Common Misconceptions about RTK Surveying: The Real Story and the Mistakes

Table of Contents

• What is RTK surveying? Background on why centimeter-level accuracy draws attention

• Conditions required to achieve centimeter accuracy with RTK positioning

• Common misconceptions about RTK surveying and the real facts

• New developments in simplified RTK surveying: high-precision positioning with LRTK

• FAQ

What is RTK surveying? Background on why centimeter-level accuracy draws attention

In recent years, construction and civil engineering sites have shown a growing demand to minimize positioning errors as much as possible. Conventional GNSS-only positioning is convenient for obtaining current position, but it typically incurs errors on the order of several meters. A few meters of deviation is acceptable for checking your location on a map app, but when performing precise on-site layout staking (setting out) or as-built measurements, meter-level errors are unacceptable. For example, in road or bridge construction, large surveying errors can lead to misplacement or incorrect elevation of completed structures, degrading construction quality. High-precision positional information is also required when detecting minute displacements during infrastructure inspections.

This is where high-precision positioning technology known as RTK surveying attracts attention. RTK stands for *Real Time Kinematic*, and it refers to a method that can measure positions at centimeter-level accuracy by correcting GNSS errors in real time. Standard GNSS positioning typically has meter-level deviations caused by satellite signal errors, but RTK surveying uses two GNSS receivers—a base station and a rover—to perform relative positioning, cancel out error sources, and achieve accuracy that standalone positioning cannot provide. A base station (reference station) is a receiver placed at a location whose coordinates are known precisely; it calculates the error components in the received satellite signals at that location in real time. The rover is the receiver placed at the point to be surveyed; it receives correction information sent from the base station and applies it to its own position computations. In this way, the rover can compute its position relative to the base station in real time, enabling positioning with horizontal and vertical errors within a few centimeters.

Such centimeter-level positioning accuracy is highly valued for improving productivity on worksites, driven in Japan by initiatives like i-Construction. By using RTK surveying, structures can be placed exactly according to design drawings, and as-built measurements can be taken precisely to support quality control. Centimeter-accurate positioning also dramatically improves data reliability and operational efficiency for drone photogrammetry, machine guidance for heavy equipment, and positioning control of autonomous construction machinery. Consequently, RTK technology is being adopted across a wide range of sites, from major general contractors to small and medium-sized construction firms, surveying companies, and infrastructure maintenance managers.

Conditions required to achieve centimeter accuracy with RTK positioning

To obtain the high accuracy of "errors of a few centimeters" with RTK surveying, several important conditions must be met. RTK is a powerful technology, but it is not magic that guarantees 1 cm accuracy simply by using it; appropriate environment and operation are required for it to perform. Let’s look at the main points in order.

• Correction information from the base station: An accurately positioned base station is essential for RTK. The base station calculates the error components from its GNSS observation data and transmits that correction information to the rover in real time. Thanks to these corrections, the rover can cancel out errors that it cannot correct on its own and compute a high-accuracy position. Recently, public continuously operating reference stations (CORS) maintained by the Geospatial Information Authority of Japan and commercial GNSS correction services have become widely available, so it is common to obtain correction information without setting up your own base station. In any case, receiving accurate correction data in real time is a prerequisite for centimeter-level accuracy.

• Distance to the base station: The closer the base station (or virtual reference point) is to the rover, the more similar the error sources common to both stations (ionospheric and tropospheric delays, satellite orbit and clock errors, etc.) will be, leading to higher accuracy. Generally, if the base station is within several km, maintaining centimeter-level accuracy with RTK is easier. Conversely, as distance increases, residual errors that cannot be fully corrected grow, and positioning accuracy gradually degrades (roughly speaking, error increases by a few millimeters per 1 km of distance). Therefore, for high-precision surveying it is effective to either install a dedicated base station near the survey area or use a network RTK service based on a nationwide CORS network.

