CO-ORDINATE SYSTEMS FOR UKCS PETROLEUM EXPLORATION AND PRODUCTION LICENCES

It has been drawn to the Department’s attention that there may be some uncertainty as to petroleum licence boundary co-ordinate description across the UKCS. This notice sets out the Department’s interpretation of licence boundary co-ordinates in existing licences and confirms the position, until further notice, as to the co-ordinate systems that will apply in the case of future awards of licences. These are to be determined in accordance with the principles set out below. Specific geographical co-ordinate systems are identified for use in various areas. Transformations between the relevant co-ordinate systems are defined. Through a combination of the declared co-ordinate systems and declared transformations, petroleum industry users can unambiguously merge positional data throughout the UK and its continental shelf. The recommendations are made explicitly for petroleum licence boundary co-ordinate decription but are also suitable for use for petroleum data management purposes. The Oil and Gas Directorate of the Department of Trade and Industry advise that: 1. To the east of 6 degrees West longitude, “European Datum” means the first adjustment dated 1950, usually referred to as ED50. For UKCS petroleum exploration and production purposes ED50 is equivalent to ETRF89 with the “Common Offshore” transformation applied. 2. To the west of 6 degrees West longitude, the co-ordinate system for UKCS petroleum exploration is ETRF89. UKCS licence boundaries to the west of 6 degrees West longitude follow a latitude and longitude graticule based on the ETRF89 system, except for licences abutting 6 degrees West longitude on their eastern side where special provision is required to ensure exact adjacency to licences to the east based on ED50. 3. The current practice of using the Ordnance Survey (R) GB National Grid as the co-ordinate systems for petroleum exploration and production in landward areas of Great Britain is maintained. 4. The following geodetic transformations are recognised as defining the relationships between the various co-ordinate systems required for UKCS petroleum exploration and production purposes: 4.1 the difference between the WGS84 and ETRF89 co-ordinate systems is not significant and WGS 84 co-ordinate values can be assumed to be equivalent to ETRF89. This is equivalent to the transformation between WGS84 and ETRF89 being taken to be zero. 4.2 the recommended relationship between ED50 and WGS84 or ETRF89 is the “Common Offshore” transformation. The Common Offshore transformation is an operation using the position vector transformation method and the following specified set of Helmert transformation parameters for changing co-ordinates between the WGS84 and ED50 co-ordinate systems on the UKCS. For petroleum exploration and production purposes the transformation can also be used between the ETRF89 and ED50 co-ordinate systems.

“Common Offshore” transformation parameters from ETRF89 (WGS84) to ED50
dX(m)	dY(m)	dZ(m)	RotX	RotY	RotZ	Scale (ppm)
+89.5	+93.8	+123.1	0	0	+0.156	-1.200

Test Point using Common Offshore transformation parameters:

Latitude	Longitude	Ellipsoid Height
ETRF89 (WGS84)	53- 00- 00.000  N	01- 00- 00.000  E	50.00 m
ED50	53- 00- 02.887  N	01- 00- 05.101  E	2.72 m

4.3 the relationship between OSGB36 (OSGB National Grid) and ETRF89 is the OSGB petroleum transformation. The OSGB petroleum transformation is an operation using the position vector transformation method and the following specified set of Helmert transformation parameters for changing co-ordinates between OSGB36 and ETRF89 or WGS84 co-ordinate systems. The transformation has an accuracy of typically 2 metres and is no worse than approximately 4 metres throughout Britain. A more accurate transformation is available from the Ordnance Survey.

OSGB petroleum transformation parameters from ETRF89 (WGS84) to OSGB36
dX(m)	dY(m)	dZ(m)	RotX	RotY	RotZ	Scale (ppm)
-446.448	+125.157	-542.060	-0.150	-0.247	-0.842	+20.4894

Test Point using OSGB petroleum transformation parameters:

Latitude	Longitude	Ellipsoid Height
ETRF89 (WGS84)	53- 00- 00.000  N	01- 00- 00.000  E	50.00 m
OSGB36	52- 59- 58.719  N	01- 00- 06.490  E	3.99 m

4.4 the relationship between OSGB36 and ED50 is the concatenation of the OSGB36 to ETRF89 and ETRF89 to ED50 transformations in recommendations 4.2 and 4.3 above, known as the UKOOA landward/seaward transformation.

UKOOA landward/seaward transformation parameters from OSGB36 to ED50
dX(m)	dY(m)	dZ(m)	RotX	RotY	RotZ	Scale (ppm)
+535.948	-31.357	+665.160	0.150	0.247	0.998	-21.689

Test Point using UKOOA landward/seaward transformation parameters:

Latitude	Longitude	Ellipsoid Height
OSGB36	52- 59- 58.719  N	01- 00- 06.490  E	3.99 m
ED50	53- 00- 02.887  N	01- 00- 05.101  E	2.72 m

It is recognised that slightly different transformations have been used historically. In general, for oil exploration and production purposes these transformations are not significantly different. In certain cases involving existing unitisation across licence boundaries it will be necessary to retain the use of the transformation adopted by the unit operator to ensure that there is no change in equity attributable to revised co-ordinate system practices. Further details and guidelines are published on the DTI and UKOOA websites (www.og.dti.gov.uk, www.ukooa.co.uk).