PostGIS 1.5.8 Manual - Fedora Project Packages GIT repositories

PostGIS 1.5.8 Manual229 / 310DescriptionReturns the smallest circle polygon that can fully contain a geometry.NoteThe circle is approximated by a polygon with a default of 48 segments per quarter circle. This number can be increasedwith little performance penalty to obtain a more accurate result.It is often used with MULTI and Geometry Collections. Although it is not an aggregate - you can use it in conjunction withST_Collect to get the minimum bounding cirlce of a set of geometries. ST_MinimumBoundingCircle(ST_Collect(somepointfield)).The ratio of the area of a polygon divided by the area of its Minimum Bounding Circle is often referred to as the Roeck test.Availability: 1.4.0 - requires GEOSExamplesSELECT d.disease_type,ST_MinimumBoundingCircle(ST_Collect(d.the_geom)) As the_geomFROM disease_obs As dGROUP BY d.disease_type;Minimum bounding circle of a point and linestring. Using 8 segs to approximate a quarter circleSELECT ST_AsText(ST_MinimumBoundingCircle(ST_Collect(ST_GeomFromEWKT(’LINESTRING(55 75,125 150)’),ST_Point(20, 80)), 8)) As wktmbc;wktmbc-----------POLYGON((135.59714732062 115,134.384753327498 102.690357210921,130.7941629693790.8537670908995,124.963360620072 79.9451031602111,117.116420743937 ←↪70.3835792560632,107.554896839789 62.5366393799277,96.6462329091006 ←↪56.70583703063,84.8096427890789 53.115246672502,72.5000000000001 ←↪51.9028526793802,60.1903572109213 53.1152466725019,48.3537670908996 ←↪56.7058370306299,37.4451031602112 62.5366393799276,27.8835792560632 ←↪←↪