共查询到20条相似文献，搜索用时 15 毫秒
1.
ABSTRACTIntersections are the critical parts where different traffic flows converge and change directions, forming “bottlenecks” and “clog points” in urban traffic. Intersection travel time is an important parameter for public route planning, traffic management, and engineering optimization. Based on low-frequency spatial-temporal Global Positioning System (GPS) trace data, this article presents a novel method for estimating intersection travel time. The proposed method first analyzes the different travel patterns of vehicles through an intersection, then determines the range of an intersection dynamically and reasonably, and obtains traffic flow speed and delay at the intersection under different travel patterns using a fuzzy fitting approach. Finally, the average intersection travel time is estimated from traffic flow speed and delay and intersection range in different travel patterns. Wuhan road network data and GPS trace data from taxicabs were tested in the experiments and the results show that the proposed method can improve the accuracy of travel time estimation at city intersections. 相似文献
2.
AbstractDetecting and describing movement of vehicles in established transportation infrastructures is an important task. It helps to predict periodical traffic patterns for optimizing traffic regulations and extending the functions of established transportation infrastructures. The detection of traffic patterns consists not only of analyses of arrangement patterns of multiple vehicle trajectories, but also of the inspection of the embedded geographical context. In this paper, we introduce a method for intersecting vehicle trajectories and extracting their intersection points for selected rush hours in urban environments. Those vehicle trajectory intersection points (TIP) are frequently visited locations within urban road networks and are subsequently formed into density-connected clusters, which are then represented as polygons. For representing temporal variations of the created polygons, we enrich these with vehicle trajectories of other times of the day and additional road network information. In a case study, we test our approach on massive taxi Floating Car Data (FCD) from Shanghai and road network data from the OpenStreetMap (OSM) project. The first test results show strong correlations with periodical traffic events in Shanghai. Based on these results, we reason out the usefulness of polygons representing frequently visited locations for analyses in urban planning and traffic engineering. 相似文献
3.
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
4.
Evaluating the importance of accessibility to congestion response using a GIS-based travel simulator
Irene Casas 《Journal of Geographical Systems》2003,5(1):109-127
This paper examines the effect of accessibility on individual response to unexpected traffic delays and congestion. The dataset
used was collected by means of a travel simulator developed within a geographic information system (GIS) environment. The
simulator models a commute trip where congestion takes place, and subjects are asked to respond by making a choice among alternative
courses of action. Available alternatives for dealing with the unexpected traffic delay include changing the location of the
planned activities or changing the activities to be performed. Accessibility to the new locations and to the different activities
is computed using a cumulative measure. Analysis using CHAID tree technique found that accessibility is a good predictor of
subjects' choice when responding to unexpected traffic delays.
Received: September 2002 / Accepted: January 2003
Support for this research by a grant from the Center of Intelligent Transportation Research of the Ohio State University
is gratefully acknowledged. The author would also like to thank Joe Weber, Mei-Po Kwan and two anonymous reviewers for their
valuable comments. 相似文献
5.
《测量评论》2013,45(92):276-277
AbstractIn survey work connected with Seismic (Geophysical) investigations, the nature of the operations is such that provisional points many miles apart have frequently to be located with a minimum of delay. When no map and no triangulation exists, the range finding method about to be described is very useful. The method can also be recomlnended for reconnaissance and exploration surveys. It was used by one of the R.A. Survey Regiments with success during the war. The essentials are a good theodolite and a steel tape. 相似文献
6.
A relativistic delay model for Earth-based very long baseline interferometry (VLBI) observation of sources at finite distances is derived. The model directly provides the VLBI delay in the scale of terrestrial time. The effect of the curved wave front is represented by using a pseudo source vector K = (R
1 + R
2)/(R
1 + R
2), and the variation of the baseline vector due to the difference of arrival time is taken into account up to the second-order by using Halley’s method. The precision of the new VLBI delay model is 1 ps for all radio sources above 100 km altitude from the Earth’s surface in Earth-based VLBI observation. Simple correction terms (parallax effect) are obtained, which can also adopt the consensus model (e.g. International Earth Rotation and Reference Frames Service conventions) to finite-distance radio source at R > 10 pc with the same precision. The new model may enable estimation of distance to the radio source directly with VLBI delay data. 相似文献
7.
In recent decades, rapid growth of travel volume has resulted in a significant increase in traffic congestion, accidents, environmental pollution and energy consumption. Accurate traffic data are drastically needed for effective evaluation of traffic systems in order to alleviate the impacts of increasing travel volume of the quality of life and economic development of urban areas. This article provides a discussion on a data acquisition methodology for highway traffic pattern recognition and congestion analysis by integrating data from the global positioning system (GPS) with a geographic information system (GIS). The GPS technology is a powerful tool in capturing continuous positioning and timing information, whereas the GIS is capable of storing, managing, manipulating, analyzing and displaying the acquired spatial information. Compared to previous studies, the effective integration of the two technologies allows for traffic analysis to be conducted at a finer resolution. The proposed method is illustrated with a case study on multiple major highway segments in Columbus, Ohio. 相似文献
8.
