From: Regina Obe <lr@pcorp.us>
Date: Wed, 4 Nov 2009 11:57:06 +0000 (+0000)
Subject: type correction in ST_BuildArea output.  Add additional proto to ST_Area and correct... 
X-Git-Tag: 1.5.0b1~298
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=35c2df329383e6f39cd8d237bffffa3ba3cc68c3;p=postgis

type correction in ST_BuildArea output.  Add additional proto to ST_Area and correct the example to show the new spheroid measurement default

git-svn-id: http://svn.osgeo.org/postgis/trunk@4735 b70326c6-7e19-0410-871a-916f4a2858ee
---

diff --git a/doc/reference.xml b/doc/reference.xml
index 5b6ef5e7f..b368575ed 100644
--- a/doc/reference.xml
+++ b/doc/reference.xml
@@ -8980,6 +8980,12 @@ FROM
 			  <funcdef>float <function>ST_Area</function></funcdef>
 				<paramdef><type>geography </type><parameter>g1</parameter></paramdef>
 			</funcprototype>
+			
+			<funcprototype>
+			  <funcdef>float <function>ST_Area</function></funcdef>
+				<paramdef><type>geography </type><parameter>g1</parameter></paramdef>
+				<paramdef><type>boolean </type><parameter>use_spheroid</parameter></paramdef>
+			</funcprototype>
 		  </funcsynopsis>
 		</refsynopsisdiv>
 		<refsection>
@@ -8987,7 +8993,9 @@ FROM
 
 			<para>Returns the area of the geometry if it is a polygon or
 				multi-polygon. Return the area measurement of an ST_Surface or
-		  ST_MultiSurface value. For geometry Area is in the units of the spatial reference system.  For geography area is in square meters.</para>
+		  ST_MultiSurface value. For geometry Area is in the units of the srid.  For geography area is in square meters  and defaults to measuring about the spheroid of the geography (currently only WGS84).
+		  To measure around the faster but less accurate sphere -- ST_Area(geog,false).
+		  </para>
 
 			<para><inlinemediaobject>
 				<imageobject>
@@ -9034,10 +9042,11 @@ SELECT ST_Area(the_geom) As sqft, ST_Area(ST_Transform(the_geom,26986)) As sqm
 			</programlisting>
 
 <para>Return area square feet and square meters using Geography data type.  Note that we transform to our geometry to geography
-	(before you can do that make sure your geometry is in WGS 84 long lat 4326).  Geography always measures in meters. </para>
+	(before you can do that make sure your geometry is in WGS 84 long lat 4326).  Geography always measures in meters. 
+	This is just for demonstration to compare.  Normally your table will be stored in geography data type already.</para>
 <programlisting>
 
-SELECT ST_Area(the_geog)/POWER(0.3048,2) As sqft, ST_Area(the_geog) As sqm
+SELECT ST_Area(the_geog)/POWER(0.3048,2) As sqft_spheroid,  ST_Area(the_geog,false)/POWER(0.3048,2) As sqft_sphere, ST_Area(the_geog) As sqm_spheroid
 		FROM (SELECT
 		geography(
 		ST_Transform(
@@ -9047,9 +9056,9 @@ SELECT ST_Area(the_geog)/POWER(0.3048,2) As sqft, ST_Area(the_geog) As sqm
 			)
 		)
 	) As foo(the_geog);
-	   sqft       |       sqm
-------------------+------------------
- 927.186481558707 | 86.1384427837078
+ sqft_spheroid   |   sqft_sphere    |   sqm_spheroid
+-----------------+------------------+------------------
+928.684405217197 | 927.186481558724 | 86.2776044452694
 
  --if your data is in geography already
  SELECT ST_Area(the_geog)/POWER(0.3048,2) As  sqft, ST_Area(the_geog) As sqm
@@ -12345,7 +12354,7 @@ MULTIPOLYGON(((-1 2,3 4,5 6,-1 2)),((-1 2,2 3,5 6,-1 2))) | POLYGON((-1 2,5 6,3
 		  <refsynopsisdiv>
 			<funcsynopsis>
 			  <funcprototype>
-				<funcdef>boolean <function>ST_BuildArea</function></funcdef>
+				<funcdef>geometry <function>ST_BuildArea</function></funcdef>
 				<paramdef><type>geometry </type> <parameter>A</parameter></paramdef>
 			  </funcprototype>
 			</funcsynopsis>