CSPI Spotlight: Easy 3D Recording with a Smartphone Makes DX for Structure Maintenance a Reality

At the large construction and surveying exhibition CSPI-EXPO (Construction and Surveying Productivity Improvement Expo), the latest technologies that lead to on-site DX attract attention every year. At this year’s CSPI, solutions that enable easy 3D recording and surveying with a single smartphone—and that can also be used for structure maintenance—were especially in the spotlight. Tasks that once required specialized equipment and craftsman skill can now be completed with a smartphone, and the digital transformation (DX) of construction sites is finally becoming a reality.

By utilizing smartphone LiDAR scanners and high-precision GPS, site topography and structures can be recorded on the spot as three-dimensional data, allowing for detailed measurement and comparison later. Advances in these digital technologies are dramatically simplifying surveying and recording work that used to require many personnel and considerable time.

Acceleration of Construction DX and CSPI-EXPO

In the construction industry, severe labor shortages and the aging of workers have progressed in recent years, and the stagnation of skill transfer has become a serious issue. Thorough safety management is also required, making the use of digital technologies on sites an urgent measure to overcome these situations. Supported by initiatives such as the Ministry of Land, Infrastructure, Transport and Tourism-led *i-Construction*, digitization and labor-saving of tasks from surveying to construction and maintenance have been accelerating. Held against this background, CSPI-EXPO brings together industry stakeholders—from construction managers and survey technicians to municipal officials—in one place to experience solutions that improve productivity. Many advanced technologies are exhibited, including drone surveying, construction machinery robots, AI image analysis, and AR/VR simulation, and the event is always very popular.

The 6th CSPI-EXPO in 2024 (held at Makuhari Messe) had the theme “The Future of Construction,” and introduced products and services addressing industry issues such as decarbonization and energy saving, labor saving and digital construction, and quality control. Attendance has been increasing year by year, and about 57,000 people attended the 7th International CSPI-EXPO in 2025. Among the exhibits, one of the most eye-catching solutions was the smartphone-based easy high-precision positioning solution. The impact of “surveying completed with a smartphone” drew many visitors to a device called LRTK, a smartphone surveying device.

The Impact of Surveying and 3D Scanning Completed with a Smartphone

Traditionally, surveying and 3D measurement have used expensive dedicated equipment such as total stations and GPS receivers, requiring multiple people and considerable time. For example, using a total station typically requires one person to set up the instrument while another stands at the target point holding a prism, and measuring many points can take an entire day. Post-processing—bringing measured data back to the office for comparison and organization against drawings—was also indispensable. Such labor- and skill-intensive surveying work was difficult to streamline because it required experienced technique.

However, recent miniaturization of high-precision GNSS (global navigation satellite) technology and improvements in communications infrastructure have brought an era when centimeter-level positioning with a smartphone is possible. By importing RTK (Real Time Kinematic) positioning data into a smartphone, the error of built-in GPS, which used to be on the order of several meters, has been reduced to several centimeters, enabling palm-sized devices to achieve accuracy comparable to stationary surveying equipment. Furthermore, combining a smartphone camera with AR (augmented reality) technology creates a revolutionary method that allows a single person to intuitively perform surveying and positioning for construction layout.

At the CSPI venue, the fact that “surveying can be completed with a smartphone” made a huge impression on visitors. The arrival of smartphone surveying, overturning conventional wisdom, prompted comments such as “this is the definitive solution for on-site DX,” and demonstration booths were crowded throughout the event. For small and medium-sized construction companies and municipal officials in particular, the idea that they could perform surveying (so-called “iPhone surveying”) and 3D scanning with a handheld iPhone—without purchasing expensive dedicated equipment—was attractive, and many said they wanted to introduce it on their sites immediately.

What the Smartphone Surveying Device “LRTK” Is

A leading contributor to this smartphone surveying capability—and a highlight at CSPI—is LRTK. LRTK is a compact mobile positioning device developed by a startup originating from Tokyo Institute of Technology, and when attached to the back of a commercially available iPhone or iPad it enables centimeter-level GNSS positioning. The device weighs approximately 125 g and is only about 13 mm (0.51 in) thick. It is a pocket-size design with a built-in battery and high-performance antenna, and it can be attached to a dedicated smartphone case with a single touch, making it highly portable. It aims to be a “surveying instrument you can carry anywhere” and become a one-per-person site tool. Using an optional monopod (pole) allows height offset correction with one tap, making ground elevation measurement simple.

