Accuracy Of Sdo_Cs.Transform From SRID 81989 To 8307

(Doc ID 1384158.1)

Last updated on FEBRUARY 08, 2017

Applies to:

Oracle Spatial - Version: 11.2.0.1 to 11.2.0.3 - Release: 11.2 to 11.2
Information in this document applies to any platform.

Symptoms

A Coordinate Transformation from SRID 81989 to 8307 gives inaccurate results

create table eq81989 (id number, geom mdsys.sdo_geometry);

insert into eq81989 values (1, MDSYS.SDO_GEOMETRY(2001, 81989, SDO_POINT_TYPE(505601, 161495, NULL), NULL, NULL));
commit;

INSERT INTO USER_SDO_GEOM_METADATA
VALUES (
'EQ81989',
'GEOM',
MDSYS.SDO_DIM_ARRAY(
MDSYS.SDO_DIM_ELEMENT('Longitude', 0, 1505601, .05),
MDSYS.SDO_DIM_ELEMENT('Latitude', 0, 1161495, .05)
),
81989
);
commit;

select SDO_CS.transform(geom,8307) from eq81989;

SDO_CS.TRANSFORM(GEOM,8307)(SDO_GTYPE, SDO_SRID, SDO_POINT(X, Y, Z), SDO_ELEM_IN
--------------------------------------------------------------------------------
SDO_GEOMETRY(2001, 8307, SDO_POINT_TYPE(-.48524373, 51.3426846, NULL), NULL, NULL)


We get: -.48524373, 51.3426846
Expecting: -.48523482, 51.34273915

We expect those values because:
The Ordnance Survey of Great Britain offers an online system for performing transformation between OSGB36 and WGS84:
http://gps.ordnancesurvey.co.uk/convert.asp as you mentioned

From the website using
Easting: 505601 and Northing: 161495
We get: -0.48523482, 51.34273915

Cause

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