Visualize Survey Data with AR! How Network RTK Opens the Future of the Field

Table of Contents

• Introduction: Challenges of Conventional Surveying and Construction Management and the Need for DX

• How Network RTK Works and Why It Achieves Centimeter Accuracy (cm level accuracy (half-inch accuracy))

• Changes Brought to the Field by the Fusion of AR Visualization and Smartphone RTK

• Overview of LRTK (Receiver, App, Cloud) and Differences from Other Solutions

• Use Cases: As-built Management, Stake Setting, Underground Infrastructure Display, AR Guidance, etc.

• Automation Benefits Such as Point Cloud Differencing and Area/Volume Measurement

• Streamlining Field Construction Management and Reducing Training Burden with a Single Smartphone

• Examples of Improved Safety, Labor and Effort Reduction, and Error Reduction on Site

• Conclusion: Recommendation for Introducing Simple Surveying with LRTK

• FAQ

Introduction: Challenges of Conventional Surveying and Construction Management and the Need for DX

Surveying work and construction management at construction sites have seen little major change for many years and have faced multiple challenges. Conventional surveying uses specialized equipment such as total stations and levels, with several people setting out reference points and checking as-built conditions. This method requires time and effort for equipment setup, adjustment, and target placement, and limits the number of points that can be measured in a day. Moreover, converting survey results into drawings requires specialized knowledge and experience, and with the shortage of skilled technicians becoming serious, it has become difficult to maintain surveying quality and speed on site.

In addition, on construction sites, a lot of manual work and visual checks were required to confirm whether work was being carried out "according to the drawings." Workers had to rely on paper drawings and marked stakes and imagine the finished result while working, which made mistakes more likely for those with little experience. Such inefficiency and the risk of human error are recognized as problems that the construction industry as a whole must solve.

Against this background, the construction industry has recently been loudly calling for ICT adoption and DX (digital transformation). In particular, it is said that the surveying field has seen little technological innovation for about 50 years, and if this continues, productivity may stagnate and the industry's competitiveness may decline. New technologies such as drone surveying, 3D scanners, and RTK positioning are attracting attention as trump cards to compensate for labor shortages and dramatically improve work efficiency and accuracy. Especially, high-precision positioning using network RTK has dramatically improved accuracy from the meter-level GPS positioning of the past and is becoming an indispensable foundational technology for as-built management and automated control of heavy machinery.

Alongside these high-precision positioning technologies, AR (augmented reality) has rapidly become practical in recent years. By simply holding a smartphone or tablet at the site, design data and survey data can be overlaid on the real-world image, allowing intuitive understanding of site conditions. A method that combines this network RTK and AR—sometimes called “AR surveying”—has emerged, and an era has arrived in which high-precision surveying and site visualization can be performed with just a smartphone. This article explains the mechanism behind centimeter-level positioning (cm level accuracy (half-inch accuracy)) using network RTK, and the transformation brought to the field by the fusion of AR visualization and smartphone RTK. We will also introduce the features and use cases of our smartphone RTK solution "LRTK" and clarify the concrete benefits that DX in construction sites can bring. Finally, we address frequently asked questions (FAQ) to resolve doubts about network RTK and AR utilization.

How Network RTK Works and Why It Achieves Centimeter Accuracy (cm level accuracy (half-inch accuracy))

First, let us explain what network RTK is, how it works, and why it can achieve high accuracy. RTK stands for Real-Time Kinematic and is one surveying method that uses GNSS (satellite positioning such as GPS and GLONASS). Standalone positioning (such as a smartphone’s GPS) typically has position errors of several meters due to satellite signal errors. However, RTK positioning uses a separate reference station (base) whose coordinates are known accurately and observes the satellites simultaneously with the mobile unit (rover) used on site. By sending the error information received at the reference station to the rover in real time and applying corrections to the position calculation, errors can be reduced to a few centimeters (a few in).

In other words, by taking the difference between the "stationary receiver" and the "moving receiver," common error factors such as atmospheric effects and satellite clock errors are canceled out, allowing calculation of a high-precision relative position. According to materials from the Geospatial Information Authority of Japan, while standalone positioning has errors of several meters, using the RTK method can reduce errors to several centimeters. This is because analysis of the signal phase difference from satellites enables a calculation known as a fixed solution (Fix), which can resolve positions to centimeter-level accuracy. RTK receivers are equipped with high-performance antennas and dual-frequency GNSS chips for such high-precision calculations, and the rover performs real-time computation.

What is important here is the mechanism of network RTK. Traditionally, conducting RTK positioning required users to set up reference station equipment near the site themselves. Today, however, users can access a network of continuously operating reference stations (GNSS reference stations) maintained nationwide or private reference station services via the Internet. Using a protocol called Ntrip to obtain reference station data (correction information) over the network makes RTK positioning possible without placing your own reference station on site. For example, in Japan there is the Geospatial Information Authority’s network of continuously operating reference stations (about 1,300 GNSS reference stations) and correction information services operated by local governments and private companies. By using such networked RTK (VRS-type, etc.), data for a virtual reference point near the observation point is provided, enabling stable centimeter accuracy (cm level accuracy (half-inch accuracy)).

Also, as a Japan-specific high-precision positioning infrastructure, the Quasi-Zenith Satellite System (QZSS) “Michibiki” provides CLAS (Centimeter-Level Augmentation Service), which can also be utilized. CLAS transmits augmentation signals directly from satellites, and compatible receivers can receive correction information even in mountainous areas or remote islands where mobile networks do not reach. With both network RTK and CLAS being established, an environment is increasingly in place where centimeter-level positioning (cm level accuracy (half-inch accuracy)) can be performed easily across almost the entire country.

Thus, high-precision positioning technology using network RTK is beginning to be used by surveyors and construction management technicians for as-built management and heavy machinery position control, and is becoming indispensable in civil engineering and construction sites. The ability to obtain precise position information in real time provides the foundation to digitize and automate tasks that previously relied on human labor and experience.

Changes Brought to the Field by the Fusion of AR Visualization and Smartphone RTK

Next, let us look at the changes brought to the field by combining high-precision RTK positioning and AR. Conventional smartphone AR apps required placing markers on site or letting the camera recognize the floor or walls to perform initial alignment when overlaying CG models onto real space. There was also the issue of "drift," where the virtual model gradually desynchronizes from reality as the user moves. This occurs because errors accumulate in the smartphone’s gyro and camera-based self-positioning, and especially outdoors when moving over long distances, large position shifts can occur.

However, if an RTK-capable GNSS receiver is attached to a smartphone and the user’s position coordinates can be obtained with centimeter accuracy (cm level accuracy (half-inch accuracy)), AR display based on absolute coordinates becomes possible. In other words, by directly associating the latitude, longitude, and height on the design data with the real-time self-position, 3D models and guide lines can be displayed at the exact positions in real space. Even if the user walks around the site, the virtual model remains fixed in the global coordinate system, maintaining stable, non-drifting display. In other words, troublesome initial calibration work is unnecessary, and AR linked to surveying coordinates can be realized.

This fusion of RTK and AR allows users to check the completed image of a structure or construction guides on the spot. For example, if a sign to be installed in a location with poor visibility is planned, displaying the sign model precisely in AR immediately shows where it should be installed. RTK can also capture the smartphone user’s orientation (heading) with high accuracy, so the orientation of 3D models remains correct when viewed from various angles. Conventional GPS lacked the accuracy to achieve such precise overlay, but with centimeter accuracy (cm level accuracy (half-inch accuracy)) RTK, the virtual and real worlds can align perfectly on the smartphone screen.

Thus, AR visualization using smartphone RTK is a groundbreaking technology that overlays digital information directly onto real scenery to “visualize” it. Tasks that used to require carrying a drawing and mentally mapping it out on site are now rendered as the completed image or construction instructions directly on the smartphone screen, allowing anyone to understand intuitively. Communication and decision-making on site become significantly smoother, and this helps prevent work errors.

Overview of LRTK (Receiver, App, Cloud) and Differences from Other Solutions

The solution that makes it easy to utilize network RTK and AR on site as described above is our product, LRTK. LRTK is an integrated system consisting of a pocket-sized ultra-compact RTK-GNSS receiver, a dedicated smartphone app, and a cloud service. By attaching the antenna-integrated receiver to the smartphone with one touch and connecting via Bluetooth, the smartphone itself transforms into a centimeter-accuracy measuring instrument. The dedicated app acquires correction data from network RTK services and Michibiki’s CLAS in real time to achieve high-precision positioning. The coordinates of acquired points can be converted and displayed in the World Geodetic System Japan Plane Rectangular Coordinate System and elevations (geoid height), allowing direct comparison with existing drawings and survey control points.

The LRTK terminal (the receiver itself) is very small and lightweight at approximately 125 g and about 1.3 cm thick, and its built-in battery enables continuous measurement for several hours without an external power source. It also has dustproof and waterproof performance for reliable use in harsh construction site environments. The dedicated app runs on iPhone/iPad (and some Android devices), and positioning and measurement operations feature an intuitive UI that anyone can handle. Acquired point cloud data and photos can be uploaded to the cloud immediately and shared in real time with office PCs and other staff. This makes it easy to confirm the information measured on site with internal stakeholders on the spot.

