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## 6.4.2 Mollweide projection (-Jw -JW)

This pseudo-cylindrical, equal-area projection was developed by the German mathematician and astronomer Karl Brandan Mollweide in 1805. Parallels are unequally spaced straight lines with the meridians being equally spaced elliptical arcs. The scale is only true along latitudes 40°44' north and south. The projection is used mainly for global maps showing data distributions. It is occasionally referenced under the name homalographic projection. Like the Hammer projection, outlined above, we need to specify only two parameters to completely define the mapping of longitudes and latitudes into rectangular x/y coordinates:

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

An example centered on Greenwich can be generated thus:

    pscoast -Rd -JW4.5i -Bg30/g15 -Dc -A10000 -Gblack -P > GMT_mollweide.ps

Figure 6.26: World map using the Mollweide projection.

Next: 6.4.3 Winkel Tripel projection Up: 6.4 Miscellaneous projections Previous: 6.4.1 Hammer projection (-Jh Contents Index