Accelerating On-site DX for Civil Engineering Construction Managers! How LRTK Opens a New Era of *i-Construction*

The wave of digital transformation (DX) is steadily sweeping into construction sites. Especially driven by the Ministry of Land, Infrastructure, Transport and Tourism’s *i-Construction*, the work of civil engineering construction managers is beginning to change dramatically. Faced with a decline in experienced technicians and the need for work-style reforms, leveraging digital technologies is key to improving on-site productivity while ensuring quality. In this article on on-site DX, we explain how the latest technologies are transforming the tasks of civil engineering construction managers. We also explore how the new solution LRTK, which individual technicians can easily adopt, is poised to pioneer a new era of *i-Construction*.

How is *i-Construction* being used on sites?

*i-Construction* is an initiative proposed around 2016 as a national policy to boost productivity on construction sites. Specifically, it promotes the use of ICT (information and communication technology) in each phase of survey, design, construction, and management. Examples of practices include:

• Use of 3D data: Create 3D models using CIM (Construction Information Modeling) from the design stage and use them for construction planning and as-built verification. Being able to visualize the finished form in three dimensions makes it easier to share design intent on site.

• Introduction of ICT-equipped construction machines: Equip heavy machinery such as bulldozers and backhoes with GNSS (satellite positioning) and machine control technologies to perform grading and excavation automatically or semi-automatically. Operators need only move the machine according to the design data, enabling near-specification construction. This allows high-precision work without relying on highly skilled machine operators.

• 3D surveying and as-built management: Acquire pre- and post-construction terrain and structure data as 3D datasets using drone photogrammetry or terrestrial laser scanners. Large areas can be surveyed in a short time, making it far more efficient and comprehensive than manual point surveying.

These initiatives are gradually taking hold, particularly in large-scale projects commissioned by national and local governments. In direct-managed projects, the application rate of ICT construction (earthworks) is increasing, and it is now common to see technicians on site with 3D drawings and tablet devices. For example, in road construction, the workflow can include 3D surveys by drone before construction, precise cut-and-fill by GNSS-equipped bulldozers during construction, and post-construction verification of as-built conditions using drone or laser scanner point cloud data.

On the other hand, whether the benefits of *i-Construction* are realized depends on site scale and organization. Large construction companies can promote DX on large projects by deploying specialist staff and expensive ICT equipment, but on small- to medium-sized sites or projects with limited personnel, investments can become underutilized. Even so, it is indisputable that making digital technology practical for everyday site work will become increasingly important. In the next section, we consider the gap between the ideals and realities of ICT construction and how to bridge it.

The reality of ICT earthworks: bridging the gap between ideals and reality

Some may imagine that full use of the latest ICT will make construction entirely automated: drones automatically surveying and calculating earth volumes, excavators digging automatically, bulldozers grading automatically, and drones performing as-built inspections on their own. But real civil engineering sites are not that simple, and ICT earthworks face various constraints and challenges.

First, the application of ICT technologies is subject to environmental constraints. GNSS-equipped machines and surveying instruments cannot be used where satellite signals do not reach, such as inside tunnels or in mountainous areas. Positioning accuracy can degrade near high-voltage lines, and at certain times satellite geometry can increase errors. Drone photogrammetry is affected by weather conditions—it cannot fly in strong winds or rain, and on bright sunny days surface glare can reduce accuracy. Moreover, processing aerial photos into point cloud data can take hours to days on a high-performance PC, leaving issues in terms of immediacy. As a result, many technicians feel the dilemma that total-station manual surveying is the reliable way to achieve stable accuracy regardless of weather.

Next, cost and skill barriers cannot be ignored. 3D laser scanners and ICT-equipped machines are very expensive and cannot be kept on every site. Operation and data processing require specialized knowledge, and companies lacking veteran surveyors or CIM engineers may find that purchased equipment goes unused. Particularly on small projects, deploying high-cost equipment may not be economically justified, forcing reliance on traditional manual methods.

To bridge the gap between the ideal and reality of ICT construction, it is important to identify which tasks should adopt ICT and to introduce easy-to-use tools suited to site scale. Rather than replacing everything with the latest technology, prioritize digitizing time-consuming or dangerous tasks and complement the rest with traditional methods. Also, if there are simple digital devices that site technicians themselves can operate, they can proceed with DX at their own pace without relying on specialists. One recently noted solution is a simple high-precision surveying tool that combines a smartphone with a compact GNSS device. In the next chapter, focusing on as-built management, we look at the benefits this new approach brings to sites.

