Eckert IV
and VI
The Eckert
IV and Eckert VI were created by Max Eckert in 1906, and are used for
world maps. Both are Pseudocylindrical projections whose central meridian
is a straight line. 180th meridians of the Eckert IV projection are cemicircle,
and all other meridians are equally spaced elliptical Arcs. Meridians
on the Eckert VI projection are equally spaced sinusoidal curves. In both
projections, the parallels are unequally spaced straight lines parallel
to one another, and the Poles are straight lines half as long as the equator.
Scale is true along latitudes 40º30'for the Eckert IV projection, and
49º16' for Eckert VI. When "EckertIV or EckertVI" are selected
in the "User-Defined Coordinate System Parameters" dialog box
you will need to enter the following parameters:
- Radius
of the Sphere
- False
Northing and False Easting
- Longitude
of the Central Meridian
NOTE:
Only a spherical form of this projection is used. The radius of the sphere
is used for forward and inverse projection from grid to geodetic coordinates
within the system wherein this projection is incorporated. You are required
to specify a geodetic datum when you use this projection as part of a
coordinate system in order to perform geodetic datum shifts into other
coordinate systems.