This thesis is addressing the fusion of geo-information from different data sources for time-critical geo-applications. Such geo-information is extracted from sensors that record earth observation (EO) data. In recent years the amount of sensors that provide geo-information experienced a major growth not least because of the rising market for small sensors that are nowadays integrated in smartphones or recently even in fitness wristbands that are carried at the body. The resulting flood of geo-information builds the basis for new, time-critical geo-applications that would have been inconceivable a decade ago. The real-time characteristics of geo-information, which is also getting more important for traditional sensors (e.g. remote sensors), require new methodologies and scientific investigations regarding aggregation and analysis that can be summarised under the term geo-information fusion. Thus, the main goal of this thesis is the investigation of fusing geo-information for time-critical geo-applications with the focus on the benefits as well as challenges and obstacles that appear. Three different use cases dealing with capturing, modelling and analysis of spatial information are studied. In that process, the main emphasis is on the added value and the benefits of geo-information fusion. One can speak of an “added value” if the informational content can only be derived by the combination of information from different sources, meaning that it cannot be derived from one source individually. Another goal of this thesis is the prototypical integration of the fusion approach in spatial data infrastructures (SDIs) to increase the interoperability of the developed methods. By doing so, the fusion can be provided (e.g. over the internet) and used by a multitude of users and developers. Above that, the integration is of high importance regarding systems and concepts like the Global Earth Observation System of Systems (GEOSS), the INSPIRE directive for Europe or the European monitoring system Copernicus. The results and findings of this thesis can be seen as the first advances and can be used for further research and studies in the field of geo-information fusion which will gain further importance and relevance for all spatial questions in the future.