Percolation Analysis – Archaeological Applications at Widely Different Spatial Scales

Abstract

This paper provides a summary of the percolation method of cluster analysis, and then describes two detailed archaeological case studies where the technique is applied at significantly different geographical scales. This demonstrates not only the potential for the technique within archaeology, but also how it can be applied at different spatial scales with different objectives appropriate to the specific problem in question. The technique, originally developed in physics and more recently adopted in geography, is a way of identifying groupings or clusters, purely based on spatial separation using Euclidian distance. The paper includes a discussion comparing percolation analysis with other clustering techniques already established within archaeology. The first case study uses percolation analysis as an exploratory tool for investigating the distribution of hillforts in Britain, identifying clusters and groupings at a national scale. The purpose is to identify possible socio-political entities for further investigation. In the second case study, the technique is applied to excavated features at a sub-regional level, in Saxony-Anhalt, central Germany, with the different objective of identifying settlement sites along a 13 km strip excavation. The aim here was to arrive at estimates of settlement sizes, which in turn can inform landscape archaeological surveys for deciding on the attribution of single finds to an already known site or registering a new site. Percolation analysis is shown to be an effective tool for analysing archaeological data sets at widely different geographical scales and should become a standard part of the archaeologist’s spatial analysis toolkit.

Keywords

• percolation analysis
• spatial clustering
• spatial scale
• geo-statistics
• scripting language r