As night fell on May 10, 2024, millions of curious people across the globe ventured outside in hopes of catching a glimpse of the northern lights in the darkness — and better yet, capturing a spectacular photo. Previously visible only in arctic regions, this phenomenon came into view as far south as Alabama and California as the night’s aurora borealis revealed itself, etching the moment into our memories. And it all became possible thanks to solar activity being at nearly a 20-year high.
But what was a sense of beauty and wonder for many also served as a time of concern and even angst for those who either provide or rely on accurate positioning from satellites. This unusual phenomenon was caused by a G5 level geomagnetic storm that lasted two days — making it the most significant geomagnetic storm descended on Earth since 2003. NOAA’s Space Weather Prediction Center measured its Estimated Planetary K-Index (Kp index) — a common metric-based gauge for geomagnetic storms — on a 9 point scale, on which it hit maximum values at various monitoring stations.
The aurora borealis sets the stage to gauge Trimble IonoGuard
This provided the ultimate opportunity to field test the performance of Trimble® IonoGuard™, as Dr. Stuart Riley, Trimble VP of technology - GNSS, notes in this LinkedIn post. IonoGuard, unveiled in October, is the culmination of Trimble’s decades of data collection and engineering development. Purposefully designed to help mitigate the impacts of ionospheric disturbances on GNSS performance with ample signal tracking change capabilities, this solution estimates various parameters on a per-satellite basis, adjusting the position engine to maintain accuracy.
Due to seasonal effects and the nature of this storm, it was expectedly less impactful in equatorial regions, while significant effects were seen in polar and mid-latitude areas. Riley’s post focuses on the effects seen at a site in Northern Alberta, Canada (around 57 degrees north latitude).
Northern Alberta
GNSS receivers in Northern Alberta saw the ionospheric disturbance begin around 18:00 hours UTC on May 10. Looking at Trimble’s historic RTK engine on a 1.8 kilometer RTK baseline we see that the position solution was severely impacted throughout the storm. The system struggles to provide reliable positioning during the storm, with large outliers occurring frequently.
The Trimble ProPoint engine (without IonoGuard) performs better, although it struggles to provide reliable positioning with errors of tens of centimeters. 1
1 An earlier version of this paper had used the ProPoint RTK engine from the version 6.20 firmware in the analysis, rather than the version 6.26 ProPoint RTK engine used throughout this analysis. The earlier ProPoint RTK engine was more susceptible to drops out of RTK due to the ionospheric disturbances.
