Total Electron Content (TEC) Processing from GPS Observations to Facilitate Ionospheric Modeling

With the increasing global distribution of high rate dual-frequency GPS receivers the production of a real time atmospheric constituent definition, TEC, has become a beneficial contributor to the modeling applications used in the assessment of GPS position accuracy and the composition of the ionosphere, plasmasphere, and troposphere. Historically, TEC measurements were obtained through post processing techniques to produce the quality of data necessary for modeling applications with rigorous error requirements. These procedures necessitated the collection of large volumes of data to address the various abnormalities in the computation of TEC associated with the use of GPS pseudorange and carrier phase. A post-processing model application can achieve greater data quality controls and source selection while real-time modeling environments must rely on autonomous controls and filtration techniques to prevent the production of erroneous model results. In this paper we will present methods for processing TEC in real-time, which utilize several procedures including the application of an ionospheric model to automatically perform quality control on the TEC output and the computational techniques used to address receiver multi-path, faulty receiver observations, cycle-slips, segmented processing, and receiver calibrations. The resulting TEC measurements are provided with rigorous error estimates to assist in numerical space weather model assimilation of the ionosphere and provide a predictive atmospheric definition necessary to encompass the troposphere and plasmasphere.