1. By Mrs. Page (with a LOT of help from the Internet!)

2. Map Projections
Map projections are attempts to portray the surface of the earth or a portion of the earth on a flat surface. Some distortions of shape, distance, direction, scale, and area always result from this process.
The purpose, or function of the map, determines what projection should be used
The geographic location determines what projection should be used

3. Centered at Lawrence, Kansas, the geographic center of the “Lower 48” States

4. Centered at Ada, OK

5. The Geographic Grid
Latitude and Longitude Latitude is measured north and south of the equator, up to 90º
Longitude is measured east and west of the Prime Meridian—meridian that passes through Greenwich, England—up to 180º
Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc.

6. Many types of maps, for many different purposes
Map Projections
Many types of maps, for many different purposes
Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc.

7. 1 unit of map distance=50,000 units of distance on the Earth
Map Projections
1:50,000
1 unit of map distance=50,000 units of distance on the Earth
Map Scale
Scale fraction: a ratio that tells how to convert distance on the map to true distance on the Earth
Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc.

8. Each map projection has a specific purpose
Map Projections
Map projection: a system of parallels and meridians representing the Earth’s curved surface drawn on a flat surface
Curved surface cannot be projected onto a flat sheet without distortion
Each map projection has a specific purpose
Each projection has advantages and drawbacks
Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc.

9. Mercator Projection
The Mercator projection has straight meridians and parallels that intersect at right angles.
Scale is true at the equator or at two standard parallels equidistant from the equator.
The projection is often used for marine navigation because all straight lines on the map are lines of constant compass bearing.
Mercator is a cylindrical projection. Cartographers start by wrapping a cylinder around the globe along the equator.

10. Original Mercator Projection Map, 1569

11. Invented 1569 by Gerardus Mercator Used for navigation
Map Projections
Mercator projection: map projection with horizontal parallels and vertical meridians
Invented 1569 by Gerardus Mercator
Used for navigation
Scale increases from equator to poles
Straight line on the map is a line of constant compass bearing
Straight line on a Mercator projection not the shortest distance between two points
Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc.

12. Robinson Projection (1961)
Neither conformal nor equidistant
Compromises shape and size
Longitude lines are curved

13. Robinson Projection
This grid plot shows the distortion factor of the Robinson projection.
The Robinson projection with Tissot's Indicatrix of deformation

14. Mercator
Projection
Notice shapes and sizes!
Robinson
Projection

15. Shows true sizes of regions on Earth’s surface
Map Projections
Goode Projection: Equal-area map projection often used to display information such as climate or soil type
Shows true sizes of regions on Earth’s surface
Distorts shapes of places, especially high latitudes and at edges of map
Called an “interrupted projection”
This is sometimes called an “orange peel” projection. Can you guess why?
Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc.

16. Used for maps of polar regions Scale increases outward
Map Projections
Azimuthal (polar) projection: map projection centered on Earth’s North or South Pole
Used for maps of polar regions
Scale increases outward
Shows only one hemisphere
Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc.

17. Lambert Azimuthal Equal-Area Projection
Maps from a sphere to a disk.
It accurately represents area in all regions of the sphere, but it does not accurately represent angles.
It gives a planar picture of the sphere in which every region appears with the correct area but perhaps a greatly distorted shape.
Here’s an azimuthal projection from the
South Pole. What continents do you see?

18. Unusual Map Projections

27. Works Cited
Morehead State University
Progonos Project
University of California at Santa Barbara
Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc.