Including Original "Paul H. Letters" Copyright © 1996-2018 Paul V. Heinrich - All rights reserved.

Thursday, 4 October 2007

Online Geological /Geophysical /Topological Map Resources

Online Geological /Geophysical /Topological Map Resources

Paul bristolia at
Thu Oct 4 09:35:31 EDT 2007

Mr EMan wrote:

"Having received some request for more online map
information, here are some tips for locating free on
line maps.(Primarily USA)."

There are some web pages, which provide links for where
free GIS data, including scans of topographic and other
maps, called "DRGs" for various states. They include:

1. "Maps and GIS Resources: United States, by State",
compiled by the University of Oregon Libraries.

2. Libre Map Project - The purpose of the Libre Map
Project is to aggregate and make digital maps and
related GIS data available for Free. The URLs are: and

3. Websites for Digital GIS Data - Stanford University

URLs for International GIS Data:

4. FINDING UNITED STATES DEMs - “Digital Elevation
Models for the United States can be downloaded at
no cost from several locations on the Internet.”

5. Guide to Mostly On-Line and Mostly Free U.S. Geospatial
and Attribute Data - University of Arkansas Compilation.

One way of finding digital map data is to search using your
favorite search engine and a combination of the key words
"GIS", "DRG", and the name of the state, for which a person
is looking for data. Most states now have GIS archives,
which contain DRGs of topographic maps and other digital

In terms of geologic maps, a person can go to the
National Geologic Map Database at:

It contains DRGs and other digital copies of various
geologic maps for parts of the United States.

Digital geologic maps accompany the United States
Geological Survey (USGS) publications, which can be
downloaded free from the USGS Publications Warehouse at;


For example, a geological map of a geologic dome, which
was initially mistaken for an impact crater, can be found in
“The geology and mechanics of formation of the Fort Rock
Dome, Yavapai County, Arizona, Professional Paper
no. 1266, at:


Paul H.

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