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<section xmlns:xlink="http://www.w3.org/1999/xlink" xmlns="http://docbook.org/ns/docbook" version="5.0" xml:id="Geometry_Constructors">
	  <title>Geometry Constructors</title>

	<refentry xml:id="ST_Collect">
	  <refnamediv>
		<refname>ST_Collect</refname>
		<refpurpose>Creates a GeometryCollection or Multi* geometry from a set of geometries.</refpurpose>
	  </refnamediv>

	  <refsynopsisdiv>
		<funcsynopsis>
			<funcprototype>
				<funcdef>geometry <function>ST_Collect</function></funcdef>
					<paramdef><type>geometry</type> <parameter>g1</parameter></paramdef>
					<paramdef><type>geometry</type> <parameter>g2</parameter></paramdef>
			</funcprototype>
			<funcprototype>
				<funcdef>geometry <function>ST_Collect</function></funcdef>
					<paramdef><type>geometry[]</type> <parameter>g1_array</parameter></paramdef>
			</funcprototype>
			<funcprototype>
				<funcdef>geometry <function>ST_Collect</function></funcdef>
					<paramdef><type>geometry set</type> <parameter>g1field</parameter></paramdef>
			</funcprototype>
		</funcsynopsis>
	  </refsynopsisdiv>

	  <refsection>
		<title>Description</title>
		<para> Collects geometries into a geometry collection.
			The result is either a Multi* or a
			GeometryCollection, depending on whether the input geometries have the same or different types
			(homogeneous or heterogeneous).
			The input geometries are left unchanged within the collection.
			</para>

		<para><emphasis role="bold">Variant 1:</emphasis> accepts two input geometries</para>
		<para><emphasis role="bold">Variant 2:</emphasis> accepts an array of geometries</para>
		<para><emphasis role="bold">Variant 3:</emphasis> aggregate function accepting a rowset of geometries.</para>

		<note><para>
		If any of the input geometries are collections (Multi* or GeometryCollection)
		ST_Collect returns a GeometryCollection (since that is the only type
		which can contain nested collections).
		To prevent this, use <xref linkend="ST_Dump"/> in a subquery to expand the
		input collections to their atomic elements (see example below).
		</para></note>

		<note><para>ST_Collect and <xref linkend="ST_Union"/> appear similar, but in fact operate quite differently.
		ST_Collect aggregates geometries into a collection without changing them in any way.
		ST_Union geometrically merges geometries where they overlap,
		and splits linestrings at intersections.
		It may return single geometries when it dissolves boundaries.
		</para></note>

		<para role="availability" conformance="1.4.0">Availability: 1.4.0 -  ST_Collect(geomarray) was introduced. ST_Collect was enhanced to handle more geometries faster.</para>
		<para>&Z_support;</para>
		<para>&curve_support;</para>
	  </refsection>

	  <refsection>
		<title>Examples - Two-input variant</title>
		<para>Collect 2D points.</para>
<programlisting>
SELECT ST_AsText( ST_Collect( ST_GeomFromText('POINT(1 2)'),
	ST_GeomFromText('POINT(-2 3)') ));

st_astext
----------
MULTIPOINT((1 2),(-2 3))
</programlisting>

<para>Collect 3D points.</para>
<programlisting>
SELECT ST_AsEWKT( ST_Collect( ST_GeomFromEWKT('POINT(1 2 3)'),
		ST_GeomFromEWKT('POINT(1 2 4)') ) );

		st_asewkt
-------------------------
 MULTIPOINT(1 2 3,1 2 4)
 </programlisting>

<para>Collect curves.</para>
 <programlisting>
SELECT ST_AsText( ST_Collect( 'CIRCULARSTRING(220268 150415,220227 150505,220227 150406)',
		'CIRCULARSTRING(220227 150406,2220227 150407,220227 150406)'));

		st_astext
------------------------------------------------------------------------------------
MULTICURVE(CIRCULARSTRING(220268 150415,220227 150505,220227 150406),
 CIRCULARSTRING(220227 150406,2220227 150407,220227 150406))
</programlisting>
		</refsection>
		<refsection>
<title>Examples - Array variant</title>
<para>Using an array constructor for a subquery.</para>
<programlisting>
SELECT ST_Collect( ARRAY( SELECT geom FROM sometable ) );
</programlisting>
<para>Using an array constructor for values.</para>
<programlisting>
SELECT ST_AsText(  ST_Collect(
		ARRAY[ ST_GeomFromText('LINESTRING(1 2, 3 4)'),
			ST_GeomFromText('LINESTRING(3 4, 4 5)') ] )) As wktcollect;

--wkt collect --
MULTILINESTRING((1 2,3 4),(3 4,4 5))
</programlisting>
		</refsection>
		<refsection>
		<title>Examples - Aggregate variant</title>
		<para>Creating multiple collections by grouping geometries in a table.</para>
<programlisting>
SELECT stusps, ST_Collect(f.geom) as geom
	 FROM (SELECT stusps, (ST_Dump(geom)).geom As geom
				FROM
				somestatetable ) As f
	GROUP BY stusps
</programlisting>

	  </refsection>
	  <refsection>
		<title>See Also</title>
		<para><xref linkend="ST_Dump"/>, <xref linkend="ST_Union"/></para>
	  </refsection>
	</refentry>

	<refentry xml:id="ST_LineFromMultiPoint">
	  <refnamediv>
		<refname>ST_LineFromMultiPoint</refname>

		<refpurpose>Creates a LineString from a MultiPoint geometry.</refpurpose>
	  </refnamediv>

	  <refsynopsisdiv>
		<funcsynopsis>
		  <funcprototype>
			<funcdef>geometry <function>ST_LineFromMultiPoint</function></funcdef>
			<paramdef><type>geometry </type> <parameter>aMultiPoint</parameter></paramdef>
		  </funcprototype>
		</funcsynopsis>
	  </refsynopsisdiv>

	  <refsection>
		<title>Description</title>

		<para>Creates a LineString from a MultiPoint geometry.</para>

		<para>Use <xref linkend="ST_MakeLine"/> to create lines from Point or LineString inputs.</para>

		<para>&Z_support;</para>

	  </refsection>

	  <refsection>
		<title>Examples</title>
		<para>Create a 3D line string from a 3D MultiPoint</para>
		<programlisting>
SELECT ST_AsEWKT(  ST_LineFromMultiPoint('MULTIPOINT(1 2 3, 4 5 6, 7 8 9)')  ));

--result--
LINESTRING(1 2 3,4 5 6,7 8 9)
</programlisting>
	  </refsection>

	  <!-- Optionally add a "See Also" section -->
	  <refsection>
		<title>See Also</title>

		<para><xref linkend="ST_AsEWKT"/>, <xref linkend="ST_MakeLine"/></para>
	  </refsection>
	</refentry>

	<refentry xml:id="ST_MakeEnvelope">
		<refnamediv>
		<refname>ST_MakeEnvelope</refname>

		<refpurpose>Creates a rectangular Polygon from minimum and maximum coordinates.</refpurpose>
		</refnamediv>

		<refsynopsisdiv>
		<funcsynopsis>
		  <funcprototype>
			<funcdef>geometry <function>ST_MakeEnvelope</function></funcdef>
			<paramdef><type>float</type> <parameter>xmin</parameter></paramdef>
			<paramdef><type>float</type> <parameter>ymin</parameter></paramdef>
			<paramdef><type>float</type> <parameter>xmax</parameter></paramdef>
			<paramdef><type>float</type> <parameter>ymax</parameter></paramdef>
			<paramdef choice="opt"><type>integer</type> <parameter>srid=unknown</parameter></paramdef>
		  </funcprototype>
		 </funcsynopsis>
		</refsynopsisdiv>

		<refsection>
			<title>Description</title>

			<para>Creates a rectangular Polygon from the minimum and maximum values for X and Y.
			Input values must be in the spatial reference system specified by the SRID.
			If no SRID is specified the unknown spatial reference system (SRID 0) is used.</para>

			<para role="availability" conformance="1.5">Availability: 1.5</para>
			<para role="enhanced" conformance="2.0">Enhanced: 2.0: Ability to specify an envelope without specifying an SRID was introduced.</para>

		</refsection>

		<refsection>
		<title>Example: Building a bounding box polygon</title>
		 <programlisting>
SELECT ST_AsText( ST_MakeEnvelope(10, 10, 11, 11, 4326) );

st_asewkt
-----------
POLYGON((10 10, 10 11, 11 11, 11 10, 10 10))
</programlisting>
		</refsection>
		<refsection>
			<title>See Also</title>
			<para><xref linkend="ST_MakePoint"/>, <xref linkend="ST_MakeLine"/>, <xref linkend="ST_MakePolygon"/>, <xref linkend="ST_TileEnvelope"/></para>
		</refsection>
	</refentry>

	<refentry xml:id="ST_MakeLine">
		<refnamediv>
		<refname>ST_MakeLine</refname>

		<refpurpose>Creates a LineString from Point, MultiPoint, or LineString geometries.</refpurpose>
		</refnamediv>

		<refsynopsisdiv>
		<funcsynopsis>
			<funcprototype>
				<funcdef>geometry <function>ST_MakeLine</function></funcdef>
				<paramdef><type>geometry</type> <parameter>geom1</parameter></paramdef>
				<paramdef><type>geometry</type> <parameter>geom2</parameter></paramdef>
			</funcprototype>

			<funcprototype>
				<funcdef>geometry <function>ST_MakeLine</function></funcdef>
				<paramdef><type>geometry[]</type> <parameter>geoms_array</parameter></paramdef>
			</funcprototype>

			<funcprototype>
				<funcdef>geometry <function>ST_MakeLine</function></funcdef>
				<paramdef><type>geometry set</type> <parameter>geoms</parameter></paramdef>
			</funcprototype>
		</funcsynopsis>
		</refsynopsisdiv>

		<refsection>
		<title>Description</title>

		<para>Creates a LineString containing the points of Point, MultiPoint, or LineString geometries.
		Other geometry types cause an error.
		</para>
		<para><emphasis role="bold">Variant 1:</emphasis> accepts two input geometries</para>
		<para><emphasis role="bold">Variant 2:</emphasis> accepts an array of geometries</para>
		<para><emphasis role="bold">Variant 3:</emphasis> aggregate function accepting a rowset of geometries.
		To ensure the order of the input geometries use <varname>ORDER BY</varname> in the function call,
		or a subquery with an <varname>ORDER BY</varname> clause.</para>

		<para>
		Repeated nodes at the beginning of input LineStrings are collapsed to a single point.
		Repeated points in Point and MultiPoint inputs are not collapsed.
		<xref linkend="ST_RemoveRepeatedPoints"/> can be used to collapse repeated points from the output LineString.
		</para>

		<para>&Z_support;</para>

		<para role="availability" conformance="2.3.0">Availability: 2.3.0 -  Support for MultiPoint input elements was introduced</para>
		<para role="availability" conformance="2.0.0">Availability: 2.0.0 -  Support for LineString input elements was introduced</para>
		<para role="availability" conformance="1.4.0">Availability: 1.4.0 -  ST_MakeLine(geomarray) was introduced. ST_MakeLine aggregate functions was enhanced to handle more points faster.</para>

		</refsection>

		<refsection>
			<title>Examples: Two-input variant</title>

<para>Create a line composed of two points.</para>
<programlisting>
SELECT ST_AsText( ST_MakeLine(ST_Point(1,2), ST_Point(3,4)) );

	  st_astext
---------------------
 LINESTRING(1 2,3 4)
</programlisting>

<para>Create a 3D line from two 3D points.</para>
<programlisting>
SELECT ST_AsEWKT( ST_MakeLine(ST_MakePoint(1,2,3), ST_MakePoint(3,4,5) ));

		st_asewkt
-------------------------
 LINESTRING(1 2 3,3 4 5)
</programlisting>

<para>Create a line from two disjoint LineStrings.</para>
<programlisting>
 select ST_AsText( ST_MakeLine( 'LINESTRING(0 0, 1 1)', 'LINESTRING(2 2, 3 3)' ) );

          st_astext
-----------------------------
 LINESTRING(0 0,1 1,2 2,3 3)
</programlisting>
		</refsection>

		<refsection>
			<title>Examples: Array variant</title>

		<para>Create a line from an array formed by a subquery with ordering.</para>
<programlisting>
SELECT ST_MakeLine( ARRAY( SELECT ST_Centroid(geom) FROM visit_locations ORDER BY visit_time) );
</programlisting>

		<para>Create a 3D line from an array of 3D points</para>
<programlisting>
SELECT ST_AsEWKT( ST_MakeLine(
          ARRAY[ ST_MakePoint(1,2,3), ST_MakePoint(3,4,5), ST_MakePoint(6,6,6) ]  ));

		st_asewkt
-------------------------
LINESTRING(1 2 3,3 4 5,6 6 6)
</programlisting>
		</refsection>

		<refsection>
		<title>Examples: Aggregate variant</title>
		<para>This example queries time-based sequences of GPS points from a set of tracks
		and creates one record for each track.
		The result geometries are LineStrings composed of the GPS track points in the order of travel.</para>

<para>Using aggregate <varname>ORDER BY</varname> provides a correctly-ordered LineString.</para>
		<programlisting>
SELECT gps.track_id, ST_MakeLine(gps.geom ORDER BY gps_time) As geom
	FROM gps_points As gps
	GROUP BY track_id;</programlisting>

<para>Prior to PostgreSQL 9, ordering in a subquery can be used.
However, sometimes the query plan may not respect the order of the subquery.</para>
		<programlisting>
SELECT gps.track_id, ST_MakeLine(gps.geom) As geom
	FROM ( SELECT track_id, gps_time, geom
			FROM gps_points ORDER BY track_id, gps_time ) As gps
	GROUP BY track_id;</programlisting>
		</refsection>

		<refsection>
			<title>See Also</title>
			<para><xref linkend="ST_RemoveRepeatedPoints"/>,
            <xref linkend="ST_AsEWKT"/>,
            <xref linkend="ST_AsText"/>,
            <xref linkend="ST_GeomFromText"/>,
            <xref linkend="ST_MakePoint"/>,
            <xref linkend="ST_Point"/>
            </para>
		</refsection>
	</refentry>


	<refentry xml:id="ST_MakePoint">
		<refnamediv>
		<refname>ST_MakePoint</refname>

		<refpurpose>Creates a 2D, 3DZ or 4D Point.</refpurpose>
		</refnamediv>

		<refsynopsisdiv>
		<funcsynopsis>
		  <funcprototype>
			<funcdef>geometry <function>ST_MakePoint</function></funcdef>
			<paramdef><type>float</type> <parameter>x</parameter></paramdef>
			<paramdef><type>float</type> <parameter>y</parameter></paramdef>
		  </funcprototype>
		</funcsynopsis>
		<funcsynopsis>
		  <funcprototype>
			<funcdef>geometry <function>ST_MakePoint</function></funcdef>
			<paramdef><type>float</type> <parameter>x</parameter></paramdef>
			<paramdef><type>float</type> <parameter>y</parameter></paramdef>
			<paramdef><type>float</type> <parameter>z</parameter></paramdef>
		  </funcprototype>
		</funcsynopsis>
		<funcsynopsis>
		  <funcprototype>
			<funcdef>geometry <function>ST_MakePoint</function></funcdef>
			<paramdef><type>float</type> <parameter>x</parameter></paramdef>
			<paramdef><type>float</type> <parameter>y</parameter></paramdef>
			<paramdef><type>float</type> <parameter>z</parameter></paramdef>
			<paramdef><type>float</type> <parameter>m</parameter></paramdef>
		  </funcprototype>
		</funcsynopsis>
		</refsynopsisdiv>

		<refsection>
			<title>Description</title>

			<para>Creates a 2D XY, 3D XYZ or 4D XYZM Point geometry.
			Use <xref linkend="ST_MakePointM"/> to make points with XYM coordinates.</para>

			<para>Use <xref linkend="ST_SetSRID"/> to specify a SRID for the created point.</para>

			<para>
			While not OGC-compliant, <varname>ST_MakePoint</varname> is
			faster and more precise than <xref linkend="ST_GeomFromText"/>
			and <xref linkend="ST_PointFromText"/>.
			It is also easier to use for numeric coordinate values.</para>

			<note><para>For geodetic coordinates, <varname>X</varname> is longitude and <varname>Y</varname> is latitude</para></note>

			<note><para>
			The functions 
			<xref linkend="ST_Point"/>, <xref linkend="ST_PointZ"/>, <xref linkend="ST_PointM"/>, and <xref linkend="ST_PointZM"/> 
			can be used to create points with a given SRID.
			</para></note>

			<para>&Z_support;</para>
		</refsection>

		<refsection>
		<title>Examples</title>
		 <programlisting>-- Create a point with unknown SRID
SELECT ST_MakePoint(-71.1043443253471, 42.3150676015829);

-- Create a point in the WGS 84 geodetic CRS
SELECT ST_SetSRID(ST_MakePoint(-71.1043443253471, 42.3150676015829),4326);

-- Create a 3D point (e.g. has altitude)
SELECT ST_MakePoint(1, 2,1.5);

-- Get z of point
SELECT ST_Z(ST_MakePoint(1, 2,1.5));
result
-------
1.5</programlisting>
		</refsection>
		<refsection>
			<title>See Also</title>
			<para>
			<xref linkend="ST_GeomFromText"/>, <xref linkend="ST_PointFromText"/>, <xref linkend="ST_SetSRID"/>, <xref linkend="ST_MakePointM"/>,
			<xref linkend="ST_Point"/>, <xref linkend="ST_PointZ"/>, <xref linkend="ST_PointM"/>, <xref linkend="ST_PointZM"/>
 			</para>
		</refsection>
	</refentry>

	<refentry xml:id="ST_MakePointM">
		<refnamediv>
		<refname>ST_MakePointM</refname>

		<refpurpose>Creates a Point from X, Y and M values.</refpurpose>
		</refnamediv>

		<refsynopsisdiv>
			<funcsynopsis>
			  <funcprototype>
				<funcdef>geometry <function>ST_MakePointM</function></funcdef>
				<paramdef><type>float</type> <parameter>x</parameter></paramdef>
				<paramdef><type>float</type> <parameter>y</parameter></paramdef>
				<paramdef><type>float</type> <parameter>m</parameter></paramdef>
			  </funcprototype>
			</funcsynopsis>
		</refsynopsisdiv>

		<refsection>
			<title>Description</title>

			<para>Creates a point with X, Y and M (measure) ordinates. 
			Use <xref linkend="ST_MakePoint"/> to make points with XY, XYZ, or XYZM coordinates.</para>

			<para>Use <xref linkend="ST_SetSRID"/> to specify a SRID for the created point.</para>

			<note><para>For geodetic coordinates, <varname>X</varname> is longitude and <varname>Y</varname> is latitude</para></note>

			<note><para>
			The functions 
			<xref linkend="ST_PointM"/>, and <xref linkend="ST_PointZM"/> 
			can be used to create points with an M value and a given SRID.
			</para></note>

		</refsection>

		<refsection>
		<title>Examples</title>
			<note><para><xref linkend="ST_AsEWKT"/> is used for text output
			because <xref linkend="ST_AsText"/> does not support M values.</para></note>

			<para>Create point with unknown SRID.</para>
		 <programlisting>
SELECT ST_AsEWKT(  ST_MakePointM(-71.1043443253471, 42.3150676015829, 10)  );

				   st_asewkt
-----------------------------------------------
 POINTM(-71.1043443253471 42.3150676015829 10)
</programlisting>

<para>Create point with a measure in the WGS 84 geodetic coordinate system.</para>
<programlisting>
SELECT ST_AsEWKT( ST_SetSRID(  ST_MakePointM(-71.104, 42.315, 10),  4326));

						st_asewkt
---------------------------------------------------------
SRID=4326;POINTM(-71.104 42.315 10)
</programlisting>

<para>Get measure of created point.</para>
<programlisting>
SELECT ST_M(  ST_MakePointM(-71.104, 42.315, 10)  );

result
-------
10
</programlisting>
		</refsection>
		<refsection>
			<title>See Also</title>
			<para><xref linkend="ST_MakePoint"/>, <xref linkend="ST_SetSRID"/>,
			<xref linkend="ST_PointM"/>, <xref linkend="ST_PointZM"/></para>
		</refsection>
	</refentry>

	<refentry xml:id="ST_MakePolygon">
		<refnamediv>
		<refname>ST_MakePolygon</refname>

		<refpurpose>Creates a Polygon from a shell and optional list of holes.</refpurpose>
		</refnamediv>

