随着GNSS应用的扩展，全球卫星导航系统反射（GNSS-R）技术已成为潮位监测的重要技术手段之一。本文基于非洲东海岸的MAYG站2019-2020年的观测数据，利用导航卫星信号的信噪比（SNR）的变化来反演天线相位中心到海平面的垂直距离，通过高程基准转换归算到以zero_hydrographic为基准的潮位高度，并与DZAOUDZI验潮站提供的实测潮位高度进行对比。本文具体研究内容如下：

（1）简介GPS、GLONASS、Galileo和BDS四大导航卫星系统，结合SNR与多路径的关系详细介绍GNSS-R技术监测潮位的基本理论，并阐述LSP谱分析的原理。

（2）基于GNSS-R技术融合多系统多SNR进行潮位监测时，为剔除监测结果的冗余性，将同一时刻不同SNR类型反演结果取均值。通过2020年DOY300和DOY321-DOY327潮位监测的实验，验证潮位监测的可行性与周期性。基于2019-2020年潮位监测的实验，验证潮位监测的可靠性与连续性。连续两年的实验结果表明，每天监测数量的中值增加到58，每天每两次有效潮位监测的时间间隔的中值缩减到16.00min，时间分辨率显著提高，监测的海平面高度的数量总计41860个，平均误差为0.0268m，相关系数为0.9130，均方根误差为0.4022，验证了GNSS-R技术监测的潮位与验潮站实测的潮位具有较好的相关性。

（3）研究了2019-2020年不同系统不同SNR类型监测潮位的精度，GPS的精度对比为S5X>S2X>S1C>S2W，GLONASS的精度对比为S1P>S2P>S1C>S2C，Galileo的精度对比为S8X>S7X>S5X>S1X，BDS2-IGSO卫星的精度对比为S7I>S6I>S2I，BDS2-MEO卫星的精度对比为S7I>S6I>S2I，BDS3-MEO卫星的精度对比为S6I>S2I。2020年DOY268-DOY366接收机型号由TRIMBLE NETR9替换成了TRIMBLE ALLOY，需要对新增的SNR类型以及BDS3卫星进行精度分析。通过实验分析可得，GPS的精度对比为S5X>S2X>S2W>S1C>S1X，Galileo的精度对比为S6X>S1X>S7X>S5X>S8I，BDS2-IGSO的精度对比为S7I>S6I>S2I，BDS2-MEO的精度对比为S7I>S2I>S6I，BDS3-IGSO的精度对比为S1X>S6I>S5X>S2I，BDS3-MEO的精度对比为S6I>S5X>S1X>S2I。BDS2和BDS3的精度对比为BDS3-MEO>BDS2-MEO>BDS2-IGSO>BDS3-IGSO。

（4）通过BDS-R的研究实验可得，BDS-GEO卫星高度角没有变化，无法用于岸基测高；BDS-IGSO的卫星轨道持续时间比其他卫星星座更长，消除了快速变化的潮汐，潮位监测精度明显要差；BDS3-MEO的潮位监测精度优于其他各个系统的精度。

With the expansion of GNSS applications, Global Navigation Satellite System Reflection (GNSS-R) technology has become one of the important technical means for sea level monitoring. Based on the observation data of the MAYG station on the east coast of Africa in 2019-2020, the SNR of the navigation satellite signal is used to invert the vertical distance from the antenna phase center to the sea level, and then converted to the height based on zero_hydrographic through the elevation reference conversion. Then, it is compared with the measured tide height provided by the DZAOUDZI tide gauge station. The specific research content of this paper is as follows:

(1) The four navigation satellite systems of GPS, GLONASS, Galileo and BDS are introduced. Combining the relationship between SNR and multipath, the basic theory of GNSS-R technology to monitor tide level is introduced and the principle of LSP spectrum analysis is explained.

(2) When tide level monitoring is performed based on GNSS-R technology fusion of multiple system and multiple SNR, in order to eliminate the redundancy of the monitoring results, the inversion results of different SNR types at the same time are averaged. Through the tide level monitoring experiments in DOY300 and DOY321-DOY327 of 2020, the feasibility and periodicity of tide level monitoring are verified. Simultaneously, based on the experiment of tide level monitoring in 2019-2020, the reliability and continuity of tide level monitoring are verified. The experimental results for two consecutive years show that the median of the number of daily monitoring has increased to 58, the median of the effective tide level monitoring interval twice a day has been reduced to 16.00 min, and the time resolution has been significantly improved. The number of monitored tide level is 41860, with an average error of 0.0268m, a correlation coefficient of 0.9130, and a root mean square error of 0.4022, which verifies that the tide level monitored by the GNSS-R technology has a good correlation with the tide level measured by the tide gauge station.

(3) The accuracy comparison of different SNR types of different systems in 2019-2020 is studied. The accuracy comparison of GPS is S5X>S2X>S1C>S2W, the accuracy comparison of GLONASS is S1P>S2P>S1C>S2C, and the accuracy comparison of Galileo is S8X>S7X>S5X>S1X, the accuracy comparison of BDS2-IGSO satellite is S7I>S6I>S2I, the accuracy comparison of BDS2-MEO satellite is S7I>S6I>S2I, and the accuracy comparison of BDS3-MEO satellite is S6I>S2I. In DOY268-DOY366 of 2020, the receiver model is replaced from TRIMBLE NETR9 to TRIMBLE ALLOY. It is necessary to analyze the accuracy of the newly added SNR types and BDS3 satellites. Through experimental analysis, the accuracy comparison of GPS is S5X>S2X>S2W>S1C>S1X, the accuracy comparison of Galileo is S6X>S1X>S7X>S5X>S8I, the accuracy comparison of BDS2-IGSO is S7I>S6I>S2I, the accuracy comparison of BDS2-MEO is S7I>S2I>S6I, the accuracy comparison of BDS3-IGSO is S1X>S6I>S5X>S2I, and the accuracy comparison of BDS3-MEO is S6I>S5X>S1X>S2I. The accuracy comparison between BDS2 and BDS3 is BDS3-MEO>BDS2-MEO>BDS2-IGSO>BDS3-IGSO.

(4) Through the research experiment of BDS-R, it can be obtained that the elevation angle of BDS-GEO satellite has almost no change and cannot be used for shore-based altimetry. BDS-IGSO satellite orbit duration is longer than other satellite constellations, which eliminate the rapidly changing tides, and the accuracy of tide level monitoring is obviously poor. The tide level monitoring accuracy of BDS3-MEO is better than that of other systems.

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