Table of Contents

• Introduction

• Challenges of Underground Utilities and Construction Errors

• What It Means to Visualize Underground Utilities with AR

• Why AR Visualization Can Prevent Construction Errors

• Improving Inspection Accuracy Using AR

• Points to Keep in Mind When Introducing AR

• Easier AR Use with Simple Surveying Using LRTK

• FAQ

Introduction

Various infrastructure facilities are buried beneath the ground at construction sites. Water pipes, sewer pipes, gas pipes, power cables, communication cables—lifelines that support our daily lives—are spread underground. If such underground utilities are accidentally damaged during excavation or piling work, there is a risk of serious accidents such as explosions or fires from gas leaks, water outages or power outages, and large-scale communication failures. In fact, more than 100 incidents of underground utility damage are reported domestically each year, so ensuring safety and preventing construction errors are important issues.

To prevent accidents caused by underground utilities, it is essential to accurately understand in advance what is buried under the work area and where. But because the underground is not visible, traditionally the only option has been to rely on drawings and records of burial locations. Old drawings may have shifted positions, or pipes that haven’t been updated may exist. Methods using metal detectors or radar surveys can also be used to examine buried objects, but they require specialized equipment and effort, and they cannot find everything with 100% certainty. On site, workers can only dig cautiously while guessing “the gas pipe should be around here,” and less experienced workers are at higher risk of mistakes.

What has attracted attention in recent years is the “visualization” of underground utilities using AR (augmented reality) technology. AR is a technology that overlays CG information on the camera view of a smartphone or tablet. With AR, the positions of pipes and cables hidden underground and not directly visible can be displayed on the device screen as if viewing through the ground. For example, when a worker holds up a smartphone, the water pipe buried under the road might appear as a blue line. By making the invisible “visible,” it becomes easier to plan safe construction that avoids underground utilities, and heavy equipment operators and workers can work with greater confidence. Also, for post-completion infrastructure inspections, if the underground facility locations can be confirmed with AR displays, checks can be done more efficiently. The use of AR technology is expected to prevent construction errors and improve inspection accuracy, providing reassurance for all stakeholders. This article explains in detail how AR visualizes underground utilities, the benefits, and points to consider when introducing it. At the end of the article, we also introduce a method using a new technology called “LRTK” that enables anyone to perform high-accuracy surveying easily.

Challenges of Underground Utilities and Construction Errors

To prevent accidents caused by underground utilities, it is necessary to identify burial locations before starting work and to ensure clear on-site warnings. In practice, drawings of buried pipes and cables are obtained from relevant parties in advance, and the ground at the work site is commonly marked with spray paint indicating “gas pipe here,” etc. If necessary, test excavations (carefully digging in advance to confirm) or detector surveys are also conducted. However, the accuracy and update status of drawings vary, markings may be slightly off, and there may be buried utilities not shown on drawings. Even with thorough investigations, human error cannot be completely eliminated.

Against this backdrop, major accidents involving underground utilities continue to occur. In the 1980s, more than 300 accidents occurred annually, but after strengthened countermeasures the number temporarily fell below 100. Still, in recent years the number has remained around 150–200 per year, so on-site risk remains high. For example, if a gas pipe is accidentally damaged, the surrounding area is exposed to danger and work is halted, and enormous effort and cost are required for restoration and compensation. For contractors it can lead to loss of trust, and for clients and managers it is a serious problem. Underground utilities and construction errors remain major issues that must be solved.

The main challenges can be summarized as follows:

• Invisible buried utilities: It is not intuitive what is buried underground, making it difficult for workers to visualize locations.

• Variability in information accuracy: If drawings or ledgers are old or inaccurate, discrepancies with actual burial locations occur.

• Burden of preliminary surveys: Pre-excavation utility surveys and marking work take time and effort, placing a large burden on the site.

• Human error: It is difficult to completely eliminate human errors such as overlooking drawings, marking mistakes, or misunderstandings.

