Overhead lines are a lifeline that supplies power to railways and are also a major artery of the power network—critical infrastructure for society. Inspections to maintain their integrity are indispensable, but aren’t those tasks often a heavy burden for people working on site? High-altitude hazardous work, limited working hours late at night, and excessive labor due to staff shortages—there are many challenges at sites handling overhead lines. For example, on railways, maintenance of overhead line equipment must be carried out for only a short time after the last train at night. Working in protective gear is grueling even in summer, and in the dead of winter it’s a battle against extreme cold. Workers are always at risk of falling or electric shock, and meticulous care and effort are devoted to ensuring safety. Likewise, in power transmission line construction and inspection, climbing towers dozens of meters high and relying on lifelines for work is unavoidable. In such environments where a momentary lapse can lead to a serious accident, safety measures are thorough, down to attaching fall-prevention tethers to each tool. Nevertheless, risks from natural conditions—strong winds, lightning, and the like—always raise the tension on site. In addition, highly skilled technicians who are adept at high-altitude work tend to be older, and chronic labor shortages are severe. With limited personnel responsible for vast amounts of equipment, there is a strong demand on site for greater efficiency and improved safety.

In traditional overhead-line inspections, not only is the work itself demanding, but the measurements and record-keeping that accompany inspections are also burdensome. Maintenance of overhead lines (railway contact wires and transmission lines) requires regular inspection of wire wear, sag, loosening or damage to support fittings, and measurement to ensure that overhead line heights and clearance distances from surrounding structures fall within prescribed values. If these are not accurately understood and appropriately addressed, safe railway operation and stable power transmission could be compromised. Therefore inspections cannot be neglected, but they have traditionally required enormous effort and time. Processes such as height measurements 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, surveying equipment like total stations is used to set out the positions of overhead-line poles, but that also requires expertise to install and operate the instruments and typically involves multiple workers. In remote mountain sections of transmission lines, travel to the site can take a long time, and even after arrival poor communications can make contacting headquarters difficult—another inefficiency.

To improve these harsh conditions, recent efforts have begun to use robots and drones for unmanned automation. However, such solutions often require expensive specialized machines and complex operation, creating barriers to widespread on-site adoption. This is where LRTK technology, introduced as a more accessible solution that can change conventional on-site practices, draws attention. This new approach using smartphones promises a revolution in overhead-line inspections—here’s how it can transform the field.

Challenges in conventional overhead-line inspection and surveying

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

• Safety risks of high-altitude work: Work at height always carries serious dangers such as falls and electric shocks. Night work limits visibility at workers’ feet, requiring intense concentration. Even with full precautions like harnesses (lifelines) and insulated protective clothing, a small mistake can lead to an accident. Great care is also required for placement of bucket trucks and scaffolding, and the tension on site remains high.

• Labor and time burden: On railways, work can only be done at night when trains are stopped, meaning the available work time is limited to the few hours between the last and first trains. Completing work efficiently requires multiple workers, including veterans, which increases labor costs and hours under constraint. For power line construction, a small crew must cover wide areas, limiting the amount of work that can be done in a day. In remote sites, travel alone can consume most of the schedule.

• Measurement errors and reliance on individuals: Traditional measurements depend heavily on the intuition and experience of skilled personnel, introducing risks of manual measurement error and lapses in recordkeeping. For example, the accuracy of overhead-line height measurements depends on the worker correctly positioning a measuring rod. Pass/fail judgments of inspection results also tend to rely on individual judgment, so assessments may vary when personnel change.

• Difficulty in data utilization: Inspection and surveying results are often recorded by hand on paper checklists or drawings, and the collected information frequently remains locked away in on-site files. Comparing with past data or sharing with other departments is time-consuming, so the insights gained on site are not fully leveraged.

Leaving these issues unresolved leaves the future of infrastructure maintenance management uncertain. A system that can acquire and share high-accuracy data safely and efficiently is needed—this is where LRTK technology comes in.

