[Proj] Robinson projection

[Bernhard Jenny]

I think I found an inconsistency in the PROJ.4 implementation of the Robinson projection. Robinson specifies the vertical distribution and length of parallels in his 1974 text for every 5 degrees of increasing latitude.  PROJ.4 places the 40 degree latitude at 0.4968, whereas Robinson places it at 0.4958. This corresponds to a vertical shift of about 9 km at 40 degrees north and south. Is this a simple mistyping, or are there any reasons to change Robinson's definition?

Reference:
Robinson, A. (1974). A New Map Projection: Its Development and Characteristics. International Yearbook of Cartography, p. 145-155.

Thanks,
Bernie
 
Bernhard Jenny
Institute of Cartography and Geoinformation ETH Zurich
jenny at karto.baug.ethz.ch
http://jenny.cartography.ch