[postgis-commits] svn - r2863 - trunk/doc
postgis-commits at postgis.refractions.net
postgis-commits at postgis.refractions.net
Tue Jul 15 23:42:00 PDT 2008
Author: kneufeld
Date: 2008-07-15 23:42:00 -0700 (Tue, 15 Jul 2008)
New Revision: 2863
Modified:
trunk/doc/reference.xml
trunk/doc/reference_new.xml
Log:
moved ST_Envelope, complete with examples.
Modified: trunk/doc/reference.xml
===================================================================
--- trunk/doc/reference.xml 2008-07-16 05:10:32 UTC (rev 2862)
+++ trunk/doc/reference.xml 2008-07-16 06:42:00 UTC (rev 2863)
@@ -476,24 +476,6 @@
</varlistentry>
<varlistentry>
- <term>ST_Envelope(geometry)</term>
-
- <listitem>
- <para>Returns a vald geometry (POINT, LINESTRING or POLYGON)
- representing the bounding box of the geometry. Degenerate cases
- (vertical lines, point) will return a geometry of lower dimension
- than POLYGON.</para>
-
- <para>OGC SPEC s2.1.1.1 - The minimum bounding box for this
- Geometry, returned as a Geometry. The polygon is defined by the
- corner points of the bounding box ((MINX, MINY), (MAXX, MINY),
- (MAXX, MAXY), (MINX, MAXY), (MINX, MINY)).</para>
-
- <para>NOTE:PostGIS will add a Zmin/Zmax coordinate as well.</para>
- </listitem>
- </varlistentry>
-
- <varlistentry>
<term>ST_IsEmpty(geometry)</term>
<listitem>
@@ -1095,18 +1077,6 @@
<variablelist>
<varlistentry>
- <term>UpdateGeometrySRID([<schema_name>], <table_name>,
- <column_name>, <srid>)</term>
-
- <listitem>
- <para>Update the SRID of all features in a geometry column
- updating constraints and reference in geometry_columns. Note: uses
- current_schema() on schema-aware pgsql installations if schema is
- not provided.</para>
- </listitem>
- </varlistentry>
-
- <varlistentry>
<term>update_geometry_stats([<table_name>,
<column_name>])</term>
@@ -2813,17 +2783,6 @@
</varlistentry>
<varlistentry>
- <term>ST_Envelope</term>
-
- <listitem>
- <para>Return the bounding rectangle for the ST_Geometry
- value.</para>
-
- <para>SQL-MM 3: 5.1.15</para>
- </listitem>
- </varlistentry>
-
- <varlistentry>
<term>ST_Equals</term>
<listitem>
Modified: trunk/doc/reference_new.xml
===================================================================
--- trunk/doc/reference_new.xml 2008-07-16 05:10:32 UTC (rev 2862)
+++ trunk/doc/reference_new.xml 2008-07-16 06:42:00 UTC (rev 2863)
@@ -412,6 +412,100 @@
<sect1>
<title>Geometry Accessors</title>
+
+ <refentry id="ST_Envelope">
+ <refnamediv>
+ <refname>ST_Envelope</refname>
+
+ <refpurpose>Returns a geometry representing the bounding box of the
+ supplied geometry.</refpurpose>
+ </refnamediv>
+
+ <refsynopsisdiv>
+ <funcsynopsis>
+ <funcprototype>
+ <funcdef>boolean <function>ST_Envelope</function></funcdef>
+
+ <paramdef><type>geometry </type> <parameter>g1</parameter></paramdef>
+ </funcprototype>
+ </funcsynopsis>
+ </refsynopsisdiv>
+
+ <refsection>
+ <title>Description</title>
+
+ <para>Returns the minimum bounding box for the supplied geometry, as a geometry.
+ The polygon is defined by the corner points of the bounding box
+ ((<varname>MINX</varname>, <varname>MINY</varname>),
+ (<varname>MINX</varname>, <varname>MAXY</varname>),
+ (<varname>MAXX</varname>, <varname>MAXY</varname>),
+ (<varname>MAXX</varname>, <varname>MINY</varname>),
+ (<varname>MINX</varname>, <varname>MINY</varname>)). (PostGIS will add a
+ <varname>ZMIN</varname>/<varname>ZMAX</varname> coordinate as
+ well).</para>
+
+ <para>Degenerate cases (vertical lines, points) will return a geometry of
+ lower dimension than <varname>POLYGON</varname>, ie.
+ <varname>POINT</varname> or <varname>LINESTRING</varname>.</para>
+
+ <caution>
+ <para>In PostGIS, the bounding box of a geometry is represented internally using
+ <varname>float4</varname>s instead of <varname>float8</varname>s that are used
+ to store geometries. The bounding box coordinates are floored, guarenteeing
+ that the geometry is contained entirely within its bounds. This has the
+ advantage that a geometry's bounding box is half the size as the minimum
+ bounding rectangle, which means significantly faster indexes and general performance.
+ But it also means that the bounding box is NOT the same as the minimum bounding
+ rectangle that bounds the geometry.</para>
+ </caution>
+
+ <para><inlinemediaobject>
+ <imageobject>
+ <imagedata fileref="images/check.png" />
+ </imageobject>
+ </inlinemediaobject> This method implements the <ulink
+ url="http://www.opengeospatial.org/standards/sfs">OpenGIS Simple Features
+ Implementation Specification for SQL: v1.1: s2.1.1.1</ulink></para>
+
+ <para><inlinemediaobject>
+ <imageobject>
+ <imagedata fileref="images/check.png" />
+ </imageobject>
+ </inlinemediaobject> This method implements the SQL/MM specification:
+ SQL-MM 3: 5.1.15</para>
+ </refsection>
+
+ <refsection>
+ <title>Examples</title>
+
+ <programlisting>
+SELECT ST_AsText(ST_Envelope('POINT(1 3)'::geometry));
+ st_astext
+------------
+ POINT(1 3)
+(1 row)
+
+
+SELECT ST_AsText(ST_Envelope('LINESTRING(0 0, 1 3)'::geometry));
+ st_astext
+--------------------------------
+ POLYGON((0 0,0 3,1 3,1 0,0 0))
+(1 row)
+
+
+SELECT ST_AsText(ST_Envelope('POLYGON((0 0, 0 1, 1.0000001 1, 1.0000001 0, 0 0))'::geometry));
+ st_astext
+--------------------------------------------------------------
+ POLYGON((0 0,0 1,1.00000011920929 1,1.00000011920929 0,0 0))
+(1 row)
+SELECT ST_AsText(ST_Envelope('POLYGON((0 0, 0 1, 1.0000000001 1, 1.0000000001 0, 0 0))'::geometry));
+ st_astext
+--------------------------------------------------------------
+ POLYGON((0 0,0 1,1.00000011920929 1,1.00000011920929 0,0 0))
+(1 row)</programlisting>
+ </refsection>
+</refentry>
+
</sect1>
<sect1>
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