TEC – Total Electron Content

The Total Electron Content (TEC) is the total number of free electrons integrated along a path between a satellite and a ground receiver, usually expressed in TEC units (1 TECU = 10¹⁶ electrons per square meter). It quantifies the ionospheric influence on radio signals such as GNSS transmissions. Variations in TEC cause signal delays and phase shifts, leading to positioning errors if not corrected. TEC can be mapped globally or regionally to monitor ionospheric conditions and improve navigation accuracy.

More Info: https://geodesy.science/item/ionosphere/