From: Regina Obe Date: Fri, 27 Jun 2008 16:42:37 +0000 (+0000) Subject: same changes as made to trunk X-Git-Tag: 1.3.4rc1~55 X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=bb49fa79daacf2aa34ec05049b71b2638727a3e7;p=postgis same changes as made to trunk git-svn-id: http://svn.osgeo.org/postgis/branches/1.3@2813 b70326c6-7e19-0410-871a-916f4a2858ee --- diff --git a/doc/postgis.xml b/doc/postgis.xml index 2447f6853..e628bcc5a 100644 --- a/doc/postgis.xml +++ b/doc/postgis.xml @@ -2954,7 +2954,7 @@ VACUUM FULL ANALYZE mytable; Returns 1 (TRUE) if Geometry A is "spatially - within" Geometry B. + within" Geometry B. A has to be completely inside B. Performed by the GEOS module @@ -3167,7 +3167,7 @@ VACUUM FULL ANALYZE mytable; Geometry. The optional third parameter sets the number of segment used to approximate a quarter circle (defaults to 8). - Performed by the GEOS module + Performed by the GEOS module. OGC SPEC s2.1.1.3 @@ -3177,9 +3177,13 @@ VACUUM FULL ANALYZE mytable; ST_ConvexHull(geometry) - Returns a geometry that represents the convex hull of this - Geometry. - + The convex hull of a geometry represents the minimum closed geometry that encloses all geometries within the set. + It is usually used with MULTI and Geometry Collections. Although it is not an aggregate - you can use it in conjunction with ST_Collect to get the convex hull of a set of points. ST_ConvexHull(ST_Collect(somepointfield)). It is often used to determine an affected area based on a set of point observations. + + SELECT d.disease_type, ST_ConvexHull(ST_Collect(d.the_geom)) As the_geom + FROM disease_obs As d + GROUP BY d.disease_type + Performed by the GEOS module OGC SPEC s2.1.1.3 @@ -3191,7 +3195,8 @@ VACUUM FULL ANALYZE mytable; Returns a geometry that represents the point set - intersection of the Geometries. + intersection of the Geometries. + In other words - that portion of geometry A and geometry B that is shared between the two geometries. Performed by the GEOS module @@ -3200,6 +3205,14 @@ VACUUM FULL ANALYZE mytable; OGC SPEC s2.1.1.3 + + + ST_Shift_Longitude(geometry) + + Reads every point/vertex in every component of every feature in a geometry, and if the longitude coordinate is <0, adds 360 to it. The result would be a 0-360 version of the data to be plotted in a 180 centric map + + + ST_SymDifference(geometry A, geometry B) @@ -3230,7 +3243,7 @@ VACUUM FULL ANALYZE mytable; OGC SPEC s2.1.1.3 - + ST_Union(geometry, geometry) @@ -5364,7 +5377,9 @@ z' = z This method is a subcase of ST_ConvexHull - Return the convex hull of the ST_Geometry value. + The convex hull of a geometry represents the minimum geometry that encloses all geometries within the set. + It is usually used with MULTI and Geometry Collections. Although it is not an aggregate - you can use it in conjunction with ST_Collect to get the convex hull of a set of points. ST_ConvexHull(ST_Collect(somepointfield)). It is often used to determine an affected area based on a set of point observations. + SQL-MM 3: 5.1.16 @@ -5532,6 +5547,7 @@ z' = z This method is a subcase of Return an ST_Geometry value that represents the point set intersection of two ST_Geometry values. + In other words - that portion of geometry A and geometry B that is shared between the two geometries. SQL-MM 3: 5.1.18