<?xml version="1.0" encoding="UTF-8"?>
  <sect1 id="Spatial_Relationships">
    <sect1info>
    <abstract>
    <para>These functions determine spatial relationships between geometries.</para>
    </abstract>
    </sect1info>
	<title>Spatial Relationships</title>

		<sect2>
		<title>Topological Relationships</title>

	<refentry id="ST_3DIntersects">
		<refnamediv>
			<refname>ST_3DIntersects</refname>

			<refpurpose>Returns TRUE if the Geometries "spatially
			intersect" in 3D - only for points, linestrings, polygons, polyhedral surface (area).
			</refpurpose>
		</refnamediv>
		<refsynopsisdiv>
			<funcsynopsis>
				<funcprototype>
					<funcdef>boolean <function>ST_3DIntersects</function></funcdef>
					<paramdef>
						<type>geometry</type>
						<parameter>geomA</parameter>
					</paramdef>
					<paramdef>
						<type>geometry</type>
						<parameter>geomB</parameter>
					</paramdef>
				</funcprototype>
			</funcsynopsis>
		</refsynopsisdiv>
		<refsection>
			<title>Description</title>
			<para>Overlaps, Touches, Within all imply spatial intersection.  If any of the aforementioned
				returns true, then the geometries also spatially intersect.
				Disjoint implies false for spatial intersection.</para>

			<para>Changed: 3.0.0 SFCGAL backend removed, GEOS backend supports TINs.</para>
			<para>Availability: 2.0.0</para>
			<note>
			  <para>This function call will automatically include a bounding box
			  comparison that will make use of any indexes that are available on the
			  geometries.</para>
			</note>

			<para>&Z_support;</para>
			<!-- Optionally mention supports Polyhedral Surface  -->
			<para>&P_support;</para>
			<para>&T_support;</para>
			<para>&sfcgal_enhanced;</para>
			<para>&sqlmm_compliant; SQL-MM 3: ?</para>
		</refsection>
		<refsection>
		<title>Geometry Examples</title>
<programlisting>SELECT ST_3DIntersects(pt, line), ST_Intersects(pt, line)
	FROM (SELECT 'POINT(0 0 2)'::geometry As pt, 'LINESTRING (0 0 1, 0 2 3)'::geometry As line) As foo;
 st_3dintersects | st_intersects
-----------------+---------------
 f               | t
(1 row)
		</programlisting>
		</refsection>

		<refsection><title>TIN Examples</title>
		    <programlisting>SELECT ST_3DIntersects('TIN(((0 0 0,1 0 0,0 1 0,0 0 0)))'::geometry, 'POINT(.1 .1 0)'::geometry);
 st_3dintersects
-----------------
 t</programlisting></refsection>

		<refsection>
			<title>See Also</title>
			<para><xref linkend="ST_Intersects"/></para>
		</refsection>
	</refentry>

  <refentry id="ST_Contains">
	  <refnamediv>
		<refname>ST_Contains</refname>

		<refpurpose>Returns true if and only if no points of B lie in the exterior of A, and at least one point of the interior of B lies in the interior of A. </refpurpose>
	  </refnamediv>

	  <refsynopsisdiv>
		<funcsynopsis>
		  <funcprototype>
			<funcdef>boolean <function>ST_Contains</function></funcdef>

			<paramdef><type>geometry </type>
			<parameter>geomA</parameter></paramdef>

			<paramdef><type>geometry </type>
			<parameter>geomB</parameter></paramdef>
		  </funcprototype>
		</funcsynopsis>
	  </refsynopsisdiv>

	  <refsection>
		<title>Description</title>

		<para>Geometry A contains Geometry B if and only if no points of B lie in the exterior of A, and at least one point of the interior of B lies in the interior of A.
		An important subtlety of this definition is that A does not contain its boundary, but A does contain itself. Contrast that to <xref linkend="ST_ContainsProperly" /> where geometry
		A does not Contain Properly itself.</para>

		<para>Returns TRUE if geometry B is completely inside geometry A. For this function to make
		sense, the source geometries must both be of the same coordinate projection,
		having the same SRID.  ST_Contains is the inverse of ST_Within.  So ST_Contains(A,B) implies ST_Within(B,A) except in the case of
		invalid geometries where the result is always false regardless or not defined.</para>

		<para>Performed by the GEOS module</para>
		<para>Enhanced: 2.3.0 Enhancement to PIP short-circuit extended to support MultiPoints with few points. Prior versions only supported point in polygon.</para>

		<important>
		  <para>Enhanced: 3.0.0 enabled support for <varname>GEOMETRYCOLLECTION</varname></para>
		</important>

		<important>
		  <para>Do not use this function with invalid geometries. You will get unexpected results.</para>
		</important>

		<para>This function call will automatically include a bounding box
			comparison that will make use of any indexes that are available on
			the geometries. To avoid index use, use the function
			_ST_Contains.</para>

		<para>NOTE: this is the "allowable" version that returns a
			boolean, not an integer.</para>

		<para>&sfs_compliant; s2.1.1.2 // s2.1.13.3
		- same as within(geometry B, geometry A)</para>
		<para>&sqlmm_compliant;	SQL-MM 3: 5.1.31</para>

		<para>There are certain subtleties to ST_Contains and ST_Within that are not intuitively obvious.
			For details check out <ulink url="http://lin-ear-th-inking.blogspot.com/2007/06/subtleties-of-ogc-covers-spatial.html">Subtleties of OGC Covers, Contains, Within</ulink></para>
	  </refsection>

	  <refsection>
		<title>Examples</title>

		<para>The <function>ST_Contains</function> predicate returns <varname>TRUE</varname> in all the following illustrations.</para>

		<informaltable>
		  <tgroup cols="2">
			<tbody>
			  <row>
				<entry><para><informalfigure>
					<mediaobject>
					  <imageobject>
						<imagedata fileref="images/st_contains01.png" />
					  </imageobject>

					  <caption><para><varname>LINESTRING</varname> / <varname>MULTIPOINT</varname></para></caption>
					</mediaobject>
				  </informalfigure></para></entry>

				<entry><para><informalfigure>
					<mediaobject>
					  <imageobject>
						<imagedata fileref="images/st_contains02.png" />
					  </imageobject>

					  <caption><para><varname>POLYGON</varname> / <varname>POINT</varname></para></caption>
					</mediaobject>
				  </informalfigure></para></entry>
			  </row>
			  <row>
				<entry><para><informalfigure>
					<mediaobject>
					  <imageobject>
						<imagedata fileref="images/st_contains03.png" />
					  </imageobject>

					  <caption><para><varname>POLYGON</varname> / <varname>LINESTRING</varname></para></caption>
					</mediaobject>
				  </informalfigure></para></entry>

				<entry><para><informalfigure>
					<mediaobject>
					  <imageobject>
						<imagedata fileref="images/st_contains04.png" />
					  </imageobject>

					  <caption><para><varname>POLYGON</varname> / <varname>POLYGON</varname></para></caption>
					</mediaobject>
				  </informalfigure></para></entry>
			  </row>
			</tbody>
		  </tgroup>
		</informaltable>

		<para>The <function>ST_Contains</function> predicate returns <varname>FALSE</varname> in all the following illustrations.</para>

		<informaltable>
		  <tgroup cols="2">
			<tbody>
			  <row>
				<entry><para><informalfigure>
					<mediaobject>
					  <imageobject>
						<imagedata fileref="images/st_contains05.png" />
					  </imageobject>

					  <caption><para><varname>POLYGON</varname> / <varname>MULTIPOINT</varname></para></caption>
					</mediaobject>
				  </informalfigure></para></entry>

				<entry><para><informalfigure>
					<mediaobject>
					  <imageobject>
						<imagedata fileref="images/st_contains06.png" />
					  </imageobject>

					  <caption><para><varname>POLYGON</varname> / <varname>LINESTRING</varname></para></caption>
					</mediaobject>
				  </informalfigure></para></entry>
			  </row>
			</tbody>
		  </tgroup>
		</informaltable>

		  <programlisting>
-- A circle within a circle
SELECT ST_Contains(smallc, bigc) As smallcontainsbig,
	   ST_Contains(bigc,smallc) As bigcontainssmall,
	   ST_Contains(bigc, ST_Union(smallc, bigc)) as bigcontainsunion,
	   ST_Equals(bigc, ST_Union(smallc, bigc)) as bigisunion,
	   ST_Covers(bigc, ST_ExteriorRing(bigc)) As bigcoversexterior,
	   ST_Contains(bigc, ST_ExteriorRing(bigc)) As bigcontainsexterior
FROM (SELECT ST_Buffer(ST_GeomFromText('POINT(1 2)'), 10) As smallc,
			 ST_Buffer(ST_GeomFromText('POINT(1 2)'), 20) As bigc) As foo;

-- Result
  smallcontainsbig | bigcontainssmall | bigcontainsunion | bigisunion | bigcoversexterior | bigcontainsexterior
------------------+------------------+------------------+------------+-------------------+---------------------
 f                | t                | t                | t          | t        | f

-- Example demonstrating difference between contains and contains properly
SELECT ST_GeometryType(geomA) As geomtype, ST_Contains(geomA,geomA) AS acontainsa, ST_ContainsProperly(geomA, geomA) AS acontainspropa,
   ST_Contains(geomA, ST_Boundary(geomA)) As acontainsba, ST_ContainsProperly(geomA, ST_Boundary(geomA)) As acontainspropba
FROM (VALUES ( ST_Buffer(ST_Point(1,1), 5,1) ),
			 ( ST_MakeLine(ST_Point(1,1), ST_Point(-1,-1) ) ),
			 ( ST_Point(1,1) )
	  ) As foo(geomA);

  geomtype    | acontainsa | acontainspropa | acontainsba | acontainspropba
--------------+------------+----------------+-------------+-----------------
ST_Polygon    | t          | f              | f           | f
ST_LineString | t          | f              | f           | f
ST_Point      | t          | t              | f           | f

 </programlisting>
	  </refsection>

	  <refsection>
		<title>See Also</title>
		<para><xref linkend="ST_Boundary" />, <xref linkend="ST_ContainsProperly" />, <xref linkend="ST_Covers" />, <xref linkend="ST_CoveredBy" />, <xref linkend="ST_Equals"/>, <xref linkend="ST_Within"/></para>
	  </refsection>
 </refentry>

 <refentry id="ST_ContainsProperly">
	  <refnamediv>
		<refname>ST_ContainsProperly</refname>

		<refpurpose>Returns true if B intersects the interior of A but not the boundary (or exterior). A does not contain properly itself, but does contain itself.</refpurpose>
	  </refnamediv>

	  <refsynopsisdiv>
		<funcsynopsis>
		  <funcprototype>
			<funcdef>boolean <function>ST_ContainsProperly</function></funcdef>

			<paramdef><type>geometry </type>
			<parameter>geomA</parameter></paramdef>

			<paramdef><type>geometry </type>
			<parameter>geomB</parameter></paramdef>
		  </funcprototype>
		</funcsynopsis>
	  </refsynopsisdiv>

	  <refsection>
		<title>Description</title>

		<para>Returns true if B intersects the interior of A but not the boundary (or exterior).</para>

		<para>A does not contain properly itself, but does contain itself.</para>
		<para>Every point of the other geometry is a point of this geometry's interior. The DE-9IM Intersection Matrix for the two geometries matches
   [T**FF*FF*] used in <xref linkend="ST_Relate" /></para>

		<note>
		  <para>From JTS docs slightly reworded: The advantage to using this predicate over <xref linkend="ST_Contains" /> and <xref linkend="ST_Intersects" /> is that it can be computed
	  efficiently, with no need to compute topology at individual points.</para>
		<para>
			 An example use case for this predicate is computing the intersections of a set of geometries with a large polygonal geometry. Since intersection is a fairly slow operation, it can be more efficient to use containsProperly to filter out test geometries which lie
	wholly inside the area.  In these cases the intersection is	known a priori to be exactly the original test geometry.
	 </para>
		</note>
		<para>Performed by the GEOS module.</para>
		<para>Availability: 1.4.0</para>

		<important>
		  <para>Enhanced: 3.0.0 enabled support for <varname>GEOMETRYCOLLECTION</varname></para>
		</important>

		<important>
		  <para>Do not use this function with invalid geometries. You will get unexpected results.</para>
		</important>

		<para>This function call will automatically include a bounding box
			comparison that will make use of any indexes that are available on
			the geometries. To avoid index use, use the function
			_ST_ContainsProperly.</para>

	  </refsection>

	  <refsection>
		<title>Examples</title>
		  <programlisting>
	--a circle within a circle
	SELECT ST_ContainsProperly(smallc, bigc) As smallcontainspropbig,
	ST_ContainsProperly(bigc,smallc) As bigcontainspropsmall,
	ST_ContainsProperly(bigc, ST_Union(smallc, bigc)) as bigcontainspropunion,
	ST_Equals(bigc, ST_Union(smallc, bigc)) as bigisunion,
	ST_Covers(bigc, ST_ExteriorRing(bigc)) As bigcoversexterior,
	ST_ContainsProperly(bigc, ST_ExteriorRing(bigc)) As bigcontainsexterior
	FROM (SELECT ST_Buffer(ST_GeomFromText('POINT(1 2)'), 10) As smallc,
	ST_Buffer(ST_GeomFromText('POINT(1 2)'), 20) As bigc) As foo;
	--Result
  smallcontainspropbig | bigcontainspropsmall | bigcontainspropunion | bigisunion | bigcoversexterior | bigcontainsexterior
------------------+------------------+------------------+------------+-------------------+---------------------
 f                     | t                    | f                    | t          | t                 | f

 --example demonstrating difference between contains and contains properly
 SELECT ST_GeometryType(geomA) As geomtype, ST_Contains(geomA,geomA) AS acontainsa, ST_ContainsProperly(geomA, geomA) AS acontainspropa,
 ST_Contains(geomA, ST_Boundary(geomA)) As acontainsba, ST_ContainsProperly(geomA, ST_Boundary(geomA)) As acontainspropba
 FROM (VALUES ( ST_Buffer(ST_Point(1,1), 5,1) ),
		  ( ST_MakeLine(ST_Point(1,1), ST_Point(-1,-1) ) ),
		  ( ST_Point(1,1) )
	) As foo(geomA);

  geomtype    | acontainsa | acontainspropa | acontainsba | acontainspropba
--------------+------------+----------------+-------------+-----------------
ST_Polygon    | t          | f              | f           | f
ST_LineString | t          | f              | f           | f
ST_Point      | t          | t              | f           | f
 </programlisting>
	  </refsection>

	  <refsection>
		<title>See Also</title>
		<para><xref linkend="ST_GeometryType" />, <xref linkend="ST_Boundary" />, <xref linkend="ST_Contains" />, <xref linkend="ST_Covers" />, <xref linkend="ST_CoveredBy" />, <xref linkend="ST_Equals"/>, <xref linkend="ST_Relate" />, <xref linkend="ST_Within"/></para>
	  </refsection>
 </refentry>

  <refentry id="ST_Covers">
	  <refnamediv>
		<refname>ST_Covers</refname>

		<refpurpose>Returns 1 (TRUE) if no point in Geometry B is outside
			Geometry A</refpurpose>
	  </refnamediv>

	  <refsynopsisdiv>
		<funcsynopsis>
		  <funcprototype>
			<funcdef>boolean <function>ST_Covers</function></funcdef>

			<paramdef><type>geometry </type>
			<parameter>geomA</parameter></paramdef>

			<paramdef><type>geometry </type>
			<parameter>geomB</parameter></paramdef>
		  </funcprototype>
		  <funcprototype>
			<funcdef>boolean <function>ST_Covers</function></funcdef>

			<paramdef><type>geography </type>
			<parameter>geogpolyA</parameter></paramdef>

			<paramdef><type>geography </type>
			<parameter>geogpointB</parameter></paramdef>
		  </funcprototype>
		</funcsynopsis>
	  </refsynopsisdiv>

	  <refsection>
		<title>Description</title>

		  <para>Returns 1 (TRUE) if no point in Geometry/Geography B is outside
			Geometry/Geography A</para>

		<important>
		  <para>Enhanced: 3.0.0 enabled support for <varname>GEOMETRYCOLLECTION</varname></para>
		</important>

		<important>
		  <para>Do not use this function with invalid geometries. You will get unexpected results.</para>
		</important>

		<para>This function call will automatically include a bounding box
			comparison that will make use of any indexes that are available on
			the geometries. To avoid index use, use the function
			_ST_Covers.</para>

		<para>Performed by the GEOS module</para>
    <para>Enhanced: 2.4.0 Support for polygon in polygon and line in polygon added for geography type</para>
		<para>Enhanced: 2.3.0 Enhancement to PIP short-circuit for geometry extended to support MultiPoints with few points. Prior versions only supported point in polygon.</para>
		<para>Availability: 1.5 - support for geography was introduced. </para>
		<para>Availability: 1.2.2</para>

		<para>NOTE: this is the "allowable" version that returns a
			boolean, not an integer.</para>

		<para>Not an OGC standard, but Oracle has it too.</para>
		<para>There are certain subtleties to ST_Contains and ST_Within that are not intuitively obvious.
			For details check out <ulink url="http://lin-ear-th-inking.blogspot.com/2007/06/subtleties-of-ogc-covers-spatial.html">Subtleties of OGC Covers, Contains, Within</ulink></para>
	  </refsection>

	  <refsection>
		<title>Examples</title>
			<para> Geometry example </para>
		  <programlisting>
	--a circle covering a circle
SELECT ST_Covers(smallc,smallc) As smallinsmall,
	ST_Covers(smallc, bigc) As smallcoversbig,
	ST_Covers(bigc, ST_ExteriorRing(bigc)) As bigcoversexterior,
	ST_Contains(bigc, ST_ExteriorRing(bigc)) As bigcontainsexterior
FROM (SELECT ST_Buffer(ST_GeomFromText('POINT(1 2)'), 10) As smallc,
	ST_Buffer(ST_GeomFromText('POINT(1 2)'), 20) As bigc) As foo;
	--Result
 smallinsmall | smallcoversbig | bigcoversexterior | bigcontainsexterior
--------------+----------------+-------------------+---------------------
 t            | f              | t                 | f
(1 row)	</programlisting>
		<para>Geeography Example</para>
		<programlisting>
-- a point with a 300 meter buffer compared to a point, a point and its 10 meter buffer
SELECT ST_Covers(geog_poly, geog_pt) As poly_covers_pt,
	ST_Covers(ST_Buffer(geog_pt,10), geog_pt) As buff_10m_covers_cent
	FROM (SELECT ST_Buffer(ST_GeogFromText('SRID=4326;POINT(-99.327 31.4821)'), 300) As geog_poly,
				ST_GeogFromText('SRID=4326;POINT(-99.33 31.483)') As geog_pt ) As foo;

 poly_covers_pt | buff_10m_covers_cent
----------------+------------------
 f              | t
		</programlisting>
	  </refsection>

	  <refsection>
		<title>See Also</title>
		<para><xref linkend="ST_Contains"/>, <xref linkend="ST_CoveredBy" />, <xref linkend="ST_Within"/></para>
	  </refsection>
 </refentry>

  <refentry id="ST_CoveredBy">
	  <refnamediv>
		<refname>ST_CoveredBy</refname>

		<refpurpose>Returns 1 (TRUE) if no point in Geometry/Geography A is outside
			Geometry/Geography B</refpurpose>
	  </refnamediv>

	  <refsynopsisdiv>
		<funcsynopsis>
		  <funcprototype>
			<funcdef>boolean <function>ST_CoveredBy</function></funcdef>

			<paramdef><type>geometry </type>
			<parameter>geomA</parameter></paramdef>

			<paramdef><type>geometry </type>
			<parameter>geomB</parameter></paramdef>
		  </funcprototype>

		  <funcprototype>
			<funcdef>boolean <function>ST_CoveredBy</function></funcdef>

			<paramdef><type>geography </type>
			<parameter>geogA</parameter></paramdef>

			<paramdef><type>geography </type>
			<parameter>geogB</parameter></paramdef>
		  </funcprototype>
		</funcsynopsis>
	  </refsynopsisdiv>

