Today, spatial data infrastructures consist mainly of GI services that offer base functionalities such as searching, accessing, and visualising geographic data. While this makes it easier to use geographic data, GI services cannot yet be combined to provide analyses based on specific user requirements. For this, additional GI services and mechanisms for orchestrating them are required. Standards in this area are currently under development, e.g. the OGC discussion paper on Web Processing Services (WPS). In this paper, we present the design and implementation of a geoprocessing service based on the WPS specification. In the conclusion, we highlight the problems encountered as well as open research questions and possible next steps in the area of distributed geoprocessing.