Albers Equal-Area Conic Projection

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Let phi_0 be the latitude for the origin of the Cartesian coordinates and lambda_0 its longitude, and let phi_1 and phi_2 be the standard parallels. Then for a unit sphere, the Albers equal-area conic projection maps latitude and longitude (phi,lambda) to Cartesian (x,y) coordinates

x=rhosintheta
(1)
y=rho_0-rhocostheta,
(2)

where

n=1/2(sinphi_1+sinphi_2)
(3)
theta=n(lambda-lambda_0)
(4)
C=cos^2phi_1+2nsinphi_1
(5)
rho=(sqrt(C-2nsinphi))/n
(6)
rho_0=(sqrt(C-2nsinphi_0))/n.
(7)

The projection illustrated above takes (phi_0,lambda_0)=(0 degrees,0 degrees) and standard parallels at phi_1=0 degrees and phi_2=60 degrees.

The inverse formulas are

phi=sin^(-1)((C-rho^2n^2)/(2n))
(8)
lambda=lambda_0+theta/n,
(9)

where

rho=sqrt(x^2+(rho_0-y)^2)
(10)
theta=tan^(-1)(x/(rho_0-y)).
(11)

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