A GNSS Time Offset Monitoring and Evaluation Method Based on BDT PPS Measurement
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摘要: 实时确定并获取不同GNSS时间基准之间的时间偏差(GNSS时差)是多GNSS联合导航定位授时的前提和基础。为了提高GNSS时差监测的精度并改进现有时差监测模型存在时延修正不完全等不足,本文提出一种基于BDT标准秒脉冲(1 PPS)信号测量的GNSS时差监测方法(改进的PPS方法),并设计了一种针对时差序列的评估分析策略。首先采用高性能设备构建时差监测硬件平台并进行时差监测链路的精确校准和修正,然后通过BDT的闭合监测进一步优化未完全消除的系统误差,最后基于相应的数据处理方法进行时差数据处理,实现了实时高精度的GNSS时差监测;此外,构建了一种能够同时考虑时差数据的时频特性与精度特性的评估策略,较为全面地分析了时差监测结果的性能。时差监测及其分析结果表明: 1)改进的PPS方法得到的BDT与GPST/GST/GLOT之间的时差测量不确定度优于3纳秒,其时差结果的精度比单点定位方法得到的时差结果的精度平均高出4倍; 2)所提时差评估策略能够顾及时差结果的时频特性、精度特性,实现更为全面系统评估分析; 3) BDT与其他GNSS时间基准保持了较好的一致性。Abstract: Objectives To determine and obtain the real-time system time offset between different global navigation satellite system time references (GNSS time offset) in real time is the premise and basis of multi-GNSS joint navigation, positioning and timing. In order to improve the accuracy of GNSS time offset monitoring and overcome the shortcomings of existing time difference monitoring models such as incomplete delay correction, we propose a GNSS time offset monitoring method (called the modified PPS method) based on a standard BeiDou Time (BDT) one pulse per second (1 PPS) signal measurement, and designs an evaluation and analysis strategy for the corresponding time offset data series. Methods Firstly, the hardware platform of time offset monitoring is built by assembling several high-performance equipment and the time offset monitoring link is accurately calibrated and corrected. Then, the system errors such as time delay are optimized through the closed monitoring of BDT. Finally, the time offset data is processed based on the designed data processing method. Thus, real-time and high-precision GNSS time offset monitoring is realized. In addition, an evaluation strategy that can consider both time-frequency characteristics and precision characteristics is constructed to comprehensively analyze the time offset monitoring results. Specifically, the accuracy of the time offset results and the variation between different GNSS time systems are analyzed by calculating the accuracy, drift rate, short-term stability (using modified Hadamard variance) of the time offset data series and the uncertainty of the corresponding fitting residual. Results The results of time offset monitoring and its corresponding analysis show that the uncertainty of time offset measurement between BDT and GPST/GST/GLOT obtained by the new method is better than 3 nanoseconds, and the accuracy of the new method is 4 times higher than that of the single point positioning method on average. The proposed strategy can consider the time-frequency characteristics and precision characteristics of the time offset results to achieve a more comprehensive system evaluation and analysis. Conclusions The modified PPS method can carry out reasonable and accurate calibration and correction of the time offset monitoring link, while the closed monitoring based on BDT can refine the systematic errors of the model and the designed data processing method can process the time offset data more accurately and reasonably. As a result, the method can realize real-time and high precision monitoring of GNSS time offset. Furthermore, the time offset results are evaluated and analyzed scientifically and effectively from different angles based on the proposed strategy. BDT keeps good consistency with other GNSS time references.
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Keywords:
- GNSS /
- Time Offset Monitoring /
- Pulses Per Second /
- Error Correction /
- Time Offset Evaluation
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