Summarizing the main features of LRTK compared to other solutions:

• Ease and labor savings: Surveying that used to require two people with a total station or large GNSS receiver can be completed by one person with just a smartphone and a compact device using LRTK. Site supervisors or construction managers can perform quick surveys and as-built checks on the spot, reducing the need to dispatch survey teams.

• Portability and responsiveness: Because the device fits in a pocket and can be taken out and used whenever needed, on-site mobility is greatly improved. Its light and compact form factor allows it to be carried at all times and respond immediately to sudden measurement needs.

• Low cost: LRTK is offered at a far more reasonable price range compared to conventional high-precision surveying equipment. Without having to acquire expensive instruments in multiple units, provisioning one device per person becomes realistic, making it easy for small and medium-sized companies to adopt.

• All-in-one functionality: In addition to high-precision GNSS positioning, the app integrates features required on site into a single app, including 3D scanning using the smartphone’s LiDAR and camera, point cloud generation, overlay display of design data via AR, photogrammetric measurements, and area/volume calculation. Measured data is saved to the cloud and can be smoothly used for office CAD comparison or BIM model checks.

• High extensibility: LRTK comes in multiple models, some equipped with inclination correction and others, as mentioned earlier, that can directly receive the CLAS signal (“offline-capable models”). Models with inclination correction detect the tilt of the device with sensors and automatically correct to record accurate point coordinates even when the pole cannot be held vertically. This ensures accuracy even when measuring with a tilted pole over obstacles, enabling positioning in places that were previously unmeasurable. CLAS-compatible models can directly receive correction information from satellites in areas without mobile coverage—such as mountain areas and near tunnel openings—so surveying can continue with centimeter accuracy (cm level accuracy (half-inch accuracy)) even when network connection is difficult.

In this way, LRTK is an innovative solution that meets all kinds of on-site positioning and surveying needs with a single smartphone. Since its release in 2022, a wide range of users—from site supervisors at general contractors to small civil engineering firms and infrastructure maintenance technicians—have begun using it as a site DX tool, and the new workflow of “the smartphone becoming an all-purpose surveying instrument” is quietly spreading.

Use Cases: As-built Management, Stake Setting, Underground Infrastructure Display, AR Guidance, etc.

LRTK, which combines smartphone RTK and AR technology, is powerful in the following actual construction site scenarios:

• As-built management: You can check and measure as-built conditions (completed structures and terrain) on the spot. Scanning the work area with an LRTK-enabled smartphone instantly acquires the 3D shape of embankments or structures as point cloud data. The obtained point cloud can be overlaid with the design model to check on site whether positions, heights, and shapes conform to specifications. For example, you can scan a road subgrade immediately after leveling and compare it with the design elevation, color-coding any low spots. This allows you to identify insufficient fill and perform additional work immediately without waiting for later surveys. Traditionally, verification would occur after completion by a surveying team, causing rework risk, but when construction staff can verify as-built conditions in real time, it greatly contributes to quality assurance and prevention of rework. Additionally, volumes and areas can be automatically calculated from the acquired point cloud, significantly streamlining earthwork quantity calculation and as-built drawing creation.

• Stake setting and layout: For stake setting and layout tasks to establish reference lines and locations for buildings and structures, AR guidance is very useful. When holding a smartphone equipped with LRTK on site, virtual stakes or reference lines from the design are displayed in real time at the design positions. Workers need only mark or install stakes according to those indications, greatly reducing the layout work that previously required setting batter boards and using tape measures. Even on steep slopes or paved surfaces where it is physically difficult to drive stakes, accurate layout is possible by referencing the points displayed on screen. As a result, layout work that required multiple people can be handled by one person, preventing mistaken placement of survey points and subsequent rework.

• Underground infrastructure visualization: Locations of buried water and sewer pipes, gas pipes, power and communication cables can be visualized in AR to enable safer and more efficient work. If you preload the buried utilities drawing into the LRTK app, you can display the underground piping route through your smartphone as if seeing through the ground. This helps prevent accidental damage to lifelines during excavation and provides reassurance when installing new pipes by checking clearances relative to existing infrastructure. AR display is also powerful when identifying buried valves or structures during inspections. Even in dark areas or complex piping networks, you can accurately locate invisible targets by following markers displayed on the smartphone screen.

