A constrained LAMBDA method for GPS attitude determination

An improved method to obtain fixed integer ambiguity in GPS attitude determination is presented. Known conditions are utilized as constraints to acquire attitude information when the float solution and its variance–covariance matrix are not accurate enough. The searching ellipsoidal region is first expanded to compensate for errors caused by the inaccurate float solution. Then the constraints are used to shrink the region to a proper size, which maintains the true integer ambiguity. Experimental results demonstrate that this scheme gives a fast search time and a higher success rate in determining the fixed integer ambiguity than the unconstrained method. The accuracy of attitude angles is also improved.

基于WebGIS定制平台的开发与应用

基于柔性设计、定制及框架技术,形成应用型WebGIS定制平台的概念及框架,提炼了平台的高柔性、多粒度功能复用、充分可定制三大特点,进行了数据定制与配置、界面定制与配置、功能定制与配置等功能的研究与设计。基于WebGIS定制平台的开发与应用实践证明:该开发模式实现了多个WebGIS应用系统的敏捷开发,较好地支持了数据共享、功能复用与界面的一致性。     

ERS-2 SAR反演海洋风矢量的研究

SAR(Synthetic Aperture Radar)反演海洋风矢量是当今微波遥感领域非常有意义的前沿课题. 本文首先介绍了星载SAR估算海面风向、风速的基本原理和三种主流反演算法,接着给出反演的流程图以及重要步骤. 然后,以2002年5月7日香港地区ERS-2 SAR海洋图像为例,对经典的SWDA (SAR Wind Direction Algorithm)－谱分析方法加以改进,求得具有180°模糊度的风向,并用香港天文台气象浮标实测数据消除了风向不确定性. 最后,利用CMOD4 GMF（Geophysical Model Function,地球物理模式函数）计算得到海面上10m高的风速. 与气象浮标站实测资料相比,利用ERS-2 SAR图像获取的海面风向、风速的精度均较高. 这一结果表明：如果对SAR预先进行ADC(Analog to Digital Converter)改正以及精确校准,结合改进的SWDA和CMOD4,可以获得高精度的风矢量.     

不同规格化的引潮位展开及其转换

引入完全规格化的缔合勒让德函数,阐述国际上两类不同规格化的引潮位展开,使引潮位函数表达更加简明,大地系数定义更加规范. 由此得到由Doodson规格化与Hartmann & Wenzel规格化之间的转换系数.     

住房成本与通勤成本的空间互动关系——来自北京市场的微观证据及其宏观含义

住房成本和通勤成本是城市空间结构中两个相互关联的内生变量。居民在进行居住区位 选择时, 会在这两者之间进行权衡, 从而形成住房价格、建筑密度和通勤行为在空间上的变化规 律。本文回顾了通勤成本和住房成本间的理论均衡关系, 探讨了各种现实情况是如何影响这个理 论关系的; 并利用大规模调研所采集的北京市微观个体数据, 提供了这一互动关系的一些定量证 据; 最后从两个角度探讨了这种互动关系在城市管理的公共政策方面的宏观含义: 考虑通勤成本 后的住房支付能力评价, 以及就业与居住过度分离的社会效果分析。     

地方政府官方旅游网站营销功能实证分析

在线营销已成为信息时代目的地整体营销战略的重要组成部分,考察目的地营销网站的发展状况有助于目的地营销组织审视其在线营销活动。以中国内地31个省为例,将营销战略、信息服务、交易处理、技术支持和网站运营作为一级指标,对官方旅游网站的营销功能进行评估。结果表明,目前国内目的地营销网站功能已无显著地区差异,大部分网站处于信息提供的初级发展阶段,目的地营销战略实施、交易处理等功能尚需改进;地方官方网站营销功能的充分发挥有赖于各级政府的支持,目的地在线营销的发展必须与目的地整体营销战略相整合。     

Screening the current soil drainage class map of Flanders (Belgium) for its predictive quality

The predictive quality of the current drainage class map of Flanders was evaluated using data from two monitoring networks: one with good spatial coverage but poor temporal coverage and another with better temporal but poor spatial coverage. We combine both networks to obtain 1678 point predictions for mean highest water (MHW) and mean lowest water (MLW) tables by applying time series modelling and total least squares regression. The resulting MHW and MLW point data set was used to evaluate the currency of the existing map and to identify regional differences. The quality of the current map is moderate, and large differences occur between regions. Especially the Campine region shows large and systematic differences, whereas the southeastern hills and chalk–loam region is relatively accurate. If more weight is given to errors in the wetter drainage classes, about 50% of the area of Flanders would benefit from remapping. Copyright © 2011 John Wiley & Sons, Ltd.     

Analytical and computational procedure for solving the consolidation problem of layered soils

One‐dimensional consolidation analysis of layered soils conventionally entails solving a system of differential equations subject to the flow conditions at the bounding upper and lower surfaces, as well as the continuity conditions at the interface of every pair of contiguous layers. Formidable computational efforts are required to solve the ensuing transcendental equations expressing the matching conditions at the interfaces, using this method. In this paper, the jump discontinuities in the flow parameters upon crossing from one layer to the other have been systematically built into a single partial differential equation governing the space–time variation of the excess pore pressure in the entire composite medium, by the use of the Heaviside distribution. Despite the presence of the discontinuities in the coefficients of the differential equation, a closed‐form solution in the sense of an infinite generalized Fourier series is obtained, in addition to which is the development of a Green's function for the differential problem. The eigenfunctions of the composite medium are the coordinate functions of the series, obtained computationally through the application of the extended equations of Galerkin. The analysis has been illustrated by solving the consolidation problem of a four‐layer composite, and the results obtained agree very well with the results obtained by previous researchers. Copyright © 2013 John Wiley & Sons, Ltd.     

Accounting for sparsely observed rainfall space—time variability in a rainfall—runoff model of a semiarid Tunisian basin/Prise en compte d'observations peu denses de la variabilité spatiotemporelle de la pluie dans une modélisation pluie—débit d'un bassin semi-aride Tunisien

Abstract

The management of water excesses and deficits is a major task in semiarid Mediterranean regions, where the variability of rainfall inputs is high at different time and space scales. Thus intense hydrometeorological events, which generate both potential resource and hazards, are of major interest. A simple method is proposed, with the example of the Skhira basin (192 km²) in central Tunisia, to account for the event space–time variability of rainfall in a rainfall–runoff model, in order to check its influence on the shape, magnitude and timing of resulting hydrographs. The transfer function used is a geomorphology-based unit hydrograph with an explicit territorial significance. Simulations made for highly variable events show the relevance of this method, seen as the first step of a downward approach, and its robustness with respect to the quality and the density of rainfall data.