月球地形测绘和月球大地测量(4)

主要介绍了美国在20世纪70年代著名的"阿波罗(Apollo)"登月项目,和90年代的"克莱门汀号(Clementine)"、"月球探测(LunarProspector)",以及欧共体的"SMART-1"探月航天器。1969年至1972年间阿波罗项目前后进行了17次环绕登月的各种试验,其中有6次成功登月。它们分别是"阿波罗"11,12,14,15,16,17号。"阿波罗"和以后的探月项目向科学家提供了大量的月球数据,其中有影像资料,月面和环月试验的成果,同时还进行了样本收集、月面及其周围环境的地学勘测和月球大地测量等各项工作。     

Three-dimensional Reconstruction of the Yaolin Cave

This paper reports on three-dimensional reconstruction of the Yaolin Cave in the Karst Region of Zhejiang, China. An object-oriented method was used to represent two cave classes—the class Boundary and the class Inside. The class Boundary included objects of the cave ceiling and the cave floor which are part of the topographical trend of the cave. This trend was determined by integrating topography with landform using TIN modeling. The inside of the cave with stalagmites, stalactites, dripstone-columns, and other objects was built using surveying data, photographs, and such computer graphics techniques as texture mapping and transparency. A stand-alone, 3-D visualization system—Cave3D—was developed on the Windows 98/NT platform to produce 3-D graphics and implement graphics-based computation, spatial query, and analyses. A virtual Yaolin cave was created using VRML97 and Java and posted on the Web.     

Constrained variants of the gravity model and spatial dependence: model specification and estimation issues

In this paper, we distinguish three constrained variants of the gravity model of spatial interaction: doubly constrained, production constrained and attraction constrained exponential gravity models. These model variants include origin- and/or destination-specific balancing factors that act as constraints to ensure that the estimated rows and columns of the flow data matrix sum to the observed row and column totals. Because flows are typically counts, the Poisson rather than the normal probability model specification furnishes the appropriate statistical distribution, and parameter estimation can be achieved via Poisson regression. This probability model specification motivates the use of origin and/or destination fixed effects or—under certain conditions—the use of origin- and/or destination-specific random effects for model estimation. The paper establishes theoretical connections between balancing factors, fixed effects represented by binary indicator variables and random effects. The results pertaining to both the doubly and singly constrained cases of spatial interaction are illustrated with an empirical example while accounting for spatial dependence between flows from locations neighbouring both the origins and destinations during estimation.     

Atlas Mapping in the 21st Century

Atlases are changing. The paper paradigm of maps and atlases has pervaded recent cartographic history. By nature that paradigm serves, as well as defines, a specific audience in terms of use and presentation. In the lab and at the printing press, the paper paradigm demands certain design and production flows that will drastically change through evolutions in data structures, mapmaking techniques, and presentation methods. Technological transformations in mapping influence much of this change. The implications for the creation and distribution of atlases are significant. With that in mind, this paper addresses a number of issues that relate to the technological evolution of atlases from paper to digital products: the distinction between paper and digital products and services and the implications of that distinction for atlas design—particularly for web-based services; facilitating data and its application to the evolution of map/atlas products; and a redefinition of "atlas" and the "audience" for an atlas.     

Formulas for precisely and efficiently estimating the bias and variance of the length measurements

Error analysis in length measurements is an important problem in geographic information system and cartographic operations. The distance between two random points—i.e., the length of a random line segment—may be viewed as a nonlinear mapping of the coordinates of the two points. In real-world applications, an unbiased length statistic may be expected in high-precision contexts, but the variance of the unbiased statistic is of concern in assessing the quality. This paper suggesting the use of a k-order bias correction formula and a nonlinear error propagation approach to the distance equation provides a useful way to describe the length of a line. The study shows that the bias is determined by the relative precision of the random line segment, and that the use of the higher-order bias correction is only needed for short-distance applications.     

基于点云数据的不规则文物三维重建——以经幢为例

海量点云数据可以较好地构建文物的三维建模,针对文物复杂的表面结构,传统的算法很难达到精细建模,为了解决复杂模型表面的空间三角网构网问题,本文结合空间三角形的法向量构建三角网,以空间三角网表面的曲率为约束条件,构建物体表面的空间三角网,然后对构建的空间三角网进行精细建模。以昆明市文物——经幢为例进行三维重建试验,结果表明,新方法适合室内文物的三维建模,可以达到较好的效果。     

可视化交互空间数据挖掘技术的探讨

随着地理信息获取技术飞速发展,使得当前存储在空间数据库中的空间数据的深度和广度得到了前所未有的发展,传统的空间统计方法和空间分析方法已经难以有效而迅速地处理和分析它们,如何有效而及时地分析和处理空间数据变得越来越迫切。空间数据挖掘作为上个世纪90年代逐步发展起来的新兴技术,逐渐在研究和实践中显示出它的优势。与此同时,地理可视化技术也逐步走向成熟,二者的结合催生出新型空间数据分析技术———可视化交互空间数据挖掘。本文就该技术的相关问题进行了一些研究探讨。     

