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Geosciences LibreTexts

3: Topographic Maps

  • Page ID
    5467
  • Learning Objectives

    After completing this chapter, you should be able to:

    • Recognize topographic patterns and geologic patterns
    • Read and construct contour lines
    • Determine gradients
    • Read map scales and convert fractional scales
    • Construct a topographic profile

    • 3.1: Introduction
      A topographic map is an extremely useful type of map that adds a third dimension (vertical) to an otherwise two-dimensional map defined by the north, south, east, and west compass directions. This third dimension on a topographic map is represented by contour lines, which are imaginary lines drawn on a map that represent an elevation above average sea level (a.s.l.) or mean sea level (m.s.l).
    • 3.2: Map Orientation and Scale
      All topographic maps produced by the U.S. Geological Survey (U.S.G.S) are oriented with north at the top of the map. Therefore if you locate a position on the map, and move towards the top of the map you are moving in a northerly direction, and if you are moving to the bottom of the map, you are moving towards the south. Any movement to the right will be towards the east and a movement towards the left will be towards the west.
    • 3.3: Lab Exercise (Part A)
      The following problems are for practice; answers to these questions are provided at the end of the chapter.
    • 3.4: Contour Lines
      Contour lines allow a vertical dimension to be added to a map and represent elevations above sea level. Since each individual contour line connects points of equal elevation, then following that line in the real world means that you are staying at the same elevation while walking along that imaginary line. If you were to move off that line, you are either walking up or down in elevation.
    • 3.5: Lab Exercise (Part B)
      For Questions 5 through 9, refer to Figure 3.4 below, which shows a hill, an intermittent stream, and two index contours (darkened contour lines). Assume the contour interval for this map is 5ft, and the index contour that is crossing the stream has an elevation of 70ft.
    • 3.6: Drawing Contour Lines and Topographic Profiles
      As you draw a contour line on a map you will notice that the elevations on one side of your line will be lower elevations, and elevations on the other side of your line will be higher elevations. Once your contour lines are drawn, you will notice that you had to draw some lines closer together in some areas and wider apart in other areas and that you may have even enclosed an area by drawing a contour line in a circular pattern.
    • 3.7: Lab Exercise (Part C)
      This is a graded activity. The following pages must be printed and completed by the student and mailed to the instructor in order to be scored. Alternatively, you may scan the activity and send it electronically to the instructor; unreadable scans will not be accepted, so be sure to send in legible work.
    • 3.8: Topographic Maps Lab Assignment
      This Lab Assignment is to be mailed to your Instructor at the contact address recorded in the Syllabus. Make sure that you use additional postage if needed. There is no online assessment for the Topographic Maps Lab. Complete the entire assignment and mail to your instructor postmarked by the assignment deadline. You should make an extra copy to practice on and mail in a clean and neat version for grading. Make sure to include your name on every page and staple all of the pages together.

    Thumbnail: Topographic map of Swamp Canyon Trail portion of Bryce Canyon National Park. (Public Domain; National Park Service)