New Contributions on the Dome of the Pantheon in Rome: Comparison Between the Ideal Model and the Survey Model

Abstract

ABSTRACT:This work proposes an integrated survey and a study of the intrados of the dome of the Pantheon in Rome. An actualized architectural survey of the interior of the dome can generate useful material for future studies. The survey has been realized by using in a first stage the digital photogrammetry and in a second stage the three-dimensional laser scan technology. The compared analysis between different methods applied in the same object is useful towards a closer approximation to real dimension. Among several aspects that arise in dealing with the Pantheon this work focuses mainly on the study of the geometry of the inner surface of the dome. The specific goal of the research is to verify the spherical form of the surface and the coffers' distribution. In this sense it takes an important place the extracting data system. In order to realize the analysis it was applied a critical treatment of selected information contained in the point cloud. The use of plan and section drawings connects to the study of three dimensional models. The research is based on the construction of an ideal geometrical model that derives from the theoretical model described in the historical documents. The survey points model, which keeps the irregularities of the actual form, determines the creation of an average sphere, that is a regular model defined by clarifying geometrical laws. The direct comparison between the survey model and the ideal model contributes to the building understanding. It detects irregularities or deformities where they exist, and provides objective and quantifiable data.

Geometrical Analysis of the Coffers of the Pantheon’s Dome in Rome

“…This difference has an impact on the radial arrangement of the coffers and generates the divergence of the bisector that was registered by the comparison of the survey model and the ideal model. Moreover, as in our previous study (Aliberti et al 2014), the bisector of this sector shows a gap with the North-South axis. This divergence from the average value was distributed evenly between the six sectors of the second quadrant in order to generate a uniform image of the soffit frame.…”