A flat map so drawn that equal units of actual (or represented) area in any two portions of the map have identical map areas. For maps representing portions of the earth's surface this is obtained by continuously changing the scales of the meridians and parallels. Equal-area maps covering the whole globe, such as the Sanson–Flamsteed sinusoidal projection, are approximately elliptical. In Lambert's azimuthal equal- area projection, the parallels of latitude come closer together as the equator is approached. Any map of the whole world or of a hemisphere necessarily distorts the shape of a region far from the center of the map, but such maps are useful for some climatological studies in which the correct representation of area is important. For limited parts of the globe equal-area projections are quite practical. Compare conformal map.