As-built management: from an era of "recording" to "visualization and immediate inspection"

Among construction management tasks, as-built management is particularly important. As-built management verifies that completed structures and construction elements meet the design specifications and is central to quality assurance, acceptance by the client, and handover conditions. Traditionally, as-built verification has relied mainly on manual measurement and recording. For road works, for example, workers would measure subgrade or pavement thickness, width, and elevation at several representative points after completion using tape measures, staff rods, and levels, checking each against design values. Results would be compiled into as-built management tables with photos for submission.

However, this conventional method has long had issues recognized by many site technicians. First, it is labor- and time-intensive. Surveying usually requires two or more people, and measuring many points across a wide site is a heavy burden. Choosing measurement points and recording results is a skill-based task, making it difficult to cope under staff shortages. Second, there is a lack of coverage due to sampling. The number of points measurable manually is limited, so inspections tend to be spot checks. Measuring only a few dozen points cannot capture the entire as-built condition, and defects in unmeasured areas can be missed. Third, there is the potential for human error—forgetting to take photos or recording incorrect measurements can occur in busy sites. If photos are missing for buried structures, the worst-case scenario could require rework or lead to disputes. In short, the old approach of measuring only discrete points and relying on people has reached its limits in efficiency and risk management.

In recent years, there has been a move to incorporate 3D measurement technologies into as-built management. Point cloud data, obtained from laser scanners or drone photogrammetry, digitally records the site’s shape as a collection of innumerable measurement points. A single survey can densely scan a wide area, allowing as-built conditions to be treated as surfaces rather than points. For slope works, for example, visualizing the entire slope’s gradient and irregularities as a point cloud makes it easy to spot subtle unevenness or shaping errors that would previously be overlooked. As-built management is shifting from “recording” to “visualization and immediate inspection.”

The Ministry of Land, Infrastructure, Transport and Tourism has responded by drafting a “Guideline for As-built Management Using 3D Measurement Technology (draft)” to promote site adoption. The draft guideline specifies required accuracy and density standards for point cloud-based as-built measurement; meeting these allows the results to be recognized as official as-built deliverables. Where traditional practice placed reference points with tapes and levels to control elevation, it is now possible to verify as-built conditions with equal or greater reliability using point clouds plus high-precision GNSS. Technically, it is becoming feasible to check on-site in real time whether construction matches the design and to correct it on the spot.

To put these changes into practice on site, tools that make point cloud measurement and high-precision positioning easy to use are required. One newly emerged concept is high-precision positioning × point cloud × smartphone. In the next chapter, we examine how this solution is evolving site surveying.

Site surveying evolving with high-precision positioning × point cloud × smartphone

3D scanners and drones are convenient but, as mentioned, expensive and difficult to operate. A recently gaining approach is to combine a smartphone with an RTK-GNSS receiver for site surveying. Smartphones now have high-performance cameras and, on some models, LiDAR sensors, and their processing power as compact computers keeps improving. By combining a smartphone with an RTK (Real Time Kinematic) GNSS receiver—the pinnacle of satellite positioning—you can realize a pocket-sized “all-purpose surveying device.”

LRTK, developed by Refixia, a venture from Tokyo Institute of Technology, embodies this “smartphone × RTK” concept. It is a compact device weighing several hundred grams that attaches to a smartphone or tablet and receives RTK correction information from satellites, providing centimeter-level positioning accuracy (half-inch accuracy) to the smartphone. Paired with the dedicated mobile app “LRTK,” it integrates everything from acquiring positioning data to point cloud scanning and AR-based as-built visualization—handling the necessary tasks all in one.

For example, by walking around with an LRTK-attached smartphone and pointing it at the site, the LiDAR sensor or camera captures surrounding shapes and continuously acquires them as point cloud data. Typical standalone smartphone positioning errors of about 5-10 m (16.4-32.8 ft) are drastically reduced by RTK corrections to extremely high accuracy—about horizontal 1-2 cm (0.4-0.8 in) and vertical within 3 cm (1.2 in). Because the acquired point clouds are tagged with accurate global coordinates (latitude, longitude, elevation), you can overlay the 3D point cloud with design data on the spot to check as-built conditions or preserve data for later drawing creation, making the data widely usable.

