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

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

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

Centered at Ada, OK

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.

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.

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.

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.

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.

Original Mercator Projection Map, 1569

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.

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

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

Mercator Projection Notice shapes and sizes! Robinson Projection

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.

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.

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?

Unusual Map Projections

Works Cited Morehead State University http://people.moreheadstate.edu/fs/j.holcomb/praxis.pdf Progonos Project http://www.progonos.com/furuti/MapProj/Dither/ProjAz/projAz.html University of California at Santa Barbara http://www.ncgia.ucsb.edu/projects/tobler/Projections/sld012.htm Visualizing Physical Geography Copyright © 2008 John Wiley and Sons Publishers Inc.