		<refsynopsisdiv>
		<funcsynopsis>
		  <funcprototype>
			<funcdef>geometry <function>ST_MakePolygon</function></funcdef>
			<paramdef><type>geometry</type> <parameter>linestring</parameter></paramdef>
		  </funcprototype>
		</funcsynopsis>
		<funcsynopsis>
		  <funcprototype>
			<funcdef>geometry <function>ST_MakePolygon</function></funcdef>
			<paramdef><type>geometry</type> <parameter>outerlinestring</parameter></paramdef>
			<paramdef><type>geometry[]</type> <parameter>interiorlinestrings</parameter></paramdef>
		  </funcprototype>
		</funcsynopsis>
		</refsynopsisdiv>

		<refsection>
			<title>Description</title>

			<para>Creates a Polygon formed by the given shell and optional array of holes.
			Input	geometries must be closed LineStrings (rings).</para>

			<para><emphasis role="bold">Variant 1:</emphasis>  Accepts one shell LineString.</para>
			<para><emphasis role="bold">Variant 2:</emphasis>  Accepts a shell LineString and an array of
			inner (hole) LineStrings. A geometry array can be constructed using the PostgreSQL array_agg(), ARRAY[] or
			ARRAY() constructs.</para>

			<note><para>This function does not accept MultiLineStrings.
			Use <xref linkend="ST_LineMerge"/> to generate a LineString, or <xref linkend="ST_Dump"/> to extract LineStrings.</para>
			</note>

			<para>&Z_support;</para>
		</refsection>

		<refsection>
		<title>Examples: Single input variant</title>
		<para>Create a Polygon from a 2D LineString.</para>
		 <programlisting>
SELECT ST_MakePolygon( ST_GeomFromText('LINESTRING(75 29,77 29,77 29, 75 29)'));
</programlisting>

<para>Create a Polygon from an open LineString,
using <xref linkend="ST_StartPoint"/> and <xref linkend="ST_AddPoint"/> to close it.</para>
<programlisting>
SELECT ST_MakePolygon( ST_AddPoint(foo.open_line, ST_StartPoint(foo.open_line)) )
FROM (
  SELECT ST_GeomFromText('LINESTRING(75 29,77 29,77 29, 75 29)') As open_line) As foo;
</programlisting>

<para>Create a Polygon from a 3D LineString</para>
<programlisting>
SELECT ST_AsEWKT( ST_MakePolygon( 'LINESTRING(75.15 29.53 1,77 29 1,77.6 29.5 1, 75.15 29.53 1)'));

st_asewkt
-----------
POLYGON((75.15 29.53 1,77 29 1,77.6 29.5 1,75.15 29.53 1))
</programlisting>
<para>Create a Polygon from a LineString with measures</para>
<programlisting>
SELECT ST_AsEWKT( ST_MakePolygon( 'LINESTRINGM(75.15 29.53 1,77 29 1,77.6 29.5 2, 75.15 29.53 2)' ));

st_asewkt
----------
POLYGONM((75.15 29.53 1,77 29 1,77.6 29.5 2,75.15 29.53 2))
</programlisting>
		</refsection>
		<refsection>
			<title>Examples: Outer shell with inner holes variant</title>

			<para>Create a donut Polygon with an extra hole</para>
		   <programlisting>
SELECT ST_MakePolygon( ST_ExteriorRing( ST_Buffer(ring.line,10)),
	ARRAY[  ST_Translate(ring.line, 1, 1),
		ST_ExteriorRing(ST_Buffer(ST_Point(20,20),1)) ]
	)
FROM (SELECT ST_ExteriorRing(
	ST_Buffer(ST_Point(10,10),10,10)) AS line ) AS ring;
</programlisting>
    <para>Create a set of province boundaries with holes
    representing lakes.  The input is a table of
    province Polygons/MultiPolygons and a table of water linestrings.
    Lines forming lakes are determined by using <xref linkend="ST_IsClosed"/>.
    The province linework is extracted by using
    <xref linkend="ST_Boundary"/>.
    As required by <code>ST_MakePolygon</code>,
    the boundary is forced to be a single LineString by using <xref linkend="ST_LineMerge"/>.
    (However, note that if a province has more than one region or has islands
    this will produce an invalid polygon.)
    Using a LEFT JOIN ensures all provinces are included even if they have no lakes.
    </para>

    <note><para>The CASE construct is used because passing a null array into
    ST_MakePolygon results in a NULL return value.</para></note>

		<programlisting>
SELECT p.gid, p.province_name,
	CASE WHEN array_agg(w.geom) IS NULL
	THEN p.geom
	ELSE  ST_MakePolygon( ST_LineMerge(ST_Boundary(p.geom)),
                        array_agg(w.geom)) END
FROM
	provinces p LEFT JOIN waterlines w
		ON (ST_Within(w.geom, p.geom) AND ST_IsClosed(w.geom))
GROUP BY p.gid, p.province_name, p.geom;
</programlisting>

	<para>Another technique is to utilize a correlated subquery
	and the ARRAY() constructor that converts a row set to an array.</para>
<programlisting>
SELECT p.gid,  p.province_name,
    CASE WHEN EXISTS( SELECT w.geom
        FROM waterlines w
        WHERE ST_Within(w.geom, p.geom)
        AND ST_IsClosed(w.geom))
    THEN ST_MakePolygon(
        ST_LineMerge(ST_Boundary(p.geom)),
        ARRAY( SELECT w.geom
            FROM waterlines w
            WHERE ST_Within(w.geom, p.geom)
            AND ST_IsClosed(w.geom)))
    ELSE p.geom
    END AS geom
FROM provinces p;
</programlisting>
		</refsection>
		<refsection>
			<title>See Also</title>
			<para>
				<xref linkend="ST_BuildArea"/>
				<xref linkend="ST_Polygon"/>
			</para>
		</refsection>
	</refentry>

	<refentry xml:id="ST_Point">
	  <refnamediv>
		<refname>ST_Point</refname>

		<refpurpose>Creates a Point with X, Y and SRID values.</refpurpose>
	  </refnamediv>

	  <refsynopsisdiv>
		<funcsynopsis>
		  <funcprototype>
			<funcdef>geometry <function>ST_Point</function></funcdef>
			<paramdef><type>float</type> <parameter>x</parameter></paramdef>
			<paramdef><type>float</type> <parameter>y</parameter></paramdef>
		  </funcprototype>
		</funcsynopsis>
        <funcsynopsis>
          <funcprototype>
            <funcdef>geometry <function>ST_Point</function></funcdef>
            <paramdef><type>float</type> <parameter>x</parameter></paramdef>
            <paramdef><type>float</type> <parameter>y</parameter></paramdef>
            <paramdef><type>integer</type> <parameter>srid=unknown</parameter></paramdef>
          </funcprototype>
        </funcsynopsis>
	  </refsynopsisdiv>

	  <refsection>
		<title>Description</title>

		<para>Returns a Point with the given X and Y coordinate values. This is the SQL-MM equivalent for <xref linkend="ST_MakePoint"/> that takes just X and Y.</para>

		<note><para>For geodetic coordinates, <varname>X</varname> is longitude and <varname>Y</varname> is latitude</para></note>

