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.

Distortions

• Every map MUST have distortions that

result from making a 2D representation of a

3D sphere

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)

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. visual recognition

2. accuracies

3. distortions

4. 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

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?

A

B

C D

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/Polar/Azimuthal 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

Shape distorted at edge of projection.

Distortions:

Uses:

Great Circle Routes

• The line created when you cut the globe in

half connecting two points

• used by pilots because great circle routes appear as straight lines.

Uses:

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?

Equal Area Map

• area (size) is correct but other properties are

distorted

Conformal Map

• shape is correct but other properties are

distorted

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