mirror of
https://git.osgeo.org/gitea/postgis/postgis
synced 2024-10-24 09:02:37 +00:00
ef67651d86
- ST_Line_Interpolate_Point renamed to ST_LineInterpolatePoint - ST_Line_Substring renamed to ST_LineSubstring - ST_Line_Locate_Point renamed to ST_LineLocatePoint Tests updated to use the new signature, docs updated to show the new signature and report deprecations git-svn-id: http://svn.osgeo.org/postgis/trunk@11190 b70326c6-7e19-0410-871a-916f4a2858ee
603 lines
20 KiB
XML
603 lines
20 KiB
XML
<?xml version="1.0" encoding="UTF-8"?>
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<sect1 id="Linear_Referencing">
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<title>Linear Referencing</title>
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<refentry id="ST_Line_Interpolate_Point">
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<refnamediv>
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<refname>ST_LineInterpolatePoint</refname>
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<refpurpose>Returns a point interpolated along a line. Second argument is a float8 between 0 and 1
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representing fraction of total length of linestring the point has to be located.</refpurpose>
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</refnamediv>
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<refsynopsisdiv>
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<funcsynopsis>
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<funcprototype>
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<funcdef>geometry <function>ST_LineInterpolatePoint</function></funcdef>
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<paramdef><type>geometry </type> <parameter>a_linestring</parameter></paramdef>
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<paramdef><type>float </type> <parameter>a_fraction</parameter></paramdef>
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</funcprototype>
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</funcsynopsis>
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</refsynopsisdiv>
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<refsection>
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<title>Description</title>
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<para>Returns a point interpolated along a line. First argument
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must be a LINESTRING. Second argument is a float8 between 0 and 1
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representing fraction of total linestring length the point has to be located.</para>
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<para>See <xref linkend="ST_Line_Locate_Point" /> for
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computing the line location nearest to a Point.</para>
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<note>
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<para>Since release 1.1.1 this function also interpolates M and
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Z values (when present), while prior releases set them to
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0.0.</para>
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</note>
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<para>Availability: 0.8.2, Z and M supported added in 1.1.1</para>
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<para>Changed: 2.1.0. Up to 2.0.x this was called ST_LineInterpolatePoint.</para>
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<para>&Z_support;</para>
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</refsection>
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<refsection>
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<title>Examples</title>
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<informalfigure>
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<mediaobject>
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<imageobject>
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<imagedata fileref="images/st_line_interpolate_point01.png" />
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</imageobject>
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<caption><para>A linestring with the interpolated point at 20% position (0.20) </para></caption>
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</mediaobject>
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</informalfigure>
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<programlisting>--Return point 20% along 2d line
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SELECT ST_AsEWKT(ST_Line_Interpolate_Point(the_line, 0.20))
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FROM (SELECT ST_GeomFromEWKT('LINESTRING(25 50, 100 125, 150 190)') as the_line) As foo;
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st_asewkt
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----------------
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POINT(51.5974135047432 76.5974135047432)
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</programlisting>
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<programlisting>
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--Return point mid-way of 3d line
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SELECT ST_AsEWKT(ST_Line_Interpolate_Point(the_line, 0.5))
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FROM (SELECT ST_GeomFromEWKT('LINESTRING(1 2 3, 4 5 6, 6 7 8)') as the_line) As foo;
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st_asewkt
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--------------------
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POINT(3.5 4.5 5.5)
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--find closest point on a line to a point or other geometry
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SELECT ST_AsText(ST_Line_Interpolate_Point(foo.the_line, ST_Line_Locate_Point(foo.the_line, ST_GeomFromText('POINT(4 3)'))))
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FROM (SELECT ST_GeomFromText('LINESTRING(1 2, 4 5, 6 7)') As the_line) As foo;
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st_astext
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----------------
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POINT(3 4)
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</programlisting>
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</refsection>
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<!-- Optionally add a "See Also" section -->
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<refsection>
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<title>See Also</title>
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<para><xref linkend="ST_AsText" />, <xref linkend="ST_AsEWKT" />, <xref linkend="ST_Length" />, <xref linkend="ST_Line_Locate_Point" /></para>
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</refsection>
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</refentry>
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<refentry id="ST_Line_Locate_Point">
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<refnamediv>
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<refname>ST_LineLocatePoint</refname>
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<refpurpose>Returns a float between 0 and 1 representing the location of
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the closest point on LineString to the given Point, as a fraction
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of total 2d line length.</refpurpose>