	    <para role="enhanced" conformance="3.2.0">Enhanced: 3.2.0 srid as an extra optional argument was added. Older installs require combining with ST_SetSRID to mark the srid on the geometry.</para>
		<para>&sqlmm_compliant; SQL-MM 3: 6.1.2</para>

	  </refsection>


	  <refsection>
		<title>Examples: Geometry</title>

        <programlisting>SELECT ST_Point( -71.104, 42.315);</programlisting>

        <para>Creating a point with SRID specified:</para>
		<programlisting>SELECT ST_Point( -71.104, 42.315, 4326);</programlisting>

        <para>Alternative way of specifying SRID:</para>
        <programlisting>SELECT ST_SetSRID( ST_Point( -71.104, 42.315), 4326);</programlisting>
	  </refsection>

	  <refsection>
		<title>Examples: Geography</title>

		<para>Create <link linkend="PostGIS_Geography">geography</link> points using the <varname>::</varname> cast syntax:</para>
		<programlisting>SELECT ST_Point( -71.104, 42.315, 4326)::geography;</programlisting>

        <para>Pre-PostGIS 3.2 code, using <varname>CAST</varname>:</para>
        <programlisting>SELECT CAST( ST_SetSRID(ST_Point( -71.104, 42.315), 4326) AS geography);</programlisting>

<para>If the point coordinates are not in a geodetic coordinate system (such as WGS84),
then they must be reprojected before casting to a geography.
In this example a point in Pennsylvania State Plane feet (SRID 2273)
is projected to WGS84 (SRID 4326).</para>
<programlisting>
SELECT ST_Transform( ST_Point( 3637510, 3014852, 2273), 4326)::geography;</programlisting>
	  </refsection>

	  <!-- Optionally add a "See Also" section -->
	  <refsection>
		<title>See Also</title>

		<para><xref linkend="ST_MakePoint"/>, 
			<xref linkend="ST_PointZ"/>, <xref linkend="ST_PointM"/>, <xref linkend="ST_PointZM"/>, 
			<xref linkend="ST_SetSRID"/>, <xref linkend="ST_Transform"/></para>
	  </refsection>
	</refentry>


    <refentry xml:id="ST_PointZ">
      <refnamediv>
        <refname>ST_PointZ</refname>
        <refpurpose>Creates a Point with X, Y, Z and SRID values.</refpurpose>
      </refnamediv>

      <refsynopsisdiv>
        <funcsynopsis>
          <funcprototype>
            <funcdef>geometry <function>ST_PointZ</function></funcdef>
            <paramdef><type>float</type> <parameter>x</parameter></paramdef>
            <paramdef><type>float</type> <parameter>y</parameter></paramdef>
            <paramdef><type>float</type> <parameter>z</parameter></paramdef>
            <paramdef choice="opt"><type>integer</type> <parameter>srid=unknown</parameter></paramdef>
          </funcprototype>
        </funcsynopsis>
      </refsynopsisdiv>

      <refsection>
        <title>Description</title>
        <para>Returns an Point with the given X, Y and Z coordinate values, and optionally an SRID number.</para>
        <para role="enhanced" conformance="3.2.0">Enhanced: 3.2.0 srid as an extra optional argument was added. Older installs require combining with ST_SetSRID to mark the srid on the geometry.</para>
      </refsection>

      <refsection>
        <title>Examples</title>
        <programlisting>SELECT ST_PointZ(-71.104, 42.315, 3.4, 4326)</programlisting>
        <programlisting>SELECT ST_PointZ(-71.104, 42.315, 3.4, srid =&gt; 4326)</programlisting>
        <programlisting>SELECT ST_PointZ(-71.104, 42.315, 3.4)</programlisting>
      </refsection>

      <refsection>
        <title>See Also</title>
        <para><xref linkend="ST_MakePoint"/>, <xref linkend="ST_Point"/>, <xref linkend="ST_PointM"/>, <xref linkend="ST_PointZM"/></para>
      </refsection>
    </refentry>

    <refentry xml:id="ST_PointM">
      <refnamediv>
        <refname>ST_PointM</refname>
        <refpurpose>Creates a Point with X, Y, M and SRID values.</refpurpose>
      </refnamediv>

      <refsynopsisdiv>
        <funcsynopsis>
          <funcprototype>
            <funcdef>geometry <function>ST_PointM</function></funcdef>
            <paramdef><type>float</type> <parameter>x</parameter></paramdef>
            <paramdef><type>float</type> <parameter>y</parameter></paramdef>
            <paramdef><type>float</type> <parameter>m</parameter></paramdef>
            <paramdef choice="opt"><type>integer</type> <parameter>srid=unknown</parameter></paramdef>
          </funcprototype>
        </funcsynopsis>
      </refsynopsisdiv>

      <refsection>
        <title>Description</title>
        <para>Returns an Point with the given X, Y and M coordinate values, and optionally an SRID number.</para>
        <para role="enhanced" conformance="3.2.0">Enhanced: 3.2.0 srid as an extra optional argument was added. Older installs require combining with ST_SetSRID to mark the srid on the geometry.</para>
      </refsection>

      <refsection>
        <title>Examples</title>
        <programlisting>SELECT ST_PointM(-71.104, 42.315, 3.4, 4326)</programlisting>
        <programlisting>SELECT ST_PointM(-71.104, 42.315, 3.4, srid =&gt; 4326)</programlisting>
        <programlisting>SELECT ST_PointM(-71.104, 42.315, 3.4)</programlisting>
      </refsection>

      <refsection>
        <title>See Also</title>
        <para><xref linkend="ST_MakePoint"/>, <xref linkend="ST_Point"/>, <xref linkend="ST_PointZ"/>, <xref linkend="ST_PointZM"/></para>
      </refsection>
    </refentry>


    <refentry xml:id="ST_PointZM">
      <refnamediv>
        <refname>ST_PointZM</refname>
        <refpurpose>Creates a Point with X, Y, Z, M and SRID values.</refpurpose>
      </refnamediv>

      <refsynopsisdiv>
        <funcsynopsis>
          <funcprototype>
            <funcdef>geometry <function>ST_PointZM</function></funcdef>
            <paramdef><type>float</type> <parameter>x</parameter></paramdef>
            <paramdef><type>float</type> <parameter>y</parameter></paramdef>
            <paramdef><type>float</type> <parameter>z</parameter></paramdef>
            <paramdef><type>float</type> <parameter>m</parameter></paramdef>
            <paramdef choice="opt"><type>integer</type> <parameter>srid=unknown</parameter></paramdef>
          </funcprototype>
        </funcsynopsis>
      </refsynopsisdiv>

      <refsection>
        <title>Description</title>
        <para>Returns an Point with the given X, Y, Z and M coordinate values, and optionally an SRID number.</para>
        <para role="enhanced" conformance="3.2.0">Enhanced: 3.2.0 srid as an extra optional argument was added. Older installs require combining with ST_SetSRID to mark the srid on the geometry.</para>
      </refsection>

