The layout of icosakaidígono in the Jupiter-Ammon Clypeus of Tarragona (Ist century) and the face of Christ of the Rosette in the Cathedral of Orvieto (14th century)

Identifier:  PC:2682

Handle: https://hdl.handle.net/20.500.11797/PC2682

Authors:  Lluis i Ginovart, J.; Samper, A.; Coll-Pla, S.; Costa-Jover, A.

Abstract:
The techniques of massive data capture, as the Terrestrial Laser Scanner and the digital photogrammetry, allow to accurately analyze close objects and others that are not accessible, by statistical methods. Its application has allowed assessing, from the geometric point of view, the sculptures of the figure Clypeus of Tarragona, Jupiter-Ammon (1st century) and the one of the Orvieto's Cathedral rosette, with the face of Christ (14th century). The Clypeus of Tarragona and Orvieto's rosette are divided in 22 parts, forming a polygonal shape known as icosakaidígono. This polygon does not appear in the Elementa of Euclides, neither in the Almagesto of Ptolomeo, nor in the rare Practica Geometriae of the time. These polygons can be built by means of angular division inherited from astrolabe and quadrant builders. This polygon can be defined also through the rotation of the square, since the repeated support of the catheti on the hypotenuse allows the rotation of the tool, or other indirect methods. The conclusion of the analysis of these figures is that, statistically, both sculptures have a geometric construction equal to the Reliquiario del Corporale del Miracolo di Bolsena (1337-1338) of Orvieto's Cathedral.