Over the past years user-generated content has gained increasing importance in the area of geographic information science. Private citizens collect environmental data of their neighborhoods and publish it on the web. The wide success of volunteered geographic information relies on the simplicity of such systems. We propose to use sketch maps as a visual user interface, because sketch maps are intuitive, easy to produce for humans and commonly used in human-to-human communication. Sketch maps reflect users' spatial knowledge that is based on observations rather than on measurements. However, sketch maps, often considered as externalizations of cognitive maps, are distorted, schematized, incomplete, and generalized. Processing spatial information from sketch maps must therefore account for these cognitive aspects. In this paper, we suggest a set of qualitative spatial aspects that should be captured in representations of sketch maps and give empirical evidence that these spatial aspects are robust against typical schematizations and distortions in human spatial knowledge. We propose several existing qualitative spatial calculi to formally represent the spatial aspects, suggest appropriate methods for applying them, and evaluate the proposed representations for alignment of sketch maps and metric maps.