共查询到20条相似文献，搜索用时 15 毫秒
1.
A multi‐temporal sequence of seven NOAA‐n, Advanced Very High Resolution Radiometer (AVHRR) satellite scenes (April 10, May 18, June 6, June 29, July 20, and August 18, 1987) were composited to derive cover‐type information in the heterogeneous landscape of University Lake Watershed, North Carolina, U.S.A. The Normalized Difference Vegetation Index (NDVI) was calculated for each scene and merged into a seven‐dimensional dataset, representing each time period sampled. An unsupervised classification was performed on the multi‐temporal composite to derive five cover‐type classes. Similar classifications were generated on single scene information. Ground control information was derived from an unsupervised classification of one kilometer grid compositional percentages initially derived from photo‐interpreted landcover information. The multi‐temporal NDVI classification more consistently characterized phenologic responses on a spatially dissected landscape than single scene clustering. Sub‐pixel information showed how the algorithm separated compositional information between classes. Temporal vectors were plotted to illustrate differentiation on the basis of NDVI profiles. 相似文献
2.
Accessibility Futures 总被引：1，自引：0，他引：1
This study uses accessibility as a performance measure to evaluate a matrix of future land use and network scenarios for planning purposes. The concept of accessibility dates to the 1950s, but this type of application to transportation planning is new. Previous research has established the coevolution of transportation and land use, demonstrated the dependence of accessibility on both, and made the case for the use of accessibility measures as a planning tool. This study builds off of these findings by demonstrating the use of accessibility‐based performance measures in the Twin Cities Metropolitan Area. This choice of performance measure also allows for transit and highway networks to be compared side‐by‐side. For roadway modeling, zone‐to‐zone travel time matrix was computed using stochastic user equilibrium (SUE) assignment with travel time feedback to trip distribution. A database of schedules was used on the transit networks to assign transit routes. This travel time data was joined with the land use data from each scenario to obtain the employment, population, and labor accessibility from each traffic analysis zone (TAZ) within specified time ranges. Tables of person‐weighted accessibility were computed for 20 minutes with zone population as the weight for employment accessibility and zone employment as the weight for population and labor accessibility. Maps of accessibility by zone were produced to show the spatial distribution of accessibility across the region. The results show that a scenario where population and employment growth are concentrated in the center of the metropolitan area would produce the highest accessibility no matter which transportation network changes are made. However, another scenario which concentrates population growth in the center of the metropolitan area and shifts employment growth to the periphery consistently outperforms the scenario representing the projected 2030 land use without any growth management strategy. 相似文献
3.
基于GIS的公交可达性指数算法 总被引：2，自引：0，他引：2
借助于GIS空间分析方法,以福州市金山新区为例,对公交可达性的问题进行了探讨。研究过程中建立了研究区范围内包括交通网络信息的地理空间数据库,并通过综合考虑相关影响因子,提出了一种公交可达性指数的计算方法,并进行实地价。这一算法可为选址分析等各类问题提供相对定量化的公交可达性信息。 相似文献
4.
针对城市地理时空数据的专业类别多、数据格式多、数据分散等诸多特性,提出了栅格式数据、图形式数据、要素式数据、类GIS数据、ArcGIS数据5大类地理时空数据的管理方案。采用基于富客户端的地图增强技术、基于时间帧的时空数据动态表达技术和空间数据及平台功能自扩展定制技术,对城市地理时空大数据管理与应用平台进行了总体设计,开发了集管理与应用于一体的资源创建与管理系统、信息集成共享系统、数据交互应用系统,实现了城市地理时空大数据的管理与应用的高效性。本文提出的技术方法已在长沙市规划交通勘测信息集成管理与应用共享平台项目建设中得到验证,为城市地理时空大数据的集成管理和共享应用提供了技术经验。 相似文献
5.
