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EX COVER ........................................................................................................................................................................... 1 Copyright notice............................................................................................................................................................ 1 Revisions ....................................................................................................................................................................... 1 Acknowledgements....................................................................................................................................................... 2 Sponsors........................................................................................................................................................................ 2 Summary Contents........................................................................................................................................................ 3 List of figures - images, tables and diagrams .................................................................................................................... 4 Introduction ...................................................................................................................................................................... 5 1. Coordinate Systems and Geodesy ............................................................................................................................ 7 1.1 The Origin – Reference Surfaces and Elevations in Mapping ........................................................................... 7 1.1.1 MSL, Elevation and Height ............................................................................................................................... 8 1.1.2 Coordinate Systems ......................................................................................................................................... 8 1.1.3 Geographical coordinates ................................................................................................................................ 9 1.2 Principles of Geodesy – The forgotten Earth science! .................................................................................... 10 1.2.1 Geodesy.......................................................................................................................................................... 10 1.2.2 Geodetic Datum ............................................................................................................................................ 11 1.2.3 Distortions in the Ellipsoidal Model ............................................................................................................... 15 Points to Ponder ........................................................................................................ Error! Bookmark not defined. 1.3 Principles of Cartography – ’s ‘ qu Wo ld’! s ?............................................................................. 17 1.3.1 Projection Categories ..................................................................................................................................... 17 1.3.2 Mapping Parameters...................................................................................................................................... 18 1.3.3 Distortions in Mapping................................................................................................................................... 18 1.3.4 Azimuth Distortion ......................................................................................................................................... 19 1.3.5 Scale Distortion ............................................................................................................................................. 20 2. Changing from One Map System to Another.......................................................................................................... 21 2.1 Ellipsoids and datums ........................................................................................................................................... 21 3. True North, Grid North, Convergence Summary & Exercises ................................................................................... 23 3.1 Map projections .................................................................................................................................................... 23 Some simple worked examples: ............................................................................................................................. 25 4 h E h’s M gn c F ld ......................................................................................................................................... 27 4.1 Basic Outline ................................................................................................................................................... 27 4.2 V ons n h E h’s M gn c F ld ......................................................................................................... 28 4.3 Magnetic Observatory Distribution ................................................................................................................ 31 4.4 Diurnal Variation ............................................................................................................................................. 31 5. Principles of MWD and Magnetic Spacing ............................................................................................................. 33 5.1 Measurement While Drilling (MWD) .............................................................................................................. 33 5.1 Data Recovery ................................................................................................................................................. 34 5.2 MWD Magnetic Spacing.................................................................................................................................. 36 5.2.1 Drill String Magnetic Interference ................................................................................................................. 36 5.2.2 Pole Strength Values ...................................................................................................................................... 36 5.2.3 Azimuth Error ................................................................................................................................................. 36 5.2.4 NMDC Length Selection Charts ...................................................................................................................... 36
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