Computing unambiguous TEC and ionospheric delays using only carrier phase data from NOAA´s CORS network

A new method for computing absolute (unambiguous) levels of Total Electron Content (TEC) and subsequently the L1 and L2 phase delays of GPS is presented. Unlike previous computational methods, this one relies solely upon dual frequency, ambiguous carrier phase data without any reliance on pseudo-range, a-priori values or other external information. The only requirements for this method are that the ionosphere is assumed to lie in a two-dimensional shell of constant ellipsoidal height, and that the GPS data come from a network of ground stations, geographically separated so as to allow satellites to be viewed by a variety of stations at overlapping times. The usefulness of this method and its application toward nowcasting and forecasting of the ionosphere are also discussed.