New overhead-line inspection methods enabled by LRTK technology

LRTK is a cutting-edge technology that enables centimeter-level positioning, 3D scanning, and AR (augmented reality) work assistance using a smartphone. By attaching a compact GNSS receiver to a smartphone and applying RTK (real-time kinematic) correction to satellite positioning errors in real time, LRTK reduces GPS positioning errors from meters to just a few centimeters horizontally and vertically. This allows accurate position awareness on map coordinates while on site. By linking with a smartphone’s built-in LiDAR (light detection and ranging sensor) and camera, it can convert the surrounding environment into 3D data on the spot and display virtual guidance overlays. The revolutionary aspect of LRTK is that functions that previously required separate specialized instruments—high-precision GNSS units, 3D laser scanners, total stations—can now be consolidated into a single smartphone that fits in your pocket. For example, high-precision surveying once required large tripod-mounted GNSS receivers or total stations, but with LRTK equivalent positioning can be achieved with just a smartphone and a small receiver.

Specifically, here are the main functions LRTK brings to overhead-line inspections:

• Centimeter-level position measurement: Using LRTK, you can instantly obtain coordinates of the point you want to measure with a smartphone. For example, you can measure the installation positions of overhead-line poles or height reference points on site and immediately save latitude, longitude, and elevation data. There is no need to carry heavy surveying equipment and spend long hours measuring; a single person can quickly perform high-precision positioning at multiple points. Measurement results are plotted on a map for on-site confirmation, making it easy to decide immediately whether additional measurements are needed and reducing rework. LRTK supports network RTK correction information and the QZSS (Michibiki) CLAS signal, allowing it to maintain centimeter-level accuracy even in environments where conventional RTK positioning was difficult, such as under forest canopies or overpasses.

• Fast acquisition of 3D point cloud data: By walking around the site with a LiDAR-equipped smartphone in hand, you can capture the surrounding terrain and structures as 3D point cloud data. Because LRTK continuously corrects the device’s position, it suppresses distortions and positional shifts commonly seen during scans and enables creation of accurate 3D models in a short time. You can record overhead lines and poles as well as surrounding tunnels and buildings in three dimensions and later measure distances or heights at any point from the captured point cloud. 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. Areas around structures that were hard to see previously can be comprehensively understood by viewing the point cloud from above, helping to detect deterioration or problematic spots. LiDAR sensors also perform well in low-light conditions, making them reliable for nighttime inspections.

• AR work navigation: AR is another major attraction of LRTK. Through the smartphone screen, digital information can be overlaid on the real-world view. For example, a “coordinate navigation” feature that guides you to a pre-registered target point with arrows or markers lets less experienced personnel reach their destination without getting lost. AR can pinpoint specific locations—such as the foundation of a particular pole or a spot that had a problem in the previous inspection—so that even at night you can immediately tell which point to inspect. You can also project the design’s building limits or equipment 3D models onto the site to visually check whether overhead lines and structures fall within the required clearances. Because you can directly compare the ideal state with the current situation through the phone instead of mentally overlaying drawings, AR helps prevent work errors.

• Cloud-linked data sharing: Survey data and inspection records acquired with an LRTK app can be uploaded to the cloud on the spot. With an internet connection and the press of a button, point cloud data, photos, and coordinate lists can be synchronized to the company cloud, making it easy for remote teams to view and share information on a PC. Point clouds can be viewed in a browser without special software, enabling headquarters specialists to check site-obtained data in real time. By combining cloud services, accumulation and utilization of inspection results become smooth.

The introduction of LRTK digitizes many of the processes in overhead-line inspection that previously required significant manpower and time. Reducing dangerous high-altitude work to the minimum while enabling safe data collection from the ground is a major advantage for on-site teams. Because measurements can be performed easily by a single person, the burden of arranging heavy machinery like aerial work platforms or traffic control for roads is also reduced. Moreover, an LRTK phone combines the functions of surveying instrument, 3D scanner, camera, and navigation device, making it more economical than equipping multiple specialized devices and lowering the barrier to adoption; its ease of use—ready whenever needed—is another attraction. Since a smartphone app allows intuitive operation, precise inspections can be performed even by non-experts. This is truly a change on the ground that deserves to be called a “revolution” in overhead-line inspections!

On-site use cases: scenarios for improved safety and efficiency

LRTK has already begun to be used in Japan’s railway and power sectors, and many benefits have been reported from the field. Here are representative scenarios showing the concrete effects LRTK can achieve in overhead-line inspections.

