[postgis-tickets] [SCM] PostGIS branch master updated. 3.1.0alpha3-8-g87812cb
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- Log -----------------------------------------------------------------
commit 87812cbd6d1e1348de83b82ee3980f6ef19083a1
Author: Martin Davis <mtnclimb at gmail.com>
Date: Fri Nov 27 22:00:04 2020 -0800
Improve Doc Ref for Overlay and Processing
diff --git a/doc/reference_overlay.xml b/doc/reference_overlay.xml
index 7188f67..6175aa9 100644
--- a/doc/reference_overlay.xml
+++ b/doc/reference_overlay.xml
@@ -31,9 +31,10 @@
<title>Description</title>
<para>
- Clips a geometry by a 2D box in a fast but possibly dirty way.
- The output geometry is not guaranteed to be valid (self-intersections for a polygon may be introduced).
- Topologically invalid input geometries do not result in exceptions being thrown.
+ Clips a geometry by a 2D box in a fast and tolerant but possibly invalid way.
+ Topologically invalid input geometries do not result in exceptions being thrown.
+ The output geometry is not guaranteed to be valid
+ (in particular, self-intersections for a polygon may be introduced).
</para>
<para>Performed by the GEOS module.</para>
@@ -114,7 +115,7 @@ on that same grid. This method requires GEOS-3.9.0 or higher.
<imageobject>
<imagedata fileref="images/st_symdifference01.png" />
</imageobject>
- <caption><para>The original linestrings shown together. </para></caption>
+ <caption><para>The input linestrings </para></caption>
</mediaobject>
</informalfigure>
</para>
@@ -135,7 +136,7 @@ on that same grid. This method requires GEOS-3.9.0 or higher.
</tbody>
</tgroup>
</informaltable>
-<para>Safe for 2D. This is same geometries as what is shown for st_symdifference</para>
+<para>The difference of 2D linestrings.</para>
<programlisting>SELECT ST_AsText(
ST_Difference(
'LINESTRING(50 100, 50 200)'::geometry,
@@ -148,16 +149,16 @@ st_astext
LINESTRING(50 150,50 200)
</programlisting>
-<para>When used in 3d doesn't quite do the right thing.</para>
-<programlisting>select ST_AsEWKT(
- ST_Difference(
- 'MULTIPOINT(-118.58 38.38 5,-118.60 38.329 6,-118.614 38.281 7)' :: geometry,
- 'POINT(-118.614 38.281 5)' :: geometry
- )
- );
+<para>The difference of 3D points.</para>
+<programlisting>SELECT ST_AsEWKT( ST_Difference(
+ 'MULTIPOINT(-118.58 38.38 5,-118.60 38.329 6,-118.614 38.281 7)' :: geometry,
+ 'POINT(-118.614 38.281 5)' :: geometry
+ ) );
+
st_asewkt
---------
-MULTIPOINT(-118.6 38.329 6,-118.58 38.38 5)</programlisting>
+MULTIPOINT(-118.6 38.329 6,-118.58 38.38 5)
+</programlisting>
</refsection>
<refsection>
@@ -207,11 +208,10 @@ Returns a geometry that represents the shared portion of geomA and geomB.
</refsynopsisdiv>
<refsection>
<title>Description</title>
- <para>Returns a geometry that represents the point set
- intersection of the Geometries.</para>
-
- <para>In other words - that portion of geometry A and geometry B
- that is shared between the two geometries.</para>
+ <para>Returns a geometry that represents the point-set
+ intersection of two geometries.
+ In other words, that portion of geometry A and geometry B
+ that is shared between the two geometries.</para>
<para>If the geometries do not share any space (are disjoint), then an empty geometry collection
is returned.</para>
@@ -351,7 +351,7 @@ from ST_GeomFromText('LINESTRING Z (2 2 6,1.5 1.5 7,1 1 8,0.5 0.5 8,0 0 10)') A
<refname>ST_Node</refname>
<refpurpose>
-Nodes a set of linestrings.
+Nodes a set of lines.
</refpurpose>
</refnamediv>
@@ -369,10 +369,14 @@ Nodes a set of linestrings.
<title>Description</title>
<para>
-Fully node a set of linestrings using the least possible number of nodes
-while preserving all of the input ones.
+Returns a (Multi)LineString representing the fully noded version of an input set of linestrings.
