All equal-area maps have their best application as statistical maps, but they are also useful as general reference maps. Their greatest weakness is their distortion of shapes. This can be somewhat alleviated by interruption; but this has drawbacks also, since relationships across a split on the map are lost.
The Sinusoidal projection is one of the earliest equal-area projections developed. It utilizes horizontal lines, equally spaced in proportion to the true distances between latitudes. These latitude lines are then equally divided into the true proportional distance between meridian lines. The result gives a true area map that presents fairly good shapes up to the edges of the projection. Interruption can improve further on these shapes.