Overhead lines are the lifeline that supplies power to railways and are an important infrastructure that serves as a major artery in the power grid. Inspections to maintain their integrity are indispensable, but aren’t these tasks always a heavy burden for workers on site? Dangerous work at height, very limited working hours during late-night periods, and excessive workloads due to labor shortages—all of these problems exist where overhead lines are handled. For example, on railways, maintenance of overhead line equipment must be performed for only a short time late at night after the last train. Working in protective gear is harsh even in summer, and in the dead of night in winter it is a battle against extreme cold. Workers are always exposed to the risk of falls and electric shock, and utmost care and effort are required to ensure safety. Meanwhile, in power transmission line construction and inspection, climbing towers tens of meters (tens of ft) high and relying on lifelines is unavoidable. At sites where a momentary lapse could lead to a serious accident, safety measures are taken down to attaching tethers to each tool to prevent dropping. Even so, natural conditions such as strong winds or lightning pose risks, and tension at worksites remains high. In addition, technicians who are experienced in high-altitude work tend to be aging, and chronic labor shortages are severe. To maintain vast facilities with limited personnel, there is a strong need on site for improved efficiency and enhanced safety.

In traditional overhead line inspections, not only is the work itself demanding, but the burden of measurements and record-keeping that accompany inspections cannot be overlooked. In maintenance of overhead lines (such as railway contact lines and transmission lines), periodic inspections check wire wear, sag, looseness or damage of support fittings, and measure whether overhead line height and clearance distances from surrounding structures fall within specified values. If these are not accurately understood and properly addressed, they can impair safe railway operation or stable power transmission. Therefore, inspections cannot be neglected, but the work originally required enormous effort and time. Processes such as height measurement using measuring rods or laser rangefinders, visual checks, and recording results on paper to later reflect on drawings are labor- and time-intensive. In some sites, total stations and other surveying instruments are used to set out overhead line poles, but these also require setup and operation expertise and typically assume multiple personnel. In remote mountainous transmission-line sections, reaching the site can take a long time, and even after arrival poor communications can make contact with headquarters difficult—another inefficiency.

To improve these harsh conditions, recent efforts have begun to use robots and drones for unmanned and automated operations. However, many cases require expensive dedicated machinery or complex operation, making widespread on-site adoption difficult. What is attracting attention as a more accessible solution that can change on-site norms is the newly emerged LRTK technology. This smartphone-based new method promises to bring a revolution to overhead line inspection sites—here’s how.

Problems with Conventional Overhead Line Inspection and Surveying

Let’s organize the challenges that inspection sites for overhead lines have faced.

• Safety risks in high-altitude work: Work at height always involves serious dangers such as falls and electric shock. Night work is especially demanding because footing is dark and workers must maintain high concentration. Even with thorough measures such as wearing safety harnesses (lifelines) and insulated protective clothing, a small mistake can lead to an accident. Careful attention is also required when setting up bucket trucks or scaffolding, and the sense of tension on site never fully eases.

• Burden of personnel and time: On railways, work can only be done late at night when trains are stopped, and working hours are limited to the few hours between the last and first trains. To complete tasks efficiently, multiple workers including veterans are required, increasing labor costs and confinement time. For power line works, wide-area jobs must be handled by small teams, limiting the amount of work that can be done in a day. In distant sites, travel alone can consume most of the schedule.

• Measurement errors and dependence on individuals: Conventional measurements rely heavily on the judgment and experience of skilled workers, so manual measurement errors and missed recordings can occur. For example, accuracy of overhead line height measurements depends on whether the worker can correctly place the measuring rod. Also, pass/fail judgments on inspection results tend to depend on individual subjectivity, and evaluations can vary when personnel change.

• Difficulty in data utilization: Inspection and survey results are often recorded by hand on paper check sheets or drawings, so collected information tends to remain dormant in onsite files. Comparing with past data or sharing with other departments is laborious, and site knowledge is not fully leveraged.

With such issues unresolved, uncertainty remains for the future of infrastructure maintenance. A system that can obtain and share high-accuracy data safely and efficiently is needed—this is where LRTK technology comes in.

