About the Hammer Projection
In 1889 David A. Aitoff devised his Aitoff elliptical azimuthal projection. This quickly inspired Ernst Hammer to produce an equal area equivalent in 1892. Hammer gave prominent credit to Aitoff in both the paper's title and text, hence this projection is also sometimes known as the "Hammer-Aitoff". This should not be confused with the original Aitoff projection, which it quickly replaced.
The Hammer projection is an azimuthal projection. With the exception of the equator, the parallels are curved. Excluding the straight prime meridian, all the meridians are elliptical arcs. The end result is a projection that is very similar to the Mollweide pseudo-cylindrical projection but the polar regions are show less shearing.
Author's Note: The Hammer projection is one of the better projections presented here at Equal-Area-Maps.com. It is arguably better than the Mollweide projection with slightly less shape distortion in the polar regions, and slightly greater aesthetics. However, software support is only moderate. The Hammer projection is supported by ESRI and the Proj4 library, but not Proj4JS.
See our interactive Hammer Projection world map (overlays disabled due to the lack of Proj4JS support).