## Geocart Projections

What is a projection?

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Lambert azimuthal equal-area

zenithal equal-area

zenithal equivalent

Classifications

Azimuthal
Equal area
Nonperspective

Graticule

Polar aspect:
Meridians: Equally spaced straight lines intersecting at the central pole. Angles between them are the true angles.
Parallels: Unequally spaced circles, centered at the pole, which is a point. Spacing of the circles gradually decreases away from the pole. The entire Earth can be shown, but the opposite pole is a bounding circle having a radius 1.41 times that of the Equator.
Symmetry: About any meridian
Equatorial aspect:
Meridians: Central meridian is a straight line. Meridian 90° away is a circle. Other meridians are complex curves, unequally spaced along the Equator and intersecting at each pole. Spacing decreases away from the central meridian.
Parallels: Equator is a straight line. Other parallels are complex curves concave toward the nearest pole. They are unequally spaced along the central meridian, and spacing decreases away from the Equator. Along the meridian 90° from the central meridian, parallels are equally spaced.
Symmetry: About the central meridian or the Equator
Oblique aspect:
Meridians: Central meridian is a straight line. Other meridians are complex curves intersecting at each pole shown.
Parallels: Complex curves unequally spaced along the central meridian; spacing decreases away from the center of projection
Symmetry: About the central meridian

Range

Entire Earth

Scale

True only at the center in all directions. Decreases with distance from the center along radii. Increases with distance from the center in a direction perpendicular to radii.

Distortion

Only the center is free from distortion. Distortion is moderate for one hemisphere but becomes extreme for a map of the entire Earth.

Usage

Frequently used in the polar aspect in atlases for maps of polar regions and of Northern and Southern Hemispheres. The equatorial aspect is commonly used for atlas maps of the Eastern and Western Hemispheres. The oblique aspect is used for atlas maps of continents and oceans. The equatorial and oblique aspects are used by the U.S. Geological Survey in cooperation with others for maps of the Circum-Pacific Map Project.
Recommended for equal-area maps of regions approximately circular in extent

Origin

Presented by Johann Heinrich Lambert (1728–1777) of Alsace in 1772

Other names

Lorgna (for polar aspect, due to independent derivation, 1789)
Zenithal Equal-Area
Zenithal Equivalent

Similar projections

W. William-Olsson's projection combines the Lambert Azimuthal Equal-Area with a modified Werner.

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.