Realizing “Visualization” on Construction Sites with AR: Hidden Risks Made Instantly Visible

Table of Contents

• Invisible risks lurking at civil engineering sites

• Visualization of the site using AR technology

• Technologies enabling markerless high-precision AR

• Examples of AR use in civil engineering

• Effects AR introduction brings to the site (safety improvement, efficiency, etc.)

• Closing: Simple surveying with LRTK

• FAQ

Even seemingly safe areas on civil engineering and construction sites often conceal hidden risks. For example, underground water and sewer pipes, gas lines, and power cables are not directly visible, so there is a danger of accidentally damaging them during excavation. There are also cases where serious accidents or rework occur due to problems that are difficult to detect with the naked eye, such as internal cracks or deterioration of structures, underground cavities, and discrepancies between as-built conditions and design drawings. How to manage these “invisible” elements and translate that into safe construction has long been a challenge for the civil engineering industry.

Traditionally, responses relied on the experience of veteran workers, paper drawings, and on-site marking (spray marking). However, human intuition and static drawings have limits, and in urban areas where complex underground structures intersect, it is not uncommon for the information on drawings to differ from actual site conditions. There are frequent near-miss reports where workers thought “there should be nothing here” only to uncover unexpected piping. In fact, domestic incidents of buried object damage occur on the order of several hundred cases annually (although they decreased to about 92 cases per year in 2012, they have been rising again and reached 168 cases in 2024), and they remain a factor threatening site safety. The question of how to make “things you can’t see” visible on site—one emerging solution attracting attention in recent years is AR (Augmented Reality).

Invisible risks lurking at civil engineering sites

What are the “invisible risks” that can pose latent dangers at construction sites? A primary example is lifeline facilities buried underground. When excavating roads or development sites, accidentally damaging underground water pipes, sewer pipes, gas lines, communication cables, or power lines can lead to large-scale leaks, gas leaks, or power outages. Damaging aged pipes in particular can cause significant secondary damage—gas pipes may risk explosions, and damaged sewer pipes may even lead to road collapses. Such accidents can escalate into construction delays and compensation issues, posing a serious headache for site managers.

Beyond underground utilities, there are invisible issues within structures or in construction processes. For instance, the placement of rebar or embedded piping inside concrete structures cannot be seen from the outside. During renovations or retrofits, opening walls or floors can reveal piping routed in positions different from the drawings. Also, because the final appearance cannot be understood until completion, failing to notice design errors or interferences (clashes with other equipment) during construction—i.e., mismatches between plan and reality—is another form of hidden risk. Furthermore, deterioration or cracks in structures may only be discovered through specialized inspections; missed inspections can jeopardize safety. In this way, civil engineering sites contain many types of information and conditions that are not visible, and these hidden factors greatly influence safety, quality, and efficiency.

Visualization of the site using AR technology

In recent years, AR (Augmented Reality) has been expected as a trump card for “making the invisible visible.” AR overlays CG or digital information onto the real-world view via a smartphone or tablet camera. When you view the site through a dedicated app, information that would normally be invisible appears on the screen as if it exists there. For example, if you point a camera at the ground of a road, the screen can render the positions of underground water pipes and cables so they appear transparent. Workers can intuitively understand “what is buried beneath their feet and how it is arranged” just by looking at a smartphone screen. This removes the need to mentally overlay paper drawings and enables on-site verification as if looking through the ground, greatly improving understanding and certainty.

Similarly, displaying a 3D model of a structure before completion in AR can project a life-size image of the final appearance onto the construction site. For example, at bridge or tunnel construction sites, superimposing the finished shape allows checks of whether elements will be positioned and sized according to the design. By working while viewing AR models, construction personnel can perform highly accurate work with the final shape in mind. AR is also useful for visualizing data that is hard for the human eye to perceive. For instance, overlaying inspection data or sensor information in AR can color-code areas of concrete deterioration or parts under stress. This enables rapid detection of hidden deterioration or anomalies and supports preventive maintenance.

Technologies enabling markerless high-precision AR

To realize site visualization with AR, it is extremely important to accurately align digital information with the real world. If alignment is off, virtual pipe models or design models displayed may not match real positions and could cause misrecognition leading to accidents. However, the accuracy of typical smartphone-built-in GPS has an error on the order of several meters (several ft), which is insufficient for the centimeter-level alignment (half-inch accuracy) required on construction sites. Older AR systems used markers (QR codes or special patterns) placed at each site and read by the camera to correct positioning. But placing and managing markers across large civil engineering sites is impractical. This led to the development of the latest technologies that enable markerless and high-precision AR display.

