Overview of RTK × AR Technology

First, let's briefly review RTK positioning technology. While conventional GPS or GNSS positioning typically provides accuracy of several meters, RTK positioning can achieve centimeter-level accuracy, reducing positional errors to just a few centimeters. RTK works by correcting positioning errors in real-time between a base station (fixed reference point) and a rover (mobile unit), allowing highly accurate coordinates to be obtained instantly. This centimeter-level accuracy is essential for effectively implementing AR on construction sites. If accuracy were off by even a few meters, the virtual design models could not be accurately overlaid onto their real-world positions, greatly diminishing the reliability of AR-based verification.

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How, then, do we combine high-precision positioning with AR? One method involves integrating RTK-enabled GNSS receivers into AR glasses (smart glasses) or tablet devices, allowing site workers to view design data superimposed directly onto the real environment. For instance, solutions are emerging that equip AR glasses like Microsoft's HoloLens with dual-antenna RTK-GNSS, enabling workers to view design information hands-free while performing tasks. Additionally, specialized helmet-integrated AR devices are under development, and in the future, workers wearing smart glasses may become a common sight at construction sites. By utilizing precise positional and orientation data obtained from RTK within AR devices, digital information can be accurately aligned and displayed within the real-world space. This integration is particularly effective when combined with 3D design data represented by BIM/CIM. Traditionally cumbersome on-site model alignment tasks become unnecessary, as the design models can be directly projected via AR into their exact intended coordinates. RTK × AR technology effectively brings drawings and 3D models directly into the real-world environment of construction sites.

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Practical Examples of RTK × AR in the Construction Industry

In the construction industry, various initiatives leveraging RTK and AR for digital transformation (DX) in construction management are already underway. Below are several notable use cases:

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On-site confirmation of construction plans using a tablet-based RTK receiver and AR application. High-precision RTK positioning allows accurate overlay of digital design data onto their correct real-world positions.

• Overlaying Design Drawings and Models onto Construction Sites: Displaying drawings or 3D models as AR overlays onto the actual site scenery helps stakeholders reach intuitive agreements and prevents mistakes. For example, Shimizu Corporation developed an "Underground Infrastructure Visualization System," which uses position data obtained via GNSS receivers to retrieve buried utility drawings from the cloud and superimpose them onto tablet camera views. This clearly reveals the locations of underground pipes and cables, reducing the risk of accidental damage during excavation work. Additionally, in bridge and building construction, projecting the planned structural models onto real-world sites enables verification of spatial relationships and aesthetics before actual construction. AR visualization provides intuitive understanding of the final outcome, which is difficult to achieve through drawings alone, making explanations to clients or local residents smoother. Such visual clarity improves the efficiency and effectiveness of stakeholder meetings and consultations.

• Improving Construction Accuracy (Rebar Placement, Foundation Work, etc.): AR technology also excels as a construction accuracy management tool. For instance, Obayashi Corporation developed a system integrating BIM models, point-cloud measurements, and AR to automatically verify rebar installation. Utilizing data captured from helmet-mounted cameras, the system swiftly confirms whether rebars are arranged according to the intended number, spacing, and diameter, significantly reducing inspection workloads and enhancing quality. AR also proves valuable in foundation work and marking operations. Traditionally, surveyors needed to physically mark pile-driving positions or place markers on the ground. However, RTK-compatible AR applications can virtually display pile locations (AR piles) or reference lines on-site, streamlining these tasks. For example, on steep slopes or hard ground where physical pile placement is challenging, virtual piles can precisely indicate required positions within AR space. Workers can accurately verify locations through tablets or smartphones while positioning rebars and formwork, greatly minimizing human error and improving overall precision.

• Streamlining Infrastructure Inspection and Maintenance: The integration of RTK and AR introduces a fresh approach to infrastructure maintenance. For example, during routine inspections of tunnels or embankments, previous inspection photos' positions and angles can be precisely recorded. At the next inspection, AR arrows guide users via smartphone screens to replicate the exact camera positioning, allowing consistent conditions for monitoring long-term changes, such as crack progression. Moreover, inspectors can place virtual markers at detected deterioration points and later use AR during repairs to accurately identify these locations. Remote assistance is also becoming increasingly practical, with on-site AR imagery shared via the cloud, enabling distant experts to annotate and give instructions directly on live site views. In essence, RTK-AR technology promises substantial efficiency gains in infrastructure inspection and maintenance by reducing oversights and enhancing information-sharing accuracy.

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Benefits of RTK × AR Construction Management using LRTK

As explained above, RTK×AR technology offers numerous advantages; however, practical concerns such as "Aren't high-precision devices difficult to operate?" or "Isn't expensive specialized surveying equipment required?" might arise. These concerns are addressed by Lefixea's LRTK series. LRTK is a compact RTK-GNSS receiver solution integrated with smart devices and cloud services, designed specifically to allow anyone on-site to easily achieve centimeter-level positioning and utilize AR technology. Below, we introduce three key benefits provided by adopting the LRTK solution.

① Easy Introduction of High-Precision Positioning:
With the LRTK series, you can easily set up an RTK positioning environment without needing specialized surveying equipment. For example, the LRTK Phone is a compact device that attaches directly to the back of your iPhone or iPad with a simple click. Just by attaching it to a smartphone, you can achieve centimeter-level positioning accuracy utilizing QZSS (Michibiki) augmentation signals or network-based RTK—no complex setups or cable connections required.

Traditionally, precise positioning required expensive, stationary GNSS receivers or surveying equipment, but now it can be done simply with "one smartphone per person + an LRTK device." This approach allows everyone from site supervisors to craftsmen to access highly accurate location data from their own devices, accelerating the widespread adoption of precision positioning.

