PSC 121 Prince George's Community College Topographic Maps More than a Road Map

Morning! ► Check your mailboxes! ► Begin working on “Hero’s Journey” once you have the supplies PSC 121 Prince George's Community College

Topographic Maps

What is a Topographic Map? In contrast to most maps, a topographic map shows the shape of the Earth’s surface by using contour lines. In contrast to most maps, 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. All points on the same contour line have the same elevation.

PSC 121 Prince George's Community College What is a Topographic Map? ► Scaled representation of features on the surface of the Earth ► Provides information about land elevations and landforms such as mountains, hills, and depressions

PSC 121 Prince George's Community College Contour Lines Elevation is indicated by contour lines. A contour line is a line of equal elevation. All points on a contour line have the same elevation. 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. 20 ft elevation increase 20 ft elevation decrease r.htm

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.

PSC 121 Prince George's Community College Steep or flat? You can tell whether a region on a map is steep terrain (hill/mountain) or relatively flat (plain) by looking at contour lines. HOW? Let’s take a look….

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

PSC 121 Prince George's Community College Map Symbols Marsh Stream Forest Intermittent Stream Secondary Highway Houses

Let’s take a walk up a hill!

We’re now at an elevation of 100 meters. 100m

Let’s keep going! 100m

Now we’re at 200m. 100m 200m

Shall we march on? 100m 200m

We’ve made it to 300m! 100m 200m 300m

On to the peak! 100m 200m 300m

We’re on the peak, but what’s our elevation? 100m 200m 300m

Any ideas? 100m 200m 300m Let’s add contour lines for every 50 meters and see if that helps.

100m 200m 300m We know that we are above 350m, but less than 400m. 50m 150m 250m 350m

100m 200m 300m Let’s head down the hill, it’s getting late! 50m 150m 250m 350m

100m 200m 300m Now what’s our elevation? 50m 150m 250m 350m If you said somewhere between 200m and 250m you are right!

100m 200m 300m Let’s try this again! 50m 150m 250m 350m

100m 200m 300m What’s our elevation now? 50m 150m 250m 350m If you said 50m or just under, you’re right!

Let’s now look at the same hill, but the way we might see it from an airplane!

Each color change represents a 50 meter increase.

Now, let’s try the same hike! Our elevation is 0 meters.

Now what is our elevation?

If you said more than 150 meters, but less than 200 meters your right!

Let’s go a little higher.

Think you know our elevation now? More than 300meters But less than 350meters

If we were standing on the peak, what would be our elevation? ► More than 350 meters, less than 400 meters

Let’s head down hill.

Know our elevation?

More than 100 meters, less than 150 meters

PSC 121 Prince George's Community College Let’s practice Identifying topographic profiles on the back of page 2 -Then back to notes on rivers

PSC 121 Prince George's Community College Tracking Flowing Water ► How does water always flow? DOWNHILL ► How can we tell what direction (N,S,NW,ESE) is downhill?

PSC 121 Prince George's Community College Tracking Flowing Water Look for elevation changes, since water will flow from higher to lower elevations. Here the stream flows toward the northwest ft2000 ft

PSC 121 Prince George's Community College Tracking 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

PSC 121 Prince George's Community College Tracking 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