Spotlight at CSPI: The New Era of Construction Management Opened by Smartphone High-Precision Positioning × AR

(Introduction) As DX (digital transformation) in the construction industry accelerates, a technology trend that has attracted significant attention at recent Construction and Survey Productivity Improvement Exhibitions (CSPI-EXPO) is emerging. It’s a new construction management solution that combines high-precision positioning technology (GNSS) with AR (augmented reality) on smartphones. Centimeter-level positioning using a smartphone and intuitive AR visualization are poised to overturn conventional practices and usher in a new era of construction management. This article clearly explains the innovations brought by this “smartphone × high-precision positioning × AR” approach, how it differs from traditional methods, on-site use cases, and its effects on productivity improvement.

Latest technology trends seen at CSPI-EXPO

CSPI-EXPO (Construction and Survey Productivity Improvement Exhibition) is one of Japan’s largest trade shows gathering the latest technologies and products for the civil engineering, construction, and surveying industries. Every year many companies and organizations participate, showcasing various “construction DX” related technologies such as ICT construction, i-Construction, IoT devices, drone surveying, and 3D scanners. Among these, the fusion of high-precision positioning using smartphones and AR technology has drawn particularly strong interest in recent years. Attempts to realize centimeter-level surveying—which traditionally required specialized equipment—on a smartphone and project that data onto the site via AR have garnered keen attention from industry stakeholders.

A small GNSS receiver attached to a smartphone can quickly turn an iPhone into a centimeter-class surveying instrument. *Photo shows an LRTK Phone attached.*

Smartphones transformed into high-precision surveying instruments — what RTK × AR enables

By combining a smartphone with a high-precision GNSS receiver and an AR app, many surveying and construction management tasks that were previously conducted with dedicated equipment can be handled with just one smartphone. The key is RTK (Real Time Kinematic) technology, which enhances smartphone positioning to centimeter-level accuracy in real time. Ordinary smartphone GPS has errors on the order of meters, but RTK-GNSS uses correction information from base stations to achieve planar accuracy of about 2–3 cm (and vertical accuracy of about 3–5 cm). Using this high-precision positioning on a smartphone enables the accurate overlay of data onto the real world, making intuitive AR-based construction management possible.

For example, when viewing a site through the smartphone camera, points and lines corresponding to positions on the design drawings can be virtually displayed in place. Tasks that previously required imagining locations from drawings and marking them are completed simply by “looking” at the smartphone screen. Because the GNSS receiver attached to the smartphone continuously acquires its precise coordinates, the AR display remains stable even while walking around. Traditional standalone AR functions tended to drift with extended movement, but reinforcing smartphone positioning with high-precision GNSS resolves this issue.

Furthermore, by leveraging a smartphone’s sensor suite, new surveying styles become possible. For instance, combining an iPhone’s LiDAR scanner or stereo camera capabilities allows measuring coordinates of points that are distant or out of reach simply by pointing the camera. Points on dangerous cliff faces or high locations that were previously difficult to approach can now be measured instantly from a safe position by aligning a virtual target with the camera view. The smartphone is literally transforming into a “universal surveying instrument.”

Differences from conventional total stations and GNSS equipment

So, how does this new method—smartphone × high-precision positioning × AR—differ from traditional surveying instruments? Below we summarize the advantages compared with representative total stations and conventional GNSS surveying instruments.

• Required personnel and work efficiency: Surveying with a total station typically required two or more people (an operator for the instrument + a person holding a prism). Each point measurement involved setting up tripods, sighting, and staff placement, and measuring multiple points could take a full day. In contrast, with a smartphone + RTK-GNSS, one person can conduct agile surveying. GNSS can measure points even where line of sight is poor (behind obstacles), so overall movement time is reduced and significant efficiency gains are expected. Fewer personnel roaming the site and the ability to measure many points in a short time are major advantages.

• Ease of operation and accuracy assurance: Traditional surveying instruments require specialized skills, and reading and recording survey points often rely on experienced personnel. Manual reading or recording errors can lead to construction mistakes. Smartphone-based surveying, however, offers intuitive app operation that anyone can handle, with automatic data logging. Simply look at the point on the smartphone screen and press a button to save coordinates; previously measured points are shown with AR markers so you can immediately see “which points have been measured.” This enables accuracy-controlled surveying without advanced expertise, reducing human error on site.

