ARヒートマップが支える安全施工 – 見えない埋設物もその場で可視化

目次

• 見えない埋設物が引き起こす事故と課題

• ARヒートマップで地下インフラを「見える化」

• 高精度ARを支えるRTK測位技術

• ARヒートマップ導入のワークフロー

• ARヒートマップがもたらすメリット

• 現場事例と今後の展望

• おわりに：LRTKが実現する簡易測量とAR表示

• FAQ

Roadworks and utility construction sites for water, sewerage, and gas often face a major source of anxiety: not knowing what is buried underground. Accidentally damaging buried pipes or cables can lead to serious incidents such as water leaks, gas leaks, or power outages. In recent years, a new solution called an AR heatmap has attracted attention as a way to address this “invisible risk.” By visualizing underground information through a camera, it enables safer and more efficient work. This article explains in detail how AR heatmap technology helps prevent accidents involving buried utilities, its effects, deployment methods, field cases, and even introductions to the LRTK system that enables simple surveying.

見えない埋設物が引き起こす事故と課題

A constant concern at road excavation sites and land development sites is the damage to existing underground infrastructure. For example, accidentally nicking a water main can cause large-scale leakage; a gas main can lead to gas leaks or even explosions. Cutting power cables or communication lines can cause power outages or communication failures that seriously affect society. In fact, many incidents of buried-utility damage are reported domestically every year, and the majority stem from not knowing exactly what is buried where.

To prevent such accidents, maintenance and management of buried pipes have long been handled with great care. In new construction, positions and depths are recorded by surveying before backfilling, and kept as drawings or photo logs. Later works rely on those drawings, with experienced workers carefully excavating while assuming, “There should be a pipe around here.” As needed, ground-penetrating radar is used to locate buried items, or trial excavations are performed to directly confirm positions.

However, management that relies on paper drawings and human intuition has limitations. In urban areas with complex underground piping, old as-built drawings often do not match reality. Near-miss incidents where an unexpected pipe appears from a spot shown blank on the drawings are common. It is also difficult to mentally visualize the three-dimensional relationships of intersecting pipes, and even veterans can overlook or misinterpret things. Ultimately, the fundamental challenge in infrastructure construction and management is always how to make the invisible visible.

If the underground situation could be understood intuitively, not only could excavation troubles be avoided, but inspections of aging pipes and renovation planning would become far more efficient. The trump card expected to achieve this is visualization of buried utilities using AR (augmented reality) technology.

ARヒートマップで地下インフラを「見える化」

AR (Augmented Reality) is a technology that overlays digital information onto camera images from a smartphone or tablet. Applied to buried-utility management, it can virtually visualize pipes and cables buried underground on the spot. For example, pointing a smartphone camera at the ground can render water and gas mains on the screen as if you were “seeing through” the surface. Workers can intuitively grasp “what is buried directly beneath their feet and how” by viewing 3D models of the pipes overlaid on the real scene. The major advantage is that underground structures can be confirmed in situ, like the real thing, without relying on drawings or guesswork.

To realize such AR heatmap-based underground visualization, advanced technology that aligns virtual models with the real world precisely is essential. Built‑in GPS and electronic compasses in smartphones can have errors of several meters, causing virtual pipe overlays to be significantly offset from their actual buried positions. That degree of error cannot be called “seeing through” and may even mislead and create danger. Conventional outdoor AR often required placing markers (registration targets) on site or performing manual calibration the first time. For wide-area infrastructure management, placing markers at every location or manually adjusting each time is impractical.

The solution to these problems is the markerless high-precision AR realized by the combination of “smartphone + LiDAR + RTK‑GNSS.” Modern smartphones come with powerful AR platforms that use camera and IMU data to track device movement in space. Higher-end models even include compact LiDAR sensors that capture the surrounding environment as real-time 3D point clouds. Because LiDAR can accurately sense terrain and object shapes/distances, virtual objects (such as 3D models of buried pipes) can be stably overlaid on reality and occlusion—where virtual objects are naturally hidden by real objects—can be rendered realistically. In other words, smartphones can instantly build a three-dimensional map of their surroundings in addition to camera images, dramatically strengthening the AR display foundation.