针对现有库容遥感监测方法对无湖盆数据区域的湖泊动态库容难以直接测算问题,提出了未知湖泊水下地形数据的遥感湖泊动态库容监测方法。该方法通过多源遥感数据,匹配相对时相的湖泊面积和水位信息,构建并模拟湖盆DEM数据,据此来估算湖泊的动态库容。在算法实现上,首先采用分布迭代水体提取从遥感影像提取湖泊的多期动态边界;其次,从ICEsat GLAS激光测高数据中反演出湖泊的动态水位高程;第三,依据时间水位信息,通过邻近时相匹配,将水位高程赋给湖泊边界线,生成湖泊等水位线;第四,通过等水位线构建TIN(triangulated irregular network)和Kriging插值,得到模拟湖盆数字高程模型;最后,依据模拟湖盆DEM和水体面积分布、水位信息,计算湖泊动态库容。试验通过对博斯腾湖的多年动态库容监测与真实性检验,结果显示:最大误差为2.21×108 m3,最小误差为0.000 02×108 m3,平均误差为0.044×108 m3,均方根为0.59,相关系数达到0.99。 相似文献
6.
A Space‐Time Raster GIS Data Model for Spatiotemporal Analysis of Vegetation Responses to a Freeze Event 
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下载免费PDF全文 Many past space‐time GIS data models viewed the world mainly from a spatial perspective. They attached a time stamp to each state of an entity or the entire area of study. This approach is less efficient for certain spatio‐temporal analyses that focus on how locations change over time, which require researchers to view each location from a temporal perspective. In this article, we present a data model to organize multi‐temporal remote sensing datasets and track their changes at the individual pixel level. This data model can also integrate raster datasets from heterogeneous sources under a unified framework. The proposed data model consists of several object classes under a hierarchical structure. Each object class is associated with specific properties and behaviors to facilitate efficient spatio‐temporal analyses. We apply this data model to a case study of analyzing the impact of the 2007 freeze in Knoxville, Tennessee. The characteristics of different vegetation clusters before, during, and after the 2007 freeze event are compared. Our findings indicate that the majority of the study area is impacted by this freeze event, and different vegetation types show different response patterns to this freeze. 相似文献
7.
基于完善的交通规划理论和模型,以某市为例,借助RS技术的空间数据获取能力和GIS技术的空间分析能力,综合考虑最短出行距离、最短出行时间以及网络节点人口密度3个因素,研究分析某市的道路交通可达性,并对现有的道路交通网络进行评价,为未来城市道路交通规划以及城市建设提供科学可靠的参考依据。 相似文献
8.
Much effort has been applied to the study of land use multi‐objective optimization. However, most of these studies have focused on the final land use scenarios in the projected year, without considering how to reach the final optimized land use scenario. To fill this gap, a spatio‐temporal land use multi‐objective optimization (STLU‐MOO) model is innovatively proposed in this research to determine possible spatial land use solutions over time. The STLU‐MOO is an extension of a genetic land use multi‐objective optimization model (LU‐MOO) in which the LU‐MOO is generally carried out in different years, and the solutions at year T will affect the solutions at year T + 1. We used the Wuhan agglomeration (WHA) as our case study area. The STLU‐MOO model was employed separately for the nine cities in the WHA, and social, economic, and environmental objectives have been considered. The success of the experiments in the case study demonstrated the value and novelty of our proposed STLU‐MOO model. In addition, the results also indicated that the objectives considered in the case study were in conflict. According to the results, the optimal land use plan in 2050 can be traced back to 2040, 2030, and 2020, providing a series of Pareto solutions over the years which can provide spatio‐temporal land use multi‐objective optimization solutions to support the land use planning process. 相似文献
9.
