Geocart Projections

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McBryde-Thomas flat-pole sinusoidal

Classifications

Pseudocylindrical
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)

Origin

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

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.

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.