	  <refsection>
		<title>Description</title>

		  <para>Returns 1 (TRUE) if no point in Geometry/Geography A is outside
			Geometry/Geography B</para>

		<important>
		  <para>Enhanced: 3.0.0 enabled support for <varname>GEOMETRYCOLLECTION</varname></para>
		</important>

		<important>
		  <para>Do not use this function with invalid geometries. You will get unexpected results.</para>
		</important>
		<para>Performed by the GEOS module</para>
		<para>Availability: 1.2.2</para>
		<para>This function call will automatically include a bounding box
			comparison that will make use of any indexes that are available on
			the geometries. To avoid index use, use the function
			_ST_CoveredBy.</para>

		<para>NOTE: this is the "allowable" version that returns a
			boolean, not an integer.</para>

		<para>Not an OGC standard, but Oracle has it too.</para>
		<para>There are certain subtleties to ST_Contains and ST_Within that are not intuitively obvious.
			For details check out <ulink url="http://lin-ear-th-inking.blogspot.com/2007/06/subtleties-of-ogc-covers-spatial.html">Subtleties of OGC Covers, Contains, Within</ulink></para>
	  </refsection>

	  <refsection>
		<title>Examples</title>
		  <programlisting>
	--a circle coveredby a circle
SELECT ST_CoveredBy(smallc,smallc) As smallinsmall,
	ST_CoveredBy(smallc, bigc) As smallcoveredbybig,
	ST_CoveredBy(ST_ExteriorRing(bigc), bigc) As exteriorcoveredbybig,
	ST_Within(ST_ExteriorRing(bigc),bigc) As exeriorwithinbig
FROM (SELECT ST_Buffer(ST_GeomFromText('POINT(1 2)'), 10) As smallc,
	ST_Buffer(ST_GeomFromText('POINT(1 2)'), 20) As bigc) As foo;
	--Result
 smallinsmall | smallcoveredbybig | exteriorcoveredbybig | exeriorwithinbig
--------------+-------------------+----------------------+------------------
 t            | t                 | t                    | f
(1 row)	</programlisting>
	  </refsection>

	  <refsection>
		<title>See Also</title>
		<para><xref linkend="ST_Contains"/>, <xref linkend="ST_Covers" />, <xref linkend="ST_ExteriorRing"/>, <xref linkend="ST_Within"/></para>
	  </refsection>
 </refentry>

  <refentry id="ST_Crosses">
	<refnamediv>
	  <refname>ST_Crosses</refname>

	  <refpurpose>Returns <varname>TRUE</varname> if the supplied geometries have some, but not all,
	  interior points in common.</refpurpose>
	</refnamediv>

	<refsynopsisdiv>
	  <funcsynopsis>
		<funcprototype>
		  <funcdef>boolean <function>ST_Crosses</function></funcdef>

		  <paramdef><type>geometry </type><parameter>g1</parameter></paramdef>

		  <paramdef><type>geometry </type><parameter>g2</parameter></paramdef>
		</funcprototype>
	  </funcsynopsis>
	</refsynopsisdiv>

	<refsection>
	  <title>Description</title>

	  <para><function>ST_Crosses</function> takes two geometry objects and
	  returns <varname>TRUE</varname> if their intersection "spatially cross", that is, the
	  geometries have some, but not all interior points in common. The
	  intersection of the interiors of the geometries must not be the empty
	  set and must have a dimensionality less than the maximum dimension
	  of the two input geometries. Additionally, the intersection of the two
	  geometries must not equal either of the source geometries. Otherwise, it
	  returns <varname>FALSE</varname>.</para>

	  <para>In mathematical terms, this is expressed as:</para>

	  <remark>TODO: Insert appropriate MathML markup here or use a gif.
	  Simple HTML markup does not work well in both IE and Firefox.</remark>

	  <informalfigure>
		<mediaobject>
		  <imageobject>
			<imagedata fileref="images/st_crosses-math.gif" />
		  </imageobject>
		</mediaobject>
	  </informalfigure>

	  <para>The DE-9IM Intersection Matrix for the two geometries is:</para>

	  <itemizedlist>
		<listitem>
		  <para><markup>T*T******</markup> (for Point/Line, Point/Area, and
		  Line/Area situations)</para>
		</listitem>

		<listitem>
		  <para><markup>T*****T**</markup> (for Line/Point, Area/Point, and
		  Area/Line situations)</para>
		</listitem>

		<listitem>
		  <para><markup>0********</markup> (for Line/Line situations)</para>
		</listitem>
	  </itemizedlist>

	  <para>For any other combination of dimensions this predicate returns
	  false.</para>

	  <para>The OpenGIS Simple Features Specification defines this predicate
		only for Point/Line, Point/Area, Line/Line, and Line/Area situations.
		JTS / GEOS extends the definition to apply to Line/Point, Area/Point and
		Area/Line situations as well. This makes the relation
		symmetric.</para>

		<important>
		  <para>Enhanced: 3.0.0 enabled support for <varname>GEOMETRYCOLLECTION</varname></para>
		</important>

	<note>
	  <para>This function call will automatically include a bounding box
	  comparison that will make use of any indexes that are available on the
	  geometries.</para>
	</note>

	<para>&sfs_compliant; s2.1.13.3</para>
	<para>&sqlmm_compliant; SQL-MM 3: 5.1.29</para>
	</refsection>

	<refsection>
	  <title>Examples</title>

	  <para>The following illustrations all return <varname>TRUE</varname>.</para>

	  <informaltable>
		<tgroup cols="2">
		  <tbody>
			<row>
			  <entry><para><informalfigure>
				  <mediaobject>
					<imageobject>
					  <imagedata fileref="images/st_crosses01.png" />
					</imageobject>

					<caption><para><varname>MULTIPOINT</varname> / <varname>LINESTRING</varname></para></caption>
				  </mediaobject>
				</informalfigure></para></entry>

			  <entry><para><informalfigure>
				  <mediaobject>
					<imageobject>
					  <imagedata fileref="images/st_crosses02.png" />
					</imageobject>

					<caption><para><varname>MULTIPOINT</varname> / <varname>POLYGON</varname></para></caption>
				  </mediaobject>
				</informalfigure></para></entry>
			</row>

			<row>
			  <entry><para><informalfigure>
				  <mediaobject>
					<imageobject>
					  <imagedata fileref="images/st_crosses03.png" />
					</imageobject>

					<caption><para><varname>LINESTRING</varname> / <varname>POLYGON</varname></para></caption>
				  </mediaobject>
				</informalfigure></para></entry>

			  <entry><para><informalfigure>
				  <mediaobject>
					<imageobject>
					  <imagedata fileref="images/st_crosses04.png" />
					</imageobject>

					<caption><para><varname>LINESTRING</varname> / <varname>LINESTRING</varname></para></caption>
				  </mediaobject>
				</informalfigure></para></entry>
			</row>
		  </tbody>
		</tgroup>
	  </informaltable>

	  <para>Consider a situation where a user has two tables: a table of roads
	  and a table of highways.</para>

	  <informaltable>
		<tgroup cols="2">
		  <tbody>
			<row>
			  <entry><para> <informalexample>
				  <programlisting>CREATE TABLE roads (
  id serial NOT NULL,
  the_geom geometry,
  CONSTRAINT roads_pkey PRIMARY KEY (road_id)
);</programlisting>
				</informalexample> </para></entry>

			  <entry><para> <informalexample>
				  <programlisting>CREATE TABLE highways (
  id serial NOT NULL,
  the_gem geometry,
  CONSTRAINT roads_pkey PRIMARY KEY (road_id)
);</programlisting>
				</informalexample> </para></entry>
			</row>
		  </tbody>
		</tgroup>
	  </informaltable>

	  <para>To determine a list of roads that cross a highway, use a query
	  similiar to:</para>

	  <para><informalexample>
		  <programlisting>SELECT roads.id
FROM roads, highways
WHERE ST_Crosses(roads.the_geom, highways.the_geom);</programlisting>
		</informalexample></para>
	</refsection>
  </refentry>

  <refentry id="ST_LineCrossingDirection">
	<refnamediv>
	  <refname>ST_LineCrossingDirection</refname>

	  <refpurpose>Given 2 linestrings, returns a number between -3 and 3 denoting what kind of crossing behavior. 0 is no crossing.</refpurpose>
	</refnamediv>

	<refsynopsisdiv>
	  <funcsynopsis>
		<funcprototype>
		  <funcdef>integer <function>ST_LineCrossingDirection</function></funcdef>
		  <paramdef><type>geometry </type> <parameter>linestringA</parameter></paramdef>
		  <paramdef><type>geometry </type> <parameter>linestringB</parameter></paramdef>
		</funcprototype>
	  </funcsynopsis>
	</refsynopsisdiv>

	<refsection>
	  <title>Description</title>

	  <para>Given 2 linestrings, returns a number between -3 and 3 denoting what kind of crossing behavior. 0 is no crossing.  This is only supported for <varname>LINESTRING</varname></para>
	  <para>Definition of integer constants is as follows:
		   <itemizedlist>
				<listitem>
				  <para> 0: LINE NO CROSS</para>
				</listitem>
				<listitem>
				  <para>-1: LINE CROSS LEFT</para>
				</listitem>
				<listitem>
				  <para> 1: LINE CROSS RIGHT</para>
				</listitem>
				<listitem>
				  <para>-2: LINE MULTICROSS END LEFT</para>
				</listitem>
				<listitem>
					<para> 2: LINE MULTICROSS END RIGHT</para>
				</listitem>
				<listitem>
				  <para>-3: LINE MULTICROSS END SAME FIRST LEFT</para>
				</listitem>
				<listitem>
				  <para> 3: LINE MULTICROSS END SAME FIRST RIGHT</para>
				</listitem>
			</itemizedlist>
	  </para>
	  <para>Availability: 1.4</para>
	  <!-- optionally mention that this function uses indexes if appropriate -->

