Geocart Projections

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two-point equidistant

doubly equidistant

Parameters: Anchor point 1, Anchor point 2

Classifications

Geocart menu class: Azimuthal
Modified azimuthal
Neither conformal nor equal area

Graticule

Meridians: Complex curves
Parallels: Complex curves
Poles: Normally points
Symmetry: Normally none

Scale

True along a straight line from either of two central points

Distortion

No points free of distortion

Usage

Map of Asia by the National Ceographic Society
Could be used to determine the distance from a ship at sea at a known location from the start and end of a voyage

Origin

Presented by Hans Maurer (1868-1945) of Cermany in 1919 and Charles F. Close (1865-1952) of England independently in 1921

Aspects

Typically oblique

Other names

Doubly Equidistant

Limiting forms

If the two central points are identical, the Azimuthal Equidistant projection results.

Similar projections

Azimuthal Equidistant, on which distance is correct from only one point
Donald Elliptical, developed by Jay K. Donald of the American Telephone and Telegraph Company in 1956. Used by telephone companies to establish long-distance rates, the Donald is a Two-Point Equidistant projection specially modified for the ellipsoid and confined to the United States and southern Canada.
Chamberlin Trimetric, an approximate three-point equidistant projection
Two-Point Azimuthal-Equidistant, presented by Charles F. Close in 1922, has true azimuths from one point and true distances from a second point to all other points.

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.