Logarithmic ambiguities in the description of spatial infinity

Logarithmic ambiguities in the choice of asymptotically Cartesian coordinates at spatial infinity are discussed. It is shown that they do not affect the definitions of energy-momentum and angular momentum at i°. Thus, from a physical viewpoint, the ambiguities are "pure gauge." A prescription is given for fixed this gauge freedom for the class of space-times in which the leading-order part of the Weyl tensor satisfies a certain reflection symmetry. This class admits, in all (relatively boosted) rest frames at infinity, a one-parameter family of asymptotically distinct 3-surfaces (generalized 3-planes) on which the trace of the extrinsic curvature falls off faster than usual.