	</refsection>


	<refsection>
	  <title>Examples</title>
  <!-- TODO: We really badly need diagrams here and more examples -->
		<informaltable>
		  <tgroup cols="2">
			<tbody>
			  <row>
				<entry><para><informalfigure>
					<mediaobject>
					  <imageobject>
						<imagedata fileref="images/st_linecrossingdirection01.png" />
					  </imageobject>
					  <caption><para>Line 1 (green), Line 2 ball is start point,
					triangle are end points. Query below. </para></caption>
					</mediaobject>
				  </informalfigure>
				  <programlisting>
SELECT ST_LineCrossingDirection(foo.line1, foo.line2) As l1_cross_l2 ,
	  ST_LineCrossingDirection(foo.line2, foo.line1) As l2_cross_l1
FROM (
SELECT
 ST_GeomFromText('LINESTRING(25 169,89 114,40 70,86 43)') As line1,
 ST_GeomFromText('LINESTRING(171 154,20 140,71 74,161 53)') As line2
	) As foo;

 l1_cross_l2 | l2_cross_l1
-------------+-------------
           3 |          -3
				</programlisting>
			</para>
		</entry>

		<entry>
			<para><informalfigure>
				<mediaobject>
				  <imageobject>
					<imagedata fileref="images/st_linecrossingdirection02.png" />
				  </imageobject>
				  <caption><para>Line 1 (green), Line 2 (blue) ball is start point,
						triangle are end points. Query below.</para></caption>
				</mediaobject>
			  </informalfigure>
			  <programlisting>
SELECT ST_LineCrossingDirection(foo.line1, foo.line2) As l1_cross_l2 ,
	  ST_LineCrossingDirection(foo.line2, foo.line1) As l2_cross_l1
FROM (
 SELECT
  ST_GeomFromText('LINESTRING(25 169,89 114,40 70,86 43)') As line1,
  ST_GeomFromText('LINESTRING (171 154, 20 140, 71 74, 2.99 90.16)') As line2
) As foo;

 l1_cross_l2 | l2_cross_l1
-------------+-------------
           2 |          -2
				</programlisting>
			</para>
		</entry>
	  </row>
	  <row>
				<entry><para><informalfigure>
					<mediaobject>
					  <imageobject>
						<imagedata fileref="images/st_linecrossingdirection03.png" />
					  </imageobject>
					  <caption><para>Line 1 (green), Line 2 (blue) ball is start point,
					triangle are end points. Query below. </para></caption>
					</mediaobject>
				  </informalfigure>
				  <programlisting>
SELECT
	ST_LineCrossingDirection(foo.line1, foo.line2) As l1_cross_l2 ,
	ST_LineCrossingDirection(foo.line2, foo.line1) As l2_cross_l1
FROM (
 SELECT
  ST_GeomFromText('LINESTRING(25 169,89 114,40 70,86 43)') As line1,
  ST_GeomFromText('LINESTRING (20 140, 71 74, 161 53)') As line2
  ) As foo;

 l1_cross_l2 | l2_cross_l1
-------------+-------------
          -1 |          1
				</programlisting>
			</para>
		</entry>

		<entry>
			<para><informalfigure>
				<mediaobject>
				  <imageobject>
					<imagedata fileref="images/st_linecrossingdirection04.png" />
				  </imageobject>
				  <caption><para>Line 1 (green), Line 2 (blue) ball is start point,
						triangle are end points. Query below.</para></caption>
				</mediaobject>
			  </informalfigure>
			  <programlisting>
SELECT ST_LineCrossingDirection(foo.line1, foo.line2) As l1_cross_l2 ,
	  ST_LineCrossingDirection(foo.line2, foo.line1) As l2_cross_l1
FROM (SELECT
	ST_GeomFromText('LINESTRING(25 169,89 114,40 70,86 43)') As line1,
	ST_GeomFromText('LINESTRING(2.99 90.16,71 74,20 140,171 154)') As line2
	) As foo;

 l1_cross_l2 | l2_cross_l1
-------------+-------------
          -2 |          2
				</programlisting>
			</para>
		</entry>
	  </row>
	  </tbody>
	</tgroup>
</informaltable>

<programlisting>
SELECT s1.gid, s2.gid, ST_LineCrossingDirection(s1.the_geom, s2.the_geom)
	FROM streets s1 CROSS JOIN streets s2 ON (s1.gid != s2.gid AND s1.the_geom &amp;&amp; s2.the_geom )
WHERE ST_CrossingDirection(s1.the_geom, s2.the_geom) > 0;
</programlisting>
	</refsection>

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

	  <para><xref linkend="ST_Crosses" /></para>
	</refsection>
  </refentry>

  <refentry id="ST_Disjoint">
		<refnamediv>
			<refname>ST_Disjoint</refname>

			<refpurpose>Returns TRUE if the Geometries do not "spatially
			intersect" - if they do not share any space together.
			</refpurpose>
		</refnamediv>
		<refsynopsisdiv>
			<funcsynopsis>
				<funcprototype>
					<funcdef>boolean <function>ST_Disjoint</function></funcdef>
					<paramdef>
						<type>geometry</type>
						<parameter>A</parameter>
					</paramdef>
					<paramdef>
						<type>geometry</type>
						<parameter>B</parameter>
					</paramdef>
				</funcprototype>
			</funcsynopsis>
		</refsynopsisdiv>
		<refsection>
			<title>Description</title>
			<para>Overlaps, Touches, Within all imply geometries are not spatially disjoint.  If any of the aforementioned
				returns true, then the geometries are not spatially disjoint.
				Disjoint implies false for spatial intersection.</para>

		<important>
		  <para>Enhanced: 3.0.0 enabled support for <varname>GEOMETRYCOLLECTION</varname></para>
		</important>

			<para>Performed by the GEOS module</para>
			<note>
			  <para>This function call does not use indexes</para>

			</note>
			<note>
			  <para>NOTE: this is the "allowable" version that returns a
			boolean, not an integer.</para>
			</note>
			<para>&sfs_compliant; s2.1.1.2 //s2.1.13.3
			- a.Relate(b, 'FF*FF****')</para>
			<para>&sqlmm_compliant; SQL-MM 3: 5.1.26</para>
		</refsection>
		<refsection>
		<title>Examples</title>

		<programlisting>SELECT ST_Disjoint('POINT(0 0)'::geometry, 'LINESTRING ( 2 0, 0 2 )'::geometry);
 st_disjoint
---------------
 t
(1 row)
SELECT ST_Disjoint('POINT(0 0)'::geometry, 'LINESTRING ( 0 0, 0 2 )'::geometry);
 st_disjoint
---------------
 f
(1 row)
		</programlisting>
		</refsection>

		<refsection>
			<title>See Also</title>
			<para><xref linkend="ST_Intersects"/></para>
		</refsection>
	</refentry>

	<refentry id="ST_Equals">
	  <refnamediv>
		<refname>ST_Equals</refname>

		<refpurpose>Returns true if the given geometries represent the same geometry. Directionality
			is ignored.</refpurpose>
	  </refnamediv>

	  <refsynopsisdiv>
		<funcsynopsis>
		  <funcprototype>
			<funcdef>boolean <function>ST_Equals</function></funcdef>
			<paramdef><type>geometry </type> <parameter>A</parameter></paramdef>
			<paramdef><type>geometry </type> <parameter>B</parameter></paramdef>
		  </funcprototype>
		</funcsynopsis>
	  </refsynopsisdiv>

	  <refsection>
		<title>Description</title>

		<para>Returns TRUE if the given Geometries are "spatially
			equal". Use this for a 'better' answer than '='.
			Note by spatially equal we mean ST_Within(A,B) = true and ST_Within(B,A) = true and
			also mean ordering of points can be different but
			represent the same geometry structure.  To verify the order of points is consistent, use
			ST_OrderingEquals (it must be noted ST_OrderingEquals is a little more stringent than simply verifying order of
			points are the same).</para>

		<important>
		  <para>This function will return false if either geometry is invalid except in the case where they are binary equal.</para>
		</important>

		<important>
		  <para>Enhanced: 3.0.0 enabled support for <varname>GEOMETRYCOLLECTION</varname></para>
		</important>

		<para>&sfs_compliant; s2.1.1.2</para>
		<para>&sqlmm_compliant; SQL-MM 3: 5.1.24</para>
        <para>Changed: 2.2.0 Returns true even for invalid geometries if they are binary equal</para>
	  </refsection>

	  <refsection>
		<title>Examples</title>

		<programlisting>SELECT ST_Equals(ST_GeomFromText('LINESTRING(0 0, 10 10)'),
		ST_GeomFromText('LINESTRING(0 0, 5 5, 10 10)'));
 st_equals
-----------
 t
(1 row)

SELECT ST_Equals(ST_Reverse(ST_GeomFromText('LINESTRING(0 0, 10 10)')),
		ST_GeomFromText('LINESTRING(0 0, 5 5, 10 10)'));
 st_equals
-----------
 t
(1 row)
</programlisting>
	  </refsection>

	  <refsection>
		<title>See Also</title>

		<para><xref linkend="ST_IsValid"/>, <xref linkend="ST_OrderingEquals"/>, <xref linkend="ST_Reverse"/>, <xref linkend="ST_Within" /></para>
	  </refsection>

	</refentry>


	<refentry id="ST_Intersects">
		<refnamediv>
			<refname>ST_Intersects</refname>

			<refpurpose>Returns TRUE if the Geometries/Geography "spatially
			intersect in 2D" - (share any portion of space) and FALSE if they don't (they are Disjoint).
			For geography tolerance is 0.00001 meters (so any points that close are considered to intersect)
			</refpurpose>
		</refnamediv>
		<refsynopsisdiv>
			<funcsynopsis>
				<funcprototype>
					<funcdef>boolean <function>ST_Intersects</function></funcdef>
					<paramdef>
						<type>geometry</type>
						<parameter>geomA</parameter>
					</paramdef>
					<paramdef>
						<type>geometry</type>
						<parameter>geomB</parameter>
					</paramdef>
				</funcprototype>
				<funcprototype>
					<funcdef>boolean <function>ST_Intersects</function></funcdef>
					<paramdef>
						<type>geography</type>
						<parameter>geogA</parameter>
					</paramdef>
					<paramdef>
						<type>geography</type>
						<parameter>geogB</parameter>
					</paramdef>
				</funcprototype>
			</funcsynopsis>
		</refsynopsisdiv>
		<refsection>
			<title>Description</title>
			<para>If a geometry or geography shares any portion of space then they intersect.
			For geography -- tolerance is 0.00001 meters (so any points that are close are considered to intersect)</para>
			<para>ST_Overlaps, ST_Touches, ST_Within all imply spatial intersection.
			  If any of the aforementioned
				returns true, then the geometries also spatially intersect.
				Disjoint implies false for spatial intersection.</para>

