地图综合中的地图目标自相似性分形衰减研究

分形衰减是指在地图综合中,地图目标随着比例尺的变化其结构形态随之发生改变,其自相似程度是递减变化的,反应到分维数的变化上,称之为分形衰减。本文以分形分析方法作为工具,分维值作为度量参数,分析地图综合中地图目标的分形衰减现象。以扩展分维作为理论基础,从变维分析的角度出发,研究地图目标的自相似程度随比例尺变化而衰减的规律,进一步研究地图目标的尺度指标与分形衰减之间的关系。     

基于GIS的福州应急避难所空间格局评价

日益凸显的突发性自然灾害对城市应急管理提出了更高的要求,应急避难所是其重要基础设施之一.本研究利用福州市社区尺度的人口统计数据建立高精度的人口密度分布图,根据应急避难所的容纳人数与人口密度图动态缓冲区分析计算其服务能力空间范围,对研究区内21个避难所的空间格局进行评价.结果表明,福州城区避难所建设数量不足,空间分布不均,人口服务辐射能力弱.针对福州城区避难所空间分布现状,分析了主要的影响因素,对福州城区应急避难场所选址提出了进一步优化建议,认为在人口分散区的避难所应该增加数量,适当减小规模;而在人口稠密区则可增加规模适中的避难所建设.     

Review of the Kalman-type hydrological data assimilation

ABSTRACT

There is great potential in Data Assimilation (DA) for the purposes of uncertainty identification, reduction and real-time correction of hydrological models. This paper reviews the latest developments in Kalman filters (KFs), particularly the Extended KF (EKF) and the Ensemble KF (EnKF) in hydrological DA. The hydrological DA targets, methodologies and their applicability are examined. The recent applications of the EKF and EnKF in hydrological DA are summarized and assessed critically. Furthermore, this review highlights the existing challenges in the implementation of the EKF and EnKF, especially error determination and joint parameter estimation. A detailed review of these issues would benefit not only the Kalman-type DA but also provide an important reference to other hydrological DA types.

Editor D. Koutsoyiannis; Associate editor F. Pappenberger     

Paramater regimes for studying isolated eddies

Abstract

The parameter ranges relevant to propagating oceanic eddies are explored with a view to simplifying the equation sets previously used to simulate such eddies. The reduced gravity shallow-water model is used as a starting point. We consider eddies whose width is of the same order as, or somewhat larger than, the Rossby deformation radius. Two model equations emerge from these scalings, both permitting modon solutions and easy numerical integration. Both, too, give fair simulations of the shallow-water model, but disagree in details.

Using another approach, an ad hoc vortex model is used to predict the path of an eddy. This also gives a fair but not perfect simulation of the one-layer results. It appears that the only ideal way to reproduce primitive equation results accurately is to use the primitive equations themselves.     

Improving long-range hydrological forecasts with extended Kalman filters

Abstract

There is a continuing effort to advance the skill of long-range hydrological forecasts to support water resources decision making. The present study investigates the potential of an extended Kalman filter approach to perform supervised training of a recurrent multilayer perceptron (RMLP) to forecast up to 12-month-ahead lake water levels and streamflows in Canada. The performance of the RMLP was compared with the conventional multilayer perceptron (MLP) using suites of diagnostic measures. The results of the forecasting experiment showed that the RMLP model was able to provide a robust modelling framework capable of describing complex dynamics of the hydrological processes, thereby yielding more accurate and realistic forecasts than the MLP model. The performance of the method in the present study is very promising; however, further investigation is required to ascertain the versatility of the approach in characterizing different water resources and environmental problems.

Citation Muluye, G. Y. (2011) Improving long-range hydrological forecasts with extended Kalman filters. Hydrol. Sci. J. 56(7), 1118–1128.     

Flood frequency analysis of southern Africa: II. Identification of regional distributions

Abstract

Regional frequency analysis of annual maximum flood data comprising 407 stations from 11 countries of southern Africa is presented. Forty-one homogeneous regions are identified. The L-moments of the observed data indicate that the possible underlying frequency distributions are Pearson type 3 (P3), lognormal 3-parameter (LN3), General Pareto (GPA) or General Extreme Value (GEV). Simulation experiments for the selection of the most suitable flood frequency procedure indicate that Pearson type 3/Probability Weighted Moments (P3/PWM) and log-Pearson type 3/Method of Moments (LP3/MOM) are suitable procedures for the region.     

多目标区域地球化学编图数据整理方法—以海河流域编图为例

多目标区域地球化学编图是科学表达区域土壤地球化学分布和特征的图示方法,大区域的编图一般可能涉及到对不同的工作区、不同实验室和不同时间的测试数据,以及不同景观条件和网度的表层、深层土壤元素数据或不同分度带的网格数据分别进行拼接合并,因此区域编图对原始数据的整理和网格化处理不可避免.而不同的数据整理方法及其计算参数所形成的结果是非常不同的,数据本身的特点也对编图具有很大的影响.为了真实客观地反映区域内元素的地球化学分布特征,数据整理和处理的方法及技术参数的选择是关键技术问题.作者就化探数据处理中常用的几种插值方法进行了对比评价,并分别从网格间距及搜索半径大小等方面做比较,提出了自己在编图中采用的数据处理方法及选用的技术参数.     

一种界址表和界址点坐标成果表的自动生成方法

界址表和界址点坐标成果表是地籍测绘资料制作过程中经常要绘制的表格,然而很多测绘单位没有专门的软件来绘制,在平时的作图中,都是手工操作,效率低下且容易出错.本文阐述了在AutoCAD平台下,如何应用VBA根据宗地图中界址点、界址线以及宗地的扩展属性自动生成界址表和界址点坐标成果表.程序已在Windows XP和AutoC...     

动态非线性滤波模型非线性强度的曲率度量及其应用

基于微分几何的两种曲率——参数影响曲率和固有曲率,给出了定量描述非线性滤波问题的非线性强度的方法,分别采用扩展Kalman滤波方法和Unscented Kalman滤波方法进行了模拟实验。结果验证了这些曲率确实能够度量非线性滤波问题的非线性强度,且能够评估非线性滤波算法的状态估计性能。     

柴木铁路沼泽化冻土区热管冷却半径的观测研究

柴达尔-木里铁路沿线高温沼泽化多年冻土广泛发育,约20km的冻土路基采用了热管降温措施．借鉴青藏铁路的成功经验,热管的纵向和横向间距均设计为3m,并针对铁路东南-西北的不利走向,在阳坡布设了双排热管．为验证热管措施在多年冻土湿地路段设计参数的合理性,2008年底在柴达尔-木里铁路中段布设了热管冷却半径观测试验场,该观测...