• Real-time as-built verification: Previously, verifying whether measured points matched the design often required taking data back to the office for comparison with drawings or CAD. If discrepancies were found, crews had to return to the site for adjustments, causing inefficiency. With smartphone × AR, design data and measured data can be overlaid and checked on the spot, allowing immediate assessment of as-built conditions. This reduces repeated comparisons and back-and-forth between field and office, speeding up quality management cycles.

• Equipment cost and adoption barriers: High-precision total stations, GNSS receivers, and 3D laser scanners can cost several million yen per unit, making it difficult for small and medium-sized companies to equip multiple sets. In contrast, a smartphone + small GNSS receiver can be introduced with a relatively low initial investment. Recently introduced smartphone-mount RTK receivers have become more affordable, and it is becoming feasible to equip each field technician with one at a lower cost than traditional instruments. Reducing the need to rent expensive equipment or maintain large surveying teams lowers overall operating costs.

Of course, optical instruments remain advantageous for millimeter-level precision tasks (such as precise reference point surveys or structural displacement monitoring). However, for general civil engineering construction and terrain surveys, smartphone + RTK accuracy is increasingly sufficient. Proper selection of tools is important, but smartphone surveying is clearly emerging as a practical approach that combines adequate accuracy with substantial efficiency gains for many field surveying tasks.

On-site use cases expanding for smartphone positioning × AR

So, what can high-precision smartphone positioning and AR actually do on site? Here are several major use cases enabled by the latest solutions.

• Rapid single-person layout and stake driving: For setting reference lines and marking pile-driving positions, survey crews traditionally placed wooden stakes or chalk marks based on drawings. Using RTK × AR, simply point the smartphone at the design location and virtually display a stake or marker in AR at that spot. Even on rock surfaces or steep slopes where physical stakes can’t be driven, a virtual stake on the screen serves as an accurate reference. Multiple stake positions are indicated by AR markers as you move, enabling one person to efficiently direct stake placement.

• Overlaying 3D design models in AR: On sites using 3D design data like BIM/CIM, the planned 3D model can be overlaid on live site imagery via AR and shared with stakeholders on the spot. Displaying the expected completed shape of road embankments or structures at the actual construction location helps not only field staff but also equipment operators, craftsmen, clients, and nearby residents intuitively understand the final image. AR-based “visualization of the site” reduces communication losses from planning meetings to as-built inspections and helps prevent rework due to misaligned expectations.

• As-built management and quality inspections: Smartphone AR is powerful for as-built management and quality checks during and after construction. For example, to verify whether a dam or embankment has reached the specified height or slope, overlay the design cross-section lines on the terrain in AR to instantly see areas of excess or deficiency. Comparing point cloud data measured by smartphone with the design model on site enables immediate volume difference calculations for residual soil and other advanced inspections. AR display of inspection checkpoints helps ensure thorough and efficient checks. For repeat photography at fixed observation points, the smartphone can record previous shooting positions and angles and guide framing via AR, allowing anyone to retake photos with the same composition and improving the precision of long-term comparisons.

• Point cloud scanning and earthwork volume calculation: Using an iPhone with LiDAR, you can easily scan the site’s 3D point cloud. While aligning scans has been difficult with ordinary smartphone scanning, high-precision GNSS allows accurate coordinates to be assigned to every acquired point, turning scan results into georeferenced 3D survey data. By measuring point clouds before and after excavation and comparing them, earthwork volumes can be computed instantly, enabling speedy quantity management. Even for large-area embankment volume measurements, walking along AR-guided paths and scanning completes the job quickly.

High-precision positioning tags are added to 3D point clouds obtained by smartphone, enabling direct use as as-built models.

• Disaster response and remote sharing: In major disaster sites, smartphone surveying supports rapid situational assessment and information sharing. Where heavy machinery cannot enter, workers can capture coordinates and photos with a smartphone and upload them to the cloud, allowing remote office engineers to receive data in real time for mapping and analysis. In Japan, some local governments have introduced iPhone + high-precision GNSS devices for landslide recovery operations, digitally recording conditions without bringing large equipment into affected areas. Systems that can augment positioning via satellite communications allow surveying even when communication infrastructure is disrupted, increasing the potential of smartphone surveying as an initial response tool in disasters.