AbstractScatterplots are essential tools for data exploration. However, this tool poorly scales with data-size, with overplotting and excessive delay being the main problems. Generalization methods in the attribute domain focus on visual manipulations, but do not take into account the inherent nature of information redundancy in most geographic data. These methods may also result in alterations of statistical properties of data. Recent developments in spatial statistics, particularly the formulation of effective sample size and the fast approximation of the eigenvalues of a spatial weights matrix, make it possible to assess the information content of a georeferenced data-set, which can serve as the basis for resampling such data. Experiments with both simulated data and actual remotely sensed data show that an equivalent scatterplot consisting of point clouds and fitted lines can be produced from a small subset extracted from a parent georeferenced data-set through spatial resampling. The spatially simplified data subset also maintains key statistical properties as well as the geographic coverage of the original data. 相似文献
9.
本文以北京城市交通为例,选取北京城市路网数据,计算城市路网介数中心性,以反映城市各道路路段的通达情况;并利用北京出租车GPS定点数据,计算实际的交通轨迹。传统的路网介数中心性主要依据各路段最短路径的比重评价理论上的道路通达性,而本文以网络介数中心性为基础,提出动态介数的方法,从城市各路段交通量比重的角度评价各道路实际拥堵情况。利用两个介数的对比能够全面客观地反映交通拥堵状况,提高交通拥堵指数的参考价值,并为城市建设规划决策及道路改建等方案提供依据,有利于缓解城市道路交通拥堵现状。 相似文献
10.
《International Journal of Digital Earth》2013,6(12):1214-1230
ABSTRACTEarth observation data are typically compressed using general-purpose single-threaded compression algorithms that operate at a fraction of the bandwidth of modern storage and processing systems. We present evidence that recently developed multi-threaded compression codecs offer substantial benefits over widely used single-threaded codecs in terms of compression efficiency when applied to a selection of moderate resolution imaging spectroradiometer (MODIS) datasets stored in the HDF5 format. Compression codecs from the LZ77 and Rice families are shown to vary in efficacy when applied to different MODIS data products, highlighting the need for compression strategies to be tailored to different classes of data. We also introduce LPC-Rice, a new multi-threaded codec, that performs particularly well when applied to time-series data. 相似文献
11.
Integrated Traffic Management Systems (ITMS) need reliable, accurate, and real-time data. Travel time, speed, and delay are
three of the most important factors used in ITMS for monitoring, quantifying, and controlling congestion. GPS has recently
become available for civil applications. Because it provides real-time spatial and time measurements, it has an increasing
use in conducting different transportation studies. This article presents the application of GPS in collecting travel time,
speed, and delay information of 64 major roads in the state of Delaware. A comparative statistical analysis was performed
on data collected by GPS, with data collected simultaneously by the conventional method. The GPS data proved to be at least
as accurate as the data collected by the conventional method, and it was 50% more efficient in terms of manpower. Moreover,
the sample-size requirement was determined to maintain 95% confidence level throughout the controlled test. Benefiting from
the Geographic Information System's dynamic segmentation tool, our travel time, delay, and speed information were integrated
with other relevant traffic data. This was presented graphically on the Internet for public use. Statistical trend analysis
for the data collected in 1997, 1998, 1999, and 2000 are also presented and applications on the overall ITMS are discussed.
? 2002 Wiley Periodicals, Inc. 相似文献
12.
13.
《International Journal of Digital Earth》2013,6(1):47-71
Abstract Vectors and periodic phenomena, e.g. traffic versus time, have direction on a circular scale of 360°. An overview of existing methods for the display of circular-spatial and vectorial-spatial data, such as arrow plots, is given. We introduce the circular dataimage, a new type of graphic for the display of circular-spatial data. It is defined by encoding direction in a spatial display by using colors from a color wheel constructed by connecting three or more two-color gradients with color continuity at the connections. Therefore, image discontinuity from using a single-color gradient, e.g. blue–red, does not occur. High-resolution global views of ocean wind direction are used as a running example throughout the paper. Advantages and disadvantages of circular dataimages compared to arrow plots were obtained from a usability study. Circular dataimages provide for simultaneous recognition of fine structure on a small-scale and large-scale structure on a global scale. 相似文献
14.
交通拥堵是当代各大城市普遍面临的问题,如何通过各种技术手段发现城市交通的易拥堵路段并予以改善是城市交通相关部门以及学者关心的一个问题。通过各种GPS设备产生的历史轨迹数据对城市的研究逐渐受到重视,且取得一定的进展。文中总结运行车辆的4种通行状态:正常行驶、停靠/停泊、信号灯等待以及拥堵,分析这4种状态下运行车辆的速度特征,定义轨迹段平均速度和轨迹段速度方差两个数字特征用来描述运行车辆轨迹段的速度特征以及描述路段拥堵程度的拥堵指数,提出一种基于轨迹分段的拥堵检测的可视化方法,通过实验验证发现其可以较好地估计城市交通拥堵状况。 相似文献
15.
