Anchor uncertainty and space-time prisms on road networks

Space-time prisms capture all possible locations of a moving person or object between two known locations and times given the maximum travel velocities in the environment. These known locations or ‘anchor points’ can represent observed locations or mandatory locations because of scheduling constraints. The classic space-time prism as well as more recent analytical and computational versions in planar space and networks assume that these anchor points are perfectly known or fixed. In reality, observations of anchor points can have error, or the scheduling constraints may have some degree of pliability. This article generalizes the concept of anchor points to anchor regions: these are bounded, possibly disconnected, subsets of space-time containing all possible locations for the anchor points, with each location labelled with an anchor probability. We develop two algorithms for calculating network-based space-time prisms based on these probabilistic anchor regions. The first algorithm calculates the envelope of all space-time prisms having an anchor point within a particular anchor region. The second algorithm calculates, for any space-time point, the probability that a space-time prism with given anchor regions contains that particular point. Both algorithms are implemented in Mathematica to visualize travel possibilities in case the anchor points of a space-time prism are uncertain. We also discuss the complexity of the procedures, their use in analysing uncertainty or flexibility in network-based prisms and future research directions.     

Simulating visit probability distributions within planar space-time prisms

The space-time prism is key concept in time geography and moving objects databases; it demarcates all locations that a mobile object can occupy given anchor locations and times and a maximum velocity for travel. Although the prism’s spatial and temporal extent is widely applied as a measure of accessibility and object locational uncertainty, until recently little attention has been paid to the properties of the prism interior such as the probabilities of the object visiting different locations within the prism. Better understanding of the visit probability distribution within the prism can improve theoretical understanding as well as refine the prism as a practical measure of space-time accessibility and object uncertainty. This paper presents two methods for modeling the distribution of visit probabilities within planar space-time prisms: (1) a directed Random Walk method for discrete space and time, and (2) a truncated Brownian Bridges method for continuous space and time. We illustrate these methods and demonstrate the effect of prism and mobility parameters on the visit probability distributions within the prism.     

Modeling uncertainty of moving objects on road networks via space–time prisms

Moving objects produce trajectories, which are typically observed in a finite sample of time‐stamped locations. Between sample points, we are uncertain about the moving objects's location. When we assume extra information about an object, for instance, a (possibly location‐dependent) speed limit, we can use space–time prisms to model the uncertainty of an object's location.

Until now, space–time prisms have been studied for unconstrained movement in the 2D plane. In this paper, we study space–time prisms for objects that are constrained to travel on a road network. Movement on a road network can be viewed as essentially one‐dimensional. We describe the geometry of a space–time prism on a road network and give an algorithm to compute and visualize space–time prisms. For experiments and illustration, we have implemented this algorithm in MATHEMATICA.

Furthermore, we study the alibi query, which asks whether two moving objects could have possibly met or not. This comes down to deciding if the chains of space–time prisms produced by these moving objects intersect. We give an efficient algorithm to answer the alibi query for moving objects on a road network. This algorithm also determines where and when two moving objects may have met.     

SPACE‐TIME MODELING OF GRIZZLY BEARS*

ABSTRACT. An appropriate conceptual leap can be made from human geography to physical geography by applying space‐time continuum modeling to zoogeomorphology—the alteration of the landscape by animals. Drawing on the work of Torsten Hägerstrand, we propose a space‐time continuum model of grizzly bears, a geomorphic agent. Through both data‐driven and conceptual applications, the model traces where and when grizzly bears are likely to wield a geomorphic impact. The model further demonstrates that geographers have much to gain by merging concepts from human and physical geography.     

