Here are some cases where one or more of the data sets will not be displayed.

* The most common mistake users make is to choose an image type data set,
such as topography, and keep the land and ocean features in the data sets to be
plotted list. Eventhough the topography map is displayed, land and ocean polygons
entirely cover the topography map, thus making it invisible. Make sure that at least
either ocean or land polygons are not selected in the data sets to be plotted list.

* Some data sets such as roads, isc seismicity, etc. are quite large. If you try to make a
global road map, for example, not only would the output be useless, it would also
keep the server busy long time. To prevent this, some data sets can only be displayed
when you have zoomed in on a region. These data sets are identified by a star next to
them in the data sets lists.

* All image type data sets will not be displayed if you zoomed in too much on a small region.
This is mainly due to a known bug in the system. However, the resoltion of the images
would not allow seeing extreme details, and for this reason, presently we are not worring
about this problem.

* If you are not doing any of the above actions, we would like to hear from you. Please let
us know by e-mail. Our address is in the home page.