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## 6.3.9 Cylindrical stereographic projections (-Jcyl_stere -JCyl_stere)

The cylindrical stereographic projections are certainly not as notable as other cylindrical projections, but are still used because of their relative simplicity and their ability to overcome some of the downsides of other cylindrical projections, like extreme distortions of the higher latitudes. The stereographic projections are perspective projections, projecting the sphere onto a cylinder in the direction of the antipodal point on the equator. The cylinder crosses the sphere at two standard parallels, equidistant from the equator. The projections are defined by:

- The central meridian (uses the middle of the map when omitted).
- The standard parallel (default is the Equator). When used, central meridian needs to be given as well.
- Scale in inch/degree or as 1:xxxxx (-Jcyl_stere), or map width (-JCyl_stere)

Some of the selections of the standard parallel are named for the cartographer or publication that popularized the projection (Table 6.3).

Table 6.3: Standard parallels for some cylindrical equal-area projections.
Projection | Standard parallel
Miller's modified Gall | 66.159467°
Kamenetskiy's First | 55°
Gall's stereographic | 45°
Bolshoi Sovietskii Atlas Mira or Kamenetskiy's Second | 30°
Braun's cylindrical | 0°

A map of the world, centered on the Greenwich meridian, using the Gall's stereographic projection (standard parallel is 45°, Figure 6.24), is obtained as follows:

    gmtset PLOT_DEGREE_FORMAT dddA
    pscoast -R-180/180/-60/80 -JCyl_stere/0/45/4.5i -Ba60f30g30/a30g30 -Dc -A5000 -Wblack -Ggrey -P \
            > GMT_gall_stereo.ps

Figure 6.24: World map using Gall's stereographic projection.

Next: 6.4 Miscellaneous projections Up: 6.3 Cylindrical projections Previous: 6.3.8 Miller Cylindrical projection Contents Index