Hammer - an equal-area map projection, described by Ernst Hammer in 1892. Directly inspired by the Aitoff projection, Hammer suggested the use of the equatorial form of the Lambert azimuthal equal-area projection instead of Aitoff's use of the azimuthal equidistant projection. Visually, the Aitoff and Hammer projections are very similar, but the Hammer has seen more use because of its equal-area property.