+The noding preserves all of the input nodes,
+and introduces the least possible number of new nodes.
+The resulting linework is dissolved (duplicate lines are removed).
</para>
+ <para>This is a good way to create fully-noded linework suitable for use as input to <xref linkend="ST_Polygonize" />.</para>
+
<para>&Z_support;</para>
<para>Performed by the GEOS module.</para>
<para>Availability: 2.0.0</para>
@@ -384,6 +388,7 @@ This may cause the resulting linestrings to have a different order and direction
</refsection>
<refsection>
<title>Examples</title>
+ <para>Noding a 3D LineString which self-intersects</para>
<programlisting>
SELECT ST_AsText(
ST_Node('LINESTRINGZ(0 0 0, 10 10 10, 0 10 5, 10 0 3)'::geometry)
@@ -392,6 +397,18 @@ output
-----------
MULTILINESTRING Z ((0 0 0,5 5 4.5),(5 5 4.5,10 10 10,0 10 5,5 5 4.5),(5 5 4.5,10 0 3))
</programlisting>
+
+ <para>Noding two LineStrings which share common linework.
+ Note that the result linework is dissolved.</para>
+ <programlisting>
+SELECT ST_AsText(
+ ST_Node('MULTILINESTRING ((2 5, 2 1, 7 1), (6 1, 4 1, 2 3, 2 5))'::geometry)
+ ) As output;
+output
+-----------
+MULTILINESTRING((2 5,2 3),(2 3,2 1,4 1),(4 1,2 3),(4 1,6 1),(6 1,7 1))
+ </programlisting>
+
</refsection>
<!-- Optionally add a "See Also" section -->
@@ -407,7 +424,7 @@ MULTILINESTRING Z ((0 0 0,5 5 4.5),(5 5 4.5,10 10 10,0 10 5,5 5 4.5),(5 5 4.5,10
<refentry id="ST_Split">
<refnamediv>
<refname>ST_Split</refname>
- <refpurpose>Returns a collection of geometries resulting by splitting a geometry.</refpurpose>
+ <refpurpose>Returns a collection of geometries created by splitting a geometry by another geometry.</refpurpose>
</refnamediv>
<refsynopsisdiv>
@@ -423,7 +440,9 @@ MULTILINESTRING Z ((0 0 0,5 5 4.5),(5 5 4.5,10 10 10,0 10 5,5 5 4.5),(5 5 4.5,10
<refsection>
<title>Description</title>
<para>
- The function supports splitting a line by (multi)point, (multi)line or (multi)polygon boundary, a (multi)polygon by line. The returned geometry is always a collection.
+ The function supports splitting a line by a (multi)point, (multi)line or (multi)polygon boundary,
+ or a (multi)polygon by line.
+ The returned geometry is always a collection.
</para>
<para>
diff --git a/doc/reference_processing.xml b/doc/reference_processing.xml
index 58707d8..7d6f3b7 100644
--- a/doc/reference_processing.xml
+++ b/doc/reference_processing.xml
@@ -1952,17 +1952,21 @@ POLYGON((19.9999999999997 79.9999999999999,33.0769230769229 60.3846153846152,138
<refsection>
<title>Description</title>
- <para>Creates a GeometryCollection containing possible
- polygons formed from the constituent linework of a set of
- geometries.</para>
+ <para>Creates a GeometryCollection containing the
+ polygons formed by the constituent linework of a set of geometries.
+ Input linework must be correctly noded for this function to work properly.</para>
<note>
- <para>Geometry Collections are often difficult to deal with with third party tools, so use ST_Polygonize in conjunction with <xref linkend="ST_Dump" /> to dump the polygons
- out into individual polygons.</para>
+ <para>
+ To ensure input is fully noded use <xref linkend="ST_Node" /> on the input geometry
+ before polygonizing.
+ </para>
</note>
<note>
- <para>Input linework must be correctly noded for this function to work properly</para>
+ <para>GeometryCollections are often difficult to deal with with third party tools.
+ Use <xref linkend="ST_Dump" /> to convert the polygonize result
+ into separate polygons.</para>
</note>
<para>Performed by the GEOS module.</para>
-----------------------------------------------------------------------
Summary of changes:
doc/reference_overlay.xml | 65 ++++++++++++++++++++++++++++----------------
doc/reference_processing.xml | 16 +++++++----
2 files changed, 52 insertions(+), 29 deletions(-)
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