Visualize Survey Data with AR! The Future of Construction Sites Opened by Network RTK

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

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

• Overview of LRTK (Receiver, App, Cloud) and How It Differs from Other Solutions

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

• Benefits of Automating Point Cloud Differencing and Area/Volume Measurement

• Efficiency Gains and Reduced Training Load from Managing Site Work with Just a Smartphone

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

• Conclusion: Recommendations for Introducing Simple Surveying with LRTK

• FAQ

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

Surveying tasks and construction management on construction sites have gone for many years with little major change and have faced multiple challenges. Traditional surveying used dedicated instruments such as total stations and levels, with multiple personnel performing setup of reference points and verification of as-built conditions. This approach requires time and effort for instrument setup, adjustment, and target placement, and limits the number of points that can be measured in a day. Converting survey results into drawings requires specialized knowledge and experience, and with a growing shortage of skilled technicians, maintaining on-site surveying quality and speed has become increasingly difficult.

Moreover, construction management has required many manual tasks and visual checks to confirm whether work is being carried out "according to the drawings." Workers had to rely on paper drawings and marked stakes, visualizing the completed structure in their heads as they worked—making it easy for less experienced personnel to make mistakes. Such inefficiencies and risks of human error are recognized as industry-wide problems in construction.

Against this backdrop, the construction industry has recently been calling loudly for ICT adoption and DX (digital transformation). In particular, it is said that the surveying field has seen little major technological innovation for about 50 years, and without change productivity may stagnate and industry competitiveness may decline. New technologies—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. High-precision positioning using network RTK, in particular, has dramatically improved accuracy over conventional meter-level GPS positioning and is becoming an essential foundational technology for as-built management and automatic control of construction machinery.

Alongside these high-precision positioning technologies, AR (augmented reality) has rapidly reached practical use in recent years. By simply holding a smartphone or tablet on site, design data and survey data can be overlaid on real-world imagery, enabling intuitive understanding of site conditions. The approach that combines this network RTK and AR—what might be called "AR surveying"—has emerged, bringing an era in which high-precision surveying and on-site visualization can be achieved with a single smartphone. This article explains how network RTK achieves centimeter-level positioning and how the fusion of AR visualization and smartphone RTK is transforming the field. We also introduce our smartphone RTK solution, LRTK, its features and use cases, and clarify the concrete benefits that DX brings to construction sites. Finally, we address frequently asked questions (FAQ) to resolve common doubts about network RTK and AR utilization.

How Network RTK Works and Why It Achieves Centimeter 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 a surveying method that uses GNSS (satellite positioning systems such as GPS and GLONASS). Standalone positioning (e.g., smartphone GPS) typically produces position errors on the order of several meters due to satellite signal errors. RTK positioning, however, uses a separate reference station (a fixed station) whose coordinates are known accurately and observes the satellites simultaneously with the moving receiver (the rover) used in the field. By sending the error information received at the reference station to the rover in real time and applying corrections in the position calculations, errors can be reduced to on the order of several centimeters.

In other words, by taking the difference between the "stationary receiver" and the "moving receiver," common error sources such as atmospheric effects and satellite clock errors are canceled out, enabling highly accurate relative positioning. According to materials from the Geospatial Information Authority of Japan, while standalone positioning typically has errors of several meters, using an RTK method can reduce errors to several centimeters. This is because RTK can perform calculations called "fixed solutions (Fix solution)" that analyze phase differences of signals from satellites and resolve positions at the centimeter level. RTK receivers are equipped with high-performance antennas and dual-frequency GNSS chips to perform such high-precision computations, and the rover performs real-time processing for positioning.

An important part of this is the mechanism of network RTK. Traditionally, to perform RTK positioning, users had to set up their own reference-station equipment near the site. Today, however, users can utilize networks of continuously operating reference stations (CORS) deployed nationwide or private reference station services over the Internet. Using a protocol called Ntrip to obtain reference station data (correction information) via the network makes it possible to perform RTK positioning without deploying a local reference station. For example, in Japan the Geospatial Information Authority of Japan operates a network of continuously operating reference stations (about 1,300 GNSS reference stations), and various municipalities and companies provide correction-data services. By using such network RTK (e.g., VRS methods), data for a virtual reference point near the observation location is provided, yielding stable centimeter-level accuracy.

