University of Southampton OCS (beta), CAA 2012

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Calculating Accessibility
Irmela Herzog

Last modified: 2011-12-15


Accessibility to fresh water, good soil, salt and raw material like flint stones played an important role in prehistory. For example, accessibility to water is an important factor included in most archaeological predictive models.

Several definitions for the geographical term accessibility exist. Accessibility is often determined in relation to target locations, for example accessibility to fresh water supply. The geometry of the target locations are often points (e.g. sources) but could also be lines (e.g. streams). The simplest approach to calculate accessibility is based on the presence or absence of a target, more refined methods take several targets and their weights into account, for example the amount of water available at a fresh water supply.

In an archaeological context, accessibility often is considered as the ease with which a location may be reached from any other location in the area. The term general accessibility will be used in this context. Some studies assume that an area was explored by the first settlers using corridors of high accessibility.

It will be shown that for archaeological landscape analysis, popular accessibility measures derived from the gravity model are computationally expensive and may produce unintuitive results. Instead this paper presents a more intuitive method for calculating accessibility which is inspired by kernel density estimation. The kernels take the topographic situation into account, i.e. least-cost distances are calculated instead of Euclidian distances.

General accessibility depends on the scale of the analysis, a location which is highly accessible on a local scale may hardly be reachable on a more global scale. The bandwidth parameter of kernel density estimation can be used to control the scale of the accessibility measure.

The Bergisches Land in Germany provides the test region where the concepts and methods presented in this paper will be applied. 


Accessibility; Kernel density estimation; GIS