Since only a smartphone and a small GNSS receiver are required, surveying that previously needed a total station plus prism staff and two people can now be completed by one person. The device is pocket-sized with a built-in battery and does not get in the way when walking around a site. There are no complicated settings or operations: with an intuitive interface you can press a button on the smartphone screen to acquire point coordinates, start and stop point cloud scans, and record photos. In other words, LRTK can be seen as an innovative tool that strongly supports on-site DX as a “precision surveying instrument anyone can use.”

Another notable point is that because it operates with just a smartphone and satellites, it has few connectivity constraints. LRTK supports Japan’s Quasi-Zenith Satellite System (QZSS) high-precision positioning service (CLAS), enabling centimeter-level positioning even in mountain areas without cellular signal or at disaster sites where the internet is down. Surveying deep in the mountains traditionally posed challenges in establishing reference points, but with LRTK you can obtain accurate positions offline as well, allowing digital surveying benefits to be enjoyed across a wider range of sites.

How is it used on actual sites? LRTK use cases and changes

How do such smartphone RTK solutions perform on real civil engineering sites? Here are some concrete LRTK use cases.

• Road construction: Using LRTK to verify subgrade and pavement thickness and elevation has shortened as-built measurement tasks that used to take several people half a day. Record measurement points with a smartphone at designated locations and complete in-site sharing via the cloud the same day. Using LRTK’s AR function, tasks like setting batter boards or laying out reference points—which previously required two people—can be accurately performed by one person. On long roadworks, you can walk while measuring many points and instantly check results, reducing oversights and easing inspection preparation.

• Bridge construction: LRTK is effective on bridge sites with many as-built items—positions and elevations of abutments and piers, thickness checks of girders and deck slabs, etc. Quick and precise surveying is possible even at heights or during night work, providing safety management benefits. For example, measuring the top elevation of a bridge pier immediately after concrete placement allows instant verification against design and prevents later rework. You can also AR-display a bridge model on your smartphone during construction to check whether anchor bolt holes or bearing installation locations are correct. Rapid and reliable as-built management reduces worker burden and lowers the risk of construction delays.

• Slopes and reclaimed land: For steep slope works, verifying finished gradients is important, but climbing slopes to measure is dangerous and limited. With LRTK, workers can remain in safe areas below the slope and perform point cloud scans of the entire slope with a smartphone. In just a few minutes you can acquire extensive 3D terrain data, detail gradient and surface irregularities, and immediately identify areas needing repair. Because measurement is non-contact and remote, there are no missed spots, and safety improves dramatically by avoiding entry into hazardous zones.

• Disaster sites: LRTK is useful for surveying disaster-damaged areas like slope failures or sediment runoff from earthquakes or heavy rain. In large-scale disasters, rapid on-site surveying capability without waiting for heavy machinery or large survey teams is crucial. With LRTK, you can quickly measure collapsed slopes or deposited sediments as point clouds, calculate volumes on-site to estimate earthworks, and share results via the cloud so headquarters and the client receive real-time updates. Since CLAS enables continued positioning even outside cellular coverage, you can achieve rapid and safe situation assessment even when communications are down. LRTK was used in the investigation of the Noto Peninsula earthquake, where a single small device provided high-precision damage records and immediate sharing.

These examples demonstrate concrete DX effects from LRTK adoption. Beyond measurement efficiency, there are multifaceted benefits such as improved safety, quality assurance, and smoother communication via cloud sharing.

Why one-person surveying and one-person as-built management is possible

A major change brought by LRTK is the realization of “one-person surveying and one-person as-built management.” Traditionally, surveying and as-built management were carried out by multiple people. Why can one person now complete these tasks? The answer lies in technological advances and operational innovations.

The first point is miniaturization and integration of positioning and measurement equipment. A surveying device integrated with a smartphone, like LRTK, eliminates the need to carry separate devices for positioning, measurement, and recording. The app on the smartphone automates tasks from positioning to point cloud generation, photo capture, and note-taking, linking and saving all data. This enables a single person to continuously perform tasks that used to be divided among several roles, such as “measuring” and “recording.”

The second point is automation and simplification of operations. Previously, obtaining survey results required setting up instruments at each station, reading angles and distances, and converting to coordinates via manual calculations or software—specialized procedures. Now, the LRTK app displays coordinate values on the spot with a button press, and point cloud scanning is started and stopped like recording a video. Real-time computation and improved UI make it intuitive for non-experts to operate. New or young technicians can use it without hesitation, enabling tasks that once required veteran surveyors to be handled in-house.

The third point is streamlined data sharing and utilization. If data collected by one person is immediately synced to the cloud, office colleagues and technical managers can check back in real time. On-site staff can receive instructions like “measure this point a bit more” or “scan this area too” and respond accordingly. Conversely, the on-site operator can instantly generate color-coded heat maps from the collected point cloud to confirm excesses and shortages in as-built conditions—accelerating feedback processes. In short, digital systems act as “an extra assistant,” allowing one person to perform work that would have required multiple people.

Because of these factors, some sites report that “a single site supervisor can handle surveying without assembling a survey team” after adopting LRTK. One-person surveying increases flexibility in personnel allocation and helps address labor shortages. Flexible responses such as having a small crew verify areas at night that couldn’t be measured during the day also become easier.

Paperwork and inspections change too: cloud integration and PDF workflows

The effects of on-site DX extend beyond measuring and verification to subsequent document creation and inspection responses. Systems like LRTK dramatically simplify documentation for as-built management.

First, positioning and point cloud data acquired with the LRTK app are automatically converted to official geodetic coordinate values (for example, the JGD2011 plane rectangular coordinate system), and elevations are corrected to geoid height. This means you get deliverables aligned with official reference systems from the start without complex on-site coordinate calculations—saving considerable effort in downstream document preparation.

Because acquired data can be organized and managed in the cloud, drawing creation and report generation based on measurement results are smoother. For example, you can cut required sections from point clouds on a cloud platform to create as-built management tables or 3D models, and easily populate prescribed formats with photos and measured values. Compared to the old practice of comparing field books and photo ledgers to compile reports by hand, centralizing digital data greatly reduces work time. Site-collected information can be used directly for electronic deliverables, reducing duplicate entry and transcription errors and improving the accuracy of as-built documentation.

Cloud integration is also changing inspection and stakeholder sharing styles. Traditionally, inspectors were presented with printed charts and large photo albums for on-site inspections. With DX, you can, for example, share a link to point cloud as-built data in the cloud with the client for prior review. The client can view the 3D data in a browser and point out concerns, and the contractor can perform corrections or supplementary surveys and update the data—enabling a form of remote inspection collaboration. At minimum, the need to copy data to USB drives or print dozens of A3 drawings will be eliminated.

LRTK’s cloud includes data-sharing functions that let you issue a viewing URL to stakeholders with a single button. With password protection and expiration settings, security is maintained, and anyone can view and download measurement results from a browser without specialized software. This shift from paper to PDF/Web is changing as-built management output formats and accelerating digital-based inspection and consensus-building internally and externally.

By digitalizing the entire workflow from site measurement to document creation and inspection responses, the workload of civil engineering construction managers is reduced, allowing them to devote more time to safety management and schedule coordination.

Site-led DX: start with LRTK

As discussed above, site DX offers not only efficiency gains but also significant value in quality improvement and safety assurance. Following the Ministry’s *i-Construction* and BIM/CIM trends, construction management based on 3D data will become increasingly standard. Digitalizing as-built management enables objective quality assurance that does not rely solely on the intuition and experience of seasoned workers, and it is key to maintaining high productivity with limited personnel.

To adapt to these changes, it is wise to begin with small, site-led DX measures that can be implemented directly. Large-scale investments or highly specialized DX initiatives pose high barriers, but a simple surveying solution that works with just a smartphone can be tried as soon as tomorrow. LRTK is precisely such a trump card for on-site DX. Even without special skills, LRTK lets you easily adopt centimeter-level accuracy (half-inch accuracy) surveying and 3D as-built management. Why not start digitalizing familiar tasks and experience the benefits firsthand?

LRTK can become a reliable ally on your sites. By adding the latest technology to traditional methods, you can experience a new form of construction management. For advancing construction management DX, simple surveying with LRTK is ideal. Now is the time to take site-driven steps into DX and evolve your site to the next stage.