GNSS (Global Navigation Satellite System) observable errors are affected by systematic errors due to the free electrons present in the ionosphere. The error associated with ionosphere depends on the Total Electron Content (TEC), which is influenced by several variables: solar cycle, season, local time, geographical location and geomagnetic activity. GPS (Global Positioning System), GLONASS (Global Orbiting Navigation Satellite System) and Galileo dual frequency receivers allow to calculate the error affecting GNSS observables and the TEC. With the rate of change in the TEC (ROT), it is possible to establish indices indicating irregularities in the ionosphere, thus enabling inferences to be drawn as to the behaviour of the ionosphere. It is currently possible to carry out such studies in Brazil due to the various Active Networks available, such as the RBMC/RIBaC (Brazilian Continuous Monitoring Network/INCRA Community Bases Network) and the Active GNSS Network of the State of São Paulo. The proposed research aimed at estimating and analysing ionosphere irregularity indices, as well as addressing the geo-sciences of information on ionosphere behaviour.