Despite the problems of extreme horizontal exaggeration with
latitude, the conformal Mercator projection (-–JM) remains
the stalwart of location maps used by scientists. It is one
of several cylindrical projections offered by GMT; here we
will only have time to focus on one such projection. The
complete syntax is simply
-–JMwidth
To make coastline maps we use pscoast which automatically will access the GMT coastline data base derived from the GSHHS database1.3. In addition to the common switches we may need to use some of several pscoast -specific options (see Table 1.2).
One of -–W, -–G, -–S must be selected. Our first coastline example is from Latin America:
pscoast –-R-90/-70/0/20 -–JM6i -–P -–B5g5 –-G180/120/60 >! map.ps