GMT - The Generic Mapping Tools

GMT is a set of public-domain computer programs widely used for analysis, processing, and display of scientific data. GMT is used by scientists in a variety of disciplines and on all continents. Being "generic", the programs are not tied to any particular data set or field, but can be (and is) used by geoscientists as well as medical researchers, engineers, social scientists, biologists, government agencies, and others. GMT has been installed on computers ranging from laptops to supercomputers, all running some flavor of UNIX. The latest version 3.0 was announced this fall in EOS (Wessel, P., and W. H. F. Smith, 1995, New Version of the Generic Mapping Tools Released)

This course will discuss the GMT environment and the use of GMT in processing, analysis, and display of scientific data. We will review many frequently asked questions about GMT, portability and installation issues, file formats, and learn to unleash the power of UNIX-GMT scripting. Specifically, we will discuss

• UNIX general processing tools such as awk, grep, and sed.
• The main aspects of cshell programming.
• Several GMT processing algorithms (such as gridding, contouring, triangulation)
• How the user's processing choices affect the final product.
• Basic properties of the most common map projections.
• Efficient GMT script writing.
• GMT PostScript and manual plot editing.

• Location maps with superposed symbols, lines, and text [BASIC].
• A variety of data analysis and processing scripts [INTERMEDIATE].
• Automatic custom database, mailinglist, and WWW page management [ADVANCED].

This course/seminar is open to all students. Interested staff and faculty are welcome to sit in on some or all sessions. There are no prerequisites or exams; grades will be assigned based on participation and three homework assignments tailored to each student's thesis project (if applicable). The form of the seminar will depend on enrollment and computer availability, as well as specific requests from potential participants.

Required text: The Generic Mapping Tools Version 3 Technical Reference and Cookbook by P. Wessel and W. H. F. Smith (Place order with Janet), X64774

Online access to course material

Most lectures will involve Unix or GMT scrips and data files. All keyboard commands issued during a demonstration will be saved in a lecture log (e.g., lec_4.log); there may also be PostScript files of handouts and other material. You can access all that stuff below; it will be added as the semester progresses.

Organization

• Course Flyer
• Course Outline

Session # 1 (Jan, 16, 1997)

• Lecture 1 notes
• What can GMT do?
• The GMT Run-time Environment
• Example of a .cpt file
• Example of an ascii file

Session # 2 (Jan, 21 & 23, 1997)

• GMT plot modules
• GMT Common Command Line Switches
• GMT Defaults for plots, 1[PostScript]
• GMT Defaults for plots, 2[PostScript]

Session # 3 (Jan, 28 & 30, 1997)

• GMT Cylindrical Projections [PostScript]
• GMT Conic Projections [PostScript]
• GMT Azimuthal Projections [PostScript]

Session # 4 (Feb, 4 & 6, 1997)

• Silly pattern
• data
• quakes.d
• quakes.cpt

Session # 5 (Feb, 11 & 13, 1997)

• Table 5.11 from Davis (1986)
• Color cpt file for that table
• Network file

Session # 6 (Feb, 18 & 20, 1997)

• Various color wheels

Session # 7 (Feb, 25 & 27, 1997)

No files, but we discussed the scope of Project 1. This project consists of making a cshell script called mapmaker that will assist the novice GMT user in making a simple Mercator map with colored continents. When run, the script should explain to the user what it does and request the following information:

1. Area of interest
2. Map width
3. Anotation interval
4. page orientation (landscape or portrait)
5. Color of the continents
6. Resolution of the coastline
7. Name of output file

The script should also contain comments identifying the purpose of the program, its author, date, version, and assumptions of the environment. Optionally, you may add a few more features to the script:

1. Default values for all questions
2. Option to draw the coastline and request a pen thickness and color
3. Option to draw political borders and request a pen thickness and color
4. Anything else that seems reasonably useful

Session # 8 (Mar, 4 & 6, 1997)

• filetype test
• break and continue test
• status test
• topo.d
• Te-age.table

Session # 9 (Mar, 11 & 13, 1997)

Session # 10 (Mar, 18 & 20, 1997)

• Triangulation exercise
• Nearest neighbor exercise

1. Can read 1 or more xyz ASCII tables of geographic or Cartesian data
2. Automatically adjust the grid aspect ratio for geographic data (use awk)
3. Provide reasonable default values for -R and -I (use awk)
4. Offer choice of spatial preprocessing (mean or medians)
5. Ask for output filename
6. Deal with data records (# in 1st col) and multiple segment records (> in 1st col) (use egrep)
7. Be clever about picking -R -I to ensure rapid calculation (hint: use surface -Q)

The script should also contain comments identifying the purpose of the program, its author, date, version, and assumptions of the environment.

Session # 11 (April, 1 & 3, 1997)

• the raw ship data
• crude clip polygon

Session # 12 (April, 8 & 1, 1997)

• cpt file for our data
• Awk script that generates awk-script for symbols
• example def file
• hot spot locations

Session # 13 (April, 15 & 17, 1997)

• Example of parameter file
• Final imagemaker script
• Example of mailed in message
• Nasty background deamon script

Session # 14 (April, 22 & 24, 1997)

~pwessel/bin/animate ~wessel/gg710-02/images/cglobe_??0.tiff

We also defined the third and final project which is about animation. The project is due May 16. The project should be a script that does the following:

1. Read or make one or several gridfiles for animation
2. Loop over these files or loop over view angle or any other proxy for change
3. For each step, make a PostScript file and convert it to a tiff file
4. clean up and start up animate

Session # 15 (April, 29 & May 1, 1997)