MAPSPROJECTIONS

AND SCALE

ALL MAPS LIE FLAT

AND

ALL FLAT MAPS LIE!

Map projections

• There are many types of projections. Here are a few:

• Robinson

• Goode’s

• Eckert IV Equal Area

• Mercator

• Mollweide Equal Area

• Peters

Issues

• Each type of map projection has problems—and the biggest problem is trying to fit a round globe onto a flat surface!

• Based on tables of coordinates, not mathematical formulas. The projection distorts shape, area, scale, and distance in an attempt to balance the errors of projection properties.

• Tears, or interruptions, minimize specific distortions. They are placed to group related parts of the map together. The Goode homolosine projection uses four distinct interruptions that cut through the oceans but leave major land masses untouched.

• The central meridian and all parallels are at right angles, all other meridians are sinusoidal curves. Shape distortion increases at the poles. Scale is correct at standard parallels of 49:16 North and South.

• Straight meridians and parallels that intersect at right angles. Scale is true at the equator or at two standard parallels equidistant from the equator. Used for marine navigation because all straight lines on the map are lines of constant azimuth.

• The central meridian is straight. The 90th meridians are circular arcs. Parallels are straight, but unequally spaced. Scale is true only along the standard parallels of 40:44 N and 40:44 S.

• De-emphasizes area exaggerations in high latitudes by shifting the standard parallels to 45 degrees.

Scale

• Large scale—objects are large (large detail)

• E.g. 1:10,000

• Small scale—shows more of the Earth but the detail is less.

• E.g. 1:1,000,000

Images showing scale—

Seattle, Washington

Satellite view of the United States

Map of the United States

The United States