Sinusoidal

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Sometimes called the Sanson-Flamsteed, Sinusoidal is a projection with some characteristics of a cylindrical projectionoften called a pseudocylindrical type. The central meridian is the only straight meridianall others become sinusoidal curves. All parallels are straight and the correct length. Parallels are also the correct distance from the Equator, which, for a complete world map, is twice as long as the central meridian.

Construction

Pseudocylinder

Property

Equal-area

Meridians

Meridians are sinusoidal curves, curved toward a straight central meridian.

Parallels

All parallels are straight, parallel lines.

Graticule spacing

Meridian spacing is equal and decreases toward the poles. Parallel spacing is equal. The graticule spacing retains the property of equivalence of area.

Linear scale

Linear scale is true on the parallels and the central meridian.

Uses

Portray areas that have a maximum extent in a north-south direction.

World equal-area projection in atlases to show distribution patterns.

Sinusoidal maps achieve the property of equal-area but not conformality. The Equator and central meridian are distortion free, but distortion becomes pronounced near outer meridians, especially in polar regions.

Interrupting a Sinusoidal world or hemisphere map can lessen distortion. The interrupted Sinusoidal contains less distortion because each interrupted area can be constructed to contain a separate central meridian. Central meridians may be different for the northern and southern hemispheres and may be selected to minimize distortion of continents or oceans.

Sinusoidal is particularly suited for less than world areas, especially those bordering the Equator, such as South America or Africa. Sinusoidal is also used by the USGS as a base map for showing prospective hydrocarbon provinces and sedimentary basins of the world.

Sinusoidal Projection

map_projection_sinusoidal

Source: Snyder and Voxland, 1989