Digitizing Kiloposts with Simple Surveying: Promoting Infrastructure DX with High-Precision Positioning Data

In the field of infrastructure management, maintaining aging equipment and facilities is a major challenge. Among these, kiloposts (distance markers) installed along expressways and railway lines are indispensable for daily management and locating positions during emergencies. However, traditionally the location information and condition of kiloposts have relied on paper ledgers and institutional knowledge, making accurate management difficult in some respects. This article reviews what kiloposts are and identifies management challenges, then introduces the benefits of digitizing ledgers through simple surveying using a smartphone and high-precision positioning technology (RTK). As an example of infrastructure DX (digital transformation) using point cloud data and cloud integration, we will look concretely at how this can improve on-site efficiency and disaster response capabilities.

What is a kilopost? Definition and role on railways and roads

A kilopost is a sign that indicates the distance from a point designated as the “origin” on a railway or road. In Japan, most are displayed in kilometers, so they are commonly called “kiloposts” (formally referred to as “distance markers” on railways and “distance signs” on roads). For example, on railways there are markers installed beside the track every 1 km (1 km (3,280.8 ft)). A special “0 kilopost” is placed at the origin, and thereafter the numbers increase to 1 km (3,280.8 ft), 2 km (6,561.7 ft)… On roads, small signs indicating distance from the road’s origin are similarly installed at regular intervals on shoulders and median strips of expressways and national highways. On expressways there are typically green kiloposts every 1 km (1 km (3,280.8 ft)) (e.g., “12”) and finer displays every 100 m (100 m (328.1 ft)) (e.g., white auxiliary signs showing “12.6”), which help indicate travel distance and pinpoint accident locations.

The main roles of kiloposts are as follows:

• Reference for location: They function as reference points that express locations along a route or road. During maintenance or inspection, locations can be accurately communicated as “the point X km from the origin.” For example, saying “the 12.6 km (41,338.6 ft) point on line XX” lets personnel immediately identify the location.

• Distance measurement: They serve as markers to measure distances in operation management and road management. Kilopost values are used when calculating train travel distances or section distances on roads.

• Location identification in emergencies: In accidents or disasters, kilopost markings are used to report locations for rescue and recovery activities. As with accident reports on expressways that say “near kilopost 15 on XX road,” they contribute to accurate on-site location sharing.

Thus, kiloposts are unobtrusive but provide essential basic information for infrastructure operation. However, their management comes with several challenges.

Field challenges in kilopost management: deterioration, positional errors, and ledger updates

When managing kiloposts in the field, the following issues have been pointed out:

• Sign deterioration and damage: Kiloposts are exposed to wind, rain, and sunlight for many years, causing paint to peel or numbers to become hard to read. Posts can also be broken or lost due to snow removal work or vehicle run-off accidents. Deteriorated signs reduce on-site visibility and render the distance markings ineffective.

• Position displacement: Kiloposts should ideally be installed at precise distance positions, but in practice they can be placed slightly off due to terrain or construction constraints. When routes are changed by road improvement works, the positions of old kiloposts can become inconsistent with the new actual distances. In such cases, discrepancies arise between the markings and actual positions, and paper drawings or records alone may make it difficult to reconcile them with the field.

• Ledger management and update burden: Traditionally, information related to kiloposts (installation location, displayed distance, installation date, etc.) has been managed in paper ledgers or spreadsheet files. Each time there is a field change the ledger must be updated, but this is a tedious manual task. When multiple personnel manage the data, omissions and entry errors are likely, resulting in ledgers not being kept up to date. If the current state is not known, confusion can occur when verifying on site, such as “the sign that should be there according to the ledger is not found” or “the displayed number does not match the ledger.”

Because of these issues, new approaches are required to manage kiloposts accurately and efficiently. One promising approach is digitizing ledgers by combining high-precision positioning RTK with simple surveying using smartphones.

Advantages of high-precision positioning (RTK) and simple smartphone surveying

Advances in technology have dramatically changed the positioning field in recent years. In particular, the satellite positioning technique called RTK (Real Time Kinematic) is known as an advanced method capable of specifying positions with centimeter-level precision. RTK achieves high accuracy by having a base station and a rover (the surveyor’s GNSS receiver) communicate to correct satellite positioning errors in real time. Whereas expensive GNSS surveying equipment used to be required, RTK functionality can now be conveniently utilized on smartphones.

Simple surveying using smartphones offers the following advantages:

• Centimeter-level high accuracy (half-inch accuracy): Typical smartphone GPS has errors of about 5–10 m, but by using RTK-capable receivers and networks, positioning with errors of a few cm (a few in) is possible. When recording the positions of infrastructure like kiloposts, centimeter-level accuracy provides far more reliable data than traditional visual estimation or general GPS.

