GMT - GENERIC MAPPING TOOLS Data Processing and Plotting ! 4th Year Honours Course Unit (25 hours) University of Sydney Maria Seton and Jo Whittaker GMT Honours Course - University of Sydney" 1 TABLE OF CONTENTS 1. Introduction" 7 The Course" 7 What is GMT?" 7 2. Spatial Data" 10 Vector Data" 12 Vector Data Storage (File Formats)!................................................................14 Raster Data" 15 Colour" 20 Colour Models!..................................................................................................22 RGB Colour Model!...........................................................................................23 CMYK Colour Model!........................................................................................24 HSV Colour Model!............................................................................................25 3. Historical View of Spatial Data" 29 4. Coordinate Systems" 39 Cartesian Coordinate System" 39 Geographic Coordinate System!.....................................................................39 Latitude!.............................................................................................................44 Longitude!.........................................................................................................45 Determining Longitude!...................................................................................47 Measuring Distance!.........................................................................................48 5. Geodetics" 50 Geometric Earth Models" 50 GMT Honours Course - University of Sydney" 2 Historical Note on the Shape of the Earth!.....................................................53 Figure of the Earth!...........................................................................................55 Ellipsoid!............................................................................................................55 Geoid!.................................................................................................................57 Projections!.......................................................................................................58 Distortion Properties!.......................................................................................60 Projection Parameters!....................................................................................61 Projection Surfaces!.........................................................................................62 Cylindrical Projections!....................................................................................63 Conical Projections!.........................................................................................71 Azimuthal or Planar Projections!....................................................................74 Pseudo or Miscellaneous Projections!...........................................................79 Summary" 81 6. Map Making" 84 Basic UNIX" 84 Command Line Navigation!.............................................................................84 Find out where you are [pwd]!.........................................................................84 List the contents of the current directory [ls]!...............................................84 Change Directory [cd]!.....................................................................................85 Making Directories!..........................................................................................85 Deleting Files and Directories!........................................................................85 Copying and Moving!.......................................................................................86 Other useful UNIX commands and processes!..............................................86 Shell redirection: [<] [>] [>>]!...........................................................................86 Pipes: [ | ]!..........................................................................................................86 Permissions:!....................................................................................................87 GMT Honours Course - University of Sydney" 3 UNIX Summary!.................................................................................................87 GMT Fundamentals" 89 GMT Default Parameters!.................................................................................89 Map boundary parameters in GMT: GMT defaults!........................................93 Defining geodetic parameters in GMT: GMT Defaults!..................................95 Measurement Units in GMT: GMT Defaults!...................................................95 Creating a map boundary in GMT: -B option!.................................................95 Defining the map frame in GMT: -R option!....................................................98 Defining map projections in GMT: -J option!................................................100 Linear projection -Jx or -JX!..........................................................................100 Mercator projection -JM or -Jm!....................................................................101 UTM projection -JU or -Ju!.............................................................................101 Conical projections!.......................................................................................102 Azimuthal projections!...................................................................................102 Thematic (global) projections!.......................................................................103 Creating a basemap using psbasemap!........................................................104 Plotting Vector Data" 105 Plotting Symbols: -S[symbol][size] option!..................................................105 Plotting Vector Data: psxy command!...........................................................106 Colouring Interiors : -G[fill] option!...............................................................108 Colouring Outlines and Lines: -W[pen] option!...........................................110 Plotting Polygons: -L option!.........................................................................112 Plotting Coastlines: pscoast command!.......................................................113 Creating Colour Tables" 115 Defining colours for gridded data: -C option!..............................................115 Creating a colour table using makecpt!........................................................116 Creating a colour table using grd2cpt!.........................................................118 GMT Honours Course - University of Sydney" 4 Plotting Raster Data" 118 Querying raster data using grdinfo!..............................................................119 Plotting contours using grdcontour!............................................................120 Plotting gridded data using grdimage!.........................................................121 Building a GMT Script" 123 Starting a Shell Script!...................................................................................124 Building a Shell Script!...................................................................................124 Make a Shell Script Executable!....................................................................124 Run a Shell Script!..........................................................................................124 Assigning Variables in a Shell Script!...........................................................125 PostScript" 125 Building a PostScript file in GMT: -K and -O options!.................................126 Using Multiple GMT Commands!...................................................................127 7. Data Processing and Interpolation" 129 Modifying Vector Data" 129 Using common UNIX commands!.................................................................129 Using basic awk programming!.....................................................................129 How to use AWK" 129 Processing Vector Data" 134 filter1d!.............................................................................................................134 filter2d!.............................................................................................................134 trend1d!............................................................................................................134 Modifying Raster Data" 134 Querying raster data: grdinfo!.......................................................................135 Resizing or merging gridding data: grdcut, grdpaste and grdblend!........135 Resampling gridded data: grdsample!.........................................................135 GMT Honours Course - University of Sydney" 5 Performing mathematical operations on gridded data: grdmath!..............135 Processing Raster Data" 135 grdfilter!...........................................................................................................135 Data Interpolation" 135 Data Gridding!.................................................................................................135 xyz2grd!...........................................................................................................136 surface!............................................................................................................136 nearneighbor!..................................................................................................136 8. Further Reading" 136 9. References"