• Impact in case of accidents: If a buried utility is damaged, it leads not only to safety hazards but also to delays in schedules, financial losses, and a decline in social trust.

What It Means to Visualize Underground Utilities with AR

So what exactly does it mean to “visualize” underground utilities using AR technology? Simply put, it means overlaying digital information that indicates the positions of pipes and cables buried underground onto the camera view of a smartphone or tablet. It’s as if you are seeing through the ground—the buried utilities appear on the screen. At this time, the ground itself is not actually being seen; the display is CG based on pre-prepared positional data that says “this is what’s here.” However, from the user’s perspective, it feels almost the same as being able to directly confirm the underground situation on site.

There are three major elements required to realize AR visualization of underground utilities.

• Buried utility position data: This is the information that serves as the source for visualization. Prepare data that shows the routes and depths of water pipes and cables in advance. Existing burial drawings, GIS data, and BIM/CIM models can be used, and for new installations 3D data is created at the design stage.

• High-precision positioning: A mechanism to accurately determine the current position and orientation of the AR-capable device itself. Outdoors, GPS or GNSS (satellite positioning) are used, but ordinary GPS has errors on the order of meters, so methods such as RTK (real-time kinematic) are used to ensure centimeter-level positioning accuracy (cm level accuracy (half-inch accuracy)). In some cases, manual alignment referencing known points on site may be performed.

• AR-capable devices and apps: Devices such as smartphones and tablets that can display AR and an application to display buried utility data. In recent years, AR features (camera, gyros, LiDAR sensors, etc.) in commercial mobile devices have become more complete, so AR can be used on site without dedicated expensive equipment.

With these elements in place, actual use is simple. First, load the buried utility data into the device’s app and determine the device’s current position. Then, against the real-world scene captured by the camera, the pipes and structures underground are displayed as virtual 3D objects or lines. For example, “gas pipe at a depth of 1 m (3.3 ft)” or “power cable from here to here” is drawn on the screen, and workers can adjust their work positions or dig more carefully while watching it. Because the AR display of buried utilities updates in real time according to viewpoint, positional relationships can be understood from any angle without having to mentally reconstruct the drawings in three dimensions. AR visualization of underground utilities fills the information gap on site, enabling more intuitive and reliable construction decisions.

Why AR Visualization Can Prevent Construction Errors

Visualizing underground utilities with AR directly contributes to preventing various mistakes during construction. Human intuition derived from what we can “see” in reality is extremely important. Compared to imagining pipe positions from drawings, seeing blue or red lines in place via AR allows anyone to accurately grasp positional relationships. Specifically, here are the main reasons AR leads to reductions in construction errors.

• Eliminates misreading of drawings: AR addresses human errors such as excavating after missing a drawing or burial marker. Because the actual-size pipe positions are shown in AR, workers can intuitively understand the safe work area without constantly checking paper drawings. Mistakes like misreading the drawing scale or misunderstanding on-site positions become less likely.

• Allows preemptive avoidance of interference with buried utilities: AR visualizes the positional relationship between existing buried utilities and structures to be constructed. For example, if another pipe runs under the planned excavation area, you can immediately notice it on the AR screen. Because interference risks can be detected before construction and design or construction methods can be modified, scenarios such as “we dug and found a pipe and had to stop work” can be prevented.

• Ensures everyone on site shares the same awareness: Information displayed in AR can be shared by all stakeholders present. Precautions that used to exist only in the minds of veterans become visible to everyone, including newcomers, via AR displays. Discrepancies like “I didn’t hear about that” or “I wasn’t told” are reduced, making it easier for the whole team to align on preventing mistakes.

• Real-time feedback: Because the location of buried utilities can be constantly checked with AR as work progresses, you immediately notice if you approach a danger zone. If an excavator operator monitors buried pipe positions through a tablet from the cab while digging, much finer and safer adjustments are possible than before. Real-time feedback allows work to proceed while avoiding risks at each step.

