LI 861 XI and XJ Current Topics in Information Transfer:
GIS & Map Librarianship

Emporia State University
Emporia, Kansas USA

Topographic Maps

Susan Ward Aber

7.5-minute topographic map
of Fort Smith, Arkansas.
Image taken from: mac.usgs.gov/
isb/pubs/booklets/topo/topo.html

Sample

Topographic sheet maps are central to map collections. The purpose of this activity is to introduce this map type and define its makeup including contour lines, grid systems, and map scales that combine to help find elevations and locations on Earth.

Contour Lines

Topography is the configuration of Earth's surface, which is modeled with imaginary lines on Earth connecting points equal in elevation. These imaginary lines shown on topographic maps are called contour lines and elevation is shown in feet or meters above mean sea level. A contour interval is the difference in elevation between any two adjacent contour lines and while it is constant for a particular map, intervals may be 5 feet to 400 foot depending on the level of detail needed for a given region. In order to show detail but keep the map readable, higher contour intervals are used for mountainous regions and lower contour intervals for flat areas.

On standard USGS topographic maps, contour lines are brown when representing land and blue for water, with every fifth line printed bold. Spot elevations are given to the nearest foot or meter for points of interest such as a hilltop or coastline. Precise spot elevations accompanied by B.M. are benchmarks that are actually marked on the ground with a brass plate permanently fixed on the ground by surveyors.


Topographic Map image
taken from: en.wikipedia.org/
wiki/Image:Topographic_map
_example.png#file

Topographic Map image taken from:
en.wikipedia.org/wiki/Image:
Topographic-Relief-perspective-example.jpg

According to Johnston et al. (2006), five rules apply to interpreting contour lines:

  1. When contour lines cross streams, they bend or V upstream due to erosion and consequently stream flow is in the opposite direction.
  2. Closed contours shown as ellipses or circles represent hills.
  3. Closed contours shown with hachures or short lines radiating inside the O point downslope and represent a closed depression or basin with no outlet.
  4. Steep slopes are shown by closely spaced contours, and gentle slopes are shown by widely spaced contours.
  5. The difference in elevation between the highest and lowest point of a given area is known as the maximum relief.

This course was first offered for university credit in the spring 2007 semester. Visit Course Schedule and Syllabi to see when it will be taught again for ESU, slim.emporia.edu/program/syllabus/syllabus.htm. Or if you are interested in taking this course on the resources and services associated with map librarianship, please contact Dr. Aber at saber@emporia.edu.

This page was for the use and benefit of students enrolled at Emporia State University, School of Library and Information Management slim.emporia.edu/. For more information contact the course instructor, S. W. Aber, e-mail: saber@emporia.edu Thanks for visiting! Webpage created: December, 2006; last update: June 17, 2008.

Copyright 2007-2008 Susan Ward Aber. All rights reserved.