• Mobility and ease: The smartphone combined with a compact GNSS receiver is lightweight and easy to carry. Workers can patrol a site with a smartphone in their pocket without lugging heavy survey equipment or tripods, and perform surveys immediately when needed. One person can measure multiple points quickly, enabling efficient data collection with a small team.

• Real-time data recording: Smartphone surveying automatically records information like date/time and point names along with positioning. There is no need to write notes on paper; a press of the measurement button instantly saves point data including latitude, longitude, and elevation digitally. This reduces input errors and allows field-acquired data to be used directly in subsequent processes.

• Low cost: Compared to dedicated surveying instruments, a smartphone plus a small RTK receiver greatly reduces initial investment. Since existing smartphones can be used, deploying one device per person is realistic. Lower cost barriers make it easy to introduce precise positioning into tasks that previously did not use it.

• Multifunctional extensibility: Smartphones have cameras and communication functions, and recent models even include LiDAR sensors. Therefore, during a single site visit you can simultaneously capture visual records through photos and perform 3D scans (point cloud measurements) with LiDAR. Collected data can be saved in the app with coordinates and annotated with notes or voice recordings as needed. Beyond mere positioning, smartphone surveying enables comprehensive digital recording of site conditions.

These advantages dramatically streamline kilopost position checks and condition assessments. Next, we will look at how high-precision coordinate data and point cloud data collected by smartphones can be centrally managed in the cloud to create digital ledgers.

Point cloud acquisition + cloud integration of high-precision coordinates for digitizing ledgers

With smartphone RTK surveying, it is possible not only to obtain coordinate numbers but also to use 3D scanning functions to acquire point cloud data. A point cloud is a dataset that represents an object’s shape as a collection of countless coordinate points, and using LiDAR sensors and the like you can digitize the three-dimensional form of a site. For example, at a highway kilopost, scanning the signpost and surrounding road shape with a smartphone can record a point cloud model with cm-level accuracy (half-inch accuracy) and attached position information.

The obtained coordinate data and point cloud data can be uploaded directly from the smartphone app to a cloud database. By integrating with the cloud, information measured in the field is immediately reflected in the digital ledger and can be shared in real time with managers in the office and other team members. The need to take paper ledgers back to the office for transcription is eliminated, and ledger updates can be completed on the spot.

A cloud-based digital ledger can link and store all kinds of information for each kilopost. Specifically, the following data can be managed together for each kilopost:

• Unique ID and name (e.g., “Tohoku_Expressway_12.0 km marker”)

• High-precision position coordinates expressed as latitude/longitude/elevation or in a plane rectangular coordinate system

• Installation date, type (expressway, railway, etc.), and displayed distance value

• Photos taken on site and point cloud models acquired via LiDAR

• Inspection dates and comments at those times, and records of any damage

By centralizing textual, spatial, and visual information, you can understand at a desk “what sign is at that location, where exactly it is, and what its condition is.” Each dataset plotted on a map can be viewed intuitively, and searching and filtering are easily performed as needed. This builds what could be called a digital twin of the kiloposts.

Benefits of unified management of installation, updates, and inspection history using high-precision data

By digitizing ledgers, you can track the history from kilopost installation through updates (replacement/reinstallation) and regular inspections in a time series. The main benefits of this unified management are as follows:

• Centralization and sharing of information: Sharing a single database within the organization eliminates the inefficiency of different staff using different ledgers. Field personnel, managers, and decision-makers can all access the same up-to-date data and eliminate discrepancies in understanding. Because it is shared on the cloud, status can be checked via a browser even from remote locations.

• History management and traceability: Records accumulate of when, who, and what was performed on each kilopost (installation, repair, removal, inspection, etc.). For example, it becomes easy to see “this marker at XX km was updated X years ago” or “previous inspection pointed out deterioration,” helping prevent oversight and assisting future planning. When problems arise, past data facilitates cause analysis and countermeasure planning.

• Improved data accuracy and reliability: Using RTK positioning data dramatically improves the positional accuracy of ledger information. Instances of “the record says it should be there but it can’t be found” are reduced, minimizing discrepancies between the field and the ledger. Reliable data-based management also reduces unnecessary site verification work.

• Streamlined maintenance planning: Analyzing ledger data helps identify which sections of kiloposts are aging and when replacements are likely needed. For example, if inspection histories show faster deterioration in certain areas (heavy snowfall zones or seaside areas exposed to salt spray), targeted preventive maintenance can be prioritized. Maintenance plans backed by high-precision data are more rational and defensible than those based on intuition or experience alone.

