Bipolar Oblique Conformal Conic

images\sc_projections_bipobliqueconf.gif

 

A conformal projection that consists of two oblique conic projections, side-by-side, but with poles 104 degrees apart.

 

Scale

 

Scale is true along two standard transformed parallels on each conic projection. Neither of these lines follows any geographical meridian or parallel.

 

Distortion

 

Very small deviation from conformality, where the two conic projections join. However, potentially very large distortion outside the intended region. When creating graticules for use with this distortion the graticule must be trimmed by selecting portions of the graticule and deleting those portions that otherwise are projected in unpleasant ways. Note how the graticule shown in the illustration above has been trimmed.

 

Usage

 

Used only in spherical form for maps of the Americas. Used by the AGS for maps of North and South America, by USGS for the North American portion of the Geologic Map of 1965, the Basement Map of 1967 and the USGS Geothermal Map and Metallogenic Map.

 

Limitations

 

Use only for maps of the Americas.

 

Origin

 

Developed by O.M. Miller and William A. Briesemeister and presented in 1941 and designed specifically for a map of North and South American constructed in several sheets by the American Geographical Society (AGS).