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-- and render the extended text representation of that geometrySELECT ST_SetSRID(ST_Extent(the_geom),2249) as bextent FROM sometable;

bextent--------------------------------------------------------------------------------SRID=2249;POLYGON((739651.875 2908247.25,739651.875 2970042.75,794875.8125 2970042.75,794875.8125 2908247.25,739651.875 2908247.25))

See Also

ST_AsEWKT, ST_Extent3D, ST_SetSRID, ST_SRID

7.12.7 ST_Extent3D

Name

ST_Extent3D – an aggregate function that returns the box3D bounding box that bounds rows of geometries.

Synopsis

box3d ST_Extent3D(geometry set geomfield);

Description

ST_Extent3D returns a box3d (includes Z coordinate) bounding box that encloses a set of geometries. The ST_Extent3D functionis an "aggregate" function in the terminology of SQL. That means that it operates on lists of data, in the same way the SUM()and AVG() functions do.

Since it returns a bounding box, the spatial Units are in the units of the spatial reference system in use denoted by the SRID

NoteSince ST_Extent3D returns a bounding box, the SRID meta-data is lost. Use ST_SetSRID to force it back into ageometry with SRID meta data. The coordinates are in the units of the spatial ref of the orginal geometries.

This function supports 3d and will not drop the z-index.

This method supports Circular Strings and Curves

Examples

SELECT ST_Extent3D(foo.the_geom) As b3extentFROM (SELECT ST_MakePoint(x,y,z) As the_geomFROM generate_series(1,3) As xCROSS JOIN generate_series(1,2) As yCROSS JOIN generate_series(0,2) As Z) As foo;b3extent

--------------------BOX3D(1 1 0,3 2 2)

--Get the extent of various elevated circular strings

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SELECT ST_Extent3D(foo.the_geom) As b3extentFROM (SELECT ST_Translate(ST_Force_3DZ(ST_LineToCurve(ST_Buffer(ST_MakePoint(x,y),1))),0,0, ←↩

z) As the_geomFROM generate_series(1,3) As xCROSS JOIN generate_series(1,2) As yCROSS JOIN generate_series(0,2) As Z) As foo;

b3extent--------------------BOX3D(1 0 0,4 2 2)

See Also

ST_Extent, ST_Force_3DZ

7.12.8 Find_SRID

Name

Find_SRID – The syntax is find_srid(<db/schema>, <table>, <column>) and the function returns the integer SRID of the specifiedcolumn by searching through the GEOMETRY_COLUMNS table.

Synopsis

integer Find_SRID(varchar a_schema_name, varchar a_table_name, varchar a_geomfield_name);

Description

The syntax is find_srid(<db/schema>, <table>, <column>) and the function returns the integer SRID of the specified column bysearching through the GEOMETRY_COLUMNS table. If the geometry column has not been properly added with the AddGe-ometryColumns() function, this function will not work either.

Examples

SELECT Find_SRID(’public’, ’tiger_us_state_2007’, ’the_geom_4269’);find_srid----------4269

See Also

ST_SRID

7.12.9 ST_Mem_Size

Name

ST_Mem_Size – Returns the amount of space (in bytes) the geometry takes.