Some interesting facts:
equator -
SELECT
SDO_GEOM.SDO_DISTANCE(
SDO_GEOMETRY( 2001, 8307, SDO_POINT_TYPE(0,0, NULL), NULL, NULL),
SDO_GEOMETRY( 2001, 8307, SDO_POINT_TYPE(1,0, NULL), NULL, NULL),
0.05, 'unit=KM') as Dist8307,
SDO_GEOM.SDO_DISTANCE(
sdo_cs.transform(MDSYS.SDO_GEOMETRY(2001, 8307, MDSYS.SDO_POINT_TYPE(0,0, NULL), NULL, NULL),'USE_SPHERICAL', 3785),
sdo_cs.transform(MDSYS.SDO_GEOMETRY(2001, 8307, MDSYS.SDO_POINT_TYPE(1,0, NULL), NULL, NULL),'USE_SPHERICAL', 3785),
0.05, 'unit=KM') as Dist3785
FROM dual;
DIST8307 DIST3785
---------------------- ----------------------
111.319490793262 111.319490793274
Here is latitude 53 degrees
SELECT
SDO_GEOM.SDO_DISTANCE(
SDO_GEOMETRY( 2001, 8307, SDO_POINT_TYPE(0,53, NULL), NULL, NULL),
SDO_GEOMETRY( 2001, 8307, SDO_POINT_TYPE(1,53, NULL), NULL, NULL),
0.05, 'unit=KM') as Dist8307,
SDO_GEOM.SDO_DISTANCE(
sdo_cs.transform(MDSYS.SDO_GEOMETRY(2001, 8307, MDSYS.SDO_POINT_TYPE(0,53, NULL), NULL, NULL),'USE_SPHERICAL', 3785),
sdo_cs.transform(MDSYS.SDO_GEOMETRY(2001, 8307, MDSYS.SDO_POINT_TYPE(1,53, NULL), NULL, NULL),'USE_SPHERICAL', 3785),
0.05, 'unit=KM') as Dist3785
FROM dual;
DIST8307 DIST3785
---------------------- ----------------------
67.1366830300055 111.31949079327
It counts like on the equator!