Bipolar oblique conformal conic
Description
This projection was developed specifically for mapping North and South America. It maintains conformality. It is based on the Lambert conformal conic, using two oblique conic projections side by side.
Projection method
Two oblique cones are joined with the poles 104° apart. A great circle arc 104° long begins at 20° S and 110° W, cuts through Central America, and terminates at 45° N and approximately 19°59'36" W. The scale of the map is then increased by approximately 3.5 percent. The origin of the coordinates is 17°15' N, 73°02' W (Snyder 1993).
Lines of contact
The two oblique cones are each conceptually secant. These standard lines do not follow any single parallel or meridian.
Linear graticules
Only from each transformed pole to the nearest actual pole
Properties
Shape
Conformality is maintained except for a slight discrepancy at the juncture of the two conic projections.
Area
Minimal distortion near the standard lines, increasing with distance
Direction
Local directions are accurate because of conformality.
Distance
True along standard lines.
Limitations
The bipolar oblique conformal conic projection will display North America and South America only. If having problems, check all feature types (particularly annotation and tics) and remove any features that are beyond the range of the projection.
Uses and applications
- Developed in 1941 by the American Geographical Society as a low-error single map of North and South America
- Conformal mapping of North and South America as a contiguous unit
- Used by USGS for geologic mapping of North America until it was replaced in 1979 by the transverse Mercator projection
Parameters
Supported in ArcInfo Workstation only. Projection-specific parameters are set by the software.