LRTK Revolutionizing Railway Signal Communications: Accelerating On-Site DX with Smartphone RTK × AR

Introduction: Field Challenges in Railway Signal Communications and the Need for DX

The railway signal communications field is the unsung force that supports safe train operations. Many pieces of equipment—signals and points beside the tracks, cables, and more—monitor railways around the clock. However, construction and maintenance sites still retain strong elements of analog work, posing challenges in terms of both efficiency and safety. In particular, the burden of nighttime work is significant: concentrated tasks must be performed in the limited hours between the last and first trains (typically around midnight to the early morning hours of 4 a.m.). Working in the dark with limited personnel and relying on paper drawings for construction and inspection increases the risk of mistakes and often forces reliance on veteran intuition. Moreover, as the industry faces an aging workforce and labor shortages, the need for on-site DX through digital technologies (digital transformation) is growing. On-site DX refers to initiatives that leverage digital tools to streamline and enhance field operations. In railway signal communications, DX is strongly expected to boost productivity and reduce human error.

Inefficiencies and Constraints in Traditional Construction, Inspection, and Design Management

To date, many processes in railway signal construction and maintenance inspections have depended heavily on manual work and experience. For example, when locating a new signal pole (the pole for a signal), survey teams have had to use tape measures and optical surveying instruments (such as total stations) to repeatedly measure distances from reference points and mark positions beside the tracks at night. Determining positions while holding a paper drawing and illuminating it with a flashlight is a complex procedure prone to human error. The work often requires a manpower approach, and because it depends on veterans’ intuition, it is hard to standardize and is highly person-dependent.

The same applies to inspection tasks, where personnel check equipment while referring to paper logbooks and drawings. For instance, when confirming a communication cable route, workers must compare pre-printed wiring diagrams with the actual installation to find anomalies, which is inefficient on site. Unfolding paper drawings for verification during the short nighttime work window is extremely inefficient, and dim conditions increase the risk of recording errors.

In addition, the slow pace of data sharing used to be a bottleneck. Notes written on site and photos taken had to be reorganized back at the office and reflected in reports and drawings. This time lag sometimes led to measured values not being accurately reflected or to departments not receiving the latest information. With paper-based management, information tends to be scattered and fragmented, and measurement results gathered through overnight work are often underutilized.

In short, the railway signal communications field faced a dual inefficiency of “labor-intensive nighttime work” and “paper-drawing-centered management.” To break this situation and maintain infrastructure safely and reliably, business innovation using the latest technology is indispensable.

Smartphone RTK × AR × 3D Scanning “LRTK” Features and Integration

One solution to these issues is the positioning system “LRTK,” which leverages smartphone RTK × AR technology. LRTK is our system that equips a smartphone with a compact high-precision GNSS receiver to enable centimeter-level positioning (inch-level accuracy). By combining a smartphone with a dedicated antenna, accuracy comparable to surveying equipment that once cost several million yen becomes easily accessible to anyone.

LRTK has three major features. The first is smartphone RTK positioning. RTK (Real Time Kinematic) is a technique that corrects satellite positioning errors in real time to obtain high-precision positions, and smartphone RTK brings this capability to mobile devices. Standard smartphone GPS has errors of several meters (several ft), but LRTK uses networked electronic reference station information and augmentation signals from the Quasi-Zenith Satellite System Michibiki to improve accuracy to errors of a few centimeters (a few inches). The smartphone screen displays real-time coordinates of the current position, and by simply pressing a button at the point you want to measure, you can acquire and save that 3D coordinate. Surveying that previously required multiple people can now be completed by a single person with a smartphone.

The second feature is AR (augmented reality) visual guidance. Through the camera view of the LRTK-compatible app, design data and guidance markers can be overlaid onto the real-world view. Because high-precision RTK positioning keeps the digital information correctly aligned with your position and orientation, a virtual AR marker can be displayed exactly at the spot “where this signal pole should be” on site. Where determining positions used to require measuring dimensions on drawings and pounding stakes, you now simply follow arrows on the smartphone screen to be led to the precise point. Wiring routes and other elements can also be drawn on the ground as AR lines or arrows, making it easy to grasp paths that were hard to visualize on paper. AR displays are visually prominent even in dark sites, so judgments such as “which part to replace” or “which route to lay the cable” can be made quickly and accurately during nighttime work.