      <refsection>
        <title>Examples</title>
        <programlisting>SELECT ST_PointZM(-71.104, 42.315, 3.4, 4.5, 4326)</programlisting>
        <programlisting>SELECT ST_PointZM(-71.104, 42.315, 3.4, 4.5, srid =&gt; 4326)</programlisting>
        <programlisting>SELECT ST_PointZM(-71.104, 42.315, 3.4, 4.5)</programlisting>
      </refsection>

      <refsection>
        <title>See Also</title>
        <para><xref linkend="ST_MakePoint"/>, <xref linkend="ST_Point"/>, <xref linkend="ST_PointM"/>, <xref linkend="ST_PointZ"/>, <xref linkend="ST_SetSRID"/></para>
      </refsection>
    </refentry>

	<refentry xml:id="ST_Polygon">
	  <refnamediv>
		<refname>ST_Polygon</refname>
		<refpurpose>Creates a Polygon from a LineString with a specified SRID.</refpurpose>
	  </refnamediv>

	  <refsynopsisdiv>
		<funcsynopsis>
		  <funcprototype>
			<funcdef>geometry <function>ST_Polygon</function></funcdef>
			<paramdef><type>geometry </type> <parameter>lineString</parameter></paramdef>
			<paramdef><type>integer </type> <parameter>srid</parameter></paramdef>
		  </funcprototype>
		</funcsynopsis>
	  </refsynopsisdiv>

	  <refsection>
		<title>Description</title>

		<para>Returns a polygon built from the given LineString
		and sets the spatial reference system from the <varname>srid</varname>.</para>

		<para>ST_Polygon is similar to <xref linkend="ST_MakePolygon"/> Variant 1
		with the addition of setting the SRID.</para>
		<para>To create polygons with holes
		use <xref linkend="ST_MakePolygon"/> Variant 2 and then <xref linkend="ST_SetSRID"/>.
		</para>

		<note><para>This function does not accept MultiLineStrings.
		Use <xref linkend="ST_LineMerge"/> to generate a LineString, or <xref linkend="ST_Dump"/> to extract LineStrings.</para>
		</note>

		<para>&sfs_compliant;</para>
		<para>&sqlmm_compliant; SQL-MM 3: 8.3.2</para>
		<para>&Z_support;</para>

	  </refsection>

	  <refsection>
		<title>Examples</title>

<para>Create a 2D polygon.</para>
		<programlisting>
SELECT ST_AsText( ST_Polygon('LINESTRING(75 29, 77 29, 77 29, 75 29)'::geometry, 4326) );

-- result --
POLYGON((75 29, 77 29, 77 29, 75 29))
</programlisting>
<para>Create a 3D polygon.</para>
<programlisting>
SELECT ST_AsEWKT( ST_Polygon( ST_GeomFromEWKT('LINESTRING(75 29 1, 77 29 2, 77 29 3, 75 29 1)'), 4326) );

-- result --
SRID=4326;POLYGON((75 29 1, 77 29 2, 77 29 3, 75 29 1))
</programlisting>
	  </refsection>

	  <!-- Optionally add a "See Also" section -->
	  <refsection>
		<title>See Also</title>

		<para> <xref linkend="ST_AsEWKT"/>, <xref linkend="ST_AsText"/>, <xref linkend="ST_GeomFromEWKT"/>, <xref linkend="ST_GeomFromText"/>, <xref linkend="ST_LineMerge"/>, <xref linkend="ST_MakePolygon"/></para>
	  </refsection>
	</refentry>


	<refentry xml:id="ST_TileEnvelope">
		<refnamediv>
		<refname>ST_TileEnvelope</refname>
		<refpurpose>Creates a rectangular Polygon in <link xlink:href="https://en.wikipedia.org/wiki/Web_Mercator_projection">Web Mercator</link> (SRID:3857) using the <link xlink:href="https://en.wikipedia.org/wiki/Tiled_web_map">XYZ tile system</link>.</refpurpose>
		</refnamediv>

		<refsynopsisdiv>
		<funcsynopsis>
		  <funcprototype>
			<funcdef>geometry <function>ST_TileEnvelope</function></funcdef>
			<paramdef><type>integer</type> <parameter>tileZoom</parameter></paramdef>
			<paramdef><type>integer</type> <parameter>tileX</parameter></paramdef>
			<paramdef><type>integer</type> <parameter>tileY</parameter></paramdef>
			<paramdef choice="opt"><type>geometry</type> <parameter>bounds=SRID=3857;LINESTRING(-20037508.342789 -20037508.342789,20037508.342789 20037508.342789)</parameter></paramdef>
			<paramdef choice="opt"><type>float</type> <parameter>margin=0.0</parameter></paramdef>
		  </funcprototype>
		 </funcsynopsis>
		</refsynopsisdiv>

		<refsection>
			<title>Description</title>

			<para>Creates a rectangular Polygon
            giving the extent of a tile in the <link xlink:href="https://en.wikipedia.org/wiki/Tiled_web_map">XYZ tile system</link>.
            The tile is specified by the zoom level Z and the XY index of the tile in the grid at that level.
            Can be used to define the tile bounds required by <xref linkend="ST_AsMVTGeom"/> to convert geometry
            into the MVT tile coordinate space.
            </para>
            <para>By default, the tile envelope is in the <link xlink:href="https://en.wikipedia.org/wiki/Web_Mercator_projection">Web Mercator</link> coordinate system (SRID:3857)
            using the standard range of the Web Mercator system (-20037508.342789, 20037508.342789).
            This is the most common coordinate system used for MVT tiles.
            The optional <varname>bounds</varname> parameter can be used to generate tiles in any coordinate system.
            It is a geometry that has the SRID and extent of the "Zoom Level zero" square within which the XYZ tile system is inscribed.</para>

			<para>The optional <varname>margin</varname> parameter can be used to expand a tile by the given percentage.
            E.g. <varname>margin=0.125</varname> expands the tile by 12.5%, which is equivalent to buffer=512 when the tile extent size is 4096, as used in <xref linkend="ST_AsMVTGeom"/>.
            This is useful to create a tile buffer to include data lying outside of the tile's visible area, but whose existence affects the tile rendering.
            For example, a city name (a point) could be near an edge of a tile, so its label should be rendered on two tiles, even though the point is located in the visible area of just one tile.
            Using expanded tiles in a query will include the city point in both tiles.
            Use a negative value to shrink the tile instead. Values less than -0.5 are prohibited because that would eliminate the tile completely.
            Do not specify a margin when using with <varname>ST_AsMVTGeom</varname>.
            See the example for <xref linkend="ST_AsMVT"/>.</para>

			<para role="enhanced" conformance="3.1.0">Enhanced: 3.1.0 Added margin parameter.</para>
			<para role="availability" conformance="3.0.0">Availability: 3.0.0</para>
		</refsection>

		<refsection>
		<title>Example: Building a tile envelope</title>
		 <programlisting>SELECT ST_AsText( ST_TileEnvelope(2, 1, 1) );

 st_astext
------------------------------
 POLYGON((-10018754.1713945 0,-10018754.1713945 10018754.1713945,0 10018754.1713945,0 0,-10018754.1713945 0))

