This topic describes the ST_AsText function. This function returns the Well-Known Text (WKT) string that represents a geometry object or a geography object. The WKT string that is returned does not contain spatial reference identifier (SRID) metadata.
Syntax
text ST_AsText(geometry g1);
text ST_AsText(geometry g1 , integer maxdecimaldigits);
text ST_AsText(geography g1);
text ST_AsText(geography g1 , integer maxdecimaldigits); Parameters
| Parameter | Description |
|---|---|
| g1 | The geometry object or geography object whose WKT representation you want to obtain. |
| maxdecimaldigits | The maximum number of decimal places that you want to retain. Default value: 15. |
Description
- If you want to obtain a WKT string that contains an SRID, we recommend that you use the ST_AsEWKT function.
- The WKT format cannot ensure precision. If you want to prevent floating-point numbers of a specific decision from being truncated, we recommend that you use the ST_AsBinary function or the ST_AsEWKB function.
Examples
- Obtain a WKT string with the default parameter settings retained.
SELECT ST_AsText(ST_GeomFromText('POINT(116 40)',4326)); st_astext --------------- POINT(116 40) (1 row) - Obtain a WKT string with the number of decimal places specified.
SELECT ST_AsText(ST_GeomFromText('POINT(116.112 40.412)',4326),2); st_astext --------------------- POINT(116.11 40.41) (1 row)