The St Mark’s Basilica Pavement: The Digital Orthophoto 3D Realisation to the Real Scale 1:1 for the Modelling and the Conservative Restoration

Abstract

The pavement of St Mark’s Basilica in Venice is very famous for its historical-artistic importance, for its undulation, for the richness of the materials. Conservative restoration and the necessity of a precise acquaintance of the entire mosaic induced to the digital relief in scale 1:1 of all the musive surface to obtain a 3D orthophoto. In a first test area, and in a subsequently area about 40mq in the right transept, technologies, elaborations, instruments for the appraisal of the operating feasibility of a relief have been experienced. After the verification of the relief feasibility 3000 targets have been placed on the pavement (one; each 80 cm per 2000mq), those ones have been topographically surveyed by the means of a total station and they have been levelled in altitude.

All has been punctually geo-referenced in the national cartographic system.

With an high resolution metric digital camera, employing a f/40mm lens with nadiral shot about 2.20m have been realized more than 2000 shots. Ground pixel measures 0,5mm.

The DSM (Digital Surface Model), with lcm net, has been obtained by the auto-correlation of the image by the means of Socet Set 5.2.0 software property of BAE System.

As from the DTM we finally proceeded with the realization of the 3D orthophoto of the all pavement.

This one gives us the correct position of each pavemental tessera and permits a totally automatical form to extract altimetric profiles between prearranged points and so realize, always automatically, templates for the restoring of the basement with his characteristical undulation.