			<para>Changed: 3.0.0 SFCGAL version removed.</para>
			<para>Enhanced: 2.5.0 Supports GEOMETRYCOLLECTION.</para>
			<para>Enhanced: 2.3.0 Enhancement to PIP short-circuit extended to support MultiPoints with few points. Prior versions only supported point in polygon.</para>
			<para>Performed by the GEOS module (for geometry), geography is native</para>
			<para>Availability: 1.5 support for geography was introduced.</para>
			<note>
			  <para>This function call will automatically include a bounding box
			  comparison that will make use of any indexes that are available on the
			  geometries.</para>
			</note>
			<note>
			  <para>For geography, this function has a distance tolerance of about 0.00001 meters and uses the sphere rather
				than spheroid calculation.</para>
			</note>
			<note>
			  <para>NOTE: this is the "allowable" version that returns a
			boolean, not an integer.</para>
			</note>
			<para>&sfs_compliant; s2.1.1.2 //s2.1.13.3
			  - ST_Intersects(g1, g2 ) --&gt; Not (ST_Disjoint(g1, g2 ))
			</para>
			<para>&sqlmm_compliant; SQL-MM 3: 5.1.27</para>
                        <para>&sfcgal_enhanced;</para>
		</refsection>
		<refsection>
		<title>Geometry Examples</title>
<programlisting>SELECT ST_Intersects('POINT(0 0)'::geometry, 'LINESTRING ( 2 0, 0 2 )'::geometry);
 st_intersects
---------------
 f
(1 row)
SELECT ST_Intersects('POINT(0 0)'::geometry, 'LINESTRING ( 0 0, 0 2 )'::geometry);
 st_intersects
---------------
 t
(1 row)

-- Look up in table. Make sure table has a GiST index on geometry column for faster lookup.
SELECT id, name FROM cities WHERE ST_Intersects(geom, 'SRID=4326;POLYGON((28 53,27.707 52.293,27 52,26.293 52.293,26 53,26.293 53.707,27 54,27.707 53.707,28 53))');
 id | name
----+-------
  2 | Minsk
(1 row)
</programlisting>
		</refsection>
		<refsection>
		<title>Geography Examples</title>
<programlisting>SELECT ST_Intersects(
		'SRID=4326;LINESTRING(-43.23456 72.4567,-43.23456 72.4568)'::geography,
		'SRID=4326;POINT(-43.23456 72.4567772)'::geography
		);

 st_intersects
---------------
t
</programlisting>
		</refsection>
		<refsection>
			<title>See Also</title>
			<para> <xref linkend="ST_3DIntersects" />, <xref linkend="ST_Disjoint"/></para>
		</refsection>
	</refentry>

	<refentry id="ST_OrderingEquals">
	  <refnamediv>
		<refname>ST_OrderingEquals</refname>

		<refpurpose>Returns true if the given geometries represent the same geometry
		and points are in the same directional order.</refpurpose>
	  </refnamediv>

	  <refsynopsisdiv>
		<funcsynopsis>
		  <funcprototype>
			<funcdef>boolean <function>ST_OrderingEquals</function></funcdef>
			<paramdef><type>geometry </type> <parameter>A</parameter></paramdef>
			<paramdef><type>geometry </type> <parameter>B</parameter></paramdef>
		  </funcprototype>
		</funcsynopsis>
	  </refsynopsisdiv>

	  <refsection>
		<title>Description</title>

		<para>ST_OrderingEquals compares two geometries and returns t (TRUE) if the
		  geometries are equal and the coordinates are in the same order;
		  otherwise it returns f (FALSE).</para>

		<note>
			<para>This function is implemented as per the ArcSDE SQL
		specification rather than SQL-MM.
		http://edndoc.esri.com/arcsde/9.1/sql_api/sqlapi3.htm#ST_OrderingEquals</para>
		</note>
		<para>&sqlmm_compliant; SQL-MM 3: 5.1.43</para>
	  </refsection>

	  <refsection>
		<title>Examples</title>

		<programlisting>SELECT ST_OrderingEquals(ST_GeomFromText('LINESTRING(0 0, 10 10)'),
		ST_GeomFromText('LINESTRING(0 0, 5 5, 10 10)'));
 st_orderingequals
-----------
 f
(1 row)

SELECT ST_OrderingEquals(ST_GeomFromText('LINESTRING(0 0, 10 10)'),
		ST_GeomFromText('LINESTRING(0 0, 0 0, 10 10)'));
 st_orderingequals
-----------
 t
(1 row)

SELECT ST_OrderingEquals(ST_Reverse(ST_GeomFromText('LINESTRING(0 0, 10 10)')),
		ST_GeomFromText('LINESTRING(0 0, 0 0, 10 10)'));
 st_orderingequals
-----------
 f
(1 row)
</programlisting>
		  </refsection>
		  <refsection>
			<title>See Also</title>
			<para><xref linkend="ST_Equals"/>, <xref linkend="ST_Reverse"/></para>
		  </refsection>
	</refentry>

	<refentry id="ST_Overlaps">
	  <refnamediv>
		<refname>ST_Overlaps</refname>

		<refpurpose>Returns TRUE if the Geometries share space, are of the same dimension, but are not completely contained by each other.</refpurpose>
	  </refnamediv>

	  <refsynopsisdiv>
		<funcsynopsis>
		  <funcprototype>
			<funcdef>boolean <function>ST_Overlaps</function></funcdef>
			<paramdef><type>geometry </type> <parameter>A</parameter></paramdef>
			<paramdef><type>geometry </type> <parameter>B</parameter></paramdef>
		  </funcprototype>
		</funcsynopsis>
	  </refsynopsisdiv>

	  <refsection>
		<title>Description</title>

		<para>Returns TRUE if the Geometries "spatially
			overlap".  By that we mean they intersect, but one does not completely contain another. </para>

		 <para>Performed by the GEOS module</para>

		<important>
		  <para>Enhanced: 3.0.0 enabled support for <varname>GEOMETRYCOLLECTION</varname></para>
		</important>

		<para>This function call will automatically include a bounding box
		comparison that will make use of any indexes that are available on
		the geometries. To avoid index use, use the function
		_ST_Overlaps.</para>

		<para>NOTE: this is the "allowable" version that returns a
			boolean, not an integer.</para>

		<para>&sfs_compliant; s2.1.1.2 // s2.1.13.3</para>
		<para>&sqlmm_compliant; SQL-MM 3: 5.1.32</para>
	  </refsection>

	  <refsection>
		<title>Examples</title>
          <para>The following illustrations all return <varname>TRUE</varname>.</para>

	  <informaltable>
		<tgroup cols="3">
		  <tbody>
			<row>
			  <entry><para><informalfigure>
				  <mediaobject>
					<imageobject>
					  <imagedata fileref="images/st_overlaps01.png" />
					</imageobject>
					<caption><para><varname>MULTIPOINT</varname> / <varname>MULTIPOINT</varname></para></caption>
				  </mediaobject>
				</informalfigure></para></entry>

			  <entry><para><informalfigure>
				  <mediaobject>
					<imageobject>
					  <imagedata fileref="images/st_overlaps02.png" />
					</imageobject>
					<caption><para><varname>LINESTRING</varname> / <varname>LINESTRING</varname></para></caption>
				  </mediaobject>
				</informalfigure></para></entry>
			  <entry><para><informalfigure>
				  <mediaobject>
					<imageobject>
					  <imagedata fileref="images/st_overlaps03.png" />
					</imageobject>
					<caption><para><varname>POLYGON</varname> / <varname>POLYGON</varname></para></caption>
				  </mediaobject>
				</informalfigure></para></entry>
			</row>
		  </tbody>
		</tgroup>
	  </informaltable>
		<programlisting>--a point on a line is contained by the line and is of a lower dimension, and therefore does not overlap the line
			nor crosses

SELECT ST_Overlaps(a,b) As a_overlap_b,
	ST_Crosses(a,b) As a_crosses_b,
		ST_Intersects(a, b) As a_intersects_b, ST_Contains(b,a) As b_contains_a
FROM (SELECT ST_GeomFromText('POINT(1 0.5)') As a, ST_GeomFromText('LINESTRING(1 0, 1 1, 3 5)')  As b)
	As foo

a_overlap_b | a_crosses_b | a_intersects_b | b_contains_a
------------+-------------+----------------+--------------
f           | f           | t              | t

--a line that is partly contained by circle, but not fully is defined as intersecting and crossing,
-- but since of different dimension it does not overlap
SELECT ST_Overlaps(a,b) As a_overlap_b, ST_Crosses(a,b) As a_crosses_b,
	ST_Intersects(a, b) As a_intersects_b,
	ST_Contains(a,b) As a_contains_b
FROM (SELECT ST_Buffer(ST_GeomFromText('POINT(1 0.5)'), 3)  As a, ST_GeomFromText('LINESTRING(1 0, 1 1, 3 5)')  As b)
	As foo;

 a_overlap_b | a_crosses_b | a_intersects_b | a_contains_b
-------------+-------------+----------------+--------------
 f           | t           | t              | f

 -- a 2-dimensional bent hot dog (aka buffered line string) that intersects a circle,
 --	but is not fully contained by the circle is defined as overlapping since they are of the same dimension,
--	but it does not cross, because the intersection of the 2 is of the same dimension
--	as the maximum dimension of the 2

SELECT ST_Overlaps(a,b) As a_overlap_b, ST_Crosses(a,b) As a_crosses_b, ST_Intersects(a, b) As a_intersects_b,
ST_Contains(b,a) As b_contains_a,
ST_Dimension(a) As dim_a, ST_Dimension(b) as dim_b, ST_Dimension(ST_Intersection(a,b)) As dima_intersection_b
FROM (SELECT ST_Buffer(ST_GeomFromText('POINT(1 0.5)'), 3)  As a,
	ST_Buffer(ST_GeomFromText('LINESTRING(1 0, 1 1, 3 5)'),0.5)  As b)
	As foo;

 a_overlap_b | a_crosses_b | a_intersects_b | b_contains_a | dim_a | dim_b | dima_intersection_b
-------------+-------------+----------------+--------------+-------+-------+---------------------
 t           | f           | t              | f            |     2 |     2 |              2
</programlisting>


