What is noRTK? A thorough explanation of the differences and advantages compared to conventional RTK

Table of contents

• What is noRTK?

• What is conventional RTK?

• Differences between noRTK and conventional RTK

• Advantages of noRTK

• What is simple surveying with LRTK?

• FAQ

In infrastructure construction and surveying sites, even a positional deviation of a few centimeters can greatly affect quality and safety. For that reason, RTK positioning (Real Time Kinematic), which corrects GNSS positioning errors in real time to achieve high accuracy, is indispensable. The goal of high-precision RTK positioning is to obtain the centimeter-class "Fix solution" (cm level accuracy (half-inch accuracy)). However, in the field, many have experienced that Fix is hard to obtain and the system remains in a Float solution, or that corrections do not apply and the receiver remains in a "noRTK (Single) state." For construction site operators and managers considering surveying equipment, it is crucial to correctly understand what "noRTK" means and to grasp the differences and characteristics of each RTK method. This article thoroughly explains the meaning of noRTK, how it differs from conventional RTK methods, and its advantages. At the end of the article, we also introduce our LRTK simple surveying solution as a way to solve these problems and easily achieve high-precision positioning.

What is noRTK?

As the name implies, noRTK refers to a state that is "not RTK." Specifically, in GNSS positioning it means single positioning (Single solution) with no corrections from a base station applied at all. Single positioning without corrections typically results in errors of several meters to about 10 m (32.8 ft). Some receivers may display status messages such as "no RTK" or "DGPS invalid," which all indicate that base station corrections are not being applied. Naturally, the high-precision corrections that are the advantage of RTK are not in effect, so this mode cannot be used for tasks that require cm level accuracy (half-inch accuracy).

What is conventional RTK?

RTK (Real Time Kinematic) is a high-precision positioning method that uses two GNSS receivers—the base station (reference station) and the rover (mobile station)—and corrects positioning errors in real time by using the difference between satellite signals received simultaneously by both. The base station is installed at a known coordinate measured accurately in advance and calculates error information from the discrepancy between its known position and the satellite data it receives. It then transmits that correction data to the rover via radio or internet, and the rover applies the corrections to reduce autonomous positioning errors of several meters down to centimeter-level accuracy.

In conventional RTK surveying, it is common to set up a base station near the work site (ideally within a few kilometers) and distribute correction information using low-power radio, etc. The shorter the distance (baseline) between the base and rover, the more common error sources (satellite orbit errors, ionospheric and tropospheric delays, etc.) cancel out between the two stations, yielding higher accuracy. With proper operation, horizontal accuracy of about 1–2 cm (0.4–0.8 in) can be achieved, providing positioning accuracy far superior to standalone positioning.

Recently, network RTK services using multiple Continuously Operating Reference Station networks (VRS methods, etc.) have also become widespread. Users can obtain correction data from virtual reference points via the internet without installing a base station and perform RTK surveying with just a single rover. With network RTK, centimeter-level positioning is possible anywhere in Japan within communication coverage. However, using network RTK requires a communication environment (cellular network, etc.) and often entails paid service contracts.

RTK technology is used not only in surveying instruments but also in airborne surveying with drones, machine guidance for construction equipment, and position control for autonomous vehicles—various fields that require precise positioning.

Differences between noRTK and conventional RTK

As described above, the positioning mechanisms of noRTK and RTK differ greatly, so the obtainable accuracy and operational methods also differ. The main differences are summarized below.

• Measurement accuracy: noRTK (single positioning) results in large position errors of several meters or more (± several meters to about 10 m (±32.8 ft)). In contrast, RTK reduces errors to a few centimeters (within ± a few cm) through corrections, yielding a dramatic difference in positioning accuracy.

• Presence of correction data and infrastructure: noRTK does not require correction data from a base station and can operate with a single GNSS receiver. RTK positioning, however, requires a base station or external correction service and a means to transmit that data (radio or internet connection).

• Operational effort and cost: noRTK can be used without special setup or additional equipment investment, while operating RTK requires preparing base station equipment and configuring communication environments. Using commercial network RTK services generally incurs usage fees. Advanced tuning and initial setup are also required, so RTK operation demands a certain level of expertise and experience.

• Range and constraints: single positioning works anywhere in the world as long as satellites can be received, while RTK is constrained by the distance to the base station and being within communication coverage. Accuracy degrades if the base station is too far away, and network RTK cannot be used outside communication coverage. In areas with poor satellite reception, RTK may fail to achieve a Fix and fall back to Float or noRTK, whereas noRTK will always provide a position (albeit with lower accuracy).

