Geocart Projections

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GS50

Classification

Geocart menu class: Miscellaneous
Conformal

Graticule

Meridians: Complex curves at slightly varying intervals
Parallels: Complex curves at slightly varying intervals
Poles: Points beyond the useful range of the map
Symmetry: None

Scale

True along an irregular line approximately encompassing the regions of the 50 States of the United States
Varies less than 2 percent from true scale throughout the 50 States and adjacent bodies of water

Distortion

Shape and scale distortion very low for 50-State region. Greater distortion for regions away from 50 States.

Special features

Portrays irregular region of 50 States at about one-fourth the variation in scale of the best standard projections. Uses tenth-order complex-algebra polynomials to modify the Stereographic projection and is practical only with a computer. Conformality is precise in these cases even though finite polynomial series are used. The coefficients are useful only for this design of a 50-State map.

Origin

Developed by John P. Snyder (1926–) of the U.S. Geological Survey in 1982

Similar projections

Oblated (or Prolated) Stereographic projections by O.M. Miller in 1953 and by L.P. Lee in 1974 are equivalent to third-order complex-algebra polynomial modifications of the oblique Stereographic, applied to continents or the Pacific Ocean.
New Zealand Map Grid presented by W.I. Reilly in 1973 is a sixth-order complex-algebra polynomial modification of the Mercator, applied to New Zealand.
Modified-Stereographic Conformal projection developed by Snyder in 1983 is a sixth-order complex-algebra modification of the oblique Stereographic, applied to Alaska.

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.