Also available as a Japan-specific high-precision positioning infrastructure is CLAS (Centimeter Level Augmentation Service) provided by the Quasi-Zenith Satellite System (QZSS) "Michibiki." CLAS transmits augmentation signals directly from satellites, and compatible receivers can receive correction data even in mountainous areas and remote islands where cellular signals do not reach. With both network RTK and CLAS becoming available, environments in which centimeter-level positioning can be performed easily are being established across almost all of Japan.

High-precision positioning via network RTK is being used by surveyors and construction managers for as-built management and machinery position control and is becoming indispensable on civil engineering and construction sites. Being able to obtain precise position information in real time forms the foundation for digitally automating and enhancing tasks that previously relied on human hands and experience.

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

Next, let us look at the changes that combining high-precision RTK positioning with AR brings to the field. Conventional smartphone AR apps required placing markers on site or having the camera recognize floors or walls to perform initial alignment when overlaying CG models on real space. They also suffered from "drift," where virtual models gradually become misaligned from reality as the user moves. This occurs because the smartphone's gyro and camera-based self-positioning accumulate error, and in outdoor cases where users move long distances, substantial position shifts can occur.

However, if a smartphone is equipped with an RTK-capable GNSS receiver and can obtain its own position coordinates at centimeter-level accuracy, AR displays based on absolute coordinates become possible. In other words, by directly linking latitude, longitude, and elevation from the design data to the real-time self position, 3D models and guide lines can be displayed at accurate positions in real space. As users walk around the site, virtual models remain fixed in the Earth-coordinate system, maintaining stable, drift-free display. In other words, cumbersome initial calibration work becomes unnecessary, and AR linked to surveying coordinates can be realized.

By fusing RTK and AR in this way, the completed appearance of structures to be installed and construction guides can be checked on site. For example, even for a sign to be installed in a location with poor visibility, displaying the sign model in AR at the precise location lets you immediately know exactly where it should be erected. Because RTK can also capture the smartphone user's orientation (heading) with high accuracy, the model's orientation remains correct even when viewed from different angles. Ordinary GPS lacked the accuracy to achieve such precise overlays, but with centimeter-level RTK the virtual and real worlds can align perfectly on the smartphone screen.

Smartphone RTK-based AR visualization is thus a revolutionary technology that directly overlays digital information onto real scenery to "make the invisible visible." Tasks that previously required referring to drawings while imagining the finished result can now be understood intuitively because the expected completion view and construction instructions are shown directly on the phone screen. On-site communication and decision-making become much smoother, helping to prevent work errors.

Overview of LRTK (Receiver, App, Cloud) and How It Differs from Other Solutions

A solution that makes it easy to use the network RTK and AR described above on site is our LRTK. LRTK is an integrated system consisting of a pocket-sized ultra-compact RTK-GNSS receiver, a dedicated smartphone app, and cloud services. By attaching a receiver with an integrated antenna to a smartphone with one touch and connecting via Bluetooth, the smartphone instantly becomes a centimeter-level surveying instrument. The dedicated app acquires correction data from network RTK services and Michibiki's CLAS and realizes real-time high-precision positioning. Collected point coordinates can be converted and displayed in the World Geodetic System and Japan Plane Rectangular Coordinate System as well as elevation (geoid height), enabling direct comparison with existing design drawings and survey control points.

The LRTK device (the receiver itself) is very small and light—about 125 g and approximately 1.3 cm thick—and its built-in battery enables several hours of continuous measurement without an external power source. It is dust- and water-resistant, so it can be used safely in harsh construction-site environments. The dedicated app runs on iPhone/iPad (and some Android devices), and positioning and measurement operations are designed with an intuitive UI so anyone can use it easily. Acquired point cloud data and photos can be uploaded to the cloud immediately and shared in real time with PC users at the office or other staff. This makes it easy to confirm measured information on site with office stakeholders.

