据我国发布的《中国北极政策》白皮书（2018年）和《北极蓝皮书：北极地区发展报告》（2020年），近年来，随着全球气候变暖，冰川融化，极地地区的资源已进入实质性的开发阶段，极地地区的战略地位凸显，如何对极地资源开发与利用已成为国际社会关注的焦点之一。随着全球导航卫星系统（GNSS）的快速发展，精准快速的导航定位技术对极地的科学考察提供时空基准与安全保障，但极区地理位置特殊，电离层情况及磁场强度复杂多变等都会影响导航卫星信号的传播和接收。自2020年起，我国的北斗全球导航卫星系统（BDS-3）已正式为全球用户提供定位、导航与授时（PNT）等服务，及时地验证BDS-3在极区环境下的定位性能对极区后续的保障服务尤为重要。基于此，本文针对BDS-3在极地地区的数据质量和定位性能进行分析，为BDS-3在极地地区后续的PNT服务提供一定的参考。论文主要研究内容及结论如下：

（1）BDS-3在极区的数据质量分析。南北两极测站平均数据完整率为93.6%，B3I频点的数据完整率最高为94.5%优于其他频点，新频点B2b最低为90.8%，部分测站无法接收B2b频点；各测站间频点平均周跳频率在0.03~4.55之间；多路径误差平均为33.1cm，波动范围为23.2~48.1cm。同一站点，BDS-3新频点B1C频点多路径误差相对较小，波动较为稳定，其余四个频点相差不大；信噪比平均为45.1dB-Hz，波动范围为36.4dB-Hz ~48.4dB-Hz；MEO卫星的信噪比略优于IGSO卫星，同一类型卫星，B2b新频点信噪比优于其余四个频点，但部分测站无法接收B2b新频点。

（2）BDS-3在极区SPP与相对定位性能分析。BDS与GPS在极地地区可见星数均在8~14颗，PDOP值基本小于3，两系统大致相同。SPP方面，极地地区单频SPP定位精度中N、U方向最高为BDS-3 B1C频点，分别为0.6m、0.9m，E方向最高为GPS L1频点0.4m；双频BDS-3 B1C/B2a频点组合与GPS L1/L2组合IF模型定位精度相同均优于其他频点，E、N、U方向定位误差RMS均值分别为0.2m、0.2m、0.3m。极地地区BDS-3三个方向平均定位误差为0.8m、1.2m、1.5m，GPS三个频点平均为0.8m、1.1m、1.7m；极地地区BDS-3与GPS SPP定位性能相当。极地双频静态相对定位性能实验中，BDS-3短基线定位性能最优，模糊度固定率为99.13%，E、N、U方向定位精度相较于GPS分别提升4.35%、12.50%、17.86%，长基线相较于GPS分别提升了7.69%、6.06%、30.39%。BDS-3定位精度与模糊度固定率均优于GPS，E、N方向优于U方向。

（3）BDS-3在极区PPP性能分析。双频PPP，BDS-3在极地地区定位模型IF12定位精度相对于UC12在E、N、U方向提升了26.5%、22.8%、18.8%，收敛时间缩短了43.0%、58.0%、30.2%，B1I/B3I频点组合优于新频点B1C/B2a。GPS定位精度略优于BDS-3，BDS-3/GPS系统组合定位精度在E、N、U方向分别为1.0cm、0.8cm、1.2cm，收敛时间为5.4min、6.8min、8.2min，组合系统相较于单系统在定位精度和收敛时间上均有不同程度的提升。BDS-3在极区多频PPP性能分析。多频IF1213模型相较于双频IF12定位精度平均提升了8.1%，收敛时间平均缩短了15.8%。UC123相较于UC12定位精度和收敛时间分别改善了12.8%和16.1%，多频PPP定位性能优于双频PPP。多频GPS与BDS-3在收敛时间上大致相同，双系统组合多频定位精度与收敛时间分别为1.1cm、0.7cm、0.9cm和8.3min、5.3min、6.6min，优于双频双系统组合。新频点B1C/B2a/B3I组合收敛时间优于B1I/B2a/B3I，BDS-3多频PPP较双频PPP的提升幅度优于GPS。由于极区环境的特殊性，其比中低纬度地区卫星覆盖面更小，可见卫星数更低，数据质量更差，数据冗余度更低等导致BDS-3在中低纬度地区多频PPP性能优于极地地区，IF1213模型定位误差RMS平均改善48.6%，收敛时间平均缩短30.8%，UC123分别为36.1%和36.8%。

According to the white paper "China's Arctic Policy" (2018) and the "Arctic Blue Book: Arctic Region Development Report" (2020) released by China, in recent years, with global warming and melting glaciers, the resources of polar regions have entered a substantial stage of development, and the strategic position of polar regions has come to the fore, and how to develop and utilize polar resources has become one of the focal points of the international community. With the rapid development of Global Navigation Satellite System (GNSS), the accurate and fast navigation and positioning technology provides space-time benchmark and safety guarantee for scientific research in polar regions, but the special geographical location of polar regions, complex and variable ionospheric conditions and magnetic field strength will affect the propagation and reception of navigation satellite signals. Since 2020, China's BeiDou Global Navigation Satellite System (BDS-3) has been officially providing positioning, navigation and timing (PNT) services for global users, and timely verification of BDS-3's precision point positioning (PPP) performance in extreme environments is particularly important for the subsequent security services in polar regions. Based on this, this paper analyzes the data quality and PPP performance of BDS-3 in polar regions to provide some reference for the subsequent PNT services of BDS-3 in polar regions. The main research contents and conclusions of the paper are as follows:

