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Map Services: University Libraries


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Facts and Guides



Scale

Scale is an important consideration when deciding what sort of map will suit your purposes.The United States has been topographically mapped on several scales. These scales offer you one basic choice: will you sacrifice detail for area, or area for detail? Obviously, the larger the area covered on a map, the less detail can be dedicated to it. By the same token, the less area covered, the more detail you can find for it. The most detailed map series of the entire U.S. is the USGS 7.5 minute topographic map series. This series shows large amounts of detail over a small area.

Scale can be represented in three ways: Verbal scale, Bar Scale, and Representative Fraction (RF)

Example:

Verbal =                One Inch Equals One Mile

Representative Fraction =                1:24,000

Bar Scale =                0-----|-----1-----|-----2-----|-----3

Remember:
  • Large scale means Small area covered by the map. (Large amounts of detail)
  • Small scale means Large area covered by the map. (Small amounts of detail)
  • The size of the sheet has nothing to do with determining scale.

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Projections: Choose Your View Of The World

Projection refers to the mathematical method by which the three-dimensional Earth's surface is being portrayed onto a two-dimensional medium. There are many variations, but there are three types of projection methods on which all others are based. They are: Conical, Cylindrical, and Azimuthal. Each method distorts the globe in different fashion, but, as with any attempt to flatten around surface, they do distort. Conical projections offer less distortion in the Mid-Latitudes while a cylindrical projection distorts less around the Great Circle lines. Azimuthal, being based on a flat plain, distorts more and more as you move from the center. Each can be altered or positioned on the globe so as to offer the least amount of distortion for any particular area. Map Services has more information on projection types and their modifications.

For more information on the web, see Peters Projection vs. Mercator Projection.

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Locating a Geologic Map

Geologic maps are located throughout the collections - as monographs, in atlases, and in digital form - however there are a few specific series that offer detailed coverage of much of the U.S.:


  • Tennessee Division of Geology Quadrangles: extensive coverage of Tennessee at 1:24,000 scale.
  • Various U.S. Geological Survey series:
  • Geologic quadrangle maps (GQ-series): bedrock, surficial, or engineering geology of selected 7.5 or 15-minute quadrangles.
  • Oil and gas investigations maps and charts (OMand OC-series): subsurface structure and stratigraphy and surface geology of selected oil and gas fields.
  • Miscellaneous geologic investigations series maps(I-series): diverse topics, including bedrock and surficial geology, marine geology, mineral and energy resources, and geophysics and geochemistry. The series also includes maps of the Earth's moon and other planetary bodies, hydrogeology, landforms, earthquake epicenters, map projections, and oblique-view maps.
  • Miscellaneous field studies series maps (MF-series): either preliminary results of ongoing studies or final results that lack the scope of the I and GQ-series.
  • Coal investigations series maps (C-series): bedrock geology, stratigraphy, and structural relations of selected coal resource areas.
  • Hydrologic investigations atlases (HA-series): include maps which show a wide range of water resources information, including depth to groundwater and producing aquifers.
  • Other geologic maps may be found in USGS professional papers, bulletins, and water-supply papers, all located in Hodges Library. There are also certain I-series maps and other geologic data on CD-ROM, particularly in USGS' Digital Data Series.

USGS publications may be searched more thoroughly by consulting the "Guide to USGS Publications", located in the Map Services reference section, or the USGS National Geologic Map Database online. Map Services also makes available indexes for locating specific geographic areas of coverage.

For monographs, including state and regional geologic maps, digital resources, and geologic coverage of other parts of the world, search the UT Libraries' catalog or consult Map Services staff.

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