A receiver of Global Navigation Satellite Systems, GNSS, positioning signals, the receiver comprising: - a plurality of signal processing channels (440, 441) configured for processing signals received from a plurality of satellites (114, 119, 121, 123) in GNSS constellations; - a memory with a first database storing data usable to calculate atmospheric errors/corrections applicable to the receiver from a combination of one or more atmospheric errors/corrections models; - computer logic, characterized in that the computer logic is configured for calculating said data usable to calculate atmospheric errors/corrections by: - when reference signals are available, said reference signals being one of multi-frequencies signals and single frequency signals aided by atmospheric errors/corrections received from a GNSS augmentation system, selecting the atmospheric errors/corrections model which outputs a PVT that is closest to the last PVT available from the reference signals; - when reference signals are not available but have been available less than a predefined time span before, using the last atmospheric errors/corrections model selected at the time reference signals were available; - when reference signals are not available and have not been available less than a predefined time span before: • selecting a predefined model with time and/or location of usage stored in the first database; or • filtering the one or more atmospheric errors/corrections models to eliminate those that output PVT values outside a predefined confidence level and combining the models remaining at the output of the filtering. - a plurality of signal processing channels (440, 441) configured for processing signals received from a plurality of satellites (114, 119, 121, 123) in GNSS constellations; - a memory with a first database storing data usable to calculate atmospheric errors/corrections applicable to the receiver from a combination of one or more atmospheric errors/corrections models; - computer logic, - when reference signals are available, said reference signals being one of multi-frequencies signals and single frequency signals aided by atmospheric errors/corrections received from a GNSS augmentation system, selecting the atmospheric errors/corrections model which outputs a PVT that is closest to the last PVT available from the reference signals; - when reference signals are not available but have been available less than a predefined time span before, using the last atmospheric errors/corrections model selected at the time reference signals were available; - when reference signals are not available and have not been available less than a predefined time span before: • selecting a predefined model with time and/or location of usage stored in the first database; or • filtering the one or more atmospheric errors/corrections models to eliminate those that output PVT values outside a predefined confidence level and combining the models remaining at the output of the filtering. • selecting a predefined model with time and/or location of usage stored in the first database; or • filtering the one or more atmospheric errors/corrections models to eliminate those that output PVT values outside a predefined confidence level and combining the models remaining at the output of the filtering.