The Eckert IV and VI projections, presented by the German cartographer Max Eckert-Greiffendorff 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 ±40°30' (IV) and ±49°16' (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 -JKf4.5i -Bg30/g15 -Dc -A10000 -Wthinnest -Gwhite -Slightgray -P > GMT_eckert4.ps
The same script, with s instead of f, yields the Eckert VI map: