RTK GNSS Use Case: Dramatic Improvement in Civil Construction Site Work Efficiency with High-Precision Positioning

Table of Contents

• Introduction: The Importance of High-Precision Positioning on Construction Sites

• Challenges of Traditional Surveying Work

• What is RTK GNSS? Centimeter-level Accuracy (cm level accuracy (half-inch accuracy)) Achieved by Real-Time Corrections

• Benefits of Introducing RTK GNSS for Site Efficiency

• RTK GNSS Application Scenes (Surveying, Layout, As-built Management)

• Conclusion: Improving Productivity with High-Precision Positioning Technology

• FAQ

Introduction: The Importance of High-Precision Positioning on Construction Sites

In recent years, the construction industry has been swept by a wave of DX (digital transformation), making the digitization of worksites a major theme. To address chronic labor shortages, the aging of skilled workers, and the challenges of demanding, dangerous, and dirty work environments, the Ministry of Land, Infrastructure, Transport and Tourism has set a goal to increase construction site productivity by 20% by 2025 and is promoting the use of ICT technologies known as i-Construction. In line with this, introducing the latest technologies into surveying and construction management processes to improve work efficiency and safety has become an important issue.

In civil engineering works, information about “position” is indispensable in every process. Accurate coordinate positioning affects quality and efficiency in tasks such as current topographic surveys, layout of structures (staking) and batterboard installation, and post-construction as-built verification. However, traditional surveying methods required significant time and manpower for high-precision measurements, placing a heavy burden on covering entire sites. High-precision positioning technology using GNSS (Global Navigation Satellite Systems) has therefore attracted attention. This article explains how RTK GNSS centimeter-level positioning (cm level accuracy (half-inch accuracy)) dramatically streamlines site work, its mechanism, and use cases.

Challenges of Traditional Surveying Work

Traditional surveying on construction sites commonly used optical total stations and levels. These instruments can measure distances and elevation differences with high accuracy, but they require time-consuming setup and line-of-sight, and usually need two or more workers: one to operate the instrument and another to hold a prism or staff at the target point. Measuring many points across a wide site therefore consumed enormous time and effort. Surveying on steep mountain slopes or beside busy roads also carried risks of falls and secondary accidents, and transporting and setting up heavy equipment under harsh conditions was a major problem.

In addition, traditional methods often relied on manual recording and drawing of survey data, creating time lags in information sharing between the site and the office. Inefficient tasks such as taking figures from a field notebook and re-entering them into spreadsheet software were common, making real-time progress tracking and quality checks difficult. In short, conventional surveying faced issues of heavy manpower burden, time-consuming operations, safety risks, and delayed data utilization, and RTK GNSS high-precision positioning is expected as a new solution.

What is RTK GNSS? Centimeter-level Accuracy (cm level accuracy (half-inch accuracy)) Achieved by Real-Time Corrections

RTK GNSS (Real-Time Kinematic GNSS) is a high-precision positioning technology that corrects satellite positioning error sources in real time, enabling horizontal positioning errors of about ±1–2 cm (±0.4–0.8 in) and vertical errors of about ±3 cm (±1.2 in). Ordinary GNSS positioning, including GPS, can have errors of several meters due to atmospheric effects and satellite orbit errors. In the RTK method, both a reference station (base) with known accurate coordinates and a rover (mobile unit) simultaneously receive GNSS satellite signals, and the difference between their observations is used to correct errors. As a result, satellite-based positioning can achieve accuracy comparable to a total station.

Using RTK positioning allows surveying across wide sites based on a unified coordinate system originating from the reference station, reducing accuracy inconsistencies and cumulative errors between points. Even in cases where instruments previously had to be reset every few hundred meters, RTK GNSS enables continuous position measurement while moving. However, traditional RTK systems required either installing your own base station or having the rover receive correction data via the Internet (e.g., VRS = Virtual Reference Station service), and the usable range was limited to a radius of several km to about 20 km from the base station.

Recently, evolved forms of RTK such as network RTK and PPP-RTK have emerged. In Japan, a representative example is the CLAS (Centimeter-Level Augmentation Service) using the Quasi-Zenith Satellite System Michibiki, where a dedicated GNSS receiver can receive augmentation signals directly from satellites without a base station, enabling real-time centimeter-level positioning (cm level accuracy (half-inch accuracy)). These technological advances are making high-precision positioning increasingly accessible.

Benefits of Introducing RTK GNSS for Site Efficiency

Introducing RTK GNSS on site yields various efficiency improvements that were impossible with traditional methods. The main benefits are summarized below.