The third feature is 3D point cloud scanning. Modern smartphones are equipped with LiDAR sensors and high-performance cameras, allowing the surrounding structures to be scanned and recorded as a set of points (point cloud data). LRTK combines these point cloud measurements with RTK positioning to attach precise positional coordinates to scanned objects and save them. For example, after installing a signal pole, scanning the area around the pole with a smartphone yields three-dimensional data indicating the pole’s height, tilt, and positional relationships with surrounding objects, automatically saved to the cloud. Previously, point clouds obtained by laser scanners required specialized work to combine on a PC, but with LRTK you can obtain an as-built 3D model simply by waving a smartphone at the site.

These smartphone RTK positioning, AR, and point cloud scanning features are useful on their own, but LRTK is designed to integrate them within the same app. In other words, you can seamlessly measure, view, and record with a single smartphone. For example, using a smartphone equipped with LRTK in survey mode, you can measure coordinates of reference points, then switch to AR mode to display a modeled signal device from the design on site to confirm position, and then use point cloud mode to scan and record the completed structure—carrying out this workflow without interruption. Acquired coordinate data, point clouds, and photos can be shared to the cloud immediately and checked on office PCs almost in real time. The ability to compare design data and field conditions in real time and complete recording in a one-stop flow is LRTK’s greatest strength.

LRTK Use Scenarios for Signal Pole Installation and Cable Route Management

Now let’s look at representative scenarios showing how LRTK can be applied to concrete field tasks in railway signal communications.

● Use in signal pole installation: When erecting or replacing a signal pole, accurate positioning and vertical installation are essential. Traditionally, survey crews calculated offsets and heights from the track center, marking installation positions with stakes or chalk. After introducing LRTK, design data for pole positions can be preloaded into the smartphone and displayed on site as AR markers. Workers can identify installation spots to within a few centimeters (within a few inches) by checking virtual pole models or ground markers on the smartphone screen. For example, numerical guidance such as “0.05 m (0.16 ft) east and 0.10 m (0.33 ft) north from the designated position” can appear on the screen, eliminating the need to pull out a tape measure. After erecting the pole, scanning the surroundings with the smartphone converts the pole’s tilt and height into point cloud data for storage. This allows digital verification later of foundation burial depth and signal height against the design, helping to prevent reinstallation. Point cloud data is also useful for future maintenance: when inspecting whether a pole has tilted over time, comparing current and past point cloud models enables quantitative assessment of changes.

● Use in cable route design and management: LRTK also has great power in planning and installing signal communication cable routes. Traditionally, route decisions required walking the site with paper wiring diagrams in hand, marking routes while considering terrain and interference with other equipment. With LRTK, CAD drawings or GIS cable route plans can be loaded into the smartphone and projected onto the ground with AR. On site, virtual cable lines appear on the screen, so workers can perform trenching and wiring by following them. For instance, if the route is “run fiber optic cable south along the track from inside the station and connect to signal X,” that path will be shown as a line on the ground through the smartphone, with turns and junctions clearly visible. Eliminating the need to compare paper drawings while measuring enables accurate route laying in a short time even during nighttime work.

In addition, LRTK is valuable for buried cable location management. Previously, records of buried cables were often left as photos and handwritten notes. With LRTK, scanning and converting the cable to a point cloud before burial and uploading it to the cloud provides high-precision 3D location records. For example, you can save the entire point cloud showing “how deep and along what path the communication cable between signal A and B is buried.” This data can later be visualized with AR when digging in the area for other work. By pointing a smartphone at the site, the buried cable position and depth beneath pavement become visible, greatly reducing the risk of accidental damage and enabling safe, efficient excavation. LRTK truly becomes a tool that “digitally maps” the railway signal communication cable network so anyone can intuitively grasp it.

