5.5.2 Mollweide Projection (-–Jw -–JW)

This pseudo-cylindrical, equal-area projection was developed by 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$^{o}$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:

$\bullet$

The central meridian

$\bullet$

Scale along equator in inch/degree or 1:xxxxx (-Jw), or map width (-–JW)

An example centered on Greenwich can be generated thus:

#!/bin/sh
#    $Id: GMT_mollweide.sh,v 1.1 2001/03/21 04:10:21 pwessel Exp $
#

pscoast -R-180/180/-90/90 -JW0/4.5i -Bg30/g15 -Dc -A10000 -G0 -P > GMT_mollweide.ps

Figure 5.27: World map using the Mollweide projection