Eckert IV

Description

This equal area projection is used primarily for world maps.

Projection method

A pseudo cylindrical equal-area projection.

Linear graticules

Parallels are unequally spaced straight lines, closer together at the poles. Meridians are equally spaced elliptical arcs. The poles and the central meridian are straight lines half as long as the equator.

Properties

Shape

Shapes are stretched north–south 40 percent along the equator, relative to the east–west dimension. This stretching decreases to zero at 40°30' N and S at the central meridian. Nearer the poles, features are compressed in the north–south direction.

Area

Equivalent.

Direction

Local angles are correct at the intersections of 40°30' N and S with the central meridian. Direction is distorted elsewhere.

Distance

Scale is distorted north–south 40 percent along the equator relative to the east–west dimension. This distortion decreases to zero at 40°30' N and S at the central meridian. Scale is correct only along these parallels. Nearer the poles, features are compressed in the north–south direction.

Limitations

Useful only as a world map.

Uses and applications

Thematic maps of the world, such as climate.

Parameters

Desktop

• False Easting
• False Northing
• Central Meridian

Note:

Supported on spheres only.

Eckert IV Auxiliary Sphere (Desktop version 9.3 and later)

• False Easting
• False Northing
• Central Meridian
• Auxiliary Sphere Type

Note:

The Auxiliary Sphere Type parameter accepts 0 (use semimajor axis or radius of the geographic coordinate system), 1 (use semiminor axis or radius), 2 (calculate and use authalic radius), or 3 (use authalic radius and convert geodetic latitudes to authalic latitudes).

Workstation

• Longitude of Central Meridian

Note:

Supported on spheres only.