Random encounters in probabilistic time geography

Probabilistic time geography considers the encounter of moving agents to be random; therefore, a quantitative time geography analysis must consider the actual encounter probability. The existing algorithm of encounter probability is oriented over a discrete space and is sensitive to the unit definition of a virtual grid; thus, it is not suitable for continuous space. For this reason, a new method is presented in this paper for the encounter of two moving agents in continuous space. When the encounters are less than a specified distance threshold apart, an encounter event occurs based on the probability of the product, which is calculated by their respective probability density functions over their respective potential location areas. This probability provides a quantitative basis for predicting the likelihood of two agents meeting, as well as the location of this meeting point. Finally, the validity of the proposed model is verified by an experiment, which uses tracking data to calculate the encounter probabilities of three zebras and analyse the distribution characteristics of these probabilities over time and space.     

A GIS toolkit for measuring and mapping space–time accessibility from a place-based perspective

This article introduces a novel geographical information system toolkit for measuring and mapping the accessibility of individuals to services. The toolkit contributes to earlier implementations by combining aspects of both place-based and person-based accessibility measures. To this end, place-based accessibility measures are derived from a person-based framework by considering space–time prisms that are centred at service facilities rather than individual anchor points. The implementation is also innovative by explicitly accounting for the opening hours of service delivery in its accessibility measurement. In addition, the toolkit is aimed to be user-friendly and to generate insightful and comprehensible results for non-technically oriented users, which is illustrated in a brief case study about library accessibility in Ghent (Belgium).     

空间与经济地理学理论构建

空间是地理学的核心概念之一,长期以来在地理学的研究中占据核心地位。地理学对于空间的认识由于受到多学科的影响和启示也在不断演变和发展,其中哲学和社会学对空间的理解对地理科学的影响极为深刻。经济地理学作为地理学的重要分支学科之一,短短百年历史就经历了数次研究思潮的变迁和学科地位的崛起。这一切都离不开经济地理扎根于空间。空间是经济地理理论创新的源泉。本文通过对地理学中的空间概念与经济地理发展脉络的对应阐释,进一步印证了上述观点。同时,本文指出空间不能被沦落到和地方、区位、区域等概念并列的地位,空间包含着后者,须进一步强化空间的第一位性。但是也不能忽略经济地理学中的方法论的创新,每一次空间理解的突破都伴随着研究方法的创新,但是方法的创新始终是第二位的。因为方法创新的背后隐含着空间理解的改变。     

Spatiotemporal data model for network time geographic analysis in the era of big data

There has been a resurgence of interest in time geography studies due to emerging spatiotemporal big data in urban environments. However, the rapid increase in the volume, diversity, and intensity of spatiotemporal data poses a significant challenge with respect to the representation and computation of time geographic entities and relations in road networks. To address this challenge, a spatiotemporal data model is proposed in this article. The proposed spatiotemporal data model is based on a compressed linear reference (CLR) technique to transform network time geographic entities in three-dimensional (3D) (x, y, t) space to two-dimensional (2D) CLR space. Using the proposed spatiotemporal data model, network time geographic entities can be stored and managed in classical spatial databases. Efficient spatial operations and index structures can be directly utilized to implement spatiotemporal operations and queries for network time geographic entities in CLR space. To validate the proposed spatiotemporal data model, a prototype system is developed using existing 2D GIS techniques. A case study is performed using large-scale datasets of space-time paths and prisms. The case study indicates that the proposed spatiotemporal data model is effective and efficient for storing, managing, and querying large-scale datasets of network time geographic entities.     

“Teaching Against Culture” in Geography of Islam

This article explores various ways of how to challenge the “otherness” of Islam and Muslims when teaching geography of Islam. It suggests a critical project of “teaching against culture,” which challenges essentializing notions of Islam as a monolith, and rather demonstrates the complexity of Muslim geographies and “lived” Islam. Furthermore, it implies examining the various identity categories and binaries such as secular–religious and West–East that come about in the classroom itself in the secular academic context of an urban state university. As such, the article engages in questions of significance to a wider set of courses on social and cultural geographies, geography of religion, and postcolonial geographies     

