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 technological trend has been attracting significant attention at recent Construction and Survey Productivity Improvement Exhibitions (CSPI-EXPO). That trend is a new construction management solution that combines high-precision positioning technology (GNSS) and AR (augmented reality) on smartphones. Centimeter-level positioning using a smartphone and intuitive AR displays are opening a new era of construction management that overturns conventional wisdom. This article clearly explains the innovations brought by “smartphone × high-precision positioning × AR,” 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 the largest domestic trade shows where the latest technologies and products for civil engineering, construction, and surveying come together. Many companies and organizations participate each year, showcasing various “construction DX” related technologies such as ICT construction, i-Construction, IoT devices, drone surveying, and 3D scanners. Among these, what has been gaining particularly high attention in recent years is the fusion of high-precision positioning using smartphones and AR technology. The attempt to achieve centimeter-level surveying that previously required specialized equipment with a smartphone, and to project that data onto the site via AR, has drawn strong interest from industry stakeholders.

A small GNSS receiver attached to a smartphone can quickly turn an iPhone into a surveying instrument capable of centimeter-level positioning. *The photo shows an LRTK Phone attached.*

Smartphones Transforming into High-Precision Surveying Instruments – What RTK × AR Makes Possible

By combining a smartphone, a high-precision GNSS receiver, and an AR app, many surveying and construction management tasks that previously required dedicated equipment can be handled with just one smartphone. The key is RTK (Real Time Kinematic) technology, which enhances a smartphone’s position in real time to centimeter-level accuracy (cm level accuracy (half-inch accuracy)). Ordinary smartphone GPS has errors on the order of several meters, but RTK-GNSS uses correction information from base stations to achieve an accuracy of about 2-3 cm (0.8-1.2 in) in horizontal position (and about 3-5 cm (1.2-2.0 in) in height). Using this high-precision positioning on the smartphone enables the accurate overlay of data onto real space, realizing intuitive construction management via AR.

For example, when looking at a site through a smartphone camera, you can virtually display points or lines corresponding to positions on the design drawings in the real location. Tasks that used to require mentally mapping drawing positions and marking them can now be completed simply by “looking” at the smartphone screen. Because the GNSS receiver attached to the smartphone is continuously capturing its precise coordinates, the AR display remains stable even while walking around. Standalone AR functionality previously suffered from drift during prolonged movement, but reinforcing smartphone positioning with high-precision GNSS resolves this issue.

Furthermore, by leveraging the smartphone’s suite of sensors, new surveying styles become possible. For example, by combining iPhone LiDAR scanners or stereo camera functions, you can measure coordinates of points that are out of reach simply by pointing the camera. Points on a dangerous cliff face or high locations that were previously difficult because people could not approach them can now be measured instantly by aiming the smartphone from a safe position and aligning a virtual target. The smartphone is truly transforming into an “all-purpose surveying instrument.”

Differences from Traditional Total Stations and GNSS Equipment

So what distinguishes this new method—smartphone × high-precision positioning × AR—from conventional surveying instruments? Here we summarize the advantages in comparison with typical total stations and traditional GNSS surveying instruments.

• Required personnel and work efficiency: Surveying with a total station normally required two or more people (an operator of the surveying instrument plus a person holding a prism). Each point measurement involved setting up a tripod, sighting, and staff positioning, and surveying multiple points could take an entire day. In contrast, with a smartphone + RTK-GNSS, one person can perform agile surveying. GNSS can measure points even in locations with poor line-of-sight (behind obstacles), so significant efficiency gains are expected including reduced travel time. The ability to measure many points quickly with fewer personnel is a major benefit.

• Ease of operation and ensuring accuracy: Traditional surveying instruments require specialized skills, and reading and recording survey points often relied on the experience of skilled personnel. Human reading errors or recording mistakes can lead to construction errors. Surveying using a smartphone, however, offers intuitive app operation that anyone can handle, with automatic data recording. By simply looking at the smartphone screen at the point to be measured and pressing a button, coordinates are saved automatically; previously measured points are displayed as AR markers so it is immediately clear “which points have been measured.” This allows accuracy-controlled surveying without advanced expertise and reduces human error on site.

