3D Recording of Underground Buried Pipes with a Smartphone: Anyone Can Confirm Positions Before Excavation for Safe Construction

At construction sites, heavy machinery accidentally hitting underground buried pipes—such excavation accident poses a major risk to workers’ safety and the surrounding community. Damaging underground infrastructure such as gas pipes, water pipes, or communication cables can affect not only the site but also a wide area, causing extensive restoration work and social losses. This article reviews the background and conventional challenges of excavation accidents caused by underground buried pipes, and introduces a groundbreaking 3D recording and position verification method using the latest smartphone technologies (high-precision GNSS and AR). From a field perspective, we explain key points to allow anyone to easily confirm the location of buried pipes on site and achieve safe and efficient construction.

Background and Risks of Excavation Accidents Caused by Underground Buried Pipes

When digging roads or lots, accidents in which buried pipes or cables are accidentally damaged continue to occur. Especially in urban areas with many aging infrastructures and with increasing renovation works, damage accidents to buried pipes have been on the rise in recent years. Once an accident occurs, it can develop into a “public disaster” that affects not only construction personnel but also third parties in the surrounding area.

Specific risks caused by damage to buried utilities include the following:

• Damage to gas pipes: Gas leaks can cause fires or explosions, which may have serious impacts on nearby buildings and human life.

• Breakage of water pipes: Large-scale leaks can lead to water outages, disrupting the lives of local residents. Roads may become flooded and restoration work tends to be prolonged.

• Damage to sewer pipes: Leakage of sewage can cause soil contamination and odor problems, creating environmental and sanitary issues.

• Cutting of power and communication cables: Power outages and communication failures may occur, disrupting households, businesses, and social infrastructure such as traffic signals.

Such accidents, once they occur, lead to project delays and huge restoration costs, resulting in significant losses for contractors. For safety management, “not damaging buried objects” is an absolute requirement for excavation work, but in reality there are many moments where work relies on past drawings or experience and causes near-miss situations. The Ministry of Land, Infrastructure, Transport and Tourism also requires thorough pre-investigation and trial excavation of buried objects to prevent accidents, but on-site constraints make it difficult to achieve perfection.

Conventional Records of Buried Pipes and Their Limitations

To prevent accidents caused by buried pipes, it has been common practice to confirm the positions of buried objects before construction and to record their positions after construction. However, several limitations have been pointed out with conventional methods.

First, for pre-confirmation, it is common to rely on old paper buried-pipe drawings or ledgers. Drawings provided by municipal offices, water bureaus, etc., are referenced, but old drawings can be misaligned with actual pipe positions or may not reflect update works. Also, management entities or stakeholders of buried objects may have changed, making the drawings themselves difficult to obtain. As a result, drawings alone are insufficient, and there were cases where excavation had to proceed relying on the intuition of experienced workers.

There are also issues with methods of recording during and after construction. For example, conventionally positions of buried pipes were measured with tape measures or surveying instruments before backfilling, and records were left by sketching on paper or later creating drawings in CAD. However, this method is time-consuming and accuracy tends to depend on the person. Dimensions hastily noted at the site can be ambiguous, and if records remain only within the company and are not shared with other contractors, the records cannot be utilized for future work. There are also cases where temporary markings such as spray paint or chalk are drawn on temporarily restored road surfaces as markers for buried positions, but temporary markings fade over time and do not become permanent information.

Furthermore, personalization of buried-pipe information was a major problem. Even if veteran site supervisors or workers know “a pipe should be around here” in their heads, relying on individual experience cannot be called organizational safety management. In wide excavation areas, it is difficult to judge where to focus trial excavations, and there have been many cases where a pipe that was not on the drawings was found after checking drawings and visually inspecting the site. With conventional methods, it was difficult to accurately and long-term share location information of buried pipes, and as a result the risk of “you won’t know until you dig” persisted.

Emergence of a New Recording and Verification Method Using Smartphones, GNSS, and AR

In recent years, a new approach combining smartphones, high-precision GNSS, and AR (augmented reality) has emerged to solve these issues. Ordinary smartphones are evolving into powerful tools for recording and confirming buried pipe positions on site.

The key is to use a high-precision GNSS receiver attachable to a smartphone (RTK-GNSS compatible) and the smartphone’s built-in 3D scanning capabilities (LiDAR sensor or photogrammetry). With RTK (Real Time Kinematic) technology, even a smartphone can obtain position coordinates with an error of a few centimeters. This accuracy makes it possible to accurately measure the positions and depths of narrow pipes like buried pipelines. Also, the latest smartphones are equipped with LiDAR sensors that capture space three-dimensionally and can scan surrounding structures as point cloud data (a collection of numerous 3D points).

