CHALLENGES TO THE UTILITY AND LONG-TERM ACCESSIBILITY OF DIGITAL GEOLOGIC MAPS

The essential nature of scientific content and cartographic layout of geologic maps and accompanying reports has remained relatively consistent through time. As a result, geologic maps of today bear strong resemblance to those of the 1800s, thereby enabling new studies to draw upon maps and information of many vintages. Those who can read a modern geologic map are likely to understand a map published in the early days of the science because of the consistent portrayal of geologic features. Mappers have, essentially, been following a standard method since the inception of geologic mapping. The science has evolved, but fortunately the design of the geologic map has remained relatively stable.

The transition from paper to digital methods for map compilation and for cartographic production has been underway for about five decades. This transition created new opportunities for more innovative science and more effective communication, but also carries the potential to degrade scientific productivity through decreases in standard information content and format. A perusal of maps published in GIS format during recent decades (e.g., searching the National Geologic Map Database, http://ngmdb.usgs.gov) illustrates this issue, and argues for increased standardization in order to ensure that the digital maps we produce today will be useable decades from now.

The development of standards for geologic map databases is a lengthy and difficult process, and some convergence of ideas and methods is occurring. Under the mandate of the Geologic Mapping Act of 1992, the National Geologic Map Database (NGMDB) project serves to coordinate and to highlight emerging initiatives, methods, guidelines, and standards in order to assist in delivering digital geologic maps that can be easily used by a broad audience of scientists, decisionmakers, and the general public.