Harvey J. Miller

Modelling accessibility using space-time prism concepts within geographical information systems.

Abstract The space-time Of time geographical framework is a powerful perspective from which to analyse human behaviour. One of the central concepts in this framework is the space-time prism, which models individual accessibility to an environment. In this paper, the derivation and manipulation of space-time prism concepts within a geographical information system (GIS) are discussed. The required system inputs and desired outputs are identified and a generic GIS based procedure is presented Given these basic requirements, issues are discussed which can determine the feasibility of current GIS technology to handle the derivation of space-time prism concepts.

Tobler's First Law and Spatial Analysis

‘‘ I invoke the first law of geography: everything is related to everything else, but near things are more related than distant things’’ (Tobler 1970). How could a sentence justifying heuristic calculations in a crude urban growth simulation generate an icon now known as Tobler’s First Law (TFL)? Why has this law resonated so strongly in geography? Waldo Tobler could invoke a first law of geography since the proposition that near things are more related seemed reasonable in 1970. It is enduring since near and related are useful concepts at the core of spatial analysis and modeling. And in 2004 and beyond, TFL is still useful since the rise of geographic information science and technologies allow greater sophistication when measuring and analyzing these concepts. This is ironic considering that Tobler apparently invoked the law in part to apologize for the slow computers at that time. I am going to sidestep the issue of whether TFL is in fact a law by noting that science accepts the concept of empirical laws, or compact descriptions of patterns and regularities. These are not required to be immutable truths (Casti 1990; Swartz 2001). We certainly have ample evidence to support TFL: you may have noticed on the way to work this morning that the world is orderly with respect to space. Scientific laws are also not required to be causal, for example, Newton’s Law of Gravity is not an explanation. Although not causal, TFL is consistent with an elegant process argument: overcoming space requires expenditure of energy and resources, something that nature and humans try to minimize (although not exclusively, of course). I accept TFL as reasonable regularity that generally holds true. The issues I am going to examine are the central roles of ‘‘near’’ and ‘‘related’’ to spatial analysis and the increasing levels of sophistication that we can achieve when measuring and analyzing these concepts. I also suggest that relations among near entities do not imply a simple, sterile geography; complex geographic processes and structures can emerge from local interactions. Indeed, the sensitivity of geographic and other phenomena to local interactions implies that we should carefully measure and analyze relations among near things.

THE HUB NETWORK DESIGN PROBLEM: A REVIEW AND SYNTHESIS.

Abstract Hubs, or central trans-shipment facilities, allow the construction of a network where large numbers of direct connections can be replaced with fewer, indirect connections. Hub-and-spoke configurations reduce and simplify network construction costs, centralize commodity handling and sorting, and allow carriers to take advantage of scale economies through consolidation of flows. Such networks have widespread application in transportation. This paper presents a structured review of research on the hub network design problem. Three critical design questions need to be considered: (a) are the nodes in the network assigned exclusively to a single hub? (b) are direct node-to-node linkages permitted to bypass the hub facilities? and, (c) are the hub facilities fully interconnected? The nature and difficulty of the hub network design problem depends on the analysts judgement with respect to these questions. We review analytical research papers, and give brief empirical examples of eight different network design protocols.

GIS Software for Measuring Space-Time Accessibility in Transportation Planning and Analysis

Transportation systems exist to improve individual accessibility. However, emerging applications of GIS in transportation (GIS-T) and intelligent transportation system (ITS) focus on throughput (the amount of system flow) rather than accessibility. Throughput is related but not equivalent to accessibility. Sensitive transportation planning requires rigorous, realistic and tractable accessibility measures. This paper reports on the development of GIS software that implement space-time accessibility measures (STAMs). The STAMs reflect the benefits that individuals receive from the transportation system. They are easily interpreted, particularly with respect to changes in accessibility. The STAMs also consider the locations and travel velocities dictated by the transportation system as well as individuals’ daily activity schedules. Tractable computational procedures allow calculation of the STAMs for detailed, urban-scale transportation networks. A prototype ArcInfo®-linked software system that runs on Windows NT® or Sun Solaris® platform implements the STAMs with user-friendly interfaces and project management tools.