• Real-time as-built verification: Previously, confirming whether measured points on site matched the design often required bringing data back to the office and checking on drawings or CAD. If discrepancies were found, teams had to return to the site to rework—an inefficient cycle. With smartphone × AR, you can overlay design data and measured data on the spot to instantly judge whether the as-built shape is acceptable. This reduces back-and-forth between drawings and the office, speeding up the quality management cycle.

• Equipment cost and adoption hurdles: High-precision total stations, GNSS receivers, and 3D laser scanners are expensive (often several million yen per unit), making it difficult for small and medium-sized enterprises to equip multiple units. In contrast, smartphone + small GNSS receiver solutions can be introduced with a relatively low initial investment. Recently released smartphone-mounted RTK receivers have become more affordable, and in some cases handing one to each field technician can be cheaper than traditional equipment. Reducing the need to rent expensive equipment or maintain large surveying teams helps lower overall operating costs.

Of course, traditional optical instruments remain advantageous where millimeter-level precision is required (such as precise control point surveys or displacement monitoring of structures). However, for typical civil construction and terrain measurement, smartphone + RTK accuracy is increasingly sufficient. Properly choosing tools for each task is important, but smartphone surveying has emerged as a method that combines practical accuracy with significant efficiency gains in many field surveying situations.

On-Site Use Cases for Smartphone Positioning × AR

What specific things can be done on-site using smartphone high-precision positioning and AR? Below are several major use cases enabled by the latest solutions.

• Rapid batter board and pile-driving work by one person: For marking baseline lines for structures or pile-driving locations, survey teams used to install batter boards or marks on site based on drawings using wooden stakes or chalk. With RTK × AR, simply pointing the smartphone at the design pile location will display a virtual stake or marker in AR at that point. Even on rock surfaces or steep slopes where physically driving a stake is impossible, the virtual stake on the screen can serve as an accurate reference. Multiple pile locations are shown as AR markers as you move, enabling efficient one-person guidance for pile-driving locations.

• Overlaying 3D design models in AR: On sites using 3D design data such as BIM/CIM, the planned 3D model can be overlaid onto live site footage in AR so stakeholders can share the as-built image on the spot. For example, projecting the final embankment shape or structure onto the actual construction area allows not only the site supervisor but also heavy equipment operators, craftsmen, clients, and nearby residents to intuitively understand the finished appearance. AR visualization of the site reduces communication losses from planning meetings through as-built inspections and helps prevent rework due to misunderstandings.

• Applications for as-built management and quality inspection: Smartphone AR is powerful for as-built management (progress and quality confirmation) during and after construction. For instance, when checking whether a dam or development site has reached the specified elevation and slope, overlaying the design cross-section lines in AR on the terrain makes it easy to see excesses or deficits in cut-and-fill at a glance. Comparing point cloud data measured with a smartphone to the design model on site allows immediate computation of volume differences for remaining earthwork. Displaying inspection checkpoints in AR helps conduct inspections efficiently without omissions. For repeat photography at fixed points, the smartphone can record the previous shooting position and angle and provide AR guidance, enabling anyone to retake photos with the same framing and improving the accuracy of temporal change comparisons.

• Point cloud scanning and earthwork volume calculation: Using an iPhone equipped with LiDAR, it is also possible to easily capture 3D point clouds of the site. Conventionally, aligning such scans was challenging, but by using high-precision GNSS to assign accurate coordinates to all captured point cloud data, the scan results become 3D survey data placed directly into a map coordinate system. For example, by measuring point clouds before and after excavation and comparing them, you can instantly calculate hauled soil volumes and perform rapid as-built quantity management. For measuring embankment volumes over wide areas, simply walking and scanning along guides displayed in AR on site allows completion in a short time.

High-precision positioning coordinates are attached to 3D point clouds acquired by a smartphone, enabling immediate use as as-built models.

• Disaster response and remote sharing: Smartphone surveying is also useful for rapid situation assessment and information sharing at large-scale disaster sites. Where heavy machinery cannot enter, workers can use a smartphone to sequentially obtain coordinates and photos and upload them to the cloud, allowing remote office engineers to receive and convert the data to drawings and analyses in real time. In Japan, some municipalities have introduced iPhone + high-precision GNSS devices for landslide recovery tasks, digitally recording conditions without bringing large equipment into the disaster area to aid decision-making. Systems that can augment positioning via satellite communications enable surveying even when communication infrastructure is disrupted, making smartphone surveying an attractive initial investigation tool in disasters.

