From 8e8efae5049c009194250e3e3acf6c3a27e04f67 Mon Sep 17 00:00:00 2001
From: Paul Ramsey <pramsey@cleverelephant.ca>
Date: Mon, 30 Nov 2015 17:54:09 +0000
Subject: [PATCH] Document ST_Simplify parameter (#2093)

git-svn-id: http://svn.osgeo.org/postgis/trunk@14459 b70326c6-7e19-0410-871a-916f4a2858ee
---
 doc/reference_processing.xml | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/doc/reference_processing.xml b/doc/reference_processing.xml
index 17530d0e0..1d55e736b 100644
--- a/doc/reference_processing.xml
+++ b/doc/reference_processing.xml
@@ -2689,6 +2689,7 @@ LINESTRING(241.42 38.38,241.8 38.45)
 			<funcdef>geometry <function>ST_Simplify</function></funcdef>
 			<paramdef><type>geometry</type> <parameter>geomA</parameter></paramdef>
 			<paramdef><type>float</type> <parameter>tolerance</parameter></paramdef>
+			<paramdef><type>boolean</type> <parameter>preserveCollapsed</parameter></paramdef>
 		  </funcprototype>
 		</funcsynopsis>
 	  </refsynopsisdiv>
@@ -2701,6 +2702,12 @@ LINESTRING(241.42 38.38,241.8 38.45)
 				any kind of geometry. Since simplification occurs on a
 				object-by-object basis you can also feed a GeometryCollection to
 				this function.</para>
+        
+    <para>The "preserve collapsed" flag will retain objects that would otherwise
+      be too small given the tolerance. For example, a 1m long line simplified with a 10m 
+      tolerance. If the preserve flag is given, the line will not disappear. This flag
+      is useful for rendering engines, to avoid having large numbers of very
+      small objects disappear from a map leaving surprising gaps.</para>
 
 		<note><para>Note that returned geometry might lose its
 				simplicity (see <xref linkend="ST_IsSimple" />)</para></note>
-- 
2.40.0