星载卫星导航反射信号与土壤湿度的时空相关性分析

近年来使用GNSS(global navigation satellite system)反射信号反演土壤湿度已成为研究热点,使用星载反射计数据反演土壤湿度是一种有潜力的新兴技术。以TDS-1(technology demonstrate satellite-1)卫星接收的数据为例,首先推导出反射信号功率Pr与土壤湿度Mv间的理论关系,然后将SMAP(soil moisture active passive)卫星获得的Mv作为标准值,在空间上选择两条轨迹的Pr与Mv进行皮尔森相关处理,得到两条轨迹上的相关系数分别为0. 55和0. 60。之后对Pr和Mv分别进行相应的平滑预处理去除噪声,得到相关系数都增加为0. 71,即Pr与土壤湿度强相关。取春夏秋冬四个季节的数据,计算Pr与Mv的相关系数为0. 78,二者也表现为强相关。实验结果表明:星载(GNSS-reflections,GNSS-R)接收机得到的Pr与Mv有很强的相关性,具有估计土壤湿度的潜力。

Spatio-temporal correlation analysis of spaceborne GNSS reflection signals and soil moisture

In recent years, the use of Global Navigation Satellite System (GNSS) reflection signals to invert soil moisture has become a research hotspot, the use of spaceborne reflectometer data to invert soil moisture was a potential emerging technology. The paper took the data received by TechDemoSat-1 (TDS-1) satellite as an example, firstly, the theoretical relationship between Pr (the reflected signal power) and Mv (the soil moisture) was derived, and then the Mv obtained by the Soil Moisture Active Passive (SMAP)satellite was used as the standard value, in space, two trajectories of Pr and Mv were selected for Pearson correlation processing, the correlation coefficients on the two trajectories were 0.55 and 0.60, respectively. Then we carried out corresponding smoothing pretreatment for Pr and Mv respectively to remove the noise, the correlation coefficients obtained were all increased to 0.71, that was, Pr was strongly correlated with soil moisture. In addition, we took the data of four seasons: spring, summer, autumn and winter, and calculated the correlation coefficient between Pr and Mv was 0.78, which also showed strong correlation. The results show that Pr obtained by on-board GNSS-Reflections (GNSS-R) receiver and Mv have strong correlation and have the potential to estimate soil moisture.