	  </refsection>

	  <refsection>
		<title>See Also</title>

		<para><xref linkend="ST_Contains"/>, <xref linkend="ST_Crosses"/>, <xref linkend="ST_Dimension"/>, <xref linkend="ST_Intersects"/></para>
	  </refsection>
	</refentry>

	<refentry id="ST_PointInsideCircle">
	  <refnamediv>
		<refname>ST_PointInsideCircle</refname>

		<refpurpose>Is the point geometry inside the circle defined by center_x, center_y, radius</refpurpose>
	  </refnamediv>

	  <refsynopsisdiv>
		<funcsynopsis>
		  <funcprototype>
			<funcdef>boolean <function>ST_PointInsideCircle</function></funcdef>
			<paramdef><type>geometry </type> <parameter>a_point</parameter></paramdef>
			<paramdef><type>float </type> <parameter>center_x</parameter></paramdef>
			<paramdef><type>float </type> <parameter>center_y</parameter></paramdef>
			<paramdef><type>float </type> <parameter>radius</parameter></paramdef>
		  </funcprototype>
		</funcsynopsis>
	  </refsynopsisdiv>

	  <refsection>
		<title>Description</title>

		<para>The syntax for this functions is
			ST_PointInsideCircle(&lt;geometry&gt;,&lt;circle_center_x&gt;,&lt;circle_center_y&gt;,&lt;radius&gt;).
			Returns the true if the geometry is a point and is inside the
			circle. Returns false otherwise.</para>
		<note><para>This only works for points as the name suggests</para></note>

		<para>Availability: 1.2</para>
		<para>Changed: 2.2.0 In prior versions this used to be called ST_Point_Inside_Circle</para>
	  </refsection>


	  <refsection>
		<title>Examples</title>

		<programlisting>SELECT ST_PointInsideCircle(ST_Point(1,2), 0.5, 2, 3);
 st_pointinsidecircle
------------------------
 t
</programlisting>
	  </refsection>

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

		<para><xref linkend="ST_DWithin" /></para>
	  </refsection>
	</refentry>

	<refentry id="ST_Relate">
		<refnamediv>
			<refname>ST_Relate</refname>

			<refpurpose>Returns true if this Geometry is spatially related to
					anotherGeometry, by testing for intersections between the
					Interior, Boundary and Exterior of the two geometries as specified
					by the values in the intersectionMatrixPattern.  If no intersectionMatrixPattern
					is passed in, then returns the maximum intersectionMatrixPattern that relates the 2 geometries.</refpurpose>
		</refnamediv>

		<refsynopsisdiv>
			<funcsynopsis>
			  <funcprototype>
				<funcdef>boolean <function>ST_Relate</function></funcdef>
				<paramdef><type>geometry </type> <parameter>geomA</parameter></paramdef>
				<paramdef><type>geometry </type> <parameter>geomB</parameter></paramdef>
				<paramdef><type>text </type> <parameter>intersectionMatrixPattern</parameter></paramdef>
			  </funcprototype>

			  <funcprototype>
				<funcdef>text <function>ST_Relate</function></funcdef>
				<paramdef><type>geometry </type> <parameter>geomA</parameter></paramdef>
				<paramdef><type>geometry </type> <parameter>geomB</parameter></paramdef>
			  </funcprototype>

			  <funcprototype>
				<funcdef>text <function>ST_Relate</function></funcdef>
				<paramdef><type>geometry </type> <parameter>geomA</parameter></paramdef>
				<paramdef><type>geometry </type> <parameter>geomB</parameter></paramdef>
				<paramdef><type>integer </type> <parameter>BoundaryNodeRule</parameter></paramdef>
			  </funcprototype>
			</funcsynopsis>
		</refsynopsisdiv>

		<refsection>
			<title>Description</title>

			<para>Version 1: Takes geomA, geomB, intersectionMatrix and Returns 1 (TRUE) if this Geometry is spatially related to
					anotherGeometry, by testing for intersections between the
					Interior, Boundary and Exterior of the two geometries as specified
					by the values in the <ulink url="http://en.wikipedia.org/wiki/DE-9IM">DE-9IM matrix pattern</ulink>.</para>

			<para>This is especially useful for testing compound checks of intersection, crosses, etc in one step.</para>

			<note><para>This is the "allowable" version that returns a
			boolean, not an integer.  This is defined in OGC spec</para></note>

			<note><para>This DOES NOT automagically include an index call.  The reason for that
				is some relationships are anti e.g. Disjoint.  If you are
				using a relationship pattern that requires intersection, then include the &amp;&amp;
				index call.</para></note>

			<para>Version 2: Takes geomA and geomB and returns the <xref linkend="DE-9IM" /></para>

			<para>Version 3: same as version 2, but allows to specify a boundary node rule (1:OGC/MOD2, 2:Endpoint, 3:MultivalentEndpoint, 4:MonovalentEndpoint)</para>

			<important>
			  <para>Enhanced: 3.0.0 enabled support for <varname>GEOMETRYCOLLECTION</varname></para>
			</important>

			<para>not in OGC spec, but implied. see s2.1.13.2</para>
			<para>&sfs_compliant; s2.1.1.2 // s2.1.13.3</para>
			<para>&sqlmm_compliant; SQL-MM 3: 5.1.25</para>
			<para>Performed by the GEOS module</para>
			<para>Enhanced: 2.0.0 - added support for specifying boundary node rule.</para>
		</refsection>


		<refsection>
		<title>Examples</title>
		<programlisting>
--Find all compounds that intersect and not touch a poly (interior intersects)
SELECT l.* , b.name As poly_name
	FROM polys As b
INNER JOIN compounds As l
ON (p.the_geom &amp;&amp; b.the_geom
AND ST_Relate(l.the_geom, b.the_geom,'T********'));

SELECT ST_Relate(ST_GeometryFromText('POINT(1 2)'), ST_Buffer(ST_GeometryFromText('POINT(1 2)'),2));
st_relate
-----------
0FFFFF212

SELECT ST_Relate(ST_GeometryFromText('LINESTRING(1 2, 3 4)'), ST_GeometryFromText('LINESTRING(5 6, 7 8)'));
st_relate
-----------
FF1FF0102


SELECT ST_Relate(ST_GeometryFromText('POINT(1 2)'), ST_Buffer(ST_GeometryFromText('POINT(1 2)'),2), '0FFFFF212');
st_relate
-----------
t

SELECT ST_Relate(ST_GeometryFromText('POINT(1 2)'), ST_Buffer(ST_GeometryFromText('POINT(1 2)'),2), '*FF*FF212');
st_relate
-----------
t
		</programlisting>
	</refsection>

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

		<para><xref linkend="ST_Crosses" />, <xref linkend="DE-9IM" />, <xref linkend="ST_Disjoint" />, <xref linkend="ST_Intersects" />, <xref linkend="ST_Touches" /></para>
	</refsection>
</refentry>

<refentry id="ST_RelateMatch">
	<refnamediv>
		<refname>ST_RelateMatch</refname>

		<refpurpose>Returns true if intersectionMattrixPattern1 implies intersectionMatrixPattern2</refpurpose>
	</refnamediv>

	<refsynopsisdiv>
		<funcsynopsis>
		  <funcprototype>
			<funcdef>boolean <function>ST_RelateMatch</function></funcdef>
			<paramdef><type>text </type> <parameter>intersectionMatrix</parameter></paramdef>
			<paramdef><type>text </type> <parameter>intersectionMatrixPattern</parameter></paramdef>
		  </funcprototype>
		</funcsynopsis>
	</refsynopsisdiv>

	<refsection>
		<title>Description</title>

		<para> Takes intersectionMatrix and intersectionMatrixPattern and Returns true if the intersectionMatrix satisfies
		the intersectionMatrixPattern. For more information refer to <xref linkend="DE-9IM" />.	</para>
		<para>Performed by the GEOS module</para>
		<para>Availability: 2.0.0</para>
	</refsection>


	<refsection>
		<title>Examples</title>
		<programlisting>
SELECT ST_RelateMatch('101202FFF', 'TTTTTTFFF') ;
-- result --
t
--example of common intersection matrix patterns and example matrices
-- comparing relationships of involving one invalid geometry and ( a line and polygon that intersect at interior and boundary)
SELECT mat.name, pat.name, ST_RelateMatch(mat.val, pat.val) As satisfied
    FROM
        ( VALUES ('Equality', 'T1FF1FFF1'),
                ('Overlaps', 'T*T***T**'),
                ('Within', 'T*F**F***'),
                ('Disjoint', 'FF*FF****') As pat(name,val)
        CROSS JOIN
            (	VALUES ('Self intersections (invalid)', '111111111'),
                    ('IE2_BI1_BB0_BE1_EI1_EE2', 'FF2101102'),
                    ('IB1_IE1_BB0_BE0_EI2_EI1_EE2', 'F11F00212')
            ) As mat(name,val);

		</programlisting>
	</refsection>

	<!-- Optionally add a "See Also" section -->
	<refsection>
		<title>See Also</title>
		<para><xref linkend="DE-9IM" />, <xref linkend="ST_Relate" /></para>
	</refsection>
</refentry>

	<refentry id="ST_Touches">
	  <refnamediv>
		<refname>ST_Touches</refname>

		<refpurpose>Returns <varname>TRUE</varname> if the geometries have at least one point in common,
		but their interiors do not intersect.</refpurpose>
	  </refnamediv>

	  <refsynopsisdiv>
		<funcsynopsis>
		  <funcprototype>
			<funcdef>boolean <function>ST_Touches</function></funcdef>

			<paramdef><type>geometry </type>
			<parameter>g1</parameter></paramdef>

			<paramdef><type>geometry </type>
			<parameter>g2</parameter></paramdef>
		  </funcprototype>
		</funcsynopsis>
	  </refsynopsisdiv>

