LRTK Revolutionizing Kilometerage Management in Railways – Improving Safety and Efficiency with High-Precision Positioning

What is kilometerage management in railways?

In railways, the indicator used to show a position along a line is called the kilometerage (kilo-tei). Kilometerage expresses the distance from the line origin in kilometers and is, in a sense, the railway version of an address. For example, the notation "12k345" indicates the point 12.345 km (40501.969 ft) from the origin. Distance markers (kiloposts) are installed along the track at intervals such as every 100 m (328.1 ft) or every 1 km (3280.8 ft), and on site personnel use those numbers to identify the locations of equipment and trains. Kilometerage management means organizing and managing information such as railway equipment locations, work locations, and accident/failure sites based on this kilometerage.

This concept of kilometerage has been used since the early days of railways and still functions as a common positional reference across national rail networks. Kilometerage management is extremely important for railway operation and maintenance. From an operational perspective, train timetables and the placement of signal equipment are designed according to kilometerage. When a driver or dispatcher receives a report like "an abnormality occurred at XX Line, at around XX km," they can immediately picture the site and begin responding. In maintenance and inspection, the locations of rails, overhead lines, and civil structures as well as defect locations are all recorded by kilometerage. Because everyone can share a common reference of what is happening at which location, coordination among field crews, the control center, and various departments becomes smooth.

Field issues in kilometerage management

Even though kilometerage management has been used for many years in railway maintenance, several issues have been pointed out. The main ones are as follows.

• Recording shifts and errors: Kilometerage is supposed to be the measured distance along the route, but line improvement works and long-term track displacement can cause subtle mismatches between the recorded kilometerage and actual positions on the ground. Traditionally, kilometerage was calculated using tape measures or wheel-type distance meters, but small measurement differences accumulate over long distances and the errors grow. As a result, a sign that should be 10 m (32.8 ft) ahead in the records can end up being 15 m (49.2 ft) ahead in reality.

• Locating positions during abnormalities: When an accident or equipment abnormality occurs, the first requirement is to accurately identify the site. However, at night or in bad weather with poor visibility, distance markers can be overlooked or misread. In fact, at night recovery sites you sometimes see crews using flashlights to find distance markers while confirming positions. Relying only on kilometerage displays to search the site can lead to small visual errors that delay response and impair safety. In emergencies where seconds count, ambiguity about location increases on-site risk.

• Degradation of positional accuracy in asset ledgers: Railway companies register the installation locations of equipment in asset ledgers (infrastructure asset databases) by kilometerage. However, if rail replacement or gradient changes occur over years without precise re-surveys each time, discrepancies arise between the positions in the ledger and the actual positions. If left unaddressed, inconsistencies appear when comparing drawings or maps with ledger data, which can cause rework during planning or construction. As a result, crews may waste time searching for the intended equipment at the site or almost begin excavating the wrong location—close-call incidents that are a headache for managers.

As described above, conventional kilometerage management relies heavily on the intuition and manual work of experienced field staff, making it increasingly difficult year by year to maintain the accuracy and consistency of data. So how can these issues be addressed?

Effects of high-precision GNSS (RTK) positioning on precise kilometerage management

Recently, the use of high-precision GNSS positioning has attracted attention as the trump card for solving these problems. Among these, the RTK (Real Time Kinematic) method is a technology that corrects satellite positioning errors in real time to determine positions with astonishing accuracy within a few centimeters. The absolute coordinates (latitude, longitude, height) obtained by RTK can complement and strengthen the traditional kilometerage-based relative position indication as high-precision digital information.

Introducing RTK positioning into kilometerage management can produce the following effects.

• Improved location accuracy: Standalone GPS previously had errors of several meters, but RTK, using correction information, can reduce horizontal and vertical errors to about 1–2 cm (0.4–0.8 in). For example, in Japan, using centimeter-level positioning augmentation services (e.g., CLAS) provided by the QZSS "Michibiki" (centimeter-level accuracy (half-inch accuracy)), RTK-compatible devices can achieve high-precision positioning anywhere nationwide. This makes it possible to accurately associate world geodetic coordinates with any point on the track and instantly grasp the difference from the kilometerage display. Even slight positional deviations are not overlooked, allowing maintenance work to pinpoint target points. Discrepancies of tens of centimeters that used to arise when joining separately surveyed datasets can be resolved by having a common coordinate reference.

