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数字高程模型地形描述精度量化模拟研究 总被引:65,自引:3,他引:65
在首先提出数字高程模型(DEM)地形描述误差(Et)概念的基础上,以我国5个不同地貌类型区为试验样区,采用比较分析的方法,研究EDEM地形描述误差的成因、影响因素、量测方法以及误差的数学模拟途径。统计分析的结果证明DEM地形描述误差与DEM空间分辨率及其地面粗糙度之间存在着线性相关关系,回归分析结果显示,DEM地形描述误差Et的均方差RMS值可以表达为DEM水平分辨率(R)与地面垂直曲率(V)的函数:RMS Et=(0.0063V 0.0066)R-0.022V 0.2415。该结果可用以估算估算所建立的DEM的地形描述精度,也为确定适宜的DEM分辨率提供了理论依据。 相似文献
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当前GIS软件中通视分析建立在DEM数据基础上,而DEM中不含植被和建筑物信息,从而会造成通视分析误差。通过Li DAR点云数据获取高精度植被和建筑物高度,提出一种顾及地物的插值算法,生成同一网格大小的DEM与DSM,在其上分别进行通视域分析,并将分析结果进行对比,发现DEM比DSM更容易扩大视域范围,从而产生了分析误差,验证了利用DSM进行通视分析的可行性。 相似文献
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火星表面含水矿物探测进展 总被引:1,自引:0,他引:1
火星表面含水矿物类型识别和空间分布特征研究对圈定火星表面生命活动有利区域和探索可能存在的火星生命形式具有重要科学意义。本文总结了20世纪90年代以来火星表面含水矿物的探测进展,从火星轨道器光谱仪遥感探测、着陆器和巡视器就位探测两方面介绍了矿物探测使用的数据源,重点阐述了目前火星表面已经探测到的各类含水硅酸盐矿物、硫酸盐矿物、碳酸盐矿物、氯盐及高氯酸盐矿物等含水矿物的光谱特征、矿物具体类别及分布特征,分析了火星表面含水矿物定量反演的主要方法与地质意义。最后从比较行星学角度倡议开展地球和火星含水矿物形成环境和形成过程的类比研究。 相似文献
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Background
Climate variability modifies both oceanic and terrestrial surface CO2 flux. Using observed/assimilated data sets, earlier studies have shown that tropical oceanic climate variability has strong impacts on the land surface temperature and soil moisture, and that there is a negative correlation between the oceanic and terrestrial CO2 fluxes. However, these data sets only cover less than the most recent 20 years and are insufficient for identifying decadal and longer periodic variabilities. To investigate possible impacts of interannual to interdecadal climate variability on CO2 flux exchange, the last 125 years of an earth system model (ESM) control run are examined. 相似文献15.
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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To determine the distribution of positional error of a line segment, Monte Carlo approach is applied to simulate the probability density function of a line segment with the assumption that the error of endpoints in a line segment follows a two-dimensional normal distribution. For such purpose, a stochastic generator used for uncertain endpoints with the two-dimensional normal distribution is presented. This forms the basis of the generation of random line segment for the simulation of the error model of a whole line segment. The error models cover the cases where two endpoints are either independent or dependent to each other, also including a special case that the distance between two random endpoints in a line segment is close enough. 相似文献
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通过遥感影像云量数据和地面站点日照百分率观测数据建立遥感集成日照百分率模型,模拟遥感集成日照百分率的空间分布。基本思路是以空间尺度上的富余弥补时间尺度上的稀缺。云的移动是连续的,所以一幅云量遥感影像中,某一格网点周围一定区域范围内的云量都有可能对该点日照情况产生影响,因此对遥感总云量数据在日照轨迹内及云移动所经路径内重采样,能够更接近可照时段内云量的真实情况。然后按云量和日照百分率的负相关性,建立了日尺度的日照百分率遥感集成综合模型,实现对遥感集成日照百分率的模拟,完成日照百分率的遥感集成空间分布模拟图。结果表明:(1)重采样后的总云量克服了云量观测在时间上的局限性;(2)遥感集成日照百分率克服了气象站点空间上的局限性;(3)遥感集成日照百分率模型模拟精度相对插值法有显著的提高。 相似文献
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搜索技术是当前网络领域中最为热门的研究领域,搜索引擎的好坏在很大程度上决定了用户使用网络资源的效率高低。搜索引擎的效率主要是取决于系统对用户输入检索词的解析与识别。因此一个好的搜索引擎需要能够对用户输入的信息进行语义解析,准确有效地对用户意图进行识别、解析与理解,并为用户返回最为合适的搜索结果。本文设计开发了一种基于元数据的网络搜索语义识别算法,并成功应用于中国可持续发展信息共享系统中,建立基于可持续发展元数据的搜索引擎,对用户的不同需求提供不同的元数据搜索方式,最终根据可持续发展共享数据与元数据的映射关系,实现由基于数据分类存储模式的数据共享服务转变为以元数据搜索为驱动的数据共享服务模式,为用户提供了高效的可持续发展元数据搜索引擎,极大提高了中国可持续发展信息共享系统的数据共享服务能力。 相似文献