TM影像几何校正算法的精度比较

同大多数的线阵推扫式影像相比,TM影像作为双向扫描型的影像其几何校正方法有其特殊性和复杂性。针对这个问题,本文简要介绍了一般多项式、空间斜墨卡托投影、有理函数模型等几种几何近似校正算法,并利用广州地区的TM影像进行了各种试验分析和精度比较。结果表明:同其他方法相比,空间斜墨卡托投影是一种较好的算法,校正精度最高,能够达到一个像素左右,而且该方法不受地形起伏的影响,无需地面高程信息。     

空间数据重复记录的清理方法研究

在空间数据的更新过程中,需要利用多种数据源对现有数据进行更新,这样可能会导致在获得的空间数据中出现重复记录。利用计算机自动对这些重复记录进行检查处理,将会极大地降低数据生产者的工作量。本文根据在数字制图系统研制过程中所遇到的此类问题,提出了对重复空间数据进行检查与处理的方法,并在所研制的数字制图系统中得到了应用。     

顾及DEM误差自相关的坡度计算模型精度分析

基于DEM的坡度计算,其误差来源于DEM误差、DEM结构和坡度计算模型。在顾及DEM误差自相关的前提下,对四种DEM坡度计算模型进行了分析和评价。研究表明,三阶不带权差分能给出较高的坡度计算精度;在局部窗口中,格网点数量越多,坡度计算越准确;等权比不等权的坡度计算模型更准确;DEM误差自相关结构形式对坡度计算无影响。进一步的理论分析和试验分析还表明：DEM误差自相关性的存在,不仅能够改善地形分析的精度,也能改善DEM自身精度。     

一种基于双重距离的空间聚类方法

传统聚类方法大都是基于空间位置或非空间属性的相似性来进行聚类,分裂了空间要素固有的二重特性,从而导致了许多实际应用中空间聚类结果难以同时满足空间位置毗邻和非空间属性相近。然而,兼顾两者特性的空间聚类方法又存在算法复杂、结果不确定以及不易扩展等问题。为此,本文通过引入直接可达和相连概念,提出了一种基于双重距离的空间聚类方法,并给出了基于双重距离空间聚类的算法,分析了算法的复杂度。通过实验进一步验证了基于双重距离空间聚类算法不仅能发现任意形状的类簇,而且具有很好的抗噪性。     

Interpolation by regularized spline with tension: I. Theory and implementation

Bivariate and trivariate functions for interpolation from scattered data are derived. They are constructed by explicit minimization of a general smoothness functional, and they include a tension parameter that controls the character of the interpolation function (e.g., for bivariate case the surface can be tuned from a membrane to a thin steel plate), Tension can be applied also in a chosen direction, for modeling of phenomena with a simple type of anisotropy. The functions have regular derivatives of all orders everywhere. This makes them suitable for analysis of surface geometry and for direct application in models where derivatives are necessary. For processing of large datasets (thousands of data points), which are now common in geosciences, a segmentation algorithm with a flexible size of overlapping neighborhood is presented. Simple examples demonstrating flexibility and accuracy of the functions are presented.On leave from the Department of Physical Geography and Cartography, Comenius University, Mlynská dolina, Bratislava, Czechoslovakia.On leave from the Institute of Physics, Dúbravská cesta 9, Bratislava, Czechoslovakia.     

The log-normal distribution for hydraulic conductivity of compacted clays: Two or three parameters?

Risk and uncertainty assessments for waste containment systems employing clay barriers often include spatial variability in the hydraulic conductivity as part of the analysis. The two-parameter log-normal distribution is often used to describe the spatial variability, but for compacted clays the three-parameter form can be more appropriate. A statistical hypothesis test was developed that can be used to determine if the two- or three-parameter form of the log-normal distribution is more appropriate. The test is based on a likelihood ratio, comparing likelihood functions for the two- and three-parameter forms at their maximums. Likelihood functions are used assuming that a data set can be segregated into a set of distinct groups of hydraulic conductivities. A step-by-step calculation procedure is described and the test is applied to data collected from 45 sites.     

KIDS AND SPACE IN THE PUERTO RICAN HIGHLANDS

ABSTRACT. The spatial world of the child comprises two great realms, “in’ and “out,’ more or less corresponding to the great behavioral domains of “got to’ and “doing nothing.’ Within the “got‐to’ domain–and thus “in’–are home, school, and other loci of secure, stable authority. Included in “doing nothing’–and so “out’–are street and yard, field and stream, pool hall and movie theater, the spaces of games, things to do, and really doing nothing. This study looks at the shifting relationships of these realms across the life cycle of kids in the highlands of Puerto Rico in 1969–1970.     

Spatial practices and imaginaries: Experiences of colonial officers and development professionals

This paper explores the spatiality of colonial and postcolonial power and discourse as produced, performed and imagined by former British colonial service officers and contemporary UK international development professionals. It focuses on two key aspects of spatial practices. The first addresses the spaces inhabited by these colonial officers and development professionals overseas and how their locatedness, embedded or enclavic, shapes relationships to others. The second explores this distinctive social and spatial distancing through their relationship to, and imagined geographies of, home and away and how these are embodied in their institutional and cultural capital. The paper examines the regularities and consistencies that stand out from numerous individual practices through which both former colonial officers and development professionals negotiate the situations in which they live and work. It also specifies how authoritative management, privilege and distance informs their spatial practices despite changing global contexts and a more diverse composition of those who articulate contemporary relationships between 'first' and 'third' worlds. Finally, the paper suggests that the cultures which travelled over colonial space through being performed by colonial officers have been reworked throughout the postcolonial period, belying epochal historical periodizations that conjure up a clear disjuncture between colonial and development eras.     

基于Intergraph GIS的基础空间数据库一体化建设研究

阐述了基于Intergraph GIS的城市基础空间数据的结构和建库的内容,提出了一体化的建库、质量控制、空间数据动态更新以及基于版本信息的历史数据存储与恢复的方法,介绍了一体化建库实例。     

Practical Research of IKONOS-2 Geopositioning and Its Accuracy in Tibet of China

This paper presents the studies of the refining of IKONOS-2 RPC, the transform of the datum, the mode of the control point distribution and the method of IKONOS stereo triangulation, so that IKONOS imagery can be used to collect the precise geospatial data and produce the large scale map. The transform between the IKONOS-2 image space and the national coordinate system based on the RPC have been developed, and the results of block adjustment with various control schemes in a practical project near Himalayas have been examined and analysed. The encouraging results of high positioning accuracy have been obtained.