Visualizing Uncertainty In Environmental Work-flows And Sensor Streams Karthikeyan Bollu Ganesh and Patrick Mau´e Institute for Geoinformatics (IFGI), University of Muenster, D-48151 Muenster, Germany {karthikeyan,pajoma}@uni-muenster.de Abstract. Environmental data and models are uncertain by nature. The lack of knowledge about, for example, the magnitude of potential measurement errors may lead to unforeseen consequences. This makes it difficult to assess the data’s or model’s usefulness for critical applications. We present an approach for the visualization of uncertainty coming from in-situ environmental sensors. The visualization component is part of a Web-enabled environmental modelling platform which also supports the specification of processing workflows. The concept of uncertainty and means for its encoding as part of the environmental data are introduced. The individual components in the processing workflows propagate and update the uncertainty information. We also explain how the uncertainty in the original sensor data has been identified, and how the visualization component has been implemented. Keywords: Uncertainty,Uncertainty Visualization, Environmental Work- flows 1 Introduction The on-going implementation of the European INSPIRE directive facilitated the access to geographic information on the Web. Embedded in Spatial Data Infras- tructures (SDI), geospatial Web services provide means to access, process, and visualize spatial data. Interoperability between different Web services is to a cer- tain degree ensured by the standards set by the Open Geospatial Consortium. The standards also enable the direct integration into local geospatial applica- tions. But there has been only limited uptake by the environmental modelling community. The concept of a Shared Environmental Information System (SEIS) has been recently introduced to address this issue [2]. The published SEIS prin- ciples aim to facilitate access to environmental information for public authorities and the general public. This calls for new ways of how to publish environmental services, and how to present the resulting information to also non-ICT skilled end-users. Investigating the requirements for environmental services infrastruc- tures, including the execution of environmental services via standard runtime engines for service work-flows and the Web-enabled visualization through en-