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</refnamediv>
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<refsynopsisdiv>
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<funcsynopsis>
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<funcprototype>
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<funcdef>float <function>ST_LineLocatePoint</function></funcdef>
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<paramdef><type>geometry </type> <parameter>a_linestring</parameter></paramdef>
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<paramdef><type>geometry </type> <parameter>a_point</parameter></paramdef>
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</funcprototype>
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</funcsynopsis>
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</refsynopsisdiv>
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<refsection>
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<title>Description</title>
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<para>Returns a float between 0 and 1 representing the location of
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the closest point on LineString to the given Point, as a fraction
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of total <link linkend="ST_Length2D">2d line</link> length.</para>
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<para>You can use the returned location to extract a Point (<xref linkend="ST_Line_Interpolate_Point" />) or
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a substring (<xref linkend="ST_Line_Substring" />).</para>
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<para>This is useful for approximating numbers of addresses</para>
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<para>Availability: 1.1.0</para>
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<para>Changed: 2.1.0. Up to 2.0.x this was called ST_Line_Locate_Point.</para>
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</refsection>
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<refsection>
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<title>Examples</title>
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<programlisting>
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--Rough approximation of finding the street number of a point along the street
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--Note the whole foo thing is just to generate dummy data that looks
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--like house centroids and street
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--We use ST_DWithin to exclude
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--houses too far away from the street to be considered on the street
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SELECT ST_AsText(house_loc) As as_text_house_loc,
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startstreet_num +
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CAST( (endstreet_num - startstreet_num)
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* ST_LineLocatePoint(street_line, house_loc) As integer) As street_num
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FROM
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(SELECT ST_GeomFromText('LINESTRING(1 2, 3 4)') As street_line,
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ST_MakePoint(x*1.01,y*1.03) As house_loc, 10 As startstreet_num,
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20 As endstreet_num
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FROM generate_series(1,3) x CROSS JOIN generate_series(2,4) As y)
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As foo
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WHERE ST_DWithin(street_line, house_loc, 0.2);
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as_text_house_loc | street_num
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-------------------+------------
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POINT(1.01 2.06) | 10
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POINT(2.02 3.09) | 15
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POINT(3.03 4.12) | 20
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--find closest point on a line to a point or other geometry
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SELECT ST_AsText(ST_Line_Interpolate_Point(foo.the_line, ST_LineLocatePoint(foo.the_line, ST_GeomFromText('POINT(4 3)'))))
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FROM (SELECT ST_GeomFromText('LINESTRING(1 2, 4 5, 6 7)') As the_line) As foo;
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st_astext
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----------------
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POINT(3 4)
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</programlisting>
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</refsection>
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<!-- Optionally add a "See Also" section -->
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<refsection>
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<title>See Also</title>
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<para><xref linkend="ST_DWithin" />, <xref linkend="ST_Length2D" />, <xref linkend="ST_Line_Interpolate_Point" />, <xref linkend="ST_Line_Substring" /></para>
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</refsection>
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</refentry>
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<refentry id="ST_Line_Substring">
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<refnamediv>
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<refname>ST_LineSubstring</refname>
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<refpurpose>Return a linestring being a substring of the input one
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starting and ending at the given fractions of total 2d length.
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Second and third arguments are float8 values between 0 and
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1.</refpurpose>
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</refnamediv>
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<refsynopsisdiv>
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<funcsynopsis>
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<funcprototype>
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<funcdef>geometry <function>ST_LineSubstring</function></funcdef>
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<paramdef><type>geometry </type> <parameter>a_linestring</parameter></paramdef>
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<paramdef><type>float </type> <parameter>startfraction</parameter></paramdef>
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<paramdef><type>float </type> <parameter>endfraction</parameter></paramdef>
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</funcprototype>
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</funcsynopsis>
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</refsynopsisdiv>
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<refsection>
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<title>Description</title>
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<para>Return a linestring being a substring of the input one
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starting and ending at the given fractions of total 2d length.
