iGMT: Interactive Mapping of Geoscienti c Datasets. User manual for
Contents
1. Gravity anomalies from Sandwell and Smith 1997 The last example example4 of Fig 4 shows gravity anomalies in the Indian ocean ATTENTION This example is quite resource hungry and might lead to problems on smaller machines if actually run with the original data set 8 Conclusion The iGMT software package was programmed in a modular way Every routine is commented so it should be fairly easy to modify the code and add extensions to the software If you do 12 Figure 2 A part of the Carlsberg ridge in the Indian Ocean as of example2 ps parameters can be loaded from example2 dat The original file has extremely high resolution and was quite big The reduced image shown here was shrunk to 8ldpi using xv Bathymetry data is from Smith and Sandwell 1997 plate boundary from DeMets et al 1990 scale is the same than in Fig 1 so that s fine but please do not call it iGMT when you distribute it and make reference to the original software Please keep in mind that while GMT offers a large number of interesting and useful mapping options and iGMT tries to make use of them iGMT can t be as flexible as GMT In addition it is pretty hard to test every single combination of what might go wrong if Hence iGMT can be expected to fail to produce useful maps under certain circumstances Of course the software is provided as is no guarantee whatsoever is given and no responsibility for possible damage is taken Hopefully iGMT2. have compiled a list of significant earthquakes starting 2000 B C their catalog is accesible at http www ngdc noaa gov seg hazard sigintro html After quoting all lines without data by inserting a hash sign the format produced by this engine can be read directly into iGMT Internally all that iGMT does is to use awk to check if lines are quoted and for exporting of the relevant columns iGMT plots only earthquakes that have a magnitude assigned you might want to change the relevant awk lines in igmt_plotting tcl PDE earthquakes The United States Geological Survey keeps different hypocenter catalogs at the National Earthquake Information Center http wwwneic cr usgs gov neis epic epic_global html The Screen File Format can be read by iGMT Slab contours Gudmundsson and Sambridge 1998 define contours of the upper edge of sub ducting slabs from the relocated hypocenters of Engdahl et al 1998 These seismicity contours are available from http rses anu edu au seismology projects RUM rum_ download html we have included them in a format readable by GMT Custom xys files iGMT can plot two custom ASCII data files specified by the user They have to be in a columnar format similar to the polygon data described above and need at least longitude latitude and some size value for every line hence xys If you have z and y coordinates only modify the plotting routine or create an xys file yourself with the
3. help of an awk one liner awk if 1 print 1 2 1 oldxy dat gt new_xys dat You can now plot your data from the new_xys dat file and use the multiplying factor as the standard size of the symbols see also sec 6 2 Technical details how these files are handled are explained later in the text and in the comments found in igmt_plotting tcl 6 Usage of iGMT In the following I assume that you have a running version of iGMT The usage will be explained by going through all menu points that show up at the start up screen The basic idea of iGMT is to use GUI facilities to select important plotting parameters produce a GMT script and run it from within the program When this is done successfully the produced postscript code is converted to a GIF image and then displayed By doing this it is easy to create a basic script that can then be modified for more complex applications when the limits of iGMT are reached The menu list is divided into five pull down menues File Plot Datasets Parameters Scripting Options and GMT man pages as well as two buttons Map it and Quit 6 1 Menu File Plot This menue takes care of the main file handling and general input output functions of iGMT The first item Create PS leads to the identical action as the Mapit button that is e a GMT script is created and executed e if a postscript file was created this is converted into a GIF e the GIF map display underneath the menu bar is upda
4. If not write to the Free Software Foundation Inc 59 Temple Place Suite 330 Boston MA 02111 1307 USA He HR HHH HR HH HR HK HH HH H HK HEEHHHEHHHEHEERHHEERHREEHAREHRRREEEEHRHEHHEEHREEHPRRHRE EAE EHAEH EER H RRR REE 2 Credits and history iGMT is based on the GMT software by Wessel and Smith 1991 1995 and the Tcl Tk toolkit by John Ousterhout Small parts of the routines and templates were taken directly from the Tcl Tk book by Ousterhout 1993 or the GMT documentation Some of the initial Tk frame packing was done with the XF software by Sven Delmas iGMT makes use of the convert tool of the ImageMagick distribution The researchers making the data sets available that iGMT works with have to be mentioned for their great contribution Besides other sources datasets of NOAA 1988 Smith and Sandwell 1997 Sandwell and Smith 1997 Miiller et al 1997 DeMets et al 1990 Dunbar et al 1997 DeMets et al 1990 Steinberger 1998 Simkin and Siebert 1994 Dziewonski and Woodhouse 1983 and Rapp et al 1991 are processed by iGMT iGMT was formerly known as A GIS which stands for A Geophysical Information System Since the program has not full GIS functionality we changed the name to avoid confusion 3 Software requirements The current version of iGMT is intended for use on various UNIX systems and was developed running IRIX 6 3 However it could be modified to cross compile on other hardware platforms withou
