Gazetteers

Historically, gazetteers served as indexes to place names on map sheets or maps in atlases. A person could look up a place name in the gazetteer and get a page or map sheet number along with a grid reference (e.g., E4) and be able to find it on a map. The gazetteer thus served an important role in information retrieval. In its digital incarnation, a gazetteer serves a similar role as an aid for information retrieval.

One of the most widely used and known gazetteers in the United States is the Geographic Names Information System (GNIS). This digital gazetteer is maintained by the U.S. Geological Survey along with the U.S. Board on Geographic Names. As of December 21, 2009, there were 2,123,538 entries in GNIS covering more than 60 different feature classes. An entry in this gazetteer includes an official place or feature name; alternate feature names; the feature class; the state and county where it is located; the name of a topographic map on which the feature occurs; its latitude, longitude, and elevation; and an entry date.

Recently, the International Organization for Standardization (ISO) 19112 and the Open Geospatial Consortium defined content standards for digital gazetteers and interoperable gazetteer services such that gazetteer services can be executed over the Web. Standard contents for a gazetteer include an official place name; alternate names, including historical or multilingual names; a feature type; and a spatial position most often specified as a point with two-dimensional (2D) or 3D coordinates.

In their digital form, gazetteers are extremely useful for a range of geospatial search functions. Their value lies in their ability to translate between different location representation systems. Locations can be represented textually by place names and addresses or numerically by 2D or 3D coordinates in different spatial reference systems. A person can thus query a gazetteer with a coordinate range and retrieve place names contained within that range. Alternately, a person can query the gazetteer with a place name and retrieve a coordinate location or description for the place name. Location-based services may employ gazetteers to translate a person's coordinate location obtained [Page 1186]by global positioning systems to an address location or to return nearby place names or features of interest. Geospatial information on the Web may have many different location reference forms, so comprehensive searches of the Web for geospatial information will rely more and more on gazetteers to serve as the translators between these diverse reference forms. Suppose a person searches for water-quality data on Sebago Lake. Such data may be referenced using spatial coordinates, or place names, including place names with misspellings. The gazetteer can be used to expand the search from the place name the user enters to alternate names and coordinate descriptions such that the user has a greater chance of finding all the pertinent information.

Gazetteers can also serve as the geographic knowledge source to support automated text processing, spatial grounding of text descriptions, data mining, and information integration. For example, by processing a news article using a gazetteer, one could translate any place name references to coordinate references, plot these on maps, and compare these with place locations in other new articles and with other information sources.

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