Labor-saving Achieved in Railway Construction: How LRTK’s High-Precision AR Guidance Is Changing Job Sites

Background: Why Labor-Saving Is Demanded in Railway Construction

On railway construction sites, high-precision work must be completed with limited personnel and time. In particular, the construction industry in Japan is facing a severe labor shortage, making it difficult to secure skilled workers. In addition, the strengthening of overtime regulations under the work-style reform laws in 2024 (the so-called “2024 problem”) has made efficiency improvements more important than ever to finish work within scheduled periods. In the railway sector, many projects rely on nighttime work to avoid disrupting train operations, but work must be completed within the short window between the last and first trains, so reducing work time while maintaining accuracy is a major challenge.

Railway infrastructure construction and maintenance also require millimeter-level precision control. For example, misalignment of tracks or signaling equipment directly affects safe operations, so surveying and layout work at the site has required advanced skills and care. However, experienced surveyors are aging and young personnel are scarce, and the traditional approach that depends on veteran intuition and experience may not sustain future work sites. Against this backdrop, there is growing demand in the railway construction world for labor-saving and improved operational efficiency through digitalization. The Ministry of Land, Infrastructure, Transport and Tourism is promoting “i-Construction 2.0,” which sets goals of 1.5× productivity and more than 30% labor reduction on construction sites by 2040, making the adoption of new technologies for construction DX (digital transformation) in railway works an urgent task.

Burden and Risk of Errors in Conventional Surveying and Layout Work

In railway construction, surveying and layout (marking) work for track laying and equipment installation are indispensable. For example, when erecting a new catenary pole, precise positions must be marked on the ground based on coordinates on drawings, and foundations or piles must be installed accordingly. Traditionally, such layout work used surveying instruments like total stations or transits mounted on tripods, with several people holding reflecting prisms to take measurements. Distances from the track were measured with tape measures and heights checked with levels, while markings were made by hand.

However, these conventional methods involve many burdens and risks. First, the work procedures are complex, and it takes time to establish each point. With the limited nighttime working window, time spent on surveying can squeeze the available time for actual construction. Second, manual measurements relying on human effort are prone to human error. Small reading mistakes of tape measures or visual checks in the dark, calculation errors, and other slight measurement inaccuracies can later lead to significant misalignments. For example, measuring a platform door position off by several centimeters could prevent alignment with train doors and require readjustment. Errors in track layout can cause deviations in rail curvature or gradient, leading to rework, schedule delays, or in some cases reduced safety.

Moreover, conventional surveying and layout work heavily depends on skilled personnel. Operating advanced surveying equipment and translating drawings to the field require experience, and novices often struggle to perform these tasks precisely. As a result, sites have had to rely on veteran technicians, concentrating workload on specific skilled workers amid personnel shortages.

To address these issues, efficiency gains using dedicated equipment have long been explored. For example, layout navigators (surveying devices dedicated to stakeout that allow a single person to stake out positions) are used on some sites as effective labor-saving devices. However, dedicated equipment is often expensive or requires time to master, creating barriers to adoption for small-to-medium-scale sites or beginners. Responding to the question “Is there a simpler method that anyone can use to stake out accurate positions?” a new solution combining smartphones and GNSS (satellite positioning) technology has emerged.

High-Precision Positioning and Visual Guidance with LRTK and AR Technology

Recently gaining attention is the fusion of smartphone-based high-precision GNSS positioning and AR (augmented reality) guidance. The key technology here is RTK (Real Time Kinematic) positioning. RTK corrects satellite positioning errors in real time and can determine current position with centimeter-level accuracy (cm level accuracy (half-inch accuracy)). Traditionally, RTK positioning required dedicated antennas, high-performance receivers, and radio communication between rover and base stations, but compact integrated devices have been developed in recent years. One such device is the pocket-sized RTK-GNSS receiver called LRTK. LRTK is an all-in-one positioning device that can be attached to a smartphone or tablet, allowing GNSS surveying with accuracy comparable to traditional surveying instruments simply by attaching it to a phone.

When the LRTK device is attached to a smartphone and the dedicated app is launched, the phone instantly becomes a high-precision positioning instrument. LRTK supports multiple satellite systems such as GPS, GLONASS, and Galileo, and can also receive the centimeter-class augmentation service (CLAS) signal provided by Japan’s quasi-zenith satellite “Michibiki.” As a result, even in environments where satellite visibility is somewhat limited—such as mountainous areas or under elevated structures—stable centimeter-level positioning (cm level accuracy (half-inch accuracy)) can be achieved, ensuring the high accuracy required in railway construction on site. The smartphone display loads pre-prepared design coordinate data (for example, planned locations of poles or piles) and shows real-time discrepancies from the user’s current position. For example, guidance like “0.05 m east, 0.10 m north to the target point” is displayed, so a worker can simply move according to those instructions to approach the target location (0.05 m (0.16 ft), 0.10 m (0.33 ft)). There is no need to measure distances with tape measures or calculate dimensions on drawings at the site— the smartphone provides navigation. Just as a car navigation system guides you to a destination, LRTK digitally assists layout tasks on site.

Furthermore, the LRTK app leverages AR functionality to overlay virtual arrows and markers on the smartphone camera feed. The system visually marks where installations should be and guides workers visually. For example, when pointing the camera, a marker indicating “drill hole here” may appear on the floor, or arrows may indicate the direction to move. Combining precise GNSS positioning with AR display allows projecting drawing coordinates onto the real world without offset. This enables intuitive navigation and accurate layout without relying on veteran intuition. Even novice workers without surveying expertise can reach the correct points by following on-screen instructions, greatly lowering the work threshold. In practice, the visual and easy-to-understand AR guidance helps workers’ spatial awareness and is expected to reduce rework caused by positional discrepancies.

Railway Construction Scenes Where High-Precision AR Guidance Excels

High-precision AR guidance using a smartphone plus LRTK is effective across many railway construction scenarios. Below are examples of specific use cases in railway construction.

• Track center layout: When laying new track or improving a curve, it is necessary to accurately establish the centerline of the rails. Traditionally, offsets from existing survey points were calculated and center positions marked on the ground with chalk. Using AR guidance, the designed track centerline is displayed on the smartphone screen, and workers simply place markers on the ballast along that line. Even in sections with curve radii or cant (cross slope), centerline layout can be performed with errors on the order of a few centimeters without compromise, improving both the precision and speed of rail installation.

• Platform door installation: In retrofit projects installing platform screen doors, the mounting positions of door units must be determined precisely, as deviations of only a few millimeters are not acceptable if they are to align perfectly with train doors. Traditionally, each unit’s position was measured and marked from reference points at the platform edge using a tape measure, but with AR guidance the installation positions can be displayed directly on the platform in AR. Workers align door units to the displayed frames, eliminating concerns about positional error. As a result, adjustment work is reduced and multiple doors can be installed smoothly even during nighttime work.

• Cable laying: Railway projects frequently involve burying or routing signal and communication cables along the track. Installing long cable routes correctly requires measuring distances and checking corners against drawings. High-precision AR guidance can visualize the designed route on the ground, allowing workers to intuitively identify trenching locations and conduit paths. For buried installations, the trench line can be displayed in AR, preventing unnecessary excavation or routing mistakes. Also, as it is necessary to avoid coming too close to existing buried pipes or structures, combining AR with pre-acquired surrounding 3D scan data makes the spatial relationship to obstacles immediately apparent, enabling safe and accurate cable installation.

