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1.
Distances between demand points and potential sites for implementing facilities are essential inputs to location-allocation
models. Computing actual road distances for a given problem can be quite burdensome since it involves digitalizing a network,
while approximating these distances by l
p
-norms, using for instance a geographical information system, is much easier. We may then wonder how sensitive the solutions
of a location-allocation model are to the choice of a particular metric. In this paper, simulations are performed on a lattice
of 225 points using the k-median problem. Systematic changes in p and in the orientation of the orthogonal reference axes are used. Results suggest that the solutions of the k-median are rather insensitive to the specification of the l
p
-norm.
Received: 12 October 1998/Accepted: 17 September 1999 相似文献
2.
北京环线建设驱动的土地利用变化遥感检测与分析 总被引：6，自引：0，他引：6
近年来,北京市的环线建设大大改进了北京的交通状况,促进了环线周边的商业发展和房地产开发的繁荣,同时也带来了环线周边地区的土地利用的变更。在“科技奥运”科技攻关项目和在研自然科学基金项目的支撑下,选择了1988,1994,2001和2003年5—6月份的TM数据,在影像经过几何校正和辐射归一化校正后对其应用高精度的自组织神经网络分类和利用高分辨率的航空照片验证;在分类数据和变更信息的基础上,采用了空间自相关分析模型、频率指数模型和潜力模型分别对北京各种用地类型的频率指数和建设用地的Moran系数和Geary系数,以及城市增长的潜力指她进行计算。一系列计算显示了环线驱动的北京市土地利用变化情况。结果表明:在环线建设的驱动下,北京市的建设用地围绕环线呈快速增长趋势;绿地面积在四环、五环的环线一带也呈增加趋势;城市增长潜力从四环到六环呈逐渐增大趋势。 相似文献
3.
Hiroyuki Usui 《Journal of Geographical Systems》2018,20(4):387-412
The structure of road networks has been investigated in accordance with the development of GIScience. By classifying road networks into wide and narrow ones, we can define the route as the path from the route’s origin (also called the root) on a wide road network to a narrow road segment which consists of the sequence of narrow road segments arranged by ascending order of the number of steps of adjacency to its root. The length of the route can be defined with the following geometric and topological terms: the route distance, measuring the length along the route and the depth, counting the number of road segments on the route. The depth plays the important role of being a substitute for the route distance in modelling road networks as a planar graph. Since road networks clearly exhibit irregular patterns and road segment lengths are non-uniform, it is considered appropriate to adopt a stochastic approach rather than a deterministic one to analyse the route distance. However, the relationship between the route distance and its depth has not been sufficiently investigated stochastically. Therefore, the research question is how can we estimate the route distance from its depth? Based on an empirical study in the Tokyo metropolitan region, it was found that (1) the statistical distribution of the route distance can be formulated as an Erlang distribution whose parameters are its depth and the inverse of the mean length of narrow road segments, and (2) this length is constant and close to 40 m. Therefore, we can estimate the route distance from only one parameter, the depth. Also, as a practical application, accessibility to the kth depth link in terms of firefighting was evaluated because the maximum length of the extension of fire hoses is approximately 200 m. It was found that (1) even if k?≤?5, the probability that the route distance to the kth depth link is equal to or longer than 200 m ranges from 0 to 0.45; and (2) if k?≥?8, the probability is approximately 1. These indicate the limitation of the deterministic approach because, on the basis of complete grid patterns (with intervals of 40 m between intersections), k?=?5 corresponds to a distance of 200 m from wide road networks and the route to the 5th depth link can be covered with fire hoses. Moreover, it was found that the connectivity of wide road networks is higher than that of narrow ones in terms of the smaller ratio of cul-de-sacs and the larger ratio of four-way intersections. These answers contribute substantially not only to constructing a science of cities that provides a simple model and specifies the most important parameter, but also to our understanding of the structure of narrow road networks within several hundred metres of wide road networks. 相似文献
4.
以武汉市为研究区域,运用密度分析和空间自相关探索武汉市体育场馆空间分布的聚集性;利用空间二元相关性定量地分析体育场馆空间分布与经济要素、社会要素以及道路网的相关性。结果表明,武汉市体育场馆在中心城区呈聚集并向外围扩散;人口密度、生产总值以及道路网密度都在不同程度上影响着体育场馆的空间布局。武汉市体育场馆的空间分布受经济和交通情况的影响比较大。通过多元回归模型,预测随着武汉城市中心及以外地区经济的发展、道路的完善以及政府的大力支持,乡村郊区的体育场馆数量将不断增多,武汉市体育馆将向着中心城区密集一乡村郊区普及的分布模式转变。 相似文献
5.
