A method determines corrected TRP or TIS of an AUT in a near-field test chamber, the AUT having a phase center offset from a rotation center of the test chamber. The method includes performing EIRP or EIS measurements of the AUT at first sampling grid points on a first closed-surface geometric shape centered at the rotation center; mapping second sampling grid points to the first closed-surface geometric shape to provide mapped sampling grid points on the first closed-surface geometric shape, where the second sampling grid points are on a second closed-surface geometric shape centered at the phase center of the AUT; determining estimated EIRPs or EISs at the mapped sampling grid points using the EIRP or EIS measurements; scaling the estimated EIRPs or EISs at the mapped sampling grid points to provide scaled EIRPs or EISs; and calculating the corrected TRP or TIS based on the scaled EIRPs or EISs.