INTERNATIONAL HYDROGRAPHIC ORGANIZATION USER’s HANDBOOK ON DATUM TRANSFORMATIONS INVOLVING WGS 84 3rd Edition, July 2003 (Last correction August 2008) Special Publication No. 60 Published by the International Hydrographic Bureau MONACO S-60 INTERNATIONAL HYDROGRAPHIC ORGANIZATION USER’s HANDBOOK ON DATUM TRANSFORMATIONS INVOLVING WGS 84 3rd Edition, July 2003 (Last correction August 2008) Special Publication No. 60 Published by the International Hydrographic Bureau 4, Quai Antoine 1er B.P. 445 MC 98011 Monaco cedex Tel : + 377 93 10 81 00 Fax : +377 93 10 81 40 E-mail: [email protected] MONACO TABLE OF CONTENTS Preface .............................................................................................................................................. 1 1. Introduction ................................................................................................................................. 3 2. WGS 84 Coordinate System ........................................................................................................ 4 3. WGS 84 Ellipsoid ........................................................................................................................ 6 4. WGS 84 Relationship with other Geodetic Systems ................................................................... 7 5. Accuracy of WGS 84 Coordinates ............................................................................................ 10 APPENDICES A. LIST OF REFERENCE ELLISPSOID NAMES AND PARAMETERS (USED FOR GENERATING DATUM TRANSFORMATIONS) ................................. A.1 B. DATUM TRANSFORMATIONS DERIVED USING SATELLITE-TIES TO GEODETIC DATUMS/SYSTEMS .......................................................................... B.1 C. DATUM TRANSFORMATIONS DERIVED USING NON-SATELLITE INFORMATION ............................................................................................................. C.1 D. MULTIPLE REGRESSION EQUATIONS FOR SPECIAL CONTINENTAL SIZE LOCAL GEODETIC DATUMS ........................................................................... D.1 E. FORMULAS AND PARAMETERS TO TRANSFORM WGS 72 COORDINATES TO WGS 84 COORDINATES ........................................................................................ E.1 F. LOCAL:REGIONAL DATUMS CROSS REFERENCE S-57 – S-60 .......................... F.1 Page intentionally left blank PREFACE IHO Publication S-60 USER’S HANDBOOK ON DATUM TRANSFORMATIONS INVOLVING WGS-84, contains transformation constants and formulas to relate local/regional geodetic datums to WGS-84. S-60 has been derived from a comprehensive Technical Report (TR8350.2, 3rd edition, 4 July 1997, corrected to 6/03) published by the National Imagery and Mapping Agency (NIMA) of the United States and kindly provided to the IHB to be published as an IHO Special Publication. Reproduction of formulas, transformation constants and related local/regional datums does not imply that these data have been officially adopted by the concerned States or by the IHO. However the IHO strongly supports any move to reference charts to WGS-84. Member States are encouraged to refine their own transformation parameters and to report these to the IHB. The US NIMA will continue to maintain the Technical Report from which S-60 has been produced . Corrections to the transformation constants and formulas will be published on the NIMA website (see below) and incorporated in S-60 in due course. Users requiring a copy of the complete NIMA Technical report should contact: Director National Imagery and Mapping Agency ATTN: ISDFR, Mail Stop D-82 4600 Sangamore Road Bethesda, MD 20816-5003 USA Fax: +1 301 226 7649 An electronic version of the complete Technical Report and corrections can be downloaded from http://www.nima.mil 1 Page intentionally left blank 2 1. INTRODUCTION IHO Technical Resolution B2.10 recommends that transformation notes be applied to all charts at scales larger than 1:500 000 to enable the navigator to use directly or to convert to chart datum and vice versa satellite-derived geographical positions which are in the World Geodetic System (WGS). The determination of the adjustment necessary to convert a position from the WGS 84 to the chart datum requires use of datum transformation constants which, by IHO Technical Resolution B1.1, are to be published by the International Hydrographic Bureau. Hydrographers or their topographic mapping counterparts may through national efforts, obtain geodetic data in port areas from which the specific values for the appropriate datum transformation notes for their charts can be derived. Such values may differ from those obtained by use of the parameters listed in this publication. Where that is the case, use of these specific observation derived values may be more