The final piece is knowing the smartphone’s own precise position. This is where the high-precision positioning technology RTK‑GNSS (Real‑Time Kinematic Global Navigation Satellite System) proves powerful. If RTK enables centimeter-level accuracy (half-inch accuracy) in device positioning, virtual underground models can be placed to precisely match real pipe positions.

高精度ARを支えるRTK測位技術

RTK (Real-Time Kinematic) is a method that dramatically improves satellite positioning accuracy by applying correction information. By simultaneous observation with a base station at a known point, typical GNSS errors of several meters can be reduced to within a few centimeters (a few in). Since centimeter-level accuracy (half-inch accuracy) can be obtained in both horizontal and vertical directions, RTK has long been used in the surveying field.

Traditionally, high‑precision GNSS equipment was expensive and required specialized operators, but recently ultra-compact RTK‑GNSS receivers have appeared, making centimeter accuracy accessible on-site to anyone. For example, a university-venture startup developed an “RTK smartphone receiver” that enables RTK positioning simply by attaching a thin device weighing about 165 g to the back of a smartphone. It operates on an internal battery for long periods and can be attached like a smartphone case. It also supports the centimeter-level positioning augmentation service (CLAS) provided by Japan’s quasi-zenith satellite “Michibiki,” allowing stable centimeter-level accuracy (half-inch accuracy) to be maintained using only satellite augmentation signals even at sites in mountainous areas without mobile coverage. In urban areas, conventional network-based RTK correction services can be used, allowing real-time corrections to within a few centimeters (a few in) anywhere in Japan. With the combination of smartphone + high‑precision GNSS, the era in which everyone can carry a high‑precision positioning tool in their pocket is becoming a reality.

The future in which each field technician equips a smartphone with high‑precision GNSS and can quickly take it out for surveying or AR visualization is already within reach. In the latest systems, intuitive Japanese UI on the smartphone displays current position and navigation information, making them easy to use without specialized knowledge. For example, tasks that used to require two people—staking out pile-driving positions—can be done by one person holding a lightweight pole with an RTK‑equipped smartphone fixed to it; following on-screen guidance enables accurate single-person staking. The spread of easy-to-use high‑precision positioning will dramatically improve productivity and accuracy in surveying and construction management.

ARヒートマップ導入のワークフロー

By leveraging smartphone AR and RTK positioning, the entire process from construction records of buried utilities to maintenance can be digitized. Below is the workflow for realizing buried‑utility visualization using AR heatmaps, from data recording to on-site use.

• 埋設物の3D記録（施工時）: For newly buried pipes, scan the pipe and excavation area with a smartphone (LiDAR-equipped) before backfilling. If an RTK‑GNSS receiver is attached to the smartphone, the acquired point cloud is automatically tagged with high-precision absolute coordinates (public coordinate system), and the site’s 3D data is saved to the cloud. The system automatically generates a 3D model (mesh) of the pipe from the point cloud, digitally recording the pipe’s exact route, depth, and shape. Traditionally, after backfilling one had to measure with a tape and create drawings or spray-mark routes on temporarily restored pavement, but with this method a detailed 3D record is completed simply by scanning.

• データ共有と資産管理: Point clouds and model data obtained on site can be shared immediately via the cloud and viewed from office PCs or other devices. If integrated into maintenance ledgers or GIS as infrastructure asset information, they help plan future inspections and coordinate with other works. Advanced cloud-based processing—such as extracting diameters and burial depths from arbitrary cross-sections of the point cloud or automatically calculating excavation/backfill volumes—can be done with a click. Field staff can instantly obtain required numerical information without creating CAD drawings or manual calculations. Because 3D data can be shared in real time between the field and the office, supervisors can issue instructions while reviewing the point cloud model remotely, and earth disposal or material procurement can be advanced preemptively.

• AR可視化による現場活用（維持管理時）: Accumulated 3D data of buried utilities can be used for on-site verification during inspection and renovation via AR display. For instance, years later when the same road is excavated again, it’s unnecessary to pull out old drawings and guess burial locations. Launching an AR app on a smartphone and pointing the camera will instantly show the locations and routes of pipes beneath the pavement in 3D. Information such as “a single water main with diameter ○○ mm (○○ in) runs directly below here” or “a gas main runs parallel on the far side” is displayed at a glance as color-coded virtual pipe models overlaid on the real scene. Depth information can also be shown as labels, so vertical relationships such as “this water main is approximately 1.2 m (3.9 ft) below the surface” can be shared. What had relied on veterans’ intuition and paper documents becomes a digital, anyone-can-do visualization task.

