The Ostia Forum Project OFP: geophysics, excavation and digital (2-D/3-D) documentation of the plazas and buildings in the city-center of Ostia antica from the 1st-6th century AD

Ostia is the first colony and the main harbour of Rome, approximately 30 km west of the capital of the Roman Empire. Ostia was an antique ‘metropolis’ with four- and five-storey high multiple dwellings. Thanks to large-scale excavations until 1941, Ostia is the biggest visible excavation-site of an antique city worldwide. Our excavation and survey-projects since 2010 are focussed on the political and administrative center of Ostia, the Forum. The period of Late Antiquity (4th century – 7th century AD) in Ostia remained largely unknown prior to our fieldwork activities. Many areas were never scientifically documented until today. Pavements were rarely recorded, even though there are relatively adequate plans of walls. Detailed plans exist only regarding high value floors like figured mosaics, not ordinary floors like simple mosaics, mortar beds, travertine and even marble pavements. The situation is even worse regarding plazas, with prominent examples like the Forum, which were never documented in detailed plans showing individual pavement slabs and the various traces of use and reuse. i) Archaeological surface cleaning. Our first aim was to do large scale surface cleaning to find out where previously unrecorded pavements have survived. As side-effect, we were able to trace and localise former undocumented excavation activities and define their extents. Under the vegetation layer, we found a surprisingly rich stratigraphy from late-antique occupation layers to middle age robbing pits and further on to 19th century early scientific excavation-activities ending with recent tourist trample and rubbish dumps. ii) Geophysical analysis. Our second aim was to do large scale geophysical analysis from 20 cm depth until 160 cm depth to find out where substantial remains of buildings can be detected and where areas of refill and previously undocumented excavations were situated. iii) Documentation of all antique surfaces. Based on surface cleaning, we tried to document all surface-evidence of surviving late antique stratigraphy and pavements. iv) Strategical stratigraphical-sondages. Based on geophysical analysis, our aim was to plan strategical fundamental sondages. By defining the limits of the previously undocumented excavation work until the 1950’s with help from old photographs, diaries, and the geophysical plans, it was possible to do minimal invasive excavation work. Trenches deeper than 30 cm were executed in previously excavated refill areas, with the purpose of cleaning and draw profiles in the status quo of the excavations from the late 19th and early 20th centuries. v) New documentation methods. New methods were developed to document previously unrecorded large-scale surfaces of plazas and buildings. Firstly, this regards the two-dimensional photo-mosaics with highest resolution digital photography. Secondly, three dimensional recording methods were used. That is 3-D laserscannings with colour informations and 3-D ortophotography with the aim to get point clouds of different resolution for wall painting, graffitti, and minimal surface traces on one hand, and large-scale brickwalls on the other hand. In order to document large areas in limited time we developed a complete digital recording system based on aerial photography with quadro- and octo-copters and supplementary high resolution photography from the ground. vii) 3-D reconstructions. Based on the point clouds and all available stratigraphical informations, the final aim of the project is to create 3-D reconstructions of all building phases of the city centre from the 3rd century BC to the 6th century AD. In comparison to existing 3-D models, we aim to develop a more precise differentiation between the original antique remains, modern conservation efforts and actual damage by erosion, and the hypothetical full reconstruction of its supposed antique shape. Ostia as an almost completely preserved metropolis. Late Antiquity in Ostia is one of the most fascinating periods of research – because there is still so much completely unknown material-evidence to uncover, which can change our perception of history and daily life of these times.