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update ST_Line_Locate ... with example of closest point. Asked way too many times on postgis news groups

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git-svn-id: http://svn.osgeo.org/postgis/trunk@4341 b70326c6-7e19-0410-871a-916f4a2858ee
This commit is contained in:
Regina Obe 2009-08-01 18:33:18 +00:00
parent adf4763a73
commit 0ed90a2fcc
1 changed files with 30 additions and 14 deletions
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20
doc/reference.xml
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@ -13246,7 +13246,7 @@ MULTILINESTRING((3 4,4 5),(1 2,3 4))
</refentry>
</sect1>
<sect1 id="Linear_Referencing">
<sect1 id="Linear_Referencing">
<title>Linear Referencing</title>
<refentry id="ST_Line_Interpolate_Point">
<refnamediv>
@ -13311,6 +13311,14 @@ SELECT ST_AsEWKT(ST_Line_Interpolate_Point(the_line, 0.5))
--------------------
POINT(3.5 4.5 5.5)
--find closest point on a line to a point or other geometry
SELECT ST_AsText(ST_Line_Interpolate_Point(foo.the_line, ST_Line_Locate_Point(foo.the_line, ST_GeomFromText('POINT(4 3)'))))
FROM (SELECT ST_GeomFromText('LINESTRING(1 2, 4 5, 6 7)') As the_line) As foo;
st_astext
----------------
POINT(3 4)
</programlisting>
</refsection>
@ -13318,7 +13326,7 @@ SELECT ST_AsEWKT(ST_Line_Interpolate_Point(the_line, 0.5))
<refsection>
<title>See Also</title>
<para><xref linkend="ST_Length" />, <xref linkend="ST_Line_Locate_Point" /></para>
<para><xref linkend="ST_AsText" />,<xref linkend="ST_AsEWKT" />,<xref linkend="ST_Length" />, <xref linkend="ST_Line_Locate_Point" /></para>
</refsection>
</refentry>
@ -13384,6 +13392,14 @@ WHERE ST_DWithin(street_line, house_loc, 0.2);
POINT(1.01 2.06) | 10
POINT(2.02 3.09) | 15
POINT(3.03 4.12) | 20
--find closest point on a line to a point or other geometry
SELECT ST_AsText(ST_Line_Interpolate_Point(foo.the_line, ST_Line_Locate_Point(foo.the_line, ST_GeomFromText('POINT(4 3)'))))
FROM (SELECT ST_GeomFromText('LINESTRING(1 2, 4 5, 6 7)') As the_line) As foo;
st_astext
----------------
POINT(3 4)
</programlisting>
</refsection>