Through this flow, the cycle of buried‑utility management—from surveying and recording to information sharing and AR-based on-site verification—is digitally integrated. Because precise 3D information that paper drawings and photos could not fully capture is recorded, high‑precision location data can be preserved without deterioration over time. As a result, maintenance accuracy improves and contributes to accident prevention and more efficient planning in the future.

ARヒートマップがもたらすメリット

As described above, using AR heatmap technology delivers various benefits in terms of both safe construction and efficiency. Key effects are summarized below.

• 埋設物事故の防止: AR allows accurate recognition of buried locations and depths before excavation, greatly reducing the risk of accidentally damaging pipes with heavy machinery. Visualizing invisible hazards such as gas mains and high‑voltage lines in color in advance dramatically strengthens on-site safety measures. Because everyone can view the same information through the camera, mistakes due to “not knowing” are also prevented.

• 作業の効率化・省力化: The need to infer positions from drawings is eliminated, enabling precise excavation and investigation only where necessary and shortening work time. Multiple processes—surveying, layout marking, and pipe recording—can be completed with a single smartphone, reducing manpower, shortening schedules, and cutting costs. If the design model is displayed in AR during construction, slopes and positions of pipes can be confirmed on the spot during installation, reducing rework and stabilizing quality.

• 記録精度の向上: Digital records from point cloud scans can store the position and shape of buried utilities to millimeter precision, leaving far more accurate data than paper drawings or verbal handovers. This provides a highly reliable information base for future maintenance ledgers. Data stored in the cloud eliminates concerns about loss or deterioration. Because past and present data are easy to compare quantitatively, changes since the last inspection can be objectively assessed during annual checks.

• 点検計画・老朽化対策の高度化: AR heatmaps are powerful for preventive maintenance. Overlaying current 3D data with past repair histories in AR lets you quickly identify degraded sections and consider reinforcement methods. For example, when investigating road subsidence risk areas, AR display of voids detected by ground‑penetrating radar or sewer deterioration data while marking the site ensures no risk areas are overlooked. Data-driven inspection planning enables efficient management of aging infrastructure within limited budgets and personnel.

• 情報共有と合意形成の円滑化: AR visualization serves as a common language on site. Roadworks involve multiple buried-utility operators—water, gas, communications, etc.—but integrating their pipe data and displaying it collectively in AR allows all parties at joint inspections to share the same underground picture. This reduces the need to compare paper drawings and lessens recognition gaps and communication errors. For explanations to clients or neighboring residents, showing “this many pipes run beneath this road” through a smartphone makes understanding easier and helps build consensus. AR heatmaps support the field not only in safety but as a powerful communication tool.

• 現場DX（デジタルトランスフォーメーション）の推進: Introducing RTK × AR accelerates digitalization of construction sites. This aligns with the Ministry of Land, Infrastructure, Transport and Tourism’s *i-Construction* initiative, and the use of ICT and 3D data contributes to productivity gains and advanced safety management. Tasks that formerly relied on experience and intuition become data-driven, creating worksites where anyone can make accurate decisions and perform tasks. As a result, defects and rework decrease, and life-cycle costs of infrastructure maintenance are expected to be reduced.

現場事例と今後の展望

RTK × AR visualization of buried utilities is already being used in sites at home and abroad. Domestically, a startup combined a tablet with a compact RTK positioning unit to develop a system that displays underground pipes in AR on the spot. Without spreading paper drawings or performing trial excavations, site personnel can intuitively grasp the spatial relationships of buried utilities on the screen, improving safety and work efficiency. Field trials reported that pipe-recording tasks were completed without photo shoots or CAD drawing creation, and subsequent excavations could immediately locate pipes via AR display—showing substantial effect. Workers praised that exploring buried utilities no longer depended on intuition and that operation was intuitive enough to use without prior training, indicating promising uptake in the field.

Internationally, outdoor high‑precision AR systems are attracting attention as cutting‑edge technology in the construction industry. Systems that combine high‑performance GNSS receivers and AR allow centimeter-level alignment of 3D design models and underground utility information on smartphone screens, enabling on-site intuitive sharing and verification of complex BIM models and piping networks. Both in Japan and abroad, RTK × AR initiatives for construction DX and smart maintenance are active, with adoption expanding across projects from bridge works to water and sewer maintenance.