In this new method, after burying the pipes, the pipe locations are scanned with a smartphone and recorded as 3D models. The surveying and drawing processes that were formerly laborious are handled almost automatically by the smartphone and dedicated apps. For example, if a smartphone is held up to photograph and scan the pipes during installation, the pipe shapes and depths can be obtained as high-precision 3D data. Notably, the acquired data is assigned geodetic coordinates (latitude/longitude, etc.) or absolute coordinates based on reference points. This links the buried-pipe data to exact positions on a map, eliminating concerns about losing their locations in the future.

Furthermore, combining with AR (augmented reality) technology transforms on-site position confirmation. When viewing the site through the smartphone camera, the 3D model of the buried pipe previously recorded is overlaid on the real landscape. It provides an experience akin to “seeing through the ground,” allowing intuitive understanding of the exact position and depth of the buried pipe. Because the AR display uses high-precision GNSS positioning, the model remains aligned without shifting even when walking around the site with the smartphone. No special AR goggles are required; the innovative aspect is that a single handheld smartphone can confirm what is buried at the site.

Mechanism of 3D Scanning of Underground Buried Pipes and Cloud Management with Position Coordinates

With smartphone-based 3D recording of buried pipes, it is not just about acquiring data on site; centralized cloud management is the key. Point cloud data and 3D models obtained by scanning on site are uploaded from the smartphone to cloud servers immediately. The cloud stores each pipe’s shape data linked with position coordinates, creating a digital archive accessible to authorized parties as needed.

The benefits of cloud management are in information sharing and multi-purpose utilization. For example, buried-pipe data recorded at one site can be viewed later by another construction manager from the office. On 3D data, one can measure pipe dimensions or check clearances between multiple pipes with a click. Also, mesh models (3D mesh models that represent shape with surfaces) can be automatically generated from the acquired point clouds and used like CAD drawings. Conventionally, confirming pipe depth required interpreting past records or re-excavating the site, but with accurate 3D models in the cloud, you can understand pipe positions and depths at your desk.

Of course, this data also becomes the basis for AR displays in future work. As long as the buried-pipe models stored in the cloud can be retrieved, position information can be taken out anytime, anywhere. Unlike paper drawings, there is no risk of deterioration or loss, and a semi-permanent, high-precision buried-pipe map accumulates. As accumulated data grows, everyone will be able to know “what buried objects are located where in this area,” contributing to DX (digital transformation) in infrastructure management.

On-Site AR Display Procedure for Pre-Excavation Safety Checks

How, then, is the actual procedure for conducting a pre-excavation safety check using buried-pipe data? Below is an example flow of recording buried pipes with a smartphone in advance and then confirming their positions by AR display during subsequent construction.

• Preparation of buried-pipe data: First, when the target buried pipe is installed, scan it in 3D with a smartphone and save the pipe’s position and shape data to the cloud. Scanning before the pipe is fully backfilled—while the top of the pipe is still exposed—ensures accurate position recording even after it is completely buried.

• Retrieve data on site: On the day of excavation, workers launch a dedicated smartphone app on site. From the app, they access the buried-pipe database in the cloud and download past buried-pipe data corresponding to the target area. Attach a high-precision GNSS receiver to the smartphone so that the current position can be determined to the centimeter level (half-inch accuracy).

• 透視 display in AR mode: Switch the app display to AR mode and the smartphone camera will show the actual site view. Then overlay the previously acquired 3D model of the buried pipe in AR. On the smartphone screen a semi-transparent pipe model is rendered under the ground, allowing confirmation as if seeing through the ground. For example, it becomes obvious at a glance that “a gas pipe runs diagonally from the road center” or “a water pipe is buried at around a depth of 1.5 m (4.9 ft).”

• Fine adjustment and verification of position: Normally, the model is displayed in an almost correct position by GNSS-based alignment, but as a precaution verify there is no error by overlaying known structures (manhole positions or existing exposed parts). Walk around the site with the smartphone and check the relationship between the virtual pipe on the screen and ground landmarks. Thanks to high-precision positioning, the pipe model in the display follows with almost no shift from the actual pipe position, minimizing the need for fine adjustments.