(1) Data quality analysis of BDS-3 in polar regions. The average data integrity rate of the north and south polar stations is 93.6%, the highest data integrity rate of B3I frequency point is 94.5% better than other frequency points, the lowest data integrity rate of the new frequency point B2b is 90.8%, some stations cannot receive B2b frequency point, the data integrity rate of each station can better reflect the consistency of BDS satellite, the average weekly hopping frequency of frequency points between stations is between 0.03~4.55, the average multipath error is 33.1cm, fluctuating in the range of 23.2~48.1cm. At the same station, the multipath error of the new BDS-3 frequency point B1C is relatively small and stable, while the remaining four frequency points are not very different. The signal-to-noise ratio is 45.1dB-Hz on average, and the fluctuation range is 36.4dB-Hz ~48.4dB-Hz. The signal-to-noise ratio of MEO satellite is slightly better than that of IGSO satellite, and the signal-to-noise ratio of B2b new frequency point is better than the remaining four frequency points in the same type of satellite, but some stations cannot receive B2b new frequency point.

(2) Analysis of SPP and relative positioning performance of BDS-3 in polar region. Both BDS and GPS have 8-14 visible stars in the polar region, and the PDOP value is basically less than 3. The two systems are roughly the same; In SPP positioning, the highest accuracy of single frequency SPP in polar region is BDS-3 B1C frequency point in N and U direction, which are 0.6m and 0.9m respectively, and the highest GPS L1 frequency point is 0.4m in E direction. Dual frequency BDS-3 B1C/B2a frequency combination and GPS L1/L2 combination IF model have the same positioning accuracy than other frequency points, and the mean RMS of positioning errors in E, N and U directions are 0.2m, 0.2m and 0.3m, respectively. The average positioning error of BDS-3 in three directions in polar region is 0.8m, 1.2m and 1.5m, and the average positioning error of GPS three frequency points is 0.8m, 1.1m and 1.7m. The polar region BDS-3 has comparable positioning performance to GPS SPP. In the polar dual-frequency static relative positioning performance experiment, BDS-3 short baseline positioning performance is the best, the ambiguity fixed rate is 99.13%, the positioning accuracy of E, N and U directions is improved by 4.35%, 12.50% and 17.86% compared with GPS, and the positioning accuracy of long baseline is improved by 7.69%, 6.06% and 30.39% compared with GPS, respectively. BDS-3 positioning accuracy and ambiguity fixed rate are better than GPS, E, N direction is better than U direction.

(3) Analysis of BDS-3's positioning performance in the polar region. dual-frequency PPP ，the positioning accuracy of BDS-3 in the polar region is improved by 26.5%, 22.8%, and 18.8% in the E, N, and U directions relative to UC12, and the convergence time is shortened by 43.0%, 58.0%, and 30.2%, and the B1I/ B3I frequency combination is better than the new frequency B1C/B2a. The GPS positioning accuracy is slightly better than BDS-3, and the combined BDS-3/GPS system positioning accuracy is 1.0cm, 0.8cm, and 1.2cm in the E, N, and U directions, respectively, with convergence times of 5.4min, 6.8min, and 8.2min. The combined system has different degrees of improvement in positioning accuracy and convergence time compared with the single system. BDS-3 performance analysis of multi-frequency PPP in the polar region.The multi-frequency IF1213 model improves the positioning accuracy by 8.1% on average and shortens the convergence time by 15.8% on average compared with the dual-frequency IF12. UC123 improves the positioning accuracy and convergence time by 12.8% and 16.1% respectively compared with UC12, and the multi-frequency PPP positioning performance is better than the dual-frequency PPP. Multi-frequency GPS is approximately the same as BDS-3 in terms of convergence time, the dual system combination’s multi-frequency positioning accuracy and convergence time are 1.1cm, 0.7cm, 0.9cm and 8.3min, 5.3min, 6.6min, respectively, which are better than the dual-frequency dual-system combination. The convergence time of the new frequency B1C/B2a/B3I combination is better than that of B1I/B2a/B3I, and the improvement of BDS-3 multi-frequency PPP over dual-frequency PPP is better than that of GPS. Due to the particularity of the polar environment, the satellite coverage in the polar region is smaller, the number of visible satellites is lower, the data quality is worse, and the data redundancy is insufficient. As a result, the performance of BDS-3 multi-frequency PPP is better than that of polar regions in the middle and low latitudes, and the IF1213 model has an average improvement of 48.6% in positioning error RMS and an average reduction of 30.8% in convergence time. UC123 is 36.1% and 36.8%.

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