appropriate. Indeed, as the NIMA Technical Report points out, the most accurate approach for obtaining the WGS 84 data or coordinates is to acquire satellite positions and the related data at the site of interest. Where such specific data exist, or where additional information on datums and ellipsoids used in local charts is held, IHO Member States are requested to inform the IHB and share that information in order that improved or additional datums transformation constants can be developed. Further, as the datum(s) utilized in the charts may not always be easily or clearly defined, cartographers are urged to take advice of geodetic experts when selecting methods appropriate to their specific datum transformation problem(s). The ellispsoidal constants (a and 1/f) for the local datums, used to compute transformation constants, are given in Appendix A. Appendix B lists the geodetic datums (reference systems) related to WGS 84 through satellite ties and the associated transformation parameters. Appendix C lists transformation constants which were derived through non-satellite-ties. Appendix D provides the Multiple Regression Equations parameters for continental size datums and for contiguous large land areas. Appendix E provides formulas and transformation parameters to convert WGS 72 coordinates to WGS 84 coordinates. Appendix F contains a list cross-referencing the identifications for local (regional) datums used in IHO Special Publication No. 57 (S-57) and in this publication. 3 2. WGS 84 COORDINATE SYSTEM 2.1 Definition The WGS 84 Coordinate System is a Conventional Terrestrial Reference System (CTRS). The definition of this coordinate system follows the criteria outlined in the International Earth Rotation Service (IERS) Technical Note 21. These criteria are repeated below: • It is geocentric, the center of mass being defined for the whole Earth including oceans and atmosphere. • Its scale is that of the local Earth frame, in the meaning of a relativistic theory of gravitation. • Its orientation was initially given by the Bureau International de l’Heure (BIH) orientation of 1984.0. • Its time evolution in orientation will create no residual global rotation with regards to the crust. The WGS 84 Coordinate System is a right-handed, earth fixed orthogonal coordinate system and is graphically depicted in Figure 2.1. 4 In Figure 2.1, the origin and axes are defined as follows: Origin = Earth’s center of mass Z-Axis = The direction of the IERS Reference Pole (IRP). This direction corresponds to the direction of the BIH Conventional Terrestrial Pole (CTP) (epoch 1984.0) with an uncertainty of 0.005”. X-Axis = Intersection of the IERS Reference Meridian (IRM) and the plane passing through the origin and normal to the Z-Axis. The IRM is coincident with the BIH Zero Meridian (epoch 1984.0) with an uncertainty of 0.005”. Y-Axis = Completes a right-handed, Earth-Centered Earth-Fixed (ECEF) orthogonal coordinate system. The WGS 84 Coordinate System origin also serves as the geometric center of the WGS 84 Ellipsoid and the Z-Axis serves as the rotational axis of this ellipsoid of revolution. Readers should note that the definition of the WGS 84 CTRS has not changed in any fundamental way. This CTRS continues to be defined as a right-handed, orthogonal and Earth-fixed coordinate system which is intended to be as closely coincident as possible, with the CTRS defined by the International Earth Rotation Service (IERS) or, prior to 1988, its predecessor, the Bureau International de l’Heure (BIH). 2.2 Realization An important distinction is needed between the definition of a coordinate system and the practical realization of a reference frame. Section 2.1 contains a definition of the WGS 84 Coordinate System. To achieve a practical realization of a global geodetic reference frame, a set of station coordinates must be established. A consistent set of station coordinates infers the location of an origin, the orientation of an orthogonal set of Cartesian axes, and a scale. In modern terms, a globally distributed set of consistent station coordinates represents a realization of an Earth- Centered Earth-Fixed (ECEF) Terrestrial Reference Frame (TRF). The original WGS 84 reference frame established in 1987 was realized through a set of Navy Navigation Satellite System (NNSS) or TRANSIT (Doppler) station coordinates. The main objective in the original effort was to align, as closely as possible, the origin, scale and orientation of the WGS 84 frame with the BIH Terrestrial System (BTS) frame at an epoch of 1984.0. The set of estimated station coordinates put into practical use had an uncertainty of 1-2 meters with respect to the BTS. Several independent studies have demonstrated that a systematic ellipsoid height bias (scale bias) exists between