Geocart Projections

What is a projection?

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Mollweide

homolographic

homalographic

Babinet

elliptical

Classifications

Geocart menu class: Pseudocylindric
Pseudocylindric
Equal area

Graticule

Meridians: Central meridian is a straight line half as long as the Equator. Meridians 90° E. and W. of the central meridian form a circle. Others are equally spaced semiellipses intersecting at the poles and concave toward the central meridian.
Parallels: Unequally spaced straight parallel lines, farthest apart near the Equator; spacing changes gradually. Perpendicular to the central meridian.
Poles: Points
Symmetry: About the central meridian or the Equator

Scale

True along latitudes 40°44' N. and S.
Constant along any given latitude; same for the latitude of opposite sign

Distortion

Severe near outer meridians at high latitudes but can be substantially reduced if interrupted with several central meridians. Free of distortion only at latitudes 40°44' N. and S. on the central meridian.

Usage

Occasional world maps, especially thematic maps. Combined with Sinusoidal projection to develop other projections such as the Goode Homolosine and the Boggs.

Origin

Presented by Carl B. Mollweide (1774-1825) of Germany in 1805

Aspects

For educational purposes, it has been shown in various aspects as examples of normal, transverse, and oblique aspects of almost any pseudocylindrical projection. The transverse aspect has also been used by John Bartholomew in The Times Atlas in England in 1958.

Other names

Homolographic projection
Homalographic projection
Babinet projection
Elliptical projection

Similar projections

Goode Homolosine (Mollweide merged with Sinusoidal)
Boggs Eumorphic (Mollweide averaged with Sinusoidal)
Bromley, by Robert H. Bromley in 1965 (Mollweide compressed from north to south with east-west expansion to achieve no distortion along the Equator)
Hyperelliptical, by Waldo R. Tobler in 1973 (equal-area pseudocylindrical having “hyperelliptical” meridians that lie between the Mollweide ellipses and a circumscribed rectangle)

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.