星载卫星导航反射信号与土壤湿度的时空相关性分析

Spatio-temporal Correlation Analysis of Spaceborne GNSS Reflection Signals and Soil Moisture

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 P r与土壤湿度 M v间的理论关系,然后将SMAP(soil moisture active passive)卫星获得的 M v作为标准值,在空间上选择两条轨迹的 P r与 M v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 P r和 M v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 P r与土壤湿度强相关。取春夏秋冬四个季节的数据,计算 P r与 M v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 P r与 M v有很强的相关性,具有估计土壤湿度的潜力。

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 technology demonstrate satellite-1(TDS-1) satellite as an example,firstly,the theoretical relationship between the reflected signal power( P r) and the soil moisture( M v) was derived,and then the M v obtained by the soil moisture active passive (SMAP)satellite was used as the standard value,in space,two trajectories of P r and M v were selected for Pearson correlation processing,the correlation coefficients on the two trajectories were 0.55 and 0.60,respectively.Then,in order to eliminate the noise,the smooth pretreatment of P r and M v was carried out,the correlation coefficients obtained were all increased to 0.71,that was,P r was strongly correlated with soil moisture.In addition,the data of the four seasons of spring,summer,autumn and winter were obtained,the correlation coefficient between P r and M v was calculated to be 0.78,which also showed strong correlation.The results show that P r obtained by on-board GNSS-Reflections (GNSS-R) receiver and M v have strong correlation and have the potential to estimate soil moisture.