SDO_GEOM.SDO_CENTROID

Format

SDO_GEOM.SDO_CENTROID(     
  geom1  IN SDO_GEOMETRY,      
  dim1   IN SDO_DIM_ARRAY       
) RETURN SDO_GEOMETRY;

or

SDO_GEOM.SDO_CENTROID(     
  geom1  IN SDO_GEOMETRY,      
  tol    IN NUMBER       
) RETURN SDO_GEOMETRY;

Description

Returns a point geometry that is the centroid of a polygon, multipolygon, point, or point cluster. (The centroid is also known as the "center of gravity.")

For an input geometry consisting of multiple objects, the result is weighted by the area of each polygon in the geometry objects. If the geometry objects are a mixture of polygons and points, the points are not used in the calculation of the centroid. If the geometry objects are all points, the points have equal weight.

Parameters

geom1: Geometry object.
dim1: Dimensional information array corresponding to geom, usually selected from one of the xxx_SDO_GEOM_METADATA views (described in Geometry Metadata Views).
tol: Tolerance value (see Tolerance).

Usage Notes

The function returns a null value if geom1 is not a polygon, multipolygon, point, or point cluster, as identified by the SDO_GTYPE value in the SDO_GEOMETRY object.

If geom1 is a point, the function returns the point (the input geometry).

With geodetic data, this function is supported by approximations, as explained in Functions Supported by Approximations with Geodetic Data.

Depending on the shape and complexity of the input geometry, the returned point might not be on the surface of the input geometry.

Examples

The following example returns a geometry object that is the centroid of cola_c. (The example uses the definitions and data from Simple Example: Inserting_ Indexing_ and Querying Spatial Data.)

-- Return the centroid of a geometry.
SELECT c.name, SDO_GEOM.SDO_CENTROID(c.shape, m.diminfo) 
  FROM cola_markets c, user_sdo_geom_metadata m 
  WHERE m.table_name = 'COLA_MARKETS' AND m.column_name = 'SHAPE' 
  AND c.name = 'cola_c';

NAME                                                                            
--------------------------------                                                
SDO_GEOM.SDO_CENTROID(C.SHAPE,M.DIMINFO)(SDO_GTYPE, SDO_SRID, SDO_POINT(X, Y, Z)
--------------------------------------------------------------------------------
cola_c                                                                          
SDO_GEOMETRY(2001, NULL, NULL, SDO_ELEM_INFO_ARRAY(1, 1, 1), SDO_ORDINATE_ARRAY(
4.73333333, 3.93333333))