Construction and Surveying Productivity Improvement Expo — The Front Line of On-Site DX: Smartphone Surveying Device LRTK Sparks a Productivity Revolution

Against the backdrop of efforts to improve construction site productivity and the trend toward DX (digital transformation), the annual "Construction and Surveying Productivity Improvement Expo" (commonly: CSPI-EXPO) brings together the industry's most advanced technologies. This article focuses on the smartphone surveying device "LRTK," which is at the forefront of on-site DX, and introduces how it can transform construction, inspection, and surveying sites.

The Construction and Surveying Productivity Improvement Expo and the Background of Industry DX

The Construction and Surveying Productivity Improvement Expo is a trade show where construction industry stakeholders (site managers, ICT promotion staff, surveying companies, municipal officials, etc.) gather to experience new technologies and services that lead to productivity improvements. Recently, the construction industry has been accelerating "construction DX" (digital transformation) through active use of ICT technologies, driven by severe labor shortages, stagnation in skill transfer, and the need for thorough safety management. Policies such as the Ministry of Land, Infrastructure, Transport and Tourism's *i-Construction* have strongly supported the digitalization and labor reduction of field operations from surveying to construction, inspection, and maintenance. Declining working populations and aging workers have also made labor shortages more serious, and DX is expected to be a key solution to these challenges. It is truly a key to the on-site productivity revolution.

In response to these trends, the CSPI-EXPO features many cutting-edge technologies that support the future site, such as drone surveying, automated transport robots for construction machinery, AI image analysis, and AR/VR simulation. For example, at the 6th Construction and Surveying Productivity Improvement Expo held at Makuhari Messe in May 2024, themed "The Future of Construction," a wide range of solutions addressing industry issues such as decarbonization and energy saving (green initiatives), labor reduction and digital construction, and quality control were introduced. Attendance at the expo has increased year by year, and the 7th event in 2025 (held internationally) attracted about 57,000 visitors. Among the exhibits this year, a particularly attention-grabbing topic was an easy, high-precision positioning solution using smartphones. The idea that surveying can be completed with a smartphone created a strong impact, and many visitors stopped at the booth for a smartphone surveying device called LRTK.

Emergence of Smartphone RTK Surveying Technology and How It Differs from Traditional Methods

Traditional surveying typically used specialized equipment such as total stations and GPS receivers and was usually carried out by multiple people over extended time. For example, with a total station, one person must set up the instrument while another holds the prism at the target point, and measuring many points can take an entire day. Additionally, comparing survey results with drawings required bringing data back to the office, leading to inefficient back-and-forth between site and office.

However, in recent years, miniaturization of high-precision GNSS positioning technology and the development of communication infrastructure have ushered in an era in which centimeter-level positioning with a smartphone is possible. GNSS surveying using the RTK (Real Time Kinematic) method achieves high precision of about 2–3 cm (0.8–1.2 in) horizontally by applying real-time corrections of satellite positioning error information between a base station (known point) and a rover. By attaching an RTK receiver to a smartphone, the smartphone’s GPS error that used to be several meters (several ft) can be reduced to several centimeters (a few in), giving palm-sized devices positioning accuracy comparable to traditional stationary instruments. Furthermore, by combining this precise position information with AR (augmented reality) technology, a revolutionary method is born that allows even one person to intuitively perform surveying and stakeout tasks.

The main differences from traditional methods are as follows:

• Dramatic reduction in required manpower and time: Total station surveys typically required at least two people, but with a smartphone plus an RTK receiver, one operator can complete on-site surveying. Even in places with poor visibility, GNSS can measure directly, and multiple point measurements can be completed in a short time. As a result, the days spent on surveying and as-built control can be drastically reduced.

• Reduced dependence on skilled expertise: Traditionally, veteran technicians handled instrument operation, reading, and recording, and experience was essential for accurate measurements. Smartphone surveying uses dedicated apps that guide measurement procedures and automate data recording, so anyone can operate it intuitively. There is no need to follow paper drawings while taking dimensions; simply follow the smartphone screen prompts and press a button at the point you want to measure to capture coordinates. Human reading errors and recording mistakes are also reduced, easing the burden on veterans, aiding skill transfer to younger workers, and helping address labor shortages.

• Real-time on-site verification and sharing: Acquired survey data can be displayed on the smartphone screen as AR and overlaid with design drawings or past data for immediate verification. You can immediately check whether the as-built condition is correct on site, and if there is a deviation, correct it on the spot. This greatly reduces rework such as taking data back to the office to compare with drawings and re-surveying if discrepancies are found. Data can also be shared with the office via the cloud, making information transfer between site and office real-time. Supervisors or clients at remote locations can instantly view conditions, improving decision-making speed.

