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new protos for st_value (the point geometry versions -- yeh) plus examples

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git-svn-id: http://svn.osgeo.org/postgis/trunk@5728 b70326c6-7e19-0410-871a-916f4a2858ee
This commit is contained in:
Regina Obe 2010-07-07 14:18:19 +00:00
parent 547c58af8f
commit 6aeb2e04bd
1 changed files with 38 additions and 9 deletions
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47
doc/reference_wktraster.xml
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@ -1293,16 +1293,33 @@ WHERE rid = 2;
<sect1 id="Raster_Pixel_Accessors">
<title>Raster Pixel Accessors</title>
<refentry id="RT_ST_Value">
<refentry id="RT_ST_Value">
<refnamediv>
<refname>ST_Value</refname>
<refpurpose>Returns the value of a given band in a given columnx, rowy pixel. Band numbers start at 1.</refpurpose>
<refpurpose>Returns the value of a given band in a given columnx, rowy pixel or at a particular geometric point. Band numbers start at 1 and assumed to be 1 if not specified.</refpurpose>
</refnamediv>
<refsynopsisdiv>
<funcsynopsis>
<funcprototype>
<funcdef>double precision <function>ST_Value</function></funcdef>
<paramdef><type>raster </type> <parameter>rast</parameter></paramdef>
<paramdef><type>geometry </type> <parameter>pt</parameter></paramdef>
</funcprototype>
<funcprototype>
<funcdef>integer <function>ST_Value</function></funcdef>
<funcdef>double precision <function>ST_Value</function></funcdef>
<paramdef><type>raster </type> <parameter>rast</parameter></paramdef>
<paramdef><type>integer </type> <parameter>bandnum</parameter></paramdef>
<paramdef><type>geometry </type> <parameter>pt</parameter></paramdef>
</funcprototype>
<funcprototype>
<funcdef>double precision <function>ST_Value</function></funcdef>
<paramdef><type>raster </type> <parameter>rast</parameter></paramdef>
<paramdef><type>integer </type> <parameter>columnx</parameter></paramdef>
<paramdef><type>integer </type> <parameter>rowy</parameter></paramdef>
</funcprototype>
<funcprototype>
<funcdef>double precision <function>ST_Value</function></funcdef>
<paramdef><type>raster </type> <parameter>rast</parameter></paramdef>
<paramdef><type>integer </type> <parameter>bandnum</parameter></paramdef>
<paramdef><type>integer </type> <parameter>columnx</parameter></paramdef>
@ -1326,18 +1343,30 @@ WHERE rid = 2;
<para>Also note that many of these examples particular the intersection example can be more
simply done with the planned functions that are not currently available.</para>
<para>If you are looking for a function that will take a geometry point and return a pixel value, this is in the works, for now
you can use a user contributed function <ulink url="http://trac.osgeo.org/postgis/wiki/UsersWikiwktrasterfunctions">upgis_ptval</ulink>
</para>
</note>
</refsection>
<refsection>
<title>Examples</title>
<programlisting>
SELECt rid, ST_Value(rast, 1,1,1) As b1pval,
-- get raster values at particular postgis geometry points
-- the srid of your geometry should be same as for your raster
SELECT rid, ST_Value(rast, foo.pt_geom) As b1pval, ST_Value(rast, 2, foo.pt_geom) As b2pval
FROM dummy_rast CROSS JOIN (SELECT ST_SetSRID(ST_Point(3427927.77,5793243.76),-1) As pt_geom) As foo
WHERE rid=2;
rid | b1pval | b2pval
-----+--------+--------
2 | 252 | 79
-- general fictious example using a real table
SELECT rid, ST_Value(rast, 3, sometable.geom) As b3pval
FROM sometable
WHERE ST_Intersects(rast,sometable.geom);
</programlisting>
<programlisting>
SELECT rid, ST_Value(rast, 1,1,1) As b1pval,
ST_Value(rast, 2,1,1) As b2pval, ST_Value(rast, 3,1,1) As b3pval
FROM dummy_rast
WHERE rid=2;