In this way, AR enables the adage “seeing is believing” on site. As a result, human errors are greatly reduced, and mistakes such as pipe damage or rework due to construction defects can be prevented in advance.

Improving Inspection Accuracy Using AR

AR is extremely powerful not only during construction but also for post-completion infrastructure inspections and maintenance. Because underground utilities are normally invisible, traditional inspections often involved matching drawings on site and probing around thinking “there should be a pipe around here.” With AR visualization, inspectors can accurately determine the position of buried utilities from above ground, enabling efficient and reliable inspections.

For example, during routine inspection of aging pipes, displaying the water pipe route with AR while searching for leak points allows anomalies to be found efficiently. Tasks that previously relied on listening rods or metal detectors and probing by feel can now be concentrated according to AR guidance. Also, when locating buried valves or shut-off valves, visualizing approximate positions with AR can minimize the amount of digging required.

AR is also useful for post-construction as-built inspections. By overlaying pre-construction design data with the actual structures in AR, you can verify on-site whether installation matches the design. If the position or elevation of a buried pipe deviates from the design, the discrepancy is immediately apparent in the AR display. This enables inspections that used to be performed after returning with photos and survey data to be performed in real time on site.

Moreover, the ability to record and share the visual information obtained via AR contributes to improved accuracy. If an inspector photographs and saves the AR screen they are viewing, the record includes the visualized underground pipe positions that do not appear in regular photos. When reviewing later in the office, the situation can be reproduced more accurately than with mere notes or drawings, improving the precision of reporting materials. When sharing information among stakeholders, AR images or videos reduce the likelihood of miscommunication due to differing interpretations.

Thus, AR supports inspection tasks in every detail and enables comprehensive and reliable checks. As a result, the reliability of infrastructure maintenance improves, contributing to earlier detection and response to problems. Improved inspection accuracy also contributes to longer infrastructure lifespans and reduced maintenance costs.

Points to Keep in Mind When Introducing AR

While AR visualization offers great benefits, there are several points to be aware of when introducing it on site. To make the most of the technology, consider the following.

• Accuracy management of buried utility data: If the data driving AR displays is inaccurate, the whole effort is counterproductive. If only old drawings exist, resurvey them in advance to provide the most accurate positional information possible. If new buried utilities are discovered during construction, reflect them in the data for use in future projects.

• Ensuring positioning accuracy: GNSS-based positioning is key to AR use. Large errors can result in misaligned displays that create danger. Where possible, use RTK-compatible receivers, utilize correction information services, or perform calibration (on-site adjustment) using known points to maximize positional accuracy. In environments where GNSS is unstable, such as among tall buildings, consider using ground-installed target markers for alignment.

• Selection of devices and apps: Choose on-site devices with consideration for dust and water resistance and screen visibility. Consider high-brightness tablets whose screens are readable under direct sunlight outdoors or hands-free smart glasses, depending on the use case. For the AR app, confirm that it supports the data formats you need and that Japanese-language display and support are available.

• Training for site staff: Effective on-site use of new technology requires familiarity. Provide operational training at introduction and have staff become accustomed through AR rehearsals and small-scale trials. Although AR is intuitive, initial confusion can occur. By incorporating field feedback into rules and procedures, adoption will proceed smoothly.

• Compatibility with existing processes: AR is a support tool and should complement existing safety measures and construction management processes. For example, even if you confirm with AR, continue to use test excavations near important buried utilities and parallel checks with paper drawings. Do not over-rely on AR; leverage traditional knowledge as well to realize more robust safety management.

• Cost-effectiveness assessment: Carefully consider introduction costs and expected benefits. AR-capable devices have become affordable, and software is increasingly available as low-cost cloud services. Introduce AR in a way that matches the site scale and frequency of use. Start with pilot projects to verify effects before broad deployment to avoid unnecessary investment.

