共查询到20条相似文献，搜索用时 125 毫秒
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分析了事件与状态的关系,对基态修正模型加以改进,根据事件发生的频繁程度及每次数据量更新的大小,建立历史基态,对于历史基态间的地理实体数据只记录其相对于历史基态的变化部分.既克服了基于快照时空数据模型产生的大量冗余数据,又克服了基态修正模型随着修正次数的增加,历史重构需要大量的复杂计算的缺陷,具有历史数据恢复快的优势. 相似文献
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地形图建筑物时空数据模型研究 总被引：2，自引：0，他引：2
论述地形图更新和建立地形图时空数据库的必要性,总结时空数据模型的几种类型,认为城市大比例尺地形图时空数据库的建设采用基态修正模型是适宜的.分析城市建筑物更新的几种类型并将其分解为3种基本类型.给出基态修正模型中基态值和差值的实现方法.实验表明用基态修正模型派生得到的地形图与外业修测得到的地形图是一致的,可以通过基态和差值实现历史数据的恢复. 相似文献
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一种基于动态基态方法的时空数据模型扩展 总被引：1，自引：0，他引：1
分析现有时空数据基态修正模型研究的进展,提出一种基于动态基态的时空数据基态修正方法,引入动态基态数据与动态数据存储区域的概念,解决重复检索历史数据以及对时间段的检索效率低下的问题,具有基态数据占用空间较小、数据检索速度快的特点,且当历史年代久远时,存储空间最小。 相似文献
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方辉 《测绘与空间地理信息》2007,30(3):97-99,103
介绍了各种常用的时空数据模型,并重点介绍了基态修正模型及其扩展模型,分析比较了各种基态修正模型的扩展模型的优缺点,在此基础上提出了一种新的基态修正模型的改进模型,并分析了该模型的优缺点。 相似文献
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基态修正模型是目前应用较广的一种时空数据模型。本文分析了基态修正模型中的时空数据特点,采用shapefile文件作为基态数据文件,自主设计差文件格式来存储和组织变化数据。在此基础上设计了快照查询的算法、流程和查询结果的显示方法。为了给用户提供更直观、更充分的时空信息,本文提出了一种双屏幕多视图的时空数据显示模式。采用VC．NET从底层开发了一个时态地理信息系统平台,并以中南大学主校区的时空数据为实验数据对上述算法和模式进行了检验。实验表明,本文所设计的算法可行,快照显示模式能够提供更直观、更丰富、对比性强的信息内容,是时空信息显示的一种可行模式。 相似文献
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基于三维时空数据库的地信时空过程可视化研究 总被引：1，自引：0，他引：1
随着GIS数据不断更新,大量的GIS历史数据也不断累积起来。本文即是着眼于如何有效利用累积下来的多个时期的数据,模拟地信时空过程,让人们能直观了解空间信息的发展变化过程。论文先介绍了由地理信息时空数据建立的三维时空数据库,然后阐述了在此数据库支持下的地信时空过程可视化的实现技术。本文的研究是一次时态GIS与3D-GIS结合应用的尝试,实现了4D概念下更为逼真和动感的地理信息服务方式。 相似文献
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Space-time accessibility measures: A geocomputational algorithm with a focus on the feasible opportunity set and possible activity duration 总被引：12，自引：2，他引：12
Space-time accessibility measures have received much attention in recent years due to their sensitivity to differences in
individual ability to participate in activities in space and time. Despite the conceptual attractiveness and robustness of
space-time measures, only few attempts have been made to operationalize them to date. Research that seeks to improve space-time
accessibility measures is still sorely needed. This study seeks to enhance space-time accessibility measures through developing
a new operational method and GIS-based algorithm that better represents the space-time characteristics of urban opportunities
(e.g. their geographical distribution and opening hours) and human activity-travel behavior (e.g. delay times, minimum activity
participation time, and maximum travel time threshold). The proposed method not only takes into account the number and size
of opportunities, but also the possible activity duration at each activity location given its opening hours and the effect
of transport network topology (e.g. one-way streets, turn restrictions and over-pass). Incorporating these elements into space-time
measures helps overcome several shortcomings of previous approaches to evaluating space-time accessibility.
