The Future of Surveying:
RTK × AR Transforms Your Smartphone into a High-Precision GPS Surveying Tool

In recent years, the surveying industry has seen the introduction of digital technologies such as drone surveying and 3D scanners, accelerating innovations referred to as "Construction DX." In this context, a new surveying style combining RTK (Real-Time Kinematic) and AR (Augmented Reality) using smartphones is gaining attention. By simply attaching a compact RTK-GPS receiver to a smartphone, it becomes possible to achieve centimeter-level high-precision positioning, making surveying tasks that previously required specialized equipment accessible to anyone.

Thanks to AR technology, surveying data and design drawings can be overlaid onto the real-world scene, enabling intuitive operations and significantly contributing to increased productivity on-site. In this article, we will explain the mechanism and benefits of this next-generation surveying method, combining RTK and AR, and explore how the latest technologies can improve business operations.

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What is RTK × AR?

RTK (Real-Time Kinematic) is a technology that uses satellite positioning systems (GNSS) to perform high-precision positioning in real-time. Specifically, it involves using two GNSS receivers: a reference station with known coordinates and a moving station that performs positioning while moving. The error information obtained from the reference station is transmitted in real-time to the moving station for correction, allowing positioning accuracy to be achieved within a few centimeters. While standalone GPS positioning typically results in errors of several meters, RTK positioning can achieve accuracy of approximately 2-3 cm horizontally and 3-4 cm vertically.

On the other hand, AR (Augmented Reality) technology overlays computer-generated information onto the real-world scene viewed through a camera. In the field of surveying, AR (AR surveying) integrates digital data such as design drawings and survey points into the actual landscape, allowing users to intuitively understand the information on-site.

By combining RTK and AR, a smartphone transforms into a "high-precision GPS surveying tool." By attaching a miniaturized RTK-GNSS receiver to the smartphone, the phone can determine its position with centimeter-level accuracy, and using that high-precision location data, AR visualizes the surveying data in space. For example, it can pinpoint and display the alignment or location of structures on the ground or on structures themselves, as shown in the design drawings, or visually mark the measured points as virtual markings on-site. This allows users to instantly overlay and verify positioning and drawing information on-site, enabling real-time data visualization. Previously, it was necessary to reconcile the drawings with the site in the office after surveying or compare paper drawings with the actual site, but with RTK × AR, the process of "seeing, measuring, and verifying" can be completed immediately on-site.

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Benefits of Implementing RTK × AR Technology

The biggest benefit of implementing RTK × AR is that it enables efficient surveying by a single person. Traditionally, optical surveying with total stations required two people for observations and target setup, but with RTK-GNSS, one worker with the receiver can complete the survey. Additionally, RTK surveying allows for measurements through obstacles, enabling fast and accurate positioning even in sites with poor visibility, which reduces surveying time and increases efficiency.

Moreover, AR technology digitizes many manual processes, reducing the need for carrying paper drawings and re-adjusting benchmarks multiple times. As a result, work time is significantly shortened, directly improving productivity. In fact, RTK-GNSS surveying devices are eligible for the national subsidy program (for labor-saving investments), and benefits such as “efficient surveying in a short time” and “improved productivity by performing tasks alone” are expected.

The ease of use is another notable advantage, as even non-specialized users can operate the technology. The smartphone app provides an intuitive interface, so even individuals with limited surveying knowledge can follow guides to measure points and align positions using AR. For example, simply holding up the smartphone and pressing a button allows you to obtain coordinates, and previously measured points are displayed as markers on the screen for easy verification. The LRTK system, designed as a "one device per person" tool, aims to be easily carried in a pocket, allowing workers to quickly use it whenever needed.

This ease of use also reduces the burden on experienced technicians and helps delegate authority to younger staff, providing benefits in terms of addressing labor shortages and transferring skills.

The cost reduction effect is also significant. RTK × AR surveying helps reduce the expensive equipment and labor costs that were traditionally required. Total stations and high-performance GNSS receivers could cost hundreds of thousands of yen, but with the smartphone and compact RTK receiver approach, a relatively low investment is sufficient.

In practice, smartphone-mounted RTK receivers provided by startups are designed to be ultra-compact and cost-effective, aiming for a price that “everyone can afford,” and in many cases, it is more affordable than traditional equipment even when deployed with one device per person. Additionally, by shortening the time spent on non-surveying tasks, labor costs and days required for the project can be reduced, lowering overall operational costs. It’s been pointed out that by selecting the appropriate method based on the required accuracy, unnecessary costs can be avoided. For instance, in cases where millimeter-level accuracy is not needed, the cost can be reduced while maintaining centimeter-level precision through satellite positioning. In this way, RTK × AR technology presents an attractive solution for small to medium-sized civil surveying companies due to its high efficiency with minimal investment.

RTK × AR surveying offers centimeter-level precision, equivalent to traditional GNSS surveying, while excelling in mobility and convenience. In situations requiring ultra-high precision, such as precise benchmark surveying or displacement measurement, optical surveying is still necessary, but for general civil construction and land surveying, RTK × AR provides sufficient accuracy. Furthermore, by utilizing network-based RTK-GNSS, surveying can be conducted without the need for dedicated base stations. As long as the smartphone has connectivity, surveying can begin instantly anywhere in Japan. For devices that support CLAS (Centimeter-level Augmentation Service) from Japan’s quasi-zenith satellite system, Michibiki, high-precision positioning is possible even in areas without mobile signal coverage, such as mountainous regions, further expanding the operational range. Overall, RTK × AR surveying is a flexible method that allows for surveying "whenever needed, wherever needed, by anyone instantly."

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Use Cases of RTK × AR Technology

Use Case in Construction Sites: RTK × AR technology is being utilized in a variety of ways in construction management and surveying. For example, in the past, layout marking (marking the position of structures on-site) was done using wooden stakes or chalk, but with RTK × AR, "virtual stakes" can be placed on the AR display.

By measuring the coordinates of stakeout positions on the design drawings with a smartphone, and displaying virtual stakes or markers on the screen at those points, it becomes possible to accurately indicate positions even in areas where it’s difficult or dangerous to physically drive stakes, such as on rock beds or steep slopes. Additionally, 3D design models like BIM/CIM can be overlaid onto the on-site scenery, enabling real-time sharing of the completed design on-site.

This allows not only construction managers but also heavy machinery operators, craftsmen, clients, and even nearby residents to intuitively understand and visualize the final result, improving communication. In one general contractor’s site, the process of confirming construction locations while viewing overlaid design data in AR helped eliminate the need to continually unroll paper plans and re-mark positions, resulting in time savings in meetings and work. As part of advancing DX in construction, RTK × AR is strongly supporting both visualization and efficiency on-site.

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Convenience in Infrastructure Inspection and Maintenance
RTK × AR is also highly useful in regular inspections of roads and bridges, as well as in the maintenance of slopes and structures. For example, when inspecting cracks at tunnel entrances or on slopes, it is necessary to re-photograph the same composition and position as during the previous inspection for comparison. Traditionally, workers had to find the position on-site by looking at previous photos and manually adjust the camera angle, requiring skilled craftsmanship. With the smartphone app that uses RTK × AR, the coordinates and camera orientation from the previous photo are recorded. When the smartphone is held at the site, simply aligning it in the direction indicated by the AR arrow allows the user to take a photo at the same position and angle as before.

In practice, the LRTK app displays the angular difference between the current photo and the previous one, and when the alignment is perfect, the screen frame changes to green, providing intuitive guidance. This allows anyone to easily perform repeat observations.

As a result, comparing cracks and deformations becomes more accurate and faster, improving the reliability and efficiency of inspection work. Furthermore, by combining an iPhone/iPad equipped with LiDAR and RTK, it is possible to easily capture 3D point cloud data of the site.

The point clouds acquired are tagged with high-precision global coordinates, which is useful for monitoring terrain changes over time and managing as-built conditions. In this way, RTK × AR contributes to enhancing measurement data and simplifying comparison tasks in infrastructure maintenance sites.

Use Cases in Civil Engineering and Surveying
The introduction of RTK × AR technology is also advancing in small and medium-sized civil engineering companies and surveying firms. One surveyor mentioned, "Previously, we rented expensive GNSS receivers, but since introducing RTK devices that can be used with a smartphone, I can now handle most of the surveying with my own iPhone." This has made fieldwork more agile, and the ability for site supervisors to conduct surveys without needing to arrange a surveying team has increased scheduling flexibility.

In another case, RTK × AR was put to use during emergency surveying after a heavy rain disaster. On-site workers used smartphones to instantly measure the coordinates of key areas and transmit the data to the cloud. The technicians in the remote office received the data in real-time and used it to create drawings, which helped to make quick decisions for recovery. These cases show that RTK × AR technology is not only improving surveying accuracy but also transforming business processes. Tasks that were traditionally divided are now seamlessly connected with digital technology, and with faster information sharing, the responsiveness on-site has dramatically improved.

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Introduction to LRTK Products

One of the leading solutions that enable RTK × AR surveying is the LRTK product line provided by Refexia Inc. The "LRTK Phone," developed by the company, is a high-precision GNSS receiver integrated with a smartphone. This pocket-sized device enables centimeter-level positioning simply by attaching it to an iPhone or iPad. Weighing approximately 125g and only 13mm thick, the compact and lightweight body contains both the battery and antenna, and it can be easily attached and detached from the dedicated smartphone cover with just one touch. This single device encompasses all the functionalities of a surveying tool and is easy to carry. It is truly a "practical device for on-site use." Additionally, a model that supports Japan’s satellite positioning service CLAS is available, allowing for positioning even in areas without mobile network coverage, such as mountainous regions, by receiving correction data via satellite.

This enables stable high-precision surveying in a wider range of field environments.

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The features of the LRTK series extend beyond just the hardware. The dedicated LRTK app offers a simple UI that allows for single-point positioning as well as continuous positioning (log recording), and it also includes a function to automatically tag high-precision positioning information (latitude, longitude, elevation, and orientation) to photos taken. This makes it possible to plot on-site photos on a map and share them to the cloud, including the direction of the photo, with just one tap.

Additionally, there is a feature that allows you to set recorded points as target locations and navigate the distance and direction to the destination on a map screen or AR radar screen.

The LRTK series comes equipped with a variety of tools for measuring, recording, and displaying data, such as the aforementioned AR stakeout, AR-based positioning guidance, and target positioning (measuring the position of a target object through the camera). This all-in-one package is a major advantage.

While some competing products feature standalone GNSS receivers or tablet-integrated devices that only provide surveying functions, LRTK excels by offering comprehensive support for cloud-sharing positioning data, AR display, and point cloud acquisition. Moreover, it is more affordable compared to similar surveying equipment, with an easy-to-implement initial setup. In fact, there are voices saying, "Thanks to LRTK, the era has come where on-site workers each have a smartphone surveying device," and it has received high praise as a product that balances high performance with low cost.