5. demonstrates what can be done nowadays that great geophysical data sets and mapping software is available If iGMT helps in making the research work of earth scientists easier the mission is accomplished 13 et 329 23A0 M A 10 9 33 1 47 9 67 7 1204 131 9 147 7 180 0 Figure 3 Sea floor age of Miiller et al 1997 and plates from DeMets et al 1990 mGal 60 55 50 45 40 35 30 25 20 15 10 5 0 5 1015 20 25 30 35 40 45 50 55 60 Figure 4 Free air gravity anomalies in a part of the Indian ocean from Sandwell and Smith 1997 Dominant features are the Carlsberg Southwest Indian and Southeast Indian ridges the Bengal fan and the Ninety east ridge Resolution was restricted to 10 instead of 2 arc minutes 14 References DeMets C Gordon R G Argus D F and Stein S 1990 Current plate motions Geophys J Int 101 425 478 Dunbar P K Lockridge P A and Whitewide L S 1997 Catalog of Significant Earthquakes 2150 B C 1991 A D Report SE 49 National Geophysical Data Center Boulder Colorado http www ngdc noaa gov seg hazard sigintro html Dziewonski A and Woodhouse J 1983 Studies of the seismic source using normal mode the ory In Kanamori H and Boschi E editors Earthquakes observation theory and interpreta tion notes from the International School of Physics Enrico Fermi 1982 Varenna Italy pages 45 137 North Holland Publ Co Amsterdam http www s
6. 1998 and hotspots dat the hotspot list of Steinberger 1998 Colormaps The colormaps directory contains the colormaps that are used by iGMT to map the default datasets col 00 cpt through col 35 cpt are colormaps which span the data range from 1 1 B Modifying iGMT iGMT may be freely modified and distributed as long as modified version are not called iGMT There are plenty of easy possible future enhancements one could think of for instance interactive design of colormaps support of more complicated user data sets and multiple layers of raster data When this extensions become available they will be included in future versions Some common modification as opposed to extension or enhancement tasks are described below Using other path names for the locally available data sets This is easily done when its still the same format than the supported raster and polygon data sets just change the pathnames in igmt_configure tcl or in your igmt_siteconfig tcl file Including new raster data sets Make sure that the data is in one of the formats that can be read by grdraster img2latlongrd or grdimage itself Then include a new global path variable and raster data settings in igmt_configure tcl igmt_siteconfig tcl as was done for instance for the gravity data Next include a new point in the menu in the igmt_menus tcl file after the old ones that lets you choose your new data file instead of the old ones Last add some new plotting commands
7. 4 We have heard from successful installations on the SUN Solaris IBM AIX SGI IRIX and LINUX operating systems so far waw soest hawaii edu wessel gmt html GMT itself has some additional software requirements such as the availability of the netcdf library see the GMT documentation GMT could be compiled on other platforms but I am not aware of any working port at the moment awk The awk command language is available on all UNIX systems such as AIX IRIX SO LARIS HPUX or LINUX AWK or some GNU flavors of it should run on a PCs and Macs showps iGMT defaults to using the Adobe showps postscript display program You can change this like many other things in the configuration file igmt_configure tcl that comes with the iGMT distribution Another option to change parameters is to create a igmt_ siteconfig tcl file and redefine site specific variables here This file gets sourced after iGMT reads igmt_configure tcl hence variables will be overwritten by the user settings By creating a site specific file it is easier to upgrade to future versions of iGMT A possible postscript viewer alternative would be ghostscript or ghostview available for PC and Mac iGMT works fine without any postscript displayer at all as long as you do not need to view the PS files before printing them convert The convert tool of the ImageMagick software http www wizards dupont com cristy ImageMagick htm1 is used by default to convert from PS to t
