Topographic MapsTopographic Maps

Created by T. BatesCreated by T. Bates

Hugo A. Owens Middle SchoolHugo A. Owens Middle School

Adapted and edited by B. FerriAdapted and edited by B. Ferri

Lesson ObjectivesLesson Objectives Define a topographic map and state Define a topographic map and state

its uses.its uses. Describe how contour lines show the Describe how contour lines show the

elevations, shape, and slope of the elevations, shape, and slope of the land.land.

Identify the meanings of some Identify the meanings of some symbols and colors used on symbols and colors used on topographic maps.topographic maps.

What is a topographic map?What is a topographic map? A topographic map, also A topographic map, also

known as a known as a contourcontour map, map, is a map that shows the is a map that shows the shape of the landshape of the land using using contour lines. contour lines.

It is a map that shows an elevation It is a map that shows an elevation field, meaning how high and low the field, meaning how high and low the ground is in relation to ground is in relation to sea levelsea level..

Contour Maps show the elevation of the land.

What are contour lines?What are contour lines? Contour lines are lines Contour lines are lines

that connect points that connect points that are of the same that are of the same elevationelevation..

Contour lines Contour lines nevernever touch or crosstouch or cross..

They show the exact They show the exact elevation, the shape of elevation, the shape of the land, and the the land, and the steepnesssteepness of the land’s of the land’s slopeslope..

What is a benchmark?What is a benchmark? A benchmark is a point where exact A benchmark is a point where exact

elevationelevation is known and is marked is known and is marked with a brass or aluminum plate. It is with a brass or aluminum plate. It is marked marked BMBM on the map with the on the map with the elevation numbers given in feet.elevation numbers given in feet.

Benchmarks are useful to help Benchmarks are useful to help determine contour lines.determine contour lines.

Other Topographic TermsOther Topographic Terms Map scale – compares distances on Map scale – compares distances on

the map with distances on Earth.the map with distances on Earth. Legend – explains symbols used on Legend – explains symbols used on

the map.the map.

Index contours – Index contours – contour lines that contour lines that are labeled to help are labeled to help you find the you find the contour interval.contour interval.

What is a contour interval?What is a contour interval? A contour interval A contour interval

is the is the differencedifference in in elevation between elevation between two contour lines two contour lines that are that are side by side by sideside..

Remember that aRemember that a

contour interval is contour interval is

notnot the the distancedistance between the two lines between the two lines to get the distance you need to use the to get the distance you need to use the

map map scalescale..

580580

560560540540

520520Contour interval =

20 feet

What if my contour lines are close What if my contour lines are close together?together?

If the contour lines are close together, If the contour lines are close together, then that indicates that area has a then that indicates that area has a steep slope.steep slope.

What if my contour lines are far What if my contour lines are far apart?apart?

If the contour lines are far apart, then If the contour lines are far apart, then that indicates the land has a gentle that indicates the land has a gentle slope (low slope).slope (low slope).

What do the dark colored contour What do the dark colored contour lines mean?lines mean?

The dark colored contour lines The dark colored contour lines represent every fifth contour line to represent every fifth contour line to make it easier to read the map.make it easier to read the map.

What do depressions in the map look like?What do depressions in the map look like?

A depression, such as A depression, such as the inside of a dead the inside of a dead volcano, is volcano, is represented by represented by hachure lines.hachure lines.

Hachure lines are Hachure lines are regular contour lines regular contour lines with small segments with small segments sticking out from it.sticking out from it.

The first hachure line is at the same elevation The first hachure line is at the same elevation as the contour line before it.as the contour line before it.

More on Contour LinesMore on Contour Lines Contour lines form V’s that point Contour lines form V’s that point

upstream when they cross a stream.upstream when they cross a stream. It is important It is important

to remember to remember that they that they point in the point in the opposite opposite direction as direction as the flow of the flow of water.water.

What do the colors on the What do the colors on the topographic map represent?topographic map represent?

Blue lines/shapes - represent water Blue lines/shapes - represent water features, such as streams and lakes.features, such as streams and lakes.

Brown – contour linesBrown – contour lines Black – Roads, buildings, railroads, other Black – Roads, buildings, railroads, other

man made objects.man made objects. Green – Woodland areasGreen – Woodland areas Red - HighwaysRed - Highways

Now that I know what a topographic Now that I know what a topographic map is, how do I read it?map is, how do I read it?

First determine the contour interval First determine the contour interval (the distance between each contour (the distance between each contour line)line)

Then determine the map scale (usually Then determine the map scale (usually at the bottom of the map)at the bottom of the map)

Identify any hills or depressionsIdentify any hills or depressions Use the legend to identify man made Use the legend to identify man made

features.features.

Reading a topographic map cont.Reading a topographic map cont.

Look for areas where Look for areas where the contour lines are the contour lines are close together – they close together – they indicate a steep area.indicate a steep area.

Look for areas where the contour lines Look for areas where the contour lines are spread apart – they indicate a are spread apart – they indicate a gentle slope.gentle slope.

1. Contour Interval means “what every line is worth”.2. The rule of the Contour V’s

Streams and rivers flow opposite to the point of the V that is

formed when a contour line crosses them.3. Close contour lines means that there is a steep slope.4. Contour lines that are far apart mean that the land is flatter.5. The Gradient Formula is used to calculate the slope.6. Gradient means slope.7. Bulls eyes represent hills or mountains.8. Hachured lines on bulls eyes mean depressions or valleys.9. Each line represents a different elevation in feet or meters.10. Places on the same contour line are at the same elevation.11. A Profile is a side view or real representation of the

topography of an area.

Review QuestionsReview Questions How are contour lines drawn on How are contour lines drawn on

maps?maps? How does a contour map show How does a contour map show

whether a slope is gentle or steep?whether a slope is gentle or steep? What is a benchmark?What is a benchmark? How is a benchmark shown on a How is a benchmark shown on a

map?map? How is distance measured on a How is distance measured on a

contour map?contour map?