The cylindrical projection of architectural surfaces: the Caius Ennius Marsus’s mausoleum in Saepinum (Molise, Italy)

Abstract

In recent years, the Photogrammetry Laboratory at the Iuav University in Venice has carried on a strict collaboration with the Urban
Planning and Survey Laboratory at the University of Perugia. For years, the University of Perugia had been involved in the
archaeological investigation of the site of Saepinum, a Roman municipality in the Italian region of Molise. For the most part, the
collaboration concerned the survey of several urban and extra-urban areas and the thorough recording of the main monuments of the
Roman town.
Cultural heritage surveys and the digital elaboration of data often present problematics which require the implementation of new or
non-conventional procedures. This paper analyses a projection method useful to unwrap a curved surface, which has been applied to
the case study of the drum-shaped mausoleum of Caius Ennius Marsus.
Dating to the Octavian Augustus’ epoch, the monument is located along the path neighbouring the town’s wall. The mausoleum is
characterized by a cylindrical tower on top of a squared base and it is dedicated to a powerful magistrate from Saepinum.
In order to graphically represent its architecture and to enable analysis and conservation works, the curved surfaces of the monument
needed to be developed on a bi-dimensional plane surface, while maintaining metrical information unvaried.
In this direction, the team developed a specific software which allows to project laser scanning or photogrammetric point clouds of
curved surfaces onto a plane surface. Such procedure offers scholars a series of metrically accurate representations of the monument
useful to analyse the object and the ancient architectural techniques and, if required, design and plan conservation works.