• Satellite visibility (positioning environment): To achieve centimeter accuracy with RTK, it is also important to perform positioning in an environment where GNSS signals can be received stably from the satellites. In open areas with a clear sky where a sufficient number of satellites can be observed, dense observation data are obtained and the RTK solution—especially the high-precision fixed solution—stably becomes available. In contrast, in urban areas surrounded by high-rise buildings or in heavily wooded mountainous areas, satellite visibility decreases due to obstructions, which can reduce RTK accuracy and make the solution unstable. In particular, environments with signal reflections from buildings or terrain—so-called multipath—can produce large errors and make accurate positioning difficult. To obtain centimeter accuracy, it is advisable to measure in as open a sky as possible or to choose time windows with favorable satellite geometry, among other measures.

• GNSS receiver performance: The performance of the GNSS receiver used also affects accuracy. High-precision RTK positioning requires receivers capable of tracking the satellite signal at the carrier-phase level, enabling handling of very precise observations. Receivers that support multi-GNSS and multi-frequency operation are advantageous. Being able to use multiple satellite constellations (GPS, GLONASS, Galileo, and Japan’s QZSS “Michibiki,” etc.) increases the number of satellites visible in the sky and improves positioning stability. Using multiple frequency bands such as L1/L2 helps remove ionospheric errors and shortens the convergence time to obtain an initial fixed solution. Recently, low-cost multi-band RTK-GNSS modules have appeared, making high-precision positioning easier to achieve than before.

If these conditions are met, RTK can theoretically realize astonishing horizontal and vertical accuracy within a few centimeters. However, these are "ideal conditions," and real-world survey sites may see accuracy vary depending on the environment and operation. The next chapter discusses common misconceptions about RTK surveying encountered in the field and the real story behind each.

Common misconceptions about RTK surveying and the real facts

RTK is an excellent technology that can achieve centimeter-level positioning if operated correctly. However, without sufficiently understanding its mechanism and prerequisites, users may harbor incorrect expectations or misuse it in the field. Here we address representative and common misconceptions about RTK surveying and clarify the correct understanding for each.

Misconception 1: "If you use RTK, you will always measure within 1 cm error"

Some expect that introducing RTK will keep positioning errors under 1 cm in any situation. In reality, RTK accuracy is greatly influenced by the surrounding positioning environment. As mentioned earlier, in environments where satellite reception is poor, RTK may not achieve a fixed solution, and temporary errors on the order of 10 cm can occur. In urban areas with tall buildings or within forests, you can typically maintain a few centimeters of horizontal and vertical accuracy on average, but under poor conditions spikes of more than 10 cm have been observed. Rather than blindly believing "RTK always equals 1 cm accuracy," it is important to understand correctly that RTK is "a technology that yields a few centimeters in good environments and at worst a few tens of centimeters." In other words, RTK is a means to drastically reduce errors, but depending on real-world conditions some upward deviation of errors may occur—keep this in mind during operation.

Misconception 2: "Centimeter accuracy means the measured coordinates are globally accurate as well"

Hearing "centimeter-level accuracy" may lead people to assume that the obtained coordinates are also globally accurate to within a few centimeters, but caution is needed. The coordinates obtained by RTK primarily indicate relative accuracy with respect to the base station at the centimeter level, and this presumes the base station’s position is known accurately. If the coordinates assigned to the base station contain errors or offsets, the coordinates measured by the rover will be shifted by the same amount. For example, if a temporary base station is set up on site with an actual position several meters off and RTK surveying is carried out using it, relative distances within the site may be measured with high precision, but overlaying the obtained coordinates on public coordinate systems may show meter-level shifts. Remember that centimeter accuracy does not necessarily equal absolute accuracy; it means high relative accuracy tied to the reference point.

Using Geospatial Information Authority of Japan CORS or network RTK services (VRS, etc.) provided by carriers offers reassurance here: those base-station networks are rigorously calibrated to public coordinate systems, so positioning results derived from them also have high absolute accuracy in global coordinate systems. If you set up a local temporary base station on site, you should adjust the base station coordinates using known control points beforehand or perform coordinate transformation after surveying.

