Construction & Survey Productivity Improvement Expo — On the Front Lines of On-site DX: Smartphone Survey Device LRTK Sparks a Productivity Revolution

Against the backdrop of efforts to improve productivity on construction sites and the broader trend toward DX (digital transformation), the annual "Construction & Survey Productivity Improvement Expo" (commonly: CSPI-EXPO) has become a gathering place for the industry's most advanced technologies. This article focuses on one of the latest trends at the forefront of on-site DX—the smartphone surveying device "LRTK"—and introduces how it can transform fieldwork in construction, inspection, and surveying.

The Construction & Survey Productivity Improvement Expo and the background of industry DX

The Construction & Survey Productivity Improvement Expo is an exhibition where construction industry stakeholders (construction managers, ICT promotion staff, surveying companies, municipal officials, etc.) gather to experience new technologies and services that improve productivity. Recently, the construction industry has faced severe labor shortages, stalled skills transfer, and the need for stricter safety management, all of which have accelerated construction DX (digital transformation) through proactive use of ICT technologies. Policies such as *i-Construction*, promoted by the Ministry of Land, Infrastructure, Transport and Tourism, have strongly supported digitalization and labor saving across the site—from surveying to construction, inspection, and maintenance. Declining labor force and the aging of workers are also serious issues, making DX a promising solution to these challenges. It has become a key to a productivity revolution on-site.

In response to these trends, CSPI-EXPO features many cutting-edge technologies that support the construction sites of the future, such as drone surveying, automated transport robots for construction machinery, AI-based image analysis, and AR/VR simulations. For example, the 6th Construction & Survey Productivity Improvement Expo held at Makuhari Messe in May 2024, themed "The Future of Construction," showcased a wide range of solutions addressing industry challenges such as decarbonization and energy saving (greening), labor saving and digital construction, and quality control. Attendance has increased year by year, and the 7th edition in 2025 (held internationally) drew about 57,000 visitors. Among the exhibits this year, one solution that attracted particular attention was a simple, high-precision positioning solution using smartphones. The device that stopped many attendees in their tracks—due to the impact of being able to complete surveying with a smartphone—was a smartphone surveying device called "LRTK."

The emergence of smartphone RTK surveying technology and how it differs from traditional methods

Traditional surveying typically used dedicated equipment such as total stations and GPS receivers and was usually performed by multiple people over long periods. For example, with a total station, one person sets up the instrument while another holds a prism at the target point; measuring many points could take an entire day. Additionally, survey results had to be brought back to the office for comparison with drawings, causing inefficient back-and-forth between the field and the office.

However, in recent years, miniaturization of high-precision GNSS positioning technology and advances in communications infrastructure have made it possible to achieve centimeter-level positioning with a smartphone. RTK (Real Time Kinematic) GNSS surveying achieves horizontal accuracy on the order of 2–3 cm by applying real-time corrections to satellite positioning error information between a base station (known point) and a rover. By attaching an RTK receiver to a smartphone, the several-meter errors of a standalone smartphone GPS can be reduced to a few centimeters, delivering surveying-level accuracy in a palm-sized device comparable to traditional fixed instruments. Furthermore, combining this precise positioning with AR (augmented reality) technology enables an innovative method in which a single operator can intuitively perform surveying and staking-out tasks.

The main differences from traditional methods are as follows:

• Dramatic reduction in required manpower and time: Total station surveying typically required at least two people, whereas a smartphone + RTK receiver enables field surveying to be completed by a single operator. GNSS allows direct measurement even in locations with poor line of sight, and multiple point measurements can be finished in a short time. As a result, the days spent on surveying and as-built management can be greatly reduced.

• Reduced dependence on skilled experience: Traditionally, veteran technicians handled equipment operation, reading, and recording, and experience was essential for accurate measurements. Smartphone surveying uses dedicated apps that guide measurement procedures and automate data recording, making it intuitive for anyone to operate. There is no need to follow paper drawings while tracking dimensions—just follow on-screen prompts and press a button at the point to be measured to obtain coordinates. This reduces human reading errors and recording mistakes, lightens the burden on veterans, aids skills transfer to younger staff, and helps address labor shortages.

• Real-time on-site verification and sharing: Acquired survey data can be displayed on the smartphone screen as AR overlays, allowing verification against design drawings or past data on-site. You can immediately check whether as-built conditions are acceptable and correct any deviations on the spot. The need to bring data back to the office for drawing comparisons and potentially re-measuring is greatly reduced. Data can also be shared with the office via the cloud, enabling real-time communication between the field and office. Remote supervisors or clients can be shown conditions instantly, which speeds decision-making.

