I'm using PostGIS 1.5.2, with geometries in SRID:900913. I need create a circles using a list of points as centre, with a radius of 600 kilometers. I'm using this query:
INSERT INTO circles (geom) ( SELECT ST_Buffer(point, 600000, 'quad_segs=8') FROM points );
But circles created have not 600 kilometers of radius (radius is near this length, but not exactly).
Are there other methods to create circles in PostGIS?
NOTE: Information represented is from Spain. Correct projection is 4326, but client use Google rasters, so I am storing data in 900913 to avoid reprojections and increase performance.