Increase Ionosphere

Impact of increased ionospheric activity upon high-precision GNSS

Increased ionospheric activity can have a significant impact on GNSS signal positioning and tracking performance.

The ionosphere, which extends from an altitude of approximately 50 km to approximately 1000 km, affects the propagation of GNSS signals, which can result in an ionospheric delay proportional to the total electron content (TEC) along the path of transmission. the signal. In addition, localized irregularities in electron density cause rapid temporal fluctuations in both the amplitude and phase of the GNSS signals, known as ionospheric scintillation.

To mitigate the effects of increased ionospheric activity on high-precision GNSS performance, it is recommended to follow certain steps such as using the latest firmware version on all GNSS sensors, using multi-constellation, using multi-frequency GNSS observations and RTK corrections, use the default elevation cut angle of 10 degrees, among others. However, it is important to note that in extreme scintillation scenarios, all GNSS and L-band signals may be affected, which could result in significant degradation or even complete loss of GNSS fixing.

How does the ionosphere affect high-precision GNSS?

The GNSS signal experiences a delay when passing through charged particles in the ionosphere. The ionospheric delay is directly related to the total electron content (TEC) along the signal path. Furthermore, irregularities in electron density cause rapid temporal fluctuations, known as ionospheric scintillations, in the amplitude and phase of transionospheric GNSS signals.

High-precision GNSS sensors can estimate and correct for adverse ionospheric impact, but they are not immune to high ionospheric activity. This can result in reduced GNSS signal tracking, reduced L-band communications link strength, increased RTK initialization and PPP convergence times, and reduced positioning accuracy of fixed RTK convergent solutions. and PPP.

Since TEC varies depending on the geographic location of the receiver, time of day, season, and level of solar activity, predicting the impact of increased ionospheric effects on high-precision GNSS is not easy.

How can a GNSS user mitigate the effects?

To help mitigate the effects of increased ionospheric activity on high-precision GNSS performance, it is recommended that:

  • Use the latest firmware version on all GNSS sensors to achieve the best GNSS positioning and tracking performance.
  • Use multi-constellation (GPS, GLONASS, Galileo, BeiDou, QZSS) to increase the number of observations available for the positioning solution and increase the diversity of tracked GNSS signals.
  • Use GNSS observations and multi-frequency (3 or more) RTK corrections, which can help mitigate ionospheric effects.
  • Use RTK correction data generated from a reference station with a shorter baseline length whenever possible.
  • Use the default elevation cut angle of 10 degrees.
  • For high precision survey applications, apply double/multiple occupancies at different times under different ionospheric conditions.

Although these steps help mitigate the adverse impact of increased ionospheric activity, all GNSS and L-band signals can be affected in extreme scintillation scenarios, which could lead to significant degradation or even complete loss of GNSS fixing.

 

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