SELECT ST_AsText( ST_TileEnvelope(3, 1, 1, ST_MakeEnvelope(-180, -90, 180, 90, 4326) ) );

                      st_astext
------------------------------------------------------
 POLYGON((-135 45,-135 67.5,-90 67.5,-90 45,-135 45))
</programlisting>
		</refsection>
		<refsection>
			<title>See Also</title>
			<para><xref linkend="ST_MakeEnvelope"/></para>
		</refsection>
	</refentry>



	<refentry xml:id="ST_HexagonGrid">
		<refnamediv>
		<refname>ST_HexagonGrid</refname>
		<refpurpose>Returns a set of hexagons and cell indices that completely cover the bounds of the geometry argument.</refpurpose>
		</refnamediv>

		<refsynopsisdiv>
		<funcsynopsis>
		  <funcprototype>
			<funcdef>setof record <function>ST_HexagonGrid</function></funcdef>
			<paramdef><type>float8</type> <parameter>size</parameter></paramdef>
			<paramdef><type>geometry</type> <parameter>bounds</parameter></paramdef>
		  </funcprototype>
		 </funcsynopsis>
		</refsynopsisdiv>

		<refsection>
			<title>Description</title>

			<para>Starts with the concept of a hexagon tiling of the plane.
			(Not a hexagon tiling of the globe, this is not the
			<link xlink:href="https://github.com/uber/h3">H3</link> tiling scheme.)
			For a given planar SRS, and a given edge size, starting at the origin of the SRS,
			there is one unique hexagonal tiling of the plane, Tiling(SRS, Size).
			This function answers the question: what hexagons in a given Tiling(SRS, Size)
			overlap with a given bounds.</para>

			<para><inlinemediaobject><imageobject>
				<imagedata fileref="images/st_hexagongrid01.png"/>
			</imageobject></inlinemediaobject></para>

			<para>The SRS for the output hexagons is the SRS provided by the bounds geometry.</para>
			<para>Doubling or tripling the edge size of the hexagon generates a new parent tiling that
			fits with the origin tiling. Unfortunately, it is not possible to generate parent
			hexagon tilings that the child tiles perfectly fit inside.</para>

			<para><inlinemediaobject><imageobject>
				<imagedata fileref="images/st_hexagongrid02.png"/>
			</imageobject></inlinemediaobject></para>

			<para role="availability" conformance="3.1.0">Availability: 3.1.0</para>

		</refsection>

		<refsection>
		<title>Example: Counting points in hexagons</title>
		<para>To do a point summary against a hexagonal tiling, generate a hexagon grid using the
		extent of the points as the bounds, then spatially join to that grid.</para>
		 <programlisting>SELECT COUNT(*), hexes.geom
FROM
    ST_HexagonGrid(
        10000,
        ST_SetSRID(ST_EstimatedExtent('pointtable', 'geom'), 3857)
    ) AS hexes
    INNER JOIN
    pointtable AS pts
    ON ST_Intersects(pts.geom, hexes.geom)
GROUP BY hexes.geom;</programlisting>
    </refsection>
    <refsection>
		<title>Example: Generating hex coverage of polygons</title>
		<para>If we generate a set of hexagons for each polygon boundary and filter
			out those that do not intersect their hexagons, we end up with a tiling for
			each polygon.</para>
		<para><inlinemediaobject><imageobject>
			<imagedata fileref="images/st_hexagongrid03.png"/>
		</imageobject></inlinemediaobject></para>
		<para>Tiling states results in a hexagon coverage of each state, and multiple
			hexagons overlapping at the borders between states.</para>
		<note><para>The LATERAL keyword is implied for set-returning functions when referring to a prior table in the FROM list. So CROSS JOIN LATERAL, CROSS JOIN, or just plain , are equivalent constructs for this example.</para></note>
        <programlisting>SELECT admin1.gid, hex.geom
FROM
    admin1
    CROSS JOIN
    ST_HexagonGrid(100000, admin1.geom) AS hex
WHERE
    adm0_a3 = 'USA'
    AND
    ST_Intersects(admin1.geom, hex.geom)</programlisting>
        </refsection>
        <refsection>
            <title>See Also</title>
            <para><xref linkend="ST_EstimatedExtent"/>, <xref linkend="ST_SetSRID"/>, <xref linkend="ST_SquareGrid"/>, <xref linkend="ST_TileEnvelope"/></para>
        </refsection>
	</refentry>

	<refentry xml:id="ST_Hexagon">
		<refnamediv>
		<refname>ST_Hexagon</refname>
		<refpurpose>Returns a single hexagon, using the provided edge size and
			cell coordinate within the hexagon grid space.</refpurpose>
		</refnamediv>

		<refsynopsisdiv>
		<funcsynopsis>
		  <funcprototype>
			<funcdef>geometry <function>ST_Hexagon</function></funcdef>
			<paramdef><type>float8</type> <parameter>size</parameter></paramdef>
			<paramdef><type>integer</type> <parameter>cell_i</parameter></paramdef>
			<paramdef><type>integer</type> <parameter>cell_j</parameter></paramdef>
			<paramdef choice="opt"><type>geometry</type> <parameter>origin</parameter></paramdef>
		  </funcprototype>
		 </funcsynopsis>
		</refsynopsisdiv>

		<refsection>
			<title>Description</title>

			<para>Uses the same hexagon tiling concept as <xref linkend="ST_HexagonGrid"/>, but generates just one hexagon at the desired cell coordinate. Optionally,
			can adjust origin coordinate of the tiling, the default origin is at 0,0.
			</para>
			<para>Hexagons are generated with no SRID set, so use <xref linkend="ST_SetSRID"/> to set the SRID to the one you expect.</para>

			<para role="availability" conformance="3.1.0">Availability: 3.1.0</para>
		</refsection>

		<refsection>
		<title>Example: Creating a hexagon at the origin</title>
		 <programlisting>SELECT ST_AsText(ST_SetSRID(ST_Hexagon(1.0, 0, 0), 3857));

POLYGON((-1 0,-0.5
         -0.866025403784439,0.5
         -0.866025403784439,1
         0,0.5
         0.866025403784439,-0.5
         0.866025403784439,-1 0)) </programlisting>
		</refsection>
		<refsection>
			<title>See Also</title>
			<para><xref linkend="ST_TileEnvelope"/>, <xref linkend="ST_HexagonGrid"/>, <xref linkend="ST_Square"/></para>
		</refsection>
	</refentry>

    <refentry xml:id="ST_SquareGrid">
        <refnamediv>
        <refname>ST_SquareGrid</refname>
        <refpurpose>Returns a set of grid squares and cell indices that completely cover the bounds of the geometry argument.</refpurpose>
        </refnamediv>

