Аннотация:With the development of receiving equipment and GNSS and SBAS constellations, the coherent dual frerquency L band transmissions are now available from a number of geostationary satellites. These signals can be used for ionospheric total electron content (TEC) estimations. In this work, we present the results of the comparison of the noise patterns in TEC estimations using signals of geostationary satellites of augumentation systems – Indian GAGAN, European EGNOS and American WAAS, as well as the signals of Chinese COMPASS/Beidou navigational system. We show that noise level in TEC estimations based on geostationary satellites of COMPASS/Beidou system is times smaller than for SBAS and corresponds to those of GPS/GLONASS at the same elevation angles. We also discuss the capabilities of geostationary TEC observations in connection with recent G4 geomagnetic storm of March 2015.