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利用GNSS-R(Global Navigation Satellite System-Reflectometry)技术探测土壤水分是近年来一个新兴的研究方向。目前GNSS-R遥感观测中反射信号的接收与处理方式包括单天线与多天线两种模式,面向实际应用需求,GNSS-R遥感正在实现从最初的地基观测向空基、星载观测的转变。在推进GNSS-R土壤水分遥感技术业务化应用的过程中,必须首先进行适宜性分析,确定该技术探测的地理位置、空间分辨率与探测深度,然而目前对此尚未有系统、全面、定量的论述。本文针对适宜性分析中的3个关键因子分别进行理论分析与公式推导,明确相关概念的定义,并实现定量化描述,最终通过实际应用分析进一步诠释其应用价值。对于单天线模式地基观测,以美国板块边界观测计划PBO(Plate Boundary Observatory)土壤水分产品为例,分析镜面反射点的相对位置、第一级Fresnel反射椭圆簇的面积与时间序列土壤水分所代表的探测深度;对于多天线模式,以郑州上街区农田空基观测试验为例,得到基于航迹的栅格土壤水分空间分布并探讨其探测深度。本文能够为未来两种观测模式下地基、空基和星载GNSS-R遥感观测、北斗反射信号遥感,以及GNSS-R在农业、水文、生态等领域的实际应用提供理论指导。
The use of GNSS-R (Global Navigation Satellite System-Reflectometry) technology to detect soil moisture is an emerging research direction in recent years. At present, the methods of receiving and processing reflected signals in GNSS-R remote sensing observations include single-antenna and multi-antenna modes. For the practical application, GNSS-R remote sensing is transforming from initial ground-based observations to space-based and on-space observations. In promoting the operational application of GNSS-R soil moisture remote sensing technology, the suitability analysis must first be carried out to determine the geographic location, spatial resolution and exploration depth of the technology. However, there is no systematic, comprehensive and quantitative Discussion. In this paper, three key factors in suitability analysis were theoretical analysis and formula derivation, define the definition of the relevant concepts, and to achieve a quantitative description of the final practical application of the analysis and further interpretation of its value. For single-antenna ground-based observation, taking the Plate Boundary Observatory (PBO) soil moisture product as an example, the relative position of the specular reflection points is analyzed. The area of the first-order Fresnel reflection elliptic cluster is proportional to the time series of soil moisture For the multi-antenna mode, the space-based observation of farmland in Zhengzhou Shangjie District is taken as an example to obtain the spatial distribution of soil moisture on the grid based on the track and to explore its detection depth. In this paper, we can provide theoretical guidance for the practical application of GNSS-R remote sensing in space, space-based and spaceborne systems, remote sensing of Beidou reflected signals, and the practical application of GNSS-R in agriculture, hydrology and ecology in the two future observation modes.