• Time to acquire a solution: noRTK provides a position immediately after the receiver is powered on. RTK requires a certain initial convergence time to obtain a Fix, which can take from tens of seconds to several minutes depending on conditions. Once a Fix is obtained, however, high-precision positioning is maintained in real time.

As the above shows, RTK offers high precision but involves operational effort and constraints. On the other hand, noRTK has advantages due to its simplicity. Next, let’s look at the main benefits of noRTK.

Advantages of noRTK

• Ease of use: Positioning is possible simply by powering on a single GNSS receiver. There is no need to set up a base station or perform complicated initial configuration, so anyone can start using it immediately.

• Low cost: Standalone positioning does not require additional base station equipment or paid correction service contracts, so it avoids extra costs.

• No communication required and usable anywhere: Because it does not require a communications infrastructure to receive correction data, it can be used in communication-free areas such as mountainous regions. Also, since it does not involve external radio transmission, wireless licenses or installation notifications are not required.

• Immediate positioning: There is virtually no need to wait for initial convergence after startup; you can obtain your current position right away. You avoid the stress of waiting a long time for a Fix as with RTK.

As described above, standalone noRTK positioning is simple and useful in situations that do not require high precision. For example, the car navigation systems and smartphone mapping apps we use in daily life use the noRTK method (standalone GNSS positioning), and in everyday use, meter-level errors are acceptable and you can reach your destination without issues. For applications where larger errors are acceptable, noRTK is often sufficient without resorting to RTK.

Of course, for precise tasks that cannot tolerate centimeter-level errors, ensuring high precision with RTK takes priority over the convenience of noRTK. As a solution to make RTK positioning more reliable and easier to use, we next introduce simple surveying with LRTK.

What is simple surveying with LRTK?

As we have seen, RTK positioning requires advanced technology and suitable environmental conditions, and operations can sometimes be cumbersome. Common issues include "unable to place the antenna in an ideal location," "the site is too far from the base station," or "lacking the expertise to confidently configure settings." Our LRTK simple surveying solution is useful in such situations.

LRTK is a system developed to make centimeter-class positioning in the field easier and more reliable, consisting of a compact high-performance RTK-GNSS receiver and a smartphone app. It has unique features not found in conventional equipment and addresses the problem of "unable to get a Fix" from both hardware and software perspectives. Key points include:

• Stable positioning with multi-GNSS and dual-frequency: LRTK receivers support multiple satellite constellations such as GPS, GLONASS, Galileo, and QZSS (Michibiki), and perform positioning with dual-frequency L1/L2 signals. Even in urban areas, they can capture a sufficient number of satellites, and their ability to remove ionospheric errors improves, minimizing problems from insufficient satellite count or baseline length and enabling a stable Fix in a short time.

• Support for CLAS satellite augmentation signals: Some models can receive CLAS, the centimeter-level augmentation service provided by Japan’s QZSS (Michibiki), allowing them to obtain centimeter-class correction information directly from satellites even when an RTK base station cannot be set up. This enables high-precision positioning in mountainous or wide-area work where communication is unavailable, and maintains accuracy without worrying about communication outages or baseline constraints.

• Easy operation via smartphone linkage: The dedicated app lets users intuitively manage base/rover settings and connection status on site. Satellite reception status and correction data status can be checked at a glance on the screen, and if a Fix is not achieved, the cause can be quickly identified. Ntrip setup complexity is reduced because pre-registered correction services can be selected for connection, greatly reducing configuration mistakes. High usability allows on-site personnel without specialized knowledge to operate correctly—another strength of LRTK.

• Cloud integration and tilt compensation: Positioning data can be synchronized to the cloud in real time, allowing immediate sharing and checking before returning to the office. Newer models include built-in tilt sensors in the receiver that automatically correct for a tilted pole and obtain accurate coordinates. This enables high-accuracy positioning even when holding the pole at an angle to avoid obstacles, improving work efficiency.

LRTK thus offers a unique solution that balances RTK positioning accuracy with usability. It is designed to minimize "unable to get a Fix" problems common on site and allow anyone to perform high-precision surveying easily. If you are currently struggling to obtain a Fix in your operations, consider switching to LRTK simple surveying; it can be a reliable partner for obtaining a stable Fix even in complex environments.

FAQ

Q1. What are the typical positioning errors for Fix, Float, and noRTK (Single) states? A. Generally, a Fix solution has errors of almost within ± a few centimeters. A Float solution typically has deviations on the order of ± several decimeters, and a noRTK (Single) state can deviate by ± several meters or more. For example, in an LRTK system case, target accuracies are within 10 m (32.8 ft) in noRTK, within 1 m (3.3 ft) in Float, and within 2 cm (0.8 in) in Fix. Therefore, for precision work, Float or Single is insufficient, and you should always obtain a Fix before using position information.