• Improved safety: The need to manually transport heavy equipment or climb to high places is reduced, minimizing risky tasks. Visualization via AR reduces mistakes caused by misunderstandings on site, contributing to accident prevention and fewer near-miss incidents. Because everyone shares the same data, communication loss is reduced and safer construction management is achieved.

In this way, the new surveying style of smartphone × RTK achieves overwhelming efficiency and labor savings, dramatically lowering the barrier to surveying tasks. It overturns the conventional notion that surveying and as-built verification are only for specialists, bringing an era in which anyone on site can measure and verify based on data.

The Productivity Revolution Brought by the Smartphone Surveying Device "LRTK"

A representative solution of smartphone RTK surveying that attracted attention at the expo is "LRTK". LRTK is a device developed by a startup that originated from Tokyo Institute of Technology, and it is a small terminal that enables centimeter-class high-precision GNSS positioning simply by attaching it to a smartphone or tablet. Weighing only about 125 g and about 13 mm (0.51 in) thick, it is pocket-sized yet contains a battery and antenna, and is used by snapping it into a dedicated smartphone case (using an optional monopod allows height-direction correction at the push of a button). It was developed as a truly "surveying instrument you can carry anywhere at any time," aiming to be a one-per-person tool that can be casually used on site.

Attach LRTK to a smartphone and that smartphone instantly becomes a surveying device with centimeter-level accuracy. It supports the centimeter-level positioning augmentation service (CLAS) provided by Japan’s quasi-zenith satellite system "Michibiki," enabling stable high-precision positioning even in mountain areas where cellular signals are unavailable. In fact, during the Noto Peninsula earthquake in 2023, where communications infrastructure was disrupted, LRTK was effective: a single small device enabled rapid precise positioning, recording, and sharing of damage assessments. Such offline responsiveness is a major strength as a field tool.

LRTK’s functions are diverse, and the fact that construction, inspection, and recording can be completed with one device is revolutionary. Main features include:

• High-precision GNSS for single-point and continuous positioning: With a single button operation on the smartphone screen, you can measure and save coordinates (latitude, longitude, height) of any point. The app automatically converts to necessary coordinate systems such as plane rectangular coordinates or geoid heights, so there is no need for complex calculations on site. There is also a function to perform continuous positioning while walking, acquiring up to 10 points per second and obtaining track data, which is powerful for capturing longitudinal surface profiles or surveying an entire site.

• AR-based construction navigation: If design drawings or coordinate data of construction points are registered in the LRTK cloud, you can work on site while viewing the design model or target positions as AR overlays through the smartphone camera. For example, a virtual stake can be projected on the screen at the position where a pile should be driven, and the user simply follows app arrow guidance to that point to identify the exact pile-driving location. Because LRTK always knows its own position with cm level accuracy (half-inch accuracy), there is no worry of AR overlays shifting as the user moves. This intuitive "just look to stake out" function dramatically improves the efficiency and accuracy of piling and layout work.

• 3D point-cloud scanning and earthwork volume calculation: By linking with the LiDAR scanner or camera on iPhone/iPad, you can acquire 3D point-cloud data simply by walking the site. Thanks to LRTK’s high-precision position correction, each point is assigned an accurate absolute coordinate, minimizing the distortions that typically occur in walk-through scans. You can measure distances, areas, and volumes between any two points on the acquired point cloud on site, enabling immediate calculation of fill or excavation volumes. Uploading point cloud data to a cloud 3D viewer allows sharing via browser with equipment operators and designers, and makes it smooth to compare as-built conditions against construction plan models.

• Streamlined photo documentation and reporting: When survey photos are taken from the LRTK app on site, the photo files automatically include the high-precision coordinates of the shooting location and the camera orientation (azimuth). You can also enter notes at the time of shooting, and with one tap upload to the cloud so photos are plotted on a map showing exactly where and in which direction they were taken. This greatly reduces the previous labor of organizing photos taken with digital cameras in the office and pasting them on paper drawings, while preventing recording errors. The cloud also enables comparative display with photos taken at the same location previously, which is powerful for grasping long-term changes during infrastructure inspections.

• Cloud integration and data sharing: All information acquired by LRTK (coordinate data, point clouds, photos, etc.) can be uploaded directly from the site to the LRTK Cloud for centralized management. Office personnel can always view the latest data via a web browser without logging in, and positioning data can be downloaded in CSV or SIMA formats. Deliverables can be shared immediately with clients and subcontractors via URL links, minimizing the time required for report creation and data conversion. It becomes a data foundation that connects site and office in real time and contributes to faster decision-making.

With these many functions, LRTK comprehensively supports the measuring, staking out, and recording processes in surveying and construction with a single smartphone. Its ease of use and practicality drew many questions from construction management practitioners at the expo. While some visitors exclaimed in surprise, "I didn't know a smartphone could do this," many others reacted positively, saying, "This looks ready to use at our sites." The high level of interest in LRTK was evident.

