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By John Halverson, Arizona Geographic AllianceAdapted 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
Proportional / RoundCorrect SizeCorrect DistanceCorrect ShapeCorrect Direction
These 4 are called “properties”
But do you ever see a lost driver pull a globe out of the glove
compartment? Negative Features
Not ConvenientNot Detailed
Only See a Section at a Time
Limited in Purpose What would you use if you want something moreconvenient, 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
• Proportional / Round• Correct Size• Correct Distance• Correct Shape• Correct Direction
• Negative Features
• 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?
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.
What is Cartography?
mapmaking
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.
Then why d
oes
Greenland lo
ok so big on
the m
ap?
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.
Cylinder Projection
This projection has been used for over400 years for navigation (direction), but Is not very good for size and distance.
In real life, SouthAmerica is 9 times
larger thanGreenland!
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!
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.
Conic Projection
In real life, are latitude lines straight orcurved?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!
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.
Planar Projection (Azimuthal)
What does the shortest distancebetween California and Japan look like on this map?
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
Map Objectives
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.
AREA or Size
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.”
SHAPE
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.
DISTANCE
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.
DIRECTION
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.
What are you looking for?
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
Copyright © 2010 American Heritage School
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
Assessment
Copyright © 2010 American Heritage School
Your Project will be graded with a rubric. Look at the rubric before beginning your work.
