Multi-GNSS triple-frequency differential code bias (DCB) determination with precise point positioning (PPP)
Multi-GNSS triple-frequency differential code bias (DCB) determination with precise point positioning (PPP)
复制标题
具有精确单点定位 (PPP) 功能的多 GNSS 三频差分码偏差 (DCB) 确定
DOI：
10.1007/s00190-018-1194-3
复制
发表时间：
2019-05-01
影响因子：
4.4
通讯作者：
Wang, Ningbo
中科院分区：
文献类型：
--
作者：
Liu, Teng;Zhang, Baocheng;Wang, Ningbo
差分码偏差（DCB）是利用GNSS观测值感测地球电离层时最重要的系统偏差，也是GNSS定位、导航和定时应用中的重要校正参数。随着美国GPS和俄罗斯GLONASS系统的不断现代化，以及欧洲Galileo和中国北斗系统的快速发展，对多星座和多频率的精密卫星DCB产品有着强烈的需求。本文提出了一种新的多GNSS三频DCB的精确定位方法，该方法分为三个步骤。第一步是精确地检索倾斜电离层延迟和额外的代码偏差的基础上新建立的满秩三频精密单点定位（PPP）模型与原始观测。需要估计包含DCB的倾斜电离层延迟和附加码偏差。在此基础上，利用改进的IGGDCB（IGG代表Institute of Geodesy and Geophysics）方法，利用PPP方法推导出的倾斜电离层延迟估计第一频段和第二频段之间的DCB。最后，将先前估计的第一和第二频带之间的DCB代入附加码偏中，估计第一和第三频带之间的DCB。从形式精度和零基线实验两个方面对三频PPP方法和传统双频载波码级（CCL）方法的多GNSS倾斜电离层延迟进行了比较。PPP和CCL方法的四次系统平均形式精度分别为0.08和0.41 TECU，表明PPP方法比CCL方法有明显的改进。选取全球分布的60个多GNSS实验站1个月的数据，对GPS、GLONASS、Galileo和北斗卫星系统共8种类型的DCB进行了估计。将该方法生成的多GNSS卫星DCB与欧洲轨道确定中心（CODE）、德国航空航天中心（DLR）和中国科学院（CAS）的产品进行了比较。对于GPS C1 WC 2 W DCB，对于DLR、CAS和IGG（本研究），CODE产品的RMS值分别为0.24、0.07和0.09ns。对于GPS C1 WC 5X和C1 WC 5 Q DCB以及相对于DLR/CAS，RMS值分别为0.31/0.25和0.19/0.15ns。对于GLONASS C1 PC 2 P DCB，DLR、CAS和IGG相对于CODE的RMS值分别为0.68、0.49和0.33 ns。对于Galileo，RMS值分别为0.16/0.20和0.13/0.14ns，对于C1 XC 5X和C1 XC 7 X DCB以及相对于DLR/CAS。对于北斗，C2 IC 7I和C2 IC 6 I DCB以及DLR/CAS，RMS值分别为0.32/0.25和0.34/0.41。仿真结果表明，该方法能够提供多GNSS和多频卫星DCB估计，具有较高的精度、处理效率和灵活性。
Differential code biases (DCBs) account for the most significant systematical biases when sensing the earth's ionosphere with GNSS observations and are also important correction parameters in GNSS applications of positioning, navigation and timing. With the continuous modernization of the American GPS and Russian GLONASS systems, and also the rapid developments of the European Galileo and Chinese BeiDou systems, there is a strong demand of precise satellite DCB products for multiple constellations and frequencies. This study proposes a new method for the precise determination of multi-GNSS triple-frequency DCBs, which can be divided into three steps. The first step is to precisely retrieve slant ionospheric delays and additional code biases based on a newly established full-rank triple-frequency precise point positioning (PPP) model with raw observations. Both the slant ionospheric delays and additional code biases containing the DCBs need to be estimated. Then, an enhanced IGGDCB (IGG stands for Institute of Geodesy and Geophysics) method is used to estimate the DCBs between the first and second frequency bands with the PPP-derived slant ionospheric delays. At last, the previously estimated DCBs between the first and second frequency bands are substituted into the additional code biases and DCBs between the first and third frequency bands are estimated. Multi-GNSS slant ionospheric delays from the triple-frequency PPP method are compared with those from the traditional dual-frequency carrier-to-code level (CCL) method, in terms of formal precision and zero-baseline experiment. Quad-system average formal precisions are 0.08 and 0.41 TECU, for PPP and CCL methods, respectively, indicating the obvious improvements of PPP over CCL. One month of data from 60 globally distributed multi-GNSS experiment stations are selected, and totally eight types of DCBs are estimated for GPS, GLONASS, Galileo and BeiDou. Multi-GNSS satellite DCBs generated with the proposed method are compared with the products from different agencies, including Center for Orbit Determination in Europe (CODE), Deutsches zentrum fur Luft-und Raumfahrt (DLR) and Chinese Academy of Sciences (CAS). For GPS C1WC2W DCBs, RMS values with respect to CODE products are 0.24, 0.07 and 0.09ns for DLR, CAS and IGG (this study), respectively. RMS values are 0.31/0.25 and 0.19/0.15ns, for GPS C1WC5X and C1WC5Q DCBs and with respect to DLR/CAS, respectively. For GLONASS C1PC2P DCBs, RMS values with respect to CODE are 0.68, 0.49 and 0.33ns for DLR, CAS and IGG, respectively. For Galileo, RMS values are 0.16/0.20 and 0.13/0.14ns, for C1XC5X and C1XC7X DCBs and with respect to DLR/CAS, respectively. For BeiDou, RMS values are 0.32/0.25 and 0.34/0.41, for C2IC7I and C2IC6I DCBs and with respect to DLR/CAS. These results show that the proposed method can provide multi-GNSS and multi-frequency satellite DCB estimation with high precision, processing efficiency and flexibility.