Monitoring Seasonal Variations of Ionospheric TEC Using GPS Measurements

Georgiadiou ionospheric model was adopted to determine satellite-plus-receiver differential delay.The satellite-plus-receiver differential delay was estimated as constant values for each day.Dual-frequency GPS pseudo-ranges observables were used to compute vertical TEC(VTEC).All the monthly mean VTEC profiles were presented using GPS data of Beijing IGS site between 2000 and 2004.All the monthly averaged values and amplitudes of VTEC were also presented.The results indicate that the VTEC has seasonal dependency.The maximum VTEC values are observed in March and April,the minimum VTEC values in December.The seasonal variations trend is found to be the same after polynomial fitting between 2000 and 2004.