# What parameters are useful for an Albers equal area projection map of the world

I have a data set which contains global points. I would like to convert from long/lat to Albers equal area. However, the http://spatialreference.org proj4 world parameter values are actually for the USA.

Albers equal area might not be the best, both that is what I need to do.

Thanks!

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@whuber: The wikipedia article shows a map of the world. Perhaps he wants just that? – AndreJ May 31 '13 at 9:44
@Andre I think you're right; I'll withdraw my comment. Thanks. For the record, the Wikipedia article on the Albers projection contains an illustration of a world map (and in the caption provides the necessary parameters, although these are not the only ones possible). – whuber May 31 '13 at 9:45
That's exactly it...thanks so much! – user1544953 May 31 '13 at 11:21

According to O.S. Adams's General Theory of Equivalent Projections (1945) (p.37, of the article not the PDF):

Besides the representation of the two hemispheres just described, it is sometimes desired to represent the whole world on one map. If it is desired to have an equal-area map of this kind, it would be necessary to use a conic projection with minimum deformations between the north pole and 50º south latitude. The deformation beyond the parallel of 50º south would not be troublesome as no land of importance lies beyond that point, since only a tip of South America extends further south. The north pole should be taken as the center and the separation should be made at 170º west longitude which passes through Bering Strait and does not meet any land area. This projection corresponds to m=0.432; it does not produce any deformation along the parallel of 18º25' south; at the north pole, a singular point of the projection, 2δ amounts to 118º26'. The greatest value of 2δ besides this point is 58º43'; of a², 1.710 and of a², 2.924.

My interpretation of that (someone please correct me if I'm wrong):

• longitude of origin = 10º E
• first standard parallel = 90º N
• second standard parallel = 18º25' S
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To convert from long/lat to Albers equal area, from this Wikipedia article about the Albers projection:

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:

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