Many applications refer to moving objects or phenomena and require spatio-temporal modelling and specific analysis. Unlike conventional data where attributes are simple values (numerical or textual), object motion defines a continue variation in space and time. This makes it difficult to handle such datasets, for instance, answering the query "how many objects cross a given area during a given time period?" This article addresses spatio-temporal data warehouse schema modelling in order to facilitate those queries and more generally, on-line analytical processing (OLAP) on spatio-temporal databases. It is illustrated on a space-time human activity survey database within the framework of a European IST project1 .