• Improved work safety: The need to manually transport heavy equipment or climb to heights is reduced, minimizing risky tasks. AR visualization helps reduce mistakes caused by misinterpretation on-site, contributing to accident prevention and fewer near-miss incidents. With everyone working from the same shared data, communication losses are reduced and safer construction management is achieved.

This new surveying style—smartphone × RTK—achieves overwhelming efficiency and labor savings, lowering the barrier to surveying work. It overturns the conventional notion that "surveying and as-built checks are only for specialists," bringing an era where 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 drew attention at the expo is "LRTK." Developed by a startup from Tokyo Institute of Technology, LRTK is a device that, when attached to a smartphone or tablet, enables centimeter-class high-precision GNSS positioning. Weighing only about 125 g and about 13 mm thick, this pocket-sized device contains a battery and antenna and attaches with one touch to a dedicated smartphone case (an optional monopod can be used to apply height correction with a single button). It was developed as a true "surveying instrument you can carry anywhere, anytime," aiming to be a one-device-per-person tool that can be casually used on-site.

Attach LRTK to a smartphone and the phone instantly becomes a surveying instrument 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 without mobile coverage. In fact, during the 2023 Noto Peninsula earthquake, LRTK proved useful in disaster areas where communications infrastructure was down—one small device enabled precise surveying, rapid recording, and sharing of damage assessments. This offline responsiveness is a major strength as a field tool.

LRTK offers a wide range of functions and is revolutionary in that it can handle surveying, inspection, and recording with a single unit. Key features include:

• High-precision GNSS for single-point and continuous positioning: With a single button on the smartphone screen, users can measure and save coordinates (latitude, longitude, height) for any point. The app automatically converts to the required coordinate systems—such as plane rectangular coordinates or geoid height—so no complex calculations are needed on-site. Operators can also perform continuous positioning while walking, capturing up to 10 points per second to obtain track data, which is powerful for capturing longitudinal surface profiles or surveying entire sites.

• AR-based construction navigation: If design drawings or target coordinate data are registered in the LRTK Cloud, users can work on-site with the design model or target positions AR-displayed through the smartphone camera. For example, a virtual stake can be projected on the screen at the position "drive a pile here," and the user simply follows app arrows to the precise location to identify the pile-driving point. Because LRTK continuously knows its position at centimeter accuracy, AR overlays do not drift as the user moves. This intuitive "see-and-place" capability dramatically improves the efficiency and accuracy of piling and layout tasks.

• 3D point-cloud scanning and earthwork volume calculation: LRTK integrates with iPhone/iPad LiDAR scanners and cameras to acquire 3D point-cloud data simply by walking the site. Thanks to LRTK's high-precision position correction, each point is assigned accurate absolute coordinates, minimizing the distortions typically associated with walk-through scans. Users can measure distances, areas, and volumes between arbitrary points on the acquired point cloud on-site, enabling immediate calculation of fill or excavation volumes. Uploading point clouds to a cloud-based 3D viewer allows operators and design staff to share data via a browser and smoothly compare as-built conditions against design models.

• Streamlined photo documentation and reporting: Photos taken from the LRTK app automatically embed high-precision coordinates and camera orientation (bearing). Notes can be added at the time of capture, and a one-tap upload to the cloud plots where and in what direction each photo was taken on a map. This greatly reduces the prior effort of organizing digital camera photos at the office and pasting them onto paper drawings, and helps prevent documentation errors. The cloud platform also allows side-by-side comparison with past photos taken at the same location, which is powerful for tracking aging in infrastructure inspections.

• Cloud integration and data sharing: All information acquired with LRTK (coordinate data, point clouds, photos, etc.) can be uploaded directly from the field to the LRTK Cloud for centralized management. Office staff can view the latest data from a web browser without logging in, and positioning data can be downloaded in CSV or SIMA formats. Results can be shared immediately with clients or partner companies via URL links, minimizing time spent on report creation and data conversion. LRTK thus becomes a data backbone connecting field and office in real time and helps speed up decision-making.

With these capabilities, LRTK comprehensively supports on-site processes such as "measuring," "indicating," and "recording" with a single smartphone. Its ease of use and practicality drew many questions from construction managers at the expo. Reactions ranged from astonishment—"I didn't know you could do this much with a smartphone"—to practical enthusiasm—"This could be used immediately on our sites"—demonstrating strong interest in LRTK.

