New method for positional quality control in cartography based on lines. A comparative study of methodologies

This article describes a set of new metrics for evaluating the positional accuracy of lines to apply a positional control to cartographic databases. In the same way as traditional points-based studies, control based on lines compares the positions between the lines (one from a given database to be controlled and the other from a more accurate independent control database). The proposed method is based on vertex displacements and their influence on adjacent segments. The new methodology which applies these metrics is called ‘vertex influence method’. It also includes an analysis for detection of systematic displacements and a variability value of displacements based on the accuracy of the lines. All the proposed metrics are applied to a real case made up of more than 180 km of roads from the two databases. By means of this study we also compare the results obtained from the main traditional methodologies. This study has revealed the viability of the use of this method to obtain an accuracy value of positional cartographic products.     

德国铁路的建设经验和启示

德国是世界主要发达国家，重视铁路建设並作为经济推动力之一，在德国铁路建设１６０年历史中，致力于铁路网加长加密和均衡布局，旧线改造与新线建设并举，重视复线及铁路轮渡建设，及早开发高速铁路。保证客运安全便捷舒适廉价和货运重载快速，这些经验值得借鉴。     

Accuracy of contour lines using 3D bands

This article describes a new methodology for the planimetric control of contour lines. The method is based on the generation of buffers around the contour lines which define a 3D buffer around the maximum slope line. After that we analyze the quantity of points from a more accurate source which is inside this buffer. As a result, we obtain a distribution function of the control points included when we apply several widths to the buffers. We have also determined the angularity and height differences of these points. The method has been applied to several sets of contour line intervals derived from a digital elevation model (DEM) and to the contour lines of one published topographic map using the DEM as the control source. We have also analyzed the representative behaviour of the contour lines, taking into account the contour line interval and the detection of an uncertainty model based on the slope variation. This study demonstrates the viability of the proposed method for obtaining the uncertainty of the contour lines depending on a given level of confidence and the variability of this uncertainty in the map. Finally, we propose a range of contour line intervals based on the scale and slopes.     

黄土丘陵地形谷脊线展布特征

地理对象的空间展布格局特征是区域地貌研究的核心问题.其中,把握地物的组织结构及尺度范围特征是认识其空间展布格局的根本.选取黄土丘陵沟壑区韭园沟流域为实验样区,以流域地形特征线为切入点,采用空隙度系列分析方法,在5 m分辨率DEM上研究黄土地貌发育中期小流域内,地形谷脊线的空间展布格局特征.在东-西、南-北两个方向的探测结果表明:韭园沟流域谷、脊线均具有自组织、多尺度、自相似的格局特点,但各向异性特征不明显.在两个方向上均具有三个特征尺度范围:在东西方向上尺度范围分别为540 m、2 100 m、4 845 m;南北方向上尺度范围分别为1 215 m、2 810 m、5 700 m.该研究结果初步揭示了黄土地貌流域系统骨架线的空间展布格局特征,为区域地貌研究时分析尺度的选取,提供了可借鉴的思路与方法.     

A Solution of some Problems in Potential Theory

Summary. In the present paper, we give an approximate analytic solution of the Dirichlet and Neumann problems in the two-dimensional case for a contour of any shape. The formalism is based on a representation of potential functions as a sum of elementary interpolating functions and uses the theory of generalized inverse matrices. Formulae are given in the cases of Cartesian, polar and elliptic co-ordinates. The fact that an analytic expression for continuation is obtained enables one to compute and draw equipotential lines as well as field lines; besides, any further computations that one might want to perform on either the field or the potential can be handled in an analytic way. The formalism can be extended from the Laplace to the Helmholtz equation.
We give examples in the case of magnetostatics, treating in more detail the problem of the distortion of magnetic field lines by an inclusion. We also show how the method allows the computation of conformal mappings in otherwise intricate situations.     

