Polar Stereographic

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Polar Stereographic may be used to accommodate all regions not included in the UTM coordinate system, regions north of 84°N and 80°S. This form is called Universal Polar Stereographic (UPS). The projection is equivalent to the polar aspect of the Stereographic projection on a spheroid. The central point is either the North Pole or the South Pole. Of all the polar aspect planar projections, this is the only one that is conformal.

Construction

Plane

Property

Conformal

Meridians

Meridians are straight.

Parallels

Parallels are concentric circles.

Graticule spacing

The distance between parallels increases with distance from the central pole.

Linear scale

The scale increases with distance from the center. If a standard parallel is chosen rather than one of the poles, this latitude represents the true scale, and the scale nearer the pole is reduced.

Uses

Polar regions (conformal).

In Universal Polar Stereographic (UPS) system, the scale factor at the pole is made 0.994, thus making the standard parallel (latitude of true scale) approximately 81°07’N or S.

The point of tangency is a single pointeither the North Pole or the South Pole. If the plane is secant instead of tangent, the point of global contact is a line of latitude (Environmental Systems Research Institute, 1992).

Polar Stereographic is an azimuthal projection obtained by projecting from the opposite pole. All of either the northern or southern hemispheres can be shown, but not both. This projection produces a circular map with one of the poles at the center.

Polar Stereographic stretches areas toward the periphery, and scale increases for areas farther from the central pole. Meridians are straight and radiating; parallels are concentric circles. Even though scale and area are not constant with Polar Stereographic, this projection, like all stereographic projections, possesses the property of conformality.

The Astrogeology Center of the Geological Survey at Flagstaff, Arizona, has been using the Polar Stereographic projection for the mapping of polar areas of every planet and satellite for which there is sufficient information.

Define the origin of the map projection in both spherical and rectangular coordinates. Ellipsoid projections of the polar regions normally use the International 1909 spheroid (Environmental Systems Research Institute, 1992).

Longitude below pole of map    Longitude directed straight down below the pole for a north polar aspect, or straight up from the pole for a south polar aspect. This is equivalent to centering the map on a specific meridian.

Latitude of true scale    Latitude at which true scale is wanted. For secant projections, specify the latitude of true scale as any line of latitude other than 90°N or S. For tangential projections, specify the latitude of true scale as the North Pole, 90 00 00, or the South Pole, -90 00 00 (Environmental Systems Research Institute, 1992).

The figure below shows Polar Stereographic Projection and its geometric construction.

Polar Stereographic Projection

map_projection_polar_stereographic