行为地理学的学科定位与前沿方向

始自行为革命,行为地理学逐渐走向多元化的发展方向,不断扩展自身的理论框架和实践外延,反思并重新认识自身的意义,成为了人文地理学的重要组成部分。伴随着社会经济转型的深入,世界越来越向着多样化、个体性、动态化发展,人们的空间行为决策、选择的差异与个性越来越明显,空间与行为的交互越来越强,为行为地理学带来了新的发展机遇。论文通过梳理行为地理学的学科基础,提出行为地理学的学科定位与内涵外延,并指出行为地理学已经呈现出面向动态人地关系、面向个体生活质量及面向社会可持续发展3个前沿发展方向。在此基础上,论文对行为地理学面临的方法论、研究方法与跨学科的挑战进行讨论,并展望行为地理学的未来发展,以期为中国行为地理学的理论创新与实践探索提供启示。     

Theorizing and Researching Intersectionality: A Challenge for Feminist Geography*

This article focuses on the concept of intersectionality, which is being used within the wider social sciences by feminists to theorize the relationship between different social categories: gender, race, sexuality, and so forth. Although research within the field of feminist geography has explored particular interconnections such as those between gender and race, the theoretical concept of intersectionality as debated in the wider social sciences has not been addressed. This article attempts to respond to that omission. It begins by tracing the emergence of debates about the interconnections between gender and other identities. It goes on to reflect on attempts to map geometries of oppressions. The emphasis then moves from theorizing intersectionality to questioning how it can be researched in practice by presenting a case study to illustrate intersectionality as lived experience. The conclusion demonstrates the contribution that feminist geography can make to advance the theorization of intersectionality through its appreciation of the significance of space in processes of subject formation. It calls for feminist geography to pay more attention to questions of power and social inequalities.     

国际上的政治地理学研究进展与启示————对《Political Geography》杂志2005-2015年载文的分析

通过对国际上的政治地理学旗舰性杂志《Political Geography》2005-2015年期间391篇成果的分析,总结出国际政治地理学研究的主要研究议题为:边境与边界,环境政治,空间与尺度,领土和主权以及安全问题,选举地理,社会和文化政治,其中空间与尺度,领土和主权以及安全问题,社会和文化政治几个方向研究成果占较大比例,而其他三个方向则相对较少.通过研究方法分析发现,国际政治地理学主要采用定性分析的方法,尤其是民族志和文本分析的方法,定量分析的使用存在一定的局限性.最后,从该杂志的研究对象和研究机构两个方面的分析归纳出:欧美主导的发达国家(尤其是英国和美国)对世界政治地理学话题的学术霸权与世界南,北差异发展具有一定的相关性.在中国综合国力日渐增强,参与国际事务能力不断提高以及作为新兴的地缘政治力量崛起的社会历史背景下,政治地理学经世致用之能亟待被展现.因此,中国政治地理学发展作为发展中国家的声音势必将越来越洪亮.     

STRUCTURATION THEORY AND ATTEMPTS AT INTEGRATION IN HUMAN GEOGRAPHY*

Integration in human geography is achieved through multidimensional research or by the study of a variety of aspects of a whole. Giddens's structuration theory provides a new theoretical framework for integrative study in human geography in its attempt to connect individuals and societies, context and composition, time and space. Integrative studies in geography have focused on space (regional geography), time (historical geography) and society (time-geography). Structurationist analysis in geography can put society, space, or society and space at its focus. Thrift's spatial structurationist theory may lead to a new theoretically-based regionalism. On the other hand, integration at one level or between several elements may entail disintegration, at another level or element respectively.     

APPLIED GEOGRAPHICAL RESEARCH IN EAST AFRICA

Integration in human geography is achieved through multidimensional research or by the study of a variety of aspects of a whole. Giddens's structuration theory provides a new theoretical framework for integrative study in human geography in its attempt to connect individuals and societies, context and composition, time and space. Integrative studies in geography have focused on space (regional geography), time (historical geography) and society (time-geography). Structurationist analysis in geography can put society, space, or society and space at its focus. Thrift's spatial structurationist theory may lead to a new theoretically-based regionalism. On the other hand, integration at one level or between several elements may entail disintegration, at another level or element respectively.     

