether the relative sense of distance between the ground surface and the buried-pipe model feels natural. If you notice a slight discrepancy, use the app’s fine-tuning function to offset the entire model east, west, north, south, up, or down until it visually aligns.

If the display is satisfactory, we will proceed directly to trial operation. We will give stakeholders smartphones and tablets and have them actually view the underground piping through AR. While walking around the site, we will share the screen and confirm things such as "There is one water pipe directly beneath here" and "A gas pipe runs parallel further in." If participants raise operational questions or requests, we will interview them on the spot and record them. For example, if someone says "The screen is hard to see outdoors," we might consider a sunshade hood, or if someone comments "The label text is small," we might consider adjusting the font size.

Also, during this trial phase we will demonstrate its usefulness in assumed scenarios. For example, assuming a scenario of confirming buried locations before excavation work, we will try spraying marks on the ground with marking spray while viewing the AR display. We will compare how much AR can improve the efficiency and accuracy of the traditional process of measuring dimensions on drawings and then marking. Training of personnel will also be conducted in parallel at this stage. Since many technicians will likely be handling AR equipment on site for the first time, they will learn how to operate it through hands-on use. After such a trial operation period, once system reliability and user proficiency have been achieved, we will proceed to full-scale deployment.

Step 6: Full-Scale Operation and Deployment of AR in On-site Operations

In the final step, integrate AR visualization of buried pipes into daily maintenance and management operations. Incorporate the feedback obtained from testing, and if issues have been resolved, expand the target areas and use cases. The goal is for on-site AR displays to become established as part of the normal workflow, not a special event.

Prior to full-scale operation, we will first organize our internal systems. We will create a simple written manual documenting procedures for using AR and circulate it to relevant departments. For example, we will set rules such as "always confirm the location of buried objects with AR before excavation work" and "record inspection results by annotating screenshots of the AR screen." We will also equip field teams with the necessary devices (tablets, GNSS receivers, mobile batteries, etc.) and ensure they are in a state that anyone can use. To ensure operations continue even when personnel change, we will promote skill transfer through regular training and on-the-job training (OJT).

In pre-excavation safety checks, just before roadwork or pipe repair, the construction crew reconfirms underground pipe locations and depths using AR. This eliminates the need to compare drawings with the site and guess, allowing even workers visiting the site for the first time to identify hazardous areas at a glance. Briefing heavy equipment operators is also far more persuasive when done while showing the AR display.

In recording buried-pipe construction, for new piping installations, an AR system is used to verify and document the final form of the pipe before the road surface is temporarily reinstated after burial. For example, by overlaying a virtual pipe model and the actual piping (still exposed) on a smartphone screen and taking photos, you can reliably preserve the as-built condition at that location as evidence.

AR also demonstrates its power in maintenance and inspection. For example, when planning the replacement of aging pipes, you can view current 3D data while checking the extent of deterioration and repair history. Rather than flipping through paper documents and imagining the past, overlaying the data directly on site leads to more accurate judgments. Parts of the work that used to rely on veteran intuition become less person-dependent, allowing anyone to conduct highly accurate inspections.

In situations where stakeholders need to share information, AR visualizations become a common language on site. For example, in road construction multiple buried-utility operators—such as water, gas, and communications—are involved; if each party’s piping data is integrated and displayed collectively through AR, everyone at a joint on‑site meeting can share the same view of the underground conditions. Also, when explaining to clients or nearby residents, showing them through a smartphone or tablet that “this many pipes run under this road” makes understanding and consensus-building proceed smoothly.

Once operations are on track like this, the digitalization cycle for buried-pipe management is complete. Because surveying and construction records, data accumulation, and on-site utilization all operate digitally and seamlessly, information does not degrade over time and maintains its accuracy. By preserving the detailed 3D information that paper ledgers could not reproduce, it also helps streamline future planning. If the locations and shapes of buried pipes are recorded in detail, they can be accurately identified with AR when excavated during separate works years later, leading to safe, secure construction with zero accidental excavations.

Finally, the introduction of such AR contributes to promoting DX (digital transformation) across the entire industry. It is an initiative that aligns with the Ministry of Land, Infrastructure, Transport and Tourism’s i-Construction, enabling advanced, data-driven process management from surveying through construction to maintenance. It is also expected to serve as a solution to chronic labor shortages and the problem of skills transfer, and is attracting attention as a measure that can simultaneously improve on-site productivity and enhance safety.

The key to successfully visualizing buried pipes in AR is high-precision positioning information and accurate data management. By steadily following the steps described so far, an era is close at hand in which anyone can intuitively visualize underground infrastructure. For example, by using LRTK, a high-precision GNSS positioning device that can be attached to an iPhone, centimeter-level positioning and AR display can be achieved with just a smartphone. With tools like LRTK, even without specialized surveying knowledge, you can pick up a device and literally “see through” to accurately locate buried pipes. This technology, combining high-precision GNSS and smartphone AR, will greatly transform future infrastructure management. Please consider adopting AR technology as a first step toward visualizing the “invisible world” beneath your feet on-site and realizing safe, efficient maintenance and management.