https://astropy-healpix.readthedocs.io/en/latest/api/astropy_healpix.healpy.nside2pixarea.html
nside2pixarea — astropy_healpix v2.0.1
astropyhealpix
https://zonca.github.io/2013/08/healpix-map-of-earth-using-healpy.html
HEALPix map of the Earth using healpy | Andrea Zonca's blog
of thehealpixmapearthusing