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Constructing geography Instances

You can construct instances of the geography data type by inputting data either in Well-Known Text (WKT) or Well-Known Binary (WKB) format.

The geography data type provides several built-in methods that generate a geography from the Open Geospatial Consortium (OGC) WKT representation. The WKT standard is a text string that allows geography data to be exchanged in textual form.

To construct any type of geography instance from WKT input

To construct a geography Point instance from WKT input

To construct a geography MultiPoint instance from WKT input

To construct a geography LineString instance from WKT input

To construct a geography MultiLineString instance from WKT input

To construct a geography Polygon instance from WKT input

To construct a geography MultiPolygon instance from WKT input

To construct a geography GeometryCollection instance from WKT input

WKB is a binary format specified by the OGC that permits geography data to be exchanged between a client application and an SQL database. The following functions accept WKB input to construct geography instances:

To construct any type of geography instance from WKB input

To construct a geography Point instance from WKB input

To construct a geography MultiPoint instance from WKB input

To construct a geography LineString instance from WKB input

To construct a geography MultiLineString instance from WKB input

To construct a geography Polygon instance from WKB input

To construct a geography MultiPolygon instance from WKB input

To construct a geography GeometryCollection instance from WKB input

The geography data type provides a method that generates a geography instance from GML, an XML representation of a geography instance. SQL Server supports a subset of GML.

For more information on Geography Markup Language, see the OGC Specification: OGC Specifications, Geography Markup Language.

To construct any type of geography instance from GML input

GeomFromGML (geography Data Type)

You can use the following methods to return either the WKT or WKB format of a geography instance:

To return the WKT representation of a geography instance

STAsText (geography Data Type)

ToString (geography Data Type)

To return the WKT representation of a geography instance including any Z and M values

AsTextZM (geography Data Type)

To return the WKB representation of a geography instance

STAsBinary (geography Data Type)

To return a GML representation of a geography instance

AsGml (geography Data Type)

Once a geography instance is constructed, you can use the following methods to return the instance type, or if it is a GeometryCollection instance, return a specific geography instance.

To return the instance type of a geography

STGeometryType (geography Data Type)

To determine if a geography is a given instance type

InstanceOf (geometry Data Type)

To determine if a geography instance is well-formed for its instance type

STNumGeometries (geography Data Type)

To return a specific geography in a GeometryCollection instance

STGeometryN (geography Data Type)

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