Yan Shi Min Deng Jianya Gong Chang‐Tien Lu Xuexi Yang Huimin Liu 《Transactions in GIS》2019,23(2):312-333
Spatio‐temporal clustering is a highly active research topic and a challenging issue in spatio‐temporal data mining. Many spatio‐temporal clustering methods have been designed for geo‐referenced time series. Under some special circumstances, such as monitoring traffic flow on roads, existing methods cannot handle the temporally dynamic and spatially heterogeneous correlations among road segments when detecting clusters. Therefore, this article develops a spatio‐temporal flow‐based approach to detect clusters in traffic networks. First, a spatio‐temporal flow process is modeled by combining network topology relations with real‐time traffic status. On this basis, spatio‐temporal neighborhoods are captured by considering traffic time‐series similarity in spatio‐temporal flows. Spatio‐temporal clusters are further formed by successive connection of spatio‐temporal neighbors. Experiments on traffic time series of central London's road network on both weekdays and weekends are performed to demonstrate the effectiveness and practicality of the proposed method. 相似文献
10.
以深圳市为研究区，在考虑距离衰减效应的重力型两步移动搜索法（gravity two-step floating catchment area method，G2SFCA）基础上，引入Huff模型，并考虑需求点位置要素及地形要素，分别从供给点竞争、需求点定位、路网距离优化三方面对G2SFCA进行改进，并采用改进的G2SFCA对深圳市室内应急避难场所空间可达性进行研究。实验结果表明，改进的G2SFCA不仅能很好地揭示深圳市各社区室内应急避难场所的空间可达性，而且也能有效反映避难场所可达性与人口密度分布的空间匹配规律，较其他模型更符合现实情况；已建成室内应急避难场所数量、容纳人口及空间可达性的统计与分析结果真实、可靠，相关结论可为深圳市未来的防灾工作以及室内应急避难场所的空间规划与建设提供参考。 相似文献
11.
Understanding the interplay between bus,metro, and cab ridership dynamics in Shenzhen,China 下载免费PDF全文
下载免费PDF全文 Mengxue Yue Chaogui Kang Clio Andris Kun Qin Yu Liu Qingxiang Meng 《Transactions in GIS》2018,22(3):855-871
The most common mass transit modes in metropolitan cities include buses, subways, and taxicabs, each of which contribute to an interconnected complex network that delivers urban dwellers to their destinations. Understanding the intertwined usages of these three transit modes at different places and time allows for better sensing of urban mobility and the built environment. In this article, we leverage a comprehensive data collection of bus, metro, and taxicab ridership from Shenzhen, China to unveil the spatio‐temporal interplay between different mass transit modes. To achieve this goal, we develop a novel spectral clustering framework that imposes spatio‐temporal similarities between mass transit mode usage in urban space and differentiates urban spaces associated with distinct ridership patterns of mass transit modes. Five resulting categories of urban spaces are identified and interpreted with auxiliary knowledge of the city's metro network and land‐use functionality. In general, different categorized urban spaces are associated with different accessibility levels (such as high‐, medium‐, and low‐ranked) and different urban functionalities (such as residential, commercial, leisure‐dominant, and home–work balanced). The results indicate that different mass transit modes cooperate or compete based on demographic and socioeconomic attributes of the underlying urban environments. Our proposed analytical framework provides a novel and effective way to explore the mass transit system and the functional heterogeneity in cities. It demonstrates great potential for assisting policymakers and municipal managers in optimizing public transportation facility allocation and city‐wide daily commuting distribution. 相似文献
12.
Emergency services personnel face risks and uncertainty as they respond to natural and anthropogenic events. Their primary goal is to minimize the loss of life and property, especially in neighborhoods with high population densities, where response time is of great importance. In recent years, mobile phones have become a primary communication device during emergencies. The portability of cell phones and ease of information storage and dissemination has enabled effective implementation of cell phones by first responders and one of the most viable means of communication with the population. Using cellular location data during evacuation planning and response also provides increased awareness to emergency personnel. This article introduces a multi‐objective, multi‐criteria approach to determining optimum evacuation routes in an urban setting. The first objective is to calculate evacuation routes for individual cell phone locations, minimizing the time it would take for a sample population to evacuate to designated safe zones based on both distance and congestion criteria. The second objective is to maximize coverage of individual cell phone locations, using the criteria of underlying geographic features, distance and congestion. In summary, this article presents a network‐based methodology for providing additional analytic support to emergency services personnel for evacuation planning. 相似文献
13.
