PostGIS 1.5.8 Manual - Fedora Project Packages GIT repositories

PostGIS 1.5.8 Manual104 / 310DescriptionReturns TRUE if this LINESTRING is both ST_IsClosed (ST_StartPoint((g)) ~= ST_Endpoint((g))) and ST_IsSimple(does not self intersect).This method implements the OpenGIS Simple Features Implementation Specification for SQL 1.1. 2.1.5.1This method implements the SQL/MM specification. SQL-MM 3: 7.1.6NoteSQL-MM defines the result of ST_IsRing(NULL) to be 0, while PostGIS returns NULL.ExamplesSELECT ST_IsRing(the_geom), ST_IsClosed(the_geom), ST_IsSimple(the_geom)FROM (SELECT ’LINESTRING(0 0, 0 1, 1 1, 1 0, 0 0)’::geometry AS the_geom) AS foo;st_isring | st_isclosed | st_issimple-----------+-------------+-------------t | t | t(1 row)SELECT ST_IsRing(the_geom), ST_IsClosed(the_geom), ST_IsSimple(the_geom)FROM (SELECT ’LINESTRING(0 0, 0 1, 1 0, 1 1, 0 0)’::geometry AS the_geom) AS foo;st_isring | st_isclosed | st_issimple-----------+-------------+-------------f | t | f(1 row)See AlsoST_IsClosed, ST_IsSimple, ST_StartPoint, ST_EndPoint7.4.14 ST_IsSimpleST_IsSimple — Returns (TRUE) if this Geometry has no anomalous geometric points, such as self intersection or self tangency.Synopsisboolean ST_IsSimple(geometry geomA);DescriptionReturns true if this Geometry has no anomalous geometric points, such as self intersection or self tangency. For more informationon the OGC’s definition of geometry simplicity and validity, refer to "Ensuring OpenGIS compliancy of geometries"NoteSQL-MM defines the result of ST_IsSimple(NULL) to be 0, while PostGIS returns NULL.