LRTK use cases — How the field will change

Here are examples of specific situations where LRTK can be useful on-site:

• Guidance for pile-driving and layout: LRTK's AR navigation is powerful for pile-driving and layout from reference points to predetermined positions. If pile position data from design drawings is loaded into the app via the cloud, a virtual pile appears on the smartphone screen and the user is guided to the site to mark it. Anyone can place piles accurately without relying on veteran intuition, leading to uniform construction accuracy and reduced rework.

• As-built surveying and as-built management: LRTK is valuable for measuring site topography and checking as-built conditions after earthworks. Scanning wide areas into 3D point clouds and overlaying them with design models allows immediate checks for excesses or shortages in as-built dimensions. Tasks that previously took half a day for spot checks can be dramatically shortened, accelerating quality control and construction cycles.

• Verification of buried utilities and structures: LRTK helps confirm routes of underground pipes and cables and the precise locations of existing structures. Projecting buried pipe routes onto the surface with AR during excavation reduces the risk of damaging existing utilities. Even under bridges or overpasses where GPS signals are weak, LRTK's indoor positioning mode can measure the underlying space from temporarily established reference points. Non-contact coordinate measurement of inaccessible heights and hazardous areas enables safe and efficient inspection and repair planning.

• Infrastructure inspection and maintenance: For routine inspections of road signs, slopes, bridges, and the like, LRTK's photo-positioning function is highly effective. Photos tagged with coordinates and orientation are stored and linked to maps in the cloud. When revisiting the same spot in subsequent years, users can navigate precisely to the prior recorded coordinates and even replicate the same framing using AR orientation guidance. This makes it easy to compare deterioration over time and brings innovation to infrastructure asset maintenance.

• Municipal operations and disaster response: LRTK is widely used in local government fieldwork. For current-condition surveys and boundary checks, municipal staff can perform measurements themselves and share data immediately, reducing the need for external contractors and rework. In disaster response, LRTK's offline capability contributes to rapid initial surveys even without communications. Its portability makes it easy to carry into affected areas, and some municipalities are equipping LRTK as an emergency survey tool. Because it enables efficient field response with limited personnel, expectations are rising in the disaster preparedness domain.

In these ways, LRTK is attracting attention as a versatile tool that enhances productivity and safety across every phase—from construction preparation and as-built management to maintenance and emergency disaster response.

Voices from the field and the effects of adoption

On sites that have adopted LRTK, common feedback includes, "The time required for surveying and as-built checks has dramatically decreased," "Work that used to require two or more people can now be done by one, keeping operations going despite labor shortages," and "Creating paper photo ledgers is no longer necessary, drastically reducing desk work after returning to the office." A veteran surveyor commented, "I feel confident leaving work to younger staff. The app guides them, so even newcomers can measure accurately," showing that on-site working styles are indeed beginning to change.

The LRTK booth at the expo was busy throughout the event, with many attendees experiencing demos and expressing surprise at its ease of use and multifunctionality. Comments included, "I didn't expect a smartphone could do this," and "This is the definitive tool for on-site DX." It appeared particularly attractive to small and medium-sized construction companies and municipal officials as a low-barrier DX tool. Its lower upfront cost compared to dedicated instruments was also praised, with some saying, "We want everyone on-site to have one." Adoption by some construction companies and municipalities has already begun, creating a quiet boom as a trump card for promoting on-site DX. LRTK's technology is also registered with the Ministry of Land, Infrastructure, Transport and Tourism's New Technology Information System (NETIS), further encouraging adoption in public works.

Conclusion: The future of on-site DX opened by LRTK

The latest technologies showcased at exhibitions like the Construction & Survey Productivity Improvement Expo give us a glimpse of construction sites' future. The smartphone surveying device LRTK stands out as an innovative tool symbolizing on-site DX. Tasks that once relied on veterans' experience and intuition are being replaced by digital data, and an era in which anyone can perform accurate and efficient on-site work is approaching.

LRTK is expected to play an active role in everything from everyday simple surveys to large-scale project management and disaster response. As a smartphone × DX solution, it represents a compelling answer to the construction industry's challenges of improving productivity and ensuring safety. By spreading digital transformation to every corner of worksites and dramatically enhancing productivity and quality, LRTK is sure to become a leading force on the front lines of on-site DX, spearheading a productivity revolution. It will be important to watch how widely such tools are adopted and how they further drive the progress of on-site DX.