Methodologies

For the detection of Travelling Ionospheric disturbances, eight complementary methodologies are applied in the TechTIDE project with real-time and historical data from Digisonde DPS4D ionospheric sounders, from the Continuous Doppler Sounding System and from GNSS receivers.

  1. HF-TID method
  2. CDSS-MSTID detection method
  3. GNSS TEC gradient algorithms
  4. Spatial and Temporal GNSS analysis
  5. The AATR indicator
  6. HF Interferometry method
  7. HTI technique to monitor wave activity
  8. TaD 3D mapping of the electron density

5. The AATR indicator

(Sanz et al., 2014)

Figure 5: Relationship between the daily EGNOS APV1 availability (in red colour) and the daily maximum values of AATR (in blue colour). The horizontal green line indicates an experimental threshold for AATR of 1 mm/s of L1 delay.

In the context of ESA founded ICASES project, the Research group of Astronomy and Geomatics (gAGE/UPC) defined the Along Track TEC Rate (AATR) index (Sanz et al., 2014). This index has been used to identify the conditions where a degradation in the user performance of the SBAS systems in general, and in EGNOS in particular, is expected.

As an example, Figure 5, shows the relationship between the AATR index and the EGNOS APV1 availability over a period of two years for a station in Canary Islands (MAS1). These results are after the EGNOS v2.3.1 upgrade (from May 25th 2012 to August 15th 2014). As it can be seen, high values of this index lead to worse performances in the EGNOS APV1 availability due to the ionospheric conditions.

The AATR index has been chosen as the metric to characterize the ionosphere operational conditions in the frame of EGNOS activities. This indicator has been also proposed for joint analysis in the International SBAS-Ionosphere Working Group.

Sanz, J., J.M. Juan and G. Gonzรกlez-Casado, et al. Novel Ionospheric Activity Indicator Specifically Tailored for GNSS Users. Proc. 27th International Technical Meeting of The ION GNSS+ 2014, Florida, September 8-12, 2014.

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