Semantic Referencing of Geosensor Data and Volunteered Geographic Information Simon Scheider, Carsten Keßler, Jens Ortmann, Anusuriya Devaraju, Johannes Trame, Tomi Kauppinen, Werner Kuhn Institute for Geoinformatics, University of M¨ unster, Germany simon.scheider|carsten.kessler|j ortm02|anusuriya.devaraju johannestrame|tomi.kauppinen|kuhn@uni-muenster.de Abstract. Georeferencing and semantic annotations improve the find- ability of geoinformation because they exploit relationships to existing data and hence facilitate queries. Unlike georeferencing, which grounds location information in reference points on the earth’s surface, seman- tic annotations often lack relations to entities of shared experience. We suggest an approach to semantically reference geoinformation based on underlying observations, relating data to observable entities and actions. After discussing an ontology for an observer’s domain of experience, we demonstrate our approach through two use cases. First, we show how to distinguish geosensors based on observed properties and abstracting from technical implementations. Second, we show how to complement annotations of volunteered geographic information with observed affor- dances. 1 Introduction and Motivation Observations are the principal source of geographic information. Humans share senses 1 and perceptual capabilities [1] that enable them to observe their envi- ronment, and thereby obtain geographic information. For example, vision works essentially the same way for all humans. Additionally, humans can easily under- stand and reproduce observations made by others, because they can understand intentions and join their attention in a scene [2]. If someone tells you that Main Street is closed due to construction works, you can easily understand what was observed without observing it yourself. Some of the authors of this chapter have previously suggested to use perceptual capabilities as common ground to de- scribe geoinformation [3, 4]. In this chapter, we demonstrate how to account for the semantics of geoinformation based on underlying observations. Our approach is general enough to account for observations obtained from technical sensors (such as a thermometer measuring temperature) as well as human observations (e.g., observing the presence of a construction site on Main Street). Dealing with the semantics of geoinformation in terms of observable proper- ties (such as temperature, precipitation rate, or traversability of a road), we face 1 With few exceptions, such as disabilities, that do not affect the general case.