engleski

On long-term solar activity impact on GPS single- frequency 3D positioning accuracy in the Adriatic Region

The Sun acts as the main driver of processes affecting the Earth’s ionosphere, directly and indirectly influencing the Global Navigation Satellite System (GNSS) signals’ timing measurements. Solar impacts can be categorized according to different timescales that are short- lasting (regarding minutes during solar events), diurnal, seasonal (yearly) and perennial, covering the duration of the solar cycle. The proposed paper deals with seasonal and solar cycle and its impact on Global Positioning System (GPS) single frequency (L1) positioning accuracy. Solar activity was analyzed during 17 years of available observation data. For this purpose, Sunspot Number (SSN) and Daily Solar Flux 10.7 cm (SFD) were analyzed. Indices were compared with GPS three- dimensional positioning deviations calculated on three locations in the broader region of the Adriatic Sea. Positioning data were calculated as single frequency solutions, obtained from the International GNSS Service (IGS) Receiver INdependent EXchange (RINEX) data. A significant correlation has been found between positioning accuracy and elaborated indices, both with and without the employment of standard ionospheric correction model, as presented. The emphasis was given on unmodelled positioning solution or errors, respectively, to employ a GPS receiver as a partial solar activity indicator. Besides solar cycle related period, seasonal positioning deviations were analyzed in the frame of the Local Equatorial Coordinate System (LECS) with declination and hour angle as main coordinates. Detectable positioning error increase has been observed during periods of positive Sun declination (in Northern hemisphere), based on the scenario of 4 consecutive years within the elaborated period. Obtained results rendered the possibility of predictive modelling of the GPS L1 positioning error. For this purpose, the elastic net regression method was used, employing SSN and SFD indices as predictors. Results are presented and discussed, with observations and findings summarized in the concluding chapter, together with the desirable continuation of the research.

solar cycle, seasonal variations, ionospheric delay, 3D GPS positioning accuracy, local equatorial coordinate system, predictive modelling, Adriatic region

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