Use Openlayers2 Circle, 900913 into the coordinate system of 4326, you must draw a circle before calling the method, you will need to turn into a point of coordinate system. Otherwise, the default number of sides 45 degrees.
new OpenLayers.Geometry.Polygon.createRegularPolygon () on plane coordinates and spherical coordinates identified. Openlayer only recognizes sphere coordinate, does not recognize geographic coordinates, so you need to first circle the center point of the first transformation point before painting, otherwise circular drawn is problematic.
4326 and 900913 Detailed coordinate
"EPSG: 4326" character, is to describe the latitude and longitude coordinates, see "EPSG: 900931" is described as "rice" do units of x / y coordinates.
Spherical Mercator EPSG codes used in the OpenLayers: 900913.
