engleski

Klobuchar - Like Local Model of Quiet Space Weather GPS Ionospheric delay for Northern Adriatic

Ionospheric delay is the major source of satellite positioning system performance degradation. Designers of satellite positioning systems attempt to mitigate the impact of the ionospheric delay by deployment of correction models. For instance, the American GPS utilise a global standard (or Klobuchar) model, based on assumption that daily distribution of GPS ionospheric delay values follows biased cosine curve during day-time, while during the night-time the GPS ionospheric delay remains constant. Providing a compromise between computational complexity and accuracy, Klobuchar model is capable to correct up to 70% of actual ionospheric delay, mainly during quiet space weather conditions. Unfortunately, it provides a very poor performance during severe space weather, geomagnetic and ionospheric disturbances. In addition, a global approach in Klobuchar model development does not take into account particularities of the local ionospheric conditions, which can significantly contribute to the general GPS ionospheric delay. Current research activities conducted worldwide are concentrated on better understanding of the observed GPS ionospheric delay dynamics and relation to local ionosphere conditions. Here we present the results of a study addressing daily GPS ionospheric delay dynamics observed at Croatian coastal area of northern Adriatic (position φ = 45°N, λ = 15°E ) in the periods of quiet space weather in 2007. Daily sets of actual GPS ionospheric delay values were assumed the time series of composite signals, consisting of DC, cosine and residual components, respectively. Separate models have been developed, that describe components of actual GPS ionospheric delay in northern Adriatic for summer-time and winter-time, respectively. A special emphasis was given to statistical description of the residual component of daily distribution of GPS ionospheric delay, obtained by removing DC (bias) and cosine component from the composite GPS ionospheric delay. Future work will be focused on further evaluation and validation of quiet space weather GPS ionospheric delay model for northern Adriatic, transition to non-Klobuchar model, and on research in local GPS ionospheric delay dynamics during disturbed and severe space weather conditions.

satellite navigation; GPS ionospheric delay; space weather; classical decomposition

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