A New Overhead Line Inspection Method Enabled by LRTK Technology

LRTK is a cutting-edge technology that enables centimeter-level positioning (half-inch accuracy) and 3D scanning using a smartphone, along with AR (augmented reality) work assistance. By attaching a compact dedicated GNSS receiver to the smartphone and applying RTK (real-time kinematic) corrections to satellite positioning errors in real time, the GPS positioning errors that used to be several meters can be reduced to only a few centimeters (a few in) in both horizontal and vertical axes. This allows accurate positions to be determined on map coordinates while on site. Furthermore, by integrating the smartphone’s built-in LiDAR (light detection and ranging sensor) and camera, the surrounding environment can be turned into 3D data on the spot, and virtual guide displays can be shown. It is revolutionary that the functions of specialized equipment that were previously used separately—high-precision GNSS units, 3D laser scanners, total stations—can be combined into a single smartphone that fits in your pocket with LRTK. For example, high-precision surveying used to require large equipment like GNSS receivers mounted on tripods or total stations, but LRTK can achieve equivalent positioning with only a smartphone and a small receiver.

Specifically, here are the main functions LRTK brings to overhead line inspection.

• Centimeter-level positioning (half-inch accuracy): With LRTK, you can instantly obtain coordinates of the point you want to measure with a smartphone. For example, the locations of overhead line poles or height reference points can be measured on site and immediately saved as latitude, longitude, and elevation data. There is no need to carry heavy surveying equipment and spend long hours; a single person can perform high-precision positioning at multiple points in succession. Measurement results are immediately plotted on a map for on-site confirmation, making it easy to decide on the spot whether additional measurements are necessary, thereby reducing rework. LRTK also supports network RTK correction information and the QZSS “Michibiki” CLAS signal, maintaining stable centimeter-level positioning (half-inch accuracy) even in environments where traditional RTK was difficult, such as inside forests or under viaducts.

• Rapid acquisition of 3D point cloud data: By walking around the site holding a LiDAR-equipped smartphone, you can acquire surrounding terrain and structures as 3D point cloud data. Because LRTK continuously corrects the device’s position, distortions and positional shifts that often occur during scanning are suppressed, enabling high-accuracy 3D models to be obtained in a short time. Overhead lines and poles, as well as surrounding tunnels and buildings, can be recorded three-dimensionally, allowing distances and heights at arbitrary locations to be measured later on the point cloud data. For example, clearances between overhead lines and the ground—which are difficult to measure directly from the ground—can be easily checked on the acquired 3D data. Structures around hard-to-see areas can be grasped without blind spots by viewing the point cloud from above, helping to detect deterioration and problem areas. Also, LiDAR sensors perform well in dark conditions, so shape data around the site can be reliably acquired during night inspections.

• AR-based work navigation: AR functionality is another major attraction of LRTK. Digital information can be overlaid on the real-world view through the smartphone screen. For example, using a “coordinate navigation” feature that guides you to a pre-registered target point with arrows or markers allows even inexperienced personnel to reach the intended spot without getting lost. Because AR can indicate pinpoint locations such as the foundation of a specific pole or a spot that had a previous defect, you can immediately see “which spot to inspect” even at night. It is also possible to project design clearance limits or 3D models of equipment onto the site to visually check whether overhead lines and structures are within prescribed clearances. You no longer need to mentally compare drawings; by overlaying the ideal state and the current situation through the smartphone, mistakes can be prevented.

• Cloud integration for data sharing: Survey and inspection data acquired by the LRTK app can be uploaded to the cloud on the spot. With an internet connection, a single button press syncs point cloud data, photos, and coordinate lists to the company cloud, making it easy to view remotely on a PC or share information within the team. Because 3D point clouds can be viewed in a browser without special software, headquarters specialists can immediately check information acquired on site, achieving real-time collaboration. Combining cloud services in this way enables smooth accumulation and utilization of inspection results.

By introducing LRTK, various processes in overhead line inspection that previously required manpower and time are digitized. Reducing dangerous high-altitude work to the minimum while collecting data safely from the ground is a major benefit for sites. Because measurements are easy to perform by a single person, the burden of arranging heavy machinery such as aerial work platforms or traffic control for road closures is also reduced. In addition, a single LRTK phone can serve as a survey instrument, 3D scanner, camera, and navigation device, making it more economical and lowering the barrier to entry compared to acquiring multiple dedicated devices; its ready-to-use convenience is another attraction. Advanced surveying can be performed by an intuitive smartphone app, so precise inspections can be conducted even without experts. This is truly a change worthy of being called a “revolution” in overhead line inspection, and it has already begun to appear on worksites!

On-site Use Cases: Scenarios for Improved Safety and Efficiency

LRTK is already being used in the domestic railway and power sectors, and many benefits have been reported from sites. Let’s look at some representative scenarios and the concrete effects LRTK can produce in overhead line inspection.

