Document the expand() function (finally!)

git-svn-id: http://svn.osgeo.org/postgis/trunk@568 b70326c6-7e19-0410-871a-916f4a2858ee

diff --git a/doc/postgis.xml b/doc/postgis.xml
index 109c32aa32c3486fce3977ee6e82d8b008cd05bc..3e3390d9aa5a300f4f96a4897805612fec1e9177 100644 (file)
--- a/doc/postgis.xml
+++ b/doc/postgis.xml
@@ -2491,6 +2491,16 @@ is simple (does not pass through the same point more than once).
                                                </para> 
                                        </listitem> 
                                </varlistentry> 
+                               <varlistentry> 
+                                       <term>expand(geometry, float)</term> 
+                                       <listitem> 
+                                               <para>This function returns a bounding box expanded in all directions
+                                               from the bounding box of the input geometry, by an amount specified
+                                               in the second argument.  Very useful for distance() queries, to add
+                                               an index filter to the query.
+                                               </para> 
+                                       </listitem> 
+                               </varlistentry> 
                                <varlistentry> 
                                        <term>collect(geometry set)</term> 
                                        <listitem>