6.
Ground-level bus offers flexible services with relatively inexpensive fares and high-level accessibility, thus is the dominant feeder mode for metro in the majority of metropolitan areas in China. Intermodal transfer between the metro and bus networks is therefore a crucial element in the successful operation of an integrated transit system. In this circumstance, a key challenge is lack of appropriate methodologies to evaluate the spatial–temporal disparities of intermodal transfers between metro and bus. To address this issue, this research aims to promote an existing two-step floating catchment area (2SFCA) model by incorporating the temporal variability of service supply, demand, and travel time to provide a more realistic estimation of accessibility using smart card data and automatic vehicle location data. The proposed methodology was applied in a case study of the metropolitan area of Shanghai in the specific context of metro-stop based accessibility to bus services. The results of the case study show that the daily fluctuations in output metro-to-bus transfer accessibility values are highly sensitive to temporal dynamics of transfer time, service supply, and demand. It is hoped the results output here could give planners and policymakers greater insight into spatiotemporal dynamics on transfer accessibility, and help to establish an effective and efficient integrated transit system. 相似文献
7.
Spatial Supermarket Redlining and Neighborhood Vulnerability: A Case Study of Hartford,Connecticut 
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下载免费PDF全文 The disinclination of chain supermarkets to locate or relocate existing stores from inner city impoverished neighborhoods to affluent suburbs is termed ‘spatial supermarket redlining’. This study attempts to map and understand the effects of potential spatial supermarket redlining on food access in urban disadvantaged neighborhoods of Hartford, Connecticut. Using a combination of statistical and spatial analysis, we first built a Supermarket Redlining Index (SuRI) from five indicators (sales volume, employee count, accepts food coupons from federally assisted programs, and size and population density of the service area) to rank supermarkets in the order of their importance. Second, to understand the effects of supermarket closures in the inner city, a Supermarket Redlining Impact Model (SuRIM) was built with 11 indicators describing both socioeconomic and food access vulnerabilities. The interaction of these vulnerabilities identified neighborhoods that are maximally impacted by spatial supermarket redlining. Results mapped critical areas in the inner city of Hartford where, if a nearby supermarket closed down or relocated to a suburb with limited mitigation efforts to fill the grocery gap, a large number of minority, poor, and disadvantaged residents would experience difficulties to access healthy food, leading to food insecurity or perhaps a food desert. In conclusion we suggest mitigation efforts to reduce this impact of large supermarket closures. 相似文献
8.
城市公路网络服务与供给和需求密切相关,衡量区域的公路网络服务水平不能单纯从公路网密度出发,需要将供给与需求相结合进行分析。文章以GIS为基础平台,从网络服务供给与需求的相互协调关系出发,通过定量与定性相结合的方法,采用模糊聚类方法以聊城市8县市为样本分区,对公路网络服务水平进行分析评价,结果为:以相似系数在0.9以上为标准,把聊城市8个样本分为高、较高、中等、较低4个类型区,东阿、高唐为综合服务水平高类型;茌平为综合服务水平较高类型;阳谷为综合服务水平中等类型;东昌府、冠县、莘县、临清为综合服务水平较低类型。 相似文献
9.
The vector assignment p-median problem (VAPMP) (Weaver and Church in Transp Sci 19(1):58–74, 1985) was one of the first location-allocation models developed to handle split assignment of a demand to multiple facilities. The underlying construct of the VAPMP has been subsequently used in a number of reliable facility location and backup location models. Although in many applications the chance that a facility fails may vary substantially with locations, many existing models have assumed a uniform failure probability across all sites. As an improvement, this paper proposes a new model, the expected p-median problem as a generalization of existing approaches by explicitly considering site-dependent failure probabilities. Multi-level closest assignment constraints and two efficient integer linear programming (ILP) formulations are introduced. While prior research generally concludes that similar problems are not integer-friendly and cannot be solved by ILP software, computational results show that our model can be used to solve medium-sized location problems optimally using existing ILP software. Moreover, the new model can be used to formulate other reliable or expected location problems with consideration of site-dependent failure probabilities. 相似文献
10.
智能导游服务已从传统的单一景区导游发展为城市多景区导游,因此,包含了景区间导游和景区内导游两大部分;表现为更加注重面向散客服务、兼容多移动智能终端以应用程序（App）的方式运行。由于景区间导游和景区内导游往往自成系统,在游客进出景区的过程中存在着两种系统的切换,且主要采用手动方式完成,尚没有实现城市多景区导游过程的无缝衔接。为了应对这个挑战,本文设计了一个面向城市多景区的无缝导游服务模式,分析了其架构以及工作机制;并着重讨论了城市无缝导游服务的关键技术,如系统间无缝切换的条件,包含判断游客进入、离开景区等;以及导游服务过程无缝衔接的机制,包含导游动态数据结构的设计,游客游览需求、导游过程状态在多导游系统间的传递等。最后通过实例验证了该方法的有效性,作为新的导游服务模式,同时为动态集成已有的导游App提供了解决方法。 相似文献
11.