• Data unification and integration: Coordinates acquired by RTK can be linked to kilometerage information. For example, if a track inspection car collects rail deformation data and absolute coordinates are tagged to each point, defect locations can later be plotted accurately on a map and cross-referenced with other geospatial information. If kilometerage-based data and map coordinate system data match, centralized management of railway asset information on GIS or digital twins becomes easy. Because ledger updates can be based on coordinates, sharing location information across departments becomes smoother and human errors decrease. In one trial, an RTK receiver mounted on a running inspection car added absolute coordinates to track displacement data obtained every 25 m (82.0 ft) with an error within 3 cm (1.2 in). This means that dynamic data acquisition and integration with map information, which was previously difficult, has become practical.

• Improved safety and response capabilities: High-precision location awareness is powerful for safety measures and emergency response. For example, after heavy rain or an earthquake damages equipment, workers carrying RTK-compatible receivers can measure and report the positions of damaged spots to centimeter accuracy immediately. Traditional reports based on experience like "about X meters from the entrance of tunnel No. Y" become quantitative information such as "near tunnel entrance (kilometerage XXk+XXX), world coordinates (E, N) = (...)", so all related parties recognize positions by the same standard. As a result, initial responses are faster and instructions are more precise, greatly improving on-site safety. There are reports where, at an earthquake-damaged site, RTK was used to measure track displacement over an area at the centimeter level and to immediately identify which sections should be prioritized for repair. RTK thus brings major benefits in both accuracy and speed not only in normal times but also for post-disaster track inspections.

In this way, high-precision GNSS technologies such as RTK dramatically improve the accuracy and reliability of kilometerage management. However, actual field use requires dedicated equipment and operational methods. This is where the solution called "LRTK", which enables easy RTK positioning in combination with a smartphone, comes in.

Workflow for kilometerage inspection and recording using a smartphone + compact receiver with LRTK

LRTK (pronounced "el-are-tee-kay") is a compact RTK-GNSS receiver device that can be attached to a smartphone or tablet. This chapter describes a typical workflow for kilometerage inspection and recording using LRTK.

• Preparation and setup: The worker mounts the LRTK receiver on a dedicated smartphone attachment and connects it to the smartphone via Bluetooth or a wired connection (USB, etc.). The receiver itself is lightweight—on the order of several hundred grams—and does not burden transport. Before heading to the site, the app is launched and configured to access RTK reference station data (network-type correction services or CLAS signals from the quasi-zenith satellite, etc.). In tens of seconds the GNSS satellites are acquired and high-precision positioning is ready.

• On-site position measurement: Move to the inspection point or the equipment to be checked and start positioning. The LRTK receiver is integrated with the smartphone, and when necessary it can be mounted on a dedicated monopod (pole) and placed at the point to be measured. By simply tapping a button on the smartphone, the latitude, longitude, and height of that point are measured. The smartphone screen displays current coordinates and precision indicators in real time, allowing the operator to confirm stability during measurement. Because RTK ensures centimeter-level accuracy (half-inch accuracy), anyone can easily record precise positions that were difficult with traditional manual methods. If needed, multiple measurements can be averaged to improve accuracy to the millimeter level. Measurement data automatically record the date/time and positioning status (number of satellites, status of correction information), and notes can be attached if required.

• Data recording and cloud storage: After measurement, save the data in the app. The LRTK system automatically converts the acquired coordinates to the familiar coordinate systems used on site—such as the Geospatial Information Authority of Japan’s plane rectangular coordinate system—or to world geodetic coordinates, and file and point names are auto-numbered. Data stored on the device can be uploaded to the cloud with a single tap. Even at sites outside communication coverage, data are saved locally and synchronized later when back in range. Uploaded location data are instantly plotted on web-based maps, so managers and colleagues in the office can view the points. Clicking each point shows the name, time, and notes, making later follow-up easy.

With this workflow, collecting field data based on kilometerage is dramatically streamlined. Tasks that previously required assembling a survey team or recording on paper in the field and re-entering data later can now be completed by one person on site with LRTK.

Effects of positional recording and AR display during obstruction removal and abnormality inspections

A key feature of LRTK is that it can support fieldwork not only by recording numerical data but also by integrating with AR (augmented reality) technology. Combining high-precision positional data with AR during obstruction removal and abnormality inspections produces the following effects.