Key features of LRTK compared with other solutions include:

• Ease and labor savings: Surveys that traditionally required a two-person team using a total station or large GNSS receiver can be completed by a single person with LRTK using just a smartphone and a compact device. Site supervisors and construction managers can perform quick surveys and as-built checks themselves, reducing the need to arrange a survey team.

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

• Low cost: LRTK is offered at a significantly more affordable price range compared with conventional high-precision surveying equipment. Because you do not need many expensive devices, equipping one person with a unit per person becomes realistic, making it easier for small and medium-sized companies to adopt.

• All-in-one features: In addition to high-precision GNSS positioning, the app integrates features required on site into a single app—3D scanning using the smartphone’s LiDAR and camera, point cloud generation, overlay display of design data via AR, photo measurement, and area/volume calculations. Measured data is stored in the cloud and can be used seamlessly in the office to compare with CAD drawings or BIM models.

• High extensibility: LRTK comes in multiple models, some of which offer tilt compensation and some "out-of-coverage models" that can receive CLAS signals directly. A model with tilt compensation detects pole tilt with sensors and automatically corrects to record accurate point coordinates even when the pole cannot be held vertically. This maintains accuracy even when measuring with the pole tilted around obstacles, enabling measurements in places that were previously inaccessible. CLAS-compatible models can obtain correction information directly from satellites in areas without cellular reception—such as mountainous regions or tunnel entrances—allowing surveys to continue at centimeter accuracy even when network connectivity is difficult.

LRTK is therefore an innovative solution that meets various on-site positioning and surveying needs with just a smartphone. Since its release in 2022, site supervisors at general contractors, small and medium civil engineering firms, and infrastructure maintenance engineers have started using it as a site DX tool, and the new site style of "smartphones becoming universal surveying devices" is quietly spreading.

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

LRTK, which combines smartphone RTK and AR technologies, proves powerful in the following on-site scenarios:

• As-built management: You can check and measure the as-built condition (completed structures and terrain) on site. Scanning the construction area with an LRTK-equipped smartphone immediately produces a 3D point cloud of embankments or structures. Overlaying the design model on the acquired point cloud allows on-site checks to see whether positions, heights, and shapes are within specifications. For example, right after grading a roadbed, you can scan with a smartphone and compare to the design elevation, using color-coding to show any low spots. This enables you to identify insufficient fill volumes on the spot and apply additional work immediately rather than waiting for later verification. Traditionally, confirmation was done post-completion by a survey team, risking rework, but now construction staff can verify as-built conditions in real time, significantly contributing to quality assurance and preventing rework. Volume and area calculations can also be automated from the point cloud, greatly streamlining earthwork quantity calculations and as-built drawing creation.

• Stake setting and layout work: AR guidance is highly useful when setting out reference lines and positions for buildings and structures. When you hold up an LRTK-equipped smartphone, virtual stakes and reference lines from the design appear in real time at the designed positions. Workers can mark or place stakes by following these visual cues, greatly reducing the traditional need for setting up batter boards (chōhari) and using tape measures. Even on steep slopes or paved surfaces where it is physically difficult to drive stakes, you can use the points displayed on the screen to accurately set out positions. As a result, layout work that used to require multiple people can be done by one person, preventing mistakes in point placement that would otherwise cause rework.

• Underground infrastructure visualization: LRTK can visualize buried water and sewer pipes, gas mains, power and communication cables in AR, enabling safer and more efficient work. If you preload as-built drawings of buried assets into the LRTK app, you can view routes of underground piping as if you were seeing through the ground on your smartphone. This helps prevent accidental damage to lifelines during excavation and allows new installation work to be performed while confirming clearances from existing infrastructure. For inspections, AR is powerful when locating buried valves or structures: even in dark or complex piping networks, you can follow markers on the smartphone to accurately find unseen targets.

