Decision Support System for Map Projections of Small Scale Data

Albers Equal Area Conic

Usage:*

        The scale factor along the meridians is the reciprocal of the scale factor along the parallels in order to maintain equal area. An important characteristic of all normal conic projections is that scale is constant along any given parrallel. Like other normal conics, the Albers Equal-Area Conic projections have concentric arcs of circles for parallels and equally spaced radii as meridians. The parallels are not equally spaced, but they are fathest apart in the latitudes between the standard parallels and closer together to the north and south. The pole is not the center of the circles, but is normally an arc itself.

        If the pole is taken as one of the two standard parallels, Albers formulas reduce to a limiting form of the projection called Lambert's Equal-Area Conic. If the pole is the only standard parallel, the Albers formulas simplifies to provide the polar aspect to the Lambert Azimuthal Equal-Area. In both of these limiting cases, the pole is the point. If the Equator is the one standard parrallel, the projection becomes Lambert's Cylindrical Equal-Area, but the formulas must be modified. None of these extreme cases applies to the normal use of Albers, with standard parallels in the temperate zones, such as usage for the United States.

* Usage information source:

Snyder, John P. Map Projections - A Working Manual Paper U.S. Geological Survey Professional Paper 1395. Washington: United States Government Printing Office, 1987.

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