mill.rst

Miller Cylindrical

The Miller cylindrical projection is a modified Mercator projection, proposed by Osborn Maitland Miller in 1942. The latitude is scaled by a factor of $\frac{4}{5}$, projected according to Mercator, and then the result is multiplied by $\frac{5}{4}$ to retain scale along the equator.

Classification	Neither conformal nor equal area cylindrical
Available forms	Forward and inverse spherical
Defined area	Global, but best used near the equator
Alias	mill
Domain	2D
Input type	Geodetic coordinates
Output type	Projected coordinates

proj-string: +proj=mill

Usage

The Miller Cylindrical projection is used for world maps and in several atlases, including the National Atlas of the United States (USGS, 1970, p. 330-331) Snyder1987.

Example using Central meridian 90°W:

$ echo -100 35 | proj +proj=mill +lon_0=90w
-1113194.91      4061217.24

Parameters

Note

All parameters for the projection are optional.

Mathematical definition

The formulas describing the Miller projection are all taken from Snyder1987.

Forward projection

x = λ

$$y = 1.25 * \ln \left[ \tan \left(\frac{\pi}{4} + 0.4 * \phi \right) \right]$$

Inverse projection

λ = x

$$\phi = 2.5 * ( \arctan \left[ e^{0.8 * y} \right] - \frac{\pi}{4} )$$

Further reading

1. Wikipedia