PostGIS 1.5.8 Manual - Fedora Project Packages GIT repositories

PostGIS 1.5.8 Manual212 / 310-- A buffered point forcing approximation of (see diagram)-- 2 points per circle is poly with 8 sides (see diagram)SELECT ST_NPoints(ST_Buffer(ST_GeomFromText(’POINT(100 90)’), 50)) As ←↪promisingcircle_pcount,ST_NPoints(ST_Buffer(ST_GeomFromText(’POINT(100 90)’), 50, 2)) As lamecircle_pcount;promisingcircle_pcount | lamecircle_pcount------------------------+-------------------33 | 9--A lighter but lamer circle-- only 2 points per quarter circle is an octagon--Below is a 100 meter octagon-- Note coordinates are in NAD 83 long lat which we transformto Mass state plane meter and then buffer to get measurements in meters;SELECT ST_AsText(ST_Buffer(ST_Transform(ST_SetSRID(ST_MakePoint(-71.063526, 42.35785),4269), 26986),100,2)) As octagon;----------------------POLYGON((236057.59057465 900908.759918696,236028.301252769 900838.049240578,235957.59057465 900808.759918696,235886.879896532 900838.049240578,235857.59057465900908.759918696,235886.879896532 900979.470596815,235957.59057465 901008.759918696,236028.301252769 900979.470596815,236057.59057465 900908.759918696))See AlsoST_Collect, ST_DWithin, ST_SetSRID, ST_Transform, ST_Union7.9.2 ST_BuildAreaST_BuildArea — Creates an areal geometry formed by the constituent linework of given geometrySynopsisgeometry ST_BuildArea(geometry A);DescriptionCreates an areal geometry formed by the constituent linework of given geometry. The return type can be a Polygon or Multi-Polygon, depending on input. If the input lineworks do not form polygons NULL is returned. The inputs can be LINESTRINGS,MULTILINESTRINGS, POLYGONS, MULTIPOLYGONS, and GeometryCollections.This function will assume all inner geometries represent holesAvailability: 1.1.0 - requires GEOS >= 2.1.0.Examples