Classifications
pseudocylindric
Graticule
Meridians: Central meridian is a straight line half as long as the equator. Other meridians are equally spaced sinusoids, concave toward the central meridian.
Parallels: Equally spaced straight parallel lines. Perpendicular to the central meridian.
Poles: Lines half as long as the equator.
Symmetry: About the central meridian or the equator.
Scale
True along latitudes 37°55′N and S., if the world map retains correct total area.
Constant along any given latitude; same for the latitude of opposite sign.
Distortion
No point is free of all distortion, but the equator is free of angular distortion.
Similar projections
Eckert VI projection has meridians positioned identically, but parallels are spaced for equal-area.
Winkel I is an average of coordinates of the sinusoidal and equirectangular projections.
Wagner III projection uses part rather than all of the sinusoidal curve for meridians.
Putniṇš P5´ is very similar, but scaled larger.
Origin
Presented by Max Eckert (1868-1938) of Germany in 1906. The projection is an arithmetical average of the x and y coordinates of the sinusoidal and Plate Carree projections.
Description adapted from J.P. Snyder and P.M. Voxland, An Album of Map Projections, U.S. Geological Survey Professional Paper 1453. United States Government Printing Office: 1989.