ST_AsKML-ApsaraDB RDS(RDS)-阿里云帮助中心

Returns the Keyhole Markup Language (KML) element for a geometry or geography object.

Syntax

text ST_AsKML(geometry geom, integer maxdecimaldigits=15);
text ST_AsKML(geography geog, integer maxdecimaldigits=15);
text ST_AsKML(integer version, geometry geom, integer maxdecimaldigits=15, text nprefix=NULL);
text ST_AsKML(integer version, geography geog, integer maxdecimaldigits=15, text nprefix=NULL);

Parameters

Parameter	Description	Default
`geom`	The geometry object to convert to KML.	—
`geog`	The geography object to convert to KML.	—
`maxdecimaldigits`	The maximum number of decimal places in the output coordinates.	`15`
`version`	The KML version. `2` uses GML 2.1.2; `3` uses GML 3.1.1.	`2`
`nprefix`	The namespace prefix. Pass a custom string to qualify KML element names.	`NULL`

Usage notes

ST_AsKML supports 3D objects and preserves the z-coordinate of the input geometry.

Examples

Convert a 2D polygon

SELECT ST_AsKML(ST_GeomFromText('POLYGON((1 1,1 2,2 2,2 1,1 1))',4326));

Output:

                           st_askml
---------------------------------------------------------------
 <Polygon><outerBoundaryIs>
     <LinearRing><coordinates>1,1 1,2 2,.2 2,1 1,1</coordinates>
  </LinearRing></outerBoundaryIs>
 </Polygon>
(1 row)

Convert a 3D linestring

SELECT ST_AsKML(ST_GeomFromText('LINESTRING(1 2 3, 4 5 6)',4326));

Use a namespace prefix

SELECT ST_AsKML(2, ST_GeomFromText('POLYGON((1 1,1 2,2 2,2 1,1 1))',4326), 15, 'kml');

What's next

ST_AsGML — export geometry as Geography Markup Language (GML), the format underlying KML
ST_AsGeoJSON — export geometry as GeoJSON, the standard format for web mapping APIs