A measure of shape compactness is a numerical quantity representing the degree to which a shape is compact. Ways to provide an accurate measure have been given great attention due to its application in a broad range of GIS problems, such as detecting clustering patterns from remote-sensing images, understanding urban sprawl, and redrawing electoral districts to avoid gerrymandering. In this article, we propose an effective and efficient approach to computing shape compactness based on the moment of inertia (MI), a well-known concept in physics. The mathematical framework and the computer implementation for both raster and vector models are discussed in detail. In addition to computing compactness for a single shape, we propose a computational method that is capable of calculating the variations in compactness as a shape grows or shrinks, which is a typical application found in regionalization problems. We conducted a number of experiments that demonstrate the superiority of the MI over the popular isoperimetric quotient approach in terms of (1) computational efficiency; (2) tolerance of positional uncertainty and irregular boundaries; (3) ability to handle shapes with holes and multiple parts; and (4) applicability and efficacy in districting/zonation/regionalization problems.
Digital gazetteers provide information on named features, linking the feature's name with its location and its type. They have been growing in importance recently as the basis of a range of services, including way-finding, georeferencing, and intelligence. This introduction to the following collection of five research papers expands on contemporary applications of digital gazetteers, explores the issues associated with each of the three types of information, and defines three broad areas of research: the components of gazetteers; the process by which places are named and evolve; and the issues of interoperability between digital gazetteers. Each area is represented by at least one paper in the collection. Digital gazetteers increasingly form the interface between the informal discourse of humans and the formal world of geographic information science.Keywords: Digital gazetteer; Place names; Interoperability; Conflation BackgroundThe building and application of digital gazetteers, which organize knowledge and details about named places, is a growing area of research that necessarily involves cross-domain issues from fields such as spatial cognition, geographic information science, social history, computer science, and geographic information retrieval. Gazetteer-based services are being developed and deployed in such specific fields as public health, natural history data management, cultural history, and automated georeferencing of text (geoparsing). Gazetteers started out as reference books that documented the names and accepted spellings of places (toponyms)-for example, standardized place name lists for newspaper articles. In these gazetteers, contextual and descriptive information about the places was included as needed. Some of these developed into sources of authoritative names which were used widely, and the organizations that prepared them, mostly for governmental purposes, were and are known as toponymic authorities. Such authorities exist for many countries, as well as for constituent states, provinces, and even local areas. In the US, for example, the Board on Geographic Names was established in 1890 with the objective of standardizing the use of place names. Thus, the emphasis in all of these efforts was on the naming of places.When computerized mapping software emerged, place names were treated as a names layer, often structured as a table containing place names that was linked to named features for the purposes of labelling. In this case, the emphasis is on representing the geographic location rather than on the naming. In the 1990s, research projects such as the Alexandria Digital Library (ADL) project at the *Corresponding author. Email: good@geog.ucsb.edu Vol. 22, No. 10, October 2008, 1039-1044 University of California, Santa Barbara demonstrated the key role that gazetteers play in geographically enabled information management and retrieval systems. It became clear that gazetteers play a vital role in information systems because they encode relationships not only between place names and geograp...
Wikipedia is a free encyclopedia that anyone can edit and a popular example of usergenerated content that includes volunteered geographic information (VGI). In this article, we present three main contributions: (1) a spatial data model and collection methods to study VGI in systems that may not explicitly support geographic data;(2) quantitative methods for measuring distance between online authors and articles; and (3) empirically calibrated results from a gravity model of the role of distance in VGI production. To model spatial processes of VGI contributors, we use an invariant exponential gravity model based on article and author proximity. We define a proximity metric called a 'signature distance' as a weighted average distance between an article and each of its authors, and we estimate the location of 2.8 million anonymous authors through IP geolocation. Our study collects empirical data directly from 21 language-specific Wikipedia databases, spanning 7 years of contributions (2001)(2002)(2003)(2004)(2005)(2006)(2007)(2008) to nearly 1 million geotagged articles. We find empirical evidence that the spatial processes of anonymous contributors fit an exponential distance decay model. Our results are consistent with the prior results on information diffusion as a spatial process, but run counter to theories that a globalized Internet neutralizes distance as a determinant of social behaviors.
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