Misconception 3: "RTK surveying requires very expensive and specialized surveying equipment"

Many imagine that RTK requires dedicated high-precision surveying gear and that the initial investment is huge. Indeed, until fairly recently, a complete set of RTK-capable GNSS receivers and base station equipment could cost several million yen, and such gear was not something everyone could readily carry onto a site. The devices were typically large pole-type or fixed station units with integrated antennas and receivers, making transport and setup laborious. In mountainous areas especially, heavy base stations had to be mounted on tripods and rovers placed on long poles, creating logistical hurdles.

However, recent technological advances and wider adoption have driven miniaturization and cost reductions. Palm-sized GNSS receivers and smartphone-compatible devices that enable centimeter-level positioning have begun to appear. This shift brings high-precision positioning—previously the domain of skilled surveyors—within reach of many field practitioners.

Moreover, the spread of network RTK (receiving corrections via the Internet) means that many sites no longer need to carry expensive radio units or base stations; as long as the rover can connect to the Internet, it can obtain correction data from a regional reference network via a smartphone. In Japan, the QZSS “Michibiki” system also provides CLAS (Centimeter-Level Augmentation Service), so in areas without cellular coverage, receivers can get augmentation signals directly from satellites to perform high-precision positioning. In short, modern RTK surveying no longer necessarily requires large-scale equipment and can be realized with relatively simple setups.

Misconception 4: "The latest smartphones can achieve centimeter accuracy on their own"

Recent smartphones include high-performance GNSS chips and are often advertised as "dual-frequency compatible" or "supporting augmentation," which might lead some to think that a smartphone alone can achieve centimeter-level accuracy without dedicated GNSS gear. However, at present it is extremely difficult for a smartphone alone to produce RTK-level 1–2 cm accuracy.

One reason is antenna performance. The small internal antennas in smartphones suffer more noise and attenuation, making it hard to obtain a stable fixed solution. Also, the augmentation information a smartphone can receive alone is limited, typically improving accuracy only to the order of several tens of centimeters (as with SBAS or high-sensitivity standalone multi-GNSS positioning). To obtain centimeter-level accuracy in real time, a dedicated RTK-capable receiver and appropriate correction information remain necessary.

That said, easy-to-use RTK devices that work in conjunction with smartphones have appeared in recent years. By leveraging the smartphone’s display and communication and combining it with a high-performance GNSS receiver, it is now possible to achieve accuracy comparable to traditional fixed receivers. A representative example of this trend is the LRTK series of devices.

New developments in simplified RTK surveying: high-precision positioning with LRTK

The barriers to using RTK’s centimeter accuracy on site have steadily lowered, and one leading solution is LRTK. LRTK is an ultra-compact RTK-GNSS receiver series developed by Reflexia Co., Ltd., which, when paired with a smartphone or tablet, realizes a "palm-sized surveying instrument."

For example, the flagship model "LRTK Phone" is a compact device that fits in your pocket—weighing approximately 165 g and only about 1 cm (0.4 in) thick—while supporting GPS, GLONASS, Galileo, Michibiki (QZSS), and other multi-GNSS, and importantly offering three-frequency (L1/L2/L5) support. Attach this device to an iPhone or iPad and launch the dedicated LRTK app, and the smartphone instantly becomes a centimeter-accuracy surveying instrument.

The strengths of the LRTK series are not limited to hardware performance. Designed for field usability, positioning data are transmitted to the smartphone in real time via Bluetooth. Acquired coordinate data can be uploaded to the cloud-based "LRTK Cloud" with a single tap, enabling instant data sharing with office staff. Remote collaborators can check the latest survey results, and cloud tools make it easy to calculate distances and areas between measured points, facilitating smooth collaboration.

