1. Map Projections
…are about presenting the round Earth on a flat surface.
Dutch painter of the 1600s…this painted in 1669
Vermeer’s Cartographer

2. What is a map projection?
A projection is a way to make a flat representation of the Earth

3. The only accurate representation of the earth is a globe.
Only a globe preserves the map qualities of area, shape, direction, and distance.

4. Why are all map projections distorted?
All map projections must distort size, shape, distance, or direction.
Watch the following video to find out why:

5. Why do we use maps vs. globes?
Brainstorm advantages that maps have over globes and write them on the board.
Portable, easily identify regions, easier to measure distance, is more specific in terms of information presented

6. Distortions
Every map MUST and DO have distortions that result from making a 2D representation of a 3D sphere.

7. Types of Distortions Shape: the shape is wrong Area: the size is wrong
Distance: distance between places is wrong
Direction: direction is wrong (north/south aren’t the top and bottom of the map, east/west aren’t to the sides)

8. Types of Map Projections
There are three main types of map projections:
Cylindrical/Mercator
Conic
Plane/Planar/Polar/Azimuthal

9. For Mercator projections, please know the following:
visual recognition
accuracies
distortions
uses

10. Mercator/Cylindrical Projection
Invented 1569, meant for navigating ships, direction is true-mimics a globe-lines of latitude/longitude are a right angles, show straight lines are loxodromes or rhumb lines-for “true” direction BUT
Distorts size-esp. North and South Poles-imagine the orange peel again-as you stretch out the peel-the equator stay true to size but the poles are stretch out to try and make it lie flat

11. Visual Recogintion
right angles
At what angle to lines of latitude and longitude intersect on a Mercator/cylindrical projection?

12. Accuracy / Distortions
Compare the size of landmasses on the Mercator/cylindrical projection on the left with the Robinson projection on the right to answer the following questions. 1. Which landmasses appear much larger on the cylindrical projection than they actually are? 2. Which landmasses on the cylindrical projection appear to be accurate in size?
Those in the Northern Hemisphere and Southern-near the Poles
Those closest to the Equator

13. Accuracy A C D B
A:B – travel south from point A
C:D – travel east from point C
Yes, direction appears to be accurate
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?

14. Uses
Watch the following video to see a common use of cylindrical/Mercator projections:
Navigating the sea

15. Video of cylindrical/Mercator projection

16. For Conic projections, please know the following:
visual recognition
accuracy
uses

17. Conic Projection

18. Visual Recognition

19. 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)
Longitude is straight but fans out, latitude is curved
In the mid latitudes hemisphere-around US and Australia
Size is distorted, shapes are correct

20. For Planar/Polar/Azimuthal projections, please know the following:
visual recognition
uses

21. Plane/Planar/ Polar/Azimuthal Projection

22. Visual Recognition

23. Accuracy
Planar projections are accurate at the point the projection touches the map

24. Distortions:
Shape distorted at edge of projection.

25. Uses: Great Circle Routes
The line created when you cut the globe in half connecting two points

26. Uses:
used by pilots because great circle routes appear as straight lines.

27. Compromise Projections
What do you think a compromise projection is?
Winkle Triple
Robinson Projection

28. For Gall-Peters projections, please know the following:
visual recognition
Why is considered politically correct?

29. Gall-Peters Projection
Compare the Gall-Peters(left) to the cylindrical projection(right).
Both projections have latitude & longitude at right angles. What differences do you see between the shape/size of landmasses.
Why is the Gall-Peters projection called the “politically correct” projection?
Considered the “politically correct” projection--a response to the Mercator’s greater distortion of the size of landmasses in the northern hemisphere.

30. Equal Area Map
area (size) is correct but other properties are distorted

31. Conformal Map
shape is correct but other properties are distorted

32. 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.

33. Summary Video