An approach to comparing different ontologies in the context of hydrographical information

Geographical Information is increasingly captured, managed, and updated by different cartographic agencies. This information presents different structures and variable levels of granularity and quality. In practice, such heterogeneity causes the building up of multiple sets of geodata with different underlying models and schemas that have different structures and semantics. Ontologies are a proposal widely used for solving heterogeneity and a way of achieving the data harmonization and integration that Geographical Information Systems (GIS) and Special Data Infrastructures (SDI) need.This paper presents three hydrographical ontologies (which are built using top-down and bottom-up approaches) and an approach for comparing them; the goal of this approach is to prove which ontologies have a better coverage of the domain. In order to compare the resultant ontologies, six qualitative facets have been studied: sources used (amount, richness, and consensus), reliability of building approaches (community extending use, recommend-dations), ontology richness (number and types of components), formalization (language), granularity (scale factor), and the design criteria followed.