Transcript By John Halverson, Arizona Geographic Alliance Adapted from a lesson by Doug Anderson, Utah Geographic Alliance.

By John Halverson, Arizona Geographic Alliance
Adapted from a lesson by Doug Anderson, Utah Geographic Alliance
What is the most accurate
representation of the
earth?
A globe
Why are globes the best
representation of the earth?
Positive Features
These 4 are called
“properties”
Proportional / Round
Correct Size
Correct Distance
Correct Shape
Correct Direction
But do you ever see a lost driver pull a
globe out of the glove compartment?
Negative Features
Not Convenient
Not Detailed
Only See a Section at a Time
Limited in Purpose
What would you use if you want something more
convenient, more detailed, with a special purpose, or
when you want to see the whole world at the same
time?
Any time you take a round
object and put it on a flat piece
of paper . . .
• Positive Features
• Negative Features
•
•
•
•
•
•
•
•
•
Proportional / Round
Correct Size
Correct Distance
Correct Shape
Correct Direction
Not Convenient
Not Detailed
Only See ½ at a Time
Limited in Purpose
Something is going to be DISTORTED.
How do you get from this…
To this…
To this?
What is Cartography?
mapmaking
Imagine a globe made of glass with
the shapes of the continents etched on
the surface. Now imagine a light at
the globe’s center projecting shadows
of the land masses in all directions.
The cartographer’s job is to draw the
shapes of those shadows on a flat
piece of paper and transform them
into a reasonable portrait of the
planet.
Map Projections
This first, crucial step in mapmaking is called the
“projection.” They are called projections because
originally, the maps were made by “projecting”
shadows on to paper. Projections fall into three
basic categories: planar, conic, and cylindrical.
• You’ve heard the phrase “seeing is believing.”
Let’s see if it is true with maps.
• Examine the map below. Which is larger in size,
Greenland or Australia?
Greenland = 836,109 sq. miles
Australia = 2,941,299 sq . miles
In real life Australia is more
than 3 times larger than
Greenland.
Cylinder Projection
Wrap the globe with a paper cylinder and
project the shapes onto the surface of the
paper. Trace the lines and shapes onto the
paper.
Slit the cylinder and flatten it into a map.
This projection is most accurate near the
Equator and greatly distorted near the
Poles.
The most famous cylindrical map is the
Mercator projection.
This projection has been used for over
400 years for navigation (direction), but
Is not very good for size and distance.
In real life, South
America is 9 times
larger than
Greenland!
Lets try an experiment with a map.
• Every one knows that Alaska is farther north than any other state.
• Using the map shown, write down the name of the state that is the
second farthest north (after Alaska)
Which state did you choose?
Washington?
Maine?
How do you measure how far north something is?
• The correct answer is Minnesota!
•Did you measure from how far UP the state is or how far NORTH?
• Measure how far Washington and Maine are from 50 degrees North.
If you didn’t pick the correct state, it might have something to do
with the map PROJECTION!
Conic Projection
Place a cone shaped paper over the globe to
achieve a conic projection.
Cut open the cone to make it flat.
The map will be least distorted along the line
where the cone touches the sphere.
Conic projections are handy for portraying the
United States, which fits nicely within the
resulting “smile-shaped” map.
In real life, are latitude lines straight or
curved?
So is the border between the US and
Canada straight or curved?
Let’s try another experiment
Look at the following map: What looks like
the shortest distance between California and
Japan?
Is it a straight line?
The shortest distance
Is actually the red line!
Why does it look longer?
It depends on the map
PROJECTION!
Planar Projection
(Azimuthal)
Place a flat piece of paper next to the globe so
that it touches the globe at a single point, and you
get a planar projection.
Because this projection, also known as an
azimuthal projection, is most accurate at its
center, it is often used for maps focusing on one
of the Poles.
What does the shortest distance
between California and Japan
look like on this map?
