Fig. 1.6. Equal-area map with superimposed grid. One square at the equator represents a surface area of about 1,240,000 square kilometers. On this map land is green even if it is covered by ice. This map does not show sea ice.
Image by Byron Inuoye
Title
Map Distortion
NGSS Performance Expectations
NGSS PE Linking Sentence
The content and activities in this topic will work towards building an understanding of how maps distort continents and ocean basins.
Body
Map Types
Two types of maps commonly used to show the surface areas of the ocean basins and continents are equal-area maps and cylindrical-projection maps (see Figs. 1.6 and 1.7). In Figs. 1.7 and 1.8, a grid is superimposed on the map. At the equator of each map one square represents a surface area of about 1,240,000 square kilometers (or 1.24 X 106 km2).
Fig. 1.7. Cylindrical-projection map with superimposed grid. One square at the equator represents a surface area of about 1,240,000 square kilometers. On this map land is green even if it is covered by ice. This map does not show sea ice.
Image by Byron Inuoye
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Fig. 1.8 (A) equal-area map creation
Image courtesy of Carlos Furuti
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Fig. 1.8 (B) cylindrical projection map creation
Image courtesy of Carlos Furuti
An equal-area map is created by treating the earth like an orange. To get the orange peel to lay flat, it is necessary to make a lot of cuts (Fig. 1.8 A). To make a cylindrical-projection map, think of the earth as a clear globe with black outlines of its features lit from within. To make a flat map, the globe is wrapped in a paper cylinder and the projections of the outlines are traced (Fig. 1.8 B).
Table of Contents
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