Going forward, this high‑precision AR technology is likely to become more generalized and simplified and may become a new industry standard. A future in which each worker routinely points a smartphone at the site and works while checking design drawings and underground conditions via AR heatmaps is imminent. When expensive equipment and special skills are no longer required and everyone can handle accurate spatial-coordinate-based information in real time, a productivity revolution in construction and infrastructure is expected to accelerate.

おわりに：LRTKが実現する簡易測量とAR表示

The combination of RTK and AR for visualizing buried utilities is transforming infrastructure maintenance and civil engineering sites. Overlaying digital data on the real world with centimeter-level accuracy (half-inch accuracy) shifts work that used to depend on experienced workers to data-driven smart construction. The leading-edge solution now garnering attention for making this capability easily usable on-site is LRTK.

LRTK is an integrated system that achieves centimeter-level positioning and AR visualization easily for anyone by using a small RTK‑GNSS receiver attached to a smartphone and a dedicated app. Many conventional AR surveying tools require pre-placed markers or complicated initial calibration, but with LRTK the RTK fixes within tens of seconds after powering on the device, allowing immediate high‑precision AR. No special calibration is required—the system is ready to use as soon as you arrive on site. Cloud integration enables seamless operations such as downloading design models or point‑cloud survey data to overlay on the spot, and uploading measured data for instant sharing. Designed to be intuitive even for non‑specialists, reports indicate that one smartphone per person could cover surveying, layout marking, inspection, photo logging, and AR simulation.

By using LRTK, field productivity and safety can be dramatically improved without expensive equipment or large teams. In addition to buried‑utility visualization, it can be applied broadly to tasks such as as-built heatmap verification and construction navigation, serving as a true “all‑purpose surveying instrument” and a trump card for site DX. Surveying firms, municipal civil engineering departments, and construction contractors are encouraged to adopt this cutting‑edge RTK × AR technology and step into a new stage of smart infrastructure management.

FAQ

Q: ARヒートマップとは何ですか？ A: A method of visualizing invisible data by overlaying digital, color‑coded information on camera images of the real world. In construction, it displays buried pipes or subsurface deformations as a heatmap so you can inspect them as if seeing through the ground. For example, by pointing a smartphone at the ground, the positions of underground water or gas mains are color-coded and displayed at a glance.

Q: なぜ埋設物をAR表示するのに高精度な測位が必要なのですか？ A: To accurately align a virtual pipe model with its real buried position, the smartphone’s position and orientation must be known to within a few centimeters. Ordinary GPS has meter‑level errors, causing AR pipe overlays to be misaligned and invalidating the “see-through” effect. High‑precision positioning like RTK‑GNSS enables the device position to be determined within a few centimeters (a few in), allowing virtual models to match real locations precisely.

Q: 地下埋設物の3Dデータはどのように用意するのですか？ A: For existing buried pipes, past drawings and GIS data are the basis. For new pipes, record 3D data during construction by LiDAR scanning with a smartphone plus RTK positioning before backfilling. Alternatively, results detected by ground‑penetrating radar can be converted into point cloud data and imported. In any case, preparing three‑dimensional data with accurate position information in advance is essential. If that data is reliable, the virtual pipes displayed on the AR heatmap will match actual buried locations.

Q: スマホだけで地下の様子を透視できるのですか？ A: Yes—combining a modern smartphone’s camera, IMU, and LiDAR AR functions with a small external RTK‑GNSS receiver makes it possible. This setup displays the positions of buried utilities accurately on the smartphone screen without専用の測量機器や特殊なARゴーグル. In real sites, even first‑time users have reportedly started using the system without prior training and found it useful immediately.

Q: LRTKとは何ですか？ A: LRTK is a solution that makes high‑precision positioning and AR‑based buried‑utility visualization easily accessible using smartphones. It consists of a lightweight RTK‑GNSS module that attaches to a smartphone and a dedicated app, enabling on-site display and surveying of buried 3D data without complicated setup or marker placement. In short, LRTK is a “universal AR surveying tool” that advances the construction site to the next stage. Try LRTK to realize safe and efficient smart construction.