Operational Multi-GNSS Global Ionosphere Maps at GFZ Derived from
Uncombined Code and Phase Observations
Abstract
GNSS networks with multi-frequency data can be used to monitor the
activity of the Earth’s ionosphere and to generate global maps of the
vertical total electron content (VTEC). This paper introduces and
evaluates operational GFZ VTEC maps. The processing is based on a
rigorous least-squares approach using uncombined code and phase
observations, and does not entail leveling techniques. A single-layer
model with a spherical harmonic VTEC representation is used. The
solutions are generated in a daily post-processing mode with GPS,
GLONASS, and Galileo data, and are provided for the period since the
beginning of 2000. A comparison of the GFZ VTEC maps with the final
combined IGS product shows a high consistency with the solutions of the
IGS analysis centers. A validation with about four years of Jason-3
altimetry-derived VTEC data is provided, in which the GFZ solution has
the smallest bias of 1.2 TEC units compared to the solutions of the IGS
analysis centers, and with 3.0 TEC units one of the smallest standard
deviations.