The HEALPix Primer
HEALPix is a Hierarchical, Equal Area, and iso-Latitude Pixelation
of the sphere designed to support efficiently
(1) local operations on the pixel set,
(2) a hierarchical tree structure for multi-resolution applications, and
(3) the global Fast Spherical Harmonic transform.
HEALPix based mathematical software meets the challenges presented by
high resolution and large volume data sets, such as
the WMAP and Planck CMB mission products.
Krzysztof M. Górski, Benjamin D. Wandelt, Eric Hivon, Frode K. Hansen,
and Anthony J. Banday
Revision: Version 3.82; July 28, 2022
https://healpix.sourceforge.io
http://healpix.sf.net
Version 3.82, 2022-07-28