• Manpower Reduction and One-Person Operation: With a terminal equipped with a high-precision GNSS receiver, surveying and batterboard work that previously required two people can be completed by one person. If multiple workers each carry a GNSS terminal and survey in parallel, a wide area can be covered in a short time, making it possible to cope with labor shortages. Even without a licensed surveyor on site, construction managers or craftsmen can carry out necessary surveying and as-built checks themselves, reducing costs and scheduling coordination with external surveying firms.

• Dramatic Reduction in Work Time: RTK’s rapid positioning obtains coordinates of target points in a matter of seconds. Preparations like setting up heavy equipment or tripods and securing line-of-sight are unnecessary; simply move to the desired location, raise the antenna, and press a button for an immediate precise measurement. Tasks such as current surveys or staking that used to take half a day or more are greatly sped up, reducing machine operator waiting times and work interruptions, directly shortening construction schedules and boosting productivity.

• Improved Positioning Accuracy and Construction Quality: Centimeter-level accuracy (cm level accuracy (half-inch accuracy)) minimizes errors in pile-driving positions and finished elevations. Subtle deviations that previously relied on human sight or experience can be detected to within a few centimeters with RTK GNSS. Since survey results can be checked digitally on the spot, construction mistakes and measurement errors can be prevented in advance, reducing rework and preventing quality defects. In as-built management, immediate comparison with design values enables improved inspection pass rates.

• Data Sharing and Promotion of Site DX: Survey data obtained by RTK GNSS can be saved and shared digitally immediately. By linking tablets and cloud services, point cloud data and coordinate information measured on site can be shared with the office in real time, making progress visualization easy. The need to bring paper field books back and manually enter data is eliminated, and drawings and reports for reporting can be created on site. Combining GNSS with augmented reality (AR) enables overlaying design drawings or completion images on a smartphone screen for intuitive information sharing among stakeholders. These capabilities prevent communication loss and speed up consensus building.

• Improved Safety: A major advantage is reducing the need to enter hazardous areas for surveying and measurement. For example, reference point surveys beside expressways or slope inclination checks can be performed from a safe distance with GNSS, or sites can be assessed using drones. Workers no longer need to remain in dangerous locations for extended periods, reducing the risk of secondary accidents. Shorter surveying times also reduce the duration of work at height and around heavy machinery. Efficiency gains from DX thus directly contribute to improved safety management.

RTK GNSS Application Scenes (Surveying, Layout, As-built Management)

Let’s look at how site work specifically changes with the introduction of RTK GNSS in typical application scenes.

Streamlining Surveying Work: Rapid, Wide-Area Site Assessment by One Person

Traditionally, current surveys and as-built measurements relied on precise total station measurements requiring a skilled operator and an assistant. Obstacles such as buildings and trees between points required resetting instruments or adding relay points. With RTK GNSS, in principle one person can handle wide-area surveying.

Using network correction services like VRS allows the rover to perform positioning alone, minimizing the need to carry heavy equipment. By moving to the desired point, holding up a terminal with an antenna, and tapping a button, coordinates can be obtained in seconds, allowing efficient measurement of many points in a short time. For example, a site survey that used to take two people half a day can be completed by one person within a few hours using RTK GNSS. Furthermore, because all points are measured to the same reference, relative accuracy within the site is high, making data integration and drawing creation easier later.

Innovation in Layout and Batterboard Installation: Intuitive Positioning with AR

RTK GNSS also revolutionizes layout and batterboard installation for indicating road centerlines and structure positions. Traditionally, surveying teams calculated coordinates from drawings and marked positions on site with temporary stakes or chalk, relying on experience and intuition, which risked transmission errors.

With RTK GNSS, digital design data can be linked to real-world positions with high accuracy. For example, a dedicated app can display “virtual stakes” or “lines” at specified coordinates using AR on a smartphone, allowing workers to mark exact points on site while viewing the screen. Even non-experts can intuitively identify designated positions, reducing rework.

Machine operators can also view real-time deviations between their current position and the design line on an in-cab tablet, eliminating the need to dismount and wait for survey results and preventing interruptions. Integration of RTK GNSS with construction machinery advances the unification of surveying and construction, enabling more efficient operations.

Advanced As-built Management: Immediate Inspections and Quality Assurance

RTK GNSS is powerful for as-built management after structure completion. In an embankment project, for example, verifying specified elevations and slopes used to involve surveying teams measuring heights point by point after completion and then comparing them with design values.

With RTK GNSS, construction personnel can measure as-built conditions during finishing and compare them with design data on the spot. By overlaying measurements with the design model on a smartphone or tablet, deficits and excesses can be identified in real time, allowing immediate correction. As measurement data are already digitized, post-processing for as-built documentation is streamlined and inspection documents can be prepared quickly. RTK GNSS is shifting as-built management from post facto checks to continuous real-time quality control.

