Multiple data source for survey and modelling of very complex architecture

In this paper we would like to present a possible operating way to survey and model a very complex architecture, integrating different kinds of instrumentation and modeling methods. In particular we would like to convoy the attention on a possible measure and data elaboration procedure that allows collecting and post-elaborating data in a short time in order to both extract classical architectural products, such as sections and profiles, and to build complete and accurate 3D models. The necessity is to structure multi-data source procedure buds inside a five years project (still in progress) with the goal to survey and three-dimensionally model the Main Spire of Milan Cathedral. It is a very complex "object" and, for this reason, it can be considered a very challanging and useful test field for the new 3D survey technologies and, in particular, for the various "real-based" modeling methodologies. In the paper are described the survey workflow and the relative elaboration steps, focusing on the problems and justifying the key choices.