Albers projection

File:Usgs map albers equal area conic.PNG

An Albers projection shows areas accurately, but distorts shapes.

Albers projection of the world with standard parallels 20°N and 50°N.

The Albers equal-area conic projection, or Albers projection (named after Heinrich C. Albers), is a conic, equal area map projection that uses two standard parallels. Although scale and shape are not preserved, distortion is minimal between the standard parallels.

The Albers projection is one of the standard projections for British Columbia, and is the sole standard projection used by the government of Yukon. It is also used by the United States Geological Survey and the United States Census Bureau.

Snyder (Section 14) describes generating formulae for the projection, as well as the projection's characteristics. Coordinates from a spherical datum can be transformed into Albers equal-area conic projection coordinates with the following formulas, where λ is the longitude, λ₀ the reference longitude, φ the latitude, φ₀ the reference latitude and φ₁ and φ₂ the standard parallels:

$x = \rho \sin\theta$

$y = \rho_0 - \rho \cos\theta$

where

$n = {\tfrac12} (\sin\varphi_1+\sin\varphi_2)$

$\theta = n(\lambda - \lambda_0)$

$C = \cos^2 \varphi_1 + 2 n \sin \varphi_1$

$\rho = \frac{\sqrt{C - 2 n \sin \varphi}}{n}$

$\rho_0 = \frac{\sqrt{C - 2 n \sin \varphi_0}}{n}$

See also

• List of map projections

External links

• Mathworld's page on the Albers projection
• Table of examples and properties of all common projections, from radicalcartography.net
• Yukon Albers Projection
• An interactive Java Applet to study the metric deformations of the Albers Projection.