The Polar Stereographic projection somewhat resembles other polar azimuthal projections, with straight radiating meridians and concentric circles for parallels. This projection is used for polar mapping within the Universal Polar Stereographic (UPS) coordinate system.
The "Polar Stereographic" projection has the following parameters:
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False Northing
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False Easting
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Longitude of the Natural Origin of the Projection
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Latitude of the Natural Origin of the Projection
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Scale Reduction Factor at the Natural Origin of the Projection.
Using these parameters, there are two different variations of the Polar Stereographic projection that can be supported.
When using the first variation (referred to as Variant A by EPSG) the Scale Factor must be a value other than 1. In this variation, the Latitude of Origin is used only to identify the hemisphere of the projection, and thus the only valid values are ±90° or the equivalent in an alternate angle unit.
When using the second variation (referred to as Variant B by EPSG) the Scale Factor must be equal to 1, and will thus be ignored. The actual scaling factor will be calculated by using the value of the Latitude of Origin parameter which in this case actually represents the Latitude of the Standard Parallel (i.e. the Latitude of True Scale). In this case the sign of the Latitude is likewise used to determine the hemisphere of the projection.