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<H2><A NAME="SECTION001443000000000000000">
6.4.3 Winkel Tripel projection (<B>-Jr</B> <B>-JR</B>)</A>
</H2>
<P>
<A NAME="21981"></A>
<A NAME="21982"></A>
<A NAME="21983"></A>
<P>
In 1921, the German mathematician Oswald Winkel a projection that was to strike a compromise between the properties of three elements (area, angle and distance). The German word ``tripel'' refers to this junction of where each of these elements are least distorted when plotting global maps. The projection was popularized when Bartholomew and Son started to use it in its world-renowned ``The Times Atlas of the World'' in the mid 20th century. In 1998, the National Geographic Society made the Winkel Tripel as its map projection of choice for global maps.
<P>
Naturally, this projection is neither conformal, nor equal-area. Central meridian and equator are
straight lines; other parallels and meridians are curved.
The projection is obtained by averaging the coordinates of
the Equidistant Cylindrical and Aitoff (not Hammer-Aitoff)
projections. The poles map into straight lines 0.4 times
the length of equator. To use it you must enter
<P>
<UL>
<LI>The central meridian [Middle of your map].
</LI>
<LI>Scale along equator in inch/degree or 1:xxxxx (<B>-Jr</B>), or map width (<B>-JR</B>).
</LI>
</UL>
<P>
Centered on Greenwich, the example in Figure <A HREF="#fig:GMT_winkel">6.27</A>
was created by this command:
<P>
<BR CLEAR="ALL">
<HR>
<BR>
<PRE>pscoast -Rd -JR4.5i -Bg30/g15 -Dc -A10000 -Ggray -P > GMT_winkel.ps
</PRE>
<BR CLEAR="ALL">
<HR>
<DIV ALIGN="CENTER"><A NAME="fig:GMT_winkel"></A><A NAME="22622"></A>
<TABLE>
<CAPTION ALIGN="BOTTOM"><STRONG>Figure 6.27:</STRONG>
World map using the Winkel Tripel projection.</CAPTION>
<TR><TD>
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<ADDRESS>
Paul Wessel
2010-01-14
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