MULTISOURCE UPDATING AND FUSION OF GEOGRAPHIC DATABASES

It is increasingly important to deal with updated geographic databases in order to ascertain any spatial analysis for decision making in urb an planning. However, if updating a conventional database (e.g., chang ing the delivery address in a custom file) can be done by means of a S QL-type language or via a form interface, in the domain of geographic databases, updating means different things and cannot be performed eas ily. The essential reason is because updating information is not only elementary, but rather coming from different sources such as newly mad e measures, aerial photos, scanned maps, and so on. Indeed, in this ca se, updating or multisource integration can mean: local cartographic u pdates - that is to say, to integrate newly made measures into a datab ase storing old measures: in this case, sometimes some points or some segments must move a little bit, possibly replacing segments by piece- wise lines and so on, possibly by means of elastic transformations; gl obal updates - for instance, using aerial photos in order not only to detect clandestine buildings but also to automatically shift all point s of the database; this can be done by defining control points; extens ion of the coverage - in other words, when we have to fuse maps of two neighbouring zones whose boundaries do not meet, it is necessary to s elect control points and to perform rubber-sheeting at the vicinity of the boundary based on those control points; updating for measurement or topological error correction - that is, reconstruction of badly str uctured databases based essentially on topologic information; this can be achieved on a single layer (e.g., transformation of a spaghetti-li ke cadaster into a real parcel-oriented cadaster, closure of polygons) or on multiple layers (e.g., to ensure that a building is not astride the neighbouring parcels). In this paper we will give an overview of problems to be solved together with some solutions in order to perform such different kinds of updating.