Labor Reduction Effects Enabled by Cloud Integration and Single-Person Tasks

One of the biggest benefits that smartphone surveying and AR bring to sites is labor reduction and efficiency. Under i-Construction promoted by the Ministry of Land, Infrastructure, Transport and Tourism, “efficient surveying with fewer people and shorter time” is a key theme, and subsidies exist to support the introduction of RTK-GNSS equipment. Smartphone + high-precision positioning methods directly address this need for labor-saving.

First, in terms of manpower, as mentioned earlier, surveying and inspection tasks can be completed by one person, leading to significant savings in labor costs and mitigation of workforce shortages. With fewer experienced surveyors available, easy smartphone operation allows younger staff to perform measurements, reducing the burden on veterans and aiding skill transfer. User-friendly tools can raise the overall capability of an organization.

Another major advantage is real-time cloud integration. Positioning data and photos captured on a smartphone can be uploaded to the cloud on the spot, enabling instant information sharing between the field and the office. This connects previously segmented processes with time lags into a seamless workflow and speeds up responses. Everyone can immediately access the latest site information, accelerating decision-making and enabling early detection and correction of errors.

Cost-wise, it becomes possible to make rational investments to obtain sufficient accuracy. For general surveying where millimeter precision is unnecessary, using smartphone surveying instead of expensive equipment reduces equipment costs. If more tasks that used to require total-station-class equipment can now be handled with smartphones, site equipment configurations can be reconsidered. Appropriately selecting technologies by task improves overall cost performance.

Additionally, safety improvements should not be overlooked. The ability to perform single-person work means there is no need to send people into hazardous areas as guides. This reduces the risks associated with multiple people working on unstable slopes or alongside roadways, and non-contact positioning (measuring targets by aiming a camera) enables measurement of hazardous areas from a safe, distant location. Labor reduction thus contributes to enhanced safety management and helps achieve “zero accidents and zero disasters” on site.

A New Era Starting with Simple Surveying via LRTK

A concrete solution that realizes the potential of smartphone × high-precision positioning × AR is the recently introduced LRTK system. LRTK (pronounced L-R-T-K) is a high-precision GNSS positioning solution for iPhone/iPad provided by Lefixea, a venture originating from the Tokyo Institute of Technology, and it literally turns a smartphone into a “pocket-sized surveying instrument.”

The dedicated LRTK receiver “LRTK Phone” is a compact unit with an antenna and battery built into a housing weighing approximately 165 g and about 13 mm (0.51 in) thick, and it can be attached to an iPhone with a single click. It connects to the smartphone via Bluetooth or Lightning and supports network RTK and CLAS augmentation from Japan’s quasi-zenith satellite Michibiki, enabling centimeter-level positioning in real time anywhere in Japan. With dustproof and waterproof specifications suitable for field use and about 6 hours of battery operation (external power support allows longer work), it is truly a practical device designed for on-site use.

The provided iOS app “LRTK App” offers an all-in-one toolset for tasks, from acquiring and recording positioning data to AR-guided pile-driving navigation, point cloud scanning, and photo-based measurement. Measured coordinates are automatically converted to the plane rectangular coordinate system and elevation (geoid height) and plotted on a map; photos taken are tagged with high-precision position and orientation information and can be shared to the cloud immediately. For any recorded point, an AR guidance function on the map or camera screen indicates the direction and distance to the target, enabling measuring, recording, and verifying on site to be completed in a single app.

The 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, storing and sharing all data captured on site in the cloud. From the office, uploaded data can be viewed and downloaded on a map in a browser, making remote information sharing smooth. For example, point clouds and photos captured on site can be shared internally and externally in real time for immediate consultation and decision-making.

Because surveying and information sharing on site can be completed with just a smartphone, LRTK has already been adopted in civil construction and infrastructure inspection sites. There are voices saying “the era of one smartphone surveying device 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. The ability to perform high-precision surveying at a previously unthinkable low cost is making DX more accessible to small and medium-sized enterprises. It is truly a next-generation tool that can dramatically boost on-site productivity and creativity.

If you are interested, please check the [LRTK official site](https://www.lrtk.lefixea.com/). Product specifications, case studies, and demo videos are available, giving a concrete image of simple surveying applications. Why not take a step into the new era of construction management by making a smartphone your ally? On-site surveying and as-built management will evolve to become smarter, safer, and more efficient.