分类： 地球科学 >> 地球化学 提交时间： 2019-04-10
摘要： In the past two decades, Global Navigation Satellite System-Reflectometry (GNSS-R) has emerged as a new remote sensing technique for soil moisture monitoring. Some experiments showed that the antenna of V polarization is more favorable to receive the reflected signals, and the interference pattern technique (IPT) was used for soil moisture and other geophysical parameters retrieval. Meanwhile, the lower satellite elevation angles are most impacted by the multipath. However, electromagnetic theoretical properties are not clear for GNSS-R soil moisture retrieval. In this paper, the Advanced Integral Equation Model (AIEM) is employed using the wave synthesis technique to simulate different polarimetric scattering at the specular directions. Results show when the incidence angles are larger than 70º, scattering at RR polarization (The transmitted signal is Right Hand Circular Polarization (RHCP), while the received one is also RHCP) is larger than that one at LR polarization (The transmitted signal is RHCP, while the received one is Left Hand Circular Polarization (LHCP)), while scattering at LR polarization is larger than that at RR polarization for the other incident angles（1º~70º）. There is an apparent dip for VV and VR scattering due to the Brewster angle, which will result in the notch in the final receiving power and this phenomenon can be used for soil moisture retrieval or vegetation corrections. The volumetric soil moisture (vms) effects on their scattering are also presented. The larger soil moisture will result in lower scattering at RR polarization, and this is very different from the scattering of the other polarizations. It is interesting to note that the surface correlation function only affects the amplitudes of the scattering coefficients at much less level, but it has no effects on the angular trends of RR and LR polarizations.
分类： 地球科学 >> 大地测量学 提交时间： 2019-04-10
摘要： 目前，针对GNSS-R的研究多从观测角度出发，对其散射机理研究相对较少。本文针对GNSS-R（GNSS-Reflectometry）反射信号陆面参数的延迟多普勒图理论模型展开研究，对于陆面参数（裸土、植被）的双站散射特性的计算采用修改后的随机粗糙面散射模型和零阶/一阶辐射传输方程模型。通过该模型模拟分析了裸土、植被参数变化时，相应的延迟多普勒图的变化。同时为利用极化信息进行相应地物参数的后向反演，模型中增加全极化计算功能。全极化GNSS+R陆面参数延迟多普勒图理论模型的研究有助于星载数据的解释、地表实验设计、数据仿真和后向反演算法的开发。
分类： 地球科学 >> 大地测量学 提交时间： 2019-04-10
摘要： GNSS-R/IR是利用导航卫星反射信号对地观测的新方式，是国内外研究的热点技术。由于GNSS卫星群主要工作在穿透性比较强的L波段，因此适宜进行地表土壤水分监测。本文根据不同的遥感平台，详细叙述了地基、塔基、机载和星载GNSS-R技术土壤水分监测的发展现状，同时综述了辐射计联合GNSS-R技术进行土壤水分监测的发展状态以及GNSS-R地基和星载接收机的发展现状并探讨了GNSS-R/IR进行土壤水分反演的中的重点和难点内容。
分类： 地球科学 >> 大地测量学 提交时间： 2019-04-04
摘要： GNSS-R/IR（GNSS-Reflectometry/Interferometric Reflectometry)遥感是利用导航卫星反射信号或直射信号与反射信号的相干信号对地观测的新兴遥感方式，在国内外引起广泛关注。为将GNSS-R/IR技术的应用领域拓展到地表冻融状态的监测上，本文利用冻融土混合介质介电常数模型计算土壤介电常数，采用双站全极化相干反射率模型和随机粗糙面散射模型, 分别计算了经冻融土反射的GPS相干反射量的镜像反射率，以及GPS非相干反射分量的漫散射特性；并模拟分析了冻融转换时，GPS多路径信息（GNSS-IR）以及包含漫散射信号的延迟多普勒图（GNSS-R）的变化特征。理论研究表明冻融转换过程中，地表介电常数的变化导致GPS多路径信息和延迟多普勒图的明显变化。本文从散射机理上揭示了利用GNSS-R和GNSS-IR遥感进行地表冻融特性监测的理论依据。
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