Next: 6.2.2.1 Polar Stereographic Map Up: 6.2 Azimuthal projections Previous: 6.2.1.2 Hemisphere map Contents Index

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6.2.2 Stereographic Equal-Angle projection (-Js -JS)

This is a conformal, azimuthal projection that dates back to the Greeks. Its main use is for mapping the polar regions. In the polar aspect all meridians are straight lines and parallels are arcs of circles. While this is the most common use it is possible to select any point as the center of projection. The requirements are

- 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 90°).
- Scale as 1:xxxxx (true scale at pole), slat/1:xxxxx (true scale at standard parallel slat), or radius/latitude where radius is distance on map in inches from projection center to a particular [possibly oblique] latitude (-Js), or simply map width (-JS).

A default map scale factor of 0.9996 will be applied by default (although you may change this with MAP_SCALE_FACTOR). However, the setting is ignored when a standard parallel has been specified since the scale is then implicitly given. We will look at two different types of maps.

Subsections

- 6.2.2.1 Polar Stereographic Map
- 6.2.2.2 Rectangular stereographic map
- 6.2.2.3 General stereographic map

Next: 6.2.2.1 Polar Stereographic Map Up: 6.2 Azimuthal projections Previous: 6.2.1.2 Hemisphere map Contents Index