Voronoi-based region approximation for geographical information retrieval with gazetteers

Abstract

Abstract. Gazeteers and geographical thesauri can be regarded as parsimonious spatial models that associate geographical location with place names and encode some semantic relations between the names. They are of particular value in processing information retrieval requests in which the user employs place names to specify geographical context. Typically the geometric locational data in a gazetteer are con ned to a simple footprint in the form of a centroid or a minimum bounding rectangle, both of which can be used to link to a map but are of limited value in determining spatial relationships. Here we describe a Voronoi diagram method for generating approximate regional extents from sets of centroids that are respectively inside and external to a region. The resulting approximations provide measures of areal extent and can be used to assist in answering geographical queries by evaluating spatial relationships such as distance, direction and common boundary length. Preliminary experimental evaluations of the method have been performed in the context of a semantic modelling system that combines the centroid data with hierarchical and adjacency relations between the associated place names.

Acquisition of Vernacular Place Names from Web Sources

“…Alani et al [1] and Arampatzis et al [2] describe methods based on Voronoi diagrams and Delaunay triangulations to determine approximate boundaries of regions represented by sets of points.…”

What Is the Region Occupied by a Set of Points?

“…However, one situation where we may be able to make a more informed choice about how far the footprint should extend beyond the points is when we have additional information about points which are to be excluded from the region. This allows one to make use of the methods of [6] and [7] which are briefly discussed in the next section.…”

“…In the context of GIS, a method based on Voronoi diagrams has been suggested by [6]. This is applicable where the points S are representative localities within some region R, and in addition we are given a set S of points known to lie outside R. In this Dynamic Spatial Approximation Method (DSAM), the Voronoi diagram of S ∪ S is constructed, and an approximation to region R is derived as the union of the Voronoi cells containing members of S. This approximation to R is a kind of footprint, typically non-convex, of the set S. It is, of course, an extended footprint.…”

“…The convex hull is polygonal. 6. The boundary of the convex hull is a Jordan curve (unless the points are collinear).…”

A Utility Centered Approach for Evaluating and Optimizing Geo-Tagging

“…Applying all relations available at GeoNames will yield even more accurate performance metrics. More sophisticated approaches might even implement geographic reasoning (e.g., through Voronoi polygons (Alani et al, 2001) or spatial indexes based on uniform grids (Riekert, 2002)). …”