mirror of
https://git.osgeo.org/gitea/postgis/postgis
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d427e6a0b4
Includes dox and regress test git-svn-id: http://svn.osgeo.org/postgis/trunk@13694 b70326c6-7e19-0410-871a-916f4a2858ee
293 lines
7.9 KiB
XML
293 lines
7.9 KiB
XML
<?xml version="1.0" encoding="UTF-8"?>
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<sect1 id="Temporal">
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<title>Temporal Support</title>
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<refentry id="ST_IsValidTrajectory">
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<refnamediv>
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<refname>ST_IsValidTrajectory</refname>
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<refpurpose>
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Returns <varname>true</varname> if the geometry is a valid trajectory.
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</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>boolean <function>ST_IsValidTrajectory</function></funcdef>
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<paramdef><type>geometry </type> <parameter>line</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>
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Tell if a geometry encodes a valid trajectory.
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Valid trajectories are encoded as LINESTRING with M value growing
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from each vertex to the next.
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</para>
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<para>
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Valid trajectories are expected as input to some spatio-temporal queries
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like <xref linkend="ST_ClosestPointOfApproach" />
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</para>
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<para>Availability: 2.2.0</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>
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-- A valid trajectory
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SELECT ST_IsValidTrajectory(ST_MakeLine(
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ST_MakePointM(0,0,1),
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ST_MakePointM(0,1,2))
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);
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t
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-- An invalid trajectory
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SELECT ST_IsValidTrajectory(ST_MakeLine(ST_MakePointM(0,0,1), ST_MakePointM(0,1,0)));
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NOTICE: Measure of vertex 1 (0) not bigger than measure of vertex 0 (1)
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st_isvalidtrajectory
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----------------------
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f
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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>
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<xref linkend="ST_ClosestPointOfApproach" />
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</para>
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</refsection>
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</refentry>
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<refentry id="ST_ClosestPointOfApproach">
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<refnamediv>
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<refname>ST_ClosestPointOfApproach</refname>
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<refpurpose>
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Returns the measure at which points interpolated along two lines are closest.
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</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>float8 <function>ST_ClosestPointOfApproach</function></funcdef>
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<paramdef><type>geometry </type> <parameter>track1</parameter></paramdef>
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<paramdef><type>geometry </type> <parameter>track2</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>
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Returns the smallest measure at which point interpolated along the given
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lines are at the smallest distance. Inputs must be valid trajectories as
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checked by <xref linkend="ST_IsValidTrajectory" />. Null is returned if
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the trajectories do not overlap on the M range.
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</para>
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<para>
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See <xref linkend="ST_LocateAlong" /> for getting the actual points at
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the given measure.
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</para>
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<para>Availability: 2.2.0</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>
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-- Return the time in which two objects moving between 10:00 and 11:00
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-- are closest to each other and their distance at that point
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WITH inp AS ( SELECT
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ST_AddMeasure('LINESTRING Z (0 0 0, 10 0 5)'::geometry,
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extract(epoch from '2015-05-26 10:00'::timestamptz),
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extract(epoch from '2015-05-26 11:00'::timestamptz)
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) a,
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ST_AddMeasure('LINESTRING Z (0 2 10, 12 1 2)'::geometry,
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extract(epoch from '2015-05-26 10:00'::timestamptz),
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extract(epoch from '2015-05-26 11:00'::timestamptz)
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) b
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), cpa AS (
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SELECT ST_ClosestPointOfApproach(a,b) m FROM inp
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), points AS (
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SELECT ST_Force3DZ(ST_GeometryN(ST_LocateAlong(a,m),1)) pa,
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ST_Force3DZ(ST_GeometryN(ST_LocateAlong(b,m),1)) pb
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FROM inp, cpa
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)
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SELECT to_timestamp(m) t,
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ST_Distance(pa,pb) distance
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FROM points, cpa;
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t | distance
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-------------------------------+------------------
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2015-05-26 10:45:31.034483+02 | 1.96036833151395
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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>
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<xref linkend="ST_IsValidTrajectory" />,
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<xref linkend="ST_DistanceCPA" />,
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<xref linkend="ST_LocateAlong" />,
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<xref linkend="ST_AddMeasure" />
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</para>
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</refsection>
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</refentry>
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<refentry id="ST_DistanceCPA">
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<refnamediv>
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<refname>ST_DistanceCPA</refname>
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<refpurpose>
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Returns the distance between closest points of approach in two trajectories.
