Eckert IV projection is best used for thematic maps of the globe. An example of a thematic map is one depicting land cover.
Meridians are elliptical arcs that are equally spaced.
Parallels are straight lines that are unequally spaced and closer together at the poles.
See Meridians and Parallels. The poles and the central meridian are straight lines one half the length of the Equator.
"Scale is distorted north-south 40 percent along the Equator relative to the east-west dimension. This distortion decreases to zero at 40° 30’ N and S and at the central meridian. Scale is correct only along these parallels. Nearer the poles, features are compressed in the north-south direction" (Environmental Systems Research Institute, 1997).
World maps only.
Eckert IV Projection
Source: Snyder and Voxland, 1989