Table of Contents

• What is RTK?

• Differences from GPS positioning

• Benefits of RTK and application areas

• Reasons RTK use is increasing on U.S. construction sites

• Simple surveying with LRTK

• FAQ

In recent years, the use of GNSS (satellite positioning) technology has rapidly expanded in construction and surveying fields. Among these, RTK (Real Time Kinematic) has attracted attention as a revolutionary method that enables centimeter-level high-precision positioning in real time. Standalone GPS positioning used to produce errors of several meters, but RTK can reduce those errors to a few centimeters, dramatically improving the accuracy and efficiency of surveying and construction management.

In fact, RTK technology is gradually being adopted on construction sites in the United States. Why is RTK usage increasing in the U.S. now? This article explains from the basics of what RTK is, the differences from GPS, and the benefits RTK brings, to the reasons for its growing adoption in the U.S., in an easy-to-understand way from the ground up. At the end of the article, we also introduce a simple surveying solution using RTK called LRTK.

What is RTK?

RTK (Real Time Kinematic) is a type of high-precision positioning technology that uses GNSS (Global Navigation Satellite Systems). It operates two GNSS receivers simultaneously—a base station (reference point) and a rover (mobile unit)—and achieves centimeter-level positioning by sending the position error measured at the base station to the rover in real time to apply corrections. In plain terms, a single GPS device alone can be off by several meters, but by installing another reference unit and applying its corrections, the offset is canceled out and an accurate position can be determined.

RTK cancels error factors contained in satellite signals (such as satellite orbit errors, clock errors, and atmospheric effects) through differencing. For example, because the base station knows its exact position, it can calculate the error from the position obtained by satellite positioning. By sending that error information to the rover and applying it, the rover can determine its position with high precision. Performing this process in real time (immediately at each positioning epoch) is a defining feature of RTK. As a result, extremely precise positioning on the order of a few centimeters horizontally/planimetrically and a few to less than ten centimeters vertically becomes possible.

Put another way, RTK is a GPS technology that provides high-precision coordinates on-site. Traditionally, high-precision surveying required optical total stations or long-duration static GNSS observations with post-processing. With RTK, however, if you have dedicated equipment and a communication environment, you can obtain positioning results immediately on site. RTK, which corrects errors in real time, can be called a GNSS positioning method for obtaining high precision immediately.

Differences from GPS positioning

So what exactly differs between ordinary GPS positioning and RTK? The major differences are the “positioning error” and the “positioning method.”

• Difference in positioning accuracy: The accuracy of general standalone GPS positioning is said to have errors of about 5–10 m (16.4–32.8 ft). In contrast, RTK positioning reduces errors to about 1–3 cm (0.4–1.2 in) horizontally. Vertical accuracy in standalone GPS is generally large and impractical, but RTK can determine height with an accuracy of about 3–6 cm (1.2–2.4 in). In other words, positional offsets are orders of magnitude smaller, providing accuracy suitable for surveying and construction that require near-millimeter-level control.

• Difference in positioning method: Standalone GPS determines position from satellites using only one receiver (the rover), whereas RTK uses at least two receivers. One receiver is installed at a known location as the base station, and the other—called the rover—moves while positioning. The base station computes error information and transmits it to the rover by communication, where the rover applies corrections to its own position to achieve high accuracy. Because of this, RTK requires data communication between the base station and rover (via radio or the Internet), which is not necessary for ordinary GPS positioning.

• Difference in operation: Standalone GPS positioning is easy—you can get a position simply by putting a receiver where the sky is visible—but RTK requires prior setup of the base station and communication. However, network RTK services, which provide correction data over the Internet from established GNSS base station networks, have become widespread. Using a network RTK service allows a rover receiver to receive real-time corrections without deploying your own base station, eliminating that setup effort.

As described above, RTK is distinct from ordinary GPS positioning in that it “measures simultaneously at two points to cancel errors, achieving ultra-high precision” and therefore “requires communication and a base station.” Not only is the achievable accuracy entirely different, but RTK also greatly outperforms traditional GPS in obtaining vertical data and providing immediacy.

Benefits of RTK and application areas

Introducing RTK technology brings various benefits to surveying and construction sites. Here are the main advantages of RTK and its application areas.

• High-precision surveying: The greatest benefit is the dramatic improvement in positioning accuracy. RTK reduces traditional meter-level surveying errors to centimeter-level, allowing immediate acquisition of precision data that meets millimeter-level requirements for tasks such as verifying installation positions of structures and managing as-built conditions. Having high-precision coordinates on site enables subsequent design and construction processes to proceed with confidence, preventing waste from rework.