8. Geoscience Press Tucson Arizona 2nd edition http www volcano si edu gvp volcdata index htm 15 Smith W H F and Sandwell D T 1997 Global seafloor topography from satellite altimetry and ship depth soundings Science 277 195 196 http topex ucsd edu marine_topo mar_topo html Steinberger B 1998 Plumes in a convecting mantle Models and observations for individual hotspots J Geophys Res submitted USGS NEIC 1998 National Earthquake Information Center World Data Center A for Seis mology Global Earthquake Search United States Geological Survey National Earthquake Information Center http wwwneic cr usgs gov neis epic epic_global html Wessel P and Smith W H F 1991 Free software helps map and display data EOS Trans AGU 72 445 446 Wessel P and Smith W H F 1995 New version of the Generic Mapping Tools released EOS Trans AGU 76 329 A Technical details A 1 Organization of the iGMT software After unpacking the igmt_v0 5 tar file the directory should look something like this gt ls F allslabs_rum gmt 01_02 98 cmt igmt_configure tcl COPYING igmt_datasets tcl COPYRIGHT igmt_def gif README TXT igmt_gmtdefaults colormaps igmt_helper_checkfile examplel dat igmt_helper_create_man_page examplel ps gz igmt_helper_handle_gmtdefaults example2 dat igmt_helper_rmtmp_silent example2 ps gz igmt_init tcl example3 dat igmt_iomisc tcl example3 ps gz igmt_menus tcl example4 d
9. at igmt_parameters tcl example4 ps gz igmt_plotting tcl hotspots dat manual ps igmt nuvel yx igmt tcl volcanoes dat where the colormaps directory contains the color tables for GMT gt 1s col 00 cpt col 11 cpt col 22 cpt col 33 cpt col 01 cpt col 12 cpt col 23 cpt col 34 cpt 16 col 02 cpt col 13 cpt col 24 cpt col 35 cpt col 03 cpt col 14 cpt col 25 cpt col 36 cpt col 04 cpt col 15 cpt col 26 cpt col 37 cpt col 05 cpt col 16 cpt col 27 cpt geoid cpt col 06 cpt col 17 cpt col 28 cpt gravity cpt col 07 cpt col 18 cpt col 29 cpt seafloor_age cpt col 08 cpt col 19 cpt col 30 cpt seafloor_age2 cpt col 09 cpt col 20 cpt col 31 cpt topo cpt col 10 cpt col 21 cpt col 32 cpt The files in this distribution can be classified as follows Copyright COPYING and COPYRIGHT deal with legal issues iGMT is distributed under the GNU public license see the file COPYING The igmt file A ksh script that is used to check if the environment variable igmt_root and wish is available at the places iGMT is looking If all is fine wish is invoked with igmt tcl igmt_def gif is the start up screen Tcl files All files with the tcl extension contain the tcl code that runs iGMT igmt tcl is the main file it contains source commands and builds up some frames igmt_configure tcl has all global variables and the default settings for plotting whereas igmt_init tcl handles the startup sequence The file igmt_menu tcl holds the definition for the main me
10. e base data layer and provide your own colormap too 5 2 Polygon data Some example handling procedures for polygon data are included as well Plate boundary data The plate boundaries as given by DeMets et al 1990 are part of the iGMT distribution as the file nuvel yx in a slightly modified form Any polygon data file supported by psxy can be substituted for this data set Hotspot locations iGMT uses a list of hotspots compiled by Steinberger 1998 to plot their location and a name tag if selected Volcano locations The Smithsonian Institution Global Volcanism Program s list of volcanoes Simkin and Siebert 1994 is supported in the form found at http www volcano si edu gvp volcdata index htm As for the hotspot data the user can select a symbol the color and toggle a name tag A version of this list as of April 1998 is included If you want to install an update just download the data from the web and replace the adequate file The same holds true for the earthquake catalogs since iGMT was programmed to handle the original data CMT fault plane solutions iGMT uses psvelomeca from the GMT supplements package to plot the double couple part of the Harvard CMT centroid moment tensor solutions e g Dziewonski and Woodhouse 1983 as found at http www seismology harvard edu CMTsearch html A list of all events in the catalog of the first 60 days of 1998 is included as an example Significant earthquakes Dunbar et al 1997
11. ed to change the command line used for the conversion operating system call see the comments in the igmt_configure tcl file From now on we use the acronym GIF to refer to whatever graphic format you chose multi user systems since the package itself is relatively small Installing multiple copies would allow every user to modify the iGMT code themselve Next an environment variable igmt_root must be set to point to the directory where iGMT resides With csh this would be done by adding a line like setenv igmt_root HOME tcltk igmt_dir to the HOME login file The startup script file is igmt_root igmt This script calls the Tcl Tk shell wish using the path usr freeware bin wish If wish is somewhere else either change the corresponding line in igmt or set the environment variable wish_cmd After verifying the settings igmt should be executable and iGMT can be started by typing igmt_root igmt at the command line Of course this can be faciliated by adding an alias or linking igmt_root igmt to some place where your shell looks for executables 5 Datasets handled by iGMT While iGMT is lacking the database query functions of full blown GIS systems it is capable of combining multiple geophysical data sets and handling large amounts of data in an efficient way Indeed this is an achievement of the GMT software and iGMT usage does not constrain this feature Excellent data is available on the web these days and iGMT is based u
12. eismology harvard edu CMTsearch html EDC 1996 Global 30 Arc Second Elevation Data Set EROS Data Center Sioux Falls South Dakota Engdahl E R van der Hilst R and Buland R 1998 Global teleseismic earthquake relo cation with improved travel times and procedures for depth determination Pull Seism Soc Am 88 722 743 Gilly D 1994 UNIX in a Nutshell O Reilly amp Associates Inc Cambridge Gudmundsson O and Sambridge M 1998 A regionalized upper mantle RUM seismic model J Geophys Res 103 7121 7136 M ller D Roest W R Royer J Y Gahagan L M and Sclater J G 1997 Digital isochrons of the world s ocean floor J Geophys Res 102 3211 3214 http Omphacite es su oz au StaffProfiles dietmar Agegrid agegrid html NOAA 1988 Data Announcement 88 MGG 02 Digital relief of the Surface of the Earth National Geophysical Data Center Boulder Colorado http www ngdc noaa gov Ousterhout J K 1993 TCL and the TK Toolkit Addison Wesley Reading MA Rapp R H Wang Y M and Pavlis N 1991 The Ohio State 1991 geopotential and sea surface topography harmonic coefficient models Rep 410 Dept of Geod Sci and Surv Ohio State University Columbus Ohio Sandwell D T and Smith W H F 1997 Marine gravity anomaly from Geosat and ERS 1 satellite altimetry J Geophys Res 102 10039 10050 Simkin T and Siebert L 1994 Volcanoes of the World
13. furt am Main Germany Contents 1 Copyright and warranty disclaimer 2 Credits and history 3 Software requirements 4 Installation 5 Datasets handled by iGMT 5 1 Raster data 00 0 5 2 Polygon data 6 Usage of iGMT 6 1 Menu File Plot 6 2 Menu Datasets 6 3 Menu Parameters 6 4 Menu Scripting options 6 5 Menu GMT man pages 7 Examples 8 Conclusion References A Technical details A 1 Organization of the iGMT software B Modifying iGMT 12 16 16 16 18 1 Copyright and warranty disclaimer HEEHHHEHHHEHEERHHEERHREEHAREHRRREEEEHRHEHHEEHREEHPRRHRE EAE EHAEH EER H RRR REE iGMT Interactive Mapping of Geoscientific Datasets Easy access to GMT via a Tcl Tk GUI Copyright C 1998 Thorsten W Becker Alexander Braun This program is free software you can redistribute it and or modify it under the terms of the GNU General Public License as published by the Free Software Foundation either version 2 of the License or at your option any later version This program is distributed in the hope that it will be useful but WITHOUT ANY WARRANTY without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE See the GNU General Public License for more details You should have received a copy of the GNU General Public License along with this program see the file COPYING
14. he GIF format You might as well use ghostscript to convert from postscript or change the graphic format that is used for previewing to something completely different 3 iGMT works fine without a converting tool even though you get an error message when you use Map it since this command includes not only postscript but GIF output see below If you have installed the tools mentioned above you should be ready to use the basic version of iGMT While the requirements above might seem complicated it should be kept in mind that nowadays most UNIX or LINUX systems come with all of the above except GMT when the system software is installed GMT on the other hand is widely in use in the earth sciences already In addition all of the software needed to run iGMT is freeware or shareware of some kind and most of it is subjected to an open developing policy 4 Installation To get iGMT running extract the distribution igmt_v0O 5 tar gz if you have not already done so in a directory where you store Tcl Tk scripts This could well be at the single user level on 3 At the moment standard Tcl photo image displaying works only with GIF and ppm images Since ppms are usually much bigger than GIF images we chose GIF to be the standard If you choose ppm not interfering with possible copyright issues and continue to use convert just change the name of the converted file for convert in igmt_siteconfig tcl to have a ppm suffix For ghostscript you ne
15. iGMT Interactive Mapping of Geoscientific Datasets User manual for version 1 0 Thorsten W Becker Alexander Braun October 2 1998 Abstract iGMT is free software for intearctive mapping of geoscientific datasets that is built around the GMT mapping tools iGMT is intended to assist in the creation of GMT scripts for mapping raster or polygon datasets and has built in support for topography sea floor age free air gravity the geoid and various polygon data files such as earthquake hypocenter lists or hot spot locations The package should serve the earth scientist with limited experience with data set han dling in all sorts of geophysical or geological mapping tasks In addition it provides the experienced user with a graphical user interface for the GMT parameter choice After com pleting a session the user ends up with a igmt_commands gmt file that is an executable script and contains the commands used to create the last map It should serve as a starting point for more complex tasks that can t be achieved with iGMT This manual describes briefly how iGMT is used and explains some technical details that may be helpful if the user wishes to extent or modify the script iGMT is free software under the GNU license Harvard University Department of Earth and Planetary Sciences 20 Oxford St Cambridge MA 02138 USA TInstitut f r Meteorologie und Geophysik J W Goethe Universitat Frankfurt am Main Feldbergstr 47 D 60323 Frank
16. ile in the next three lines modify the respective custom polygon data files The polygon menu comes with the option of plotting two user defined data sets as mentioned above The following two items in the menu list bring up two identical dialogs where the names of the custom xys files the columns for latitude longitude and size as well as a magnification factors for the size can be specified Internally all data sets are of course handled by a trivial awk script that can be viewed in the GMT script file or in the source code that is igmt_plotting tcl 6 3 Menu Parameters This longest menu is used to set all the parameters for the GMT script It is this step in the map production process where were the graphical user interface can be hopefully most helpful Item Region This item brings up the region selection dialog Where the eastern northern etc boundaries are self explaining the Center of map projection is needed for whole earth viewing projections Clicking on The whole thing expands the geographical boundaries as far as possible for the checked projection Square it attempts to make a square like map by setting the difference between the boundaries equal Center focus in region sets the center of map projection values to the averages of the boundaries Item Projection The projection order chosen for the dialog box follows the GMT manual http www soest hawaii edu wessel gmt gmt_doc htm1 closely Projec
17. in igmt_plotting tcl With some familiarity with UNIX and GMT this should be easily done by cut and paste with the default data sets as examples Including new polygon data sets In principle this works the same way than for raster data with the exception that polygon data can be multi layer and you need to introduce another global variable in igmt_configure tcl How to do this should be evident when the custom xys files 1 and 2 are taken as an example Last resort Contact Thorsten Becker becker eps harvard edu or Alexander Braun braun em uni frankfurt de 18
18. l probably need some hands on modification of the GMT script 6 4 Menu Scripting options The first item Show GMT script shows the file that is created and executed by iGMT to get GMT to produce the postscript file we are viewing This is intended to do two things Show the inexperienced user what can be done in addition to the introduction in the GMT manual and give the experienced user a fast tool to get to a start script for more complicated applications This file is called HOME igmt_parameters dat by default Add stuff to the pscoast line lets the user add additional commands to the last pscoast command of the script file without having to exit from iGMT and run the script independently The file presented by Show script errors contains the stderr output of the GMT commands invoked and should be helpful for debugging By default GMT is verbose The next item lets the user switch the GMT logo on and off By default it is off since it would interfere with the colorbars 6 5 Menu GMT man pages This menu list is intended to provide fast access to the GMT man pages for reference At the time of the first call a temporary file is created from the man command and afterwards displayed every time the user selects the same command man page again Finally the two buttons on the right hand side of the menu bar do what they say 7 Examples The following examples were produced by running iGMT with the full data sets as described above The
19. nu line and the procedures found in igmt_datasets tcl igmt_parameters tcl and igmt_plotting tcl correspond roughly to all possible actions in the individual pull down menus Finally igmt_ iomisc tcl contains most of the input output routines and some additional tcl procedures All of these files should be fairly well commented so that I won t go into any detail here igmt_helper_ files These contain small ksh scripts that are called by iGMT tel routines and handle more operating system based processes Most of them could be integrated into the main tcl code but it seemed more transparent for possible porting to other operating systems to keep them external example dat and ps The dat files contain the parameter dump that was created with iGMT after the examples presented in sec 7 were produced The postscript files are packed with gzip and correspond to the shrinked figures in this manual and are not identical to the real postscript files produced they were too big to be included in the distribution Documentation and data The file manual ps is the manual you are reading as a postscript file nuvel yx is the modified plate boundary polygon file after DeMets et al 1990 01_02 98 cmt contains the Harvard CMT double couple fault plane solution for the first 60 days of 1998 as an example vocanoes dat the volcano locations after Simkin and Siebert 1994 allslabs_rum gmt 17 the slab seismicity contours of Gudmundsson and Sambridge
20. ormap you have to reenter the selection Use Shade raster data to toggle the shading that is done for topographic and gravity datasets using grdgradient Polygon data set items The next three menu items change what they say Symbols Sizes and Color of the polygon data Sizes are in fractions of the mapwidth and get multiplied by another factor with the size column of the xys data The symbols types that are implemented are again only a subset of what GMT can do Linewidth changing only works for the plate boundaries and the rivers and national boundaries of pscoast so far Name tags can be switched on and off for hot spots and volcano data sets Items for map grid line and frames Gridlines and Frame annotation are on off switches By default the gridlines are twice as densely spaced as the outer annotation intervals along the map frame Change this in igmt_plotting tcl if you like The mapscale the user can switch 10 on and off is positioned in the lower left corner of the map and calculated to be correct at center latitudes Miscellaneous plotting items Add a title to the plot and change the page size and orienta tion here The offsets in x and y direction default to one inch each which is usually ok Don t expect perfect results in terms of title placement or centering of the final map on the produced postscript file though Reasonable results should be achievable with the built in functions of iGMT while final copies wil
21. pon these publicly available collections Since GMT is growing into a de facto standard in parts of the geophysical community it seems natural to use GMT to handle the data With the requirements that are explained in sec 3 you should now be able to interactively use the GMT command pscoast that is used for plotting maps of land and sea coverage with political boundaries etc 4 If you want to take advantage of the built in handling capabilities for various datasets you need to get the data or tell iGMT where it can find it if the data is already around on your system All path names can be changed together with all other global variables in the igmt_configure tcl or a site specific igmt_siteconfig tcl file see above Furthermore the user has the option to specify one raster grd file and two custom polygon data sets The igmt_configure tcl is commented so it should be easy to find what you are looking for In addition some of the datasets require special converting software 5 1 Raster data Besides pscoast land and sea coverage and shorelines the following raster data files are sup ported ETOPO5 topography The ETOPO5 topography bathymetry NOAA 1988 available at http www ngdc noaa gov is supported in combination with the grdraster tool which is as psvelomeca part of the supplementary package that is available together with the GMT main distribution The ETOPO5 data set is about 19MB in i2 binary format Man pages and other doc
22. t much effort given that the software that iGMT relies on or an equivalent is available for the operating systems in question This is the case for Macs and PCs whereas I have no experience with the ported products in question The iGMT script package that comes with this documentation some example plots and small datasets is available at the iGMT home page http www seismology harvard edu becker igmt This is also the place to check for updates bug reports etc iGMT assumes that you have the following software installed and accessible either via the user s path variable or the binary paths set in igmt_configure tcl or the igmt_siteconfig tcl file see the comments below If this does not make sense to you please ask your local system administrator Tcl Tk The Tcl script language and the Tk toolkit for the construction of graphical user interfaces Ousterhout 1993 are currently available under http www scriptics com or http sunscript sun com Version 8 0 of Tcl Tk was used for developing older version may work as well Tcl is available for UNIX PC Mac and other platforms GMT The generic mapping tools Wessel and Smith 1991 1995 do the work iGMT wants version 3 0 The source code distribution as well as documentation is available at http 1Tt will be assumed that the user has some familiarity with the UNIX operating system and basics will not be explained here for UNIX and shell scripting reference see e g Gilly 199