• Catenary pole and signal installation: When erecting catenary poles (overhead line supports) or signals, accurate positioning including vertical placement is important. Normally, base positions are determined by measuring distance from the track centerline and elevation, but using AR guidance the foundation position can be projected based on the designated installation coordinates, speeding up positioning work. The ground location where a pole should be erected is displayed through the smartphone, so workers can confidently mark excavation sites or anchor bolt positions. When erecting multiple catenary poles at regular intervals, loading the design positions into the app allows AR navigation to guide each installation in sequence, enabling accurate layout even by a single worker. This reduces errors in pole spacing and tilt, improving overall catenary system quality. Similarly, for signal or level crossing equipment installation, AR can indicate the equipment base locations based on drawing coordinates, allowing faster and more accurate installation than before.

• Station equipment installation: AR technology is also useful for installing various station facilities (information displays, surveillance cameras, elevators, etc.). Station buildings and platforms often contain complex structures with many reference dimensions; if a 3D BIM (Building Information Modeling) model is available, LRTK’s AR function can overlay that model on the real environment. For example, when choosing the mounting position for an overhead information display while avoiding interference with ceiling beams or other equipment, projecting the optimal position determined in the BIM model into AR reduces trial-and-error adjustments. In confined station areas, equipment must be kept within the building gauge (the limit line for structure intrusion into the station interior). By displaying clearance lines and equipment models in AR beforehand, installers can confirm compliance and avoid post-installation “overhang” mistakes. Thus, AR-based visualization supports both interference checks in space and precise positioning for station equipment installation.

Concrete Effects: Shorter Work Time, Labor-Saving, and Improved Safety

Introducing high-precision AR guidance with LRTK is expected to produce various positive effects on railway construction sites. First is reduced construction time. With significantly less time spent on surveying and layout, more tasks can be completed within the limited nighttime work window. For example, layout work that traditionally took 2–3 people one hour from reference points might be completed by one person in just a few minutes using AR guidance. Faster positioning shortens the overall schedule and reduces impact on train operations, allowing work to finish with time to spare before the first trains.

Second is reduced dependence on skilled workers—that is, labor saving. With AR guidance, inexperienced workers can achieve accurate layouts, enabling construction to proceed without relying solely on veteran surveyors. As a result, sites can be operated with fewer people, reducing the burden of staffing and allowing more flexible work planning. This eases competition for limited skilled personnel at different sites and helps maintain stable construction capabilities despite labor shortages. Because work can be performed by following intuitive AR screen instructions, there is less need to spend long periods acquiring specialized surveying skills. This also facilitates early-stage practical training for newcomers, speeding up skill transfer.

Third is improved safety. If AR guidance reduces work errors, the likelihood of rework and emergency repairs decreases. In railway work, mistakes that lead to structural defects pose safety risks, so achieving high accuracy from the start is itself a safety measure. Also, enabling one person to perform surveying and installation efficiently reduces the number of personnel on site, which has safety benefits: fewer workers entering hazardous areas near tracks lowers the risk of being struck by trains or caught in heavy equipment operations. Shorter required work time also reduces exposure to extreme heat or cold, helping prevent heatstroke and other health issues. In fact, some sites report that even on extremely hot days, surveying can be completed more quickly than before, improving the work environment.

Progress Management and As-Built Inspection Through Point Cloud Data and BIM/CIM Integration

Solutions using LRTK also provide benefits in digital recordkeeping and quality inspection during and after construction. Using a smartphone’s LiDAR sensor or camera to scan a site allows acquisition of detailed point cloud data capturing surrounding conditions. Because LRTK corrects positions, the acquired point clouds and photos are tagged with accurate coordinates. These coordinate-tagged point clouds enable three-dimensional recording of track alignments, structures, and equipment, and can be managed in the cloud.

Acquired point cloud data can be overlaid and used with design BIM/CIM models or drawing data. For example, comparing a point cloud scanned during construction with the design model makes current progress immediately apparent—whether excavation is ahead of schedule or embankment heights match design. Progress management checks that previously required on-site measurements can now be performed digitally and intuitively. Also, for as-built inspections (verifying that finished structures and dimensions conform to design), this data is useful: dimensions can be measured on the point cloud or sections cut to compare with design cross-sections, streamlining inspection tasks that formerly required staff to repeatedly measure and record on site. For instance, after installing cable racks in a tunnel, scanning and comparing with the design model can confirm at once whether all support brackets are correctly positioned.

