We stress the importance of requirements engineering (RE) for the development of large scale software in general and for GIS-applications in particular. RE analyses the problem domain and de nes the requirements upon the software to be developed. We discuss two GIS-application scenarios, the so-called topological scenario and the network scenario, we frequently encountered in real life projects. Our investigations reveal that conventional RE-methods like e.g. Coad/Yourdon's Object-Oriented Analysis (OOA) are not capable to model GIS-speci c requirements appropriately. To overcome the de ciencies of conventional OOA we introduce GeoOOA which complements OOA by suitable geoprimitives and allows for a more adequate treatment of GISspeci c requirements. We provide GeoOOA-models of a broadcasting and a power supply domain as rst validation steps for the usefulness of GeoOOA.