Well Known Text

The Well Known Text format (hereafter WKT) provides a text representation of a geometric shape. It can be used to:

• Build instances of various shapes (e.g., using ST_MakePolygon on a Linestring).
• Convert existing shapes to a text representation for ease of reading.

Each shape in WKT has a tag which says what it is, usually followed by a list of coordinates. For example, here are some common tags:

• POINT(...)
• LINESTRING(...)
• POLYGON((...))

WKT is technically case insensitive, but is sometimes displayed using “CamelCase” for easier reading. For example, one can represent a MultiPolygon as either of:

• MULTIPOLYGON(...)
• MultiPolygon(...)

When a shape is made up of homogeneous subcomponents, such as a polygon made up of various points, the subcomponents do not need to have their own tags. For example: LINESTRING(-88.243385 40.116421, -87.906471 43.038902, -95.992775 36.153980) Shapes expressed in WKT can have an SRID prepended to the shape and followed by a semicolon, in the form SRID=123;TAG(...). The format is known as Extended Well Known Text (EWKT); it is the same as WKT, with an SRID representation prepended to the data structure. For example, below is a polygon representing a geometry that uses SRID 4326, which is used to represent latitude and longitude coordinates on the Earth as defined in the WGS84 standard: SRID=4326;POLYGON((-87.906471 43.038902, -95.992775 36.153980, -75.704722 36.076944, -87.906471 43.038902)) For more detailed information about the Well Known Text format, see the OGC specification for WKT.

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See also

• Spatial Data Overview
• Spatial indexes
• Spatial and GIS Glossary of Terms
• Geographic information — Well-known text representation of coordinate reference systems
• OpenGIS Implementation Specification for Geographic information - Simple feature access - Part 1: Common architecture
• Well known binary
• GeoJSON
• SRID 4326 - longitude and latitude
• Introducing Distributed Spatial Data in CockroachDB (blog post)