1. PSC 121 Prince George's Community College

2. PSC 121 Prince George's Community College

3. Topographic maps
A topographic map shows the shape of the Earth’s surface by using contour lines.

4. Creating the contour map
Imagine slicing through a
mountain with
a perfectly flat, horizontal piece of glass.
The intersection of the mountain with the glass is a
line of constant elevation and becomes a
contour line.
Creating the contour map

6. PSC 121 Prince George's Community College
Map Scale
There are also scales that can be used to determine distance for many different units using a ruler and the map scale.
1 mile
1 mile
1/2 mile
2000 feet
1 kilometer
200 feet
PSC 121 Prince George's Community College

7. PSC 121 Prince George's Community College
Steep or flat?
Elevation change
= 20 feet
Gradient 20ft/0.5 mi = 40 ft/mi
Flat
Elevation change
= 600 feet
Gradient 600ft/0.5 mi = 1200 ft/mi
Steep
0.5 mile distance
PSC 121 Prince George's Community College

8. Tracking Flowing Water
You can look at the contour lines as they cross the stream. They will always point upstream.
Downstream
Upstream
PSC 121 Prince George's Community College