Exercise 1: Map projections as essential tools of physical oceanography.

Page 7

The British cartographer James Gall presented his cylindrical equal area projection to the British Association in 1855. It uses 45° latitude as reference and projects all points between 45°N and 45°S inward onto the cylinder, while all points north of 45°N and south of 45°S are projected outwards as before. The diagram on the right illustrates this: All points on the earth's surface are projected in or out parallel to the reference latitude. The result is a map of the earth on the part of the cylinder that is inside the grey areas.

At the time of its design, Gall's map and other cylindrical equal area projections were considered interesting mathematical experiments. Their use for everyday cartography was not obvious at the time.

The shape of Gall's map comes close to the size of today's standard office paper and to the size of computer screens, which makes it attractive for use in books and computer displays. It was developed again, independently of Gall's earlier efforts, in 1974 by the German historian Arno Peters and is now known as the Gall-Peters projection.

This is an example of a Gall/Peters map. Like the Lambert projection, the Gall/Peters projection allows the continuation of the map in east-west direction by matching of the left and right map boundaries.

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This page last updated 5 December 1999