Map Projections
…is about presenting the
round Earth on a flat
surface.Map
Projections:
Vermeer’s Cartographer
What is a map projection?
• A projection is a way to make a flat
representation of the Earth
The only accurate representation
of the earth is a globe.
Only a globe preserves
the map qualities of
area, shape, direction,
and distance.
Why are all map projections distorted?
• All map projections must distort size, shape,
distance, or direction.
Watch the following video to find out why:
http://goo.gl/oxC3v
Why do we use maps vs. globes?
Brainstorm advantages that maps have over
globes and write them below.
Types of Map Projections
There are three main types of map projections
A. Cylindrical/Mercator
B. Conic
C. Plane/Planar/Polar/Azimuthal
For Mercator projections, please know
the following:
1.
2.
3.
4.
visual recognition
accuracy
distortions
uses
Mercator/Cylindrical Projection
Visual Recogintion
At what angle to lines of latitude and longitude intersect
on a cylindrical projection?
Accuracy /
Distortions
Compare the size of landmasses on the cylindrical projection on the left with the Robinson
projection on the right to answer the following questions.
Which landmasses appear much larger on the cylindrical projection than they actually are?
Which landmasses on the cylindrical projection appear to be accurate in size?
Accuracy
A
C
D
B
What direction would you travel to get from ‘A’ to ‘B’?
What direction would you travel to get from ‘C’ to ‘D’?
Does direction appear to be accurate on a Mercator Projection?
Uses
Watch the following video to see a common
use of cylindrical/mercator projections
http://goo.gl/obRzv
Video of cylindrical/mercator projection
• http://goo.gl/AE5bR
For Conic projections, please know the
following:
1. visual recognition
2. accuracy
3. uses
Conic Projection
Visual Recognition
Watch this: http://goo.gl/rJKp4
Answer these:
What visual clue is covered that will help you
recognize a conic projection? (visual recognition)
What parts of the world do conic projections show
accurately? (accuracy/uses)
What is distorted, size or shape? (distortions)
For Planar projections, please know the
following:
1. visual recognition
2. uses
Plane/
Planar/
Polar/
Azimuthal Projection
Visual Recognition
Accuracy
• Planar projections are accurate at the point
the projection touches the map
Distortions:
Shape distorted at edge of projection.
Uses:
Great Circle Routes
• The line created when you cut the globe in
half connecting two points
Uses:
• used by pilots because great circle routes
appear as straight lines.
Great Circle Route
This video shows planes travelling on great
circle routes to Sydney, Australia
http://goo.gl/lYnjw
Compromise Projections
With out using the internet or book, what do
you think a compromise projection is?
For Gall-Peters projections, please
know the following:
1. visual recognition
2. Why is considered politically correct?
Gall-Peters Projection
Compare the Gall-Peters(left) to the cylindrical projection(right).
1. Both projections have latitude & longitude at right angles. What differences do you
see between the shape/size of landmasses.
2. Why is the Gall-Peters projection called the “politically correct” projection?
For Robinson projections, please know
the following:
1. visual recognition
Robinson Projection
How do distortion levels of a Robinson Projection compare to distortion
levels in other map projections?
For Interrupted projections, please
know the following:
1. visual recognition
Interrupted Projections:
visual recognition
Interrupted Projections
Interrupted Projections
Why might you want to use this projection?
• We are used to looking at maps that are centered
on the Prime Meridian.
VI. The Big Idea
A. All map projections have distortions.
B. Each projection has its own advantages and disadvantages
depending on the purpose of the map.
Summary Video
http://goo.gl/TG8XM