Eckert 4 (Eckert IV)
This projection and the similar Eckert 6 are only used for maps of the entire world. Part of a set of six projections presented by Max Eckert in 1906 of Germany, but only IV and VI have been used to any great extent. It is usually found on thematic maps showing world climate conditions or population distribution.
Note: In each of the six projections, the pole lines are half the length of the Equator. In Eckert 4, the parallels are not equally spaced apart but all are straight lines. The central meridian is straight, the outer meridians, at 180 degrees, are semi-circles. The rest are elliptical arcs, spaced equally apart. It is an equal-area projection.