Railway signaling and communications equipment refers to signals and point (switch) control devices that convey information such as proceed/stop to trains, as well as the communication networks that connect them. The construction and maintenance of these systems are essential for safe train operations, and even small mistakes can lead to major accidents or service disruptions, so extremely high precision and safety management are required. In recent years, a wave of digital transformation (DX) has reached this field as well, raising expectations for new technologies that can achieve both safety assurance and improved work efficiency. However, many analog methods remain in fieldwork, and various issues have been pointed out.

In conventional railway signaling and communications construction, it is not uncommon to carry out surveying and stakeout with drawings in hand and to rely on human eyesight and experience to confirm cable routing and equipment installation. As a result, several problems tend to occur.

• Several issues: - Incorrect installation positions: When determining positions on site based on paper drawings, small measurement errors or misreading of coordinates can lead to significant misalignments. Even an error of several tens of centimeters in the position of a signal pole or buried cable can require substantial effort and cost to correct later. - Tedious drawing verification: Workers must spread out drawings and match the current location to the design position for each installation. In signaling and communications systems that involve complex wiring routes and numerous devices, this verification work tends to consume time and reduce on-site efficiency. In addition, misreading of drawings or differences in interpretation can lead to communication loss among stakeholders. - Safety risks: Situations arise where workers must enter dangerous areas beside tracks for surveying or stakeout, or work near heavy equipment. Conventional methods also require larger crews, increasing movement on site and raising the risk of human error or contact accidents. - Rework occurrences: If discrepancies from the design are discovered after construction, rework or repairs (for example, re-pouring a signal pole foundation or re-routing cable wiring) are unavoidable. Such rework not only causes schedule delays and cost increases, but also can negatively impact safety by extending nighttime work, for example.

As described above, conventional methods have limitations in efficiency, accuracy, and safety, and executing work “exactly as on the drawings” itself has become a major challenge. Railway construction in particular requires high-precision work within limited time windows such as nighttime, and a single mistake directly affects train operations and safety. For that reason, overcoming these challenges with digital technologies has become an urgent priority. What is attracting attention is the “AR Construction Navi” that leverages AR (augmented reality) technology and high-precision positioning.

What is AR Construction Navi – Overview of LRTK high-precision positioning and point-cloud scanning technology

The AR Construction Navi is a new construction support tool that fuses AR (augmented reality) technology with high-precision positioning systems. The use of 3D design data on site aligns with initiatives such as the Ministry of Land, Infrastructure, Transport and Tourism’s i-Construction policy and the promotion of BIM/CIM (3D model utilization), and is drawing attention across the infrastructure sector. It overlays digital design information onto the site view captured by a smartphone or tablet camera so that workers can intuitively understand “what should be installed where.” At its core is the high-precision GNSS positioning technology called LRTK. LRTK (pronounced “L-R-T-K”) is a positioning system using a compact RTK-GNSS receiver that receives correction information from a base station in real time, reducing typical GPS positioning errors of several meters down to a few centimeters. When a smartphone is fitted with LRTK and powered on, high-precision positioning known as a “Fix” solution is established in about 30 seconds, yielding planar accuracy of about ±1–2 cm. This largely eliminates the discrepancy between the digital design coordinates and the user’s measured on-site position, allowing AR-displayed models to align exactly with real objects.

Traditionally, positions were determined by surveyors’ stakes and layout markings using tape measures, but with AR Construction Navi, workers can reach accurate points just by following guides displayed on the smartphone screen. It is truly like an “on-site car navigation”; workers are guided by the device with prompts such as “5 cm to the east,” enabling them to install equipment or structures without deviation. For example, as a worker approaches the design coordinate of a signal pole, a target marker appears on the screen and, once sufficiently close, visually indicates “this is the installation position.” By combining RTK-GNSS accuracy with AR display, even less-experienced workers can achieve the same positional accuracy as veterans, enabling everyone to perform construction with centimeter-level precision.

Moreover, AR Construction Navi also integrates with 3D point-cloud scanning. By scanning the site shape using a smartphone’s LiDAR sensor or photogrammetry, you obtain three-dimensional point cloud data with accurate coordinates assigned to each point via LRTK. By matching this point cloud with the design 3D model in the cloud, a heat map showing deviations of the as-built shape (post-construction form) can be automatically generated. If that heat map is downloaded to the device and displayed in AR, it can be superimposed on actual structures for on-site verification. For example, it becomes immediately apparent whether foundation elevations or cable burial depths match the design. Inspections that used to be done after completion by surveying and comparing with drawings can now be confirmed and recorded digitally on the spot with AR Construction Navi. For instance, if the top level of concrete foundation is insufficient, that area will appear red on the heat map, allowing immediate repair on site before it becomes a finding in a later inspection. Cloud integration allows collected on-site information to be shared and stored instantly, so all stakeholders reference the same up-to-date data. Such mechanisms lay the foundation for site DX where data is utilized consistently from design through construction, inspection, and records. The simple configuration of a smartphone and an antenna also makes introduction and deployment easy, and it is revolutionary that workers without surveying qualifications can operate it intuitively.