23. ted The next three items allow the user to create a postscript file only or individually display the postscript This might be helpful if you have trouble installing a PS to GIF converter The filenames used for this process default to tmp igmt_ USER_tmp ps and tmp igmt_ USER_tmp gif again this can be changed in igmt_configure tcl or igmt_siteconfig tcl USER is replaced by the UNIX user name to avoid conflicts with write permissions if more than one user operates iGMT on a single machine If the produced map files are to be kept the user can either copy them to another place by hand or use the following two items in the menu list Save PS file and Save GIF file Load and Save parameters use a file to dump almost all iGMT parameter settings so that a session can be restarted at a later time without having to redo all the fine tuning iGMT comes with four example parameter files example dat that can be loaded to experiment with the software 6 2 Menu Datasets The first item in the Datasets menu leads to the raster data choice dialog where the files to choose from are those described in sec 5 The same holds true for the polygon datasets of the second item In contrast to the raster data sets polygon sets can be plotted on top of each other Future versions of iGMT will allow multiple layers of raster data as well The next part of the Datasets menu lets the user choose the custom GMT grd file he wants to plot whereas Change f
24. tions themselves are explained briefly in the pscoast man page The last check box custom projection allows the user to specify the projection with the magnification factor in the GMT format explicitly This might be needed since formatting is not perfectly done by iGMT and not all GMT projec tions are implemented Some of the projections adjust the geographic region to be plotted as suitable Items for pscoast The next three items deal with pscoast A small subset of the polygon data that can be plotted by this routine are mentioned in the Pscoast polygon selection list The next item allows changing the color of the land and sea coverage while the last pscoast item is responsible for changing some linewidths Raster data set items Toggle the automatically provided legends for the gravity age geoid and topography data sets on and off and select the subset grid resolution If the value you choose in arc minutes is smaller than the minimum value supported by the specific data set iGMT increases the value again There will be a warning when a larger number of data points are about to be processed Keep in mind that small machines might have a hard time if the resolution is too high and or the map size is too big Change colormap lets the user choose a colormap other than the ones used automatically when a predefined raster data file is selected If you change the raster data set to one of the predefined ones after choosing your own col
25. umentation are available for the GMT commands Therefore the usage will not be explained in this manual Refer e g to the man page function provided by iGMT or to http www soest hawaii edu wessel gmt gmt_doc html GTOPO30 topography The GTOPO30 DEM model EDC 1996 was greatly expanded by Smith and Sandwell 1997 It is supported in the form suggested by Smith amp Sandwell using img2latlongrd Data and other tools can be found at http topex ucsd edu marine_topo mar_topo html The img format file is 137MB Sea floor age The sea floor age data of Miiller et al 1997 was published as a GMT grdfile and is used in the form as available at http Omphacite es su oz au StaffProfiles dietmar Agegrid agegrid html The data is about 23MB in grd format and roughly 10MB in i2 binary which could be read by grdraster as ETOPO5 to do this change the corresponding lines in igmt_plotting tcl Free air gravity Sea floor gravity anomalies as published by Sandwell and Smith 1997 are used as a grdfile as found at http topex ucsd edu marine_grav mar_grav html As GTOPO30 this file is 137MB big Geoid iGMT supports plotting the geoid and comes with an adequate colormap As an ex ample we evalutated the spherical harmonic coefficients of Rapp et al 1991 from order 2 to 360 and included them in 20 arc minute resolution as a GMT grd file in our raster data set Custom data You can choose an arbitrary GMT grd file to be plotted as th
26. y can be reproduced if the data is available locally by loading the parameters file given in the distribution Hypocenters from the NEIC dataset Figure 1 shows the map of example1 ps from the iGMT distribution the whole Earth in the Mollweide projection ETOPO5 in 60 arc minute resolution is the ground raster layer All hypocenters of the USGS NEIC dataset from 1973 1997 with magnitude greater than five and NUVEL1 plate boundaries are superimposed Load examplei dat to produce this plot To reduce the size of this documentation the postscript file is not exactly that produced by iGMT but a converted GIF with lower resolution 11 m a s l 6000 3000 1000 0 500 1000 5000 Figure 1 ETOPO5 NUVELI1 plate boundaries and PDE hypocenter distribution as of example1 ps resolution reduced Data from DeMets et al 1990 NOAA 1988 USGS NEIC 1998 Smith amp Sandwell GTOPO30 topography Figure 2 of example number two shows a part of the Indian ocean and the Indian subcontinent It was produced using the Smith amp Sandwell GTOPO30 dataset in full resolution and has the pscoast shoreline data in high reso lution superimposed The original map has fascinating detail that might be lost in this repro duction Sea floor age of Miiller et al Example 3 as resp resented by Fig 3 and the files example3 ps and example3 dat shows the North Atlantic region sea floor age data coverage together with plate boundaries Stereographic projection
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