Abstract
The ionosphere is still considered one of the most significant error sources in precise Global Navigation Satellite Systems (GNSS) positioning. On the other hand, new satellite signals and data processing methods allow for a continuous increase in the accuracy of the available ionosphere models derived from GNSS observables. Therefore, many research groups around the world are conducting research on the development of precise ionosphere products. This is also reflected in the establishment of several ionosphere-related working groups by the International Association of Geodesy. Whilst a number of available global ionosphere maps exist today, dense regional GNSS networks often offer the possibility of higher accuracy regional solutions. In this contribution, we propose an approach for regional ionosphere modelling based on un-differenced multi-GNSS carrier phase data for total electron content (TEC) estimation, and thin plate splines for TEC interpolation. In addition, we propose a methodology for ionospheric products self-consistency analysis based on calibrated slant TEC. The results of the presented approach are compared to well-established global ionosphere maps during varied ionospheric conditions. The initial results show that the accuracy of our regional ionospheric vertical TEC maps is well below 1 TEC unit, and that it is at least a factor of 2 better than the global products.
Highlights
In the last decades, Global Navigation Satellite Systems (GNSS) have been rapidly evolving and have found a large number of applications in a broad range of commercial and scientific fields
The ionosphere is a layer of the atmosphere ranging from about 50 to 1000 km consisting mostly of ionized particles that cause satellite signals to be delayed or advanced
The authors compared several existing and publically available ionosphere models to satellite altimeter data, and the results showed that the accuracy of absolute vertical total electron content (TEC) was on the level of 4–5 TECU (15–25% relative)
Summary
Global Navigation Satellite Systems (GNSS) have been rapidly evolving and have found a large number of applications in a broad range of commercial and scientific fields. The authors compared several existing and publically available ionosphere models to satellite altimeter data, and the results showed that the accuracy of absolute vertical TEC (vTEC) was on the level of 4–5 TECU (15–25% relative) In this contribution we selected five popular ionosphere models as background reference models for comparisons with our solution: the International GNSS Service (IGS), Center for Orbit determination in Europe (CODE), European Space Agency (ESA), Jet Propulsion Laboratory (JPL) and Technical University of Catalonia (UPC). ESA GIM is based on processing carrier phase-smoothed pseudoranges and TEC parametrization using SHE functions It is characterized by 2.5 by 5.0 degrees spatial resolution, and temporal resolution of 2 h [23]. The manuscript is organized into four sections: (1) Introduction presenting the background and rationale for the research. (2) Methodology, where we describe (a) our new method for the carrier phase bias estimation, (b) slant and vertical TEC calculation procedure, (c) our implementation of TPS for TEC interpolation. (3) Numerical Results and Discussion where we define our test dataset, reference ionosphere models, approach to slant TEC (sTEC) self-consistency analysis, test results and their discussion. (4) Conclusions outlining new findings resulting from this research
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