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B.J.S. Cahill's World Map Variants: 1) Conformal

- - - - - world map Cahill conformal Butterfly map

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#1
Gene Keyes

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My latest posting about Cahill's cartography discusses his Conformal, one of three main Variants he had developed subsequent to his original 1909 Butterfly.

 

http://www.genekeyes...-Conformal.html

 

Besides unpublished illustrations from his archive, it also includes my earliest start on the Cahill-Keyes map, a 1975 dummy using a 1928 Cahill Conformal. Also shown is an early draft of a Cahill-Keyes Conformal by Jacob Rus (2015), based on my sui-generis transformation.



#2
Strebe

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Your treatise uses the term “conformal” all over the place, but the only conformal map in it is the variant by Adams. Cahill himself likely did not fully understand what the term meant. Your own explanation, that meridians and parallels meet at right angles, describes a necessary but insufficient condition of conformality. The Rus variant may or may not be conformal; the image resolution is too coarse to tell what’s really going on with the graticule, and in any case, it’s the mathematics that tell the true story.

 

— daan



#3
Gene Keyes

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Your treatise uses the term “conformal” all over the place, but the only conformal map in it is the variant by Adams. Cahill himself likely did not fully understand what the term meant. Your own explanation, that meridians and parallels meet at right angles, describes a necessary but insufficient condition of conformality. The Rus variant may or may not be conformal; the image resolution is too coarse to tell what’s really going on with the graticule, and in any case, it’s the mathematics that tell the true story.

 

— daan

 

Orthodox cartographers, and Adams, gave Cahill an awful lot of grief, until Adams mellowed and offered to calculate the Variants.

 

The Rus map pdf, like mine, is viewable at 1:1 M: not coarse.  —Gene



#4
Strebe

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I contacted Rus directly. As required for conformality, he uses the Schwarz–Christoffel mapping.

 

— daan







Also tagged with one or more of these keywords: world map, Cahill, conformal, Butterfly map

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