The key technology is high-precision positioning called RTK-GNSS. RTK (Real Time Kinematic) is a positioning method that reduces satellite positioning errors to below a few centimeters (below a few inches) by applying corrections from a ground reference station—shrinking GPS errors of several meters (several ft) down to centimeter-level or better. Traditionally, expensive surveying equipment was required, but recent miniaturization and cost reductions have produced palm-sized RTK-capable GNSS receivers that can be attached to smartphones or tablets. By pairing these with a smartphone on site, the device’s position can be known in real time with centimeter-level precision (half-inch accuracy), allowing virtual objects to be overlaid on real-world positions with almost no error.

In addition, modern smartphones include advanced AR platforms that recognize device orientation and position within space by tracking camera images and built-in sensors (accelerometers and gyros). High-end recent smartphones also incorporate laser ranging sensors called LiDAR, which can capture the surrounding environment as 3D point clouds in an instant. LiDAR can measure terrain and structural shapes and distances in real time, enabling virtual pipe models or structure models to blend naturally with real terrain for stable display and to present realistic occlusion (hiding virtual parts behind real objects). In short, the combination of smartphone + RTK + LiDAR enables high-precision AR displays without cumbersome marker placement.

By integrating these technologies into a system, accurate AR can be deployed over wide areas without per-site calibration. For example, with a 3D model containing buried pipe location data and an RTK-enabled smartphone, you can walk along a long road and instantly display a “see-through view.” Model alignment is done automatically based on GPS coordinates, and virtual objects appear in the correct positions simply by pointing the phone, making the system easy for anyone to use. The positional drift problem that had been a barrier to AR adoption has been overcome through technology, making practical AR solutions available for civil engineering.

Examples of AR use in civil engineering

How exactly can such AR technology be used on civil engineering sites? Here are some expected use cases.

• Safety checks by visualizing underground buried objects: Visualizing underground pipes and cables in AR allows identification of hidden danger areas before excavation. For example, displaying the routes of water, sewer, and gas pipes on a smartphone screen lets heavy equipment operators immediately recognize no-go zones. This significantly reduces the risk of accidentally damaging buried items and dramatically strengthens safety measures.

• Construction support with AR (pile driving, layout guidance, and on-site projection of design models): AR is powerful for surveying and layout tasks. Traditionally, site layout was done by transferring dimensions from drawings using surveying instruments, then driving piles or marking positions. With AR you can project lines and positions from design drawings directly onto the site, allowing workers to drive piles or mark locations by following on-screen guides for precise positioning. Displaying the 3D model of the planned structure at the site and walking around it is another usage. This makes it easier to spot discrepancies during construction, reducing rework and errors. AR can also be applied to as-built verification, for example by overlaying the completed structure with the design model and displaying deviations as a color distribution (heat map).

• AR for infrastructure inspection and maintenance: AR use is expanding in maintenance of infrastructure like bridges and tunnels. For example, when inspecting a structure, pointing a smartphone camera at it could highlight pre-measured crack locations or steel corrosion so inspectors can identify deterioration without overlooking it. For equipment maintenance, AR can highlight bolts that must never be left loose or pop up key steps from inspection manuals right on-site. The ideal is that anyone can intuitively find abnormalities and take appropriate actions without relying solely on expert experience. In the future, advanced applications such as overlaying 3D scan data obtained during inspections with historical records in AR to compare deterioration progress are also expected.

Effects AR introduction brings to the site (safety improvement, efficiency, etc.)

Visualizing the site with AR brings various benefits to civil construction and infrastructure management. Below are the main effects.

• Improved safety by preventing excavation accidents: Because hidden buried objects can be identified accurately in advance, the risk of pipe damage from erroneous excavation by heavy machinery can be greatly reduced. Sharing the locations of hazardous areas such as gas pipes or high-voltage lines before excavation raises overall safety awareness on site and helps prevent major accidents.

• Efficiency and labor savings in construction: AR eliminates the need to mentally map drawings to the site, saving effort in estimating positions. Being able to excavate, construct, or inspect only where necessary reduces unnecessary work, contributing to shorter work times and labor savings. Surveying and pile-driving tasks can be done with intuitive AR guidance, allowing people without specialist skills to achieve a certain level of accuracy and helping maintain productivity even amid a shortage of skilled workers.

