Geocart Projections

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Lambert equal-area conic

Parameters: Latitude of origin, Standard parallel 1

Classifications

Geocart menu class: Conic
Conic
Equal area

Graticule

Meridians: Equally spaced straight lines converging at a common point, which is one of the poles. The angles between them are less than the true angles.
Parallels: Unequally spaced concentric circular arcs centered on the pole of convergence of the meridians. The meridians are therefore radii of the circular arcs. Spacing of parallels decreases away from the pole of convergence.
Poles: One pole is a point; the other pole is a circular arc enclosing the same angle as that enclosed by the other parallels of latitude for a given range of longitudes. Symmetry: About any meridian

Scale

True along the chosen standard parallel
Scale is constant along any given parallel. The scale factor at any given point along the meridian is the reciprocal of that along the parallel, to preserve area.

Distortion

Free of scale and angular distortion only along the standard parallel. Severe stretching near each pole. Scale distortion and angular distortion are constant along any given parallel.

Origin

Presented by Johann Heinrich Lambert (1728 – 1777) of Alsace in 1772

Limiting form

Polar Lambert Azimuthal Equal-Area projection, if the central pole is the standard parallel. The cone of projection thereby becomes a plane.

Similar projections

Albers Equal-Area Conic projection also has concentric circular arcs for parallels and straight meridians, but it has two standard parallels close to the latitudes of interest. If just one of its standard parallels is made a pole, it becomes the Lambert Equal-Area Conic projection, but that pole is not free of distortion, as the usual standard parallel is.

Description adapted from J.P. Snyder and P.M. Voxland, An Album of Map Projections, U.S. Geological Survey Professional Paper 1453. United States Government Printing Office: 1989.