PostGIS 1.5.8 Manual - Fedora Project Packages GIT repositories

PostGIS 1.5.8 Manual113 / 310Examples-- Extract all POINTs from a LINESTRINGSELECT ST_AsText(ST_PointN(column1,generate_series(1, ST_NPoints(column1))))FROM ( VALUES (’LINESTRING(0 0, 1 1, 2 2)’::geometry) ) AS foo;st_astext------------POINT(0 0)POINT(1 1)POINT(2 2)(3 rows)--Example circular stringSELECT ST_AsText(ST_PointN(ST_GeomFromText(’CIRCULARSTRING(1 2, 3 2, 1 2)’),2));st_astext----------POINT(3 2)See AlsoST_NPoints7.4.26 ST_SRIDST_SRID — Returns the spatial reference identifier for the ST_Geometry as defined in spatial_ref_sys table.Synopsisinteger ST_SRID(geometry g1);DescriptionReturns the spatial reference identifier for the ST_Geometry as defined in Section 4.3.1 table.Notespatial_ref_sys table is a table that catalogs all spatial reference systems known to PostGIS and is used for transformationsfrom one spatial reference system to another. So verifying you have the right spatial reference system identifier isimportant if you plan to ever transform your geometries.This method implements the OpenGIS Simple Features Implementation Specification for SQL 1.1. s2.1.1.1This method implements the SQL/MM specification. SQL-MM 3: 5.1.5This method supports Circular Strings and Curves