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Info Catalog ( Spatial extensions in MySQL ( Spatial extensions in MySQL ( OpenGIS geometry model
 18.1 Introduction
 MySQL implements spatial extensions following the specification of the
 `Open GIS Consortium' (OGC). This is an international consortium of
 more than 250 companies, agencies, and universities participating in
 the development of publicly available conceptual solutions that can be
 useful with all kinds of applications that manage spatial data.  The
 OGC maintains a Web site at `'.
 In 1997, the Open GIS Consortium published the `OpenGIS (R) Simple
 Features Specifications For SQL', a document that proposes several
 conceptual ways for extending an SQL RDBMS to support spatial data.
 This specification is available from the Open GIS Web site at
 `'.  It contains additional
 information relevant to this chapter.
 MySQL implements a subset of the *SQL with Geometry Types* environment
 proposed by OGC.  This term refers to an SQL environment that has been
 extended with a set of geometry types. A geometry-valued SQL column is
 implemented as a column that has a geometry type. The specifications
 describe a set of SQL geometry types, as well as functions on those
 types to create and analyze geometry values.
 A *geographic feature* is anything in the world that has a location.  A
 feature can be:
    * An entity. For example, a mountain, a pond, a city.
    * A space. For example, a postcode area, the tropics.
    * A definable location. For example, a crossroad, as a particular
      place where two streets intersect.
 You can also find documents that use the term *geospatial feature* to
 refer to geographic features.
 *Geometry* is another word that denotes a geographic feature.
 Originally the word *geometry* meant measurement of the earth.  Another
 meaning comes from cartography, referring to the geometric features
 that cartographers use to map the world.
 This chapter uses all of these terms synonymously: *geographic
 feature*, *geospatial feature*, *feature*, or *geometry*.  The term
 most commonly used here is *geometry*.
 Let's define a *geometry* as _a point or an aggregate of points
 representing anything in the world that has a location_.
Info Catalog ( Spatial extensions in MySQL ( Spatial extensions in MySQL ( OpenGIS geometry model
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