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</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>float8 <function>ST_DistanceCPA</function></funcdef>
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<paramdef><type>geometry </type> <parameter>track1</parameter></paramdef>
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<paramdef><type>geometry </type> <parameter>track2</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>
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Returns the minimum distance two moving objects have ever been each-other.
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Inputs must be valid trajectories as checked by
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<xref linkend="ST_IsValidTrajectory" />.
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Null is returned if the trajectories do not overlap on the M range.
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</para>
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<para>Availability: 2.2.0</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>
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-- Return the minimum distance of two objects moving between 10:00 and 11:00
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WITH inp AS ( SELECT
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ST_AddMeasure('LINESTRING Z (0 0 0, 10 0 5)'::geometry,
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extract(epoch from '2015-05-26 10:00'::timestamptz),
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extract(epoch from '2015-05-26 11:00'::timestamptz)
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) a,
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ST_AddMeasure('LINESTRING Z (0 2 10, 12 1 2)'::geometry,
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extract(epoch from '2015-05-26 10:00'::timestamptz),
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extract(epoch from '2015-05-26 11:00'::timestamptz)
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) b
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)
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SELECT ST_DistanceCPA(a,b) distance FROM inp;
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distance
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------------------
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1.96036833151395
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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>
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<xref linkend="ST_IsValidTrajectory" />,
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<xref linkend="ST_ClosestPointOfApproach" />,
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<xref linkend="ST_AddMeasure" />,
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<xref linkend="geometry_distance_cpa" />
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</para>
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</refsection>
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</refentry>
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<refentry id="ST_CPAWithin">
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<refnamediv>
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<refname>ST_CPAWithin</refname>
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<refpurpose>
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Returns true if the trajectories' closest points of approach
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are within the specified distance.
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</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>float8 <function>ST_CPAWithin</function></funcdef>
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<paramdef><type>geometry </type> <parameter>track1</parameter></paramdef>
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<paramdef><type>geometry </type> <parameter>track2</parameter></paramdef>
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<paramdef><type>float8 </type> <parameter>maxdist</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>
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Checks whether two moving objects have ever been within the
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specified max distance.
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</para>
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<para>
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Inputs must be valid trajectories as checked by
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<xref linkend="ST_IsValidTrajectory" />.
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False is returned if the trajectories do not overlap on the M range.
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</para>
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<para>Availability: 2.2.0</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>
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WITH inp AS ( SELECT
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ST_AddMeasure('LINESTRING Z (0 0 0, 10 0 5)'::geometry,
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extract(epoch from '2015-05-26 10:00'::timestamptz),
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extract(epoch from '2015-05-26 11:00'::timestamptz)
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) a,
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ST_AddMeasure('LINESTRING Z (0 2 10, 12 1 2)'::geometry,
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extract(epoch from '2015-05-26 10:00'::timestamptz),
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extract(epoch from '2015-05-26 11:00'::timestamptz)
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) b
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)
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SELECT ST_CPAWithin(a,b,2), ST_DistanceCPA(a,b) distance FROM inp;
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st_cpawithin | distance
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--------------+------------------
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t | 1.96521473776207
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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>
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<xref linkend="ST_IsValidTrajectory" />,
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<xref linkend="ST_ClosestPointOfApproach" />,
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<xref linkend="ST_DistanceCPA" />,
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<xref linkend="geometry_distance_cpa" />
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</para>
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</refsection>
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</refentry>
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</sect1>
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