• AR-based work guidance: LRTK can also be used as AR navigation for machine operators and workers. For example, during excavation, you can preload the design excavation line and slope into the LRTK app and project it on the ground or wall in AR; the operator can then move a digger along the virtual line to achieve the precise excavation profile. Following AR guide lines enables accurate earthwork without batter boards, improving efficiency. In steel erection, virtual models of columns or beams can be displayed at installation locations during crane operations, allowing visual checks for misalignment while placing members. Even at night or in poor visibility, highlighting the next member or work area with AR markers helps less experienced workers carry out tasks safely and without hesitation.

As shown above, smartphone RTK + AR technology is useful in all kinds of construction tasks. It can be used during planning to overlay the completed image on site for consensus building among stakeholders, and in large-scale infrastructure maintenance to tag inspection points with AR—its range of applications will continue to expand.

Benefits of Automating Point Cloud Differencing and Area/Volume Measurement

Traditionally, calculating fill and excavation volumes and checking differences between as-built conditions and design relied on manual calculations or drawing-based comparisons. With LRTK, these processes can be largely automated. Overlaying the point cloud acquired by a smartphone with the design 3D model allows you to 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 measured point cloud to show areas exceeding allowable tolerances. This reduces the risk of discovering problems only after work completion and having to redo work.

Automatically measuring area and volume from point cloud data is another major advantage. Where it once took time to compute earthwork quantities from survey data, you can now scan terrain on a smartphone and instantly compute embankment volume or measure the area of an as-built surface. For example, during levee construction you can determine on site how many cubic meters of fill are required to reach design elevation and make rapid decisions.

These automation features greatly speed up the construction PDCA cycle. Since surveying, analysis, and visualization can all be completed with a single smartphone, you can make management decisions on the spot and move on to the next task. Creating as-built drawings and calculating quantities that used to take days can now be done in a short time, contributing to shorter schedules and cost savings. Moreover, manual transcription and calculation errors are reduced, enabling consistent digital-precision quality control. As a benefit of site DX, parts of the process that previously relied on craftsmen’s intuition and experience are replaced by data-driven, objective judgments, improving reproducibility and reliability of construction.

Efficiency Gains and Reduced Training Load from Managing Site Work with Just a Smartphone

That many surveying and construction management processes can be completed with just a smartphone thanks to LRTK leads to increased productivity on site. Tasks that previously required specialist survey staff to confirm control points or measure as-built conditions can now be performed by the construction-manager staff on the spot, reducing waiting times for external arrangements and coordination losses between departments. For instance, if you want to perform a final elevation check before concrete placement, you can pull out your smartphone and measure immediately. Since data is automatically shared to the cloud, time-consuming office tasks—like producing drawings or writing reports—are reduced. These accumulated efficiencies directly contribute to shorter schedules and cost savings, and in turn help drive DX across the site.

Using a smartphone, a general-purpose device, also lowers the barrier to skill acquisition. Intuitive AR displays make it easier for non-experts to understand differences between design and as-built, and device operation is completed with simple buttons in a smartphone app. Traditional surveying equipment required specialized knowledge and experience, and newcomers took a long time to become proficient. With LRTK, site staff who have received some training can handle the tool in a relatively short period. You do not have to understand complex surveying theory—following on-screen instructions yields accurate data—so newcomers and young staff can be made operational more easily. This is a considerable advantage in an industry facing workforce shortages.

Additionally, AR visuals smooth information sharing on site. Knowledge and cautions that previously lived only in veterans' heads can be made visible as AR markers and models for the whole team. Instructions that were difficult to convey via paper drawings become immediately clear when shown on screen. As a result, the time and effort required for training and information transfer are reduced, and rework due to miscommunication declines. Managing construction with a single smartphone is changing how knowledge is transferred on site, helping create an environment where everyone can use digital tools effectively.