LRTK supports not only network RTK (internet-based corrections such as Ntrip) but also Japan’s QZSS CLAS, the satellite-based centimeter augmentation service. Thus, in mountainous areas without cellular coverage, LRTK can receive high-precision augmentation signals directly from satellites and maintain centimeter-level positioning. Traditionally, high-precision positioning has been considered dependent on communications environment, but LRTK overturns this notion and enables stable RTK surveying almost anywhere—an important advantage.

By using LRTK, an individual can easily achieve centimeter-level positioning alone. There is no need to carry heavy tripods or fixed receivers; survey work can be completed with only a smartphone and a pocket-sized device. Acquired data are automatically tagged with coordinates such as latitude, longitude, and elevation, making it easy to compare with design drawings or GSI maps later. Photos, notes, and point cloud data can be linked to positioning results and managed centrally, streamlining report preparation and handover to subsequent processes.

Simplified surveying with LRTK is already permeating the field. Designed with the vision of a "one-device-per-person universal surveying instrument," this system’s ease of use and reasonable pricing have created a quiet boom at many sites. If you have not yet tried high-precision GNSS positioning, consider introducing LRTK. Once you experience the labor- and time-saving benefits, you may never go back to older methods. The "RTK surveying revolution starting with your smartphone" will continue to expand possibilities on job sites.

FAQ

Q. Can RTK surveying really achieve about 1 cm accuracy? A. Yes—if conditions are met, high-precision positioning with horizontal errors of approximately 1–3 cm (0.4–1.2 in) and vertical errors of about 3–6 cm (1.2–2.4 in) is possible. However, this assumes an open environment with good satellite visibility. In urban canyons or forests, temporary errors of more than 10 cm can occur. The important point is to understand that RTK is far more accurate than conventional GPS, but environmental factors can still introduce some error.

Q. Can RTK positioning be done without preparing a base station? A. Yes. Nationwide, the Geospatial Information Authority of Japan maintains CORS stations, and network RTK correction services (VRS, etc.) are available. If the rover can receive correction data via the Internet, RTK positioning is possible without setting up your own base station. In Japan, the QZSS Michibiki CLAS signal can also be used to receive satellite-based augmentation directly, enabling centimeter accuracy even in areas far from base stations or without cellular coverage.

Q. What is the difference between RTK and DGPS (Differential GPS)? A. DGPS is similar to RTK in that it receives corrections from a base station, but they differ in methodology and accuracy. DGPS primarily corrects code-based positioning errors and typically yields accuracies on the order of several tens of centimeters to 1 meter. RTK uses carrier-phase measurements to reduce errors to the centimeter level. RTK achieves stable high precision by obtaining a fixed solution, whereas DGPS mainly suppresses drifting errors and is less suitable for applications requiring long-term stable high-precision positioning.

Q. Can someone without surveying experience operate LRTK? A. Yes. LRTK is designed to minimize specialized operations; connect it to a smartphone, launch the app, and follow the guided steps to begin positioning. Basic operations such as observing and saving points are intuitive with button taps, and obtained data are automatically plotted on a map, making it easy to understand. You don’t need to manage complex settings or calculations as with traditional surveying instruments. Still, understanding RTK principles and precautions (e.g., the importance of satellite visibility) will help ensure consistently high accuracy.

Q. What advantages does LRTK have compared to conventional high-precision GNSS equipment? A. The greatest advantages are portability and ease of use. LRTK fits in your pocket, greatly reducing the burden of carrying equipment around the site. Its smartphone integration enables real-time cloud data sharing and immediate on-site result verification. Regarding accuracy, experiments have confirmed positioning within a range of several mm to several cm, comparable to conventional GNSS receivers that used to cost several million yen. Furthermore, reception of Michibiki’s CLAS signal allows positioning to continue even outside cellular coverage, making LRTK effective for surveying in remote mountainous areas. Overall, LRTK brings a new surveying style to the field: "high-end-equipment-level accuracy with smartphone-level usability."