基于FCD数据的城市有效路网密度评价——以广州荔湾区和越秀区为例

提出一种基于FCD数据的城市有效路网密度的评价方法,主要是从城市路网的静态布局结构和动态交通流量两个方面对城市路网数据以及FCD数据进行核密度估计分析,得到城市有效路网密度等级的分布特征,继而通过理论与实际道路网密度等级差异对比分析,发现路网中差异区域,为城市路网规划提供可靠的依据。以广州市中心城区越秀、荔湾内的主要路网数据以及2010年五一期间中心城区内出租车的FCD数据为例,利用上述评价方法进行分析得出以下结论:区域内人民中路、人民南路、白云路、中山六路和中山七路路段的理论与实际密度等级差异性明显,表现为路段上密度核的数量与核影响范围差异大,其中尤为突出的是人民中路和人民南路,从理论有效路网密度的分析角度,两个路段都是高密度区域,与实际交通流量存在较大的密度分异。     

Geometric-based approach for integrating VGI POIs and road networks

Integrating heterogeneous spatial data is a crucial problem for geographical information systems (GIS) applications. Previous studies mainly focus on the matching of heterogeneous road networks or heterogeneous polygonal data sets. Few literatures attempt to approach the problem of integrating the point of interest (POI) from volunteered geographic information (VGI) and professional road networks from official mapping agencies. Hence, the article proposes an approach for integrating VGI POIs and professional road networks. The proposed method first generates a POI connectivity graph by mining the linear cluster patterns from POIs. Secondly, the matching nodes between the POI connectivity graph and the associated road network are fulfilled by probabilistic relaxation and refined by a vector median filtering (VMF). Finally, POIs are aligned to the road network by an affine transformation according to the matching nodes. Experiments demonstrate that the proposed method integrates both the POIs from VGI and the POIs from official mapping agencies with the associated road networks effectively and validly, providing a promising solution for enriching professional road networks by integrating VGI POIs.     

Empirical determination of geometric parameters for selective omission in a road network

Selective omission in a road network is a necessary operation for road network generalization. Most existing selective omission approaches involve one or two geometric parameters at a specific scale to determine which roads should be retained or eliminated. This study proposes an approach for determining the empirical threshold for such a parameter. The idea of the proposed approach is to first subdivide a large road network, and then to use appropriate threshold(s) obtained from one or several subdivisions to infer an appropriate threshold for the large one. A series of experiments was carried out to validate the proposed approach. Specifically, the road network data for New Zealand and Hong Kong at different scales (ranging from 1:50,000 to 1:250,000) were used as the experimental data, and subdivided according to different modes (i.e. administrative boundary data, a regular grid of different sizes, different update years, and different road network patterns). Not only geometric parameters, but also structural and hybrid parameters of existing selective omission approaches were involved in the testing. The experimental results show that although the most appropriate thresholds obtained from different subdivisions are not always the same, in most cases, the appropriate threshold ranges often overlap, especially for geometric parameters, and they also overlap with those obtained from the large road network data. This finding is consistent with the use of different subdivision modes, which verifies the effectiveness of the proposed approach. Several issues involving the use of the proposed approach are also addressed.     

广州城市道路网的社会分异——基于轨迹大数据的出行分布性别差异

社会空间分异是人文地理学研究的重要议题,以往研究主要聚焦基于居住地和活动地的分异现象,缺乏对道路网社会空间分异的关注。本文以广州市中心区域为例,结合日常活动空间理论和空间分析方法,基于手机轨迹大数据,研究不同性别群体日常出行的城市道路网社会空间分异现象及其影响因素。结果显示：基于性别差异的城市道路网社会隔离指数高于居住地、低于就业地,在14:00—15:00时段达到峰值;不同性别群体在路网中的分布总体呈现不均衡的集聚特点,其中女性集聚程度更高;不同性别群体的出行分布和分异受到路网周边建成环境因素的影响;物流运输业就业密度的提高、小学数量的增多或道路等级的提高都会显著提高男性相对出行量,而社会服务业就业密度的提高、菜市场数量或公交站点数量的增多以及到市中心距离的减少都会显著提高女性相对出行量,这些与个体家庭和职业分工的性别差异有一定的关系。本文通过理论假设和实证分析,验证了家庭和职业的分工决策是影响道路网出行分布性别分异的深层次原因,也是解释社会空间分异的重要理论视角。研究结果有助于认识和挖掘基于城市道路网的社会分异现象及其影响机制,并为完善道路网络及周围设施的布局与建设提供借鉴。     