中国陆路交通干线自然灾害风险刍议

中国经济的快速发展,使陆路交通的密度、长度和搭乘陆路交通工具的物资和人口流动规模日益增加,交通客流和物流的增多也使遭遇自然灾害的风险进一步加大。通过数据统计、GIS方法,对我国陆路交通干线(公路、铁路)的密度和过去死亡人口和自然灾害损失的模数进行叠合分析,认为在自然灾害频次和灾种呈上升趋势的背景下,陆路交通干线的极端灾害事件日益增多,中国自然灾害的风险因子在地域分布上中、东部高,西北部低。我国目前众多的极端灾害事件对交通干线的影响,是因为对交通干线的风险因子识别研究不足,应该从节点城市、干线路段和区域交通网络三个方面对陆路交通干线自然灾害的风险展开研究。     

泽错公路夏果沟泥石流成因及防治

泽错公路是西藏自治区主骨架公路网络“六大通道”之一，由于该区域独特而又脆弱的自然环境因素，泥石流灾害分布广泛，暴发频繁，活动强烈，类型众多，严重地影响公路的畅通。泽错公路全长217km，有泥石流沟71条，平均密度为3．27条／10km，其中，夏果沟泥石流危害比较严重，其发育特征及其危害方式在公路沿线非常典型。夏果沟是一条高频率亚粘性泥石流沟，每年平均暴发泥石流10次左右，泥石流体含有大量石块，比较粘稠，汇集到公路后发生强烈堆积成灾，形成路堑阻断交通。每次泥石流暴发其堆积厚度可达2m以上，长度65m左右，一般要2—3d或更长时间才能清除，严重地影响到公路畅通。根据夏果沟泥石流对该段公路及灌渠和农田的危害特点，防治工程的重点是将泥石流固体物质拦蓄在沟内，采取拦挡停淤的工程整治措施。工程实施后，该公路段泥石流灾害消除，保证公路畅通和灌渠及农田的安全，取得良好的效益。     

Maximum entropy regularization of the geomagnetic core field inverse problem

The maximum entropy technique is an accepted method of image reconstruction when the image is made up of pixels of unknown positive intensity (e.g. a grey-scale image). The problem of reconstructing the magnetic field at the core–mantle boundary from surface data is a problem where the target image, the value of the radial field B_r , can be of either sign. We adopt a known extension of the usual maximum entropy method that can be applied to images consisting of pixels of unconstrained sign. We find that we are able to construct images which have high dynamic ranges, but which still have very simple structure. In the spherical harmonic domain they have smoothly decreasing power spectra. It is also noteworthy that these models have far less complex null flux curve topology (lines on which the radial field vanishes) than do models which are quadratically regularized. Problems such as the one addressed are ubiquitous in geophysics, and it is suggested that the applications of the method could be much more widespread than is currently the case.     

Illuminated and shadowed contour lines: improving algorithms and evaluating effectiveness

Shadowed contour lines vary line width. Illuminated contour lines additionally vary color based on an angle of illumination. Illuminated and shadowed contour lines date back to the mid-nineteenth century, but their effectiveness compared to conventional contour lines has not been fully examined. Currently, illuminated and shadowed contour lines are not widely used in computer-based cartography because they are not included in most GIS apmaking software. This article introduces improvements to existing algorithms for creating illuminated and shadowed contour lines from digital elevation data. A software package is made available to allow mapmakers to more easily make customized illuminated and shadowed contour maps. A user study comparing illuminated and shadowed contour lines to conventional contour lines and shaded relief with approximately 400 participants was conducted. Results indicate that map-readers can interpret relative height differences between points better and quicker with illuminated contour lines than regular contour lines or shaded relief. Study participants were able to select absolute maxima on an unlabeled illuminated contour map and a labeled regular contour map with equal accuracy and speed. These findings suggest that illuminated contour lines could be used more frequently for improved visualization of terrain and other surface data on maps.     

基于GIS的采煤塌陷区土地复垦项目规划设计研究

土地开发整理是现阶段中国实现耕地总量动态平衡的重要途径,采煤塌陷区土地复垦是其中重要的组成部分。受塌陷沉降的影响,采煤塌陷区具有地形破碎、微地貌起伏交错和土壤养分流失严重等特点,其在土地复垦项目的规划设计中面临的问题较一般区域复杂。在分析采煤塌陷区土地复垦规划设计流程与方法的基础上,借助GIS技术,将地形图中等高线进行栅格化处理,并根据得到的数据生成三维地形模型,对项目区地形进行模拟,并分别从复垦适宜性评价、项目规划择优以及项目工程设计三方面进行了实证研究。     

