Morton E. O’Kelly

Spatial interaction models from Irish commuting data: variations in trip length by occupation and gender

Core and peripheral contrasts in journey-to-work trip length can be interpreted as imputing the relative value of origin and destination accessibility (yielding theoretical proxies for rent and wages). Because the main variables are shown to be critically dependent on spatial structure, they may be interpreted as showing the shadow prices due to comparative location. There is also a unifying connection between these results and the existing literature on many dimensions: rent gradients, accessibility, and emissivity. In an empirical example, the advantages of a panoramic view of national commuting statistics are shown, using an Irish data set. Variations in the rates of participation in trip making by location, occupation, and gender are examined. Places that emit more trips than would be expected from their relative location are identified. Further, examining ways in which such emissivity is sensitive to a change in trip length highlights the regions where trips could possibly be adjusted to produce a shorter average trip length or which might be especially sensitive to reduction in employment. A careful reinterpretation of one of the key outputs from a calibrated spatial interaction model is shown to be consistent with the declining rent gradient expected from Alonso’s theory of land use.

A bootstrap based space–time surveillance model with an application to crime occurrences

This study proposes a bootstrap-based space–time surveillance model. Designed to find emerging hotspots in near-real time, the bootstrap based model is characterized by its use of past occurrence information and bootstrap permutations. Many existing space–time surveillance methods, using population at risk data to generate expected values, have resulting hotspots bounded by administrative area units and are of limited use for near-real time applications because of the population data needed. However, this study generates expected values for local hotspots from past occurrences rather than population at risk. Also, bootstrap permutations of previous occurrences are used for significant tests. Consequently, the bootstrap-based model, without the requirement of population at risk data, (1) is free from administrative area restriction, (2) enables more frequent surveillance for continuously updated registry database, and (3) is readily applicable to criminology and epidemiology surveillance. The bootstrap-based model performs better for space–time surveillance than the space–time scan statistic. This is shown by means of simulations and an application to residential crime occurrences in Columbus, OH, year 2000.

A lattice covering model for evaluating existing service facilities

Abstract.This article presents the following location problem: align a regularly spaced grid of new facilities as well as possible with a set of existing centres. The problem has some similarity to a problem in classical central place theory, namely the spatial arrangement of services with a particular range of coverage. The article poses the problem, gives a non-linear formulation, and details solution approaches. A robust heuristic, based on geometric insights, is also devised: if the basis for the new grid is centred on at least one fixed centre, an enumeration of various rotation angles will be effective for finding local minima (and maxima). As a practical application of this problem, a region may wish to supplement an existing system of fixed siren locations with additional facilities in such a way as to fill in, or complete, the partial coverage pattern. An evaluation of the siren system in Dublin, OH, USA, is utilised to demonstrate the effectiveness of the technique.

Rectilinear minimax hub location problems

The minimax hub location problem sites a facility to minimize the maximum weighted interaction cost between pairs of fixed nodes. In this paper, distances are represented by a rectilinear norm and may be suited to factory layout or street network problems. The problem is already well known (in 2-D) as the round trip location problem and is extended to 3-D in this paper. One rationale for the solution method is based on an extension of the geometric arguments used to solve the minimax single facility location problem. Suppose a budget is provided for interactions, and that each interaction must be accomplished for no more than this cost. The algorithm uses a bi-section search for the feasible budget until it finds the expenditure needed to provide for these flows. The extension in the present paper is that the nodes are permitted to be on different layers (levels). This 3-D version of the problem appears to be a new variant of the hub model. The models and solution techniques developed in the paper are illustrated using a small 55 node problem. Because of a relatively efficient implementation of the bi-section search, the algorithm in 2-D and 3-D is also applied successfully to a 550 node problem.

Isard’s contributions to spatial interaction modeling

Abstract.This short review, surveys Isard’s role in promoting what has become known as spatial interaction modeling. Some contextual information on the milieu from which his work emerged is given, together with a selected number of works that are judged to have been influenced (directly and indirectly) by his work. It is suggested that this burgeoning field owes a lot to the foundations laid in the gravity model chapter of “Methods”. The review is supplemented by a rather extensive bibliography of additional works that are indicative of the breadth of the impact of this field.

Global Airline Networks: Comparative Nodal Access Measures

Abstract One strategy for making sense of airline network complexity is to assess the empirical network against an appropriate benchmark. The purpose of this paper is to develop and use well known measurements of betweenness and to deploy them in the context of airline transportation nets. The paper demonstrates some structural differences that emerge in larger networks. Selected extreme values are computed, as benchmarks, from a hypothetical ideal hub network. Actual values are shown to largely comport with these expectations, but there are numerous and interesting exceptions.

The Role of Geographic Expertise in International Border Disputes: A Study of the Middle of Lake Erie Through Historical and Cartographic Perspectives

A great deal of consequence attaches to the placement, marking, mapping, and monitoring of borders and the lines that separate nations. Throughout the article attention is drawn to the role of geographic regional expertise and map analysis in providing the background for territorial and related disputes over sovereignty. This article traces, through maps, the evolving story of the international boundary between the United States and Canada in the vicinity of Lake Erie. Between the Treaty of Paris in 1783 and the delimitation of the actual boundary between the United States and the Dominion of Canada in Lake Erie in the 1820s, the depiction of the boundary was prone to two types of error: the gross inaccuracy of the base maps on which the lines were drafted and the imprecision of the words and methods used to describe or compute the location of the boundary. Although much less controversial than in the Northeast United States, where settlement was delayed until the Webster–Ashburton Treaty in 1842, the issues were nevertheless quite significant in Lake Erie. A series of partial efforts to describe the boundary, culminating in a fishery dispute, finally led to a definitive effort by the International Waterways Boundary Commission. Perhaps surprisingly, given the date of the original declaration in 1783, this did not happen until 1908. This article provides an opportunity to review both historical and cartographic aspects of the problem of defining a boundary in a water area and uncovers a forgotten gem—a paper that exactly described an appropriate analytical cartographic technique—the medial axis.