Qualitative Representations of Extended Spatial Objects in Sketch Maps

With the advent of Volunteered Geographic Information (VGI) the amount and accessibility of the spatial information such as sketched information produced by layperson increased drastically. In many geo-spatial applications, sketch maps are considered an intuitive user interaction modality. In sketch maps, the spatial objects and their relationships enable users to communicate and reason about their actions in the physical environment. The information people draw in sketch maps are distorted, schematized, and incomplete. Thus, processing spatial information from sketch maps and making it available in information systems requires suitable representation and alignment approaches. As typically only qualitative relations are preserved in sketch maps, performing alignment and matching with geo-referenced maps on qualitative level has been suggested. In this study, we analyzed different qualitative representations and proposed a set of plausible representations to formalize the topology and orientation information of extended objects in sketch maps. Using the proposed representations, the qualitative relations among depicted objects are extracted in the form of Qualitative Constraint Networks (QCNs). Next, the obtained QCNs from the sketch maps are compared with QCN derived from the metric maps to determine the degree to which the information is identical. If the representations are suitable, the QCNs of both maps should be identical to a high degree. The consistency of obtaining QCNs allows the alignment and integration of spatial information from sketch maps into Geographic Information Systems (GISs).