CSPI Spotlight: Easy 3D Recording with a Smartphone, DX for Structural Maintenance Becomes Reality

At the large construction and surveying exhibition CSPI-EXPO (Construction and Surveying Productivity Improvement Expo), the latest technologies that drive on-site DX attract attention every year. Especially at this year’s CSPI, solutions that allow easy 3D recording and surveying with just a smartphone, applicable to structural maintenance, drew the spotlight. Tasks that once required specialized equipment and artisan skills can now be completed with a smartphone, and the digital transformation (DX) of construction sites is finally becoming a reality.

By leveraging smartphone LiDAR scanners and high-precision GPS, site topography and structures can be recorded on the spot as 3D data, enabling detailed measurements and comparisons afterward. Advances in these digital technologies are dramatically simplifying surveying and recording work that previously required large amounts of labor and time.

Acceleration of Construction DX and CSPI-EXPO

In the construction industry, severe labor shortages and an aging workforce have advanced in recent years, and the stagnation of skill transfer has become a serious issue. Thorough safety management is also demanded, so leveraging digital technologies on-site has become an urgent measure to break through these challenges. Supported by initiatives such as the Ministry of Land, Infrastructure, Transport and Tourism–led *i-Construction*, the digitalization and labor-saving of tasks from surveying to construction and maintenance have accelerated. Against this backdrop, CSPI-EXPO brings together construction managers, survey technicians, and municipal officials so industry stakeholders can experience productivity-improving solutions firsthand. Many cutting-edge technologies—drone surveying, construction machinery robots, AI image analysis, AR/VR simulation—are exhibited, and the event is always very popular.

The 6th CSPI-EXPO in 2024 (held at Makuhari Messe) adopted “The Future of Construction” as its theme, showcasing products and services addressing industry challenges such as decarbonization and energy saving, labor saving and digital construction, and quality control. Attendance has been increasing year by year; the 7th International CSPI-EXPO in 2025 drew about 57,000 participants. Among the exhibits, the solution that particularly attracted attention was the high-precision positioning solution using a smartphone. The impact of “surveying completed with a smartphone” drew many visitors to the demo booth for the smartphone surveying device called LRTK.

The Impact of Smartphone-Completed Surveying and 3D Scanning

Traditionally, surveying and 3D measurement used expensive specialized equipment such as total stations and GPS receivers and typically required multiple people and considerable time. For example, with a total station one person sets up the instrument while another stands at the target point with a prism, and measuring many points can take a full day. Post-processing—bringing data back to the office to cross-check and organize with drawings—was also essential. These labor- and time-intensive tasks demanded skilled technicians, making efficiency gains difficult.

However, recent miniaturization of high-precision GNSS technology and improvements in communications infrastructure have brought an era where centimeter-level positioning is possible with smartphones. By importing RTK (Real Time Kinematic) positioning data into a smartphone, the errors of built-in GPS that were previously on the order of meters can be reduced to centimeters, achieving handheld accuracy comparable to stationary surveying instruments. Combining smartphone cameras with AR (augmented reality) technology creates a groundbreaking method that enables even a single person to intuitively perform surveying and layout work.

At CSPI, the fact that “surveying can be completed with a smartphone” gave visitors a strong shock. With smartphone surveying overturning conventional wisdom, many exclaimed it was “the definitive on-site DX,” and demo 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 their own iPhones without investing in costly specialized equipment was very attractive, and many said they wanted to introduce it to their sites immediately.

What is the Smartphone Surveying Device “LRTK”?

A key enabler of this smartphone surveying is the LRTK, which drew attention at CSPI. LRTK is a compact mobile positioning device developed by a startup spun out of Tokyo Institute of Technology; simply attaching it to the back of a commercially available iPhone or iPad enables centimeter-level high-precision GNSS positioning. The unit weighs about 125 g and is only around 13 mm thick. It’s pocket-sized with an internal battery and high-performance antenna, and easily snaps into a dedicated smartphone case, offering excellent portability. It aims to become a “surveying instrument you can carry anywhere,” a one-per-person on-site tool. Using an optional monopod (pole) allows height-offset correction with one tap, making ground height measurement simple.