川滇黔接壤地区自然灾害危险度评价

川滇黔接壤地区是中国自然灾害极易发区,高频度、高强度的自然灾害已经给该区域社会经济发展造成严重威胁。通过对川滇黔接壤地区主要自然灾害的实地调查和数据分析,构建地震、泥石流、崩塌滑坡、洪涝、干旱、冰雹和低温冷害等7个主要灾种的危险度评价指标体系和评价指标数据库,利用GIS空间分析功能获取研究区自然灾害危险度综合评价图。结果表明：川滇黔接壤地区自然灾害表现出“两线一区”的基本格局,即小江-安宁河深大断裂、金沙江沿线和乌蒙山区3个自然灾害高危险区。宏观地质构造和地貌形态是控制川滇黔接壤地区自然灾害分布格局的主要因素。高度危险和极度危险区威胁的国土总面积、总人口、GDP总量都占到研究区的一半以上,防灾减灾成为该地区发展中不可忽视的关键问题。研究也发现自然灾害对农村区域影响更加显著,因此在该地区社会经济发展和扶贫开发中,特别是乌蒙山区集中连片特困地区开发中要高度重视自然灾害的影响。     

基于GIS的斜坡单元划分方法改进与实现

斜坡单元已广泛应用于滑坡易发性制图和地质灾害评价。然而在山间盆地或大型宽谷处,常规方法划分出的斜坡单元与地貌背景难以匹配。依据高程及其衍生变量的基本形态系统和曲率的流域分割原理,基于ArcGIS技术,通过叠加曲率和反转曲率的流域边界,改进了斜坡单元划分方法。结果表明：与常规方法相比,改进方法不仅能够使用山脊线和山谷线以划分斜坡单元,还能利用台地边界和宽谷边界以分割水平地表与倾斜地表;划分出的单元大小相对均匀,单元形状总体介于圆形和正三角形之间。对于水平成分较多的地区,如黄土塬区和水库库区,该方法与传统方法相比,具有较好的应用前景。     

川滇黔接壤地区自然灾害危险度评价简

川滇黔接壤地区是中国自然灾害极易发区,高频度、高强度的自然灾害已经给该区域社会经济发展造成严重威胁。通过对川滇黔接壤地区主要自然灾害的实地调查和数据分析,构建地震、泥石流、崩塌滑坡、洪涝、干旱、冰雹和低温冷害等7个主要灾种的危险度评价指标体系和评价指标数据库,利用GIS空间分析功能获取研究区自然灾害危险度综合评价图。结果表明：川滇黔接壤地区自然灾害表现出“两线一区”的基本格局,即小江—安宁河深大断裂、金沙江沿线和乌蒙山区3个自然灾害高危险区。宏观地质构造和地貌形态是控制川滇黔接壤地区自然灾害分布格局的主要因素。高度危险和极度危险区威胁的国土总面积、总人口、GDP总量都占到研究区的一半以上,防灾减灾成为该地区发展中不可忽视的关键问题。研究也发现自然灾害对农村区域影响更加显著,因此在该地区社会经济发展和扶贫开发中,特别是乌蒙山区集中连片特困地区开发中要高度重视自然灾害的影响。     

一种高准确度的约束Delaunay三角网生成算法研究

约束线段的嵌入是CDT两步法的关键步骤之一,目前该方面的研究还不够完善,主要忽视了影响区域是凹多边形和影响区域内包含悬挂点的情况.该文研究带有约束条件的Delaunay三角网的生成问题,考虑了约束线段影响区域的特殊情况,采用递归割耳法嵌入约束线段,先将影响区域调整为简单多边形,再递归寻找并割去多边形的耳,最终将影响区域重新三角剖分.该方法可有效提高约束DIelaunay三角网的质量.     