	  <refsection>
		<title>Description</title>

		<para>Returns <varname>TRUE</varname> if the only points in common between
		<parameter>g1</parameter> and <parameter>g2</parameter> lie in the union of the
		boundaries of <parameter>g1</parameter> and <parameter>g2</parameter>.
		The <function>ST_Touches</function> relation applies
		to all Area/Area, Line/Line, Line/Area, Point/Area and Point/Line pairs of relationships,
		but <emphasis>not</emphasis> to the Point/Point pair.</para>

		<para>In mathematical terms, this predicate is expressed as:</para>

		<informalfigure>
		  <mediaobject>
			<imageobject>
			  <imagedata fileref="images/st_touches-math.gif" />
			</imageobject>
		  </mediaobject>
		</informalfigure>

		<para>The allowable DE-9IM Intersection Matrices for the two geometries are:</para>

		<itemizedlist>
		  <listitem>
			<para><markup>FT*******</markup></para>
		  </listitem>

		  <listitem>
			<para><markup>F**T*****</markup></para>
		  </listitem>

		  <listitem>
			<para><markup>F***T****</markup></para>
		  </listitem>
		</itemizedlist>

		<important>
		  <para>Enhanced: 3.0.0 enabled support for <varname>GEOMETRYCOLLECTION</varname></para>
		</important>

		<note>
		  <para>This function call will automatically include a bounding box
		  comparison that will make use of any indexes that are available on
		  the geometries.  To avoid using an index, use <function>_ST_Touches</function> instead.</para>
		</note>

		<para>&sfs_compliant; s2.1.1.2 // s2.1.13.3</para>
		<para>&sqlmm_compliant; SQL-MM 3: 5.1.28</para>
	  </refsection>

	  <refsection>
		<title>Examples</title>

		<para>The <function>ST_Touches</function> predicate returns <varname>TRUE</varname> in all the following illustrations.</para>
		<informaltable>
		  <tgroup cols="3">
			<tbody>
			  <row>
				<entry><para><informalfigure>
					<mediaobject>
					  <imageobject>
						<imagedata fileref="images/st_touches01.png" />
					  </imageobject>

					  <caption><para><varname>POLYGON</varname> / <varname>POLYGON</varname></para></caption>
					</mediaobject>
				  </informalfigure></para></entry>

				<entry><para><informalfigure>
					<mediaobject>
					  <imageobject>
						<imagedata fileref="images/st_touches02.png" />
					  </imageobject>

					  <caption><para><varname>POLYGON</varname> / <varname>POLYGON</varname></para></caption>
					</mediaobject>
				  </informalfigure></para></entry>

				<entry><para><informalfigure>
					<mediaobject>
					  <imageobject>
						<imagedata fileref="images/st_touches03.png" />
					  </imageobject>

					  <caption><para><varname>POLYGON</varname> / <varname>LINESTRING</varname></para></caption>
					</mediaobject>
				  </informalfigure></para></entry>
			  </row>
			  <row>
				<entry><para><informalfigure>
					<mediaobject>
					  <imageobject>
						<imagedata fileref="images/st_touches04.png" />
					  </imageobject>

					  <caption><para><varname>LINESTRING</varname> / <varname>LINESTRING</varname></para></caption>
					</mediaobject>
				  </informalfigure></para></entry>

				<entry><para><informalfigure>
					<mediaobject>
					  <imageobject>
						<imagedata fileref="images/st_touches05.png" />
					  </imageobject>

					  <caption><para><varname>LINESTRING</varname> / <varname>LINESTRING</varname></para></caption>
					</mediaobject>
				  </informalfigure></para></entry>

				<entry><para><informalfigure>
					<mediaobject>
					  <imageobject>
						<imagedata fileref="images/st_touches06.png" />
					  </imageobject>

					  <caption><para><varname>POLYGON</varname> / <varname>POINT</varname></para></caption>
					</mediaobject>
				  </informalfigure></para></entry>
			  </row>
			</tbody>
		  </tgroup>
		</informaltable>

		<programlisting>SELECT ST_Touches('LINESTRING(0 0, 1 1, 0 2)'::geometry, 'POINT(1 1)'::geometry);
 st_touches
------------
 f
(1 row)

SELECT ST_Touches('LINESTRING(0 0, 1 1, 0 2)'::geometry, 'POINT(0 2)'::geometry);
 st_touches
------------
 t
(1 row)</programlisting>
	  </refsection>
	</refentry>

	<refentry id="ST_Within">
	  <refnamediv>
		<refname>ST_Within</refname>

		<refpurpose>Returns true if the geometry A is completely inside geometry B</refpurpose>
	  </refnamediv>

	  <refsynopsisdiv>
		<funcsynopsis>
		  <funcprototype>
			<funcdef>boolean <function>ST_Within</function></funcdef>

			<paramdef><type>geometry </type>
			<parameter>A</parameter></paramdef>

			<paramdef><type>geometry </type>
			<parameter>B</parameter></paramdef>
		  </funcprototype>
		</funcsynopsis>
	  </refsynopsisdiv>

	  <refsection>
		<title>Description</title>

		<para>Returns TRUE if geometry A is completely inside geometry B. For this function to make
		sense, the source geometries must both be of the same coordinate projection,
		having the same SRID.  It is a given that if ST_Within(A,B) is true and ST_Within(B,A) is true, then
		the two geometries are considered spatially equal.</para>

		<para>Performed by the GEOS module</para>

		<para>Enhanced: 2.3.0 Enhancement to PIP short-circuit for geometry extended to support MultiPoints with few points. Prior versions only supported point in polygon.</para>

		<important>
		  <para>Enhanced: 3.0.0 enabled support for <varname>GEOMETRYCOLLECTION</varname></para>
		</important>

		<important>
		  <para>Do not use this function with invalid geometries. You will get unexpected results.</para>
		</important>

		<para>This function call will automatically include a bounding box
			comparison that will make use of any indexes that are available on
			the geometries. To avoid index use, use the function
			_ST_Within.</para>

		<para>NOTE: this is the "allowable" version that returns a
			boolean, not an integer.</para>

		<para>&sfs_compliant; s2.1.1.2 // s2.1.13.3
		  - a.Relate(b, 'T*F**F***')
		</para>
		<para>&sqlmm_compliant; SQL-MM 3: 5.1.30</para>
	  </refsection>

	  <refsection>
		<title>Examples</title>
		  <programlisting>
--a circle within a circle
SELECT ST_Within(smallc,smallc) As smallinsmall,
	ST_Within(smallc, bigc) As smallinbig,
	ST_Within(bigc,smallc) As biginsmall,
	ST_Within(ST_Union(smallc, bigc), bigc) as unioninbig,
	ST_Within(bigc, ST_Union(smallc, bigc)) as biginunion,
	ST_Equals(bigc, ST_Union(smallc, bigc)) as bigisunion
FROM
(
SELECT ST_Buffer(ST_GeomFromText('POINT(50 50)'), 20) As smallc,
	ST_Buffer(ST_GeomFromText('POINT(50 50)'), 40) As bigc) As foo;
--Result
 smallinsmall | smallinbig | biginsmall | unioninbig | biginunion | bigisunion
--------------+------------+------------+------------+------------+------------
 t            | t          | f          | t          | t          | t
(1 row)
		</programlisting>

		<para><inlinemediaobject>
		<imageobject>
		  <imagedata fileref="images/st_within01.png" />
		</imageobject>
	  </inlinemediaobject> </para>
	  </refsection>

	  <refsection>
		<title>See Also</title>
		<para><xref linkend="ST_Contains"/>, <xref linkend="ST_Equals"/>, <xref linkend="ST_IsValid"/></para>
	  </refsection>
	</refentry>

    </sect2>
	<!-- ==============================================================================  -->

		<sect2>
		<title>Distance Relationships</title>

	<refentry id="ST_3DDWithin">
	  <refnamediv>
		<refname>ST_3DDWithin</refname>

		<refpurpose>For 3d (z) geometry type Returns true if two geometries 3d distance is within number of units. </refpurpose>
	  </refnamediv>
	  <refsynopsisdiv>
		<funcsynopsis>
		  <funcprototype>
			<funcdef>boolean <function>ST_3DDWithin</function></funcdef>

			<paramdef><type>geometry </type>
			<parameter>g1</parameter></paramdef>

			<paramdef><type>geometry </type>
			<parameter>g2</parameter></paramdef>

			<paramdef><type>double precision </type>
			<parameter>distance_of_srid</parameter></paramdef>
		  </funcprototype>
		</funcsynopsis>
	  </refsynopsisdiv>

	  <refsection>
		<title>Description</title>

		<para>For geometry type returns true if the 3d distance between two objects is within distance_of_srid specified
		projected units (spatial ref units). </para>

        <para>&Z_support;</para>
        <!-- Optionally mention supports Polyhedral Surface  -->
        <para>&P_support;</para>
		<para>&sqlmm_compliant; SQL-MM ?</para>

		<para>Availability: 2.0.0</para>
	  </refsection>

	  <refsection>
		<title>Examples</title>

		<programlisting>
-- Geometry example - units in meters (SRID: 2163 US National Atlas Equal area) (3D point and line compared 2D point and line)
-- Note: currently no vertical datum support so Z is not transformed and assumed to be same units as final.
SELECT ST_3DDWithin(
			ST_Transform(ST_GeomFromEWKT('SRID=4326;POINT(-72.1235 42.3521 4)'),2163),
			ST_Transform(ST_GeomFromEWKT('SRID=4326;LINESTRING(-72.1260 42.45 15, -72.123 42.1546 20)'),2163),
			126.8
		) As within_dist_3d,
ST_DWithin(
			ST_Transform(ST_GeomFromEWKT('SRID=4326;POINT(-72.1235 42.3521 4)'),2163),
			ST_Transform(ST_GeomFromEWKT('SRID=4326;LINESTRING(-72.1260 42.45 15, -72.123 42.1546 20)'),2163),
			126.8
		) As within_dist_2d;

 within_dist_3d | within_dist_2d
----------------+----------------
 f              | t
</programlisting>
	  </refsection>