LRTK Use Cases — How Sites Will Change

Here are specific examples of where LRTK is useful on site.

• Guidance for pile driving and layout: For pile driving and layout from reference points to prescribed positions, LRTK’s AR navigation function is highly effective. If pile position data based on design drawings are loaded into the app via the cloud, a virtual pile is displayed on the smartphone screen on site and the user is guided to the position, enabling accurate marking. Because anyone can reliably place piles without relying on experienced intuition, this leads to standardization of construction accuracy and prevention of rework.

• As-built surveying and as-built management: LRTK is also very useful for topographic surveys after earthworks and for as-built verification of structures. You can scan wide areas as 3D point clouds to obtain as-built data and overlay it with the design model to instantly check for excesses or shortfalls in as-built dimensions. Tasks that used to take half a day, such as spot measurements to check heights at necessary locations, can be greatly shortened. This directly speeds up quality control and construction cycles.

• Confirming locations of buried objects and structures: It is helpful for confirming routes of underground pipes and cables and accurately locating existing structures. Projecting buried pipe routes from drawings as AR while excavating reduces the risk of damaging existing pipes. Even in places where GPS signals do not reach, such as under bridges or overpasses, LRTK’s indoor positioning mode can measure the space below from temporarily acquired reference points. Because you can non-contact measure coordinates of high or hazardous areas that are out of reach, inspection and repair planning can be prepared safely and efficiently.

• Infrastructure inspection and maintenance: For routine inspections of road signs, slopes, and bridges, LRTK’s photo-positioning function is powerful. Photos tagged with latitude, longitude, and azimuth are accumulated on the cloud linked to a map. When re-inspecting the same spot in subsequent years, you can navigate back to the previously recorded coordinates and easily take photos with the same composition using AR orientation guidance. This makes comparison of deterioration over time immediately apparent and brings innovation to infrastructure asset maintenance.

• Municipal work and disaster response: LRTK is widely used in local government field work. For current condition surveys and boundary confirmation of urban infrastructure, municipal staff can perform surveying themselves with LRTK and share data immediately, reducing requests to external contractors and rework. For disaster site recording, LRTK, which operates even without network coverage, contributes to rapid initial surveys. Its small size and portability make it easy to carry to disaster sites, and some municipalities are already equipping it as an emergency survey tool. Because it enables efficient site response with limited personnel, expectations in the disaster prevention field are rising.

Thus, LRTK is gaining attention as a versatile tool that enhances on-site productivity and safety across all scenes—from construction preparation to as-built management, maintenance, and emergency disaster response.

Voices from the Field and Implementation Effects

On sites that have actually introduced LRTK, comments include: "The time required for surveying and as-built verification has shortened dramatically," "Tasks that previously required two or more people can now be done by one person, so work continues despite labor shortages," and "Creating paper photo logs is no longer necessary, and desk work after returning to the office has drastically decreased." A veteran surveying technician commented, "I feel more comfortable delegating to younger staff. The app guides them, so even newcomers can measure accurately, which is very helpful," reflecting that on-site work styles are certainly beginning to change.

At the expo, the LRTK booth was consistently crowded, and many visitors experienced the demo and were surprised by its ease and multifunctionality. Comments included, "I didn’t expect a smartphone could be used this much," and "This is the definitive solution for on-site DX," especially making it attractive as a low-barrier DX tool for small and medium-sized construction companies and municipal staff. The fact that initial costs can be lower compared to specialized equipment was also appreciated, prompting comments such as, "We’d like everyone on our site to have one." Some construction companies and municipalities have already begun adopting LRTK, creating a quiet boom as a trump card for promoting on-site DX. LRTK’s technology is also registered in the Ministry of Land, Infrastructure, Transport and Tourism’s New Technology Information System (NETIS), which further supports its adoption in public works.

Conclusion: The Future of On-Site DX Opened by LRTK

The latest technologies showcased at expos like the Construction and Surveying Productivity Improvement Expo present us with a vision of the future of construction sites. The smartphone surveying device LRTK can be said to be an innovative tool symbolizing on-site DX. Work that used to rely on the experience and intuition of veterans is being replaced by digital data, and an era in which anyone can perform site tasks accurately and efficiently is right around the corner.

LRTK is expected to play an active role across a wide range of scenes, from simple daily surveying to management of large-scale construction and disaster response. As an answer to the construction industry’s challenges of improving productivity and ensuring safety, smartphone × DX solutions like this are a strong candidate. By permeating the digital revolution into every corner of the field and dramatically improving productivity and quality, LRTK is sure to assume the role of a leader at the forefront of on-site DX and become the standard-bearer of the productivity revolution. It will be interesting to see how widely such tools spread and how much they contribute to further advances in on-site DX.