• Improved work efficiency and immediacy: Because RTK provides real-time results, surveying work becomes much more efficient. For example, the traditional workflow of “survey on site → return to the office for calculations and drawing” introduces time lags, but RTK lets you confirm necessary coordinates immediately on site. Even for large-area topographic surveys, once a base station is set up and satellites are available, RTK can be used even in places with poor line of sight, reducing the frequent repositioning and line-of-sight issues associated with total stations. Time savings and immediate feedback from RTK significantly accelerate construction management.

• Labor and personnel reduction: RTK contributes to workforce efficiency. High-precision surveying often implies the need for highly skilled surveyors, but with RTK equipment, most people can perform surveying tasks after relatively short training. Tasks that previously required two-person teams, such as establishing control points or setting batter boards, can often be done by one person with RTK. As shortages of skilled surveyors worsen, RTK is gaining attention as a solution that enables small crews to maintain accuracy.

• Expanding application areas: RTK-GNSS is being used across a wide range of civil engineering and construction scenarios. For example, base point setup and as-built checks in roadworks and land development commonly use RTK receivers. Combining drone photogrammetry with RTK reduces the number of required ground control points while producing high-precision terrain models. In the growing field of ICT construction machinery (smart machines), RTK-capable GNSS antennas mounted on bulldozers and excavators enable machine guidance that automatically controls blade positions according to design surfaces. Precise position information from RTK enables automated control of machinery and construction automation, dramatically improving productivity on large-scale sites. Thus, RTK is becoming an indispensable foundational technology not only for surveying but also for DX (digital transformation) in construction.

Reasons RTK use is increasing on U.S. construction sites

While RTK’s advantages are being recognized worldwide, there are several reasons why adoption is increasing particularly on U.S. construction sites. The main reasons for the spread of RTK in the U.S. are summarized below.

• Easing severe labor shortages: The U.S. construction industry also faces labor shortages, particularly a lack of skilled surveyors. RTK allows limited personnel to efficiently conduct extensive surveying and as-built checks, making it an accepted measure to mitigate labor shortages. Even inexperienced workers can perform high-precision surveying after becoming familiar with the equipment, so RTK is gaining attention as a way to overcome constraints on human resources.

• Demand for productivity gains and cost reduction: Given the vast land area of the U.S., project scales tend to be large. There is a strong need to increase surveying and construction productivity and reduce wasteful rework. If RTK provides on-site survey results and suppresses errors, rework to correct positional mistakes later can be avoided. This leads to shorter schedules and cost reductions, so RTK’s cost-effectiveness is highly valued.

• Spread of machine guidance: Adoption of automated control and guidance technologies for heavy equipment has progressed more in the U.S. than in Japan, and using GNSS receivers on bulldozers and graders is becoming common. Accurate position control of these smart machines requires RTK-level GNSS. National promotion of intelligent construction and the adoption of RTK-equipped machine control for quality management in infrastructure works are increasing. RTK contributes to reducing operator workload and standardizing quality, which accelerates its adoption on sites.

• Lower cost and easier use of RTK technology: The cost of RTK-GNSS equipment has fallen in recent years, and miniaturization and simplification of technology have supported wider adoption. RTK-capable survey instruments used to be extremely expensive and often required specialist contractors, but today there are relatively affordable receivers and subscription services, making them accessible to small and midsize construction firms. For example, small RTK receivers that pair with smartphones and monthly subscription correction services have emerged, creating an environment where RTK can be used more cheaply and conveniently, which has driven increased use in the U.S.

• Suitability for large site environments: U.S. construction sites often involve large areas and open terrain, where RTK-GNSS is particularly effective. For earthworks on wide flat sites or long road projects, GNSS positioning tends to be stable under open skies, whereas maintaining line of sight and frequent repositioning with a total station is burdensome. RTK can position over long distances as long as satellite signals reach, so the larger the site, the greater the benefit of RTK. Additionally, national and private CORS (Continuously Operating Reference Station) networks are well-developed across the U.S., making it easier to obtain correction data via the Internet and promoting adoption at the site level.

For these reasons, RTK’s usefulness is widely recognized on U.S. construction sites and adoption is accelerating. RTK technology, which enables high-precision and efficient construction, is becoming one of the standard tools in the U.S. construction industry. Japan’s initiatives such as i-Construction led by the Ministry of Land, Infrastructure, Transport and Tourism promote ICT construction, and U.S. examples can be seen as leading models.

Simple surveying with LRTK

You can see how RTK can greatly improve surveying and construction efficiency. However, when considering introducing and operating RTK equipment in-house, some may worry, “Do I need expensive dedicated equipment?” or “Will it be difficult to use?” That’s where LRTK, a solution that makes high-precision surveying easy, comes in.

LRTK is our high-precision RTK positioning system designed so anyone on site can easily perform centimeter-level surveying. It is used in combination with a dedicated compact GNSS receiver (the LRTK unit) and a smartphone, enabling one-touch acquisition of absolute coordinates that standalone positioning cannot provide. For example, attaching the LRTK unit to the supplied monopod allows one person to easily measure point positions. Antenna height (the height at which the device is mounted) corrections are automatically calculated in the smartphone app, so accurate ground-surface coordinates can be recorded without specialized knowledge.

Although LRTK performs advanced GNSS correction processing internally, users need not handle complex settings. The LRTK unit, acting as the rover, has built-in mobile communication and automatically retrieves necessary correction data such as national geodetic control point data. Therefore, there is no need to set up your own base station on site—just take the unit and your smartphone to the site and you can start centimeter-level positioning immediately. The device has a built-in battery and is highly portable, fitting in a pouch so it won’t get in the way even in confined spaces.

Accuracy is comparable to professional high-end GNSS: LRTK achieves horizontal errors of about ±1–2 cm (±0.4–0.8 in) and vertical errors of about ±3 cm (±1.2 in) under favorable conditions. It also has a function to average multiple quick measurements; for example, averaging 60 measurements at the same point can achieve an astonishing accuracy of about 8 mm (0.31 in). Despite this level of precision, operation is completed simply by pressing a button in the smartphone app.

LRTK aims to make “difficult RTK surveying easy and safe for anyone.” In addition to high-precision point surveying, optional functions enable acquisition of wide-area 3D point cloud data with absolute coordinates, making it a next-generation surveying instrument. RTK technology is no longer limited to specialists—an era in which anyone on site can handle it is approaching.

If you are thinking “I’d like to introduce RTK at our sites” or “I want to improve surveying efficiency,” please consider using LRTK. With LRTK, even beginners can perform high-precision positioning after a short lesson. As democratization of high-precision positioning advances, LRTK will bring new possibilities to surveying and construction sites.

FAQ

Q. What is RTK? A. RTK stands for Real Time Kinematic. It is a technique that measures centimeter-level high-precision positions by correcting satellite positioning errors in real time. One receiver is fixed as a base station at a reference point, and the observation data difference between it and a mobile rover is used to cancel errors and achieve high-precision positioning.

Q. What is the difference between GPS positioning and RTK positioning? A. General standalone GPS positioning determines position with a single receiver and typically has errors of about 5–10 m (16.4–32.8 ft). Vertical accuracy is also poor, so elevation data are not very precise. RTK positioning corrects errors via communication with a base station, enabling horizontal accuracy of about 1–2 cm (0.4–0.8 in) and vertical accuracy of a few centimeters. In short, the accuracy is orders of magnitude better, and RTK requires a base station plus a communication link.

Q. What is needed for RTK positioning? A. RTK positioning basically requires a GNSS receiver for the base station, a GNSS receiver for the rover, and a means of communication between them. The base station is installed at a known coordinate, and correction data are sent to the rover via radio (such as low-power radio or UHF) or Internet. Network RTK services that use public or private control point networks have also become common; in that case, the rover needs a mobile data connection (such as smartphone tethering or an internal SIM in the receiver) to connect to a correction data distribution service. In any case, note that RTK operation requires reference station equipment and a communication environment in addition to standard GPS equipment.

Q. Can RTK positioning be used in any environment? A. RTK-GNSS surveying is most effective in locations with an open view of the sky. It cannot be used in environments where satellite signals cannot be received (urban canyons between buildings, tunnels, dense forests, etc.). Accuracy can also be degraded under strong ionospheric or tropospheric disturbances. Moreover, if communication with the base station is lost, corrections cannot be received and accuracy will fall, so network RTK can be difficult in mountain areas without coverage. RTK has environments where it is weak, so consider changing measurement points as needed or temporarily supplementing with other methods such as total stations.

Q. Can I do RTK positioning with a smartphone? A. A standard smartphone’s built-in GPS cannot achieve RTK-level accuracy, but pairing it with an external RTK-capable receiver makes centimeter-level positioning possible on a smartphone. For example, our LRTK Phone is an RTK positioning system that links with smartphones; connect the dedicated unit to your phone and launch the app to obtain high-precision position data on the smartphone. Bluetooth-connected compact RTK receivers from other manufacturers are also appearing, and using smartphones or tablets to perform RTK surveying is becoming more common. We are entering an era where smartphones can be used as site tools while benefiting from high-precision positioning.