• Strengthened coordination between field and administrative work: Because data collected in the field is instantly reflected in the cloud ledger, much of the post-field input work and report preparation is reduced. With real-time sharing between the field and office, time-consuming tasks like “calling in field measurements by phone” or “emailing reports” are eliminated, saving time and reducing errors for both sides.

Thus, unified management via digital ledgers not only consolidates data but also enhances and streamlines entire operational processes. What future developments can be expected by leveraging the accumulated data?

Expanded maintenance and disaster response through past-data comparison and map integration

A digitized kilopost ledger is useful not only for current information management but also offers great potential in future maintenance and disaster response through comparative analysis with past data and integration with other geographic information.

In terms of maintenance, comparing time-series data enables early detection of anomalies. For example, if you measure and store the coordinates of the same kilopost annually with RTK, you may detect minor ground subsidence or displacement at that point. Although it is rare for the sign itself to move, if it did shift due to a landslide, you could immediately identify it by comparing with past data in the digital ledger. Using point cloud data, you can also quantitatively evaluate sign tilt and surrounding environmental changes (e.g., obstructed sightlines due to tree growth). Monitoring based on such data supports considerations for repairs and reinforcements and promotes planned maintenance (preventive upkeep).

In terms of disaster response, digital ledgers act as powerful crisis management tools. In large earthquakes or heavy rains causing landslides or road collapses, kilopost data helps identify affected locations and the extent of damage. For example, you can quickly extract and visualize on a map the information “collapse occurred between 12.0 km (39,370.1 ft) and 14.0 km (45,931.8 ft) on XX road.” Rescue and recovery teams can rush to the site based on that information, and pre-overlapping surrounding infrastructure data (tunnels, bridges, evacuation routes, etc.) enables rapid secondary risk assessment and detour planning. Furthermore, comparing kilopost position data before and after a disaster contributes to quantitative assessment of terrain changes. With cloud-based ledgers, multiple relevant agencies can access and share information simultaneously, contributing to the centralization of command-and-control information in disaster response.

In this way, high-precision data digitized in ledgers can be applied widely from routine maintenance to emergency response, contributing to increased infrastructure resilience.

Case examples of digitizing ledgers using smartphone RTK

In practice, initiatives using smartphone RTK and cloud integration are gradually being introduced in the field. For example, one municipality introduced a smartphone-mounted RTK positioning system for road facility inspections, enabling a single staff member to quickly measure and record the positions and conditions of road signs and kiloposts. By simply attaching a dedicated compact GNSS receiver to a commercial smartphone, tasks that previously required specialist survey teams can now be performed by anyone, realizing a “one device per person” mobility. Collected data is uploaded on the spot to the cloud management system and shared in real time with relevant departments within the office. This allows detailed position data, photos, and point clouds gathered in the field to be immediately reflected in the digital ledger, enabling office staff to understand field conditions without going to the site.

The actual effects of implementation are beginning to appear. Where staff used to search the field relying on paper drawings and past records, they can now navigate directly to the accurate kilopost positions displayed on a GPS map. One manager reported, “Trips back and forth to reconcile the ledger with the field have decreased, allowing us to spend our limited time on more important inspections.” Also, one smartphone RTK solution (LRTK) uses a compact receiver weighing about 125 g (about 125 g) attached to the smartphone to provide cm-level positioning, point cloud scanning, and AR-based location guidance, changing the style of on-site work. For example, a highway company trialed using a smartphone and LRTK to inspect roadside facilities and share data with the management office the same day. Throughout the process, data acquisition to ledger updating became seamless, speeding decision-making and reducing errors.

These examples show that on-site implementation of digital technologies is producing tangible benefits. The important factor is not the technology itself but its operational integration to solve field problems. Smartphone RTK and cloud usage are versatile solutions applicable not only to kilopost management but to the management of various infrastructure assets. Starting with small sections or pilot implementations and rolling out in a form that field staff can master will expand the scope of infrastructure DX.

Conclusion

Digitizing kilopost ledgers may seem modest, but its effects are genuinely improving the quality of infrastructure management and transforming field operations. By combining high-precision positioning data and cloud technology, it is now possible to accurately capture the “current state of the field” and share it among all stakeholders. This is precisely the aim of infrastructure DX, and the accumulated data will form the foundation for smarter infrastructure operation and maintenance in the future.

Making the distance markers that are kiloposts visible and centrally managed in digital form is a model case applicable to the overall maintenance of social infrastructure such as roads and railways. To improve the capacity to respond to aging and disaster risks, the starting point is to accurately understand the information at hand. Why not open the path to infrastructure DX by taking the accessible first step of simple smartphone and RTK surveying?