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Second and third arguments are float8 values between 0 and
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1. This only works with LINESTRINGs.
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To use with contiguous MULTILINESTRINGs use in conjunction with <xref linkend="ST_LineMerge" />.</para>
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<para>If 'start' and 'end' have the same value this is equivalent
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to <xref linkend="ST_Line_Interpolate_Point" />.</para>
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<para>See <xref linkend="ST_Line_Locate_Point" /> for
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computing the line location nearest to a Point.</para>
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<note>
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<para>Since release 1.1.1 this function also interpolates M and
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Z values (when present), while prior releases set them to
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unspecified values.</para>
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</note>
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<para>Availability: 1.1.0, Z and M supported added in 1.1.1</para>
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<para>Changed: 2.1.0. Up to 2.0.x this was called ST_LineSubstring.</para>
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<para>&Z_support;</para>
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</refsection>
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<refsection>
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<title>Examples</title>
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<informalfigure>
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<mediaobject>
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<imageobject>
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<imagedata fileref="images/st_line_substring01.png" />
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</imageobject>
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<caption><para>A linestring seen with 1/3 midrange overlaid (0.333, 0.666) </para></caption>
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</mediaobject>
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</informalfigure>
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<programlisting>
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--Return the approximate 1/3 mid-range part of a linestring
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SELECT ST_AsText(ST_Line_SubString(ST_GeomFromText('LINESTRING(25 50, 100 125, 150 190)'), 0.333, 0.666));
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st_astext
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------------------------------------------------------------------------------------------------
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LINESTRING(69.2846934853974 94.2846934853974,100 125,111.700356260683 140.210463138888)
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--The below example simulates a while loop in
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--SQL using PostgreSQL generate_series() to cut all
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--linestrings in a table to 100 unit segments
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-- of which no segment is longer than 100 units
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-- units are measured in the SRID units of measurement
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-- It also assumes all geometries are LINESTRING or contiguous MULTILINESTRING
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--and no geometry is longer than 100 units*10000
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--for better performance you can reduce the 10000
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--to match max number of segments you expect
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SELECT field1, field2, ST_LineSubstring(the_geom, 100.00*n/length,
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CASE
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WHEN 100.00*(n+1) < length THEN 100.00*(n+1)/length
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ELSE 1
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END) As the_geom
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FROM
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(SELECT sometable.field1, sometable.field2,
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ST_LineMerge(sometable.the_geom) AS the_geom,
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ST_Length(sometable.the_geom) As length
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FROM sometable
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) AS t
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CROSS JOIN generate_series(0,10000) AS n
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WHERE n*100.00/length < 1;
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</programlisting>
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</refsection>
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<!-- Optionally add a "See Also" section -->
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<refsection>
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<title>See Also</title>
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<para><xref linkend="ST_Length" />, <xref linkend="ST_Line_Interpolate_Point" />, <xref linkend="ST_LineMerge" /></para>
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</refsection>
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</refentry>
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<refentry id="ST_LocateAlong">
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<refnamediv>
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<refname>ST_LocateAlong</refname>
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<refpurpose>Return a derived geometry collection value with elements
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that match the specified measure. Polygonal elements are not
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supported.</refpurpose>
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</refnamediv>
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<refsynopsisdiv>
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<funcsynopsis>
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<funcprototype>
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<funcdef>geometry <function>ST_LocateAlong</function></funcdef>
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<paramdef><type>geometry </type> <parameter>ageom_with_measure</parameter></paramdef>
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<paramdef><type>float </type> <parameter>a_measure</parameter></paramdef>
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<paramdef choice="opt"><type>float </type> <parameter>offset</parameter></paramdef>
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</funcprototype>
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</funcsynopsis>
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</refsynopsisdiv>
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<refsection>
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<title>Description</title>
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<para>Return a derived geometry collection value with elements
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that match the specified measure. Polygonal elements are not
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supported.</para>
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<para>If an offset is provided, the resultant will be offset to the
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left or right of the input line by the specified number of units.
