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 used by some big countries as "official standard projection" for Census and other applications.
| Brazil | federal government, through IBGE, for Census Statistical Grid [1] | |
| Canada | government of British Columbia[2] | |
| Canada | government of the Yukon[3] (sole governmental projection) | |
| US | United States Geological Survey[4] | |
| US |
Some "official products" also adopted Albers projection, for example most of the maps in the National Atlas of the United States.
Snyder[5] 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
{R}
λ
λ0
\varphi
\varphi0
\varphi1
\varphi2
\begin{align}x&=\rho\sin\theta\ y&=\rho0-\rho\cos\theta\end{align}
where
\begin{align}n&=\tfrac12\left(\sin\varphi1+\sin\varphi2\right)\\ \theta&=n\left(λ-λ0\right)\\ C&=\cos2\varphi1+2n\sin\varphi1\\ \rho&=\tfrac{R}{n}\sqrt{C-2n\sin\varphi}\\ \rho0&=\tfrac{R}{n}\sqrt{C-2n\sin\varphi0}\end{align}
If just one of the two standard parallels of the Albers projection is placed on a pole, the result is the Lambert equal-area conic projection.[6]