Summary: This note is an attempt to define precisely the meaning of 'Normal Place' in the context of linear least-squares problems. Under certain conditions, it is found that the use of normal places allows an exact decomposition of the problem. Its relation to the Ring Solution and the Ring-to-Sphere Solution is briefly discussed.

Bibtex entry for this abstract:

@UNPUBLISHED{LL:LL-076,
author = {L.~Lindegren},
title={{N}ormal {P}laces in {L}east-{S}quares problems, and their relation to the {R}ing {S}olution and {R}ing-to-{S}phere {S}olution},
institution={Lund Observatory},
year={2008},
month={October},
url={http://www.rssd.esa.int/doc_fetch.php?id=2859409},
note={GAIA-C3-TN-LU-LL-076},
type={Technical note}
}