HEALPix (sometimes written as Healpix), an acronym for Hierarchical Equal Area isoLatitude Pixelisation of a 2-sphere, can refer to either an algorithm for pixelisation of the 2-sphere, an associated software package,HEALPix software site at SourceForge or an associated class of map projections.Mapping on the HEALPix grid, Calabretta, Roukema, 2007