Since location is an important part of context, the management of spatial information is important for many context-aware applications, e.g. the position or the extent of users, sensors, rooms or buildings. Coordinates always have a coordinate system (CS) associated to them. Numerous CSs exist and a lot of them are commonly used, thus conversion becomes a necessity. We introduce a library that implements the OGC Simple Feature Specification and can dynamically cope with different CSs, enabling interoperability between applications, middleware components and data providers. We illustrate functions and features, describe a common CS determination algorithm and point out our lessons learned: avoid transformations, use existing standards but dare to extend them when needed.