Topographic MapsTopographic Maps
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 known as a A topographic map, also known as a
contour map, is a map that shows contour map, is a map that shows the shape of the land using contour the shape of the land using contour line. line.
Other Topographic TermsOther Topographic Terms
Map scale Map scale – compares distances on – compares distances on the map with distances on earth.the map with distances on earth.
LegendLegend – explains symbols used on – explains symbols used on the map.the map.
Index contours Index contours – contour lines that – contour lines that are labeled to help you find the are labeled to help you find the contour interval.contour interval.
It is a map that shows an elevation field, meaning how high and low the ground is in relation to sea level.
What is a benchmark?What is a benchmark? A benchmark is a point A benchmark is a point
where exact elevation is where exact elevation is known and is marked known and is marked with a brass or aluminum with a brass or aluminum plate. It is marked BM on plate. It is marked BM on the map with the the map with the elevation numbers given elevation numbers given in feet.in feet.
Benchmarks are useful to Benchmarks are useful to help determine contour help determine contour lines.lines.
What are contour lines?What are contour lines? Contour lines are lines Contour lines are lines
that connect points that that connect points that are of the same elevation.are of the same elevation.
They show the exact They show the exact elevation, the shape of elevation, the shape of the land, and the the land, and the steepness of the land’s steepness of the land’s slope.slope.
Contour lines never touch Contour lines never touch or cross.or cross.
What is a contour interval?What is a contour interval?
A contour interval is A contour interval is the difference in the difference in elevation between two elevation between two contour lines that are contour lines that are side by side.side by side.
Remember that a contour interval is Remember that a contour interval is not the distance between the two not the distance between the two lines – to get the distance you need lines – to get the distance you need to use the map scale.to use the map scale.
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 if my contour lines are close What if my contour lines are close together?together?
If the contour lines are close If the contour lines are close together, then that indicates that together, then that indicates that area has a steep slope.area has a 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, If the contour lines are far apart, then that indicates the land has a then that indicates the land has a gentle slope (low slope).gentle slope (low slope).
More on Contour LinesMore on Contour Lines Contour lines form Contour lines form
V’s that point V’s that point upstream when they upstream when they cross a stream. cross a stream.
It is important to It is important to remember that they remember that they point in the opposite point in the opposite direction as the flow direction as the flow of water.of water.
What do depressions in the map What do depressions in the map look like?look like?
A depression, such as the inside of a A depression, such as the inside of a dead volcano, is represented by dead volcano, is represented by Hachure lines.Hachure lines.
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, Black – Roads, buildings, railroads,
other man made objects.other 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?
1.1. First determine the contour interval First determine the contour interval (the distance between each contour (the distance between each contour line)line)
2.2. Then determine the map scale (usually Then determine the map scale (usually at the bottom of the map)at the bottom of the map)
3.3. Identify any hills or depressionsIdentify any hills or depressions
4.4. 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 the contour Look for areas where the contour lines are close together – they lines are close together – they indicate a steep area.indicate a steep area.
Look for areas where the contour Look for areas where the contour lines are spread apart – they indicate lines are spread apart – they indicate a gentle slope.a gentle slope.
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?
