Donald Projection

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An azimuthal, two-point equidistant projection specially modified for the Earth ellipsoid and confined to the United States and southern Canada. Shows true distances, but not true azimuths, from either of two chosen points to any other point on the map.

 

Scale

 

True along a straight line from either of the two central points that define the projection. Distances are exact when measured from either one of two central points, at: 37 degrees 42minutes 14.69 seconds North (37.7040806) latitude, 82 degrees 39minutes 15.27seconds West (-82.6542417) longitude in Floyd County, Kentucky and at 41 degrees 02 minutes 55.53 seconds North (41.0487583) latitude, 112 degrees 03 minutes 39.35 seconds West (-112.0609306) longitude in Webster County, Utah.

 

Distortion

 

No points free of distortion. Minimizes distance distortion in the lower 48 US states.

 

Usage

 

Used by telephone companies to establish long-distance rates in the United States and southern Canada.

 

Limitations

 

Use only for the lower 48 United States and Southern Canada

 

Origin

 

Developed by Jay K. Donald of the American Telephone and Telegraph Company in 1956. Two-point equidistant projections were originally presented by Hans Maurer (1868-1945) of Germany in 1919 and by Charles F. Close (1865-1952) independently in 1921.