EGNOS数据处理模型与实例

主要分析研究了EGNOS系统测试采用的误差修正模型和定位保护精度算法,并通过比较一次实测静态数据单点解算和差分解算的不同效果来说明误差模型的修正效果和保护精度算法的有效性。事实证明EGNOS系统数据处理采用的误差修正模型效果是明显的,采用的定位保护精度算法是有效的。     

大气流场的拓扑结构

用简化的大气运动方程,定性分析了大气中几种常见天气系统流场的拓扑结构. 研究表明,气旋反气旋流场与中心点附近的流形相对应;长波演化形成阻塞高压流场,与鞍点和中心点从合并到分离的流形相对应;台风和龙卷风的流场与三维空间中鞍-焦点附近的流形相对应. 研究大气流场的拓扑结构,可以直观清晰地揭示大气运动的形态和形成机理,有助于认识大气运动的规律. 文中讨论基于一定假设,结果与实际大气有差异,因而具有局限性.     

论相对点位精度的合理评定

按现行方法求得的相对点位精度由于未顾及起始数据误差的影响 ,且非实际所需评定的相对点位精度 ,因此并不客观、可靠。本文所提出的协方差基准的概念 ,用来定义相对点位精度和绝对点位精度有其客观性和实用性 ,协方差基准作为控制网点精度的参考基准 ,并不重合于网点坐标的参考基准—坐标基准 ,而可按应用的需要 ,方便地进行协方差基准转换。本文提出了合理评定相对点位精度的新方法 ,并用高精度工程控制网的实测数据进行了分析验证     

论《GIS空间分析》课程建设

综述了GIS空间分析理论的相关知识面和知识点,分析了课程的教学适应性,提出了课程建设的几点建议.     

An intelligent agent based on virtual geographic environment system

On the basis of previous work, this paper designs an intelligent agent based on virtual geographic environment (VGE) system that is characterized by huge data, rapid computation, multi-user, multi-thread and intelligence and issues challenges to traditional GIS models and algorithms. The new advances in software and hardware technology lay a reliable basis for system design, development and application.     

Virtual reality and its application to slide annimation of landslide

A few researches adopt virtual reality in landslide. So it is significant to combine the physicsbased deformable method with the process simulation of a sliding landslide, this way the dynamic process of a going landslide can be simulated. The analysis of the dynamic law of landslide provides a foundation to forecast and make it realiable to foretell disasters. After recounting the condition of VR and landsliding body simulation, this paper puts forward simulating landslide by the physics-based deformable method. The method divides landsliding into deformable body and rigid one. The deformation of deformable body can be compute by DDA and FEM, and DDA fits the great deformation and FEM is good for the tiny deformation. This paper shows it is feasible to simulate the landslide animation by this method.     

Image relaxation matching based on feature points for DSM generation

In photogrammetry and remote sensing, image matching is a basic and crucial process for automatic DEM generation. In this paper we presented a image relaxation matching method based on feature points. This method can be considered as an extention of regular grid point based matching. It avoids the shortcome of grid point based matching. For example, with this method, we can avoid low or even no texture area where errors frequently appear in cross correlaton matching. In the mean while, it makes full use of some mature techniques such as probability relaxation, image pyramid and the like which have already been successfully used in grid point matching process. Application of the technique to DEM generaton in different regions proved that it is more reasonable and reliable.     

1989年3月特强磁暴期间的电离层暴

用欧亚大陆地面电离层垂测站资料考察1989年3月12～16日磁暴期间的电离层暴形态及其发展变化. 特强磁暴引发的电离层暴是全球性的,但自磁层沉降的高能粒子对热层低部的加热程度及区域分布不同,因而各经度链区域内电离层暴的特征也有所差异. 本文研究表明,与理论推断对照,欧洲地区内F2层最大电子密度NmaxF2(或f0F2)并不出现正暴现象,而负暴自高纬向低纬的发展则与典型的热层环流结果相符. 此外,此磁暴过程期间在中低纬区存在明显的波动过程. 在亚洲高纬地区,磁暴初期13日有约10 h的正暴,而负暴过程则与欧洲地区类似,但不太清晰;且无波动现象. 磁暴期间,同一经度链的中低纬地区,夜间常发生多站同时的h′F突增. 本文再次证实这是一般磁暴期间常出现的普遍现象.     

关于大地电磁信号非最小相位性的讨论

由于信号的功率谱仅包含振幅信息而不包含相位信息,因此传统功率谱方法仅能处理最小相位信号,难于适用于非最小相位信号．本文对不同地区的实际大地电磁(MT)信号作了分析,结果表明,不同测点MT信号在Z平面上的零点分布并不全部位于单位圆之内,可以判定MT信号一般具有非最小相位的特点,因此有必要改进传统处理方法,发展新的资料处理方式．实际信号分析,理论和数值模型实验证明,信号的高阶统计量包含其相位信息,因此,高阶统计量方法能够有效处理具有非最小相位特征的MT信号．     

FY-3A/MERSI, ocean color algorithm, products and demonstrative applications

A medium resolution spectral imager (MERSI) on-board the first spacecraft of the second generation of China’s polar-orbit meteorological satellites FY-3A, is a MODIS-like sensor with 20 bands covering visible to thermal infrared spectral region. FY-3A/MERSI is capable of making continuous global observations, and ocean color application is one of its main targets. The objective is to provide information about the ocean color products of FY-3A/MERSI, including sensor calibration, ocean color algorithms, ocean color products validation and applications. Although there is a visible on-board calibration device, it cannot realize the on-board absolute radiometric calibration in the reflective solar bands. A multisite vicarious calibration method is developed, and used for monitoring the in-flight response change and providing post-launch calibration coefficients updating. FY-3A/MERSI ocean color products consist of the water-leaving reflectance retrieved from an atmospheric correction algorithm, a chlorophyll a concentration (CHL1) and a pigment concentration (PIG1) from global empirical models, the chlorophyll a concentration (CHL2), a total suspended mater concentration (TSM) and the absorption coefficient of CDOM and NAP (YS443) from China’s regional empirical models. The atmospheric correction algorithm based on lookup tables and ocean color components concentration estimation models are described. By comparison with in situ data, the FY-3A/MERSI ocean color products have been validated and preliminary results are presented. Some successful ocean color applications such as algae bloom monitoring and coastal suspended sediment variation have demonstrated the usefulness of FY-3A/MERSI ocean color products.