Polar Stereographic Projection

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Introduction

The polar stereographic projection is a method of projecting the earth’s surface onto a plane. With the pole as the center, the points on the earth’s surface are projected onto a plane tangent to the pole through rays. The core principle is to regard the earth as a sphere, with the pole as the viewpoint, the projection surface as a plane tangent to the pole, the meridians projected as radial straight lines, the latitudes projected as concentric circles, and the meridians and latitudes intersecting at right angles, presenting a spider web shape. This projection method can keep the local angles and shapes unchanged, with less deformation in polar regions, and can accurately maintain the relative distance relationship between points on the earth’s surface, ensuring that the direction on the map is consistent with the actual geographical direction.

Projection Method

The polar stereographic projection achieves accurate mapping of polar regions by projecting points on the earth’s surface onto a plane tangent to the poles through rays. The projection method is simple and intuitive, and can keep local angles and shapes unchanged, making it suitable for polar navigation, weather forecasting, military strategic deployment and other scenarios. However, this projection method has problems of area distortion and deformation in large-scale maps, so it is mainly suitable for mapping polar regions or mid- and high-latitude areas.

Pros

**Azimuth retention: **It can accurately keep the various directions on the map consistent with the actual geographical direction, which is very valuable in navigation and military applications.
**Distance accuracy: **The polar projection can accurately maintain the distance from the center of the polar region to the external point, which is of great significance in polar navigation and meteorological analysis.
**Flexible center point selection: **The center point can be selected at the pole or other important geographical locations according to needs, so as to highlight the information of a specific area.
**Wide range of applications: **It has a wide range of applications in many fields such as navigation, meteorology, military, and geographic information systems.

Cons

**Severe deformation: **The area near the center of the map has a high degree of fidelity, but as the distance from the center point increases, the deformation will become more and more serious. This phenomenon is particularly obvious when displaying a large-scale map.
Area distortion: Although the relative distance relationship between points on the surface is maintained, serious distortion of the area cannot be avoided. The area near the edge of the map will be significantly compressed or enlarged.
Limited viewing angle: It is suitable for map display within a 180-degree viewing angle, but it cannot cover the entire sphere. If global information needs to be displayed, other projection methods need to be used.
**Complex calculation: **Compared with other simple map projection methods, the mathematical calculation of the polar stereographic projection is more complicated, which requires more time and computing resources, and the entire mapping process requires the use of various professional knowledge.

Application Scenario

The polar stereographic projection is suitable for scenarios that need to highlight polar region information and maintain azimuth and distance accuracy, such as polar navigation, weather forecasting, military strategic deployment, and spatial analysis in geographic information systems. It has advantages in map drawing in mid- and high-latitude regions (such as 60°~90° north and south latitude), but attention should be paid to its deformation and area distortion in large-scale maps.

Example

Polar Stereographic Projection centered on -90 degrees longitude and 0 degrees latitude.

The stereographic map projection is shown centered on the south pole.

Mercator Projection

Transverse Mercator Projection

Wagner Projection

Longitude / Latitude Projection