Visibility Graph Analysis (VGA) is a relatively new method of computational spatial analysis derived from Space Syntax, a group of related methods for measuring the social effects of architectural space. Space Syntax interpretation of Roman houses using access analysis view the house as a hierarchical system that controls the entry of visitors through an essentially axial layout. These results can be combined with literary sources about room function to interpret the interior courtyards in larger houses as producing a separation of space into public and private (von Stackelberg 2009; Grahame 1997, 2000). This study demonstrates how comparison of visibility integration graphs to access analysis results challenges previous interpretations of this spatial hierarchy. The poster shows the global and local visibility graphs of six houses in Herculaneum Insula V and Insula VI made using the UCL Depthmap 8 software. These houses have various of atria and peristyles which function as courtyard spaces. None of the houses have the complete suite of rooms of the ideal house represented in Roman architectural manuals, and half are on irregularly shaped plots. Regardless of size, courtyard arrangement, or symmetry, courtyard spaces consistently have the highest visibility integration.This visual dominance does not always correlate to the relative accessibility of the space as measured by access analysis. While visibility is a major factor in determining proximity for sociability in Space Syntax (Hillier and Hanson 1984), visibility integration is not a predictor of movement (Turner, Doxa, O'Sullivan and Penn 2001). The findings show an alternate version of spatial hierarchy in which visually dominant courtyard spaces allow display and surveillance of movement within the house. The problems of interpretation that VGA introduces also demonstrates the difficulties of using Space Syntax theory for domestic interiors. If "privacy" as measured by Space Syntax cannot be correlated simply to accessibility or visibility integration in these types of structures, these results suggest how Space Syntax can compensate for the undertheorization of privacy by combining methods.