● Use in maintenance and inspection: LRTK is also effective in routine inspections and trouble responses for signal communications equipment. For example, during nighttime inspections, displaying AR markers for “parts scheduled to be replaced” or “bolts that need adjustment” helps workers find targets without hesitation in the dark. Imagine the next bolt to be tightened or the next cable connection point highlighted by a glowing marker. This reduces the time spent locating targets on site and allows full use of limited work time. Also, storing geotagged photos taken with LRTK in the cloud makes it possible for the office to accurately determine “which part of which signal was inspected” afterward. This prevents misreading field notes or mixing up photos and smooths report preparation. Since cloud data is accumulated as history, advanced analyses like overlaying past inspection photos with the same viewpoint in AR for comparison may become feasible.

Effects of LRTK Introduction: Improvements in Safety, Accuracy, Efficiency, and Record Integration

Through the scenarios above, LRTK brings many benefits to railway signal communications sites. The main effects of introduction are summarized below.

• Improved safety: High-precision positioning and AR guidance shorten work time and reduce the time spent working beside tracks at night. This lowers the frequency of entering hazardous areas and reduces exposure risks to workers (hazards from passing trains and unstable footing). Visualizing buried cables with AR can prevent unexpected excavation damage, directly contributing to safety.

• Improved accuracy: RTK positioning achieves accuracy on the order of a few centimeters (a few inches), dramatically improving the precision of signal pole placement and cable route laying. This greatly reduces errors that would otherwise require repositioning after installation. Because AR always allows comparison of design data with the field, deviations can be detected and corrected during construction, minimizing departures from quality standards.

• Improved efficiency: With one smartphone per person able to handle surveying, layout, and inspection, tasks can be completed with fewer personnel even in labor-short sites. Intuitive on-screen guidance enables workers without veteran experience to perform tasks, reducing training time. Consequently, each process’s required time shortens, allowing more work to be completed within the limited window from the last to the first train. Labor savings and time reductions will also help alleviate overtime and night shift burdens.

• Improved recordability: Measured coordinate data, point cloud data, and photos are automatically saved and aggregated in the cloud, reducing omissions in records. There is no need to transcribe to paper forms or input data later, practically eliminating human error concerns. Having inspection histories and as-built records in time series creates a digital archive useful for later cause analysis and future planning.

• Information sharing via cloud integration: Data acquired with LRTK can be shared immediately with stakeholders via the cloud. Values measured on site can be shared with the office on the spot to get real-time instructions. Coordinates and point cloud information collected by multiple field teams are centrally managed in a global coordinate system, making it easy to integrate data later for wide-area analysis. Digitally connecting field sites and remote offices speeds up reporting and approval processes and promotes organization-wide DX.

As described above, introducing LRTK positively impacts safety, accuracy, efficiency, recordkeeping, and information sharing, raising the overall quality and productivity of railway signal communications work.

Conclusion: Applications for Simple Surveying and the Future of On-Site DX

Introducing the smartphone RTK × AR solution “LRTK” to railway signal communications sites not only directly addresses current issues but also serves as a first step toward further DX expansion. LRTK can be expanded horizontally to various tasks beyond signal communications, such as simple surveying associated with railway construction, structural inspections, and management of other infrastructure assets. For example, it can be applied to tasks like checking building clearance around tracks, verifying catenary pole heights, and surveying equipment layouts within stations, and has already begun to show results in other fields. The era of “everyone a surveyor with a single smartphone” is becoming a reality in railway sites as well.

With infrastructure DX led by the Ministry of Land, Infrastructure, Transport and Tourism and technology innovation across railway companies, on-site digitization will accelerate further. In that context, early adoption and use of easy, high-precision tools like LRTK will not only improve operational efficiency but also strengthen corporate competitiveness. As work that once relied on veterans’ intuition and experience shifts to data-driven smart construction, nights of worrying about mistakes will decrease, and a safer, more resilient railway infrastructure maintenance system will be established.

On-site DX in railway signal communications has only just begun, but its effects are steadily appearing. Please consider proactively exploring the introduction of the latest technologies through “LRTK.” With the new power of smartphone RTK × AR, bring revolutionary efficiency and peace of mind to your sites and step into the next generation of railway infrastructure management.