基于数位的相机径向畸变参数计算

相机畸变是影响基于图像的几何量测、三维重建精度的重要因素之一。空间中一条直线在透视投影作用下理应成为一条直线,但因畸变其构象发生弯曲,通过场景信息中共线点的透视投影不变性可以求解出相机径向畸变系数。考虑畸变的渐变特性,该文设计了基于数位的相机径向畸变参数解算方法:将相机一阶径向畸变系数k1用科学计数法X×10-m表示,依次确定其指数m及尾数X,直至满足精度的设定,最终求解出k1的值。最后通过模拟和实例数据对该方法进行了分析验证。     

新世纪湖北省城镇空间发展战略及对策

21世纪湖北省城镇空间发展研究是以空间相互作用理论为基础,提出了湖北省城镇空间发展的“一点二线,占轴开发;实内拓外,圈层扩展;多重循环,交叉推进”的模式,其依据主要是：①从区位理论看,湖北省武汉市地处中国中部,理所当然地承担着承东启西、南北交流的枢纽作用,武汉就是湖北省乃至长江中游的极核城市;②从经济区位来看,“两线”交汇于湖北省的经济增长极核－武汉,“两线”地带集中湖北省的大部分工业、农业、人口和城市;③湖北省盆状地形,向心状的水系,向心状的土地利用以及向心交汇的综合运轴网络,构成了以武汉为中心的集聚与扩散的层状网络结构;在此基础上构想今后一段时间内湖北省城镇空间组织的格局及建设层次,即武汉（一级）－襄樊、荆州、宜昌、黄石（二级）－十堰、荆门、鄂州、随州、恩施、仙桃、枝城等（三级）。     

A study of diurnal variation of the electromagnetic field in northern France using ancient recordings

Summary. From 1883 to 1901 magnetic elements were continuously recorded at the French Saint-Maur observatory. From 1893 to 1895, Earth potentials along two 15 km long orthogonal lines were also recorded. Moreover, from 1884 to 1885, Blavier,'Ingénieur des Télégraphes', used several some hundred kilométre long telegraphic lines to measure and record Earth potentials. Using this set of data we will study the daily variations of the telluric and magnetic fields and the way according to which these two fields are correlated.
The observed magnetotelluric tensor is antisymmétric when the long telluric lines are considered. It is not the case for the short lines. But, making use of a correction derived from the formalism developed by Le Mouel & Menvielle in the static distortion approximation, one can derive an impedance whose phase is equal to the phase of the impedance derived from the long line data.     

基于遥感的黑龙江省西部水稻、玉米种植范围对温度变化的响应

利用多时相遥感数据,生成黑龙江西部地区1988年和1998年两个序列的农作物种植范围图,结合相应时段的该地区≥10℃积温数据进行分析。研究表明,黑龙江省西部地区农作物种植结构对气候变暖有明显的响应变化:随着等温线的大幅度整体北移,水稻的种植北界随着≥10℃积温的2200℃等温线向北移动约1.5个纬度,水稻集中种植区随≥10℃积温的2300~2400℃等温线北移约1个纬度;分布在≥10℃积温2800℃等温线和2400℃等温线附近的两个玉米密集种植区随着上述两条等温线北移1个纬度左右。在上述玉米、水稻种植范围北移过程中,同时出现玉米的种植区被新增的水稻种植区大范围替代的现象。     

区域交通网络分形的DBM特征--交通网络Laplacian分形性质的实证研究

城镇体系在理论状态下的三角点阵格局暗示着现实中的交通网络在一定时空条件下具有ＤＢＭ模型的某些特征。从形态分析和维数对比两个方面论证了区域交通网络扔Ｌａｐｌａｃｉａｎ分形性质,认为可用ＤＢＭ模型模拟城镇体系－交通网络的形成和演化过程,从而揭示其动力学机制。     

Fuzzy representation of geographical boundaries in GIS

Abstract

Polygon boundaries on thematic maps are conventionally considered to be sharp lines representing abrupt changes of phenomena. However, in reality changes of environmental phenomena may also be partial or gradual. Indiscriminate use of sharp lines to represent different types of change creates a problem of boundary inaccuracy. Specifically, in the context of vector-based GIS, use of sharp lines to represent gradual or partial changes may cause misunderstanding of geographical information and reduce analysis accuracy.

In this paper, the expressive inadequacy of the conventional vector boundary representation is examined. A more informative technique—the fuzzy representation of geographical boundaries—is proposed, in which boundaries describe not only the location but also the rate of change of environmental phenomena. Four methods of determining fuzzy boundary membership grades from different kinds of geographical data are described. An example of applying the fuzzy boundary technique to data analysis is presented and the advantages of the technique are discussed.