Places of the Holocaust: Towards a model of GIS of place

Progress toward developing a GIS of place can only follow from an understanding of what place is, and this understanding draws on geographical theory. Here—following Agnew, Tuan, and others—we consider place as being made up of three components—location, locale, and sense of place—which are recognizable at multiple scales and vary historically as a product of social and political processes. Using the testimonies of two survivors of the Holocaust, we sketch the components of a model for a GIS of place that allows for this theory of place to be visualized and analyzed. The model is, crucially, both multi‐scalar and sensitive to uncertainty, as a GIS of place needs to be able to zoom in and out of the different scales at which place is experienced, as well as capture both uncertain data and uncertainty as data. We see potential in the representations proposed for scaling up from the anecdotal to the general in the sense that any narrative can be grouped and classified according to places and scales as shown here. The challenge in developing a GIS of place along the lines we propose here is to design a new set of functionalities that can do so.     

20世纪末华北地区冬小麦物候期监测及时空格局分析

基于1983—1999年7 d时间分辨率5 km空间分辨率的AVHRR传感器数据,利用曲线特征点的物候监测方法,反演获得华北地区冬小麦关键物候期并分析其时空演变规律。结果表明:1)冬小麦的拔节期、抽穗期和成熟期主要集中在60—100、105—125和120—155 d。冬小麦物候期空间格局特征和纬度相关,纬度每升高一度冬小麦的拔节期、抽穗期和成熟期分别推迟了5.2、3.5和3.1 d。2)1983年以来,整个研究区的冬小麦物候期呈现提前趋势,每十年冬小麦的拔节期、抽穗期和成熟期分别提前了0.7、3.1、1.9 d。     

一种基于机器学习的城市发展模拟元胞模型

利用元胞自动机(Cellular Automata,CA)模拟土地利用变化,已经成为认识和理解其复杂动态演化过程的有效手段.传统的元胞自动机基于线性转换规则,较难表达土地利用变化的非线性边界问题.本文研究利用最小二乘支持向量机方法(LS-SVM),将原空间下的非线性可分问题,通过高斯径向基核函数映射到高维特征空间,简化...     

发射信号不完善性对卫星导航系统内及系统间干扰的影响分析

研究了3种典型的卫星发射信号不完善性——载波泄漏、互调失真和杂散辐射对于卫星导航信号的接收所带来的干扰,通过信号建模以及谱分离系数、码跟踪谱灵敏度系数和等效载噪比的解析计算对干扰效果进行量化分析;针对GPS和Galileo系统L1/E1频段的信号进行了多层次的仿真计算,给出了综合考虑噪声、信号损耗、外源干扰、GNSS系统内和系统间干扰,以及3种信号不完善性单独作用、两两组合和综合作用下的结果,其中对于GPS L1C/A短码考虑了电文调制对线谱的影响。结果表明,当总的不完善干扰功率水平达到一定程度后,其对接收机信号捕获跟踪和解调的影响大于系统间干扰,不能忽略。     

不同趋势法的宁夏长时序植被变化分析

宁夏地处黄土高原,植被变化趋势直接影响其生态保护。本文应用2005—2015年的MODIS NDVI月合成产品,并采用最大合成法得到年NDVI数据,分别利用一元线性回归法和Sen+Mann-Kendall法对宁夏11年间植被变化趋势和空间差异进行研究分析。结果表明,在月际变化上,月NDVI均值呈高斯分布,7—9月是植被长势最好的阶段;在年际变化上,2005—2007年NDVI值明显增长,2008—2012年NDVI值呈稳定性增长,2013—2015年NDVI值有下降趋势;在变化趋势上,一元线性回归法与Sen+Mann-Kendall法得到的植被变化趋势基本一致,均表现为北部植被整体改善,但局部城区植被退化较为严重;中部地区轻微改善,局部存在明显改善;南部植被有明显改善且植被改善面积较大;通过差异性分析二者差异性仅为22.95%,且Sen+Mann-Kendall法能更好地监测轻微变化区域,变化趋势更加准确。     

基于模糊模式识别的土壤含铁量高光谱估测

对横山县采集的84个土样350—2500 nm波段的光谱曲线进行了土壤含铁量光谱反演分析,证明了以包络去除法处理光谱数据为基础所建立的模糊贴近度反演模型为最佳,利用模糊贴近度识别进行土壤含铁量反演是可行的。     

机场净空限制面数学模型构建及三维可视化实现

机场净空管理是机场运行指标的重要组成部分.本文通过对机场净空规格进行分析,建立了机场净空区障碍物限制面的数学模型.在此数学模型的基础上使用ArcGIS系列软件建立净空限制面三角网高程模型,并进行三维显示,为使用地理信息系统进行净空管理莫定了基础.     