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

Actual deployments of smartphone RTK and AR on site have reported the following outcomes:

• A civil engineering site case: Using an LRTK-equipped smartphone to perform reference-point surveys, scan as-built areas, and overlay and check the design model in AR resulted in a process that previously took several days with a total station, laser scanner, and PC analysis being completed the same day with a single smartphone. Eliminating time spent on instrument setup and post-processing allowed field work and verification to be completed on the same day, significantly shortening the schedule. Because the work could be completed by the construction management staff without calling a specialized survey team, manpower arrangement burdens were reduced and costs were cut.

• Another construction site case: During excavation, CAD data of the planned excavation area was loaded into the LRTK app and displayed in AR during operations. The machine operator moved the excavator along the virtual excavation guide shown on the smartphone screen and achieved the target excavation shape without temporary batter boards. As a result, not only were personnel requirements for stake setting reduced, but excavation errors were minimized and almost no rework was needed. AR-based work guidance thus provided labor savings and quality improvements.

• Infrastructure inspection case: For nighttime railway maintenance work, LRTK and AR were used to display replacement parts and cable routes as AR markers, helping workers accurately locate targets in the dark. This eliminated the time spent searching with flashlights and allowed all inspections and replacements to be completed within the limited work window as planned. There were no oversights or misidentifications, contributing to improved safety and work quality. Because CLAS-capable LRTK models maintain centimeter accuracy even in cellular dead zones such as tunnels and mountainous areas, they are effective for offline infrastructure inspections and disaster surveys.

These examples show that the effects of combining smartphone RTK and AR on site are being proven in practice, not just in theory. Reported benefits include improved safety, workforce reduction, efficiency gains, and error reduction—outcomes that are expected to drive further adoption across many sites.

Conclusion: Recommendations for Introducing Simple Surveying with LRTK

The fusion of network RTK and AR visualization is becoming a future standard for construction sites. Being able to handle surveying through construction management with a single smartphone offers a powerful solution to industry challenges such as labor shortages and knowledge transfer. Actively adopting the latest technologies beyond conventional wisdom is the key to improving productivity while ensuring safety and quality.

That said, terms like "high-precision positioning" and "AR" may sound complicated. However, with solutions like LRTK, you can easily start high-precision surveying without expert knowledge. The ability to introduce digital tools at the site level without large initial investments or long training periods is a major appeal. Once you try it, you will likely be surprised by the intuitive operation and visible results.

The construction industry is now undergoing major change through DX. As explained in this article, combining centimeter-level network RTK with intuitive AR visualization can dramatically streamline site workflows. If you have not yet adopted these technologies, consider starting simply with a smartphone and LRTK. Small first steps will let you experience the effects of site DX, and over time that will help strengthen your company's overall competitiveness. We encourage you to try the future-standard smartphone RTK and AR technologies on your own sites.

FAQ

What is network RTK?

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

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 the satellites without relying on cellular communications. The service covers most of Japan and is used as a method for high-precision positioning in environments where the Internet is unavailable, such as mountainous areas and remote islands. Some LRTK models support CLAS reception and are effective at out-of-coverage sites.

Are virtual models displayed in AR stable?

Yes. By using high-precision RTK position information, virtual models overlaid in AR remain very stable. Standard smartphone AR can drift slightly as the user moves, but because RTK places models based on absolute coordinates, they generally do not 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 is temporarily disturbed a small display error may occur; nonetheless, if the positioning is in a Fix solution state, positional accuracy is maintained at the centimeter level.

What should I do where satellite signals cannot be received?

RTK positioning relies on receiving GNSS satellite signals, so it cannot be used in places where satellites cannot be observed at all, such as deep indoors or deep inside tunnels. In such cases, you need to perform local positioning using known points obtained outdoors in advance, or use conventional optical surveying instruments (such as total stations) alongside RTK. If satellite visibility is only partially obstructed, you can maintain accuracy by increasing observation time to average measurements or by moving observation points to locations with better sightlines. In areas where cellular service is unavailable but satellite reception is possible—such as mountainous regions—Michibiki’s CLAS or local radio-based reference stations can be used to continue high-precision positioning. Higher-end LRTK models come equipped with short-range radio and CLAS reception features to support surveying in offline environments.