Topographic Map Notes

Topographic Maps

A topographic map is a type of map that shows changes in elevation on Earth’s surface. Unlike regular maps, they use contour lines to represent the shape and height of the land. At first, these maps may look like squiggly lines and colors, but they provide valuable information about landforms.

What is a Topographic Map? 

 Contour lines are curved lines that show elevation on a topographic map. 

These lines are usually brown and represent a specific elevation above sea level. If you move your finger along a contour line, the elevation stays the same. 

Contour Lines

Contour Lines

Contour lines that are close together show steep slopes. 

Contour lines that are far apart show gentle slopes. 
Contour lines always connect to form a closed loop, even if they run off the edge of the map. 

A hill on a topographic map is shown as rings of contour lines that get smaller and smaller toward the peak.

Moving from one contour line to another means you are moving up or down in elevation.

Index contours are thicker contour lines with elevation numbers printed on them to help identify the height of the land.

Hill and Elevation

Contour Interval

The contour interval is the difference in elevation between contour lines. 

It is usually given in meters or feet.

Example: If a map has a contour interval of 3 meters, it means that each contour line represents a 3-meter elevation change. 

Map Scale

Map Scale shows the ratio of distances on the map to real-world distances. 

Example: 1:24,000 means that 1 inch on the map equals 24,000 inches (or 2,000 feet) in real life.

The United States Geological Survey (USGS) 

The United States Geological Survey (USGS)

The USGS is a federal agency that makes topographic maps of the entire U.S.
It was established in 1879 to study geology, hydrology, and topography.
The USGS helps investigate natural hazards such as volcanoes, earthquakes, and  landslides. 

Surveyors use scientific instruments to create accurate maps of the country.