Geocart Projections

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Eckert III

Classifications

Geocart menu class: Pseudocylindric
Geocart family: Eckert
Pseudocylindric
Equally spaced parallels
Neither conformal nor equal area

Graticule

Meridians: Central meridian is a straight line half as long as the Equator. Other meridians are equally spaced semiellipses, concave toward the central meridian. The outer meridians (180° east and west of the central meridian) are semicircles.
Parallels: Equally spaced straight parallel lines. Perpendicular to the central meridian.
Poles: Lines half as long as the Equator
Symmetry: About the central meridian or the Equator

Scale

True along latitudes 35°58' N. and S., if the world map retains correct total area (area varies locally). Constant along any given latitude; same for the latitude of opposite sign.

Distortion

No point is free of all scale distortion, but the Equator is free of angular distortion.

Origin

Presented by Max Eckert (1868-1938) of Germany in 1906

Similar projections

Eckert IV has meridians positioned identically, but parallels are spaced for equal area.
Putnins P1', has meridians that are only portions of semiellipses, but parallels are equidistant.

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.