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## 6.2.5 Azimuthal Equidistant projection (-Je -JE)

The most noticeable feature of this azimuthal projection is the fact that distances measured from the center are true. Therefore, a circle about the projection center defines the locus of points that are equally far away from the plot origin. Furthermore, directions from the center are also true. The projection, in the polar aspect, is at least several centuries old. It is a useful projection for a global view of locations at various or identical distance from a given point (the map center).

To specify the azimuthal equidistant projection you must supply:

- Longitude and latitude of the projection center.
- Optionally, the horizon, i.e., the number of degrees from the center to the edge (180°, default is 180°).
- Scale as 1:xxxxx or as radius/latitude where radius is distance on map in inches from projection center to a particular [possibly oblique] latitude (-Je), or map width (-JE).

Our example of a global view centered on 100°W/40°N can therefore be generated by the following pscoast command. Note that the antipodal point is 180° away from the center, but in this projection this point plots as the entire map perimeter:

    pscoast -Rg -JE-100/40/4.5i -B15g15 -Dc -A10000 -Glightgray -Wthinnest -P > GMT_az_equidistant.ps

Figure 6.13: World map using the equidistant azimuthal projection.

Next: 6.2.6 Gnomonic projection (-Jf Up: 6.2 Azimuthal projections Previous: 6.2.4 Orthographic projection (-Jg Contents Index