空间分析技术在研究传染病时空传播规律中的应用

以手足口病为例,介绍了地理信息的空间统计技术在传染病时空传播规律研究中的应用,包括传染病空间分布模式研究、传染病聚集性分析、传染病扩散传播模式分析、传染病发病率空间自相关分析及传染病发病率空间回归模型预测方面的研究,为传染病防治决策提供科学依据,具有一定的实用性。     

基于残差改正的动态非等时距灰色模型及应用

介绍了动态非等时距GM(1,1)模型的建模原理、建模过程以及精度评定方法,阐明了动态非等时距GM(1,1)模型中维度选择、残差改正的问题,结合高层建筑沉降监测实例进行分析,将动态非等时距残差GM(1,1)模型预测结果与实测值进行比较,得出动态非等时距残差GM(1,1)模型在建筑物沉降监测中具有很高预测精度的结论,证明了该方法的可行性与可靠性,适用于高层建筑沉降监测.     

CSS在国家古生物化石网站中的应用研究

针对国家古生物化石网站页面风格和信息类别的特点以及未来需要不断维护和改版升级的需求,研究认为,可以采取使用CSS样式表的方法来控制网页样式。主要技术路线是在创建网页代码时引入了CSS样式表,根据网站信息的特性设计出合理的字体和布局并储存在CSS样式表中再加以调用,使网页表现形式与信息内容相分离。经过开发测试和应用体验,采用此方法,不仅减少了大量冗余代码,减轻了服务器的负载,大大提高了页面的浏览速度,而且增加了网站的可维护性和可复用性。此方法还具有简单、实用、可复制的特点,网页构建和改版的工作效率将因此而提升。     

浅谈DEM的建立方法及应用

主要介绍DEM及其建立过程,研究DEM的特点及表示方法,并对不同的表示方法进行分析比对,重点介绍了DEM在地形曲面拟合、立体透视图、通视分析、计算地形属性等几个方面的应用,最后介绍这些应用在Map-GIS中的具体实现。     

Towards a 1 mGal accuracy and 1 min resolution altimetry gravity field

Over the past three decades, radar altimetry has made a significant contribution to marine gravity field modeling. To improve the accuracy and resolution, we propose a new twin-satellite altimetry. Such a system has several advantages. Among others, it provides (i) twice the number of samples per time epoch, and (ii) information about the cross-track surface gradient with high accuracy because most of the environmental and tidal errors will be common to the simultaneous measurements and therefore cancel out when computing the cross-track gradient computation. We describe a rigorous procedure for the deduction of the sea surface gradient at each altimeter observation point (i.e., not only at the crossovers), from the twin-satellite altimetry system. The precision of the gradient will be slightly affected by orbit errors, instrument drift, and inaccuracies in the geophysical corrections to be applied. We also demonstrate that a 1 mGal accuracy and 1 min resolution marine altimetry gravity field can be obtained if certain conditions are met. To achieve the expected goal, we recommend an orbital configuration, phasing two satellites in 4-s time delay such that the Earth rotation creates a natural baseline between the two satellites, and a 18 kHz SAR altimeter.     

基于网站群理念和架构的国家土地督察网站群建设实践

随着政府网站的建设和发展,网站群已成为电子政务发展的一种新模式。本文对立足于网站群理念和架构的国家土地督察网站群的建设实践进行了介绍,详解了国家土地督察网站群建设思想、建设原则、总体框架、技术路线、信息分类和栏目规划等。国家土地督察网站群为政府网站群的建设积累了有益经验。     

国土资源部门户网站信息资源整合体系研究

国土资源部门户网站是国土资源信息化建设的重要内容之一,历经10余年的发展建设,在服务国土资源管理决策和信息社会化需求方面发挥了较为重要的作用。本文围绕国土资源部门户网站信息资源整合建设实践,系统地阐述了网站的整合目标、原则、分类体系,着重介绍了系统架构、实现方法与建设成果。     