Map
Objectives
Picking the right projection is crucial for achieving
the map’s objective.
Mapmakers usually tailor their creations to focus on
area (or size), shape, distance, and direction
AREA or Size
Sometimes we want to compare geographical data based on area.
Thus we have to pick a projection that maintains the correct
proportions among the sizes of Earth’s landmasses.
This is often called an “equal-area” projection.
The price of getting the sizes right, however, is distortion in the
shapes of the continents and direction between places.
SHAPE
Preserving the shape of places is harder as the area covered gets larger.
A world map can only preserve the continents’ shapes by distorting their
sizes. Maps that stress shape are called “conformal.”
DISTANCE
Most students are taught that the shortest distance between two points
is a straight line. Not on most maps.
The shortest distance between any two spots on earth is actually a
“great circle.”
Shapes and sizes will be distorted especially at the outer edges.
DIRECTION
Many navigational charts rely on projections focused on direction.
This was especially important in the past when the best sailing
instrument was a compass. The Mercator Map shows latitude and
longitude lines always meeting at right angles (like they do on the round
earth) so sailors could take a compass bearing that would match the
map.
What are you looking for?
The National Geographic Society has
changed it preferred projections for its
world reference maps.
In 1922 the Society adopted the Van der
Grinten projection, which encloses the
world in a circle.
Their cartographers switched in 1988 to
the Robinson projection, on which the
high latitudes are less distorted in size
(but more so in shape).
A decade later, the Society began using the
Winkel Tripel projection, which provides a
better balance between size and shape.
Exaggeration
• Take a look at the map.
• If you saw a satellite
image of the same place
at the same scale, how
big would the roads
look?
• We have to exaggerate
the size of the roads
with colors and symbols
or we couldn’t see them.
(They’re not that wide
on the surface of the
earth!)
Generalization
• Take a look at the map.
• The light green is a
deciduous forest and the
orange is tall prairie grass.
• Imagine you were
standing on the line where
the two zones meet.
Would you expect to see a
line where the trees end
and the grass starts?
Maps are designed to generalize what certain
places are like rather that what the earth is exactly like.
Scale
• Another important
aspect of a map is
scale.
• Cartographers
generally use 3 ways
of showing scale on
maps:
– Fraction/Ratio
– Bar/graphic
– Written statement
1:63360 or 1/63360
One inch equals one mile
Large v. Small Scale
• Maps are said to be “large” or “small” scale based
on the ratio or fraction compared to the earth.
• Which is a larger fraction?
1/10000 or 1/100000000
• While 1/10000 is a larger fraction, it shows a
smaller area of the earth, but in larger detail.
• One way to remember this is that a large scale
map shows individual features larger (closer up)
than small scale maps.
Which map shows the largest scale?
A
B
C
D
How would you explain the following statement…
All Maps Lie.
The Key Words are:
Distortion
Exaggeration
Generalization
The TRUTH about All Maps Lie:
1) All maps are flat, the earth is not.
2) All maps distort at least one of the following items:
Size
Shape
Distance
Direction
3) Straight lines on the earth may appear curved lines on
some maps.
4) North is not always “up.”
5) Shortest distance between two points may not appear to
be straight on some map.
6) Many maps exaggerate features (so they show up).
7) Maps tend to generalize (simplify) information rather
than show what the earth is “really” like.
Explain the cartoon below:
Remember:
Anytime you take a round
object and put it on a flat piece
of paper something will be
DISTORTED!
Procedures
You will choose and complete one of the three
projects from this choice board.
Copyright © 2010 American
Heritage School
Examples from the project created by 7th grade students at
Desert Sands
Copyright © 2010 American
Heritage School
Copyright © 2010 American
Heritage School
Copyright © 2010 American
Heritage School
Copyright © 2010 American
Heritage School
Assessment
Your Project will be graded with a
rubric. Look at the rubric before
beginning your work.
Copyright © 2010 American
Heritage School