Online Determination of GNSS Differential Code Biases using Rao-Blackwellized Particle Filtering

A-CHAIM is a data assimilation model of the high latitude ionosphere, incorporating measurements from multiple kinds of instruments, including slant Total Electron Content measurements from ground-based Global Navigation Satellite System (GNSS) receivers. These measurements have receiver-specific instrumental biases which must be resolved to produce an absolute measurement, which are resolved along with the ionospheric state using Rao-Blackwellised particle filtering. These instrumental biases are compared to published values and estimation techniques, which show small but consistent systematic differences. The potential cause of these systematic biases is investigated. It is shown that if A-CHAIMs biases agreed with other estimation techniques, the result would be a overestimation of NmF2 ranging from < 10% during the day to over 20% at night, or a > 30% overestimation of topside electron density at 800km altitude