The ability to see whether a map is equal-area, conformal, or neither is useful for looking intelligently at large-area maps. For example, only if a map is equal-area can reliable judgments of relative size be made. If a map is equal-area, latitude-longitude cells are equal in size between a given pair of parallels, the cells between a given pair of meridians get smaller toward the poles, cells the same number of degrees on either side of the equator are equal in size, and linear scale change in one direction is balanced by an opposite change in the perpendicular direction. If a map is conformal, parallels and meridians meet at right angles, linear scale change in one direction is the same as in the perpendicular direction, and the map is obviously not equal-area. If at least one observation is violated for both equal-area and conformal, the projection is neither. No flat map can be both.