ABSTRACTUsing Artl@s as an example of a project that relies on volunteered geographic information (VGI), this article examines the specific challenges that exist, beyond those frequently discussed in general VGI systems (e.g., participants’ motivation and data quality control) in regard to sharing research data in humanities: (1) most data from the humanities is qualitative and collected from multiple data sources which are often inconsistent and unmappable; (2) data is usually interconnected with multiple relationships among different tables which creates challenges for both mapping and query functionality; (3) data is both geographical and historical. Consequently addresses that no longer exist have to be geolocated and visualized on historical basemaps and spaces must be represented diachronically; (4) the design of web map application needs to balance both sophisticated research requirements and a user-friendly interface; (5) finally contributors expect their data to be cited or acknowledged when used in other studies and users need metadata and citation information in order to reuse and repurpose datasets.In this article, we discuss how Artl@s, a project which developed a georeferenced historical database of exhibition catalogues, addresses these challenges. Artl@s provides a case study for VGI adoption by digital humanities scholars for research data sharing, as it offers features, such as flexible batch data contribution, interrelated spatial query, automatic geolocalization of historical addresses, and data citation mechanisms. 相似文献
16.
Pluvial flash flood (PFF) can cause serious traffic disruption in big cities. We conducted interdisciplinary research by integrating flood modeling and traffic analysis to reveal the spatiotemporal pattern of the interplay between these two processes. A simplified simulation tool, which is capable of building a road network model, assigning trip paths with the effect of road closures, and evaluating travel delay and vehicle volume redistribution in a given PFF scenario, was developed to capture the traffic disruption in the face of PFF events. Modeling outputs from a case study in the city center of Shanghai showed that the delay of vehicles diverted to dry links or trapped in flooded links may reach 0.5 to 8 times the travel time in no‐flood scenarios. Overall, approximately 1–7% of vehicle volumes on flooded links would be redistributed onto dry links (more likely major arterial roads). However, the vehicle volume variation during each time interval demonstrated evident disparity with the spatiotemporal change of flood inundations. Simulating and mapping the congestion can largely facilitate the identification of vulnerable links. Future research will test the method in other intra‐urban areas and try to bridge the gap between modeling outputs and smart city planning and management. 相似文献
17.
AbstractThe constant K in equation (12) represents distance expended through time lags in the instrument itself, and, although the value of K can be calculated from electrical data, this would not be very satisfactory and it would be better to determine it directly by means of observations over a line of known length. In addition, the point from which K would be reckoned is not a convenient one for actual field measurements. Instead of this, it is more convenient to choose an index mark on the instrument itself and referall measurements to this and thence to the mark over which the instrument is set up. 相似文献
18.
目前,基于GPS轨迹探测城市交通状态的研究缺乏对不同行驶方向的交通拥堵精细感知。针对此问题,本文提出一种基于出租车GPS轨迹的转向级交通拥堵事件探测方法。该方法首先在分析出租车运营行为特征的基础上,采用特征聚类方法滤选出能够反映真实交通状态的有效轨迹段;然后基于滤选后轨迹分析当前道路交通运行状态,探测城市路网中轻度、中度、重度3种不同强度的交通拥堵事件;最后基于拥堵事件轨迹分析交叉口不同转向的拥堵时间、拥堵强度和拥堵距离等转向级精细交通拥堵状态。试验结果表明,本文方法不仅能有效探测路网中不同强度的拥堵事件,而且能实现交叉口转向级拥堵事件的精细分析。 相似文献
19.
Russell D. Johnson 《国际地球制图》2013,28(1):41-45
Abstract Remote sensing is a powerful and accurate means of collecting data for wildlife management, particularly for large areas which are difficult of access and feature delicate ecosystems. Giant panda habitat in the People's Republic of China was evaluated by visual interpretation of multitemporal LANDSAT MSS images. The resulting map, combined with ground survey data, provides important information upon which management decisions can be planned. This case study illustrates that remote sensing techniques can make a significant contribution to the management programme for the conservation of a threatened animal species. 相似文献
20.
《The Cartographic journal》2013,50(1):19-32
AbstractMaps which are created on demand by combining geospatial data from different Web Map Services integrate conflicting portrayals and do not satisfy the requirements of effective cartographic communication. A significant improvement is achieved by selecting clearly distinguishable colours which are determined by solving an optimisation problem. Cartographic guidelines and user characteristics (e.g. colour vision impairment) can be incorporated into the optimisation model as constraints which guide the selection of colours. 相似文献