This document has been converted from the original publication. The original document was not published in Geophysics. A reproduction of the original document can be obtained from the SEG Bookstore. The SI Metric System of Units And 1 SEG Tentative Metric Standard SEG METRICATION SUBCOMMITTEE 1 Copyright 1980, Society of Exploration Geophysicist. All Rights reserved. CONTENTS FOREWORD.............................................................................................................................................. V PART 1: SI — THE INTERNATIONAL SYSTEM OF UNITS ........................................................1 1.1 INTRODUCTION..............................................................................................................................1 1.2 SI UNITS AND UNIT SYMBOLS3 .....................................................................................................1 1.2.1 SI Units..................................................................................................................................1 1.2.2 SI Unit Prefixes8....................................................................................................................2 1.3 APPLICATION OF THE METRIC SYSTEM.......................................................................................10 1.3.1 General ...............................................................................................................................10 1.3.2 Style and Usage...................................................................................................................10 1.3.3 Non-SI Units........................................................................................................................10 1.3.4 Usage for Selected Quantities.............................................................................................10 1.3.4.1 Mass, Force, and Weight.................................................................................................10 1.3.4.2 Linear Dimensions ..........................................................................................................11 1.3.4.3 Temperature ....................................................................................................................11 1.3.4.4 Time ................................................................................................................................11 1.3.4.5 Angles .............................................................................................................................12 1.3.4.6 Volume............................................................................................................................12 1.3.4.7 Energy.............................................................................................................................12 1.3.4.8 Energy, Torque, and Bending Moment...........................................................................12 1.3.4.9 Pressure and Stress..........................................................................................................12 1.3.4.10 Units and Names to be Avoided or Abandoned..........................................................12 1.4 RULES FOR CONVERSION AND ROUNDING3 ................................................................................13 1.4.1 General ...............................................................................................................................13 1.4.1.1 Conversion Factors .........................................................................................................13 1.4.1.2 Conversion of Quantities ................................................................................................13 1.4.1.3 Conversion Procedure.....................................................................................................13 1.4.1.4 Accuracy and Rounding..................................................................................................13 1.4.1.5 General Conversion.........................................................................................................13 1.4.1.6 Special Cases ..................................................................................................................14 1.4.2 Significant Digits.................................................................................................................14 1.4.2.1 Precision of Conversion..................................................................................................14 1.4.2.2 Significant Digit..............................................................................................................14 1.4.2.3 Importance of Zeros........................................................................................................15 1.4.2.4 Data of Varying Precision...............................................................................................15 1.4.2.5 Rounding Values10 ..........................................................................................................16 1.4.2.6 Conversion of Linear Dimensions of Interchangeable Parts...........................................16 1.4.3 Other Units..........................................................................................................................17 1.4.3.1 Temperature ....................................................................................................................17 1.4.3.2 Pressure or Stress ............................................................................................................17 1.4.3.3 Special Length Unit — the Vara.....................................................................................17 1.5 SPECIAL TERMS AND QUANTITIES INVOLVING MASS AND AMOUNT OF SUBSTANCE................18 1.6 MENTAL GUIDES FOR USING METRIC UNITS..............................................................................19 1.7 REFERENCES ...........................................................................................................................19 APPENDIX A TERMINOLOGY 3 .....................................................................................................21 APPENDIX B SI UNITS3 ...................................................................................................................23 B.1 Advantages of SI Units............................................................................................................23 B.2 Non-SI Metric Units................................................................................................................24 ii B.3 SI Base Unit Definitions..........................................................................................................24 3 B.4 Definitions of SI Derived Units Having Special Names ........................................................25 3 8 APPENDIX C STYLE GUIDE FOR METRIC USAGE , ...............................................................27 C.1 STYLE GUIDE........................................................................................................................27 C.1.1 Rules for Writing Metric Quantities ...............................................................................27 C.1.2 Plurals and Fractions.......................................................................................................28 C.1.3 Periods.............................................................................................................................28 C.1.4 The Decimal Marker .......................................................................................................28 C.1.5 Grouping of Numbers .....................................................................................................28 C.1.6 Spacing............................................................................................................................28 C.1.7 Powers.............................................................................................................................29 C.1.8 Compound Units .............................................................................................................29 C.1.9 SI Prefix Usage ...............................................................................................................29 C.1.10 Spelling of Vowel Pairs ..................................................................................................30 C.1.11 Complicated Expressions................................................................................................30 C.1.12 Attachment......................................................................................................................31 C.1.13 Equations.........................................................................................................................31 C.1.14 Pronunciation of Metric Terms .......................................................................................31 C.1.15 Typewriting Recommendations ......................................................................................31 APPENDIX D GENERAL CONVERSION FACTORS ....................................................................33 D.1 General ...................................................................................................................................33 D.2 Notation...................................................................................................................................33 D.3 Organization ...........................................................................................................................34