  PRAIA - Package for the Reduction of Astronomical Images Automatically - is a
suite of astrometric and photometric tasks designed to cope with huge amounts
of heterogeneous observations with fast processing, no human intervention,
minimum parametrization and yet maximum possible accuracy and precision. It is
the main tool used to analyse astronomical observations by an international
collaboration involving Brazilian, French and Spanish researchers under the
Lucky Star umbrella for Solar System studies. In this paper, we focus on the
astrometric concepts underneath PRAIA, used in reference system works, natural
satellite and NEA astrometry for dynamical and ephemeris studies, and lately
for the precise prediction of stellar occultations by planetary satellites,
dwarf-planets, TNOs, Centaurs and Trojan asteroids. We highlight novelties
developed by us and never reported before in the literature, which
significantly enhance astrometry precision and automation. Such as the robust
object detection and aperture characterization (BOIA), which explains the long
standing empirical photometry/astrometry axiom that recommends using apertures
with 2 - 3 sigma (Gaussian width) radius. We give examples showing the
astrometry performance, discuss the advantages of PRAIA over other astrometry
packages and comment about future planed astrometry implementations. PRAIA
codes and input files are publicly available for the first time at:
https://ov.ufrj.br/en/PRAIA/. PRAIA astrometry is useful for Solar System as
well as astrophysical observations.
