VTEC Map. This diagram is the map of the Vertical Total Electron Content over Europe. The Total Electron Content (TEC) is a common descriptive parameter of Earth’s ionosphere; it represents the total number of electrons integrated between a radio transmitter and receiver along a tube of one meter squared cross section, i.e., the electron columnar number density.

The TEC depends on local time, latitude, longitude, season and geomagnetic conditions.
TEC values along the signal-in-space path are derived by processing calibrated dual frequency measurements collected by a network of GNSS receivers.

Then, such measurements are verticalized and interpolated to produce VTEC European maps in TECu, by assuming the thin-shell layer simplification at a height of 350 Km. A TECu (TEC unit) consists of 1016 electron per square meter and is approximately equivalent to a 16 cm delay at L1 frequency.

The ionospheric grid map ha a resolution of 1° x 1° lat/lon. A new image is updated every 10 mins with a latency of about 2 hrs in UTC time.

VTEC Gradient Map. This diagram is derived from the VTEC maps and shows the maximum magnitude of spatial gradients along E/W and S/N directions.

Due to their order of magnitudes, VTEC gradients are calculated in TECu / Km. Similarly to the VTEC maps, a new map with resolution 1° x 1° is updated every 10 mins with a latency of 2 hrs in UTC time.

Maximum VTEC map. This diagram shows the maximum VTEC value recorded during last hour on the European region. The shown quantities are expressed in TECu and are derived from the VTEC maps generated on periodic basis.