https://astropy-healpix.readthedocs.io/en/stable/coordinates.html
Coordinate conversions — astropy_healpix v2.0.1
Converting between pixel indices and spherical coordinates: As described in Getting started, coordinates in a HEALPix pixellization can follow either the...
coordinate conversionsastropyhealpix
https://www.fatiando.org/boule/dev/user_guide/coordinates.html
Coordinate conversions | Boule dev
coordinate conversionsbouledev
https://kvotab.se/proj.html
Swedish Coordinate Conversions — kvot ab
Convert coordinates between WGS 84, SWEREF 99 and RT 90, including bulk conversion from a pasted list.
coordinate conversionsswedishkvot