What is RTK? The Role and Importance in Surveying Tasks

Basic Structure of RTK Positioning: In RTK-GNSS positioning, two receivers are used: a reference station (on the right) with a known position and a rover (on the left) whose position is to be determined. Both receivers simultaneously receive signals from the same satellite. By transmitting error correction data from the reference station to the rover, the rover calculates a highly precise position within a few centimeters.

With traditional standalone positioning, errors of several meters were common, but using RTK enables horizontal accuracy of 2–3 cm and vertical accuracy of 3–4 cm, making it extremely useful in surveying and construction management.

RTK is not only highly accurate but also provides real-time results, which is one of its major advantages.

As a result, RTK-based high-precision positioning has become the core of the construction process, especially with the promotion of ICT construction through the "i-Construction" initiative led by the Ministry of Land, Infrastructure, Transport and Tourism.

For example, RTK-GNSS is increasingly used in various areas of infrastructure construction and maintenance, including machine guidance for ICT construction machinery, as-built management, and setting reference points for drone surveying.

​

Benefits of Using RTK in Surveying
By introducing RTK, the productivity and accuracy of surveying sites are dramatically improved. Below are the main benefits of using RTK:

• Conducting Large-Scale Surveys in a Short Time: GNSS-RTK surveying allows for rapid surveying of large areas by a single person, compared to traditional total station (TS) methods. With the base station + rover setup, it significantly reduces the effort of maintaining line of sight and the need for frequent re-adjustments, thereby shortening the work time. In fact, GNSS surveying is known for its major strength: "the ability to conduct large-scale surveys in a short time with high precision."

• High-Precision Data Acquisition: RTK allows for the acquisition of position coordinates with an error of just a few centimeters, making it easy to ensure accuracy in terrain surveying and as-built management. Tasks that previously relied on skilled manual measurements for detailed work can now be performed with stable accuracy using RTK equipment. RTK-GNSS, which combines high-precision positioning with real-time capability, has become an indispensable technology for modern surveying.

• Labor Savings and Single-Person Operation: With just one RTK surveying device, a single person can perform the surveying. Unlike traditional TS surveying, where multiple people are needed to place reflection prisms, RTK allows one person to collect position coordinates simply by carrying the equipment and moving between points. This is a significant advantage in the construction industry, where labor shortages are a serious issue, contributing to labor savings and improved safety by reducing the need for personnel to enter hazardous areas.

• Direct Acquisition of World Geodetic System Coordinates: With RTK using GNSS, the observed values are directly obtained as coordinates in the World Geodetic System (e.g., JGD2011). This reduces reliance on local coordinates or known points, making centralized data management easier. The obtained coordinates also have high compatibility with GIS and design data, promoting their use in later stages and facilitating digital management (so-called construction DX).

 

As mentioned above, by utilizing RTK, surveying tasks are made more efficient and less labor-intensive, while accuracy is dramatically improved. As a result, this leads to faster project timelines and cost reductions, making it a foundational technology that supports the digitalization of construction sites.

​

Challenges in RTK Operations on Site
While RTK is extremely useful, there are several challenges when implementing it on-site. To maximize the benefits of its introduction, attention must be paid to the following points.

• Base Station Setup and Communication Security: In traditional RTK-GNSS surveying, a base station (fixed station) needs to be set up near the site, and communication with the rover station must occur via radio. Choosing the right location for the base station and setting up the equipment can be time-consuming. Additionally, obstacles between the base station and the rover can lead to unstable communication. As the distance from the base station increases, the positioning accuracy of the rover decreases, and in areas where the radio signals cannot reach, RTK positioning becomes unusable.

• Dependence on Network-Based RTK: Recently, network-based RTK (such as the VRS method) that distributes correction data from electronic reference points has become more widespread. However, this system relies on an internet connection, meaning it is difficult to use in mountainous areas or locations outside mobile network coverage. Additionally, the positioning accuracy is influenced by the quality of the communication carrier's network, and communication costs, including monthly service fees, are incurred.

• Impact of Multipath and Signal Obstruction: A common challenge for GNSS positioning is that in locations with poor sky visibility (such as under overpasses, beneath trees, or in urban canyons between buildings), errors due to signal reflection and obstruction (multipath) can increase significantly. In RTK, positioning cannot be initialized if fewer than four satellites are received, so it's essential to ensure open sky visibility and be cautious when moving during positioning. Additionally, during rain or snow, signal propagation may be affected, leading to degraded accuracy (Note: Environmental factors in GNSS surveying).

