eSWua: Code-derived Total Electron Content (TEC) from 50 Hz GNSS signal samples

GNSS Total Electron Content (TEC) is computed from the 50 Hz raw signal samples acquired on two different signal frequencies and expressed in TEC units (TECu). Code-derived slant TEC (sTEC) are evaluated through the dual-frequency pseudorange observables and provided every 15 seconds (tec0, tec15, tec30, tec45) for each available GNSS satellites link (depending on the acquisition capabilities of the receiver). sTEC at 1-min resolution is provided as the average of the previous quantities. The absolute sTEC measurements are corrected from the satellite-induced biases in the case of GPS, Galileo, Beidou and QZSS satellites. Correction for the station inter-frequency biases are currently not provided. Vertical values of the TEC (vTEC) are evaluated from the 1-min sTEC by assuming the Ionospheric Pierce Point at an altitude of 350 km and by applying a specific mapping function (Mannucci et al., 1993, https://hdl.handle.net/2014/36277).