深圳市道路网络结构特征的成因及其景观格局效应

本文以我国典型快速城市化地区深圳市为例,综合使用GIS技术、道路网络结构特征分析、景观格局分析和相关分析方法研究其道路网络结构特征的成因及其景观生态效应。在确定了24个独立的空间研究单元的基础上,重点分析了深圳市道路网络结构特征的相关关系、城市化水平差异对道路网络结构特征的影响和道路格局特征的景观整体及重要组分的格局效应。结果表明:城市建设用地密度的增加导致交通用地密度、节点和廊道储量增加,道路网络结构复杂程度、格局指数降低;资源条件、环境和生态保护约束是导致道路网络复杂性增加、结构发育水平下降、网络格局指数不断降低的主要原因;深圳市的道路网络格局特征对全市景观整体格局没有表现显著的约束性影响,对建设用地显示出环境保护约束和空间吸引两个方面的综合效应,对于林地则表现出生态保护约束、空间排斥和物理分割三个方面的综合效应。     

Hierarchical community detection and functional area identification with OSM roads and complex graph theory

An in-depth analysis of the urban road network structure plays an essential role in understanding the distribution of urban functional area. To concentrate topologically densely connected road segments, communities of urban roads provide a new perspective to study the structure of the network. In this study, based on OpenStreetMap (OSM) roads and points-of-interest (POI) data, we employ the Infomap community detection algorithm to identify the hierarchical community in city roads and explore the shaping role roads play in urban space and their relation with the distribution of urban functional areas. The results demonstrate that the distribution of communities at different levels in Guangzhou, China reflects the urban spatial relation between the suburbs and urban centers and within urban centers. Moreover, the study explored the functional area characteristics at the community scale and identified the distribution of various functional areas. Owing to the structure information contained in the identification process, the detected community can be used as a basic unit in other urban studies. In general, with the community-based network, this study proposes a novel method of combining city roads with urban space and functional zones, providing necessary data support and academic guidance for government and urban planners.     

Integration of linear and areal hierarchies for continuous multi-scale representation of road networks

Spatial data can be represented at different scales, and this leads to the issue of multi-scale spatial representation. Multi-scale spatial representation has been widely applied to online mapping products (e.g., Google Maps and Yahoo Maps). However, in most current products, multi-scale representation can only be achieved through a series of maps at fixed scales, resulting in a discontinuity (i.e., with jumps) in the transformation between scales and a mismatch between the available scales and users' desired scales. Therefore, it is very desirable to achieve smoothly continuous multi-scale spatial representations. This article describes an integrated approach to build a hierarchical structure of a road network for continuous multi-scale representation purposes, especially continuous selective omission of roads in a network. In this hierarchical structure, the linear and areal hierarchies are constructed, respectively, using two existing approaches for the linear and areal patterns in a road network. Continuous multi-scale representation of a road network can be achieved by searching in these hierarchies. This approach is validated by applying it to two study areas, and the results are evaluated by both quantitative analysis with two measures (i.e., similarity and average connectivity) and visual inspection. Experimental results show that this integrated approach performs better than existing approaches, especially in terms of preservation of connectivity and patterns of a road network. With this approach, efficient and continuous multi-scale selective omission of road networks becomes feasible.     

面向指路标志系统的交通网络数据模型及应用

指路标志指示的信息与路网的拓扑数据、几何特征和交通网络的服务规则紧密相关。在传统的弧段—结点数据模型基础上拓展了结点—邻近结点拓扑关系,加入与交叉口相关的路网几何特征和交通网络服务规则,建立面向指路标志系统的交通网络数据模型。将这种数据模型应用于广州市城市路网的指路标志系统中,实现了城市路网指路标志的自动生成。     

Using kernel density estimation to assess the spatial pattern of road density and its impact on landscape fragmentation

Road density (i.e., km/km²) is a useful broad index of the road network in a landscape and has been linked to several ecological effects of roads. However, previous studies have shown that road density, estimated by grid computing, has weak correlation with landscape fragmentation. In this article, we propose a new measure of road density, namely, kernel density estimation function (KDE) and quantify the relation between road density and landscape fragmentation. The results show that road density estimated by KDE (km/km²) elucidates the spatial pattern of the road network in the region. Areas with higher road density are dominated by a larger proportion of built-up landscape and less possession of forest and vice versa. Road networks segregated the landscape into smaller pieces and a greater number of patches. Furthermore, Spearman rank correlation model indicates that road density (km/km²) is positively related to landscape fragmentation. Our results suggest that road density, estimated by KDE, may be a better correlate with effects of the road on landscape fragmentation. Through KDE, the regional spatial pattern of road density and the prediction of the impact of the road on landscape fragmentation could be effectively acquired.     