Visualizing the site with AR – Applications to signal poles, cable routes, and more

So how does this AR Construction Navi specifically help on site? Let’s look at the main use cases in railway signaling and communications construction.

• Signal pole installation: When erecting signal masts or sign posts, AR Construction Navi visualizes the design position and height in situ. By displaying a virtual pole model on the ground and indicating the center point of the foundation or the arrangement of anchor-bolt positions to millimeter precision, workers can install equipment without deviation while positioning the hardware. Because distances and height relationships with surrounding equipment can also be confirmed in AR, problems such as “the post position is wrong” can be prevented in advance.

• Cable route laying: Signal communication cables and fiber-optic routing can be displayed as virtual route lines on the ground or on structures via AR. For example, when installing cable racks inside a tunnel, AR draws the design mounting positions and routes on the wall, so workers can attach brackets and route cables according to the guidance. Branch points and bend radii are also visualized, reducing the need to repeatedly consult drawings even in complex routes and preventing omissions in construction.

• Control cabinet mounting: Relay control cabinets and communication equipment racks to be installed in station buildings or signal boxes can also have their installation positions projected in AR for verification. The outlines of equipment and positions of mounting holes can be displayed on walls or floors to guide drilling and installation. Even when lining up multiple cabinets, AR allows pre-assessment of layout balance, eliminating the need for physical trial-and-error. There are also initiatives to use AR to display wiring labels and device layouts inside control cabinets transparently, aiding on-site wiring checks. This is expected to reduce human errors in complex wiring tasks.

• Underground duct installation: AR is effective for confirming positions of underground cable ducts or water pipes. By projecting buried routes from drawings onto the ground in AR, invisible piping can be visualized before excavation. This enables machine operators and workers to excavate safely, reducing the risk of damaging existing ducts. For newly installed ducts, AR can record and verify exact positions after burial. This can prevent future situations where the location of buried assets is unknown during maintenance inspections.

In this way, AR Construction Navi’s visualization of the site eliminates recognition gaps among workers and serves as a powerful guide to implement design intent as-is. Because workers can constantly compare the design model and actual conditions while working, mistakes can be corrected immediately, minimizing rework. This is the real-time construction verification unique to AR.

Furthermore, AR technology is beginning to play a role in the maintenance and management of signaling and communications equipment. For example, if crack locations on structures are recorded with AR markers, the exact same spots can be identified at the next inspection, helping to track long-term changes and prevent oversights. Examples have been reported where buried cable routes or internal layouts of signaling devices are displayed like cutaway views, allowing even non-experts to quickly locate faults. AR Construction Navi is expected not only as a tool for construction but also as a trump card for maintenance DX. There are also efforts to display warning signs or work procedures in AR in workers’ fields of view to prevent entry into hazardous areas and reduce human error.

Benefits of introduction – Preventing rework, improving safety, enabling remote collaboration

For example, in a certain railway signal replacement project, using AR Construction Navi to perform everything from stakeout to installation of signal poles resulted in measurement and marking of foundation positions—which used to take half a day—being completed in about 2 hours, and post-construction measurements showed almost no deviation from the design values, producing a highly accurate finish. The site supervisor commented, “Anyone could carry out the work without relying on a veteran’s intuition, and there was no rework,” reflecting the tangible effects.

Major construction companies and railway-related firms have already begun pilot deployments, and the following qualitative and quantitative benefits have been reported from the field.

• Dramatic reduction in construction errors and rework: Because workers can always refer to the design model in AR while working, the situation of “finding misalignment later” has been significantly reduced. Correct construction in one pass becomes possible, and the incidence of re-surveying and rework has dropped dramatically. On some sites, teams reported achieving zero rework after introduction, effectively eliminating remedial work due to quality defects. Preventing rework directly shortens schedules and reduces costs, contributing significantly to improved site productivity.

