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## 6.4.5 Eckert IV and VI projection (-Jk -JK)

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

- The central meridian [Middle of your map].
- Scale along equator in inch/degree or 1:xxxxx (-Jk), or map width (-JK).

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

Figure 6.29: World map using the Eckert IV projection.

The same script, with s instead of f, yields the Eckert VI map:

Figure 6.30: World map using the Eckert VI projection.

Next: 6.4.6 Sinusoidal projection (-Ji Up: 6.4 Miscellaneous projections Previous: 6.4.4 Robinson projection (-Jn Contents Index