Additional Information on OMC

• Performance
• Political Boundaries
• Bathymetry and Topography
• Editing the Maps
• Known Bugs
• Plans
• Versions
• The Script
• References
• Net Awards

Performance

Performance of OMC depends on internal processing time and the bandwidth/traffic ratio in a given situation. Internal processing (map generation, postscript conversion) takes 15 to 30 seconds on a SparcStation 10. Plotting magnetic lineations and fracture zones may cost 20 seconds each. There might still be some chances for optimizing the cgi-script, but I guess they would be hard to notice.

The time for transmission of the map to your browser cannot be generalized. The server log tells us, load is smallest around 7.00 MET

Political Boundaries

The political boundaries plotted with the OMC are now quite up-to-date. The current GMT versions come with data on political borders which do reflect the post-cold-war situation. The amount of work put into this part of the GMT package by the authors must have been quite high and I hope they do not have to touch these files again in the future - not only form a GIS point of view.

Bathymetry and Topography

The OMC offers the plotting of contour lines for bathymetry (water depth) and topography (elevation of dry areas). The information used are derived from the ETOPO5 data set which is available from U.S. National Geophysical Data Center (NGDC). E. Söding of GEOMAR made a global GRD-file from ETOPO05 and allowed us to use this with OMC.

The contour interval at OMC depends on the map extent:
< 2 degrees: contour interval = 100m
> 2 degrees: contour interval = 200m
> 10 degrees: contour interval = 500m
> 90 degrees: contour interval = 1000m
Always the 'smaller' edge of the map is taken into account.

Here this data set is only used to illustrate the relief of the area mapped: the contours are not annotated. The deviation of the contours from the "real world" might reach tens to hundreds of meters. It is not intended to give serious morphological information (e.g. for scientific or navigational purposes).

Editing the Maps

To date, the user has no influence on the appearance of the maps, except the mapping areas though you might opt for b/w-maps form version 4.0 on. Moreover, the maps might not look very attractive (specifically if you plot locations). But the maps are presented to the user as PNG (indexed colors) images and one might download EPSF or Adobe Illustrator versions of a map. These types of files can easily be edited by the user, for instance by changing the indexed colors. The postscript and Illustrator files can be imported by a variety of graphic packages.

Known Bugs

Plotting maps with topography and/or bathymetry contours with a Lambert Azimuthal projection results in a map where only the area specified in the input form gets the contours.

Plans

Eventually, OMC will be developed to an interface to available georeferenced information (political, infrastructural, etc.) from the public domain.

Versions

Version 4.1, March, 1999:
Small updates and modifications of the OMC-pages.

Version 4.0, April 15, 1997:
"Pan and Zoom"-functions implemented (eventually). Thanks to "mapproject" another very useful GMT routine. Added option to create black-and-white maps. This was one of the features users kept asking for.

Version 3.0, May 24, 1996:
OMC moved to another machine, saves some 15 seconds for remote shell formerly necessary. Polar Stereographic projection added (useful for mapping polar regions). Scale gets plotted on the maps. New options: track-mode for user-defined locations, plotting of plate boundaries, plotting of magnetic lineations and fracture zones. Redesign of the input-form, update of the .html-documents

Version 2.2, May 3, 1996:
Postscript-to-GIF conversion now done by ImageMagick. Script straightened up. Option to plot some cities added.

Version 2.1, April 18, 1996:
Added option to plot contour lines illustrating topography and bathymetry. Minor changes of the .html-documents.

Version 2.0, April 16, 1996:
Added option to plot DSDP/ODP-sites, added option to plot user defined locations. Fixed some typos, introduced new typos.

Version 1.0, March 1996:
4 map projections available, download ps-maps after creation, simple test for non-valid input, limit Mercator maps to defined areas,

The Script

If you are in the mood for a journey to the stone-age of online mapping you might take a look at the main script that delivers the maps. You easily identify old-style code from the first 3 month a newly self-appointed perl-hacker.

References

Wessel, P., and W. H. F. Smith, 1995

The Generic Mapping Tools (GMT) version 3.0 Technical Reference & Cookbook, SOEST/NOAA.

Wessel, P., and W. H. F. Smith, 1995

New Version of the Generic Mapping Tools Released, EOS Trans. AGU, 76, p. 329.

Wessel, P., and W. H. F. Smith, 1995

New Version of the Generic Mapping Tools Released, http://www.agu.org/eos_elec/95154e.html, Copyright 1995 by the American Geophysical Union.

E.Tittel, M.Gaither, S.Hassinger & M.Erwin (1995):

Foundations of World Wide Web Programming with HTML and CGI. - IDG Books Worldwide Inc., Foster City CA, USA: 648 pp.

R.L.Schwarz (1995):

Einführung in Perl. - O'Reilly/Internationl Thomson Verlag, Bonn: 258 pp.

Net Awards:

	Winner of the Europe's Cool Site of the Day award! June 20, 1996