Sediment concentration changes in runoff pathways from a forest road network and the resultant spatial pattern of catchment connectivity

Hydrological connectivity is a term often used to describe the internal linkages between runoff and sediment generation in upper parts of catchments and the receiving waters. In this paper, we identify two types of connectivity: direct connectivity via new channels or gullies, and diffuse connectivity as surface runoff reaches the stream network via overland flow pathways. Using a forest road network as an example of a landscape element with a high runoff source strength, we demonstrate the spatial distribution of these two types of linkages in a 57 km² catchment in southeastern Australia. Field surveys and empirical modelling indicate that direct connectivity occurs primarily due to gully development at road culverts, where the average sediment transport distance is 89 m below the road outlet. The majority of road outlets were characterised by dispersive flow pathways where the maximum potential sediment transport distance is measured as the available hillslope length below the road outlet. This length has a mean value of 120 m for this catchment. Reductions in sediment concentration in runoff plumes from both pathways are modelled using an exponential decay function and data derived from large rainfall simulator experiments in the catchment. The concept of the volume to breakthrough is used to model the potential delivery of runoff from dispersive pathways. Of the surveyed road drains (n=218), only 11 are predicted to deliver runoff to a stream and the greatest contributor of runoff occurs at a stream crossing where a road segment discharges directly into the stream. The methodology described here can be used to assess the spatial distribution and likely impact of dispersive and gullied pathways on in-stream water quality.     

基于交通信息流的长三角地区网络空间结构及其效率研究

基于2015年长三角地区25个地级市之间的公路、普速列车、高速列车与信息网络数据,对流视角下该地区的网络结构特征及其效率进行综合分析与判断。研究表明：① 流视角下长三角地区网络结构呈现出“Z”字型向“一轴多极”的网络空间结构转变、网络中核心与边缘城市节点价值的此消彼长和“等级+网络”等新特征;② 现代化的交通与通信技术变革加速了高端生产与管理要素在区域的集聚与扩散,促使长三角地区呈现出明显的“核心—边缘”格局;③ 长三角地区网络化的综合效率一般,仅有少部分城市达到了最优,但各城市的规模效率相对较好,是未来综合效率提高的主要影响因素。     

外部性视角下中国城市网络演化及其环境效应研究

在全球化、快速城市化和新技术革命的背景下,要素流与网络关系构成的“流空间”愈发重要,城市网络结构不断受到冲击与重塑,人地关系矛盾日益凸显,区域空间组织模式及其环境效应已成为环境经济地理学研究的重要议题。本文利用腾讯位置大数据,构建了2015—2018年288个地级以上城市之间的人口迁徙网络,采用社会网络分析和面板空间计量模型,对中国城市网络演化格局及其环境效应进行实证分析。结论如下：① 中国城市网络联系强度高的城市主要分布在“胡焕庸线”东侧的京津冀、长三角、珠三角和成渝城市群组成的菱形结构;城市网络密度和关联性逐渐增强,度数和中介中心性呈现多中心和分散化的发展趋势。② 中国城市空气质量总体有所好转,空间上呈现显著的集聚特征;88.89%的城市空气质量指数（AQI）下降,PM_2.5、PM₁₀、SO₂、CO和NO₂年均浓度有所下降,而O₃年均浓度有所上升。③ 中国城市网络对环境质量的影响主要来源于城市网络外部性所带来的空间溢出效应;城市网络中节点权力地位和影响力的增强,提高了借用规模和借用技术,从而促进环境质量提升。④ 度数中心性提升了东部、中部和东北地区的环境质量,减少了PM_2.5、PM₁₀、SO₂和O₃的年均浓度,增加了CO的年均浓度;而中介中心性则提高了西部地区的环境质量,降低了NO₂的年均浓度。     

基于浮动车数据的旅游景点周边路网容量研究——以厦门岛为例

随着旅游业的快速发展,旅游城市在法定节假日出现了交通需求的大幅增长,导致不同程度的交通问题。本文利用厦门市的浮动车数据(FCD),分别选取2014年10月1日与10月14日作为节假日与工作日的样本进行研究,首先通过OD点核密度估计判断节假日与工作日出行在时空上的差异,确定研究的时空范围;其次,通过对FCD数据进行核密度估计分析旅游景点周边的车流量变化,并与路段的等级、车道数等道路设施属性进行对比,推测路网的容量;最后进一步通过计算路网中路段行程车速验证方法的可行性。结果显示：节假日期间的旅游交通与工作日的通勤交通在时空分布上存在差异,同时基于FCD数据研究旅游景点周边的路网容量是有效的,厦大—南普陀景点周边路网在节假日期间无法满足车流量的需求。本文对旅游景点周边路网容量的评估结果可为旅游旺季旅游路网的合理规划与管控提供依据。     