When LRTK is attached to a smartphone, the phone instantly transforms into a surveying instrument with centimeter-level accuracy (half-inch accuracy). It supports Japan’s Quasi-Zenith Satellite System “Michibiki” centimeter-level positioning augmentation service (CLAS), enabling stable high-precision positioning even in mountainous areas without network coverage. In practice, during the 2023 Noto Peninsula earthquake, LRTK proved useful in disaster areas where communications infrastructure was down: a single small device enabled rapid precise positioning and 3D recording and sharing of damage information. Its ease of use without the need for training and its significantly lower cost compared to conventional equipment have driven adoption across civil engineering, construction, surveying, and infrastructure management fields. LRTK has also been adapted to the MLIT’s 3D as-built management guidelines and registered in the New Technology Information System (NETIS), raising expectations for its use in public works.

Main Functions Enabled by LRTK

LRTK not only improves positioning accuracy, but also strongly supports on-site DX through a variety of functions integrated with smartphone apps and the cloud. Here are the main functions that allow a single smartphone to “measure,” “display,” and “record.”

• Centimeter-level high-precision positioning (single point and continuous): With the tap of a button on the smartphone screen, you can measure and save the coordinates (latitude, longitude, and elevation) of any point. The app automatically converts to the required coordinate systems (such as plane rectangular coordinates or geoid height), so there is no need for troublesome calculations on site. It is also possible to perform continuous positioning while walking, recording up to 10 points per second to log tracks, which is effective for capturing roadway longitudinal profiles and surveying the topography of entire sites.

• AR-based construction navigation: If design drawings or coordinates of construction points are registered in the LRTK cloud, you can work on site with AR overlays of design models and target positions through the smartphone camera. For example, if pile-driving positions are shared, a virtual pile will appear on the screen and the user can simply follow arrow guidance to reach the exact location. Because the smartphone always knows its position with cm level accuracy (half-inch accuracy), there is no worry about AR overlays drifting as with conventional AR. This enables intuitive, visually clear high-precision positioning.

• 3D point cloud scanning and as-built measurement: By linking with the LiDAR scanner and camera built into iPhones and iPads, you can obtain surrounding 3D point cloud data simply by walking the site. Thanks to position correction by LRTK, each point is assigned an accurate absolute coordinate, minimizing distortions that commonly occur during walk-around scanning. You can measure distances between any two points, areas, and volumes on the acquired point cloud on the spot, making earthwork volume calculations for fills and excavations immediate. Uploading to the cloud 3D viewer for sharing allows heavy equipment operators and design staff to check the current conditions via a browser, and overlaying with design models makes as-built comparison smooth.

• Geotagged photo records: When you take site photos with the smartphone, the photo file is automatically tagged with the high-precision coordinates of the shooting location and the camera orientation (bearing). If you enter notes and upload at the time of shooting, the photos are organized and stored on a map showing “when, where, and in which direction” each photo was taken. Previously, organizing photos taken with a digital camera and cataloging them required extra work, but LRTK completes the record on site and prevents misplacement or incorrect attachment of photos. On the cloud, photos taken at the same location during past inspections can be displayed side by side, making it easy to compare aging and deterioration of infrastructure.

• Cloud sharing and CAD/BIM integration: All data obtained with LRTK (position points, point clouds, photos, etc.) can be uploaded to the LRTK cloud for centralized management. Data is shared instantly between the field and the office, allowing the latest status to be grasped remotely. Stakeholders can view results via a web browser, download survey data in SIMA or CSV formats as needed, or import them into CAD software. Because data can be shared with clients and partner companies via URL links, the time required for report preparation and format conversion is reduced.

New Value Created by Easy 3D Recording

Easy 3D recording with LRTK is highly effective for post-construction as-built management and quality verification. For example, after earthwork completion you can scan a wide area with 3D point clouds to obtain current condition data and compare it on the spot by overlaying it with a design model registered in the cloud. You can instantly check as-built dimensions of fills or structures and perform touch-ups immediately if there are discrepancies. Traditionally, surveying teams measured the site and then compared with drawings in the office, arranging corrections on later days; with LRTK you can determine as-built acceptability in real time, dramatically reducing rework. Because volumes and heights can be directly measured from point cloud data, earthwork calculations and elevation checks are completed in a short time.

Storing acquired 3D data and coordinate information in the cloud as evidence makes later inspection attendances and report preparation smooth. By enabling quality assessment based on data even for those who are not experienced survey technicians, LRTK can raise the overall level of site quality management. Making 3D data accessible to everyone on a daily basis would be a revolutionary change for the construction industry.

DX Use for Structure Maintenance

In Japan, infrastructure structures such as roads, bridges, and tunnels built during the period of high economic growth are aging, and a huge amount of inspection and maintenance must be carried out with limited personnel. Efficiency improvements through DX are urgently needed in infrastructure maintenance as well, and LRTK can be effectively used in these fields. LRTK brings DX benefits not only to construction and surveying but also to inspection and maintenance tasks for structures such as bridges, tunnels, and slopes. For example, in routine inspections of road signs and bridges, photos taken with LRTK-recorded shooting coordinates and orientation allow staff to immediately identify the exact location and direction when reviewing photos in the office later. When revisiting the same point in subsequent years, the smartphone’s coordinate navigation function can guide you straight to the previously recorded coordinates, and AR guidance makes it easy to retake photos with the same composition and angle as before. This simplifies comparisons of aging and deterioration and brings revolutionary efficiency improvements to infrastructure asset maintenance.

