Ranking spaces for predicting human movement in an urban environment

Abstract

A city can be topologically represented as a connectivity graph, consisting of nodes representing individual spaces and links if the corresponding spaces are intersected. It turns out in the space syntax literature that some defined topological metrics can capture human movement rates in individual spaces. In other words, the topological metrics are significantly correlated to human movement rates, and individual spaces can be ranked by the metrics for predicting human movement. However, this correlation has never been well justified. In this paper, we study the same issue by applying the weighted PageRank algorithm to the connectivity graph or space–space topology for ranking the individual spaces, and find surprisingly that: (1) the PageRank scores are better correlated to human movement rates than the space syntax metrics, and (2) the underlying space–space topology demonstrates small world and scale free properties. The findings provide a novel justification as to why space syntax, or topological analysis in general, can be used to predict human movement. We further conjecture that this kind of analysis is no more than predicting a drunkard's walking on a small world and scale free network.

Keywords:

• Space syntax
• Topological analysis of networks
• Small world
• Scale free
• Human movement
• PageRank

Acknowledgements

The study reported in the paper is financially supported by a Hong Kong Polytechnic University research grant. An earlier of this paper was presented at the XXIII International Cartographic Conference, 4–10 August 2007, Moscow, Russia. The author is grateful to Chengke Liu for his research assistance, and Amy Langville and David Gleich for their timely advice on efficient computation of PageRank. One of the referees provided constructive comments that better shaped the paper. However, any shortcomings are my sole responsibility.

Notes

1. A space syntax program based on Macintosh computer, developed by Bartlett school of University College London.

2. A suite of freeware space syntax programs implemented as an extension of ESRI GIS family or as a standalone application and Java applet; for downloading refer to http://www.hig.se/˜bjg/Axwoman.htm

3. Since a web graph is directed, there are two kinds of connectivity for any node: inlink connectivity (coming to the node) and outlink connectivity (outgoing from the node).