Moreover, the LRTK series offers multiple product types, not only the smartphone-compatible "Phone" model but also construction helmet-mounted and stationary "Pro" models. This flexibility to choose according to application further lowers the barriers to implementing RTK at construction sites.

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② Intuitive Operation Through Smart Device Integration:
LRTK seamlessly integrates with dedicated apps running on smartphones and tablets, allowing intuitive operation on familiar devices. Simply launch the app, and it automatically connects to the GNSS receiver, displaying your current position at centimeter-level accuracy. From there, you can easily record measurement points by tapping the screen or select and visualize design models in AR without complicated training. This smartphone-like ease of use greatly simplifies surveying and construction management tasks.

Additionally, with LRTK, all acquired data (point coordinates, photos, point clouds, etc.) is instantly synchronized to the cloud. For instance, photos captured onsite automatically include metadata such as precise coordinates and the direction in which they were taken, enabling office-based staff to immediately identify photo locations and orientations on a digital map. The combination of intuitive smart-device operation and rapid cloud-based information sharing makes LRTK remarkably user-friendly and efficient.

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③ Real-Time Information Management through Cloud Integration:
The LRTK system integrates closely with cloud services, designed specifically to facilitate real-time data sharing between construction sites, offices, and all related stakeholders. Measurement data and point clouds recorded through the LRTK app are automatically uploaded to the LRTK Cloud and synchronized instantly across devices via the internet.

For example, if onsite personnel scan a construction area and generate a point-cloud model, this data can be uploaded immediately to the cloud, allowing office-based staff to promptly review, perform volume calculations, or make drawing adjustments. Conversely, if design staff prepare BIM/CIM models and upload them to the cloud, onsite workers can download the latest models directly onto their devices for immediate AR visualization.

This cloud-based centralized information management ensures synchronization of the most up-to-date data between site and office, significantly accelerating decision-making and reducing the potential for rework. Moreover, the LRTK Cloud also incorporates robust access control and version history management, allowing real-time monitoring of construction and survey activities while minimizing risks related to data tampering or loss. Ultimately, this leads to substantial improvements in overall construction management efficiency and quality.

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In addition, AR visualization using LRTK has been confirmed to provide stable, high-accuracy positioning by continuously correcting the user's location in real-time. This ensures that AR models remain accurately aligned even when workers move around the site. Unlike traditional AR systems where virtual objects often drift or misalign as users walk, the LRTK system greatly reduces this issue, enhancing user confidence and practicality on-site. Thus, leveraging LRTK enables the full benefits of RTK×AR construction management while facilitating smooth adoption and integration into daily operations.

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The Future of Construction Management and the Potential of RTK×AR

Construction management utilizing RTK×AR is expected to evolve significantly in the future. Particularly, by integrating advanced communication and robotic technologies, entirely new styles of construction management may emerge.

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The first possibility is real-time construction management through integration with high-speed communications such as 5G. Although remote supervision and remote support between construction sites and offices via cloud services have already begun, the widespread adoption of 5G networks will soon enable seamless, latency-free sharing of large-volume 3D models and high-definition AR visuals. Specifically, this technology will allow real-time distribution of AR imagery viewed by on-site workers to multiple locations simultaneously, facilitating instant expert feedback through "real-time collaborative work." Additionally, process data from ongoing construction (such as machinery IoT data and sensor measurements) could be visualized directly via AR, enabling immediate on-site decision-making. The advancement toward high-speed, low-latency communications will strongly support such real-time construction management, creating innovative operational structures that transcend geographical limitations.
 

The second is the "integration with autonomous construction robots." In recent years, automated control of construction machinery and the use of on-site robots have advanced significantly, and RTK×AR can create powerful synergies with these technologies. For example, autonomous construction machinery or rebar-placement robots equipped with RTK receivers could perform tasks based on high-precision positional data, while site managers visualize robot movements through AR. Drone surveying also benefits from RTK-enhanced accuracy, enabling immediate AR visualization of point-cloud models to verify construction results directly on-site. In the future, it could become feasible to achieve a near-real-time cycle of robots conducting construction work, humans verifying it through AR, and then providing immediate feedback to robots for adjustments. Amid intensifying labor shortages, initiatives combining robots, RTK, and AR are likely to dramatically boost productivity.

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The third is "Application to Smart Cities." As high-precision positioning infrastructure is developed throughout entire cities and digital twins (virtual urban models) are constructed, RTK×AR technology is expected to find broad applications beyond the construction field. For example, in road and pipe construction, workers can safely and efficiently perform excavation while using AR glasses to view maps of underground utilities and pipe routes in real-time. City offices or administrators can simply update infrastructure GIS data on the cloud, instantly reflecting changes in the AR displays at work sites, thus preventing accidents caused by distribution errors or referencing outdated maps. Additionally, in urban planning, it will become feasible to overlay city-block and building models onto real-world sites using AR to evaluate aspects such as scenery and shading, or to aid in community consultations. In the future, anyone in the city might carry centimeter-level positioning devices (such as smartphones or smart glasses), enabling them to instantly access urban information through AR whenever necessary. Indeed, the day when RTK×AR serves as the core informational infrastructure supporting city life and urban development in smart cities may not be far away.

Thus, RTK×AR construction management is currently evolving and has the potential to become "standard practice" in the future. As the adoption of 5G networks and robotics technologies progresses, the pace of implementation will likely accelerate even further. This technology extends beyond the boundaries of the construction industry, influencing entire urban environments and society as a whole, making it an area worth watching closely in the coming years.