• AR-based work guidance: LRTK can also be used as AR navigation for heavy equipment operators and workers. For example, in excavation work, preconfigured design excavation lines and slopes can be projected onto the ground or wall via AR, and an operator can move the excavator along these virtual guides to achieve the correct excavation shape. Following AR guide lines enables target earthwork without batter boards, improving productivity. During steel erection, displaying virtual models at column and beam installation positions while operating cranes lets operators visually check for misalignment and place members without error. In night work or low-visibility conditions, highlighting the next member to be installed or the work area with AR markers allows even inexperienced workers to work safely and confidently.

As shown above, smartphone RTK + AR technology is useful in virtually every construction scenario. It can be used to overlay the finished image on site during the planning stage to gain stakeholder consensus, tag inspection points in large infrastructure maintenance with AR, and its application range will continue to expand.

Automation Benefits Such as Point Cloud Differencing and Area/Volume Measurement

Traditionally, calculating fill or excavation volumes and checking differences between as-built conditions and design drawings relied on manual calculations or comparisons on drawings. Using LRTK can greatly automate these processes. By overlaying the point cloud data acquired by smartphone with the design 3D model, you can immediately visually confirm differences on site. For example, you can generate a heat map on the spot that color-codes elevation differences between the design surface and the measured point cloud, making it easy to identify locations where deviations exceed allowable ranges. This reduces the risk of discovering problems after work completion and having to redo work.

Moreover, automatic calculation of areas and volumes from point cloud data is a major advantage. Previously, it took time to calculate earthwork quantities from survey data, but you can now instantly compute fill volume from terrain scanned on a smartphone or measure the area of an as-built surface. For example, in an embankment project you can decide on site how many cubic meters of additional fill are needed to reach the design elevation, enabling quick decision-making.

These automation features significantly speed up the construction PDCA cycle on site. Since surveying, analysis, and visualization can be completed with one smartphone, construction managers can make decisions and move to the next task on the spot. Time-consuming tasks such as creating as-built drawings and quantity calculations can be completed in a short time, contributing to shorter schedules and cost savings. Furthermore, transcription and calculation errors by hand are reduced, enabling quality control at digital precision. As a benefit of site DX, parts of work that previously relied on craftsmen’s intuition and experience can be replaced with objective, data-driven decisions, improving reproducibility and reliability of construction.

Streamlining Field Construction Management and Reducing Training Burden with a Single Smartphone

The fact that many steps of surveying and construction management can be completed with a single smartphone thanks to LRTK leads to increased productivity on site. Tasks that previously required a specialist surveyor to check control points and as-built conditions can be performed by the construction manager on the spot, reducing waiting times for external scheduling and coordination losses between departments. For example, if a final elevation check is needed before concrete pouring, you can take out a smartphone and measure and confirm immediately. Data is automatically shared to the cloud, reducing the effort to return to the office to create drawings or reports. These accumulative efficiencies directly shorten schedules and reduce costs, contributing to overall DX promotion on site.

Using a general-purpose device such as a smartphone also lowers the learning hurdle. Intuitive AR display makes it easier for non-experts to understand discrepancies between design and actual conditions, and operations are completed with simple button actions in the smartphone app. Conventional surveying equipment demanded specialized knowledge and experience, and it took a long time for new personnel to become proficient. With LRTK, field staff who have received some training can handle it in a short period. Even without in-depth knowledge of surveying theory, following on-screen instructions yields accurate data, allowing newcomers and younger staff to become productive more quickly. This is a major advantage for the construction industry, which struggles with labor shortages.

Additionally, the visual nature of smartphone AR facilitates smoother information sharing on site. Tacit knowledge and tips previously held only in the minds of veterans can be visualized as AR markers and models and shared with the whole team. Instructions that were difficult to convey on paper drawings become immediately clear when shown on the screen. As a result, the time and effort for training and communication are reduced and rework due to miscommunication is decreased. Construction management using a single smartphone is transforming the way knowledge is transmitted on site, helping create an environment in which everyone can effectively use digital tools.

Examples of Improved Safety, Labor and Effort Reduction, and Error Reduction on Site

Actual results reported from sites that introduced smartphone RTK and AR include the following:

• Case at a civil engineering site: Using an LRTK-equipped smartphone to perform reference point surveying, as-built point cloud scanning, and AR overlay checks against the design model, processes that previously took several days with a total station, laser scanner, and PC analysis were completed the same day with a single smartphone. Time spent setting up survey equipment and post-processing was eliminated, and completing both work and verification on the same day led to significant schedule reductions. Because the construction management staff completed everything without calling a specialized surveying team, manpower coordination was simplified and costs were reduced.