• Streamlining regular inspections and improving accuracy: In railway maintenance sites, the positions of poles and cable equipment are pre-measured and datafied with LRTK, and the system is starting to be used to accurately navigate to those points during regular inspections. Inspecting the same points each time prevents oversights and missed checks even across years. For example, if coordinates of cable boxes or poles along the track are recorded, the LRTK app will guide inspectors to the same spots during the next patrol. Even in poor visibility at night, simply following arrows displayed on the smartphone screen lets workers identify the target pole, significantly reducing inspection time. At each inspection point, previously taken photos and records can be reviewed on the spot, making it easier to notice trends or changes in abnormalities. Reliance on veteran intuition is reduced, helping ensure consistent quality regardless of who performs the inspection.

• Record keeping and quality control before and after construction: LRTK is also useful for new installation or replacement of overhead lines. If the site is scanned into a point cloud before work begins, a detailed 3D current-state model enables thorough construction planning. During construction, AR can visualize the positions of poles and brackets indicated in the design at the actual site, preventing misalignment of piling positions or mounting errors. For example, workers can perform virtual marking like “a pole here” on the ground via AR, eliminating the need to repeatedly set up rods or markers. After construction is complete, a re-scan with LRTK can verify on data whether the heights and positions of the completed overhead line equipment match the design. This not only allows reliable and speedy quality checks but also makes it possible to record changes by comparing pre- and post-construction 3D data. Point cloud and positioning data are saved in the cloud so stakeholders can share them for reviews or attach them to reports, enabling easy secondary use.

• Remote situational awareness and coordinated work: LRTK also serves as a bridge between the field and the office. Consider an abnormality on a transmission line route in a mountainous area. Previously, the office had to make judgments based on radio reports or photos from the field, which provided only fragmentary information. With LRTK, the situation on site can be shared three-dimensionally. A worker can photograph the problem area with a smartphone while measuring its position and, if needed, 3D-scan the surroundings and upload to the cloud. Office engineers can immediately check the data and grasp the situation via a 3D view. This enables on-site and remote staff to discuss appropriate countermeasures using the same data, speeding decisions on additional material procurement or dispatching reinforcement personnel and greatly shortening initial response times. Being able to virtually reproduce the site from afar strengthens teamwork in infrastructure maintenance.

• Application to asset management: Precise data collected with LRTK can also support corporate asset management and maintenance planning. If coordinates and inspection histories for all poles and related equipment are centrally managed in the cloud, areas with advanced aging or frequent abnormalities can be identified and prioritized for renewal or repair. Quantitative data supports decisions on optimal timing for maintenance or replacement, enabling strategic maintenance that efficiently allocates limited budgets and personnel. If LRTK becomes established as the field data collection tool, it will greatly contribute to visualizing infrastructure assets and optimizing long-term maintenance.

Users who actually used LRTK reported comments such as “At first I was skeptical that a smartphone could really do surveying, but I was surprised at the accuracy after using it. With this, we can halve our night work,” and sites have welcomed the difference. Others reported, “Dangerous high-altitude work has decreased and mental burden has been reduced,” experiencing safety benefits. As described, LRTK-based overhead line inspection and construction management are beginning to deliver significant results in both safety and efficiency. Partial automation of inspection tasks and centralized data management are changing on-site workflows themselves.

Conclusion

By incorporating LRTK technology into overhead line inspection, the traditionally accepted burdens and risks can be greatly reduced. Precise data obtainable without climbing high protects workers and directly contributes to shorter night working hours and reduced staffing. Because reliable results can be produced without relying on veteran experience, organizations can more confidently prepare for future generational transitions. Also, once data are acquired they are accumulated in the cloud, aiding time-series comparisons and information sharing among stakeholders. Compared with the era of paper records and oral transmission, being able to preserve on-site knowledge as digital assets is a major strength.

The use of such digital technologies is being promoted by governments and companies as DX (digital transformation) of infrastructure maintenance. Methods like LRTK are precisely the concrete measures that on-site personnel expect. It is also worth noting the versatility that allows flexible application beyond overhead line inspection—for example, simple as-built surveys in civil engineering or photo documentation during equipment inspection can be handled by the same system. The convenience of being able to quickly take out a device and survey when needed will strongly support DX across worksites.

Looking ahead, applications are anticipated in which AI analyzes the vast data collected by LRTK to automatically detect signs of deterioration or abnormalities. By combining craftsmen’s field skills with data science, infrastructure maintenance will evolve into smarter, more proactive preventive care.

A new breeze of digital technology has begun to blow through the domain of overhead line inspection, where people once toiled and faced danger. The new LRTK-based method for improving safety and efficiency has the potential to greatly change how people work on site. The new era of overhead line inspection is just around the corner. Why not take a look at this revolutionary solution and envision the future of overhead line management together?