PostGIS

ST_AsText

Prev

8.9.1. Well-Known Text (WKT)

Next

Name

ST_AsText — Return the Well-Known Text (WKT) representation of the geometry/geography without SRID metadata.

Synopsis

text +`*`+ST_AsText*(`geometry `g1`)`;

text +`*`+ST_AsText*(`geometry `g1, integer maxdecimaldigits = 15`)`;

text +`*`+ST_AsText*(`geography `g1`)`;

text +`*`+ST_AsText*(`geography `g1, integer maxdecimaldigits = 15`)`;

Description

Returns the OGC Well-Known Text (WKT) representation of the geometry/geography. The optional `maxdecimaldigits` argument may be used to limit the number of digits after the decimal point in output ordinates (defaults to 15).

To perform the inverse conversion of WKT representation to PostGIS geometry use ST_GeomFromText.

Note

The standard OGC WKT representation does not include the SRID. To include the SRID as part of the output representation, use the non-standard PostGIS function ST_AsEWKT

Warning

The textual representation of numbers in WKT may not maintain full floating-point precision. To ensure full accuracy for data storage or transport it is best to use Well-Known Binary (WKB) format (see ST_AsBinary and `maxdecimaldigits`).

Warning

Using the `maxdecimaldigits` parameter can cause output geometry to become invalid. To avoid this use ST_ReducePrecision with a suitable gridsize first.

Availability: 1.5 - support for geography was introduced.

Enhanced: 2.5 - optional parameter precision introduced.

check This method implements the SQL/MM specification. SQL-MM 3: 5.1.25

check This method supports Circular Strings and Curves

Examples

SELECT ST_AsText('01030000000100000005000000000000000000
000000000000000000000000000000000000000000000000
F03F000000000000F03F000000000000F03F000000000000F03
F000000000000000000000000000000000000000000000000');

    st_astext
--------------------------------
 POLYGON((0 0,0 1,1 1,1 0,0 0))

Full precision output is the default.

SELECT ST_AsText('POINT(111.1111111 1.1111111)'));
    st_astext
------------------------------
 POINT(111.1111111 1.1111111)

The `maxdecimaldigits` argument can be used to limit output precision.

SELECT ST_AsText('POINT(111.1111111 1.1111111)'), 2);
    st_astext
--------------------
 POINT(111.11 1.11)

See Also