• Another construction site case: In excavation work, CAD data of the planned excavation area based on the design was loaded into the LRTK app and displayed in AR during work. The heavy equipment operator moved the excavator according to the virtual excavation guide shown on the smartphone screen, achieving accurate excavation shapes without batter boards. As a result, personnel required for stake setting were reduced and excavation errors were minimized, with almost no rework. AR-based construction guidance therefore delivers both labor savings and quality improvements.

• Infrastructure inspection case: In railway nighttime maintenance, LRTK and AR were used to display parts to be replaced and cable routes with AR markers in advance, enabling workers to accurately locate components even in darkness. This eliminated time spent searching with flashlights and allowed all planned inspections and replacements to be completed within the limited work window. Oversights and misidentification-related errors were eliminated, improving safety and work quality. In areas without mobile coverage such as tunnels or mountains, CLAS-compatible LRTK models can maintain centimeter accuracy (cm level accuracy (half-inch accuracy)), making them effective for offline infrastructure inspection and disaster surveys.

These examples demonstrate that the combination of smartphone RTK and AR provides benefits proven in practice, not just theory. Improvements in safety, workforce reduction, efficiency, and error reduction—achieving multiple gains at once—have been reported across many sites, and wider adoption is expected going forward.

Conclusion: Recommendation for Introducing Simple Surveying with LRTK

The fusion of network RTK and AR visualization technologies is becoming a future standard at construction sites. Being able to handle surveying through construction management with a single smartphone provides a powerful solution to industry challenges such as labor shortages and knowledge transfer. Actively adopting the latest technologies rather than clinging to old conventions is key to improving productivity and ensuring safety and quality.

That said, “high-precision positioning” and “AR” may sound difficult at first. However, solutions like LRTK make it possible to start high-precision surveying simply without specialized knowledge. The ability to introduce digital tools at the field level without large initial investment or long training periods is a major attraction. Once used, you will likely be surprised by the intuitive operation and visible results.

The construction industry is now poised for major change through DX. We have seen how combining centimeter accuracy (cm level accuracy (half-inch accuracy)) from network RTK with intuitive AR visualization dramatically streamlines field workflows. If you have not yet adopted these technologies, why not start easily with a smartphone and LRTK? You can experience the effects of site DX from a small step, and it will eventually contribute to strengthening your company’s overall competitiveness. We encourage you to try smartphone RTK and AR technologies—future standards—on your site.

FAQ

What is network RTK?

Network RTK is RTK positioning that uses data from multiple GNSS reference stations (such as continuously operating reference stations) installed in various locations and accessed over a network. Users receive correction information (reference station data) over an Internet connection and apply it to their receiver. This enables high-precision RTK positioning without placing a private reference station at the site. In Japan, the Geospatial Information Authority’s network of continuously operating reference stations and private services using the VRS method are widely used, and with just a smartphone and a small receiver, centimeter-level positioning (cm level accuracy (half-inch accuracy)) can be achieved easily.

What is CLAS?

CLAS (Centimeter-Level Augmentation Service) is an augmentation signal service provided by Japan’s Quasi-Zenith Satellite System (QZSS) Michibiki for high-precision positioning. Compatible RTK receivers can receive centimeter-level correction information directly from satellites without relying on mobile communications. The service area covers most of Japan, and it is used as a means of performing high-precision positioning in environments where the Internet does not reach, such as mountainous areas and remote islands. Some LRTK models also support CLAS reception, making them highly effective at sites outside mobile coverage.

Are the positions of virtual models displayed in AR stable?

Yes. Using high-precision RTK position information, the positions of models overlaid in AR are very stable. In normal smartphone AR, models can drift slightly with movement, but because RTK places models based on absolute coordinates, they do not generally drift. Virtual objects remain in the correct positions as you walk around the site, and their orientation and scale do not change unexpectedly. However, if the device’s gyro or camera recognition temporarily malfunctions, slight display errors may occur; if positioning is in a Fix solution state, position accuracy is maintained at centimeter-level (cm level accuracy (half-inch accuracy)).

What should I do in places where satellite signals cannot be received?

RTK positioning requires reception of GNSS satellite signals and therefore cannot generally be used indoors or deep inside tunnels where satellites cannot be observed at all. In such cases, you must either perform local layout based on known points acquired outdoors in advance or use conventional optical surveying equipment (such as a total station) in combination. If satellite visibility is only partially blocked, you can maintain accuracy by taking longer observation times for averaging or by moving observation points to locations with a clearer view. In mountainous areas where only the mobile network is out of range but satellite reception is possible, you can continue high-precision positioning by using Michibiki’s CLAS or a locally deployed radio reference station. Higher-end LRTK models include ultra-small radio or CLAS reception features, enabling surveying in offline environments.