PostGIS 1.5.8 Manual - Fedora Project Packages GIT repositories

PostGIS 1.5.8 Manual94 / 310DescriptionReturns the closure of the combinatorial boundary of this Geometry. The combinatorial boundary is defined as described insection 3.12.3.2 of the OGC SPEC. Because the result of this function is a closure, and hence topologically closed, the resultingboundary can be represented using representational geometry primitives as discussed in the OGC SPEC, section 3.12.2.Performed by the GEOS moduleImportantDo not call with a GEOMETRYCOLLECTION as an argumentThis method implements the OpenGIS Simple Features Implementation Specification for SQL 1.1. OGC SPEC s2.1.1.1This method implements the SQL/MM specification. SQL-MM 3: 5.1.14This function supports 3d and will not drop the z-index.ExamplesSELECT ST_AsText(ST_Boundary(ST_GeomFromText(’LINESTRING(1 1,0 0, -1 1)’)));st_astext-----------MULTIPOINT(1 1,-1 1)SELECT ST_AsText(ST_Boundary(ST_GeomFromText(’POLYGON((1 1,0 0, -1 1, 1 1))’)));st_astext----------LINESTRING(1 1,0 0,-1 1,1 1)--Using a 3d polygonSELECT ST_AsEWKT(ST_Boundary(ST_GeomFromEWKT(’POLYGON((1 1 1,0 0 1, -1 1 1, 1 1 1))’)));st_asewkt-----------------------------------LINESTRING(1 1 1,0 0 1,-1 1 1,1 1 1)--Using a 3d multilinestringSELECT ST_AsEWKT(ST_Boundary(ST_GeomFromEWKT(’MULTILINESTRING((1 1 1,0 0 0.5, -1 1 1),(1 10.5,0 0 0.5, -1 1 0.5, 1 1 0.5) )’)));←↪st_asewkt----------MULTIPOINT(-1 1 1,1 1 0.75)See AlsoST_ExteriorRing, ST_MakePolygon7.4.3 ST_CoordDimST_CoordDim — Return the coordinate dimension of the ST_Geometry value.