共查询到20条相似文献，搜索用时 93 毫秒
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本文基于导线测量的误差源,阐述了误差匹配的内涵及导线测量精度的要求,并结合导线网的机助法精度估算等情况,对控制测量工作提出一些建议。 相似文献
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对镇江市原有地籍GPS控制网的检测技术方案以及检测过程中的技术要求进行了介绍，并对在GPS控制网基础上加密的一、二级导线精度进行了估算。 相似文献
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吴俊昶 《武汉大学学报(信息科学版)》1986,(3)
目前导线网平差多采用相关平差法。按该法在网(结点)平差时计算未知数的协因数阵,可以评定结点的点位精度。文献[2]等均未曾论及各个导线点的精度评定问题。实际上,导线网中的最弱点不一定出现在结点内,为此需全面评定导线点的精度。本文将专门论述导线网相关平差中导线点的精度评定问题。 相似文献
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用红外测距仪布设导线网已十分普遍，当以导线网作为首级控制时一般宜布成网格化导线，而四等及四等以上的控制测量均要采用严密平差，从实践出发，本文将较详尽地对这一问题进行研讨。 相似文献
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Studies on small-world networks have received intensive interdisciplinary attention during the past several years. It is well-known
among researchers that a small-world network is often characterized by high connectivity and clustering, but so far there
exist few effective approaches to evaluate small-world properties, especially for spatial networks. This paper proposes a
method to examine the small-world properties of spatial networks from the perspective of network autocorrelation. Two network
autocorrelation statistics, Moran’s I and Getis–Ord’s G, are used to monitor the structural properties of networks in a process of “rewiring” networks from a regular to a random
network. We discovered that Moran’s I and Getis–Ord’s G tend to converge and have relatively low values when properties of small-world networks emerge. Three transportation networks
at the national, metropolitan, and intra-city levels are analyzed using this approach. It is found that spatial networks at
these three scales possess small-world properties when the correlation lag distances reach certain thresholds, implying that
the manifestation of small-world phenomena result from the interplay between the network structure and the dynamics taking
place on the network.
相似文献
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To delineate channel networks from DEMs regardless of landform type, this article proposes a new method using slope-weighted flow accumulation. To validate the method, SRTM-3, a global DEM dataset with a resolution of approximately 90 m, was used for analysis of the Loess Plateau, China. Channel networks delineated with and without slope-weighted flow accumulation were derived in both uplands and hilly lands for comparison. In the weighted flow accumulation method, the thresholds for delineating the channels were defined by detecting a turning point in the frequency distribution of the weighted flow accumulation function or by visual similarity with drainage channels extracted from topographic maps. The channel networks delineated with weighting showed closer correlation with a topographic map than the channel networks without weighting, despite the differences in thresholds. Moreover, the channel networks delineated with weighting represented the differences between landform types, while the channel networks without weighting did not. Weighting on the basis of the slope angle shows promise as a general channel delineation method which reflects the actual topography due to its hydrogeomorphological functions. 相似文献
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基于空间统计特征的河网结构分类 总被引：2，自引：0，他引：2
提出了基于特征因子进行空间数据库河网结构分类的方法和技术。探讨了各种类型河网的特征，阐述了时河网进行分类的因子及河网分类的方法和过程，描述了河网数据的有向图组织厦其分类实验。 相似文献
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Computer networks like the Internet are gaining importance in social and economic life. The accelerating pace of the adoption
of network technologies for business purposes is a rather recent phenomenon. Many applications are still in the early, sometimes
even experimental, phase. Nevertheless, it seems to be certain that networks will change the socioeconomic structures we know
today. This is the background for our special interest in the development of networks, in the role of spatial factors influencing
the formation of networks, and consequences of networks on spatial structures, and in the role of externalities. This paper
discusses a simple economic model – based on a microeconomic calculus – that incorporates the main factors that generate the
growth of computer networks. The paper provides analytic results about the generation of computer networks. The paper discusses
(1) under what conditions economic factors will initiate the process of network formation, (2) the relationship between individual
and social evaluation, and (3) the efficiency of a network that is generated based on economic mechanisms.
Received: 5 July 2000 / Accepted: 28 November 2000 相似文献
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Geographical impacts on social networks from perspectives of space and place: an empirical study using mobile phone data 总被引：2，自引：0，他引：2
Space and place are two fundamental concepts in geography. Geographical factors have long been known as drivers of many aspects of people’s social networks. But whether and how space and place affect social networks differently are still unclear. The widespread use of location-aware devices provides a novel source for distinguishing the mechanisms of their impacts on social networks. Using mobile phone data, this paper explores the effects of space and place on social networks. From the perspective of space, we confirm the distance decay effect in social networks, based on a comparison between synthetic social ties generated by a null model and actual social ties derived from real-world data. From the perspective of place, we introduce several measures to evaluate interactions between individuals and inspect the trio relationship including distance, spatio-temporal co-occurrence, and social ties. We found that people’s interaction is a more important factor than spatial proximity, indicating that the spatial factor has a stronger impact on social networks in place compared to that in space. Furthermore, we verify the hypothesis that interactions play an important role in strengthening friendships. 相似文献
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基于BP神经网络的点状地图符号识别 总被引：7，自引：0，他引：7
点状地图符号的识别是实现扫描方式地图自动数字化的重要研究内容之一，本文首先分析介绍ＢＰ网络模型及其学习算法，然后根据ＢＰ模型本身所存在的一些不足之处，提出相应的改进措施，还以实际扫描地图图像进行相应的实验验证，最后，对网络的输入模式加以讨论，提出了三种减小网络规模的具体方法。 相似文献
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LIUGang 《地球空间信息科学学报》2005,8(1):28-32
This paper focuses on the image segmentation with probabilistic neural networks (PNNs). Back propagation neural networks (BpNNs) and multi perceptron neural networks (MLPs) are also considered in this study, Especially, this paper investigates the implementation of PNNs in image segmentation and optimal processing of image segmentation with a PNN. The comparison between image segmentations with PNNs and with other neural networks is given. The experimental results show that PNNs can be successfully applied to image segmentation for good results. 相似文献
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道路网元胞的组成及其配置构成了特定的网络景观,受启发于元胞和景观格局中斑块的相似性,借鉴景观格局分析中的景观指数分析法,提出了一种城市道路网元胞模式分析的新方法——网络景观指数分析法。该方法基于道路类型生成不同类别的元胞,计算网络景观指数,并通过相关分析与因子分析挖掘主要因子,进而解释主要因子及代表指数在道路网模式分析中的含义。应用该方法计算了中国34个城市街道网络的24个指标,发现了4个主要因子:元胞的空间分布与多样性、元胞最大尺寸与延展性差异、元胞平均延展性和元胞平均尺寸与形状复杂度。反映到道路网中,描述了道路的集聚与分散特征、道路类型的多样性、道路网的规则程度等特征。 相似文献
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本文分析了不同类的三维空间定位网(简称为空间网或三维网)联合处理时,坐标转换摸型定义上的差别,从统计学角度定义了空间网系统性尺度误差,区分和讨论了不同类空间网的不同尺度特性,在提出理论模型的基础上,分析了各类空间网联合处理时的实用转换模型的特性和偏差。最后,提出了多类空间网联合处理时的最佳转换模型。 相似文献