With these points in mind, AR technology can be smoothly integrated into the field and its benefits maximized. With appropriate preparation and operation, AR visualization of underground utilities will become the new norm at construction sites.

Easier AR Use with Simple Surveying Using LRTK

Finally, as a technology that makes AR visualization of underground utilities even easier, we introduce “LRTK.” LRTK (pronounced “el-ar-tee-kay”) is a pocket-sized surveying device that can be used by attaching a small high-precision GNSS receiver to a smartphone. Its biggest feature is that anyone on site can perform centimeter-level positioning on their own (cm level accuracy (half-inch accuracy)) without specialized training or large equipment.

Traditionally, obtaining accurate positions of buried utilities required surveying with instruments such as total stations. But with LRTK, you can point a smartphone, press a button, and measure and record coordinates of buried utilities on the spot. For example, after burying a pipe you can measure several points with LRTK to precisely digitize the pipe route. By immediately sharing that data to the cloud and importing it into an AR app, the pipe can be visualized in the correct position from the moment construction is completed. LRTK lowers the barriers to surveying work, dramatically streamlining the data preparation needed for AR use.

LRTK also considers integration with AR beyond simple position measurement. If you place a virtual object at coordinates obtained with LRTK in an AR app on your phone, you can visualize stake locations or burial routes on the spot. LRTK is truly a bridge connecting measuring (reality) and showing (virtual).

By utilizing such simple surveying tools, high-precision data acquisition that previously relied entirely on survey professionals can be conducted by on-site personnel. As a result, digital construction including AR visualization of underground utilities will become increasingly accessible. LRTK is a powerful ally supporting the AR-driven construction revolution. By wisely incorporating cutting-edge technologies, we can realize safer and more efficient construction sites.

FAQ

Q: Can AR really show what’s under the ground? A: AR does not directly image reality like an X-ray fluoroscope. It displays virtual overlays based on position data obtained in advance. However, if the data is accurate, it can feel as if you are seeing through the ground. In short, AR is a technology that “shows” rather than “sees,” but in practice it sufficiently visualizes the underground for on-site use.

Q: Do I need special equipment or expertise to use AR? A: All you need are an AR-capable smartphone or tablet, a compatible app, and the buried utility data. Many modern smartphones have built-in AR capabilities, so you can start without expensive dedicated equipment. If you want higher accuracy, connecting a GNSS receiver to your phone enables centimeter-level positioning (cm level accuracy (half-inch accuracy)). Operation is intuitive—simply point the camera—so advanced IT skills are not required. With brief training, site staff can use it effectively.

Q: How do you prepare position information for underground utilities? A: For existing infrastructure, the first step is to obtain piping and burial drawings from relevant organizations. Since old drawings can be inaccurate, verify actual positions with ground-penetrating radar surveys or test excavations as needed and correct the data. For new construction, create 3D information of buried utilities during the design stage. Using a simple surveying system like LRTK to measure on site and obtain high-precision coordinates is advisable. Once digitized, manage positional information in a GIS or the cloud to keep it up to date.

Q: How much does it cost to introduce AR? A: Costs vary by scale and method, but it is much more affordable now than before. Dedicated AR equipment used to be expensive, but leveraging commercial smartphones and tablets reduces hardware costs. Even when adding GNSS receivers, more affordable options than traditional surveying equipment are available. Software is often offered as subscription services at accessible price points. Considering the costs avoided by preventing construction errors and improving efficiency (rework, accident response, etc.), the return on investment can be substantial.

Q: What is LRTK? A: LRTK is the name of a GNSS solution that turns a smartphone into a high-precision surveying instrument. It consists of a small pocket-sized device and a dedicated app, enabling anyone to easily obtain centimeter-level position information (cm level accuracy (half-inch accuracy)). It is an easier-to-use adaptation of conventional RTK-GNSS technology, allowing not only on-site surveying but immediate cloud sharing of acquired data and use in AR displays. It is attracting attention as a tool to streamline location setting for buried utilities and as-built management.