• Initial Costs and Operational Familiarity: The introduction of a complete GNSS-RTK surveying system requires a considerable initial investment. There are costs involved in acquiring high-precision RTK receivers, communication devices, and, in some cases, base station equipment. Furthermore, personnel training and gaining knowledge of positioning principles are essential for effective in-house operation. If operators are not familiar with equipment setup or troubleshooting, it can lead to unexpected time losses on-site.

​

As mentioned, dependence on the communication environment and challenges related to equipment and operations can become obstacles to the effective use of RTK. However, these can be fully overcome with proper planning, appropriate equipment selection, and the implementation of countermeasures.
In the next section, we will explore the key points for successfully operating RTK and the latest solutions available.

​

Key Points and Measures for Successful RTK Operation
To fully enjoy the benefits of RTK implementation, it is essential to address the challenges mentioned above while ensuring proper operation. Below are the key points for reliably utilizing RTK on-site.

• Differentiating Communication Methods: Select the optimal RTK method based on the site environment. In areas with good mobile communication, using network-based RTK can eliminate the need for base station setup. On the other hand, in remote areas such as mountainous regions without communication coverage, using a private base station combined with low-power wireless (digital radio) RTK is effective. Although it requires obtaining a radio station license and ensuring line-of-sight, stable positioning is possible without being affected by internet connectivity. By flexibly using VRS and local RTK for each site, continuous high-precision positioning can be achieved.

• Base Station Setup Considerations: When operating your own base station, it is essential to place it at a location with good visibility, preferably at a high point, to reduce the distance between the base and rover. When the distance is within 10 km, common error factors between both stations can be canceled out, improving accuracy. Additionally, using features like "automatic base station mode" to determine stable reference coordinates over long periods of continuous observation is important for enhancing base station positioning accuracy. Preparing spare batteries for the base station and ensuring there are no interference sources nearby are also essential preparations.

• Utilizing Latest Equipment and Technologies: Recent RTK-GNSS receivers have improved multi-GNSS and multi-frequency capabilities, expanding the ability to position even under obstructions. For example, using a receiver with tilt compensation allows for accurate coordinate acquisition even when the surveying pole cannot be kept vertical. Additionally, using the centimeter-level correction service (CLAS) provided by Japan's Quasi-Zenith Satellite System (Michibiki) enables high-precision correction data even without an internet connection. By introducing equipment with such advanced technologies, the reliability and convenience of RTK operations are greatly enhanced.

• Operational Rules and Training: To ensure stable operation on-site, share the standard procedures and precautions for RTK surveying within the company. For example, ensure "adequate satellite count at startup," "regular accuracy checks at known points," and "avoid placing obstacles between the base station and rover during positioning." Additionally, it is important for personnel to receive training from equipment manufacturers or experts to ensure they understand the principles of RTK and how to operate the equipment correctly. By reducing human error and maximizing the potential of the equipment, it is possible to prevent on-site issues before they arise.

​

By keeping these points in mind, RTK becomes a powerful tool on surveying sites. Furthermore, in recent years, new RTK solutions that address these challenges in a one-stop manner have emerged. In the next section, we will introduce one of these optimal solutions, LRTK.

​

RTK Utilization with LRTK
"LRTK" is gaining attention as a solution that solves the challenges of traditional RTK operations and allows anyone to easily use high-precision positioning. LRTK is the name of a digital positioning technology and device series, designed to maximize the benefits of RTK positioning by incorporating feedback from field users.

​

LRTK Phone: A super-compact RTK-GNSS receiver device that attaches to your smartphone. By simply attaching it to the back of an iPhone, the smartphone transforms into a centimeter-level precision surveying tool.

You can immediately perform positioning or marking on-site whenever needed, and the acquired data can be instantly shared via the cloud. Weighing approximately 125g and being small enough to fit in your pocket, it serves as a versatile surveying tool that can be easily carried and used whenever necessary.

LRTK series devices address common issues with communication environments, tilt, and setup challenges in field operations.

For example, the stationary "LRTK Pro2" integrates the antenna, battery, and radio into a single unit with a rugged design, ensuring stable operation even in harsh field environments. It can perform positioning using CLAS (Augmentation Signal from Michibiki) even without internet, enabling high-precision positioning in remote areas like mountainous regions or offshore, outside mobile network coverage.

Additionally, the device includes tilt compensation, allowing accurate coordinate acquisition even when the pole is tilted, making surveying in areas with many obstacles smoother.

LRTK also excels in software. Its intuitive operation through the dedicated app, along with the ability to automatically upload and share positioning data, facilitates seamless coordination between the field and the office.

By leveraging LRTK, an RTK solution, high-precision surveying becomes possible "for anyone, anywhere, and anytime." We invite you to experience the surveying digital transformation (DX) with the latest technology. We hope LRTK will help streamline and improve the accuracy of your surveying operations.