L’analisi grafica dei documenti d’archivio quale strumento per “leggere e conoscere” il progetto della fortificazione alla moderna

From the second half of the fifteenth century the fortification ”alla moderna” marks the passage from the medieval defensive system to the protection of the city being entrusted to the pentagonal bastions. In this period drawing acquires importance where the project lines simulate the trajectories of the bullets and the cross-fire of the bastions and the geometric matrices change the medieval shape of the cities. There are numerous writings with the aim of showing and explaining technical choices, rigorous models and plastic design solutions. A design approach, that allows a mutual coverage of the bastion, which requires a few lines, designed to show the existing works and the new defensive line. The scientific discipline of “drawing” actively participates in the study of these “war machines” and provides its contribution with the architectural survey and the representation of digital models of realized works or only designed solutions; the scientific sector also supports the historical - archaeological research, guides towards the identification of metric scales adopted in the construction sites. Alghero, Spanish fortress of Sardinia, shows the application of this line of research, thanks to the archival documents that describe the events that have characterized the construction phases of the fortress in the second half of the sixteenth century.