面向虚拟地球的矢量金字塔分布式存储研究

针对矢量数据在虚拟地球中的高效传输及实时可视化的需求,分析了矢量数据在虚拟地球中的组织方式及特点,设计了基于HBase的矢量金字塔分布式存储模型和一种基于MapReduce的矢量金字塔并行入库方法,使得海量矢量数据的入库可分配到各个子节点进行,大大缩短了入库时间.最后以GeoGlobe虚拟地球为基础平台,分别在单机和集群环境下对矢量金字塔的调度时间进行了实验.实验结果表明,该方法具有较好的可行性,有效提高了虚拟地球并发调度的效率.     

Tight integration of GPS observations and persistent scatterer InSAR for detecting vertical ground motion in Hong Kong

A method for tightly integrating GPS observations and the persistent scatterer (PS) interferometric synthetic aperture radar (InSAR) is proposed to detect vertical ground motion in Hong Kong, China. The tropospheric zenith wet delays (ZWD) derived from GPS observations at sites in the SAR scenes are used first to model and correct for the tropospheric effects in the interferograms generated from the SAR images. The vertical motion rates (VMR) of the GPS sites determined based on the continuous GPS observations obtained at the sites are then used as constraints in the PS InSAR solutions to further enhance the quality of the solutions. Data from 12 continuous tracking GPS sites in Hong Kong and 8 ENVISAT ASAR images acquired during 2006–2007 are used to demonstrate the application of the proposed method. The results from the example show that the method is capable of detecting accurately the vertical ground motion.     

兴安盟气象局虚拟局域网应用与实现

VLAN现已成为当前应用很广泛也很成熟的一种以太局域网技术,其技术的灵活性、网络安全性及便于实现的特性正符合实际工作的需要,文章就虚拟局域网在兴安盟气象局局域网的具体实现与应用作一具体描述。     

Time Evolution of Deformation Using Time Series of Differential Interferograms: Application to La Palma Island (Canary Islands)

Differential interferometry is a very powerful tool for detecting changes in the Earth’s crust where coherence conditions are good, but is difficult to employ in some volcanic areas due to dense vegetation. We apply two differential InSAR methods using the time series associated with the interferograms to perform a phase analysis on a data set for La Palma island (Canary Islands) from the ERS-1 and ERS-2 European Space Agency (ESA) satellites for the time period 1992 to 2000. Both methods involve choosing a master image from the database and creating a series of interferograms with respect to this image. The “Coherent Pixel Time Series” (CPTS) technique chooses pixels with good average coherence, aligns the unwrapped interferograms with a stable area and then performs an inversion to calculate the linear velocity to quantify the deformation. The Coherent Target Modeling (CTM) method calculates the temporal coherence of each pixel to identify stable targets and then determines the best velocity for each pixel by using a linear fit that maximizes the temporal coherence. Using these two methods we have been able to detect deformation on La Palma Island that has been previously undetectable by conventional InSAR methods. There is a roughly circular region on the Southern part of the island that is actively deforming at ~ −4 to −8 mm/yr. This region is located near the Teneguia valcano, the host of the last known eruption on La Palma in 1971. A thorough investigation of the possible sources for this deformation revealed that it was most likely created by a subsurface thermal source.     

虚拟地理信息技术的地下水动态模拟分析应用

针对现有地下水流模拟软件在数据预处理、三维可视化效果等方面的不足,以Visual C⁺⁺ 6.0为主要开发环境、OpenGL为三维图形显示与渲染工具,以地下水及其赋存地质体观测记录为主要数据源,实现了数据处理、建模、存储、调度、查询以及真三维可视化,在此基础上完成了地下水动态模拟分析功能,实现了虚拟地理信息技术在地下水工作中的系统应用,具有功能开放、丰富、灵活的特点。     

Review paper: Virtual sources and their responses,Part II: data‐driven single‐sided focusing

In Part I of this paper, we defined a focusing wave field as the time reversal of an observed point‐source response. We showed that emitting a time‐reversed field from a closed boundary yields a focal spot that acts as an isotropic virtual source. However, when emitting the field from an open boundary, the virtual source is highly directional and significant artefacts occur related to multiple scattering. The aim of this paper is to discuss a focusing wave field, which, when emitted into the medium from an open boundary, yields an isotropic virtual source and does not give rise to artefacts. We start the discussion from a horizontally layered medium and introduce the single‐sided focusing wave field in an intuitive way as an inverse filter. Next, we discuss single‐sided focusing in two‐dimensional and three‐dimensional inhomogeneous media and support the discussion with mathematical derivations. The focusing functions needed for single‐sided focusing can be retrieved from the single‐sided reflection response and an estimate of the direct arrivals between the focal point and the accessible boundary. The focal spot, obtained with this single‐sided data‐driven focusing method, acts as an isotropic virtual source, similar to that obtained by emitting a time‐reversed point‐source response from a closed boundary.     

Review paper: Virtual sources and their responses,Part I: time‐reversal acoustics and seismic interferometry

A focusing acoustic wave field, emitted into a medium from its boundary, converges to a focal spot around the designated focal point. Subsequently, the focused field acts as a virtual source that emits a field propagating away from the focal point, mimicking the response to a real source at the position of the focal point. In this first part of a two‐part review paper on virtual sources and their responses, we define the focusing wave field as the time reversal of an observed point‐source response. This approach underlies time‐reversal acoustics and seismic interferometry. We analyse the propagation of a time‐reversed point‐source response through an inhomogeneous medium, paying particular attention to the effect of internal multiples. We investigate the differences between emitting the focusing field from a closed boundary and from an open boundary, and we analyse in detail the properties of the virtual source. Whereas emitting the time‐reversed field from a closed boundary yields an accurate isotropic virtual source, emitting the field from an open boundary leads to a highly directional virtual source and significant artefacts related to multiple scattering. The latter problems are addressed in Part II, where we define the focusing wave field as an inverse filter that accounts for primaries and multiples.     

VSP地震干涉成像及应用研究

受井中检波器串级数局限,垂直地震剖面(VSP)反射波成像范围窄,且不能对井中最浅接收点上方区域有效成像.虽然多次波成像能扩大成像范围,但在实际应用中尚有诸多困难和挑战.本文根据Wapenaar的地震干涉理论,基于上下行波场分离技术,研发了VSP地震干涉成像方法.该方法将VSP自由表面多次波重建为在地表震源位置激发(虚震源)接收的拟地面地震反射波,然后偏移成像,以达到对多次波间接成像的目的.通过数值模型实验,测试了VSP干涉成像的极限分辨率,并讨论了主要采集参数的影响,结果表明:该方法的垂向和水平极限分辨率分别达约10m和20m,且能分辨深度达6500m处的50m×100m溶洞;采用12至24道井中检波器串采集的VSP资料,其干涉成像结果显著优于VSP反射波成像,与相应的地面地震成像效果相当.将本文方法应用于新疆地区采集的VSP资料,结果表明:与VSP反射波成像相比,成像同相轴更加连续,成像范围显著扩大;与地面地震成像相比,成像结果相当,尤其在浅中部甚至更好.新方法不仅无需进行井中接收点静校正,且能显著增大成像范围,有利于成像同相轴的追踪对比、地震属性提取和地质解释,尤其对中国新疆地区深部缝洞型储层的成像,具有广泛的实际应用前景.     

网络信息空间的地理学研究回顾与展望

网络信息空间（以下简称网络空间）的地理学是当前地理学研究的重点方向之一。1991年万维网诞生并向大众普及后网络空间开始得到广泛认可,同时其作为一种新的空间与事物也吸引了地理学界的高度关注。以多种期刊数据库和搜索引擎为检索源,考察国内外网络空间的地理学研究成果。依据研究内容将国外研究归纳为网络空间地理内涵、虚拟社区、虚拟化身与认知、网络空间的经济地理学,网络空间制图和互联网6个重点研究领域,将国内研究归纳为互联网的区域作用、网站和虚拟地理环境3个热点领域,并分别进行了梳理回顾。最后对国内外研究进行了简要评述,从网络空间的外部层面、内部层面和作用层面提出了若干研究议题。     

虚拟现实与计算机动画

虚拟现实与计算机动画方面的研究内容在较长的时期内是一个热点主题,ISPRS将其列为一个专题,对支持摄影测量与遥感的成果展示有积极的促进作用。本文通过归纳和总结2008年ISPRS大会的该专题论文,简要地给出这些论文的主旨,以企为读者提供举纲张目的帮助。这些论文的研究内容集中在3维可视化相关技术方面,包括3维数据获取建模与处理、3维模型数据精简、纹理数据提取、DEM可视化以及巷道可视化方法等。