	  <refsection>
		<title>See Also</title>

		<para><xref linkend="ST_3DDistance"/>, <xref linkend="ST_Distance"/>, <xref linkend="ST_DWithin"/>, <xref linkend="ST_3DMaxDistance" />, <xref linkend="ST_Transform" /></para>
	  </refsection>
	</refentry>

<refentry id="ST_3DDFullyWithin">
	  <refnamediv>
		<refname>ST_3DDFullyWithin</refname>

		<refpurpose>Returns true if all of the 3D geometries are within the specified
		distance of one another. </refpurpose>
	  </refnamediv>

	  <refsynopsisdiv>
		<funcsynopsis>
		  <funcprototype>
			<funcdef>boolean <function>ST_3DDFullyWithin</function></funcdef>

			<paramdef><type>geometry </type>
			<parameter>g1</parameter></paramdef>

			<paramdef><type>geometry </type>
			<parameter>g2</parameter></paramdef>

			<paramdef><type>double precision </type>
			<parameter>distance</parameter></paramdef>
		  </funcprototype>
		</funcsynopsis>
	  </refsynopsisdiv>

	  <refsection>
		<title>Description</title>

		<para>Returns true if the 3D geometries are fully within the specified distance
		of one another. The distance is specified in units defined by the
		spatial reference system of the geometries.  For this function to make
		sense, the source geometries must both be of the same coordinate projection,
		having the same SRID.</para>

		<note>
		  <para>This function call will automatically include a bounding box
		  comparison that will make use of any indexes that are available on
		  the geometries.</para>
		</note>

		<para>Availability: 2.0.0</para>
        <para>&Z_support;</para>
        <!-- Optionally mention supports Polyhedral Surface  -->
        <para>&P_support;</para>

	  </refsection>

	  <refsection>
		<title>Examples</title>
		<programlisting>
		-- This compares the difference between fully within and distance within as well
		-- as the distance fully within for the 2D footprint of the line/point vs. the 3d fully within
		SELECT ST_3DDFullyWithin(geom_a, geom_b, 10) as D3DFullyWithin10, ST_3DDWithin(geom_a, geom_b, 10) as D3DWithin10,
	ST_DFullyWithin(geom_a, geom_b, 20) as D2DFullyWithin20,
	ST_3DDFullyWithin(geom_a, geom_b, 20) as D3DFullyWithin20 from
		(select ST_GeomFromEWKT('POINT(1 1 2)') as geom_a,
		ST_GeomFromEWKT('LINESTRING(1 5 2, 2 7 20, 1 9 100, 14 12 3)') as geom_b) t1;
 d3dfullywithin10 | d3dwithin10 | d2dfullywithin20 | d3dfullywithin20
------------------+-------------+------------------+------------------
 f                | t           | t                | f </programlisting>
	  </refsection>

	  <refsection>
		<title>See Also</title>

		<para><xref linkend="ST_3DMaxDistance"/>, <xref linkend="ST_3DDWithin"/>, <xref linkend="ST_DWithin"/>, <xref linkend="ST_DFullyWithin"/></para>
	  </refsection>
	</refentry>

	<refentry id="ST_DFullyWithin">
	  <refnamediv>
		<refname>ST_DFullyWithin</refname>

		<refpurpose>Returns true if all of the geometries are within the specified
		distance of one another</refpurpose>
	  </refnamediv>

	  <refsynopsisdiv>
		<funcsynopsis>
		  <funcprototype>
			<funcdef>boolean <function>ST_DFullyWithin</function></funcdef>

			<paramdef><type>geometry </type>
			<parameter>g1</parameter></paramdef>

			<paramdef><type>geometry </type>
			<parameter>g2</parameter></paramdef>

			<paramdef><type>double precision </type>
			<parameter>distance</parameter></paramdef>
		  </funcprototype>
		</funcsynopsis>
	  </refsynopsisdiv>

	  <refsection>
		<title>Description</title>

		<para>Returns true if the geometries is fully within the specified distance
		of one another. The distance is specified in units defined by the
		spatial reference system of the geometries.  For this function to make
		sense, the source geometries must both be of the same coordinate projection,
		having the same SRID.</para>

		<note>
		  <para>This function call will automatically include a bounding box
		  comparison that will make use of any indexes that are available on
		  the geometries.</para>
		</note>

		<para>Availability: 1.5.0</para>
	  </refsection>

	  <refsection>
		<title>Examples</title>
		<programlisting>postgis=# SELECT ST_DFullyWithin(geom_a, geom_b, 10) as DFullyWithin10, ST_DWithin(geom_a, geom_b, 10) as DWithin10, ST_DFullyWithin(geom_a, geom_b, 20) as DFullyWithin20 from
		(select ST_GeomFromText('POINT(1 1)') as geom_a,ST_GeomFromText('LINESTRING(1 5, 2 7, 1 9, 14 12)') as geom_b) t1;

-----------------
 DFullyWithin10 | DWithin10 | DFullyWithin20 |
---------------+----------+---------------+
 f             | t        | t             |  </programlisting>
	  </refsection>

	  <refsection>
		<title>See Also</title>

		<para><xref linkend="ST_MaxDistance"/>, <xref linkend="ST_DWithin"/></para>
	  </refsection>
	</refentry>

	<refentry id="ST_DWithin">
	  <refnamediv>
		<refname>ST_DWithin</refname>

		<refpurpose>Returns true if the geometries are within the specified
		distance of one another. For geometry units are in those of spatial reference and for geography units are in meters and measurement is
		defaulted to use_spheroid=true (measure around spheroid), for faster check, use_spheroid=false to measure along sphere.</refpurpose>
	  </refnamediv>

	  <refsynopsisdiv>
		<funcsynopsis>
		  <funcprototype>
				<funcdef>boolean <function>ST_DWithin</function></funcdef>
				<paramdef><type>geometry </type>
				<parameter>g1</parameter></paramdef>

				<paramdef><type>geometry </type>
				<parameter>g2</parameter></paramdef>

				<paramdef><type>double precision </type>
				<parameter>distance_of_srid</parameter></paramdef>
		  </funcprototype>

		  <funcprototype>
				<funcdef>boolean <function>ST_DWithin</function></funcdef>
				<paramdef><type>geography </type>
				<parameter>gg1</parameter></paramdef>

				<paramdef><type>geography </type>
				<parameter>gg2</parameter></paramdef>

				<paramdef><type>double precision </type>
				<parameter>distance_meters</parameter></paramdef>

				<paramdef choice="opt"><type>boolean </type>
				<parameter>use_spheroid</parameter></paramdef>
		  </funcprototype>
		</funcsynopsis>
	  </refsynopsisdiv>

	  <refsection>
		<title>Description</title>

		<para>Returns true if the geometries are within the specified distance
		of one another.</para>

		<para>For <type>geometry</type>: The distance is specified in units defined by the
		spatial reference system of the geometries.  For this function to make
		sense, the source geometries must both be of the same coordinate projection,
		having the same SRID.</para>

		<para>For <type>geography</type> units are in meters and measurement is
		defaulted to <varname>use_spheroid</varname>=true, for faster check, <varname>use_spheroid</varname>=false to measure along sphere.
		</para>

		<note>
		  <para>This function call will automatically include a bounding box
		  comparison that will make use of any indexes that are available on
		  the geometries.</para>
		</note>

		<note>
		  <para>Prior to 1.3, ST_Expand was commonly used in conjunction with &amp;&amp; and ST_Distance to
		  achieve the same effect and in pre-1.3.4 this function was basically short-hand for that construct.
		  From 1.3.4, ST_DWithin uses a more short-circuit distance function which should make it more efficient
		  than prior versions for larger buffer regions.</para>
		</note>

		<note><para>Use ST_3DDWithin if you have 3D geometries.</para></note>

		<para>&sfs_compliant;</para>
		<para>Availability: 1.5.0 support for geography was introduced</para>
		<para>Enhanced: 2.1.0 improved speed for geography. See <ulink url="http://blog.opengeo.org/2012/07/12/making-geography-faster/">Making Geography faster</ulink> for details.</para>
		<para>Enhanced: 2.1.0 support for curved geometries was introduced.</para>
	  </refsection>

	  <refsection>
		<title>Examples</title>
		  <programlisting>
-- Find the nearest hospital to each school
-- that is within 3000 units of the school.
--  We do an ST_DWithin search to utilize indexes to limit our search list
--  that the non-indexable ST_Distance needs to process
-- If the units of the spatial reference is meters then units would be meters
SELECT DISTINCT ON (s.gid) s.gid, s.school_name, s.geom, h.hospital_name
	FROM schools s
		LEFT JOIN hospitals h ON ST_DWithin(s.the_geom, h.geom, 3000)
	ORDER BY s.gid, ST_Distance(s.geom, h.geom);

-- The schools with no close hospitals
-- Find all schools with no hospital within 3000 units
-- away from the school.  Units is in units of spatial ref (e.g. meters, feet, degrees)
SELECT s.gid, s.school_name
	FROM schools s
		LEFT JOIN hospitals h ON ST_DWithin(s.geom, h.geom, 3000)
	WHERE h.gid IS NULL;

-- Find broadcasting towers that receiver with limited range can receive.
-- Data is geometry in Spherical Mercator (SRID=3857), ranges are approximate.

-- Create geometry index that will check proximity limit of user to tower
CREATE INDEX ON broadcasting_towers using gist (geom);

-- Create geometry index that will check proximity limit of tower to user
CREATE INDEX ON broadcasting_towers using gist (ST_Expand(geom, sending_range));

-- Query towers that 4-kilometer receiver in Minsk Hackerspace can get
-- Note: two conditions, because shorter LEAST(b.sending_range, 4000) will not use index.
SELECT b.tower_id, b.geom
  FROM broadcasting_towers b
  WHERE ST_DWithin(b.geom, 'SRID=3857;POINT(3072163.4 7159374.1)', 4000)
	  AND ST_DWithin(b.geom, 'SRID=3857;POINT(3072163.4 7159374.1)', b.sending_range);

			  </programlisting>
	  </refsection>

	  <refsection>
		<title>See Also</title>

		<para><xref linkend="ST_Distance"/>, <xref linkend="ST_Expand"/>, <xref linkend="ST_3DDWithin"/></para>
	  </refsection>
	</refentry>


    </sect2>

</sect1>
