Daniel P. Diffendale deposited Photomodeling Sant’Omobono. Meeting the challenges of topographic documentation in a waterlogged urban environment [Poster] on Humanities Commons 6 years, 2 months ago
The use of digital photogrammetric techniques to document archaeological layers and features has become increasingly common. Software such as PhotoScan uses multiple photographs of an object to model its geometry. In addition to providing more detailed topographical data than those acquired using a total station alone, such photomodeling offers solutions to problems posed by complex urban excavations. A deep sounding at the site of Sant’Omobono in Rome’s Forum Boarium presented special challenges for topographical documentation. The depth of the sounding and excavation below the water table necessitated the installation of steel sheeting to prevent slumping and collapse of the scarp. The initial height of the sheets above the sounding blocked sight lines and precluded the regular use of a total station to document excavation levels. At deeper levels within the sounding, the presence of sump holes, pumps, and occasionally standing water presented additional challenges to the creation of photomodels. The creation of photogrammetric models that included fixed points around the excavation area permitted not only the calculation of real elevation data but also the recording of detailed topographic data for each stratigraphic unit thus modeled. The resulting photomodels can also be used in the creation of traditional transparency overlay plans. Photogrammetric documentation in a single context recording system such as that used at Sant’Omobono has the further advantage of allowing the reconstruction of detailed vertical sections, not only along the limits of the excavated area, but also along any axis within it. Photomodeling also has a potential analytical value in allowing more accurate calculation of sediment-volume estimates than is possible using traditional techniques. The use of photomodeling at Sant’Omobono provides a model for dealing with the specific topographic challenges of urban excavations and for richer data collection in all excavation contexts.