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 90° from center. The central meridian, each meridian 90° 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. Although defaulting to 1, you can change the map scale factor via the MAP_SCALE_FACTOR parameter. Our example shows a transverse Mercator map of south-east Europe and the Middle East with 35°E as the central meridian:
pscoast -R20/30/50/45r -Jt35/0.18i -B10g5 -Dl -A250 -Glightgray -Wthinnest -P > GMT_transverse_merc.ps
The transverse Mercator can also be used to generate a global map--the equivalent of the 360° Mercator map. Using the command
pscoast -R0/360/-80/80 -JT330/-45/3.5i -B30g15/15g15WSne -Dc -A2000 -Gblack -P > GMT_TM.ps