Topographic MapsTopographic Maps

One way to see isolines at work…One way to see isolines at work…do you know what type of isoline do you know what type of isoline

is used in Topo Maps?is used in Topo Maps?

OK…first of all..OK…first of all..

• What is a Topographic Map?• A TOPOGRAPHIC map is a 2 dimensional

model of how a certain landscape looks• What is a contour line? • On a topographic map, the isolines

connect point of equal elevation• You need to try to use your imagination to

see what the landscape might look like in 3-D (in real life)

Top and Side View of Island 1.1

Island 1.1

• Which part of the island has the steepest slope? (use the profile view to help you)

• That’s right, the EAST side!

• Which side is relatively flat?

• Of course! The West Side!

Island 1.1

• Ok, so now….MARK the highest point on the island profile with an “H”

• Now MARK the highest point on the top view with an “H”

Island 1.1

• What do you notice about the spacing of the contour lines on the steep side of the island?

• Yup, they’re spaced CLOSE TOGETHER

Island 1.1

• What about the spacing of the contour lines on the “flat” (level) side of the island?

• Uh huh – they’re spaced FAR APART!

Island 1.1

• If the elevation of sea level is 0 meters, and each contour line 10 meters higher than the last, LABEL each contour line on the top view of the island.

• How high is the highest contour line on the map? • That’s right – 50 meters!

1020 30

Diagram 1.1

• What is a contour interval?• A contour interval is the difference in elevation

between 2 consecutive lines on a topo map• CONTOUR INTERVALS remain the same for

the entire map!! • So, what is the contour int. of diagram 1.1?

10 2030

Diagram 1.1

• Notice how the top contour line (the 50th) is darkened more than the others

• Every 5th contour line (sometimes 4th) is darkened in for easier reading

• These darkened lines are called “INDEX CONTOURS” and are in whole round numbers (like 50, 100, 200, etc.)

Ok, now for a NEATO trick!

• There is a way to calculate a contour interval!

• This is VERY helpful if you have trouble figuring it out

• You subtract 2 known contour lines from each other and then just divide that number by the number of SPACES between the 2 lines you just subtracted!

Holy Moly that was a mouthful..

• Check out how easy this is though!

• I will show you 3 maps, and we will figure out the contour intervals together

• Ready????

• Let’s do it!

Map A

• What is the contour interval here?

• 40-0=40

• 40 divided by 4 spaces = 10 m!!

Map B

• What is the contour interval here?

• 60-0 = 60

• 60 divided by 3 spaces = 20m!

Finally, Map C

• What’s the contour interval here?

• 100-0 = 100

• 100 divided by 4 spaces = 25m

Moving Along…Moving Along…

• To show elevations of land that GOES DOWN INTO Earth like a mine, quarry, or sinkhole, a SPECIAL contour line is used

• It’s called a HACHURE line, and looks like what you have in your notes!

• The small “whiskers” always point towards the lower elevation

• The 1st hachure line is always given the same value as the NON-HACHURE contour line before it

• Ok, so let’s try this…..

Diagram 1.2Diagram 1.2

• OK, label the contour lines on diagram 1.2

• The C.I. is 10m• The depression has

been labeled for you• Remember, the

hachure line has been given the SAME value as the last non hachure line before!

How did you do? How did you do? I know, this stuff is easy, yo!

10

20

OK, now for some practice..OK, now for some practice..

• Ok, now it’s time for you to label the next 2 diagrams COMPLETELY

• Label ALL lines

• The contour intervals have been given beneath the diagrams

• Go to it, and ask for help if you don’t understand!

How did you do?How did you do?

What is Relief?What is Relief?

• Pepto Bismol!!!• Actually, it’s the way the landscape (the shape

of Earth’s surface) is portrayed on a map – mountains, hills, valleys, plateaus, plains (lowlands), etc.

• A relief map is a map that shows all of these things in 3D (with raised surfaces and everything)

• This is different than a topo map – they show the landscape in 2D (on flat paper)

Compass RoseCompass Rose

• A compass rose is a set of axes that have directions labeled on them

• I know many of you have seen simple ones before….

They look like this!!They look like this!!

OK, so label the one YOU OK, so label the one YOU have..have..

north (N) south (S) east (E) west (W) northeast (NE)

northwest (NW)

southeast (SE) southwest (SW)

east-northeast (ENE)

west-northwest (WNW) 3

east-southeast (ESE)

west-southwest (WSW)

north-northwest (NNW)

north-northeast (NNE)

south-southeast (SSE)

Which direction is missing from the list?? ______________________________________________

Which direction is missing from the list?

How did you do?

Let’s discuss a few things…Let’s discuss a few things…