McBryde-Thomas flat-pole sinusoidal

III

Classifications

pseudocylindric
equal-area

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: Unequally spaced straight parallel lines, widest separation near the equator. Perpendicular to the central meridian.
Poles: Lines one-third as long as the equator.
Symmetry: About the central meridian or the equator.

Scale

True along latitudes 55°51′N and S. Constant along any given latitude; same for the latitude of opposite sign.

Distortion

Free of distortion only at latitudes 55°51′N and S. On the central meridian.

Usage

Basis of merged projections by McBryde (see McBryde S3).

Similar projections

Sinusoidal projection uses sinusoids for meridians, but the poles are points.
Eckert VI projection uses sinusoids for meridians and is equal-area, but the poles are lines half as long as the equator.

Origin

Presented by F. Webster McBryde and Paul D. Thomas through the U.S. Coast and Geodetic Survey in 1949.

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.