Equal Angle / Equal Area Comparison

EQUAL ANGLE projection preserves the geometry of projected shapes. The area on the surface of the sphere, represented by a projected region, depends on its location. The projected area of a given circle increases towards the equator of the projection (see below for illustration).

EQUAL AREA projection distorts geometrical shapes such as small circles (circles with centers not coincident with that of the sphere). Nevertheless, a constant area on the projection represents a constant area on the surface of the sphere, regardless of its location. This method reduces visual bias in comparisons between data clusters in different parts of the sphere.

 

EQUAL ANGLE projection

EQUAL AREA projection

image\eq_ang5.gif

Pole Plot

image\eq_ar4.gif

Pole Plot

image\eq_ang7.gif

Contour Plot

image\eq_ar6.gif

Contour Plot

image\eq_ang9.gif

Small Circles, 15° cone angle

(circles remain circular, but increase in area towards the equator)

image\eq_ar8.gif

Small Circles, 15° cone angle

(circles have equal area, but become elliptical towards equator)