Once attached to a smartphone, that instant the phone is transformed into a surveying instrument with centimeter accuracy. It supports the centimeter-level augmentation service (CLAS) provided by Japan’s Quasi-Zenith Satellite System “Michibiki,” enabling stable high-precision positioning even in mountainous areas outside of cellular coverage. In fact, following the 2023 Noto Peninsula earthquake, where communications infrastructure was disrupted, LRTK was effective: a single small device enabled rapid precise positioning and 3D recording and sharing of damage conditions. Its ease of use without the need for training and its cost, which is far lower than conventional equipment, have driven adoption across civil engineering, construction, surveying, and infrastructure management. LRTK has also been made compatible with the Ministry of Land, Infrastructure, Transport and Tourism’s 3D as-built management guidelines and registered in the New Technology Information System (NETIS), raising expectations for 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 linked with smartphone apps and the cloud. Here are the main functions that allow a single smartphone to complete “measure, indicate, and record.”

• Centimeter-level high-precision positioning (single point and continuous): With a tap on the smartphone screen, you can measure and save coordinates (latitude, longitude, height) of any point. The app automatically converts to the required coordinate system (such as plane rectangular coordinates or geoid height), so no cumbersome calculations are needed on site. You can also record trajectories by continuous positioning while walking—up to 10 points per second—making it powerful for capturing longitudinal profiles of roads or surveying entire site topography.

• Construction navigation with AR: If design drawings or coordinate data for construction points are uploaded to the LRTK cloud, you can view the design model or target positions in AR through the smartphone camera on-site while working. For example, if pile-driving positions are shared, a virtual pile will appear on the screen and the user simply follows arrow guidance to reach the exact location. Because the smartphone always knows its position to centimeter accuracy, there is no worry about AR misalignment as with conventional AR. This enables intuitive, “what you see is what you get” high-precision layout.

• 3D point cloud scanning and as-built measurement: Linked with the LiDAR scanner and camera built into iPhone or iPad, you can obtain surrounding 3D point cloud data simply by walking the site. Thanks to position correction by LRTK, each point is assigned accurate absolute coordinates, minimizing distortions that often occur when stitching walking scans. You can measure distances, areas, and volumes between any two points on the acquired point cloud on the spot, allowing immediate earthwork volume calculations for fills and excavations. Uploading to the cloud 3D viewer for sharing lets machine operators and designers check site conditions via a browser and smoothly compare as-built conditions against design models.

• Geotagged photo records: When you take photos on-site with the smartphone, the photo files automatically include high-precision coordinates and camera orientation (bearing). If you enter notes and upload to the cloud at the time of shooting, the photos are organized and stored on a map showing “when, where, and which direction” each photo was taken. Previously, photos taken with digital cameras had to be organized and ledgered later, but with LRTK, records can be completed on-site, preventing misplacement or incorrect attachment of photos. In the cloud you can display photos taken at the same location during past inspections side by side, making it easy to compare aging changes for infrastructure inspections.

• Cloud sharing and CAD/BIM integration: All data acquired with LRTK (survey points, point clouds, photos, etc.) can be uploaded to the LRTK cloud for centralized management on the spot. Data is shared instantly between the site and the office, allowing remote stakeholders to understand the latest situation. Stakeholders can view results from a web browser and download survey data in SIMA or CSV formats as needed, or import into CAD software. Because data can be shared with clients and subcontractors via URL links, time spent preparing reports and converting formats 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 checks. For example, after earthworks completion, you can scan wide areas as a 3D point cloud to acquire current data and overlay and compare it on the spot with a design model pre-registered in the cloud. You can immediately check as-built dimensions of fills and structures and, if there are excesses or shortages, perform corrections right away. Previously, survey crews measured the site and then checked drawings in the office, with corrections made on a later date; with LRTK you can determine as-built acceptability in real time, dramatically reducing rework. Because volumes and heights can be measured directly from point cloud data, earthwork quantity calculations and elevation checks are completed quickly.

Acquired 3D data and coordinate information can be stored in the cloud as evidence, smoothing future inspection attendance and report preparation. With an environment where even non-expert surveyors can evaluate quality based on data, overall site quality control levels are expected to rise. Making 3D data handling routine for everyone would be a revolutionary change for the construction industry.

DX Application to Structural Maintenance

In Japan, infrastructure such as roads, bridges, and tunnels built during the high economic growth period is aging, and limited personnel must inspect and maintain vast assets. Efficiency through DX is an urgent issue in infrastructure maintenance as well. LRTK can be effectively applied to these sites. Beyond construction and surveying, LRTK brings DX benefits to inspection and maintenance of structures such as bridges, tunnels, and slopes. For example, during routine inspections of road signs or bridges, photos taken with LRTK record coordinates and orientation, allowing office staff to immediately identify the exact location and direction when reviewing photos later. When re-surveying the same point in subsequent years, you can navigate back to the previously recorded coordinates with the smartphone’s coordinate navigation and easily retake photos in the same composition and angle guided by AR. This simplifies comparisons of aging deterioration and brings revolutionary efficiency to infrastructure asset maintenance.