Conclusion: Improving Productivity with High-Precision Positioning Technology

As we have seen, centimeter-level high-precision positioning (cm level accuracy (half-inch accuracy)) provided by RTK GNSS is an innovative technology that streamlines various tasks at civil engineering construction sites while simultaneously improving safety and quality. One-person surveying and real-time as-built management, which were once unthinkable, are becoming possible, heralding a new site style for the DX era. The technological foundation of high-precision GNSS continues to evolve, and dedicated devices are becoming smaller and cheaper, bringing an era in which anyone can perform precise surveying with a smartphone.

Among these innovations, LRTK has emerged as a compact RTK GNSS receiver attachable to a smartphone, attracting attention as a solution that enables centimeter-level positioning even without specialized surveying knowledge. By attaching a device weighing only a few hundred grams to a smartphone and launching a dedicated app, initialization completes in a few tens of seconds and high-precision positioning begins. The simplicity of no complex settings and immediate usability on arrival at the site embodies the concept of “surveying anytime, anywhere, by anyone.”

Furthermore, because LRTK supports Japan’s CLAS augmentation signals, it can perform standalone positioning even in mountainous areas outside cellular coverage, and built-in batteries allow long operation times for practical on-site use. If you are considering achieving efficiency and manpower reduction at your site with RTK GNSS, actively adopting these latest technologies is recommended. By incorporating simple surveying with LRTK, civil construction productivity can dramatically improve with unprecedented speed and accuracy.

FAQ

Q: What equipment and preparations are required to use RTK GNSS? A: To perform RTK GNSS positioning, you need a GNSS receiver capable of centimeter-level positioning and correction information that the receiver accepts. Correction information can be provided by installing your own base station or by using reference point services provided over the Internet (e.g., VRS). Recently, Japan’s Michibiki (QZSS) CLAS signals allow correction reception and positioning with a standalone receiver. On site, the receiver is placed at the point to be measured (or held on a pole or tripod), and a controller device (smartphone or tablet) is used to obtain and record positioning data. Using dedicated RTK-enabled apps or software, reception of correction information and coordinate calculations are performed automatically, providing real-time high-precision position coordinates.

Q: What level of accuracy can be expected from RTK GNSS? How does it differ from ordinary GPS? A: RTK GNSS can achieve roughly 1–2 cm (0.4–0.8 in) horizontally and about 3 cm (1.2 in) vertically. Ordinary smartphone GPS or standalone positioning can produce errors of several meters, but RTK removes error factors through relative positioning with a reference station, enabling far more precise measurements. For example, locations that previously had errors approaching 10 m can be reduced to within a few centimeters with RTK. This is comparable to the precision of conventional optical total stations and is sufficient for position setting and as-built checks in civil engineering.

Q: Is GNSS surveying affected by weather and the environment? Can it be used indoors or in forests? A: GNSS positioning fundamentally relies on receiving signals from satellites overhead, so positioning is unstable where the antenna cannot see the sky. Rain or snow generally do not directly have a large impact on positioning accuracy, but in forests, tunnels, or near buildings satellite signals can be blocked or multipath (reflections) can cause errors, degrading accuracy. Even with RTK GNSS, it is ideal to use it in open areas. However, if positioning temporarily becomes unstable, it will automatically recover to high-precision positioning once satellites are reacquired. In tunnels, indoors, or other places where satellites cannot be received, GNSS cannot be used alone and must be combined with total stations, terrestrial laser scanners, or high-precision inertial navigation systems.

Q: Does introducing RTK GNSS at a site require expensive investment? A: Traditional survey-grade GNSS equipment often cost several million yen, making adoption difficult for small to medium sites. However, technological innovation and cost reductions have led to affordable, compact high-precision GNSS receivers. Products like LRTK that work with smartphones can be operated at much lower cost than purchasing dedicated large equipment. Reducing reliance on external surveyors can also lower total costs. Additionally, intuitive systems that do not require licensed surveyors reduce training costs and shorten the learning curve, making adoption easier.

Q: What is LRTK and how can it be used on site? A: LRTK is a positioning system consisting of a small RTK GNSS receiver and a smartphone app, transforming a smartphone into a centimeter-accurate surveying instrument. Specifically, a receiver device attached to the back of an iPhone or iPad and a dedicated surveying app (LRTK app) enable high-precision positioning, point cloud measurement, and AR display of design information. Because LRTK supports Japan’s CLAS augmentation signals, it can perform standalone high-precision positioning even at sites without cellular coverage. On site, the smartphone with the receiver can be mounted on a monopod or pole to measure ground points or used for walking-area surveys. Tasks that previously required specialized equipment can be performed easily with smartphone operations using LRTK, greatly contributing to labor and manpower savings in surveying. As functionality continues to expand, LRTK is expected to become one of the standard tools on construction sites.