Q2. How many satellites are minimally required to obtain a Fix with RTK? A. It depends on the algorithm, but generally it is said that both the base and rover need to simultaneously track five or more common satellites. Four GPS satellites alone usually allow only standalone positioning, not an RTK fixed solution. If the base and rover share five common satellites—ideally six or more—the chance of achieving a Fix increases. Modern receivers are multi-GNSS capable and can use ten or more satellites simultaneously, reducing cases where a lack of satellites prevents a Fix. However, satellite geometry is also important; if satellites are clustered in one part of the sky, accuracy may still be poor despite many being visible. Choosing times when satellites are well distributed in the sky is often a shortcut to obtaining a Fix.

Q3. How long does it usually take from starting RTK positioning to obtaining a Fix solution? A. Under good conditions, many cases reach a Fix within 30 seconds to 2 minutes after powering on the receiver. If sky visibility is good and satellite signals are stable, a fixed solution within 1 minute is not uncommon. Conversely, in poor environments or if initial correction data reception is delayed, Float can persist for more than 5 minutes. Once a Fix is obtained, it is generally maintained as long as positioning continues (unless communication is lost or the environment changes suddenly). If a Fix is not obtained after more than 5 minutes, consider the causes discussed in this article and review settings and the environment. In some cases, restarting the receiver or moving location can achieve a Fix more quickly.

Q4. Do weather or time of day affect RTK’s ability to obtain a Fix? A. Weather itself (rain or clouds) does not greatly affect GNSS signals, so there is little difference in RTK fixability between sunny and rainy days. However, heavy rain causing water droplets on the antenna can slightly reduce reception sensitivity. Time of day affects satellite geometry and ionospheric conditions. The number of visible satellites changes over time; for example, there can be periods such as around 2–4 p.m. when temporarily fewer satellites are visible (depending on the satellite systems used). During daytime, increased solar activity can cause larger ionospheric disturbances, which can increase errors and destabilize Fix for long-baseline RTK. Therefore, selecting times when satellite geometry is favorable and the ionosphere is stable increases success rates. Generally, early morning or nighttime tend to be more stable for maintaining a Fix.

Q5. If the system remains in noRTK without obtaining a Fix, what countermeasures are there? A. First, review the positioning environment. If there are many obstacles nearby, move to a location with a clearer sky to capture more satellites. If using a base station, recheck the base station setup location and reference coordinate for correctness. If the base- rover distance is too long, shorten the distance if possible or consider using a regional continuously operating reference station network (VRS). Check GNSS settings: ensure the rover and base are configured to use the same satellite systems (GPS, GLONASS, etc.) and frequency bands. Finally, verify that correction data is actually being received by checking the communication status. If these measures do not improve the situation, consider switching to a more stable positioning system like LRTK.

Q6. What is the difference between DGPS (Differential GPS) and RTK? A. DGPS (Differential GPS) is a general term for techniques that improve positioning accuracy using base station corrections, typically achieving meter- to sub-meter-level improvements. RTK, on the other hand, uses carrier-phase measurements to achieve centimeter-level accuracy through high-precision differential positioning. For example, SBAS (satellite-based augmentation systems) that correct code (pseudo-range) errors or DGPS for marine use can reduce errors to below 1 m, but RTK resolves integer ambiguities in the carrier phase to reduce errors to a few centimeters. However, RTK requires more sophisticated equipment and algorithms and is more complex to operate than DGPS.

Q7. What equipment and preparations are needed to use RTK positioning? A. Basically, you need an RTK-capable GNSS receiver (rover) and a means to provide correction information (a base station or network service). If you provide your own base station, you must install a GNSS receiver at a known coordinate and prepare radio equipment to transmit correction data to the rover (base GNSS receiver + communication equipment + tripod, etc.). If using national or commercial network RTK services, the rover must connect to the internet via cellular communication to obtain correction data from the provider. This requires a service contract and Ntrip connection settings. In any case, achieving centimeter-level accuracy requires a high-performance receiver and appropriate environment configuration.

Q8. In the end, which should you use: noRTK or RTK? A. It depends on the required accuracy. If meter-level errors are acceptable, simple noRTK (standalone positioning) is sufficient—it's low-cost and low-effort. If centimeter-level accuracy is required, RTK high-precision positioning is essential. In actual operation, RTK receivers will automatically output positions in noRTK (Single) mode when correction data is not available. Think of noRTK as the basic mode and RTK as the high-precision mode, and choose based on the accuracy required at each site.