• Improved work efficiency and speed: Digital guidance reduces manual positioning and measurement tasks, shortening total work time. Tasks that previously required time for drawing confirmation or stake-driving can be completed simply by following on-screen instructions in AR, resulting in reports of 1.5×–2× faster work in some cases. Also, using AR screen screenshots directly in meeting materials and reports has reduced the workload for creating supplementary drawings and organizing photo ledgers. The freed-up capacity can be allocated to other tasks, enabling efficient operation even on sites facing labor shortages.

• Enhanced safety: Higher guidance accuracy and one-pass completion reduce unnecessary nighttime work and emergency corrective work. Time spent entering hazardous areas for surveying is also shortened, and the number of workers remaining on site can be reduced. Tasks that used to require two people may be completed by one, easing personnel allocation burdens. Because AR enables work while looking at the front-facing screen, the risk of neglecting attention to the ground is also reduced. On-site feedback includes “not having to stare down at paper drawings increased situational awareness and reduced near-miss incidents.” AR Construction Navi contributes to both safety and productivity.

• Remote collaborative work: The 3D models and positioning data handled in AR can be shared via the cloud, enabling distant experts to closely review site conditions. For example, a worker can livestream the tablet camera view with AR overlays while a remote technician provides instructions, enabling remote assistance. In one project, AR visuals were shared during a web conference to explain construction steps, allowing on-site reviews without travel. This reduces travel time and coordination costs and speeds up emergency responses. From the perspectives of infectious disease countermeasures and work-style reform, the ability to collaborate regardless of location is increasingly important.

• Smoother consensus building: Sharing the on-site image via AR among all stakeholders has significant communication benefits. When clients, site supervisors, and designers look at the tablet screen together, everyone understands the same completed image. Details that were difficult to convey on drawings become immediately clear, leading to feedback such as “meeting and explanation times have been greatly reduced” and “design intent mismatches are gone.” There are also trials of displaying AR models at full scale during community briefings to help local residents understand and support projects. Particularly on large projects, speeding up consensus building contributes greatly to smoother overall planning.

• More efficient report generation: With data digitized and aggregated on site, automatic report output is advancing. For example, LRTK cloud services now include functions to generate construction management reports with one click from measured point-cloud data and photos. Report creation that used to be done back at the office can be completed on site, reducing administrative burdens for site supervisors and preventing transcription errors when recording as-built data. Time required to prepare deliverables for electronic submission is also shortened, allowing time to be reallocated to other tasks. This also facilitates smooth compliance with electronic submissions to government agencies and improves transparency and reliability of construction records.

Conclusion – Toward the future of railway signaling and communications DX

The AR Construction Navi utilizing LRTK introduced here can be considered a key solution that strongly promotes DX in the railway signaling and communications field. By digitizing on-site work itself and raising safety, quality, and efficiency across the board, this technology will likely grow increasingly prominent. This is not just the adoption of a convenient tool but an initiative aligned with construction DX visions such as i-Construction promoted by the Ministry of Land, Infrastructure, Transport and Tourism. Especially in the face of labor shortages and an aging workforce, this easy-to-use smart construction tool has the potential to become a new on-site standard accessible to everyone. The simple system using a smartphone and a small antenna also lowers the barrier to introduction, making it easy to experience benefits in a short period and encouraging wider adoption.

AR Construction Navi’s applications are not limited to large-scale projects. It is expected to be useful for routine inspections, minor improvement works, and even simple surveying of infrastructure assets. For example, without relying on a veteran’s intuition, pointing a smartphone could instantly measure a structure’s tilt or installation deviation, or complete preliminary site surveys for work locations in a short time. Common uses include leaving AR markers at abnormal points discovered during regular patrols and sharing them, enabling DX tools to be naturally integrated into daily operations.

A time when the site and the digital are seamlessly fused in the world of railway signaling and communications is imminent. The future opened by combining AR Construction Navi and LRTK represents a new form of knowledge transfer that lets novices access experienced workers’ know-how early, and it marks a turning point toward a safer, more efficient infrastructure management system. Visualizing and sharing site know-how prevents the concentration of skills in a few individuals and supports the development of younger workers. In the longer term, integration with wearable devices such as smart glasses could enable hands-free confirmation of AR information while working. Moreover, accumulating on-site data toward digital twin recreation of the site in virtual space could enable applications such as AI-driven optimization of construction planning and predictive maintenance. By adopting these cutting-edge technologies on site, industry-wide DX will accelerate, leading to more resilient and smarter railway infrastructure. The wave of change is steadily reaching sites that once relied on paper drawings, and the day when XR technologies support everyday operations is not far off. Please consider applying this AR Construction Navi at your sites as well, and let us jointly promote the next generation of railway signaling and communications DX.