The Eckert IV and VI projections, presented by Max Eckert in 1906, are pseudocylindrical equal-area projections. Central meridian and all parallels are straight lines; other meridians are equally spaced elliptical arcs (IV) or sinusoids (VI). The scale is true along latitudes 4030' (IV) and 4916' (VI). Their main use is in thematic world maps. To select Eckert IV you must use -JKf (f for ``four'') while Eckert VI is selected with -JKs (s for ``six''). If no modifier is given it defaults to Eckert VI. In addition, you must enter
Centered on the Dateline, the Eckert IV example below was created by this command:
pscoast -Rg -JKf180/4.5i -Bg30/g15 -Dc -A10000 -W0.25p -Gwhite -Slightgray -P > GMT_eckert4.ps
The same script, with s instead of f, yields the Eckert VI map: