土壤水分是气象预报、农情监测以及水文模型的重要参数之一,利用被动微波遥感技术可以有效获取土壤水分。欧空局(ESA)计划于2009年发射卫星SMOS(Soil Moisture and Ocean Salinity),其主要目的是监测全球范围内的土壤水分和海洋盐度变化。根据SMOS的设置情况,寻找精度较高的半经验模型以便为进一步的土壤水分反演提供简化模型。对于裸露地表,地表粗糙度、土壤介电常数等因素影响最终的微波发射率。运用Dobson半经验介电常数模型计算土壤的介电常数,将计算结果输入高级积分方程模型(AIEM)。通过AIEM模拟的数据库,利用回归关系建立了一个精度相对较高的L波段多角度半经验模型。
[Objective] The aim was to compare and analyze microwave coherent and incoherent scattering models in a corn field. [Method] In the research, based on a coherent scattering model （Stile）, we proposed a coherent scattering model exclusive for corn, in which, physical optics （PO） and infinite-length dielectric cylinder were used to calculate single-scattering matrices of corn leaves and stalks. In addition, coherent components produced from interaction among the scattering mechanisms were also considered and this coherent model was compared with the Michigan Mi- crowave Canopy Scattering （MIMICS） model. The measured data in a corn filed in Gongzhuling in Jilin Province were used as the input parameters of the coherent and incoherent models. We simulated backscattering coefficients of VV and HH po- larization at L and C bands and made a comparison between the simulation results. [Result] The simulation results at L-band were poor, which indicated that we could not find regularity at early growth stage of vegetation. In addition, comparisons be- tween coherent and incoherent scattering models proved that the coherence triggered by the scattering mechanism was small. [Conclusion] In the research, we analyzed differences between coherent and incoherent scattering models with change of incident angle, and further analysis on the differences with change of vegetation and soil needed to be made in future.
数字高程模型(DEM)是进行三维分析的核心数据,其在诸多领域起着辅助设计与决策的作用。随着多尺度DEM数据的急剧增多,要求对DEM数据进行高效存储与管理,同时对DEM数据的安全、快速、实时的多用户访问提出了要求,空间数据库的管理模式是适应这种要求的最佳解决方案。对多尺度DEM数据库内容进行了详细分析;通过对空间数据库技术的各类方案进行对比,选用ArcSDE for SQL Server进行建库工作,实现了空间数据与属性数据的统一存储;采用Arc Engine(AE)开发方式开发了数据库管理系统,并以实验地区的DEM数据库系统建设为例,完成了数据库基本操作功能模块的开发与设计,实现了各类数据的查询、浏览和管理功能。
