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Capturing human activity spaces: New geometries

Rai, R. K.; Balmer, Michael; Vaze, V. S.; Schönfelder, Stefan; Axhausen, Kay W.

FG Verkehrssystemplanung und Verkehrstelematik

Activity space, defined as “the local areas within which people move or travel during the course of their activities during a specified time period”, is a measure of an individual’s spatial behavior which captures individual and environmental differences and offers an alternative approach to studying the spatial reach of travelers. The shape and area of activity space is a product of how it is conceptualized and measured. This paper enlarges the set of geometries which can be used to describe activity space. It tests four parametric geometries (ellipse, superellipse, Cassini oval, and bean curve), which are identified as those capturing a specific share of all locations visited, i.e. 95%, while minimizing the area covered. They are estimated for a number of long-duration data sets while distinguishing between trip purposes. We present both a flexible, easily adaptable method for calculating activity spaces of different shapes and a qualitative comparison of the four above-mentioned shape types on the basis of the given surveys. We can thus demonstrate that the choice of an appropriate shape representing an individual’s activity space is highly dependent on the spatial distributions and frequencies of the locations visited by the person in the given time period.