Furthermore, LRTK makes it easy to attach coordinate tags to photos taken with a smartphone, so the exact location of each photo is accurately recorded and later identification in the office is straightforward. Photos and point cloud data can be shared via the cloud in real time, enabling remote managers and clients to participate in digital inspections. It becomes realistic to immediately create as-built documentation and reports based on high-precision data collected on site. In this way, precise positioning with LRTK and data integration connects recording during construction through inspection and delivery, innovating quality control and documentation processes in railway construction.

Ease of LRTK Adoption and Usability on Site

When introducing new technology to job sites, usability and cost are key concerns. Smartphone-based surveying systems using LRTK offer major advantages in these respects. First, the required equipment is only a smartphone and a palm-sized LRTK device. Traditionally, achieving centimeter-level surveying required expensive GNSS receivers and mounting equipment costing several million yen, plus separate costs for 3D scanners. With LRTK, attaching a small receiver to a smartphone that many people already own greatly reduces initial investment. There is no need to purchase large dedicated equipment, and a small team can try a pilot implementation—making a small-start approach easy.

Portability is another practical advantage on site. A smartphone plus LRTK is compact enough to fit in a pocket, eliminating the need to carry heavy tripods or surveying instruments along the track. For long sections, workers can collect necessary data while walking with a smartphone in hand. The device’s battery is built in and designed for long use on site. Since setup time is minimal, workers can respond quickly in situations where speed or frequent relocation of setup points is required.

In addition, ease of operation is important. LRTK apps are designed to be intuitive, so users do not need to remember specialized terms or complex settings. On-screen guidance and button operations are easy to understand, and short training enables anyone to operate the system. AR instructions are simple and clear, so even those unfamiliar with site work can act without hesitation. If a user is unsure, office staff can remotely verify and support position information through the cloud. In other words, LRTK can become an immediate asset on site, with low psychological and technical barriers to adoption.

Durability and environmental resilience are also important for field equipment, and LRTK devices are robustly designed for outdoor use. They operate reliably in light rain, wind, and dust, and are engineered to maintain stable positioning accuracy across extreme summer and winter temperatures. This allows confident use in the harsh environments typical of railway construction. Overall, LRTK adoption is achievable with the simplicity of “all you need is a smartphone,” and its on-site usability is well established.

Conclusion: A New Style of Railway Construction Brought by LRTK

Facing issues such as severe labor shortages and constraints on nighttime work, LRTK’s high-precision AR guidance is a trump card technology for labor-saving in railway construction. This system, which achieves centimeter-level positioning and intuitive AR navigation with a single smartphone, is overturning conventional practices and fundamentally changing how field work is performed. A time may be near when anyone can handle surveying and layout with a smartphone in hand and proceed with construction driven by data.

Introducing tools like LRTK shifts work that once relied on experience and intuition toward data-backed, reliable construction. This represents a move from artisanal, person-dependent skills to reproducible digital construction methods that can be executed by whole teams. While gaining efficiency, labor savings, and safety improvements, overall quality can also be elevated. This trend aligns with national efforts to drive DX on construction sites and benefits all stakeholders involved in maintaining and building railway infrastructure.

When job sites change, ways of working change too. Freed capacity from labor-saving measures can be redirected to other tasks and workforce development, boosting organizational productivity and technical capability. Simple surveying and AR-assisted construction with LRTK is a powerful ally for achieving “fast, accurate, and safe sites.” Adopting these advanced technologies early as a future vision for railway construction will directly support competitiveness going forward. Let’s bring high-precision AR guidance to the field quickly and achieve both labor-saving and quality improvement.