Geocart Projections

What is a projection?

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Miller cylindric

Classifications

Geocart menu class: Cylindric
Cylindric
Neither conformal nor equal area

Graticule

Meridians: Equally spaced straight parallel lines 0.73 as long as the Equator
Parallels: Unequally spaced straight parallel lines, closest near the Equator, but spacing does not increase poleward as fast as it does on the Mercator. Perpendicular to meridians.
Poles: Straight lines equal in length to the Equator
Symmetry: About any meridian or the Equator

Scale

True along the Equator in all directions
Constant in any given direction along any other given latitude; same scale at the latitude of opposite sign
Changes with latitude and direction

Distortion

None at the Equator. Shape, area, and scale distortion increases moderately away from the Equator but becomes severe at the poles.

Other features

Parallels are spaced from the Equator by calculating the distance for 0.8 of the same latitude on the Mercator and dividing the result by 0.8. Therefore, the two projections are almost identical near the Equator.

Usage

World maps in numerous American atlases and some other atlases, as a projection resembling the Mercator but having less distortion of area and scale, especially near the poles

Origin

Presented by Osborn Maitland Miller (1897–1979) of the American Geographical Society in 1942

Aspects

Normal aspect is commonly used.
Oblique aspect has been used by the National Geographic Society.

Similar projections

Gall projection has different spacing of parallels. The lines of no distortion are at latitudes 45° N. and S. rather than at the Equator. Miller proposed other alternates in 1942, including one identical with his preferred cylindrical but using two-thirds instead of 0.8.

Description adapted from J.P. Snyder and P.M. Voxland, An Album of Map Projections, U.S. Geological Survey Professional Paper 1453. United States Government Printing Office: 1989.