提出了一种基于北斗GEO卫星反射信号的土壤湿度长期连续探测方法,建立了土壤湿度反演模型,给出了信号处理的一般流程,并搭建陆基接收平台进行了验证试验。该方法采用GNSS-R双天线体制接收处理北斗GEO卫星直射和土壤反射信号,在信号同步的基础上提取信号功率并计算土壤反射率,进而根据反演模型得到土壤湿度。以北斗GEO卫星作为信号源,该方法可以在信号处理中省去一般GNSS-R处理过程的定位解算环节,能够实现对固定区域土壤湿度的长期连续观测。试验结果表明,基于北斗GEO卫星反射信号的土壤湿度反演结果在时间和数值上均具有良好的连续性,与土壤湿度参考值相吻合,均方根误差达到0.049,较北斗IGSO和GPS MEO卫星在反演土壤湿度方面性能更优。
This paper proposes a method of continuous long-term soil moisture measurement using signals from BeiDou GEO satellites. It also presents the soil moisture inversion model as well as the relevant signal processing steps. Moreover, a land-based experiment is carried out to verify its validity. This method adopts the dual-antenna Global Navigation Satellite System Reflection (GNSS-R) mode to receive and process direct signal from BeiDou GEO satellites and reflected signal from soil. Based on signal synchronization, the reflectivity of soil can be calculated according to the extracted signal power values. And then, the soil moisture can be obtained in light of the inversion model. By taking singals from BeiDou GEO satellites, not only the positioning calculation step of general GNSS-R data processing can be ignored, but also a continuous long-term observation of soil moisture for fixed area can be realized. Experiment results based on the method above show a good continuity in both time and magnitude. They are also highly consistent with reference values and the root mean square error equals to 0.049. Compared with BeiDou IGSO and GPS MEO satellites, BeiDou GEO satellites can present a better performance in soil moisture retrieval.
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