Local and global approaches for the integration of up-to-date geo-db and ancient maps within the Atl@s portal

In the framework of the Atl@s portal project, aimed to achieve the georeferencing of historical cartography into modern mapping grids, in this paper a task concerning the integration of up-to-date spatial geo-db to ancient maps is presented. The main aim is to guarantee the web visualization and diffusion of the geo-iconographic historical contents in a detailed territorial dimension. The research is focused on algorithms and tools implemented within open source environment to support advanced georeferencing methodologies, to define and test technical specifications, and to improve an automatic approach. The standard procedure for georeferencing historical maps is based on the use of ground control points to compute an independent transformation for each map sheet (“local” approach). Here a “global” solution, which also includes some adjacency constraints between close sheets, is proposed. Furthermore, some initial tests are described by considering the “Map of the Astronomi di Brera” of Milano city (Italy, 1807), made up of 39 sheets at 1:1,000 scale