MASTER: A multiple aspect view on trajectories 总被引：1，自引：0，他引：1
Ronaldo dos Santos Mello Vania Bogorny Luis Otavio Alvares Luiz Henrique Zambom Santana Carlos Andres Ferrero Angelo Augusto Frozza Geomar Andre Schreiner Chiara Renso 《Transactions in GIS》2019,23(4):805-822
For many years trajectory data have been treated as sequences of space‐time points or stops and moves. However, with the explosion of the Internet of Things and the flood of big data generated on the Internet, such as weather channels and social network interactions, which can be used to enrich mobility data, trajectories become more and more complex, with multiple and heterogeneous data dimensions. The main challenge is how to integrate all this information with trajectories. In this article we introduce a new concept of trajectory, called multiple aspect trajectory, propose a robust conceptual and logical data model that supports a vast range of applications, and, differently from state‐of‐the‐art methods, we propose a storage solution for efficient multiple aspect trajectory queries. The main strength of our data model is the combination of simplicity and expressive power to represent heterogeneous aspects, ranging from simple labels to complex objects. We evaluate the proposed model in a tourism scenario and compare its query performance against the state‐of‐the‐art spatio‐temporal database SECONDO extension for symbolic trajectories. 相似文献
14.
David S. Vale Fernando Ascensão Nuno Raposo António Pedro Figueiredo 《Journal of Geographical Systems》2017,19(1):43-64
It is well known that individual impairments create disparities in the accessibility of individuals to opportunities, lengthening the distances or time needed to reach them or even completely impeding access. However, the accurate calculation and representation of these disparities remain a major challenge for urban and transportation planners. In this paper, we adopt the concept of accessibility disparity, originally applied to measure place accessibility by different modes of transport, to measure and represent the accessibility of individuals with physical disabilities compared to those without disabilities. We use spatial network analysis to calculate spatial connectivity and the accessibility of Lisbon’s city center, revealing what we define as ‘disability-induced accessibility disparity’. Our results reveal not only the locations responsible for reduced accessibility, i.e., barriers and/or deterrents to movement, but also how much any given disparity reduces the accessibility of an individual, allowing the use of this methodology by planners to identify critical areas and to design inclusive public spaces. 相似文献
15.
Traffic congestion represents an ongoing serious issue in many large cities. Many public facilities, such as hospitals, tend to be centrally located to ensure they are most accessible to local residents; as a result, they may contribute significantly to a city's traffic congestion. In this study, a multi‐objective spatial optimization model was provided to help formulate hospital relocation plans, taking into account both traffic congestion and hospital accessibility. Using intra‐urban movement data, we proposed a method to estimate the area‐wide traffic congestion caused by hospital visits and to identify potential hospitals to be relocated. An NSGA‐II (Non‐dominated Sorting Genetic Algorithm II) algorithm was applied to solve the hospital relocation optimization problem; we applied our model to study optimal hospital relocation plans in Beijing. Analysis results provide a tradeoff between traffic congestion relief and hospital accessibility. We discussed plans that significantly reduce traffic congestion while maintaining a high level of hospital accessibility. Our study has significant policy implications and provides insights for future facility planning and transportation planning. 相似文献
16.
