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"Practical and Emblematic Roles of the American Polyconic Projection"

Weiner Schriften zur Geographie und Kartographie [Institut für Geographie und Regionalforschung der Universität Wien], Band 16 [Festschrift for Ingrid Kretschmer], 2004, pp. 93-99.

SUMMARY. The polyconic projection was an emblem of nineteenth-century American federal cartography. Neither conformal nor equivalent,it minimizes distance distortion on large-scale sheet maps with a local central meridian. The Coast Survey, which published projection tables and a mathematical description in its 1853 annual report, adopted the polyconic projection for its nautical charts as well as for “smooth sheet” plots of raw survey data. The Survey began converting its nautical charts to a more suitable Mercator framework in 1910 but retained the polyconic projection for smooth sheets until digital technology obviated these plots in the 1990s. The U.S. Geological Survey, which adopted the projection in the early 1880s, incorrectly claimed a polyconic framework for its topographic quadrangle maps decades after switching to conformal projections around 1950. The polyconic projection's longevity reflects bureaucratic inertia as well as any map projection's potential significance as a graphic signature. As several small-scale world maps also demonstrate, a projection acquires emblematic value when an organization selects a single cartographic perspective from several plausible yet sub-optimal solutions.

Vienna, MD-VA, 7.5-minute quadrangle map, 1973, incorrectly reports its framework as a polyconic projection.
A four-cone diagram used to explain the principle of polyconic projection. From Deitz and Adams, Elements of Map Projection (1945).
A whole-world polyconic framework centered on the Greenwich Meridian, from Deitz and Adams, Elements of Map Projection (1945).