基于数据挖掘的宁波市公共自行车使用特征 总被引：1，自引：0，他引：1
运用ArcGIS10.2和SPSS22.0软件对宁波市中心城区公共自行车的IC卡数据、区域属性数据、POI网络开放数据进行了综合分析，发现：①宁波市公共自行车使用时空分异明显，呈现圈层结构。内圈层和中圈层自行车使用量大、潮汐不明显、泊位周转率高；外圈层和外围区具有使用量小、潮汐性强、泊位周转率低的特征。②公共自行车使用与人口密度、医疗保健网点、教育机构、餐饮服务、公园数、早高峰时段、晚高峰时段具有明显正相关关系；与地铁站点数、公司企业数量、绿地广场存在明显负相关关系。 相似文献
12.
黄萌 《测绘与空间地理信息》2018,(3):46-49,52
公共服务设施的布局是否合理关系到居民的生活质量,关系到新城能否实现为中心城疏解人口及功能的规划目标,因此,对中心城、新城公共设施布局公平性和合理性的研究具有重要的科学和现实意义。本文基于GIS,结合人口数据、步行路网数据,分析了中心城、新城公共服务设施可覆盖人口、服务面积及存在的问题,对于优化北京市公共设施的布局具有一定的借鉴意义。 相似文献
13.
非监督分类的冬小麦种植信息提取模型 总被引：1，自引：0，他引：1
为了解决在区域冬小麦种植信息遥感提取过程中监督学习算法存在的需要地面样本数据支持、流程复杂、人为干扰因素多及自动化程度低等问题，本文以非监督分类为核心，结合多尺度技术，提出了一种新的非监督分类冬小麦种植信息提取模型。选取河北省辛集市为典型试验区，以2014年高分一号数据为数据源，对本文提出的模型进行实例验证。试验结果表明：该模型的Kappa系数为0.88，整体精度为94.00%；对于研究区内的冬小麦，在无需训练样本、人为干扰因素少等条件下，该模型具有与监督分类相似的提取精度，能够满足冬小麦种植信息地面遥感监测的需求。 相似文献
14.
谭敏 《测绘与空间地理信息》2015,(7)
以车载激光点云数据为研究对象,提出了一种新的路面检测与重建的方法。该方法根据GPS定位器中的索引文件或激光扫描仪的旋转角度值提取扫描车的车行路径,利用提取到的车行路径去检测对应的路沿。然后,对检测到的路沿中出现的各种异常进行相应的平滑处理。在得到精确的路沿线后,可得到路面的三维模型,从而完成对路面的重建。输出的路面三维模型为OBJ格式,可满足相关领域对精确路面的需求,比如三维城市建模。 相似文献
15.
道路网络通达性是区域交通体系建设所要考虑的重要方面。本文以GIS为技术手段,通过重力度量模型、道路加权和密度模型计算得出经济联系指数和道路加权核密度指数,并构建综合通达性指数来分析湖北省县域道路网络综合通达性及其空间特征分布。结果表明:(1)湖北省103个县经济联系指数以武汉市主城区最高;(2)道路加权核密度指数以武汉市东西湖区最高;(3)道路网络综合通达性最高的5个县级行政单元为硚口区、汉阳区、江岸区、江汉区、东西湖区。本文填补了目前国内省级交通网络通达性方面的研究空白,为湖北省道路交通网络的建设和布局优化提供了参考依据。 相似文献
16.
城市的制度转型和空间重构加剧了职住分离现象,降低了居民就业可达性,土地利用景观格局特征是影响居民就业可达性的因素之一。基于经济普查、人口普查数据以及2010年和2014年两期土地利用数据,对武汉市中心城区街道尺度的居民就业可达性进行分析,定量描述土地利用景观格局对居民就业可达性的影响。研究结果表明,景观格局指数中景观尺度的边缘密度、香农多样性指数和斑块类型尺度的斑块面积、斑块占景观面积比例、回旋半径、聚合度均对就业可达性有显著影响;就业类斑块特征对居民就业可达性的影响比居住类斑块更大,居住区规划应考虑周边就业岗位数量;土地利用多样性、斑块分布紧实度的提升均有助于提高居民就业可达性。 相似文献
17.
