U.K. OFFSHORE OPERATORS ASSOCIATION (SURVEYING AND POSITIONING COMMITTEE) GUIDANCE NOTES ON THE USE OF CO-ORDINATE SYSTEMS IN DATA MANAGEMENT ON THE UKCS (DECEMBER 1999) Version 1.0c Whilst every effort has been made to ensure the accuracy of the information contained in this publication, neither UKOOA, nor any of its members will assume liability for any use made thereof. Copyright ã 1999 UK Offshore Operators Association Prepared on behalf of the UKOOA Surveying and Positioning Committee by Richard Wylde, The SIMA Consultancy Limited with assistance from: Roger Lott, BP Amoco Exploration Geir Simensen, Shell Expro A Company Limited by Guarantee UKOOA, 30 Buckingham Gate, London, SW1E 6NN Registered No. 1119804 England _____________________________________________________________________________________________________________________Page 2 CONTENTS 1. INTRODUCTION AND BACKGROUND .......................................................................3 1.1 Introduction ..........................................................................................................3 1.2 Background..........................................................................................................3 2. WHAT HAS HAPPENED AND WHY ............................................................................4 2.1 Longitude 6°W (ED50) - the Thunderer Line .........................................................4 3. GUIDANCE FOR DATA USERS ..................................................................................6 3.1 How will we map the UKCS? ................................................................................6 3.2 Mappers and Interpreters .....................................................................................8 3.3 Data Management................................................................................................9 East of the Thunderer Line ...................................................................................9 West of the Thunderer Line ................................................................................10 Data crossing the Thunderer Line.......................................................................11 3.4 Data Loaders.....................................................................................................11 3.5 Applications usage .............................................................................................11 4. GUIDANCE FOR SOFTWARE VENDORS.................................................................13 4.1 Data Storage......................................................................................................13 4.2 Co-ordinate System Definitions ..........................................................................13 4.2 Co-ordinate System Transformations..................................................................14 4.4 Mapping…………………………………………………………………………………..15 4.5 Reporting…………………………………………………………………………………16 5. GUIDANCE FOR DATA VENDORS ...........................................................................17 5.1 Future Data........................................................................................................17 5.2 Legacy Data.......................................................................................................17 Defined data.......................................................................................................18 Measured data ...................................................................................................18 ANNEXES ...........................................................................................................................19 Annex A - DTI Gazette Notice (in full)...........................................................................1 Annex B - Post Gazette description of UKCS licence areas ..........................................1 Annex C - Co-ordinates of Blocks immediately West and adjacent to the Thunderer Line ………………………………………………………………………………………………1 Annex D - Reference Information .................................................................................1 Annex E - Incorporation of the EPSG Co-ordinate System Description in UKOOA Positioning (P) formats.................................................................................................1 Annex F - A guide to co-ordinate system geodesy ........................................................1 Annex G - Glossary......................................................................................................1 ____________________________________________________________________________________________ UKOOA Guidance Notes on use of co-ordinate systems in data management on the UKCS. November 1999 _____________________________________________________________________________________________________________________Page 3 1. INTRODUCTION AND BACKGROUND 1.1 Introduction This guidance note concerns the management of spatial data for UK Continental Shelf (UKCS) petroleum operations. In December 1999, the oil and gas licensing division of the Department of Trade and Industry (DTI) published a notice in both the London Gazette and the Edinburgh Gazette, which clarified the co-ordinate systems to which licence boundaries on the UKCS were referred. The UKOOA Surveying and Positioning (S&P) Committee recognises that some data management issues may arise out of the Gazette notice. This document has been produced to provide some guidance in handling co-ordinate integrity issues that may be encountered. In writing such "Best Practice" guidance, it is impossible to strike the correct tone for every audience. Comments and suggestions have had to assume limited knowledge in the area of geodesy on the part of the user. Therefore, within this document, there is both a glossary of terms (see annex G) and a guide to co-ordinate geodesy (see annex F) that may assist with the technical nature of some of the comments. We cannot cover all of the possible issues and thereby give explicit recommendations to everyone and so we have decided to split the issues into broad groupings. It should be noted that many of the individual comments might be relevant in other areas also. It is therefore recommended that the document be studied in its entirety. In addition, for completeness of the document, there is an element of repetition of information. 1.2 Background Increasing UKCS activity to the west of Britain has led the UKOOA Surveying and Positioning Committee and the UK Government geodetic advisors (Hydrographic Office and Ordnance Survey) to express concern that the current definition of a geographic co-ordinate system for offshore concession boundaries, based on “European Datum”, is imprecise. Although adequate for describing position in the North Sea, in areas to the west of Britain it has the potential to lead to serious difficulties in inter company and possibly international unitisation of cross border oil and gas fields. With DTI's backing, a working group was formed to recommend a technically acceptable definition and procedures for removing the ambiguity. The working group consulted widely on this issue, seeking and obtained support from Oil Companies, both operators and non- operators, seismic and positioning contractors, the Legal, Exploration and S&P Committees of UKOOA as well as the UKOOA Management Group. The working group's recommendations were submitted to the DTI Licensing Division, and the instrument chosen for their introduction was by publication of their content in both the London Gazette and the Edinburgh Gazette. Two workshops were run jointly with the DTI to examine the data management issues that may result from the Gazettal notice and provide a basis for these guidance notes. Data managers from both Oil and Service companies were represented, as were seismic data acquisition companies, consulting companies, data vendors and software vendors. The Gazette notice, as issued by the DTI early December 1999, is printed in full in annex A. ____________________________________________________________________________________________ UKOOA Guidance Notes on use of co-ordinate systems in data management on the UKCS. November 1999 _____________________________________________________________________________________________________________________Page 4 2. WHAT HAS HAPPENED AND WHY Co-ordinates describing a position on the earth are only unambiguous if the co-ordinate system to which they are referenced is identified. Geographical co-ordinate system components are geodetic datum and ellipsoid. Projected co-ordinate systems are Geographical Co-ordinate Systems with a projection transformation applied. See annex F for an overview of co-ordinate systems and annex G for a glossary of terms. Petroleum licence boundary co-ordinates have previously been referenced to “European Datum”. This term is not a precise one. Several versions of European Datum (ED) exist. Generally, in UKCS petroleum operations ED has been assumed to be the first (1950) iteration of European Datum (ED50). This was originally published to unify the co-ordinate systems used in mainland Western Europe and its extrapolation offshore becomes increasingly ambiguous as distance from the reference points used in its calculation increases. In the North Sea these ambiguities are of scientific curiosity only and not significant to petroleum operations. However, to the West of Shetland and even further west, differences arising from different technical assumptions quickly become very large. Potentially,