  It is highly plausible that the region of space-time far from an isolated
gravitating body is, in some sense, asymptotically Minkowskian. However
theoretical studies of the full nonlinear theory, initiated by Bondi et al.
(1962), Sachs (1962) and Newman & Unti (1962), rely on careful, clever,
a-priori choices of chart (and tetrad) and so are not readily accessible to the
numerical relativist, who chooses her/his chart on the basis of quite different
grounds. This paper seeks to close this gap. Starting from data available in a
typical numerical evolution, we construct a chart and tetrad which is,
asymptotically, sufficiently close to the theoretical ones, so that the key
concepts of Bondi news function, Bondi mass and its rate of decrease can be
estimated. In particular these esimates can be expressed in the numerical
relativist's chart as numerical relativity recipes.
