The fourth edition of the International Conference on Geospatial Semantics (GeoS 2011) was held in Brest, France, during May 12–13, 2011.

Geospatial semantics (GEOS) is an emerging research area in the domain of geographic information science. It aims at exploring strategies, computational methods, and tools to support semantic interoperability, geographic information retrieval, and usability. Research on geospatial semantics is intrinsically multidisciplinary and therefore GeoS traditionally brings together researchers whose expertise will address issues from diverse fields such as cognitive science, geography, linguistics, mathematics, philosophy, and information technology.

The fourth edition of GeoS provided a forum for the exchange of state-ofthe- art research results in the areas of modelling and processing of geospatial semantics. Research in geospatial semantics is critical for the development of next-generation spatial databases and geographic information systems, as well as specialized geospatial Web services. Within the context of the Semantic Web, the need for semantic enablement of geospatial services is crucial, given the ever-increasing availability of mainly unstructured geospatial data. This problem is exacerbated by the very recent and ever-growing phenomena of crowd sourcing and volunteered geographic information.

These proceedings contain full research papers which were selected from among 23 submissions received in response to the Call for Papers. Each submission was reviewed by three or four Program Committee members and 13 papers were chosen for presentation. The papers focused on formal and semantic approaches, time and activity-based patterns, ontologies, as well as quality, conflicts, and semantic integration. Overall, a wide range of research efforts were presented by researchers from institutions in Italy, Mexico, France, Belgium, Japan, UK, USA, Switzerland, Portugal, and Germany.