• Immediate and accurate position sharing: When debris or equipment abnormalities are found on the track, measuring the coordinates with LRTK and sharing them via the cloud lets remote managers grasp the situation immediately. On site, the smartphone camera can display AR markers (virtual pins) to attach virtual “marks” to real space. For example, a crack inside a tunnel or a damage spot that is hard to see at night can appear as a red pin through the smartphone, intuitively indicating the location.

• Efficient work instructions and situation awareness: With AR displays, field workers can see at a glance which part needs repair without mentally cross-referencing maps or drawings. It is possible for supervisors to upload 3D repair points or caution notes to the cloud in advance and project them onto the field smartphones. This reduces time spent searching on site and ensures crews arrive at the correct problem locations within limited work time. Also, if you re-measure the spot after debris removal and save the data, post-work reporting and history management become accurate. Less-experienced staff can visually understand instructions via AR, reducing mistakes.

Previously, outdoor AR suffered from alignment errors, but fusion with RTK positioning has resolved that, bringing AR to a practical level for field support. By combining LRTK’s high-precision positioning data with AR, on-site visualization and information sharing are greatly improved, enhancing response capability to abnormalities and increasing recovery work efficiency.

Use as maintenance data (cloud integration, history tracking, future re-surveys)

Kilometerage data obtained with LRTK can be accumulated and used as valuable maintenance information. This section explains cloud integration, the use of historical data, and applications for future re-surveys.

• Centralized data management in the cloud: As mentioned earlier, data uploaded from the LRTK app are centrally managed on a cloud platform. Authorized railway personnel can access the field database via a web browser and see on a map when, who, and where measurements were taken. This eliminates the need for paper forms or serial email reports and dramatically speeds information sharing. Photos and inspection records taken on site can be saved linked to kilometerage and coordinates, reducing later organization work.

• History tracking and trend analysis: Data accumulated in the cloud are managed in time series, so you can track when the same location was measured in the past and how the position or condition has changed. For example, continuously measuring bridge settlement during regular inspections allows plotting long-term change graphs for early detection of abnormal trends. When analyzing commonalities of repeat-failure locations, historical position data provide valuable clues for predictive maintenance. Accumulated data could be trained in AI to predict future deterioration or propose optimal repair plans.

• Reflection in future re-surveys and design: Once high-precision position data are obtained, they are useful for future projects. During track relocations or equipment updates, referring to past survey data allows precise identification of discrepancies between the current state and design drawings. If necessary, the same coordinates can be re-measured for an on-site re-survey to update to the latest information. This accumulates assets within the company that can be used immediately for preliminary surveys for new construction or for disaster recovery baseline data.

Thus, data collected via LRTK are not limited to single inspection records but contribute to long-term asset management and strategic maintenance planning. The accumulation of digitized high-precision data also promotes DX (digital transformation) across railway infrastructure management.

How kilometerage measurement and field recording workflows change with LRTK

Finally, let’s summarize how field workflows change with LRTK implementation.

Traditionally, kilometerage measurement and recording of equipment positions relied heavily on specialized survey departments and veteran experience. It was not uncommon for field staff to conduct measurements in limited nighttime work windows with printed drawings and distance meters in hand. Completing all measurements within a short night shift was difficult, and updates were sometimes postponed. Data were often handwritten in notebooks and re-entered into office PCs, introducing risks of human error and omission.

With LRTK, this workflow changes significantly. Track maintenance and equipment technicians can take measurements during daytime patrols with a smartphone in hand and immediately record required points digitally. Data sent in real time to the cloud can be reflected directly in reports and subsequent work plans, eliminating information gaps between field and office. Because the system is intuitive and usable even by non-experts, each staff member effectively becomes a “surveyor.” This raises baseline field capabilities and reduces dependence on individuals, allowing tacit know-how to be accumulated as numerical data in the organization. Measuring during the day also reduces some nighttime work, easing worker burden and reducing human error. Tasks that once required waiting for measurements can be done on the spot, enabling a fast PDCA cycle for maintenance improvements. The organization as a whole can achieve efficient and robust infrastructure maintenance.

By combining this long-standing kilometerage method with modern technology, DX in railway field operations is steadily progressing. High-precision positioning with LRTK brings substantial benefits in both safety and work efficiency and will likely see wider adoption. For those working in railways, actively embracing this new tool may be a good way to ride the wave of change from "intuition, experience, and analog" to "data and technology."