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TOPOGRAPHIC MAPS by hedongchenchen


									                                 Documents, Maps and Microforms Guide, CWU Library

                                          TOPOGRAPHIC MAPS

TOPOGRAPHIC MAPS portray, in detail, the physical features (natural and human-made) of a geographical
area. By using contour lines, topo maps are able to show the shape and the changes in elevation of terrain on
a map sheet.

MAP SCALES are used to show different degrees of detail:
 Large-scale maps provide detailed information for a small area. (1:24,000 for example)
  Small-scale maps provide limited information for a large area. (1:500,000 for example)
    The larger the number, the lesser the detail is one way of remembering this principle.
7.5-MINUTE SERIES, also referred to as the 1:24,000 scale quadrangles (quads), are the most heavily used
topographic maps. These are the largest-scale (the most detailed) maps produced by the USGS.

    Most USGS maps divide the U.S. into areas bounded by two lines of latitude and two lines of longitude,
    producing a rectangular area, called a "quadrangle". 7.5-minute series maps show an area that spans
    7.5 minutes of latitude and 7.5 minutes of longitude.

CWU Library receives 7.5 topographic maps for all 50 states (over 55,000) sheets
                  Each quadrangle is named after the most prominent feature within its area.
                  The 7.5 (1:24,000) topo maps are filed by state and then alphabetically by the name of the map.
                  Indexes to the topographic maps are kept in the drawers at the beginning of each State.
                  Records for each state and the sheet names of 7.5 quadrangle maps are being entered in CATTRAX.
                  With the exception of Washington state, the 7.5 maps circulate
 Other common map scale series are:
     Intermediate scale maps: 1:50,000 and 1:100,000
     Small scale maps: 1:250,000, 1:500,000 (state), and 1:1,000,000 and larger (U.S. - G 3700's)
                                         READING A TOPOGRAPHIC MAP

     Contour lines are used to show the shape and elevation of the terrain.
     - Contour lines never cross one another.
     - Where contour lines are close together, the slope of the hill is steep.
     - Where contour lines are far apart, the slope is gentle.
     - Lines that close within the map area represent hills.
     Contour intervals (space between contour lines) are chosen based on map scale and local relief.
     - Small intervals are used for flat areas.
     - Large intervals are used for mountainous terrain.
     Elevations are indicated -usually in feet, but occasionally in meters.

                                               COMMON MAP SCALES
             Inch System                                                             Metric System
      Scale:              1 inch represents:                                   Scale:          1 cm represents:
     1:2,500,000           40 miles (approx.)                                1:100,000             1.00 km
     1:1,000,000           16 miles (approx.)                                1:50,000              0.50 km:
     1:500,000              8 miles (approx.)                                1:25,000              0.25 km
     1:250,000              4 miles (approx.)                                1:20,000              0.20 km
     1:125,000              2 miles (approx.)
     1:63,360               1 mile
     1:24,000                 2,000 feet
                                                                                                      8/02 jj-3T

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