顾及用户体验的三维城市模型自适应组织方法

传统基于“图层付象”的组织方法,没有考虑三维城市模型的不同内容以及不同细节层次的粒度差异,导致在网络环境下的传输效率低,难以满足多用户并发访问的流畅可视化。深入分析了大范围漫游与小范围聚焦的用户体验特点,通过元数据统筹管理和对象离散化,即时响应用户请求,减少无效数据传输,保证了多用户并发环境下的高效调度和浏览。针对模型LoI)和分解的对象,设计了结构统一的对象ID,隐式存储关联关系并支持分布式模型存储管理。以分布式数据库MongoDB为平台进行实验,验证了本文方法的可行性和有效性。     

The determination of potential difference by the joint application of measured and synthetical gravity data: a case study in Hungary

In an elementary approach every geometrical height difference between the staff points of a levelling line should have a corresponding average g value for the determination of potential difference in the Earth’s gravity field. In practice this condition requires as many gravity data as the number of staff points if linear variation of g is assumed between them. Because of the expensive fieldwork, the necessary data should be supplied from different sources. This study proposes an alternative solution, which is proved at a test bed located in the Mecsek Mountains, Southwest Hungary, where a detailed gravity survey, as dense as the staff point density (~1 point/34 m), is available along a 4.3-km-long levelling line. In the first part of the paper the effect of point density of gravity data on the accuracy of potential difference is investigated. The average g value is simply derived from two neighbouring g measurements along the levelling line, which are incrementally decimated in the consecutive turns of processing. The results show that the error of the potential difference between the endpoints of the line exceeds 0.1 mm in terms of length unit if the sampling distance is greater than 2 km. Thereafter, a suitable method for the densification of the decimated g measurements is provided. It is based on forward gravity modelling utilising a high-resolution digital terrain model, the normal gravity and the complete Bouguer anomalies. The test shows that the error is only in the order of 10⁻³mm even if the sampling distance of g measurements is 4 km. As a component of the error sources of levelling, the ambiguity of the levelled height difference which is the Euclidean distance between the inclined equipotential surfaces is also investigated. Although its effect accumulated along the test line is almost zero, it reaches 0.15 mm in a 1-km-long intermediate section of the line.     

Phase center modeling for LEO GPS receiver antennas and its impact on precise orbit determination

Most satellites in a low-Earth orbit (LEO) with demanding requirements on precise orbit determination (POD) are equipped with on-board receivers to collect the observations from Global Navigation Satellite systems (GNSS), such as the Global Positioning System (GPS). Limiting factors for LEO POD are nowadays mainly encountered with the modeling of the carrier phase observations, where a precise knowledge of the phase center location of the GNSS antennas is a prerequisite for high-precision orbit analyses. Since 5 November 2006 (GPS week 1400), absolute instead of relative values for the phase center location of GNSS receiver and transmitter antennas are adopted in the processing standards of the International GNSS Service (IGS). The absolute phase center modeling is based on robot calibrations for a number of terrestrial receiver antennas, whereas compatible antenna models were subsequently derived for the remaining terrestrial receiver antennas by conversion (from relative corrections), and for the GNSS transmitter antennas by estimation. However, consistent receiver antenna models for space missions such as GRACE and TerraSAR-X, which are equipped with non-geodetic receiver antennas, are only available since a short time from robot calibrations. We use GPS data of the aforementioned LEOs of the year 2007 together with the absolute antenna modeling to assess the presently achieved accuracy from state-of-the-art reduced-dynamic LEO POD strategies for absolute and relative navigation. Near-field multipath and cross-talk with active GPS occultation antennas turn out to be important and significant sources for systematic carrier phase measurement errors that are encountered in the actual spacecraft environments. We assess different methodologies for the in-flight determination of empirical phase pattern corrections for LEO receiver antennas and discuss their impact on POD. By means of independent K-band measurements, we show that zero-difference GRACE orbits can be significantly improved from about 10 to 6 mm K-band standard deviation when taking empirical phase corrections into account, and assess the impact of the corrections on precise baseline estimates and further applications such as gravity field recovery from kinematic LEO positions.