The proper handling of code biases is essential for realizing precise ionospheric modeling, positioning and timing. It is common to treat code biases in a differential mode as a differential code bias (DCB). With the modernization of GPS and GLONASS and the implementation of Galileo and BDS, the traditional DCB calibrations are complex and not easily extendable to different frequencies and modulations. An alternative treatment of code biases is to use observable-specific signal biases (OSBs). In this contribution, all possible OSBs are estimated for the latest GNSS and analyzed from the perspectives of precision, consistency and stability. The precisions of the GPS and Galileo OSBs are significantly better than those of the GLONASS and BDS OSBs. Considering the inter-frequency bias (IFB) of GLONASS and the inter-system bias (ISB) of BDS can improve the precisions of their OSB estimates. OSB comparisons among different agencies reveal that GPS and Galileo show good agreement at the level of 0.2–0.3 ns, while the differences of the GLONASS and BDS OSBs reach 0.5–1.0 ns. In addition, agreement of 0.4–0.5 ns is demonstrated for IGSO and MEO OSBs, while the consistency of GEO OSBs is worse by a factor of 2–3. The stability of the OSB estimates is at the level of 0.03–0.09 ns for GPS, 0.10–0.25 ns for Galileo, 0.14–0.48 ns for GLONASS, and 0.16–0.44 ns for BDS. In general, the BDS-3 OSB estimates show better stability than the BDS-2 OSBs. Moreover, the code biases at the same or at a close central frequency show similar performance. This is particularly obvious for Galileo and BDS, which adopt the dual-frequency constant envelope multiplexing (DCEM) technique. For instance, the code bias estimates of C5Q, C5X, C7Q, and C8Q are close to each other for individual Galileo satellites, and the BDS code biases of C5P, C7Z, and C8X are comparable to each other.

正确处理代码偏差对于实现精确的电离层建模，定位和定时至关重要。通常将差分模式下的代码偏差视为差分代码偏差（DCB）。随着GPS和GLONASS的现代化以及Galileo和BDS的实施，传统的DCB校准非常复杂，并且不易扩展到不同的频率和调制方式。代码偏差的另一种处理方法是使用可观察到的特定信号偏差（OSB）。在此贡献中，针对最新的GNSS估计了所有可能的OSB，并从精度，一致性和稳定性的角度进行了分析。GPS和Galileo OSB的精度明显优于GLONASS和BDS OSB。考虑GLONASS的频率间偏差（IFB）和BDS的系统间偏差（ISB）可以提高其OSB估计的精度。OSB在不同机构之间的比较显示，GPS和Galileo在0.2–0.3 ns的水平上显示出良好的一致性，而GLONASS和BDS OSB的差异达到0.5–1.0 ns。此外，IGSO和MEO OSB的一致性为0.4-0.5 ns，而GEO OSB的一致性则差了2-3倍。OSB估计的稳定性对于GPS为0.03-0.09 ns，对于Galileo为0.10-0.25 ns，对于GLONASS为0.14-0.48 ns，对于BDS为0.16-0.44 ns。通常，BDS-3 OSB评估显示出比BDS-2 OSB更好的稳定性。此外，在相同或接近中心频率处的代码偏差显示出相似的性能。对于Galileo和BDS来说，这一点尤其明显，它采用了双频恒定包络复用（DCEM）技术。例如，对于单个Galileo卫星，C5Q，C5X，C7Q和C8Q的代码偏差估计彼此接近，而C5P，C7Z和C8X的BDS代码偏差彼此可比。