• Efficiency and accuracy improvement of routine inspections: At railway maintenance sites, position information for poles and cable equipment is pre-measured and digitized with LRTK, and the points are then used to accurately navigate to inspection locations during routine checks. Inspecting the same points every time prevents oversights and omissions across years of surveys. For example, if coordinates of cable boxes or poles along the track are recorded, the LRTK app will guide inspectors to the same spot on subsequent patrols. Even at night with poor visibility, workers can locate the target pole by following arrows displayed on the phone screen, significantly shortening 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 and reducing reliance on experienced intuition, thereby helping to standardize quality regardless of who conducts the inspection.

• Recordkeeping and quality control before and after construction: LRTK is also useful for installing or replacing overhead lines. Scanning the site to create a detailed as-built 3D model before work allows careful construction planning. During construction, AR can visualize the locations of poles and arms shown on design drawings on the ground to prevent misplacement of piles or incorrect installation of components. For instance, by virtually marking “install pole here” on the ground via AR, the need to repeatedly set up physical markers or scales is reduced. After completion, rescanning the site with LRTK lets you verify in the data whether the heights and positions of the finished overhead-line equipment match the design. This ensures rapid, reliable quality checks and makes it possible to record changes by comparing pre- and post-construction 3D data. Collected point clouds and positioning data stored in the cloud can be shared with stakeholders for review or appended to reports for easy secondary use.

• Remote situational awareness and coordinated response: LRTK also serves as a bridge between field and office. Consider an anomaly on a transmission line route in a mountainous area. Previously, HQ often had to make decisions based on fragmented radio reports or photos from the field, but with LRTK the site situation can be shared in three dimensions. A worker can shoot a problem area with their phone while simultaneously logging its position and, if necessary, scanning the surroundings in 3D and uploading to the cloud. Office engineers can immediately review the data in 3D and understand the on-site situation. This allows field and remote staff to discuss appropriate responses using the same data, speeding decisions on additional material orders or dispatching reinforcements and greatly reducing initial response time. Being able to “virtually” reproduce the site even from afar strengthens teamwork in infrastructure maintenance.

• Application to asset management: Precise data collected with LRTK is useful for 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 anomalies can be identified and prioritized for replacement or repair. Quantitative data enables judgments on optimal timing for maintenance or replacement, allowing limited budgets and personnel to be allocated strategically for efficient maintenance. If LRTK becomes established as a field data collection tool, it will greatly contribute to visualizing infrastructure assets overall and optimizing long-term maintenance management.

Users who have actually used LRTK report feedback such as, “At first I was skeptical that you could really do surveying with a smartphone, but I was surprised at the accuracy. With this we can cut night work in half,” reflecting the field’s amazement at the difference from traditional methods. Others say, “Dangerous high-altitude tasks have decreased and the mental burden has been reduced,” attesting to the safety benefits. As described above, using LRTK for overhead-line inspections and construction management is beginning to yield significant results in both safety and efficiency. Partial automation of inspections and centralized data management are changing on-site workflows themselves.

Conclusion

Incorporating LRTK technology into overhead-line inspections is poised to greatly reduce the labor and risks that have long been taken for granted. Precise data obtainable without climbing to height protects workers’ safety and directly shortens night work hours and reduces staffing needs. Because consistent results can be achieved without relying on veteran experience, the industry can confidently prepare for generational transitions. Once collected, data is stored in the cloud and is useful for time-series comparisons and stakeholder information sharing. Compared with the era of paper records and oral transmission, retaining on-site expertise as digital assets is a major advantage.

The use of such digital technologies is being promoted by governments and companies as DX (digital transformation) for infrastructure maintenance management. Methods like LRTK are exactly the concrete measures expected from the field. It should also be noted that they are versatile and applicable beyond overhead-line inspections—for example, simple as-built surveying in civil engineering works or photo records during equipment inspections can be handled with the same system. The convenience of quickly taking out a device and surveying when needed will strongly support DX across sites.

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

Even in the realm of overhead-line inspection—where people have long sweated and faced danger—a new breeze of digital technology is beginning to blow. The new method for improving safety and efficiency with LRTK holds great potential to transform how work is done on site. The new era of overhead-line inspections is almost here. Please take a look at this revolutionary solution and join us in envisioning the future of overhead-line management.