Azimuthal Equidistant Projection

sc_projections_aziequidistant.png

 

An azimuthal projection that is neither equal-area nor conformal. The main feature of this projection is that it shows distances and directions correctly from the central point.

 

Scale

 

All distances measured from the center are true. Distances not measured along radii from the center are not correct.

 

Distortion

 

The center of the projection is the only point without distortion. Directions from the center are true, except on some oblique and Equatorial ellipsoidal forms.

 

Usage

 

Used in the polar aspect for world maps and maps of polar hemispheres. Used in the oblique aspect for atlas maps of continents and world maps for aviation and radio use. The ellipsoidal oblique aspect is used for the plane coordinate projection system in approximate form for Guam and in nearly rigorous form for islands in Micronesia.

 

Limitations

 

Use only for a single hemisphere at a time

 

Origin

 

Known for many centuries in the polar aspect. It is believed the Egyptians used the polar aspect for star charts, but the oldest existing celestial map using this projection was prepared in 1426 by Conrad of Dyffenbach. The first known use for polar maps of the Earth was by Gerardus Mercator as insets on his 1569 world map, which introduced his famous cylindrical projection.