The labor-saving effects unlocked by cloud integration and single-person operations

One of the greatest benefits smartphone surveying and AR bring to the field is labor-saving and efficiency improvement. The Ministry of Land, Infrastructure, Transport and Tourism’s i-Construction initiative also emphasizes “efficient surveying with fewer personnel and shorter time,” and subsidy programs exist to support RTK-GNSS equipment adoption. Smartphone + high-precision positioning is precisely the technology that addresses this labor-saving need.

On the manpower side, as noted above, surveys and inspections can be completed by a single person, leading to significant reductions in labor costs and relief for labor shortages. Even with a shortage of experienced surveyors, simple smartphone operations allow younger staff to take measurements, easing veteran workloads and aiding skill succession. User-friendly tools can raise the baseline capability across the organization.

Real-time cloud integration is another major strength. Positioning data and photos acquired on a smartphone can be uploaded to the cloud on site, enabling immediate information sharing between field and office. This seamless connection reduces the time lag inherent in divided work processes and speeds up responses. With the latest field information accessible to all stakeholders, decision-making accelerates and errors are detected and corrected sooner.

From a cost perspective, it also enables rational investment to obtain sufficient accuracy. For ordinary surveying that does not require millimeter precision, using smartphone surveying instead of expensive instruments reduces equipment costs. If tasks that once required total station-class equipment can now be handled with a smartphone, on-site equipment composition can be reconsidered. Appropriate technology allocation improves overall cost performance.

Furthermore, safety improvements should not be overlooked. The ability for single-person operation means no need to send guides into hazardous areas. Risks associated with multiple people working on unstable slopes or beside roadways can be reduced, and non-contact measurements (targeting with a camera) enable measurement of hazardous locations from a distant, safe position. Labor-saving thus contributes to enhanced safety management and helps achieve “zero incidents, zero accidents” on site.

A new era begins with simplified surveying via LRTK

A concrete solution realizing the potential of smartphone × high-precision positioning × AR is the recently introduced LRTK system. LRTK is a high-precision GNSS positioning solution for iPhone/iPad provided by Lefixea, a venture originating from Tokyo Institute of Technology, which turns smartphones into “pocket-sized surveying instruments.”

The dedicated LRTK receiver “LRTK Phone” is a compact unit weighing about 165 g and about 13 mm thick, with an antenna and battery built in, and can be attached to an iPhone with one touch. It connects to the smartphone via Bluetooth or Lightning and supports network RTK and CLAS augmentation from Japan’s Quasi-Zenith Satellite System (Michibiki), enabling real-time centimeter-level positioning anywhere in Japan. It is dust- and water-resistant for field use, offers about six hours of battery life (with external power support for extended work), and is truly a practical device designed for field use.

The provided iOS app “LRTK App” is an all-in-one tool that supports tasks from acquiring and recording positioning data to AR-guided stake driving, point cloud scanning, and photo measurement. Measured coordinates are automatically converted to the plane rectangular coordinate system and elevations (geoid height) and plotted on maps; captured photos are tagged with high-precision position and orientation information and can be shared to the cloud immediately. For any recorded point, AR guidance on the map or camera screen indicates direction and distance to the destination, so measuring, recording, and verifying on site can be completed within a single app.

An AR model based on design data (red areas) is overlaid on the smartphone screen so as-built conditions can be checked and shared on the spot.

LRTK also integrates cloud services, so all data acquired on site is stored and shared in the cloud. From the office, uploaded data can be viewed, checked, and downloaded on a browser, facilitating smooth remote information sharing. For example, point clouds or photos obtained in the field can be shared in real time within or outside the company for immediate discussion and decision-making.

Because LRTK allows surveying and information sharing on site with just a smartphone, it has already been adopted in civil engineering construction and infrastructure inspection. There are voices saying “the era of one smartphone surveying instrument per person has arrived,” and its practicality—compatible with the Ministry of Land, Infrastructure, Transport and Tourism’s 3D as-built management guidelines—has been highly evaluated. Low-cost, high-precision surveying that was once unimaginable makes it easier for small and medium-sized companies to proceed with DX. It is truly a next-generation tool that will dramatically boost field productivity and creativity.

If you are interested, please also check the [LRTK official site](https://www.lrtk.lefixea.com/). Product specifications, implementation examples, demo videos, and more are available, helping you grasp concrete use cases for simplified surveying. Why not make a smartphone your ally and step into a new era of construction management? Field surveying and as-built management will evolve to become smarter, safer, and more efficient.