利用北斗导航卫星信号估算土壤水分的方法研究

Using the L-band microwaves broadcasted by the Global Navigation Satellite System (GNSS) to estimate soil moisture has become a heated science topic in recent years. China’s Beidou Navigation Satellite System (BDS) is expected to bring more capabilities as well as challenges in this field. This proposal, focusing on using the BDS signals of high temporal resolution received by the ground-based GPS/Beidou compatible receivers, aims to propose approaches for estimating the volumetric soil moisture content (VSM) under both bare soil and vegetated soil conditions. Specific tasks include how to: 1) investigate the theories of the multipath interference between the direct and the ground-reflected BDS signals recorded by the signal-to-noise ratio (SNR) data, and subsequently extract the two interferogram metrics (phase and amplitude); 2) develop an approach to estimate the VSM for bare soil using the interferogram metric phase extracted in 1); and 3) consider the vegetation effects on soil and further develop a modified approach to estimate the VSM for vegetated soil, using the two interferogram metrics (phase and amplitude) extracted in 1). The research achievements will provide theoretical basis and methodologies for soil moisture estimation using data collected by China’s own navigation satellite system, and will technically support the development of GNSS-derived soil moisture products and the validation of the soil moisture products provided by other satellite sensors.

利用全球覆盖全天候的导航卫星信号进行土壤水分估算是近年来国际研究的前沿和热点。我国亟需开展利用自主北斗卫星导航系统估算土壤水分的方法研究。本项目面向国际研究前沿及国家自主导航卫星应用需求，利用北斗地基站接收的高时间分辨率L波段微波信号，研发一套针对北斗卫星的裸土、植被覆盖地表土壤水分估算方法。首先，分析北斗系统特有的轨道及信号特征，基于地基测站北斗卫星信号信噪比(SNR)数据的干涉测量建模理论，研究SNR干涉波形相位和振幅的提取方法；然后，在此理论基础上，研究利用北斗SNR干涉测量相位进行裸土地表土壤水分估算的方法；最后，根据植被微波辐射传输理论，进一步研究考虑植被影响去除的植被覆盖地表土壤水分估算方法。本项目的研究成果将为我国自主导航卫星信号用于土壤水分估算提供理论和方法支持，还将为基于地基北斗/GPS双模测站的土壤水分产品研发、遥感水文气象应用、土壤水分卫星遥感产品验证等开辟新途径。

利用全球覆盖全天候的导航卫星信号进行土壤水分估算是近年来国际研究的前沿和热点。我国亟需开展利用自主北斗卫星导航系统估算土壤水分的方法研究。本项目面向国际研究前沿及国家自主导航卫星应用需求，利用北斗地基站接收的高时间分辨率L波段微波信号，研发一套了针对北斗卫星的裸土、植被覆盖地表土壤水分估算方法。项目主要研究成果总结如下：.1）提出并实现了地基测站北斗卫星信号信噪比SNR数据干涉测量建模方案；.2）针对裸土地表：提出了一种新的GNSS卫星干涉测量建模方法；提出并验证了基于北斗SNR干涉测量相位的裸土土壤水分估算模型；.3）针对植被覆盖地表：提出并验证了基于北斗SNR干涉测量振幅和相位的植被覆盖地表土壤水分估算模型；.4）基于研究成果1）2）3），提出并验证了基于北斗SNR的陆表多要素（土壤水分、植被含水量、积雪深度）综合反演方法，作为本项目研究内容的深入和拓展。. 本项目的研究成果将为我国自主导航卫星信号用于土壤水分估算提供理论和方法支持，还将为基于地基北斗/GPS双模测站的土壤水分（延伸至植被含水量、积雪深度）产品研发、遥感水文气象应用、卫星遥感产品验证等开辟新途径。