| Popis: |
Reliable modeling of ionospheric delays is one of the most challenging aspects of network-based real-time kinematic GPS. Various ionospheric models derived from global, regional, and local permanently tracking networks have been developed to support positioning and ionospheric research. This paper provides an assessment of the quality and reliability of ionospheric models supporting ambiguity resolution and kinematic positioning under severe ionospheric conditions. A 24-hour data set is analyzed, with special emphasis on varying ionospheric conditions over 24 hours. The quality of the model-dependent ionospheric corrections, time required to fix the ambiguities, and quality of the resulting coordinates are discussed. It is shown that under severe ionospheric conditions the models, even those with high spatio-temporal resolution, fail to support ambiguity resolution. However, the frequency of ionospheric events of the strength comparable to the conditions tested here is very low, and reliable results were obtained using all tested models under quiet to moderate ionospheric conditions 71-99% of the time. |
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