Evaluation of the 1993 Omega propagation correction model

Motivated by reported large phase prediction errors using the current propagation correction (PPC) model/algorithm (known as the 1980 PPC model, or PPC80) for paths undergoing day/night transition, the Coast Guard Omega Navigation System Center (ONSCEN) has sponsored development of a new PPC model, known as the 1993 PPC model (PPC93). The new model includes the following elements not addressed in earlier PPC models: (1) full coupling of geomagnetic and conductivity sub-models, (2) embedded model parameters which capture the transition onset and recovery phase profiles, and (3) use of path transition data (together with path-day and path-night data) in the model calibration. PPC93 has been calibrated and tested at 10.2, 111/3, and 13.6 kHz using both phase and phase difference data sets. Performance measures, including phase/phase-difference prediction error and position accuracy, for both PPC93 and PPC80 are presented. Comparisons of the two models in terms of these performance measures are given for the calibration database and several other databases