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A positive offset will be to the left, and a negative one to the
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right.</para>
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<para>Semantic is specified by: ISO/IEC CD 13249-3:200x(E) - Text
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for Continuation CD Editing Meeting</para>
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<para>Availability: 1.1.0 by old name ST_Locate_Along_Measure. </para>
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<para>Changed: 2.0.0 in prior versions this used to be called ST_Locate_Along_Measure. The old name has been deprecated and will be removed in the future but is still available.</para>
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<note><para>Use this function only for geometries with an M component</para></note>
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<para>&M_support;</para>
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</refsection>
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<refsection>
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<title>Examples</title>
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<programlisting>SELECT ST_AsText(the_geom)
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FROM
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(SELECT ST_LocateAlong(
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ST_GeomFromText('MULTILINESTRINGM((1 2 3, 3 4 2, 9 4 3),
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(1 2 3, 5 4 5))'),3) As the_geom) As foo;
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st_asewkt
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-----------------------------------------------------------
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MULTIPOINT M (1 2 3)
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--Geometry collections are difficult animals so dump them
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--to make them more digestable
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SELECT ST_AsText((ST_Dump(the_geom)).geom)
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FROM
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(SELECT ST_LocateAlong(
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ST_GeomFromText('MULTILINESTRINGM((1 2 3, 3 4 2, 9 4 3),
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(1 2 3, 5 4 5))'),3) As the_geom) As foo;
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st_asewkt
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---------------
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POINTM(1 2 3)
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POINTM(9 4 3)
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POINTM(1 2 3)
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</programlisting>
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</refsection>
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<!-- Optionally add a "See Also" section -->
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<refsection>
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<title>See Also</title>
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<para><xref linkend="ST_Dump" />, <xref linkend="ST_LocateBetween" /></para>
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</refsection>
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</refentry>
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<refentry id="ST_LocateBetween">
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<refnamediv>
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<refname>ST_LocateBetween</refname>
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<refpurpose>Return a derived geometry collection value with elements
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that match the specified range of measures inclusively. Polygonal
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elements are not supported.</refpurpose>
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</refnamediv>
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<refsynopsisdiv>
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<funcsynopsis>
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<funcprototype>
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<funcdef>geometry <function>ST_LocateBetween</function></funcdef>
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<paramdef><type>geometry </type> <parameter>geomA</parameter></paramdef>
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<paramdef><type>float </type> <parameter>measure_start</parameter></paramdef>
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<paramdef><type>float </type> <parameter>measure_end</parameter></paramdef>
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<paramdef choice="opt"><type>float </type> <parameter>offset</parameter></paramdef>
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</funcprototype>
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</funcsynopsis>
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</refsynopsisdiv>
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<refsection>
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<title>Description</title>
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<para>Return a derived geometry collection value with elements