基于SNA的全球电子信息制造业贸易网络演化特征及机理研究

基于ITC公布的2001、2007、2013年和2018年贸易数据,构建全球电子信息制造业贸易网络,采用社会网络分析法研究全球电子信息制造业贸易网络的演化特征及影响因素。结果表明：（1）电子信息制造业贸易总量增幅较大但增速放缓,贸易地区高度集中且贸易重心向发展中经济体偏移,但未出现明显“多极化”趋势;网络成员间联系渐趋紧密,中心性位居前列的成员基本稳定但整体地位下降;子群内部成员变动较大,尚未出现明显的派系林立现象;网络存在核心-半边缘-边缘结构,核心区与半边缘区内发达经济体地位下降,东亚与东南亚部分经济体的地位上升;中国大陆在网络中已占据重要位置,但中心性仍有较大提升空间,且尚未形成稳定的“朋友圈”。（2）经济规模差异、技术差异、文化差异、劳动力数量差异、陆地接壤对电子信息制造业贸易网络具有较大程度的正向影响,地理距离与物流绩效差异显示较小程度的显著负向影响,需求差异近年来具有较小程度的显著正向影响,制度差异未产生明显的影响。研究结果显示要素禀赋理论与技术差距理论对全球电子信息制造业贸易网络特征有较好的解释力,需求相似理论的解释力比较有限,全球电子信息制造业贸易兼具产业内与产业间的贸易特性。     

基于手机信令数据的南京市旅游客源地网络层级结构及区域分异研究

游客源地和目的地之间构成了一张动态的空间网络,流空间视角下的客源网络研究有助于更为真实地反映客流空间结构和客源地区位结构特征。以南京市51个景区的监测客源大数据为例,分别选取元旦、清明节、劳动节、端午节和中秋节5个时段的游客数据,采用社会空间网络聚类分析方法和空间区域划分模型,从地级市层面展开客源地网络层次结构和区域分异模式分析。结果表明：① 地市层面的客流强度表现出显著的空间层次结构特征,高等级节点主要位于南京的最邻近区域和次邻近区域,外生网络效应明显;② 不同小长假客源网络节点在全局上呈现相似的层次结构和分布模式,局部区域差异显著;③ 区域化的客源流量表现为南北分异模式,而区域化的客流强度则呈现东西分异模式。     

Using a Bayesian estimator to combine information from a cluster analysis and remote sensing data to estimate high-resolution data for agricultural production in Germany

In Germany, a county-resolution data set that consists of 35 land-use and animal-stock categories has been used extensively to assess the impact of agriculture on the environment. However, because such environmental effects as emission or nutrient surplus depend on the location, even a county resolution might produce misleading results. The aim of this article is to propose a Bayesian approach which combines two sorts of information, with one being treated as defining the prior and the other the data to form a posterior, used to estimate a data set at a municipality resolution. We define the joint prior density function based on (i) remote sensing data, thus accounting for differences in county data and missing data at the municipality level, and (ii) the results of a cluster analysis that was previously applied to the micro-census, whereas the data are defined by official statistics at the county level. This approach results in a fairly accurate data set at the municipality level. The results, using the proposed method, are validated by the national research data centre by comparing the estimates to actual observations. The test statistics presented here demonstrate that the proposed approach adequately estimates the production activities.     

可服务于北极航道的海冰与气象预报信息综合分析

全球气候变暖和北极海冰快速减少背景下,北极航道正在开通,提高海冰和气象预报能力是北极地区船只航行的重要保障。通过获取不同国家的北极高纬共享信息(包括观测数据、预报产品和历史分析资料),分析国际北极地区海冰和气象预报信息特点及存在的问题,能够为我国北极观测预报的常态化、业务化发展提供参考。通过对7个环北极国家、3个非北极国家以及3个信息发布平台共23家机构海冰和气象预报信息的对比,发现近年来各国北极预报水平提升,合作交流扩大,但是仍存在一些问题,如观测数据没有充分应用于预报、北极中央区的预报能力偏弱、预报信息共享度不够、信息应用时需要加以选择、仍需提升信息发布技术。通过上述分析,建议我国持续增加北极科考、国际合作、冰区安全航行预报保障技术研究等的投入,以系统提升我国的极地预报能力,为我国北极科考和极地航运事业提供更加及时有效的预报保障。     

A regionalization method for clustering and partitioning based on trajectories from NLP perspective

ABSTRACT

Regionalization attempts to group units into a few subsets to partition the entire area. The results represent the underlying spatial structure and facilitate decision-making. Massive amounts of trajectories produced in the urban space provide a new opportunity for regionalization from human mobility. This paper proposes and applies a novel regionalization method to cluster similar areal units and visualize the spatial structure by considering all trajectories in an area into a word embedding model. In this model, nodes in a trajectory are regarded as words in a sentence, and nodes can be clustered in the feature space. The result depicts the underlying socio-economic structure at multiple spatial scales. To our knowledge, this is the first regionalization method from trajectories with natural language processing technology. A case study of mobile phone trajectory data in Beijing is used to validate our method, and then we evaluate its performance by predicting the next location of an individual’s trajectory. The case study indicates that the method is fast, flexible and scalable to large trajectory datasets, and moreover, represents the structure of trajectory more effectively.