Berghaus Star

Description

Hermann Berghaus designed this projection in 1879. Usually centered at the north pole, it can minimize breaks in land masses. The Association of American Geographers incorporated a version of the Berghaus star projection into the logo in 1911.

The Berghaus star projection with parameters set to match the look of the Association of American Geographers (AAG) logo.

Projection method

The Berghaus star projection uses an azimuthal equidistant projection for the central hemisphere. The other half of the world is split into five triangular pieces, forming a star around the circular center. If the latitude of origin is centered at a pole, parallels are circular arcs while meridians are straight lines, broken at the equator.

Linear graticules

The straightness of the latitude and longitude lines depends on the projection's center. If the center is at the north or south pole, longitude lines are straight, but broken at the equator, while latitude lines are circular arcs. If the latitude of origin is at the equator, the equator and the central meridian are straight lines. If the latitude of origin is elsewhere, only the central meridian is a straight line. For all cases except a polar case, latitude lines are complex curves.

Properties

Shape

Shapes are not maintained.

Area

Areas are not preserved.

Direction

Directions are preserved from the central point through a hemisphere of the globe. Directions are not preserved in the star portions.

Distance

Distances are accurate from the center point for a hemisphere. They are not accurate outside that point. As an example, when the center is a pole, distances are accurate from the pole to the equator only.

Limitations

Berghaus Star is useful for world maps only.

Uses and applications

The Berghaus star projection was used for world maps in several atlases in the 19th century. The logo of the Association of American Geographers contains a Berghaus star projection.

Parameters

Desktop

• False Easting
• False Northing
• Central Meridian
• Latitude of Origin
• XY Plane Rotation

The XY plane rotation parameter is used to rotate the projection based on the central point. If set to zero, the default, the star is oriented with a point extending down. An XY plane rotation value of 36 (degrees) will rotate the star counterclockwise so that there is now a point extending up towards grid north.