For high-precision GNSS users, the ionosphere has always been an invisible, unpredictable variable. As we deal with the 2025 peak of Solar Cycle 25, the impact of ionospheric disturbances, including increased total electron content (TEC) and signal scintillation, is becoming a more frequent and pressing challenge. This activity can delay GNSS signals, degrade accuracy, and ultimately, impact productivity.
While advanced mitigation technologies are being developed, the critical question remains: how do they perform in real-world conditions? A recent test conducted in Colorado provides a clear, data-driven answer.
The test: A head-to-head comparison
On April 27, 2025, during a documented period of medium ionospheric disturbance, a controlled test was performed. Two identical Trimble® R750-2 GNSS receivers were set up in close proximity, using the same firmware version and connecting to the Trimble VRS Now™ network.
In this image, we can see the ramp up of the ionospheric Index, total electron count (TEC) and a minimal amount of scintillation as depicted by the dotted black line. The ionospheric index is “medium,” meaning it’s not high enough to cause a complete GNSS blackout, but is high enough to cause signal delays and degrade the accuracy of GNSS measurements.
Receiver A received the standard correction stream
Receiver B received the same correction stream, but with Trimble IonoGuard™ technology enabled, which protects RTK GNSS from ionospheric disturbances
This created a direct, side-by-side comparison to measure the effectiveness of specialized ionospheric mitigation.
The proof: Stable positions under pressure
The results were immediate and unambiguous. The position error plots showed that the receiver without IonoGuard experienced noticeable degradation in positioning, with higher error residuals corresponding to the ionospheric activity.
This data is using the R750-2 with the most up-to-date firmware version (6.40) released in late April 2025. The above graph is the position error plot for all data collected while the R750 was connected to the Trimble VRS Now network in Colorado. We can see how the ionospheric activity (shown at top) can affect the positioning accuracy and performance of the GNSS solution. The user would experience positioning degradation, resulting in higher error residuals, indicated at the arrows.
In contrast, the data shows the receiver with IonoGuard enabled was significantly less impacted by the same atmospheric event.
A second R750-2 with the same firmware version was used to collect data simultaneously, but this time connected to the Trimble VRS Now network with IonoGuard enabled in the stream and fallback mode enabled on the receiver.
In the above graph, we can see that the positioning error was less impacted by the ionospheric activity during the same period of time in the latitude, longitude and height components.
In this data set, the receiver is not receiving ionospheric corrections from the Trimble VRS Now correction stream. This image shows the positioning errors. but includes the 68 percentile (1σ in red), 95th percentile (2σ in reddish-orange), and 99th percentile (3σ in orange) standard deviations from the mean.
You can see again where the ionospheric activity disturbed the quality of the GNSS positioning data in the latitude, longitude and height components.
In this dataset, the receiver is receiving ionospheric information from the Trimble VRSNow correction stream with fallback mode enabled on the device. This image shows the positioning errors but includes the 68 percentile (1σ in red), 95th percentile (2σ in reddish-orange), and 99th percentile (3σ in orange) standard deviations from the mean.
When comparing this image and the one above, it is quite clear that having IonoGuard in the correction stream improved the overall positioning performance during the ionospheric event.
The most compelling evidence is visualized in the comparison scatter plot.
This scatter plot from the test shows the longitude and latitude error for the receiver with IonoGuard disabled (red) and IonoGuard enabled (blue).
As the image shows, the positions from the IonoGuard-enabled receiver are tightly clustered, representing a stable and reliable result. The data from the standard receiver is widely scattered, with significantly more outliers and distribution away from the mean, showing the ability of Trimble ProPoint® technology with IonoGuard to protect data integrity when IonoGuard information is present in the correction stream.
Conclusion: From theory to field-proven value
This test moves beyond theoretical benefits to offer tangible proof of performance. It demonstrates that in the face of real-world ionospheric disturbances, the intelligence within the correction stream is what provides resilience. As the industry navigates the peak of this solar cycle, utilizing an end-to-end GNSS system — where the receiver and the corrections network work in concert with advanced mitigation like IonoGuard — is essential for maintaining productivity and confidence in your positioning.