Moreover, measurement is possible even inside tunnels or under bridges where GPS signals do not reach by using an indoor positioning mode that acquires reference points near the entrance and performs relative positioning. Measurements at heights or dangerous locations that are out of reach can also be carried out safely using AR-based non-contact surveying. For example, measuring the height of a bridge girder or displacement in a tunnel ceiling can be completed by pointing a smartphone from the ground and capturing the point. Tasks that used to require working at heights with aerial work platforms or accessing hazardous locations manually are now streamlined by LRTK, greatly improving worker safety. Keeping 3D scan data of structures in the cloud helps produce detailed inspection records and plan future repairs. As maintenance management shifts from paper drawings and handwritten records to digital data, decisions can be made based on objective numerical and visual information rather than subjective intuition.

Efficiency and Labor Saving Effects on Site Operations

DX using a smartphone and LRTK has a dramatic effect on site efficiency and labor saving. Surveying and as-built confirmation work that previously required two to three people can now be completed by one person, and the time required is greatly reduced. Field reports from sites that introduced LRTK include comments such as “as-built measurements that used to take half a day now finish in tens of minutes” and “pile positioning that used to require two people can now be done by one,” demonstrating significant improvements. Even with a shortage of experienced survey technicians, anyone on site can perform accurate surveying, directly addressing labor shortage issues.

Since the dedicated app guides measurement procedures and automates data recording, tasks have become something “anyone can do” without relying on veteran intuition or experience. Young and new staff can obtain high-precision results simply by following on-screen instructions, reducing the burden of checks and training by senior staff. The tedious tasks of searching for survey points with paper drawings and notebooks and manually copying measured values are reduced, helping to prevent human error. Data acquired on site is immediately shared to the cloud, cutting down the time needed to organize and report after returning to the office. Time savings from surveying to reporting streamline the entire construction cycle, allowing the freed-up time to be used for other tasks.

There are also major safety benefits. Opportunities to carry heavy equipment up to heights are reduced, and surveying on dangerous cliffs or slopes can be conducted remotely, lowering worker risk. Visualizing buried utilities with AR before construction prevents accidental damage to existing pipes. Constant data connectivity between the site and the office reduces recognition gaps and enables all stakeholders to work safely with the latest information, which is expected to reduce near-miss incidents and prevent accidents.

LRTK-based smartphone DX tools are easy to introduce from a cost perspective and are being adopted by companies and organizations of various sizes. LRTK is also available as a monthly subscription hardware service, which reduces initial costs and is attractive to small and medium-sized businesses. Visitors at the exhibition commented, “I didn’t think a smartphone could be used like this” and “this could be the trump card for on-site DX,” with reactions such as “I want to issue these to all site staff.” In municipal work, there are examples where staff themselves perform current-condition surveys and boundary checks for roads and parks using LRTK, reducing outsourcing and rework for site confirmation. Some municipalities have begun equipping LRTK as an initial survey tool in disasters, and construction companies are increasingly introducing it as part of ICT construction. Being registered in the Ministry of Land, Infrastructure, Transport and Tourism’s New Technology Information System (NETIS) also lowers barriers to use in public projects, acting as a tailwind for DX promotion.

Expanding LRTK Use with Simple Surveying

Beyond advanced 3D measurement and AR, LRTK is also powerful for everyday simple surveying. For example, using an optional monopod (simple pole), you can obtain accurate coordinates of a ground point by simply placing the pole tip on the desired point and pressing a button. The app automatically compensates for the pole length offset, allowing high-precision single-point positioning without having to hold the smartphone just above the ground. Even in confined sites or locations with significant elevation differences, one person can easily mark points individually, so you can perform fine current-condition checks or as-built verification immediately when needed. LRTK meets the “I just want to measure this quickly” needs that previously required a specialized surveying team, greatly expanding the scope of data utilization on site.

LRTK also has a continuous positioning log function, allowing a worker to obtain continuous longitudinal and cross-sectional ground elevation data just by walking a site, enabling rapid surveying of large-area terrain. From daily inspections to immediate post-disaster damage recording, LRTK enables accurate surveying on the spot, becoming a reliable partner on site.

Now that so much can be achieved with a single smartphone, on-site DX from surveying and measurement to structure maintenance has steadily become a reality. LRTK, which attracted attention at CSPI, is a frontline solution that will strongly support productivity improvements and safety management at future construction sites. At future CSPI-EXPOs, smartphone-based DX solutions are expected to evolve further and become industry standards. The era in which digital reform using familiar devices dramatically improves productivity and safety on site is just around the corner.