Estimating GPS satellite and receiver differential code bias based on signal distortion bias calibration

Differential code bias (DCB) is an important error source in Global Navigation Satellite System (GNSS) data processing. Currently, DCBs are generally divided into satellite-specific and receiver-specific parts. However, the chip shape of live signal differs from the ideal rectangle. Such signal distortion on the chip shapes will lead to systematic bias in pseudorange observations, namely signal distortion bias (SDB), which affects the accuracy of DCB estimation when different receiver types are used. Therefore, this research aims to estimate satellite and receiver DCBs based on SDB calibration and to explore how SDB affects DCB. Theoretical analysis shows receiver DCB absorbs the average SDBs and satellite DCB absorbs the rest of SDBs. Thus, the existence of SDBs results in the inconsistency of DCB estimated by different types of receivers. Abundant GNSS observations from the year 2017 to 2019 are adopted to assess DCB estimation, and the results validate that there are large biases for GPS satellite DCBs among different receiver groups if SDBs are ignored. However, the biases greatly decrease once SDBs are corrected, and the average improvement is 60.0%. The long-term variations of some satellite DCB can be attributed to the SDBs and variations of receiver group proportions in the observation network. With SDB correction, the variations in satellite DCB time series greatly decrease, especially for those intra-frequency DCB products. As for the receiver DCB, the SDB only creates a systematic bias against it and generally remains unchanged unless the satellite is changed, the receiver is replaced, or the receiver firmware is updated. Overall, the accuracy of satellite DCB improves with SDB correction in terms of consistency among different receiver groups and their long-term stabilities.