Place names are often used to describe and to enquire about geographical information.
It is common for users to employ vernacular names that have vague spatial extent and which do not correspond to the official and administrative place name terminology
recorded within typical gazetteers. There is a need therefore to enrich gazetteers with knowledge of such vague places and hence improve the quality of place name-based
information retrieval. Here we describe a method for modelling vague places using knowledge harvested from web pages. It is found that vague place names are frequently
accompanied in text by the names of more precise co-located places that lie within the extent of the target vague place. Density surface modelling of the frequency of co-
occurrence of such names provides an effective method of representing the inherent uncertainty of the extent of the vague place while also enabling approximate crisp
boundaries to be derived from contours if required. The method is evaluated using both precise and vague places. The use of the resulting approximate boundaries is
demonstrated using an experimental geographical search engine.