从实时定位、环境监测到神经生理：行为地理学技术发展前沿

方法与技术的前沿性是行为地理学的学科特色,技术视角的学科梳理有助于认识行为地理的自身价值与优势。论文回顾了实时定位、环境监测与神经生理3项技术的发展脉络,围绕行为背景、行为环境、行为体验的技术应用进行了综述,并总结了空间—行为互动、地理背景不确定性、批判神经地理的理论推进与批判反思;进一步构建了融合动态背景—精细环境—实时体验的全面技术框架,形成了从背景到环境再到体验的行为地理综合研究体系,并提出了神经生理技术融入行为地理学研究的理论提升方向。论文旨在贡献地理流动性背景下的行为地理学创新路径,服务于行为地理学的知识生产与理论发展。     

Festivals as a subject for geographical research

Festivals are an increasingly common phenomenon. They strongly influence geographical space, and so are studied in depth by geographers. The author shows that festivals are a subject for research in different geographical sub-disciplines. The author also defines the research paradigm of the geography of festivals as a part of human geography. He also establishes the main aspects of festival research in geography: cultural, social, economic and time–space analysis, political, historical, general and theoretical. Finally, he suggests future directions in geographical research on festivals.     

日常生活数字化转向的时间地理学应对

信息和通信技术(ICTs)对日常生活产生重要影响,而时间地理学及时应对了日常生活的数字化转向。论文梳理了日常生活数字化转向的基本特征,包括破碎化、多任务与时空替代等方面。相关实证研究试图回答ICTs是否以及如何改变日常生活,但是忽略了对其内在机制的阐释。时间地理学应对日常生活数字化转向的最新研究包括理论扩展与可视化及分析工具发展等方面,这为理解与刻画日常生活的数字化转向提供了新的理论框架与有效工具。研究发现,首先,经典时间地理学的理论和概念可扩展应用于虚拟空间中的行为。时空间去耦合是日常生活数字化转向的内在机制。其次,基于GIS开发了物质—虚拟混合空间行为的可视化和测度方法。最后,新时间地理学对日常活动复杂情境的分析直观揭示了日常生活数字化转向的时空去耦合机制与破碎化、多任务、时空替代等基本特征,并提出前后台活动、ICT介导的活动束、ICT介导的秩序口袋等理解移动ICTs影响下日常活动转型的创新概念。最后,以时间地理学为基础,提出以实虚活动系统为核心的日常生活数字化转向研究框架,并从数字生活、智慧社会和安全城市等方面讨论未来研究议题。     

物联网时代信息地理研究的思考

近年来物联网在全球掀起巨大热潮。作为新一代信息技术,物联网不仅将给生产运行、经济和社会管理乃至个人生活带来极大影响,同时将会给地理学带来深刻变化,成为信息地理研究的重要对象。深入分析物联网对于地理学核心概念以及信息地理研究方法带来的影响,构建物联网时代信息地理研究的理论框架,主要包括:物联网构造了新的地理空间--现实地理空间与虚拟空间的统一体,推动人地关系的改善;物联网时代的信息实时收集与处理特征,使得空间结构、产品空间、行为空间发生重要变化,信息作为区位的影响因素将得到增强,城市交通、居住、工作和休憩功能空间受到影响,物联网从规范产业链和改变消费行为两个方面影响商业模式,人的环境感应能力增强,影响人们的空间感知和空间行为;基于物理世界的海量实时数据,信息地理研究方法发生变化,实证、时间维度、微观尺度等方面的研究将会增强。进而,系统性提出物联网时代信息地理的主要研究内容。