DCW-GMT is developed and maintained by
Paul Wessel, SOEST, University of Hawai'i, Honolulu, HI, USA.
Federico Esteban, Consejo Nacional de Investigaciones Científicas y Técnicas: Buenos Aires, Argentina.
Eduardo Suarez, Facultad de Ciencias Astronomicas y Geofisicas - UNLP, Argentina (deceased).
The Digital Chart of the World (DCW) is a comprehensive 1:1,000,000 scale vector basemap of the world. The charts were designed to meet the needs of pilots and air crews in medium-and low-altitude en route navigation and to support military operational planning, intelligence briefings, and other needs. For basic background information about DCW, see the Wikipedia entry.
DCW-GMT is an enhancement to DCW in a few ways: (1) it contains more state
boundaries (the largest 8 countries are now represented), and (2) the data have
been reformatted to save space and are distributed as a single deflated netCDF-4 file.
The raw files used to build dcw-gmt.nc came from the Princeton University
Digital Map and Geospatial Information Center, accessible via website
http://www.princeton.edu/~geolib/gis/dcw.html; however, the DCW access
seems to have disappeared. Your best bet for more information is
DCW-GMT is released under the
GNU Lesser General Public License.