Bonne Projection
The Bonne projection is a map projection that resembles the shape of a heart. Let 
be the standard
parallel, 
the central meridian, 
be the latitude,
and 
the longitude
on a unit sphere. Then
 |  |  |
(1)
|
 |  |  |
(2)
|
where
 |  |  |
(3)
|
 |  |  |
(4)
|
The illustrations above show Bonne projections for two different standard parallels.
The inverse formulas are
 |  |  |
(5)
|
 |  |  |
(6)
|
where
 |
(7)
|
The Werner projection is a special case of the Bonne projection.
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bonne projection