The transverse Mercator was invented by Lambert in 1772. In this projection the cylinder touches a meridian along which there is no distortion. The distortion increases away from the central meridian and goes to infinity at 90o from center. The central meridian, each meridian 90o away from the center, and equator are straight lines; other parallels and meridians are complex curves. The projection is defined by specifying:
The optional latitude of origin defaults to Equator if not specified. Our example shows a transverse Mercator map of south-east Europe and the Middle East with 35oE as the central meridian:
pscoast -R20/30/50/45r -Jt35/0.18i -B10g5 -Dl -A250 -G200 -W0.25p -P >! GMT_transverse_merc.ps
pscoast -R0/360/-80/80 -JT-30/-45/3.5i -B30g15/15g15WSne -Dc -A2000 -G0 -P >! GMT_TM.ps
we made the map illustrated in Figure 5.20. Note that when a world map is given (indicated by -R0/360/s/n), the arguments are interpreted to mean oblique degrees, i.e., the 360o range is understood to mean the extent of the plot along the central meridian, while the ``south'' and ``north'' values represent how far from the central longitude we want the plot to extend. These values correspond to latitudes in the regular Mercator projection and must therefore be less than 90 degrees.