Received: 15 September 2002 / Accepted: 10 February 2003
A version of this paper was presented at the 98th Annual Meeting of the Association of American Geographers, Los Angeles,
March 19-23, 2002. We thank Joe Weber for providing the digital transport network with travel speeds and a version of the
geocomputational algorithm he used in his study (Weber 2001), upon which our developmental effort has been based. We are also
grateful to the helpful comments and suggestions of the reviewers. 相似文献
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信息技术的快速发展带来了"大数据"时代的到来,使得城市时空行为研究面临变革。传统的城市时空行为研究方法并不能涵盖居民空间移动的复杂性和工作生活的移动性。随着智能手机的普及,微博也成为人们日常生活中常用的社交网络。本文通过获取新浪微博的签到数据,应用GIS软件分析北京地区居民行为的时空间关系。研究发现:工作日的热点要比周末集中很多,上下班高峰期多条地铁线路客流量较大,北京地区办公地区比居住地更加集中。 相似文献
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A Space-Time GIS Approach to Exploring Large Individual-based Spatiotemporal Datasets 总被引：3，自引：0，他引：3
The increasing number of large individual-based spatiotemporal datasets in various research fields has challenged the GIS community to develop analysis tools that can efficiently help researchers explore the datasets in order to uncover useful information. Rooted in Hägerstrand's time geography, this study presents a generalized space-time path (GSTP) approach to facilitating visualization and exploration of spatiotemporal changes among individuals in a large dataset. The fundamental idea of this approach is to derive a small number of representative space-time paths (i.e. GSTPs) from the raw dataset by identifying spatial cluster centers of observed individuals at different time periods and connecting them according to their temporal sequence. A space-time GIS environment is developed to implement the GSTP concept. Different methods of handling temporal data aggregation and the creation of GSTPs are discussed in this article. Using a large individual-based migration history dataset, this study successfully develops an operational space-time GIS prototype in ESRI's ArcScene and ArcMap to provide a proof-of-concept study of this approach. This space-time GIS system demonstrates that the proposed GSTP approach can provide a useful exploratory analysis and geovisualization environment to help researchers effectively search for hidden patterns and trends in such datasets. 相似文献
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李作发 《武汉大学学报(信息科学版)》1990,(4)
本文提出了多体时空大地测量边值问题的各种形式,并且在球近似的假设下,给出了边值问题的解,本文还对所得到的解进行了讨论,结果表明:已有的一些解可以作为本文的特例包括在内。 相似文献
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在卫星定位中,观测环境的优劣对最终定位结果精度有着显著性影响,单GPS系统因为其可观测卫星颗数少和自身星座分布的共同影响,载波相位周跳频繁,定位解的误差大、可靠性低、稳定性差。本文对多模GNSS （ Global Navigation Satellite System ）解算中时空系统的统一,组合单点定位模型和差分定位模型等关键技术进行了研究,实现了多模GNSS组合定位,改善了卫星相对于测站的几何分布,环境适应性加强,使得定位精度、系统冗余度和可靠性大幅提高,最后使用车载数据进行实验验证。验证结果表明,多模GNSS观测卫星数相比单GPS系统而言,观测卫星数增加了2倍,PDOP值降低了42％,极大地提高了差分定位解的成功率,固定解比例提高了18．3％。这充分说明了多模GNSS统一定位的可行性和优越性。 相似文献
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Concerns over the potential negative health effects from exposure to air pollution have led to interest in assessing personal exposure and finding ways to reduce it. As journey-time exposure accounts for a disproportionately high amount of an individual's total exposure, this article assesses the potential to apply least-cost techniques within a GIS in order to identify paths of lower journey-time exposure. The methodology adopted uses pollution surfaces for PM10 and CO generated by the dispersion model ADMS, with an analysis mask derived from OS MasterMap to create a least-cost surface. Actual routes taken by a cohort of 11–13 year old children on their journeys to school are used to compare observed journey time exposure with the exposure along alternative routes generated using the least-cost path function. While the least-cost approach proved to be successful in defining low exposure routes the ability to scale up this approach is constrained by the amount of editing required to successfully create an analysis mask from OS MasterMap data. Such alternative routes have the potential to assist in promoting safer environmental choices, however, their likelihood of adoption is dependant on a number of social and environmental influences which affect an individual's route choice. 相似文献
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针对植被对降水响应分析的多为年际尺度且多用气候影响因子分析的问题,本文提出了一种年际与季节性相结合的时间尺度、气候与土壤因子并重的空间相关性分析法.该方法从降水的季节性规律、植被的物候期角度研究植被的年际、季节性空间变化特征,实现了不同时间尺度、空间尺度上植被变化对降水过程的响应情况的分析研究.研究表明:从季节和年际尺... 相似文献
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针对空时二维滤波器结构,提出了修正两步最小均方波束形成算法,通过修正每次迭代运算中的期望阵列响应幅度和方向矩阵,显著地减少了矩阵运算量,达到快速准确求解期望方向图的相位和相应权矢量的目的。该算法在不改变天线阵元数的情况下,比传统空域滤波增加了时域处理维数,提高了波束形成质量,并利用了期望方向图相位的随机性,通过迭代更新期望方向图的相位和相应权矢量,实现了方向图的旁瓣控制,理论上可以形成任意控制的旁瓣波束,满足不同应用场合的需求。经计算机仿真实验,算法可以很好的收敛到期望的方向图,验证了该算法的有效性。该算法可广泛应用于多天线的GNSS导航接收机或抗干扰接收机中,在提高接收机在复杂环境下的可用性和灵敏度上具有重要的意义。 相似文献