The PAL library is a partial re-implementation of Pat Wallace's popular SLALIB
library written in C using a Gnu GPL license and layered on top of the IAU's
SOFA library (or the BSD-licensed ERFA) where appropriate.
PAL attempts to stick to the SLA C API where
possible although palObs() has a more C-like API than the equivalent
slaObs() function. In most cases it is enough to simply change the function
prefix of a routine in order to link against PAL rather than SLALIB. Routines
calling SOFA use modern nutation and precession models so will return slightly
different answers than native SLALIB. PAL functions not available in SOFA were
ported from the Fortran version of SLALIB that ships as part of the Starlink
software and uses a GPL licence.
See pal.news for release notes.
A simple configure script is provided:
./configure --prefix=/usr/local --without-starlink
make
make install
The tests can be run using make check. Use --prefix to specify an install location.
Given the history of the source code as a Starlink library the default will be /star.
--without-starlink forces the configure script to forget about any Starlink
configurations. This is the safe option if you run into problems when using
a simple --prefix for building outside of Starlink. The configure script
will assume Starlink is not being used by looking to see if
STARCONF_DEFAULT_PREFIX environment variable is set. You may run into problems if
STARCONF_DEFAULT_PREFIX is set but you use --without-starlink.
Requires that either the SOFA C library or the ERFA library variant
(which has a more permissive license than SOFA) be installed. The
configure script will abort if neither SOFA nor ERFA can be
found. SOFA can be obtained either from http://www.iausofa.org or
from an unofficial github repository (with a configure script) at
https://github.com/Starlink/sofa/downloads. ERFA can be downloaded
from https://github.com/liberfa/erfa.
Not all SLALIB functions have been added. New routines are added to PAL as demand arises.
A Perl binding of PAL is available (https://github.com/timj/perl-Astro-PAL) named Astro::PAL
and is available from CPAN at https://metacpan.org/module/Astro::PAL. This is a standalone
distribution that comes with its own copies of PAL and SOFA and so can be installed directly
from the cpan shell.
A Python binding of PAL is available (https://github.com/Starlink/palpy). This is a standalone distribution that comes with its own copies of PAL and SOFA.
The Starlink AST (http://www.starlink.ac.uk/ast) library now uses PAL and can be built either with a private PAL or with an external PAL.
The description paper for PAL is: "PAL: A Positional Astronomy Library", Jenness, T. & Berry, D. S., in Astronomical Data Anaysis Software and Systems XXII, Friedel, D. N. (ed), ASP Conf. Ser. 475, p307.