[Proj] adding the HEALPix projection to Proj4

[Alex Raichev]

Hi all:

I just joined this list. My name is Alex Raichev, and i'm working with
Robert Gibb and Michael Speth of Landcare Research New Zealand on a
GIS project. As part of this project, we would like to add the HEALPix
projection (http://en.wikipedia.org/wiki/Healpix) to Proj4.

Our plan is to implement in Proj4 the spherical HEALPix projection
from the formulas published in

Mark R. Calabretta and Boudewijn F. Roukema, Mapping on the healpix
grid, Monthly Notices of the Royal Astronomical Society 381 (2007),
no. 2, 865–872.

and an ellipsoidal HEALPix projection that is simply the composition
of 1) the standard area preserving projection from an oblate spheroid
to a sphere and 2) the spherical HEALPix projection.

If any of you are working on this already or have any suggestions,
please let me know.

Thanks.
Alex