Can Single-Frequency RTK Still Be Used? Applications, Accuracy, and Limitations

RTK (Real-Time Kinematic) is widely used to achieve centimeter-level GNSS positioning in surveying, agriculture, robotics, UAV mapping, and machine control applications.

Today, most high-performance RTK receivers support dual-frequency or multi-frequency GNSS observations. This has led to a common misunderstanding: single-frequency RTK is outdated or no longer practical.

However, this is not entirely true.

Under suitable conditions, single-frequency RTK can still achieve centimeter-level positioning accuracy. The key question is not whether it works, but where it can work reliably.

Compared with dual-frequency RTK, single-frequency RTK is more sensitive to ionospheric conditions, baseline length, multipath, and signal quality. When operating in open environments with short baselines and stable correction data, it can provide an excellent balance between accuracy, cost, and power consumption.

Understanding these advantages and limitations is essential when selecting the right GNSS solution for a specific application.

1. How Does Single-Frequency RTK Achieve Centimeter-Level Accuracy?

A standard GNSS receiver mainly relies on pseudorange measurements. These measurements are affected by satellite clock error, orbit error, ionospheric delay, tropospheric delay, receiver noise, and multipath. As a result, normal single-point positioning usually remains at the meter level.

RTK improves accuracy by using carrier-phase observations. Carrier phase is extremely precise, but it contains an unknown value: the number of complete carrier wavelengths between the satellite and the antenna.

This unknown integer value is called integer ambiguity.

The key process in RTK is ambiguity resolution. Once the ambiguities are correctly fixed, carrier-phase measurements can be used as highly precise distance observations, enabling centimeter-level positioning.

Single-frequency RTK follows the same fundamental principle.

Its limitation is not that it cannot achieve high accuracy. The challenge is that it has fewer observations available to separate errors and validate ambiguity solutions compared with dual-frequency RTK.

Single-frequency RTK depends strongly on short-baseline error correlation between the base and rover.

2. The Main Limitation: Ionospheric Delay

The ionosphere is one of the largest natural error sources affecting GNSS positioning.

When satellite signals pass through the ionosphere, free electrons change the signal propagation speed and introduce positioning errors. The magnitude of this delay depends on signal frequency.

Dual-frequency GNSS receivers can observe two frequencies simultaneously and use the relationship between them to estimate and remove the first-order ionospheric delay.

Single-frequency receivers cannot directly perform this correction.

Instead, they rely on error correlation between the base station and rover.

When the baseline is short, both receivers experience similar atmospheric conditions. Differential processing can therefore eliminate much of the common ionospheric and tropospheric error.

This is why baseline length is one of the most important factors affecting single-frequency RTK performance.

Single-frequency RTK performs best when:

• Base and rover are close together
• Satellite visibility is good
• Atmospheric conditions are stable
• Multipath is limited

As the baseline increases, atmospheric errors become less correlated, making ambiguity resolution slower and reducing RTK reliability.

During periods of high ionospheric activity or for longer baselines, dual-frequency RTK provides significantly better robustness.

3. Fewer Frequencies Mean Less Error Redundancy

The advantage of dual-frequency RTK is not only ionospheric correction.

Multiple frequencies provide additional independent observations, which help receivers:

• Detect cycle slips
• Reject poor-quality signals
• Improve ambiguity resolution
• Maintain Fixed solutions more reliably

Single-frequency RTK has less measurement redundancy, making it more sensitive to:

• Limited satellite visibility
• Multipath reflection
• Poor antenna installation
• Signal blockage
• Low signal-to-noise ratio
• Correction data interruption

These issues may not immediately prevent the receiver from achieving a Fixed solution, but they reduce the stability of the solution.

A particularly important risk is false fixing.

A false fix occurs when the receiver reports a Fixed RTK solution while the calculated ambiguity is incorrect. Unlike a Float solution, a false fix may appear normal while introducing positioning errors.

For surveying, mapping, and control applications, maintaining reliable Fixed status is often more important than achieving a quick initial fix.

4. Suitable Applications for Single-Frequency RTK

Single-frequency RTK is most attractive when cost, power consumption, and system simplicity matter more than maximum robustness.

Typical suitable applications include open-field boundary mapping, low-speed agricultural guidance, small outdoor robots, education, RTK experiments, simple point collection, and early-stage prototype validation.

These applications share several characteristics. The sky is relatively open. The baseline is short. The platform moves slowly. Temporary loss of fixed solution does not immediately create a safety issue. In many of these cases, single-frequency RTK provides a good balance between performance and cost.

It becomes more useful when combined with other sensors. For example, a small robot may use single-frequency RTK together with an IMU, wheel odometry, vision, or a local map. In that case, RTK provides an absolute position reference rather than carrying the entire localization system alone.

Single-frequency RTK works best in open, low-multipath environments and becomes risky in urban or obstructed areas.

5. When Is Single-Frequency RTK Not Recommended?

Although single-frequency RTK can achieve centimeter-level accuracy, it is not suitable for every environment.

Performance can degrade significantly in:

• Urban canyons
• Dense forests
• Bridge areas
• Ports with large metal structures
• Construction sites
• Locations with strong multipath reflections
• Long-baseline RTK applications

In these environments, GNSS signals may be blocked or reflected, reducing carrier-phase quality and increasing the difficulty of ambiguity resolution.

Dual-frequency and multi-frequency RTK systems are generally better suited because they provide:

• Better ionospheric error mitigation
• More observation redundancy
• Faster ambiguity fixing
• Higher Fixed-solution availability
• Improved recovery after signal interruptions

Safety-critical applications require additional caution.

Examples include:

• Autonomous vehicles
• UAV landing systems
• Railway positioning
• Advanced machine control

These systems require not only accuracy, but also position integrity — the ability to recognize when the solution may no longer be reliable.

For such applications, single-frequency RTK may be used as part of a multi-sensor navigation system, but it should generally not be the only source of high-precision positioning.

6. How to Evaluate It

A proper evaluation should not rely on one successful fixed solution. The following indicators matter more: time to first fix, fixed-solution ratio, re-fix time after signal loss, coordinate jumps, error against known points, repeatability at different times of day, behavior under partial blockage, and occurrence of false fixes.

Among these, fixed-solution ratio and false-fix risk are especially important. A receiver that fixes quickly in a demo may still fail in real deployment if the environment changes.

7. Conclusion

Single-frequency RTK is not an outdated technology. Under suitable conditions, it can still provide centimeter-level positioning while offering advantages in cost, power consumption, and system simplicity.

It is a good choice for:

• Short baselines
• Open-sky environments
• Cost-sensitive applications
• Low-speed platforms
• Non-safety-critical systems

However, its limitations become more apparent in challenging environments with long baselines, strong multipath, unstable atmospheric conditions, or strict reliability requirements.

The practical question is not:

Can single-frequency RTK achieve centimeter-level accuracy?

It can.

The more important question is:

Can it maintain reliable centimeter-level positioning in the target environment?

Choosing between single-frequency and dual-frequency RTK is ultimately about matching the GNSS technology to the application requirements.

📘 Recommended Reading

How Multi-Frequency GNSS Eliminates Ionospheric Delay

Learn how multi-frequency GNSS receivers reduce ionospheric errors and improve RTK reliability, especially in longer baseline and challenging environments.