Map projections and the visual detective: How to tell if a map is equal-area, conformal, or neither

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 meridians get number of degrees on either side of the 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 linear the map is obviously not equal-area. If at equal-area and conformal, the projection is neither. No flat map can be both.