Abstract Conventional methods of deriving global or continental vegetation maps from the National Oceanic and Atmospheric Administration's (NOAA) Advanced Very High Resolution Radiometer (AVHRR) time series data are based on two‐value Boolean logic, which cannot properly model the so‐called ecotone, the transition zone between adjacent ecosystems. New methods and data models that have been developed on the basis of fuzzy logic to address the “mixed pixel” issue in multi‐spectral imagery can also be used with multi‐temporal imagery to handle the mixture of vegetation types within an ecotone. This study introduces the concept of semantic space and its transformation from spectral feature space, which utilizes a fuzzy logic approach to characterize the continuum of vegetation communities in the African continent from AVHRR multi‐temporal (12 months for three years from 1986 to 1988) NDVI data. The fuzzy procedure was based on the Fuzzy c‐Means (FCM) algorithm with significant modifications to improve processing speed for handling large volumes of data. A second‐order mapping approach was also devised to explicitly represent subdominant vegetative coverage in ecotones and other heterogeneous regions. Comparisons between a Sub‐Saharan African Vegetation Map compiled by the International Union for Conservation of Nature (IUCN) in 1986 and the maps derived from this study demonstrated that fuzzy modeling and classification might provide a better and more realistic representation of the vegetative characteristics of the region. 相似文献
17.
针对河南省高速公路建设对城市通达性影响问题,该文通过定义时间阈值,设计了基于人口加权时间距离倒数的通达性指数,在4个时间断面上,研究河南省高速交通网络中通达性时空特征及演化规律,时间距离倒数有效减小了多路径时间距离对分析结果的数字影响。结果表明,随着河南高速交通网络的拓展,城市通达性水平得到了显著的提升,空间收敛显著,边缘城市的提升始终高于中心区域城市;高速公路通车里程增长率与通达性水平的改善存在非协调现象;城市通达性的空间聚集现象震荡走弱,聚集区域减少;城市通达性空间分布变化规律和城市化人口变化规律逐渐趋于协调。 相似文献
18.
基于GIS的邯郸市医疗服务设施可达性分析 总被引：1，自引：0，他引：1
通过网络POI收集和地图截取手段获取邯郸市主城区范围内的居民点、医疗服务设施、路网数据,结合GIS的网络分析技术和改进的潜能模型对城市医疗服务设施可达性进行综合分析。结果表明,邯郸市的医疗设施资源分布主要集中在城市中心区、南部和东北部片区,在西南和北部城区医疗设施资源较少,且3种医疗设施可达性的分布差异较大。本文的结果对于医疗设施布局和规划具有重要的参考意义。 相似文献
19.
孟宏伟 《测绘与空间地理信息》2018,(1):182-184
通过对国土规划数据的多源性、异构型、多时空性、多尺度性以及不同坐标系等特点进行阐述和分析,制定技术路线,选用数据转换法和直接访问法等数据集成方法,基于ArcGIS软件二次开发技术建立广州市国土规划多源数据管理平台,对广州市白云区的9个城中村的基础调查数据进行了集成,从而在城市限高、文物保护、社会经济数据统计、人口数据统计等方面,为广州市城市更新管理提供数据服务。 相似文献
20.
This study demonstrated the cartographic implications of automated image processing and computer graphics for the study of time‐series data. Automated statistical and image processing techniques were applied to a case study data set consisting of weekly Crop Moisture Index (CMI) values summarized at 174 state cooperative weather stations within Oklahoma for the time period between February and October, 1980. Computer generated isoline maps of the CMI values were interpolated and rescaled into a series of 32 grid matrices for input into a raster‐based ERDAS image processing software system. Principal Components Analysis (PCA) was used to develop graphic models that synthesized the multi‐temporal data into statistical dimensions that represented the most significant elements of CMI variability. Graphic models of the PCA statistical vectors were displayed individually, in conjunction with eigenvector loadings, and as composite images. Resultant images were analyzed statistically and graphically through the generated CMI grid matrices to ascertain the location, severity, and progression of drought represented in the CMI values. Traditional image processing techniques and devices were combined with the ERDAS software system to transform the multi‐temporal CMI data into multi‐dimensional images that represented the drought's spatial and temporal signature unobscured by redundant information. 相似文献