Additionally, in tunnels or under bridges where GPS signals don’t reach, measurement is possible using an indoor positioning mode that acquires reference points near the entrance and performs relative positioning. Measurements at unreachable heights or dangerous locations can also be done safely with non-contact surveying using AR. For example, height of bridge girders or displacement of tunnel ceilings can be measured from the ground simply by pointing the smartphone at the target. Tasks that previously required high-access machinery or manual access to hazardous spots are now labor-saving with LRTK, greatly improving worker safety. Keeping 3D scan data of structures in the cloud helps with detailed inspection records and planning future repairs. Moving maintenance management from paper drawings and handwritten notes to digital data enables decisions based on objective numbers and visualized information rather than individual intuition.

Efficiency and Labor Saving in Site Operations

Smartphone-based DX with LRTK has dramatic effects on site efficiency and labor saving. Surveying and as-built checks that used to require two to three people can now be completed by one person, and required time is greatly reduced. On sites that have introduced LRTK, reports include comments like “an as-built measurement that used to take half a day now finishes in tens of minutes” and “pile layout that required two people can now be done by one,” surprising many. Even with a shortage of experienced surveyors, anyone on site can perform accurate surveying, directly addressing labor shortage issues.

Because a dedicated app guides measurement procedures and automates data recording, tasks no longer rely on the intuition or experience of veterans and have become work anyone can do. Young or new staff can obtain high-precision results by simply following on-screen instructions, reducing the need for veteran oversight and mentoring. The cumbersome tasks of searching for survey points with paper drawings and notebooks or transcribing measured values are reduced, lowering the risk of human error. Since on-site data is shared to the cloud immediately, the time spent organizing and reporting after returning to the office is also reduced. Shortening the time from surveying to reporting streamlines the entire construction cycle, allowing freed time to be allocated to other tasks.

There are also significant safety benefits. The need to carry heavy equipment to heights is reduced, and hazardous cliff- or slope-side surveying can be performed remotely, lowering worker risk. Visualizing buried utilities with AR before construction can prevent accidental damage to existing pipes. Constant data connectivity between site and office reduces misunderstandings and lets all stakeholders work safely with the latest information. This is expected to reduce close calls and prevent accidents.

LRTK-based smartphone DX tools are also cost-effective to adopt, and a wide range of organizations are beginning to implement them. LRTK is available as a hardware monthly subscription service, lowering initial costs and appealing to small and medium-sized businesses. Visitors at the exhibition commented, “I didn’t realize a smartphone could be used this much,” and “this could be the trump card for on-site DX,” with reactions such as “I want every site staff to have one.” In local government work, there are examples where road and park surveys or boundary checks are performed by staff using LRTK, reducing outsourcing and rework from site confirmations. Some municipalities have started deploying LRTK as an initial disaster survey tool, and construction companies are increasingly adopting it as part of ICT construction. Registration in the Ministry of Land, Infrastructure, Transport and Tourism’s New Technology Information System (NETIS) lowers the barrier to use in public projects and provides tailwind for DX promotion.

Expanding LRTK Use through Simple Surveying

Beyond advanced 3D measurement and AR, LRTK is powerful for everyday simple surveying. For example, using an optional monopod (simple pole), you can obtain the precise coordinates of a ground point by simply aligning the pole tip with the point and pressing a button. The app automatically corrects for the pole length offset, so you don’t need to hold the smartphone right at ground level to achieve high-precision single-point positioning. Even in narrow sites or locations with elevation differences, one person can easily lay out points, so quick checks of current conditions or as-built can be performed whenever needed. This capability meets the “just want to measure a little” needs that previously required calling in specialized survey crews, greatly expanding the scope of on-site data use.

LRTK also offers continuous positioning log recording; a worker walking the site can continuously acquire longitudinal and cross-sectional ground elevation data, enabling rapid surveying of large area topography. From routine inspections to immediate post-disaster damage recording, LRTK enables accurate surveying on the spot, becoming a true “reliable companion” at the site.

Now that this can be achieved with just a smartphone, on-site DX from surveying and measurement to structural maintenance has steadily become a reality. LRTK, which garnered attention at CSPI, stands at the forefront as a solution that will strongly support productivity improvement and safety management on future construction sites. It is expected that smartphone-based DX solutions will continue to evolve at future CSPI-EXPO events and become industry standards. The era in which digital reform using familiar devices dramatically improves site productivity and safety is just around the corner.