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that match the specified range of measures inclusively. Polygonal
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elements are not supported.</para>
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<para>Semantic is specified by: ISO/IEC CD 13249-3:200x(E) - Text
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for Continuation CD Editing Meeting</para>
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<para>Availability: 1.1.0 by old name ST_Locate_Between_Measures. </para>
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<para>Changed: 2.0.0 - in prior versions this used to be called ST_Locate_Between_Measures. The old name has been deprecated and will be removed in the future but is still available for backward compatibility.</para>
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<para>&M_support;</para>
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</refsection>
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<refsection>
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<title>Examples</title>
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<programlisting>SELECT ST_AsText(the_geom)
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FROM
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(SELECT ST_LocateBetween(
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ST_GeomFromText('MULTILINESTRING M ((1 2 3, 3 4 2, 9 4 3),
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(1 2 3, 5 4 5))'),1.5, 3) As the_geom) As foo;
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st_asewkt
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------------------------------------------------------------------------
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GEOMETRYCOLLECTION M (LINESTRING M (1 2 3,3 4 2,9 4 3),POINT M (1 2 3))
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--Geometry collections are difficult animals so dump them
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--to make them more digestable
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SELECT ST_AsText((ST_Dump(the_geom)).geom)
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FROM
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(SELECT ST_LocateBetween(
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ST_GeomFromText('MULTILINESTRING M ((1 2 3, 3 4 2, 9 4 3),
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(1 2 3, 5 4 5))'),1.5, 3) As the_geom) As foo;
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st_asewkt
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--------------------------------
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LINESTRING M (1 2 3,3 4 2,9 4 3)
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POINT M (1 2 3)</programlisting>
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</refsection>
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<!-- Optionally add a "See Also" section -->
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<refsection>
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<title>See Also</title>
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<para><xref linkend="ST_Dump" />, <xref linkend="ST_LocateAlong" /></para>
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</refsection>
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</refentry>
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<refentry id="ST_LocateBetweenElevations">
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<refnamediv>
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<refname>ST_LocateBetweenElevations</refname>
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<refpurpose>Return a derived geometry (collection) value with elements
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that intersect the specified range of elevations inclusively. Only 3D, 4D LINESTRINGS and MULTILINESTRINGS
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are supported.</refpurpose>
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</refnamediv>
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<refsynopsisdiv>
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<funcsynopsis>
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<funcprototype>
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<funcdef>geometry <function>ST_LocateBetweenElevations</function></funcdef>
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<paramdef><type>geometry </type> <parameter>geom_mline</parameter></paramdef>
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<paramdef><type>float </type> <parameter>elevation_start</parameter></paramdef>
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<paramdef><type>float </type> <parameter>elevation_end</parameter></paramdef>
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</funcprototype>
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</funcsynopsis>
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</refsynopsisdiv>
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<refsection>
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<title>Description</title>
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<para>Return a derived geometry (collection) value with elements
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that intersect the specified range of elevations inclusively. Only 3D, 3DM LINESTRINGS and MULTILINESTRINGS
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are supported.</para>