        <refsynopsisdiv>
        <funcsynopsis>
            <funcprototype>
            <funcdef>setof record <function>ST_SquareGrid</function></funcdef>
            <paramdef><type>float8</type> <parameter>size</parameter></paramdef>
            <paramdef><type>geometry</type> <parameter>bounds</parameter></paramdef>
            </funcprototype>
            </funcsynopsis>
        </refsynopsisdiv>

        <refsection>
            <title>Description</title>

            <para>Starts with the concept of a square tiling of the plane.
            For a given planar SRS, and a given edge size, starting at the origin of the SRS,
            there is one unique square tiling of the plane, Tiling(SRS, Size).
            This function answers the question: what grids in a given Tiling(SRS, Size)
            overlap with a given bounds.</para>

            <para>The SRS for the output squares is the SRS provided by the bounds geometry.</para>
            <para>Doubling or edge size of the square generates a new parent tiling that
            perfectly fits with the original tiling. Standard web map tilings in mercator
            are just powers-of-two square grids in the mercator plane.</para>

            <para role="availability" conformance="3.1.0">Availability: 3.1.0</para>

        </refsection>

        <refsection>
        <title>Example: Generating a 1 degree grid for a country</title>
        <para>The grid will fill the whole bounds of the country, so if you want just squares
            that touch the country you will have to filter afterwards with ST_Intersects.</para>
            <programlisting>WITH grid AS (
SELECT (ST_SquareGrid(1, ST_Transform(geom,4326))).*
FROM admin0 WHERE name = 'Canada'
)
  SELEcT ST_AsText(geom)
  FROM grid</programlisting>
        </refsection>

        <refsection>
        <title>Example: Counting points in squares (using single chopped grid)</title>
        <para>To do a point summary against a square tiling, generate a square grid using the
        extent of the points as the bounds, then spatially join to that grid. Note the estimated extent might be off from actual extent, so be cautious and at very least make sure you've analyzed your table.</para>
            <programlisting>SELECT COUNT(*), squares.geom
    FROM
    pointtable AS pts
    INNER JOIN
    ST_SquareGrid(
        1000,
        ST_SetSRID(ST_EstimatedExtent('pointtable', 'geom'), 3857)
    ) AS squares
    ON ST_Intersects(pts.geom, squares.geom)
    GROUP BY squares.geom</programlisting>
        </refsection>

    <refsection>
        <title>Example: Counting points in squares using set of grid per point</title>
        <para>This yields the same result as the first example but will be slower for a large number of points</para>
            <programlisting>SELECT COUNT(*), squares.geom
    FROM
    pointtable AS pts
    INNER JOIN
    ST_SquareGrid(
        1000,
       pts.geom
    ) AS squares
    ON ST_Intersects(pts.geom, squares.geom)
    GROUP BY squares.geom</programlisting>
        </refsection>

        <refsection>
            <title>See Also</title>
            <para><xref linkend="ST_TileEnvelope"/>, <xref linkend="ST_HexagonGrid"/>
            , <xref linkend="ST_EstimatedExtent"/>
            , <xref linkend="ST_SetSRID"/></para>
        </refsection>
    </refentry>

	<refentry xml:id="ST_Square">
		<refnamediv>
		<refname>ST_Square</refname>
		<refpurpose>Returns a single square, using the provided edge size and
			cell coordinate within the square grid space.</refpurpose>
		</refnamediv>

		<refsynopsisdiv>
		<funcsynopsis>
		  <funcprototype>
			<funcdef>geometry <function>ST_Square</function></funcdef>
			<paramdef><type>float8</type> <parameter>size</parameter></paramdef>
			<paramdef><type>integer</type> <parameter>cell_i</parameter></paramdef>
			<paramdef><type>integer</type> <parameter>cell_j</parameter></paramdef>
			<paramdef choice="opt"><type>geometry</type> <parameter>origin</parameter></paramdef>
		  </funcprototype>
		 </funcsynopsis>
		</refsynopsisdiv>

		<refsection>
			<title>Description</title>

			<para>Uses the same square tiling concept as <xref linkend="ST_SquareGrid"/>, but generates just one square at the desired cell coordinate. Optionally,
			can adjust origin coordinate of the tiling, the default origin is at 0,0.
			</para>
			<para>Squares are generated with no SRID set, so use <xref linkend="ST_SetSRID"/> to set the SRID to the one you expect.</para>

			<para role="availability" conformance="3.1.0">Availability: 3.1.0</para>
		</refsection>

		<refsection>
		<title>Example: Creating a square at the origin</title>
		 <programlisting>SELECT ST_AsText(ST_SetSRID(ST_Square(1.0, 0, 0), 3857));

 POLYGON((0 0,0 1,1 1,1 0,0 0))</programlisting>
 		</refsection>
		<refsection>
			<title>See Also</title>
			<para><xref linkend="ST_TileEnvelope"/>, <xref linkend="ST_SquareGrid"/>, <xref linkend="ST_Hexagon"/></para>
		</refsection>
	</refentry>



    <refentry xml:id="ST_Letters">
        <refnamediv>
        <refname>ST_Letters</refname>
        <refpurpose>Returns the input letters rendered as geometry with a default start position at the origin and default text height of 100.</refpurpose>
        </refnamediv>
        <refsynopsisdiv>
        <funcsynopsis>
          <funcprototype>
            <funcdef>geometry <function>ST_Letters</function></funcdef>
            <paramdef><type>text</type> <parameter> letters</parameter></paramdef>
            <paramdef choice="opt"><type>json</type> <parameter> font</parameter></paramdef>
          </funcprototype>
         </funcsynopsis>
        </refsynopsisdiv>

        <refsection>
            <title>Description</title>

            <para>Uses a built-in font to render out a string as a multipolygon geometry. The default text height is 100.0, the distance from the bottom of a descender to the top of a capital. The default start position places the start of the baseline at the origin. Over-riding the font involves passing in a json map, with a character as the key, and base64 encoded TWKB for the font shape, with the fonts having a height of 1000 units from the bottom of the descenders to the tops of the capitals.
            </para>

            <para>The text is generated at the origin by default, so to reposition and resize the text, first apply the <code>ST_Scale</code> function and then apply the <code>ST_Translate</code> function.</para>

            <para role="availability" conformance="3.3.0">Availability: 3.3.0</para>
        </refsection>

        <refsection>
            <title>Example: Generating the word 'Yo'</title>
            <programlisting>SELECT ST_AsText(ST_Letters('Yo'), 1);</programlisting>
            <informalfigure>
            <mediaobject>
              <imageobject>
                <imagedata fileref="images/st_letters01.png"/>
              </imageobject>
              <caption><para>Letters generated by ST_Letters</para></caption>
            </mediaobject>
            </informalfigure>
        </refsection>
        <refsection>
            <title>Example: Scaling and moving words</title>
            <programlisting>SELECT ST_Translate(ST_Scale(ST_Letters('Yo'), 10, 10), 100,100);</programlisting>
        </refsection>
        <refsection>
            <title>See Also</title>
            <para><xref linkend="ST_AsTWKB"/>, <xref linkend="ST_Scale"/>, <xref linkend="ST_Translate"/></para>
        </refsection>
    </refentry>


  </section>