The initial acquisition of direct-sequence spread-spectrum (DSSS) signal transmitted in bursts by ground terminals at satellite-borne receiver poses an engineering challenge. We propose a low-complexity acquisition algorithm that is capable of capturing extremely weak DSSS signal in the presence of large Doppler dynamics. The algorithm uses fast Fourier transform (FFT)-based frequency-domain techniques to implement circular correlations between the received signal and the local pseudo-random noise (PRN) code, and it coherently accumulates the correlation results across multiple PRN code periods, to achieve a sufficient signal–noise ratio for reliable acquisition. We invoke another FFT procedure to perform the coherent accumulation and the fine compensation for the residual Doppler frequency offset. To highlight the advantage of the proposed algorithm, we make a complexity comparison among the proposed algorithm and two other benchmark strategies, namely the modified double block zero padding (MDBZP) and two-dimensional exhaustive search (2D-ES). It is shown that the proposed algorithm has the lowest complexity, which is particularly desirable for satellite-borne receivers where the computational resource is limited. The acquisition performance of the proposed algorithm is verified by theoretical analysis and Monte Carlo simulations and compared with that of MDBZP and 2D-ES. Moreover, we have carried out extensive tests on a hardware verification system, and we show the claimed tradeoff between performance and cost is indeed attainable with the suggested algorithm. Numerically, it is found the proposed algorithm can achieve a detection rate of 0.9 and a false alarm rate of \(10^{ - 5}\) at C/N 0 = 29.5 dBHz over a Doppler frequency offset range of \(\left[ { - 7.5\,{\text{kHz}},7.5\,{\text{kHz}}} \right]\) in floating-point simulation, which coincides with the analytical results. The same performance is achieved at C/N 0 = 31 dBHz in fixed-point simulation and at C/N 0 = 31.5 dBHz on a hardware system. 相似文献
18.
Hichem Mahgoun Mounira Ouarzeddine 《Journal of the Indian Society of Remote Sensing》2017,45(2):217-228
Tomographic-SAR (Synthetic Aperture Radar) is a 3D Radar imaging technique, based on spectral estimation tools. This technique is used to estimate the distribution of the backscattering signal in the elevation axis, for each azimuth-range resolution cell of the SAR image. Spectral estimation algorithms belong to two families, non parametric estimation algorithms which include DFT (Discrete Fourier Transform), SVD (Single Value Decomposition), MUSIC (Multiple Signal Classification), CAPON and parametric estimation algorithms such as LS (Least Square) and ESPRIT (Estimation of signal parameters via rotation invariance techniques). In this paper we present an inversion algorithm based on the fusion of DFT and LS for the estimation of the reflectivity signal along the elevation axis. With an appropriate combination of these two algorithms and a realistic modeling of the signal distribution, we obtain a high resolution estimate of the reflectivity signal with medium computational effort. The inversion algorithm is tested on a forested area (Västerbotten in northern Sweden), with multibaseline data set acquired in L-band (BioSAR-2008 project). Results are promising with the proposed algorithm. We used MUSIC and RVoG (Random Volume over Ground) inversions for comparison and LIDAR (Laser Imaging Detection And Ranging) image as datasets for validation of the results. 相似文献
19.
Line Eikvil Lars Aurdal Hans Koren 《ISPRS Journal of Photogrammetry and Remote Sensing》2009,64(1):65-72
In this study, we have looked into the problem of vehicle detection in high-resolution satellite images. Based on the input from the local road authorities, we have focused not only on highways, but also on inner city roads, where more clutter is expected. The study site is the city of Oslo, Norway. To do vehicle detection in these areas, we propose an automatic approach, consisting of a segmentation step, followed by two stages of object classification. In the process, we utilize multispectral images, panchromatic images and a road network. The approach has been tested on Quickbird images, and the results that are obtained have been compared with manual counts and classifications. 相似文献
20.
Absolute orientation is a basic technical work in digital image geologic logging of underground coal mine. Traditional control-point-based absolute orientation method requires setting object space control points of the known three-dimensional coordinates, which may lead to low efficiency. Therefore, this paper proposed a point-free close-range photogrammetry absolute orientation algorithm, which utilized direction line segments including plumb line segments and line segments with known directions and lengths to identify the dimensional orientation of a stereoscopic model. Experiment results show that the precision of the orientation results is favorable. σ X and σ Y are as high as 0.5 mm, and σ Z is 0.3 mm. Finally, this paper introduced the application of the proposed algorithm in rapid geological logging of coal mine roadway, which was fast and reliable, convenient and feasible. 相似文献