面向地理信息共享的AM/FM/GIS核心语义模型

提出了一种适用于管线行业的AM/FM/GIS数据模型——核心语义模型,对核心语义模型的概念框架,包括定义、编码、空间关系和规则组件环境进行了详细的剖析,得出该数据模型有利于实现管线行业的信息共享、提高数据录入精度、完善地理要素的表达,知识的可扩展性和规则组件的可重用性保证了核心语义模型具有更开放灵活的用户参与机制,最后提出了下一步研究的方向。     

A resampling strategy based on bootstrap to reduce the effect of large blunders in GPS absolute positioning

In the absence of obstacles, a GPS device is generally able to provide continuous and accurate estimates of position, while in urban scenarios buildings can generate multipath and echo-only phenomena that severely affect the continuity and the accuracy of the provided estimates. Receiver autonomous integrity monitoring (RAIM) techniques are able to reduce the negative consequences of large blunders in urban scenarios, but require both a good redundancy and a low contamination to be effective. In this paper a resampling strategy based on bootstrap is proposed as an alternative to RAIM, in order to estimate accurately position in case of low redundancy and multiple blunders: starting with the pseudorange measurement model, at each epoch the available measurements are bootstrapped—that is random sampled with replacement—and the generated a posteriori empirical distribution is exploited to derive the final position. Compared to standard bootstrap, in this paper the sampling probabilities are not uniform, but vary according to an indicator of the measurement quality. The proposed method has been compared with two different RAIM techniques on a data set collected in critical conditions, resulting in a clear improvement on all considered figures of merit.     

电离层二阶项模型的构建及其变化规律分析研究

在高精度大地测量GPS数据处理研究和应用领域,电离层二阶项延迟影响不容忽视。采用带有三角级数的曲面拟合模型构建电离层延迟二阶项模型,并结合西安市高精度GPS地面沉降监测数据,分析近五年来该区域电离层总电子含量、一阶项、二阶项延迟的半年与年变化规律及其对定位结果的影响,在电离层二阶项的研究方面获得了一些有意义的结论。     

PHOTOMAPS FROM SPACE: THEIR PRODUCTION AND POSSIBLE USES

This paper outlines, from the Soviet perspective, technical principles for the use of remote sensing imagery in mapping, with special emphasis on the compilation of small-scale space photomaps—composite map-space images in which the thematic detail of a photographic image is enhanced and/or supplemented by cartographic techniques. Two systems for producing such images, one Soviet and the other East German, are compared and a series of basic procedures identified—production of orthographic images, compilation of a terrain model and original image of relief, stereoplotting of contours on an orthophotographic base, and overall map design. A concluding section explores potential applications of space photomaps in geographic research. Translated from: Vestnik Moskovskogo Universiteta, geografiya, 1986, No. 1, pp. 49-56.     

Evaluating the Performance of Multi-Class and Single-Class Classification Approaches for Mountain Agriculture Extraction Using Time-Series NDVI

Supervised multi-class classification (MCC) approach is widely being used for regional-level land use–land cover (LULC) mapping and monitoring. However, it becomes inefficient if the end user wants to map only one particular class. Therefore, an improved single-class classification (SCC) approach is required for quick and reliable map production purpose. In this regard, the current study attempts to evaluate the performance of MCC and SCC approaches for extracting mountain agriculture area using time-series normalized differential vegetation index (NDVI). At first, samples of eight LULC classes were acquired using Google Earth image, and corresponding temporal signatures (TS) were extracted from time-series NDVI to perform classification using minimum distance to mean (MDM) and spectral angle mapper (i.e., multi-class SAM—MCSAM) under MCC approach. Secondly, under SCC approach, the TS of three agriculture classes (i.e., agriculture, mixed agriculture and plantation) were utilized as a reference to extract agriculture extent using Euclidean distance (ED) and SAM (i.e., single-class SAM—SCSAM) algorithms. The area of all four maps (i.e., MDM—19.77% of total geographical area (TGA), MCSAM—21.07% of TGA, ED—15.23% of TGA, SCSAM—13.85% of TGA) was compared with reference agriculture area (14.54% of TGA) of global land cover product, and SCC-based maps were found to have close agreement. Also, the class-wise detection accuracy was evaluated using random sample point-based error matrix which reveals the better performance of ED-based map than rest three maps in terms of overall accuracy and kappa coefficient.     

地图机助制图系统的设计与发展模式

本文从地图机助制图系统的实用与发展的特性出发,阐述了自行设计的微机大比例尺地图机助制图系统Auto G&M System的设计思想,并对其中的关键部分作了较详细的描述。最后根据当前地理信息系统(GIS)的发展情况,提出了地图机助制图系统的发展模式,促进该系统向标准化及地理信息系统发展。