Description
Bonne is an equal-area pseudoconic map projection. Its graticule takes a form of a heart, and it was frequently used to map continents.
The projection was invented by Claudius Ptolemy about A.D. 100, but it was named after Rigobert Bonne who extensively used the projection in 1752. The Bonne projection is available in ArcGIS Pro 1.0 and later and in ArcGIS Desktop 8.0 and later.
Projection properties
The subsections below describe the Bonne projection properties.
Graticule
Bonne is a pseudoconic map projection. The central meridian is projected as a straight line. The other meridians are complex curves, concave toward the central meridian and equally spaced along each parallel. The parallels of latitude are concentric circular arcs equally spaced along the central meridian. They are concave toward the pole closest to the standard parallel. The projection outline forms a shape of a heart. Both poles project as points. The graticule is symmetric across the central meridian.
Distortion
Bonne is an equal-area (equivalent) projection. Shapes, directions, angles, and distances are generally distorted. The scale is true along the central meridians and each parallel. There is no distortion along the standard parallel and central meridian, and it grows away from these lines. Distortion values are symmetric across the central meridian.
Usage
The projection was used during the nineteenth and early twentieth centuries for atlas maps of Asia, Australia, Europe, and North America. Historically, it was also used for large-scale topographic mapping of France and Ireland, along with Morocco and some other Mediterranean countries. These days, the projection is used artistically to show the world in a heart shape.
Parameters
Bonne parameters are as follows:
- False Easting
- False Northing
- Central Meridian
- Standard Parallel 1
Particular parameter cases
When the standard parallel is set to the equator, the resulting projection is sinusoidal. The Werner projection can be obtained by setting the standard parallel parameter to one of the poles.
Sources
Snyder, J. P. (1987). Map Projections: A Working Manual. U.S. Geological Survey Professional Paper 1395. Washington, DC: United States Government Printing Office.
Snyder, J. P. (1993). Flattening the Earth. Two Thousand Years of Map Projections. Chicago and London: University of Chicago Press.
Snyder, J. P. and Voxland, P. M. (1989). An Album of Map Projections. U.S. Geological Survey Professional Paper 1453. Washington, DC: United States Government Printing Office.