What about People in Geographic Information Science

Geographic information systems (GIS) are convenient and potentially powerful platforms for transportation and urban analysis. Most GIS-based tools for transportation and urban analysis continue a place-based representation that is increasingly ill-suited to answer important questions in theory, policy and practice. The increasing disconnection between people and places means that a people-based representation is required to address questions of access, exclusion and evolution at the forefront of transportation and urban analysis and policy. A people-based GIS can be achieved by integrating principles from time geography and activity theory with geographic information science (GISci) representational theories and geographic information technologies. This paper reviews the principles, state of the art and research needs for a people-based GIS based on integrating time geographic and space-time activity concepts with the theories and tools of GISci and GIS. Filename: what about people v16 Last save: December 10, 2001 2:00 PM 1 This title is an homage to the classic paper by Torsten Hägerstrand, “What about people in regional science?” (Hägerstrand 1970).

Necessary space - Time conditions for human interaction

Key scientific and application questions concern the relationships between individual-level activities and their effects on broader human phenomena, such as transportation systems and cities. Continuing advances in geographic information science, location-aware technologies, and geosimulation methods offer great potential for observational and simulation studies of human activities at high levels of spatiotemporal resolution. The author contributes by developing rigorous statements of the necessary space–time conditions for human interaction by extending a measurement theory for time geography. The extended measurement theory identifies necessary conditions both for physical and for virtual interaction. The theory suggests elegant and tractable solutions that can be derived from data available from location-aware technologies or geosimulation methods. These conditions and their solutions could be used to infer the possibilities for human interaction from detailed space–time trajectories and prisms generated from observation or simulation studies.

A Field-Based Theory for Time Geography

Classic time geography is powerful but rigid, admitting only uniform travel velocities. Computational time geographic methods that resolve the uniform velocity assumption through transportation networks or isochrones only partially address this weakness and do not have a rigorous theoretical foundation. This article develops an analytical time geographic theory for the case where travel velocities vary continuously across space. Using the continuous transportation or “urban fields” tradition in quantitative geography and regional science, this article formulates analytical definitions of the space–time path and prism for the case where unobserved components are characterized by minimum cost curves through an inverse velocity field rather than straight line segments through a uniform velocity plane. This provides a geometrically and visually oriented approach to capturing complex velocities that complements existing methods. Time geographic fields also generalize time geography as the classic and isochrone versions are special cases; these now have a rigorous analytical foundation. It also can extend the network approach by treating links as regions with continuously varying velocities. Time geographic fields are also useful for nonnetwork-constrained phenomena such as movement through terrain, water, and air. This article illustrates the approach using a computational implementation based on a lattice approximation.

Representation and Spatial Analysis in Geographic Information Systems

Abstract A common—perhaps modal—representation of geography in spatial analysis and geographic information systems is native (unexamined) objects interacting based on simple distance and connectivity relationships within an empty Euclidean space. This is only one possibility among a large set of geographic representations that can support quantitative analysis. Through the vehicle of GIS, many researchers are adopting this representation without realizing its assumptions or its alternatives. Rather than locking researchers into a single representation, GIS could serve as a toolkit for estimating and exploring alternative geographic representations and their analytical possibilities. The article reviews geographic representations, their associated analytical possibilities and relevant computational tools in the combined spatial analysis and GIScience literatures. The discussion identifies several research and development frontiers, including analytical gaps in current GIS software.

User-Centred Time Geography for Location-Based Services

Abstract Location‐based services assist people in their decision‐making during the performance of tasks in space. They do not consider the users individual preferences, time constraints and possible subtasks to be performed. In order to account for these important aspects, a user‐centred spatio‐temporal theory of location‐based services is required. We propose such a theory by combining classical time geography with an extended theory of affordances. It assumes that affordances belong to three realms: physical, social‐institutional, and mental. In addition to covering the capability, coupling and authority constraints from time geography, this allows for a user‐centred perspective because affordances describe action possibilities with regard to a specific person. Furthermore, the integration of mental affordances offers the possibility to account for cognitive time constraints due to the duration of decision‐making processes. This new theory for location‐based services is closer to the individual user and more plausible with respect to their daily lives. A business traveller scenario is used as a case study to demonstrate this.

Activities in Space and Time

This chapter discusses theories and methods for analyzing the interrelationship of human activities in space and time, focusing on time geography; and elegant and powerful framework. The relevance of time geography for analyzing real world transportation and communication systems has improved tremendously in recent years with the rise of geographic information technologies such as geographic information systems (GIS) and the global positioning system (GPS). At the same time, information technologies such the Internet and mobile telephone have drastically altered the relationships between geo-space and time in the real world, creating fascinating and imperative research challenges. The “new time geography” has great potential for guiding land use and transportation systems toward more livable and sustainable outcomes.