# GNSS TEC Calibration

TEC data are derived from carrier phase measurements for both GPS or GPS+GLONASS satellite systems.

The basic relation used to calibrate the TEC is as follows:

S Φ = sTEC + βias arc

where:

S Φ is the ionospheric delay from the raw carrier phase observations,

βias is the arc-offset, a constant to be determined for each arc of observations related to a given receiver and satellite pair. βias represents the contribution of receiver and satellites biases (δbR, δbs), and the contribution of any non-zero averaged errors over an arc of observations, e.g. the multipath (<δm>arc).

A two-dimensional thin shell model at 350 km is used to define the mapping function between the slant and vertical TEC. The vertical ionospheric variation is expressed as a function of the modip and the Local Time of the ionospheric pierce points (IPPs).

GNSS TEC Calibration online (On demand service)

Reference: *Ciraolo, L., et al*. "Calibration errors on experimental slant total electron content (TEC) determined with GPS." Journal of Geodesy 81.2 (2007): 111-120