A Multi-technique GIS Visibility Analysis for Studying Visual Control of an Iron Age Landscape

Carme Ruestes Bitrià

Departament de Ciències de l'Antiguitat i l'Edat Mitjana, Universitat Autònoma de Barcelona. Email: MariaCarme.Ruestes@uab.cat

Cite this as: Ruestes Bitrià, C. 2008 A Multi-technique GIS Visibility Analysis for Studying Visual Control of an Iron Age Landscape, Internet Archaeology 23. https://doi.org/10.11141/ia.23.4


This article proposes a multi-technique GIS (Geographical Information System) approach to visibility analysis intended to address some of the shortcomings of the traditional binary viewshed. Its ultimate aim is to obtain more accurate viewsheds and, thus, gain more robust archaeological conclusions from their analysis and interpretation.

Composite image showing viewsheds of study area

A number of methods have been put forward to overcome the limitations of traditional binary viewsheds (e.g. Wheatley and Gillings 2000). However, the majority of practical applications, based upon binary viewsheds, tend to concentrate on only one of several methodological issues that affect the accuracy of viewsheds (e.g. multiple viewer points). At best, this can lead to flawed archaeological interpretations.

The enriched methodological protocol presented here combines a variety of procedures in an effort to obtain viewsheds that offer a more complete and accurate delineation of visible areas while explicitly acknowledging the reduction in visual clarity with increasing distance. The approach advocates the use of multiple viewer points coupled with 'probable' viewsheds i.e. viewsheds that are sensitive to the errors inherent to the DEM used to generate them. The result is a 'most probable' viewshed that can be carried forward for more structured investigation such as 'Higuchi' and 'cumulative' analyses.

This method is used to investigate visibility from the Iberian hillforts that dominated the landscape surrounding Badalona (north of Barcelona, Catalonia, Spain) during the 3rd century BC. The study of visual control from the hillforts is understood as a means to deal with notions of social structure and hierarchy. Visibility analysis indicates a highly structured society, where each hillfort might have primarily controlled given zones of the landscape and might have informed others through an integrated visibility network about events taking place there.


Wheatley, D.W. and Gillings, M. 2000 'Vision, perception and GIS: developing enriched approaches to the study of archaeological visibility' in G. Lock (ed) Beyond the Map: Archaeology and Spatial Technologies. Amsterdam, 1-27.

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Last updated: Tues Mar 04 2008