Mobile computer systems equipped with wireless communication and sensor technology - such as mobile phones with cameras - have become widely available. Context information, for example the userœôòùs current location or their physical environment, plays an increasingly important role in simplifying the interaction between users and such mobile information systems. A generic framework for federating heterogeneous spatial context models is briefly described. The federated information serves as basis for the visualization of spatially referenced data. Visualization challenges include efficient rendering on mobile devices, automatic adaptation of visualization techniques to context information, as well as consideration of the quality of context in the form of uncertainty visualization.