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<para>Availability: 1.4.0</para>
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<para>&Z_support;</para>
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</refsection>
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<refsection>
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<title>Examples</title>
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<programlisting>SELECT ST_AsEWKT(ST_LocateBetweenElevations(
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ST_GeomFromEWKT('LINESTRING(1 2 3, 4 5 6)'),2,4)) As ewelev;
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ewelev
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----------------------------------------------------------------
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MULTILINESTRING((1 2 3,2 3 4))
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|
|
|
SELECT ST_AsEWKT(ST_LocateBetweenElevations(
|
|
ST_GeomFromEWKT('LINESTRING(1 2 6, 4 5 -1, 7 8 9)'),6,9)) As ewelev;
|
|
|
|
ewelev
|
|
----------------------------------------------------------------
|
|
GEOMETRYCOLLECTION(POINT(1 2 6),LINESTRING(6.1 7.1 6,7 8 9))
|
|
|
|
--Geometry collections are difficult animals so dump them
|
|
--to make them more digestable
|
|
SELECT ST_AsEWKT((ST_Dump(the_geom)).geom)
|
|
FROM
|
|
(SELECT ST_LocateBetweenElevations(
|
|
ST_GeomFromEWKT('LINESTRING(1 2 6, 4 5 -1, 7 8 9)'),6,9) As the_geom) As foo;
|
|
|
|
st_asewkt
|
|
--------------------------------
|
|
POINT(1 2 6)
|
|
LINESTRING(6.1 7.1 6,7 8 9)
|
|
</programlisting>
|
|
</refsection>
|
|
|
|
<!-- Optionally add a "See Also" section -->
|
|
<refsection>
|
|
<title>See Also</title>
|
|
|
|
<para><xref linkend="ST_Dump" /></para>
|
|
</refsection>
|
|
</refentry>
|
|
|
|
|
|
<refentry id="ST_InterpolatePoint">
|
|
<refnamediv>
|
|
<refname>ST_InterpolatePoint</refname>
|
|
|
|
<refpurpose>Return the value of the measure dimension of a geometry at the point closed to the provided point.</refpurpose>
|
|
</refnamediv>
|
|
|
|
<refsynopsisdiv>
|
|
<funcsynopsis>
|
|
<funcprototype>
|
|
<funcdef>float <function>ST_InterpolatePoint</function></funcdef>
|
|
<paramdef><type>geometry </type> <parameter>line</parameter></paramdef>
|
|
<paramdef><type>geometry </type> <parameter>point</parameter></paramdef>
|
|
</funcprototype>
|
|
|
|
</funcsynopsis>
|
|
</refsynopsisdiv>
|
|
|
|
<refsection>
|
|
<title>Description</title>
|
|
|
|
<para>Return the value of the measure dimension of a geometry at the point closed to the provided point.</para>
|
|
|
|
<para>Availability: 2.0.0</para>
|
|
|
|
<para>&Z_support;</para>
|
|
</refsection>
|
|
|
|
<refsection>
|
|
<title>Examples</title>
|
|
|
|
<programlisting>SELECT ST_InterpolatePoint('LINESTRING M (0 0 0, 10 0 20)', 'POINT(5 5)');
|
|
st_interpolatepoint
|
|
---------------------
|
|
10
|
|
</programlisting>
|
|
</refsection>
|
|
|
|
<refsection>
|
|
<title>See Also</title>
|
|
|
|
<para><xref linkend="ST_AddMeasure" />, <xref linkend="ST_LocateAlong" />, <xref linkend="ST_LocateBetween" /></para>
|
|
</refsection>
|
|
|
|
</refentry>
|
|
|
|
|
|
<refentry id="ST_AddMeasure">
|
|
<refnamediv>
|
|
<refname>ST_AddMeasure</refname>
|
|
|
|
<refpurpose>Return a derived geometry with measure elements linearly interpolated between the start and end points. If the geometry has no measure dimension, one is added. If the geometry has a measure dimension, it is over-written with new values. Only LINESTRINGS and MULTILINESTRINGS are supported.</refpurpose>
|
|
</refnamediv>
|
|
|
|
<refsynopsisdiv>
|
|
<funcsynopsis>
|
|
<funcprototype>
|
|
<funcdef>geometry <function>ST_AddMeasure</function></funcdef>
|
|
<paramdef><type>geometry </type> <parameter>geom_mline</parameter></paramdef>
|
|
<paramdef><type>float </type> <parameter>measure_start</parameter></paramdef>
|
|
<paramdef><type>float </type> <parameter>measure_end</parameter></paramdef>
|
|
</funcprototype>
|
|
|
|
</funcsynopsis>
|
|
</refsynopsisdiv>
|
|
|
|
<refsection>
|
|
<title>Description</title>
|
|
|
|
<para>Return a derived geometry with measure elements linearly interpolated between the start and end points. If the geometry has no measure dimension, one is added. If the geometry has a measure dimension, it is over-written with new values. Only LINESTRINGS and MULTILINESTRINGS are supported.</para>
|
|
|
|
<para>Availability: 1.5.0</para>
|
|
|
|
<para>&Z_support;</para>
|
|
</refsection>
|
|
|
|
<refsection>
|
|
<title>Examples</title>
|
|
|
|
<programlisting>SELECT ST_AsText(ST_AddMeasure(
|
|
ST_GeomFromEWKT('LINESTRING(1 0, 2 0, 4 0)'),1,4)) As ewelev;
|
|
ewelev
|
|
--------------------------------
|
|
LINESTRINGM(1 0 1,2 0 2,4 0 4)
|
|
|
|
SELECT ST_AsText(ST_AddMeasure(
|
|
ST_GeomFromEWKT('LINESTRING(1 0 4, 2 0 4, 4 0 4)'),10,40)) As ewelev;
|
|
ewelev
|
|
----------------------------------------
|
|
LINESTRING(1 0 4 10,2 0 4 20,4 0 4 40)
|
|
|
|
SELECT ST_AsText(ST_AddMeasure(
|
|
ST_GeomFromEWKT('LINESTRINGM(1 0 4, 2 0 4, 4 0 4)'),10,40)) As ewelev;
|
|
ewelev
|
|
----------------------------------------
|
|
LINESTRINGM(1 0 10,2 0 20,4 0 40)
|
|
|
|
SELECT ST_AsText(ST_AddMeasure(
|
|
ST_GeomFromEWKT('MULTILINESTRINGM((1 0 4, 2 0 4, 4 0 4),(1 0 4, 2 0 4, 4 0 4))'),10,70)) As ewelev;
|
|
ewelev
|
|
-----------------------------------------------------------------
|
|
MULTILINESTRINGM((1 0 10,2 0 20,4 0 40),(1 0 40,2 0 50,4 0 70))
|
|
</programlisting>
|
|
</refsection>
|
|
|
|
</refentry>
|
|
|
|
|
|
</sect1>
|