• Smoother information sharing and consensus building: Visualized on-site information functions as a common language among stakeholders. For example, road works often involve multiple utilities such as water, gas, and communications; aggregating their buried-object data and displaying them together in AR enables everyone in a joint on-site meeting to share the same image. This reduces time spent spreading out paper drawings and negotiating adjustments and helps prevent mistakes due to mismatched understanding. AR-based visualization becomes a means to obtain shared understanding across differences such as site vs. office or veteran vs. junior staff, facilitating smoother consensus building and decision-making.

• Quality improvement and sustained DX promotion: Data and on-site know-how gained through AR can help improve construction quality and advance DX (digital transformation). For example, point cloud data and photos collected on site alongside AR can be shared in the cloud for accumulation and analysis. This allows quantitative evaluation of as-built variation to improve construction accuracy, optimization of preventive maintenance plans by comparing inspection data, and other expansions into data-driven advanced management. Introducing AR is not only a one-off efficiency gain but also a step toward digitalizing sites and a foundation for future productivity revolutions.

Closing: Simple surveying with LRTK

Some may feel that realizing site visualization with AR requires time-consuming preparation such as high-precision positioning equipment and data creation. However, today there are simple surveying solutions that address these hurdles all at once. One such system is called LRTK. Attaching an LRTK-series device to a smartphone or tablet makes it surprisingly easy to perform centimeter-class positioning (half-inch class positioning), 3D scanning, and stable AR display. The major appeal is that site personnel can complete everything from surveying to AR visualization using just a smartphone, without needing a specialist surveyor or large equipment.

For example, walking around a site with a smartphone fitted with an LRTK-compatible antenna allows real-time acquisition of high-precision point cloud data with position coordinates. The acquired data can be immediately saved to and shared via the cloud, enabling office staff to review the site’s 3D model remotely. If you import design drawings or buried pipe data into LRTK’s app, you can perform AR projection directly on site. No troublesome calibration for alignment is required, and the UI is designed so that even those inexperienced with machinery can operate it intuitively.

LRTK is a cutting-edge technology aligned with the Ministry of Land, Infrastructure, Transport and Tourism’s i-Construction initiative (aimed at improving productivity on construction sites) and is a potent solution to drive DX in the construction and civil engineering industries. It offers performance comparable to expensive dedicated equipment at a fraction of the traditional cost. By leveraging LRTK to dramatically improve surveying accuracy and work efficiency on site, consider implementing the next-generation visualized civil engineering site.

FAQ

Q: What is needed to implement AR-based “visualization” on civil engineering sites? A: Basically, you need digital data of the objects you want to visualize (e.g., drawing data or 3D models including buried object locations, point cloud scan data) and AR-capable devices that can display them on-site. Today, combining tablets or smartphones with high-precision GNSS receivers (RTK-capable) makes on-site AR simple. For example, by preparing drawing data of buried pipes or point clouds obtained during construction and using a smartphone equipped with an RTK-GNSS antenna, you can overlay a virtual model of pipes accurately onto the camera view on-site.

Q: How reliable is the accuracy of AR display? A: When RTK-GNSS is used in combination, virtual objects can be placed with very high accuracy—on the order of a few centimeters (a few inches) in both horizontal position and elevation. AR using GPS alone could be off by several meters (several ft), but RTK correction can improve accuracy to a level that is hardly perceptible to the human eye. Therefore, it is reasonable to assume that pipes and structures displayed on the screen almost match their real-world positions. However, accuracy is influenced by satellite reception conditions and the surrounding environment, so it should be noted that zero error cannot be guaranteed at all times.

Q: Will AR remove the need for traditional drawing checks and ground marking? A: AR allows direct confirmation of object locations on-site, so the effort of comparing paper drawings or spray-marking the ground can be greatly reduced. In practice, AR adoption has simplified pre-excavation surveys and some record photography tasks for buried pipe work. However, drawing data remain necessary as future management documents, and AR is a tool to support field work. Final construction verification and surveying should still be performed by cross-checking digital data and ensuring safety.

Q: Can workers unfamiliar with IT handle AR systems? A: Yes. Modern AR apps are designed for intuitive operation: pointing a smartphone or tablet camera displays the necessary information in a simple manner. Many sites report that “it was usable immediately without training” or “older workers who are familiar with smartphones had no problem.” With basic operation guidance at introduction, many people can adopt AR in site operations without resistance.

Q: In what situations can AR be used? Is it limited to buried pipes? A: Of course not. AR can be applied broadly across construction and civil engineering, not only to underground utilities. As described above, AR can project pre-completion structure models on-site for construction checks, highlight deterioration during infrastructure inspections, and more. Essentially, as long as positional information is digitized, AR can make “things that are usually hard to see” visible on site. With creativity, AR can assist everything from construction management to maintenance and training.