The sundial of Augustus and its survey: unresolved issues and possible solutions

Abstract

A lively debate has developed regarding the characteristics of the so-called Horologium Augusti, at first known only through a notice in Pliny and subsequently discovered (at least partly) during the course of excavations begun in 1997 (Leonhardt, in: The Horologium of Augustus: debate and context, 2014). The gnomon of the ''Horologium'' was composed by the obelisk that presently is nearby in ''Piazza Montecitorio'' in Rome (Fig. 1). A large part of the debate has centred on the very function of the Horologium, in particular whether it was a true functioning solar clock or simply a sundial. The scope of the present essay concentrates rather on the metrical accuracy that such a sundial could have had; in particular, we will hazard a hypothesis as to the accuracy with which the direction of the sundial was laid out and the possibility of measuring the azimuth 123Acta Geod Geophys (2016) 51:527-540 DOI 10.1007 in its present placement. Such a detailed geodetic-topographic survey of the portion thus far excavated, could provide useful information for the eventual pursuit of excavations yielding, at the same time, further avenues of research; as an example it would also allow for the deduction of two pieces of information still not entirely established: the exact height of the gnomon, and the exact position of the original placement of the axis of the obelisk.

A flexible and swift approach for 3D image–based survey in a cave

“…Specifically, several limitations apply to TLS when used in cave environments, such as the difficulty of transportation and positioning (Angelini et al 2017;Doneus and Neubauer 2005a, b;Stocchi et al 2017). On the other hand, traditional topographic instrumentation, due to lateral refraction effects, should be integrated by a gyroscope (Velasco-Gómez et al 2016) which, however, increases costs and makes the survey more complex (Baiocchi et al 2016). In such harsh environments, only SLAM (simultaneous localization and mapping) image-based technique provides acceptable results in acquisition time and automation.…”

Integrated Geomatic Techniques for Georeferencing and Reconstructing the Position of Underground Archaeological Sites: The Case Study of the Augustus Sundial (Rome)

“…The survey of an archaeological artifact such as the Sundial of Augustus, with its historical, archaeological and scientific importance unique in the world and in history, requires results that are at least as accurate as those that were used in its realisation. The task is obviously much more complex today, since the sundial itself is no longer on the walking surface of an unbuilt area, as it was at the time of its realisation, but about seven metres below the current ground level in a densely urbanised area [2,3].…”