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[....] First, a comprehensive data collection was done via a total laser station. The different data campaigns started showing a sequence of dots which revealed the particular shape of this vault (Fig. 7-9). First, we saw that the diagonal transverse arches were semi-circular arches; their crossing has a consequence on the height of the nave and that of the central keystone, at exactly 6, 69 meters from the impost level. It was confirmed that the transverse arches reach almost the same height, that is, the line of the ridge line between the central keystone and those of the transverse arches is slightly lower. On the contrary, the slope of the ridge lines is sharper, the keystones of the formeret arches are almost 2 m below the central boss stone.
The architect decided to reduce the height of the windows and, by this action, succeeded to lower the height of the cornices, and, therefore, the general cost of the building. The successive dots which allowed to draw the arches' curvatures let us know another interesting fact: first, that the transverse arches' curvature is exactly the same as the diagonal arches' curvature. This precise fact entails that, when designing the transverse arch the same way as the diagonal, the keystone 2 of the transverse lays naturally a bit lower than the central one. Secondly, it is found out that also the central arch is drawn with the same curvature as the diagonal; however, in this case, for it to reach the central keystone's height, it must be elevated vertically, that is, it is to be stilted in its base(Figs. 10 y 11).
Taking these data into account, we proceed to draw the vault's designs life size, as it was done in medieval stone masonry workshops (Fig. 16). These drawings, in plan and section, are indispensable for us to infer from them all the necessary data required to carve the different parts of the vault. In fact, medieval stone masonry as a whole is based on this skill to set correspondence between the plan and the elevation. Measure taking goes on, and, after detailed works with the total station, the voussoirs' profiles which can be drawn on the layout are precisely identified and we are able to extract from them the testa templates for their carving (Fig. 17). [....]
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