Topographic MapsTopographic Maps

Pg 598 - 601Pg 598 - 601

Lesson ObjectivesLesson Objectives

Define a topographic map and its uses.Define a topographic map and 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 symbols Identify the meanings of some symbols and colors used on topographic maps.and colors used on topographic maps.

Create a topographic profileCreate a topographic profile

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 elevation/shape of the land using the elevation/shape of the land using contour lines. contour lines.

Elevation - how high and low the Elevation - how high and low the ground is in relation to sea level.ground is in relation to sea level.

What are contour lines?What are contour lines?

Contour lines are Contour lines are lines that connect lines that connect points that are of the points that are of the samesame elevation. elevation.

Contour lines never Contour lines never touch or cross.touch or cross.

What is a benchmark?What is a benchmark?

A benchmark is a point where exact A benchmark is a point where exact elevation is known and is marked elevation is known and is marked with a brass or aluminum plate.with a brass or aluminum plate.

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

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

A contour interval is the difference in A contour interval is the difference in elevation between two contour lines elevation between two contour lines that are side by side.that are 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 if my contour lines are close What if my contour lines are close together?together?

If the contour lines If the contour lines are close together, are close together, then that indicates then that indicates that area has a 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 If the contour lines are far apart, then are far apart, then that indicates the that indicates the land has a gentle 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 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.

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

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

Hachure Lines/DepressionHachure Lines/Depression

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 to remember that they It is important to remember that they point in the opposite direction as the point in the opposite direction as the flow of water.flow of 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, Black – Roads, buildings, railroads,

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

Topographic ProfileTopographic Profile1.1. Pencil the line of your interest in lightly Pencil the line of your interest in lightly

on your mapon your map

2.2. Place a blank piece of paper along the Place a blank piece of paper along the line you have drawn. line you have drawn.

3.3. On both the blank paper and the map, On both the blank paper and the map, mark clearly the starting and ending mark clearly the starting and ending points of your line of section. Below points of your line of section. Below these marks, write down the elevation of these marks, write down the elevation of the starting and ending points of your the starting and ending points of your section.section.

4.4. Make a tic mark Make a tic mark wherever the paper wherever the paper crosses a contour crosses a contour line on the map. line on the map. Write the elevation Write the elevation of the index of the index contours below contours below their tics on your their tics on your paperpaper

5.5. Get a piece of graph paper that is at Get a piece of graph paper that is at least as long as your line of section. least as long as your line of section. Place your paper with the tic marks Place your paper with the tic marks on the graph paper and mark the on the graph paper and mark the starting and ending points of your starting and ending points of your line.line.

Beginning with your starting Beginning with your starting elevation, go directly above the tic elevation, go directly above the tic mark on your paper and make a mark on your paper and make a small dot on the graph paper at the small dot on the graph paper at the corresponding elevation. Connect the corresponding elevation. Connect the dots on the graph paper.dots on the graph paper.

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?