Using a Topographic Map

Identifying Symbols

The symbols on a topographic map are used consistently to identify key, relatively stable features of the landscape. See the chart of below for a list of symbols commonly found on topographic maps.

The most widely used symbols are for ecosystems
Green shading indicates a wooded area
Open grass and farmlands are white
Sand dunes and coastal dunes are tan with speckles
Lakes and oceans are colored blue
Perennial streams and rivers are blue lines
An intermittent stream is a broken blue line of dots and dashes
A spring is a circle with a squiggle
Marshes have short blue horizontal lines
Mangrove forests are shown as squiggle lines on top of green
Trees planted by humans, including orchards and golf courses, are shown as green circles in rows
Urban areas, including cities and towns, are shaded in gray or red.
New information added by aerial photograph to the map is shown in purple.

There are symbols for land uses that are common across this country.

Gravel pits
Quarries
Mine tunnels
Power transmission lines*
Railroads- multiple track*
Railroads- single track
Campgrounds
Primary highway*
Unimproved roads
Bridges
Trails
House of worship*
School
Cemetery
Building*
Water tank
The most widely used symbols for features on topographic maps
Contour lines*
Ridges
Valley
Peak
Saddle
Depression

* Indicates where slight changes to symbols and symbol names were made on 2/16/14 based on the National 4-H Forestry Invitational changes

Interpreting Topographic Features

The surface of the earth is not flat, but a two-dimensional map is. The strategy for converting the planet's hills and valleys to a flat piece of paper involves all the little brown contour lines on a topographic map. They indicate topography – the shape of the land. A contour line joins all the places of equal elevation. The value of a contour interval depends on the map. Every 5th line is usually an index contour line; it is heavier and has an elevation reading along it. By subtracting two elevations and dividing by the number of intermediate contour lines between them, you can determine the vertical distance between two adjacent lines. In flat landscapes that may be 10 feet. In mountainous areas it may be 100 feet.

The way the lines are drawn indicate the shape of the land. Ridges and valleys, peaks and flat land, saddles (the low part between two hills) and depressions (noted by hatch marks inside a contour line) can be interpreted from the lines on a map. (See the chart below)

You can practice converting shapes to topographic lines. Imagine a basketball. Cut it in half. Place the cut side on the floor. If you were to connect all the points on the half-sphere that are the same distance above the floor, you would draw concentric circles around the outside of the ball. If you put all those circles on a piece of paper, what would it look like? If you turn a wastebasket upside down and did the same thing, what would it look like? Which drawing looks more like an upside down kitchen funnel?

When the shape is steep, the lines are closer together. When the increase is very gradual, the lines are farther apart. When the shape is flat, there are no lines. Why?

 

Calculating Distance

Each topographic map has a legend at the bottom that indicates the correlation between inches on the map and inches in the real world.  A 7.5 minute map (indicating the latitudinal distance covered in one map) usually has a scale of 1:24,000, or 1 inch on the map equals 24,000 inches on the ground (24,000 inches equals 2,000 feet). The legend also provides a scale (which resembles a ruler) that shows miles, feet, kilometers, and meters. You can use this scale as you would a ruler to determine the straight line distance between points on a map.

 

Exercise on Topographic Maps

The Air and Waste Management Association created a number of delightful classroom exercises to teach some basic concepts. This activity, called Watershed Woes, helps learners understand topographic maps to identify a watershed. Many of their explanations are useful for teaching youth to read the topographic lines in a map. Watershed Woes Topographic Map Exercise

 

Worksheet on Map Symbols

This worksheet could be a useful quiz to help learners review map symbols. It comes from the Air and Waste Management Association’s Watershed Woes activity.

Topography Symbol Workseet

Topography Symbol Answers

 

Learn More

You can learn more about symbols and features from these websites: