Geocart Projections

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bipolar oblique conic conformal

Classifications

Geocart menu class: Conic
Conic
Conformal

Graticule

Meridians: Unequally spaced curved lines, except for two straight meridians from the transformed poles to the nearest geographic pole
Parallels: Unequally spaced curved lines
Poles: Points
Symmetry: None

Scale

True along four circular arcs joined to form two S curves. These arcs do not follow any parallel or meridian. Scale is constant along circular arcs centered on each transformed pole for part of the map. The pole for most of North America is in the North Atlantic, and that for South America is in the South Pacific.

Distortion

Low throughout North and South America. None along the lines of true scale and constant along circular arcs centered on the transformed pole for the given part of the map. Slight nonconformality near the line joining the two transformed poles.

Usage

Designed specifically for a low-error map of North and South America constructed by the American Geographical Society. Other organizations, including the U.S. Geological Survey, have used the American Geographical Society map as a base for maps of North or South America alone, but, since the advent of computer plotting, other projections are preferable and practical for regional maps.

Origin

Presented by Osborn Maitland Miller (1897–1979) and William A. Briesemeister of the American Geographical Society in 1941

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.