• Safe excavation planning: Once the buried-pipe positions are understood, adjust excavation plans accordingly. Share with site supervisors and heavy equipment operators and implement specific safety measures, such as “hand-dig here down to this depth because pipes are present” or “beyond this line there are no pipes, so backhoe excavation can proceed.” If necessary, mark the ground with chalk or share screenshots of the AR display as safety notices.

By following these steps, workers can reliably grasp buried pipe locations before excavation, which were previously difficult to determine in advance. What used to be done by veteran intuition—“it’s probably around here”—can now be visualized on a smartphone screen. This enables everyone on site to share the same information and dramatically reduces the risk of damage to buried pipes.

Flexible Operation with Screen Guidance for Anyone and Role Division with Experienced Staff

A strength of the new smartphone-based system is its usability and operational flexibility. Although advanced technology might seem to require specialists, this system includes intuitive on-screen guidance that even general site workers can use. There are reports that workers using the system for the first time on site could operate the app without prior training. The smartphone app displays guidance such as “start scanning here” and “walk this area to capture,” so even those uncomfortable with machines can follow the steps without confusion.

Also, this system enables role division with experienced staff. For example, while recording buried pipes was previously left entirely to experienced surveyors, smartphone utilization allows younger or other trades’ workers to acquire data. This lets veterans focus on overall planning and data verification while other staff handle on-site surveying and recording, enabling efficient team operation. Because data is shared in the cloud, office-based engineers can check the data immediately after it is recorded on site and provide additional instructions if necessary. Remote expert support becomes easier, enabling more effective use of human resources.

Moreover, the system automatically checks for recording omissions or errors, reducing person-dependent variability. For example, scanned point cloud data is instantly converted into a 3D model, so any missing records can be detected on the spot. With manual notes and photos, one might later worry “was that pipe’s length recorded correctly?” but digital data eliminates such concerns. By enabling standardization independent of individuals, a consistent level of safety management can be realized at every site.

Value as a System Leading to Zero Accidents and Efficient Construction

The system for 3D recording and verification of buried-pipe positions using smartphones, GNSS, and AR is not just a high-tech gadget but delivers value directly linked to site safety and efficiency. One is its contribution to “zero accidents.” If the locations of buried pipes are known accurately in advance, the risk of accidentally damaging them is greatly reduced. Even thin cables that are easy to overlook can be noticed if recorded in the data, and situations where unexpected buried objects suddenly appear can be avoided. As a result, the safety of workers and nearby residents is protected, and the risk of third-party damages from construction is reduced.

Another value is construction efficiency. Previously, a large amount of time and manpower was allocated to pre-investigation, trial excavation, and record-keeping for buried pipes. The new system greatly simplifies these tasks. On-site scans are completed in a short time and become digital data immediately, so subsequent drawing production work is unnecessary. For future projects, there is no need to repeatedly perform trial excavations in the same locations for confirmation. Sharing cloud data among stakeholders reduces communication loss and prevents mistakes like “I wasn’t told” or “I didn’t know.”

Furthermore, this system can be considered a future asset. Once recorded, buried-pipe data is stored semi-permanently and can be used repeatedly in future infrastructure management or other construction. In government and public infrastructure sectors, a database that accurately shows what is buried under roads is valuable. As such data assets accumulate, ripple effects such as reduced maintenance costs and more advanced preventive maintenance are expected.

Finally, here is a concrete example of realizing the combination of smartphone RTK + point cloud recording + AR display on actual sites. For example, there is a system called [LRTK](https://www.lrtk.lefixea.com/lrtk-phone) that mounts a centimeter-class RTK-GNSS receiver on a smartphone to perform point cloud scanning and AR projection. By using LRTK, simply scanning buried pipes with a smartphone and uploading them to the cloud automatically records the pipe shapes and depths with absolute coordinates. Calling up that data on site and displaying it on a smartphone via AR makes safe construction that avoids underground pipes possible for anyone. On sites that introduced LRTK, it has been reported that even workers without special training could achieve high-precision recording and verification by following the app’s instructions, leading to zero incidents of buried-object damage.

In this way, the system of recording and utilizing buried-pipe locations in 3D with smartphones brings revolutionary improvements in both safety management and work efficiency from a field perspective. As adoption spreads, a society without excavation accidents caused by buried pipes—and routine smart construction based on data—will become a reality. To create sites where everyone can work safely and efficiently, we should actively adopt these latest technologies. Let’s update the field’s “common sense” with digital technology and realize safer, smarter construction.