A Ground-Based Augmentation System (GBAS) includes a plurality of Global Navigation Satellite System (GNSS) reference receivers configured to receive and process GNSS satellite measurements. The GBAS further includes at least one processing module communicatively coupled to the plurality of GNSS reference receivers, configured to: determine a respective ionosphere quality metric along lines of sight for of observable GNSS satellites using code minus carrier measurements from the observable GNSS satellites; define one or more valid ionosphere regions where at least one respective ionosphere quality metric meets a threshold; determine which of the observable GNSS satellites have an ionosphere pierce point within the one or more valid ionosphere regions; and output at least one overbounded Vertical Ionosphere Gradient standard deviation (Ã vig ) corresponding to the one or more valid ionosphere regions and an indication of which observable GNSS satellites have an ionosphere pierce point within the one or more valid ionosphere regions.
USING CODE MINUS CARRIER MEASUREMENTS TO MITIGATE SPATIAL DECORRELATION ERRORS CAUSED BY IONOSPHERE DELAYS