Determining receiver biases in GPS-derived total electron content in the auroral oval and polar cap region using Ionosonde measurements

Global Positioning System (GPS) total electron content (TEC) measurements, although highly precise, are often rendered inaccurate due to satellite and receiver differential code biases (DCBs). Calculated satellite DCB values are now available from a variety of sources, but receiver DCBs generally remain an undertaking of receiver operators and processing centers. A procedure for removing these receiver DCBs from GPS-derived ionospheric TEC at high latitudes, using Canadian Advanced Digital Ionosonde (CADI) measurements, is presented. Here we will demonstrate the inadequacy of common numerical methods for estimating receiver DCBs in high-latitude regions and compare our CADI-calibrated vertical TEC (vTEC) measurements to corresponding IGS IONEX interpolated vTEC map data. We demonstrate that the bias values determined using the CADI method are largely independent of the topside model (exponential, Epstein, and α-Chapman) used. We further confirm our results via comparing CADI-estimated biases with those derived from incoherent scatter radar (ISR) measurements. These CADI-method results are found to be within 1.0 TEC units (TECU) of ISR measurements, where the numerical methods used are found to be in excess of 5.0 TECU in error when compared to ISR measurements.