Topographic Maps

What is a Topographic Map? ► Provides information about land elevations and landforms such as mountains, hills, and depressions

What is a Topographic Map? A topographic map shows the shape of the Earth’s surface by using contour lines. A topographic map shows the shape of the Earth’s surface by using contour lines.

Contours are imaginary lines that join points of equal elevation above or below sea level.

PSC 121 Prince George's Community College Contour Lines All points on the same contour line have the same elevation. The elevation difference from one line to another is called the contour interval. 800 feet 700 feet r.htm

PSC 121 Prince George's Community College Contour Lines When only some lines are marked, the marked lines are called index contours. 800 feet 700 feet r.htm

PSC 121 Prince George's Community College Contour Lines The elevation difference from one line to another is called the contour interval. On the map portion below the contour interval is 20 ft. r.htm How to calculate –. 1)Find the difference between the index contours: _______ 2)Count the lines from one index contour to the next: _______ 3)Divide: ________

PSC 121 Prince George's Community College Contour Lines The contour interval is usually printed on a topographic map. However, you can always calculate the interval from the lines with values. from the lines with values.

Other information ► There are many things we can learn about an area from looking at a topographic map…. PSC 121 Prince George's Community College

Steep or flat? Flat!Steep! The closer together the contour lines, the steeper the terrain.

PSC 121 Prince George's Community College Map Symbols Topographic maps usually have a separate sheet with an explanation of map symbols. There is no room on the map for all the symbols Sample page from USGS Topo Map Symbol Pamphlet

Map Symbols Marsh Stream Forest Intermittent Stream Secondary Highway Houses

Direction of Flowing Water ► How does water always flow? DOWNHILL ► How can we tell what direction is downhill?

Direction of Flowing Water Look for elevation changes, since water will flow from higher to lower elevations. Here the stream flows toward the northwest ft2000 ft

Direction of Flowing Water Look at the contour lines as they cross the stream. They will always point upstream (the direction the water is flowing from). DownstreamUpstream

Direction of Flowing Water You can also look at where two streams merge. The merge will form a V that points downstream. Direction of flow

Draw a arrow in your notes showing the direction of flow

Depressions ► Hachure lines are used to indicate depressions in topography ► This figure represents a crater: PSC 121 Prince George's Community College

Bathymetric Maps Maps of water depths are like topographic maps with contours. However, the contours are water depths, not elevations.