Two grid systems that divide the entire surface of the Earth into quadrilaterals of equal area

Employed with unconventional spacings, meridians and parallels can block out quadrilaterals equal in area upon the surface of a sphere. Such a grid system can be transferred to any map projection and still retain the property of reference to a common unit area on a sphere, regardless of the apparent distortions of the grid in mapped form. Hence, conformal projections can be used with subjects for which areal comparisons and analyses are important. Two methods of laying out the grids are given, one employing respaced parallels the other respaced meridians. Both result in patterns that can form quadrilaterals over a wide range of sizes, but the grid with respaced parallels is more accurate and legible.