A computer simulation to test the Buchner thesis: The relationship of the Ara Pacis and the meridian in the Campus Martius, Rome

3D modeling was first introduced into the fields of archaeology and art history in the early 1990s as a new form of illustration derived from the traditional paper-based plan, section, and elevation. In recent years, it has become clear that once we have an accurate 3D restoration model of a lost or damaged cultural heritage monument, we can use the model to pose new questions and generate new discoveries and insights. This paper will consider this heuristic use of 3D models in the field of archaeoastronomy. A simulation of a built environment that includes an accurate solar tracker with historical azimuthal data drawn from NASA's Horizons System can allow us to test alignments hypothesized in the scholarly literature and to discover hitherto unsuspected alignments. We will report on our development of a Unity simulation of the northern part of the Campus Martius in Rome during the period 8 BCE to 40 CE. We made the simulation in order to test the validity of a thesis first proposed by Edmund Buchner in the 1970s according to which two Augustan monuments built in this part of the city were designed to have a solar alignment on Augustus' birthday: the so-called Horologium Augusti and the Ara Pacis. Since Buchner wrote, his thesis has been hotly debated by Roman topographers. A computer simulation may be able to move research on this topic beyond the current impasse.